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• 101.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Observation of H -> b(b)over-bar decays and V H production with the ATLAS detector2018In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 786, p. 59-86Article in journal (Refereed)

A search for the decay of the Standard Model Higgs boson into a b (b) over bar pair when produced in association with a W or Z boson is performed with the ATLAS detector. The data, corresponding to an integrated luminosity of 79.8 fb(-1) were collected in proton-proton collisions during Run 2 of the Large Hadron Collider at a centre-of-mass energy of 13 TeV. For a Higgs boson mass of 125 GeV, an excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.9 (4.3) standard deviations. A combination with the results from other searches in Run 1 and in Run 2 for the Higgs boson in the bb decay mode is performed, which yields an observed (expected) significance of 5.4 (5.5) standard deviations, thus providing direct observation of the Higgs boson decay into b-quarks. The ratio of the measured event yield for a Higgs boson decaying into b (b) over bar to the Standard Model expectation is 1.01 +/- 0.12(stat.) (-0.15) (+0.16)(syst.). Additionally, a combination of Run 2 results searching for the Higgs boson produced in association with a vector boson yields an observed (expected) significance of 5.3 (4.8) standard deviations.

• 102.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Measurement of the nuclear modification factor for inclusive jets in Pb plus Pb collisions at root s(NN)=5.02 TeV with the ATLAS detector2019In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 790, p. 108-128Article in journal (Refereed)

Measurements of the yield and nuclear modification factor, R-AA, for inclusive jet production are performed using 0.49 nb(-1) of Pb+Pb data at root s(NN) = 5.02 TeV and 25 pb(-1) of Pb+Pb data at root s = 5.02 TeV with the ATLAS detector at the LHC. Jets are reconstructed with the anti-k(t) algorithm with radius parameter R = 0.4 and are measured over the transverse momentum range of 40-1000 GeV in six rapidity intervals covering vertical bar y vertical bar < 2.8. The magnitude of R-AA increases with increasing jet transverse momentum, reaching a value of approximately 0.6 at 1 TeV in the most central collisions. The magnitude of R-AA also increases towards peripheral collisions. The value of R-AA is independent of rapidity at low jet transverse momenta, but it is observed to decrease with increasing rapidity at high transverse momenta.

• 103.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Search for Higgs boson decays into a pair of light bosons in the bb mu mu final state in pp collision at root s=13 TeV with the ATLAS detector2019In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 790, p. 1-21Article in journal (Refereed)

A search for decays of the Higgs boson into a pair of new spin-zero particles, H -> aa, where the a-bosons decay into a b-quark pair and a muon pair, is presented. The search uses 36.1 fb(-1) of proton-proton collision data at root s = 13 TeV recorded by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the Standard Model prediction is observed. Upper limits at 95% confidence level are placed on the branching ratio (sigma(H)/sigma(SM)) x B(H -> aa -> bb mu mu), ranging from 1.2 x 10(-4) to 8.4 x 10(-4) in the a-boson mass range of 20-60 GeV. Model-independent limits are set on the visible production cross-section times the branching ratio to the bb mu mu final state for new physics, sigma(vis)(X) x B(X -> bb mu mu), ranging from 0.1 fb to 0.73 fb for m(mu mu) between 18 and 62 GeV.

• 104.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Study of the hard double-parton scattering contribution to inclusive four-lepton production in pp collisions at root s=8 TeV with the ATLAS detector2019In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 790, p. 595-614Article in journal (Refereed)

The inclusive production of four isolated charged leptons in pp collisions is analysed for the presence of hard double-parton scattering, using 20.2 fb(-1) of data recorded in the ATLAS detector at the LHC at centre-of-mass energy root s = 8 TeV. In the four-lepton invariant-mass range of 80 < m(4l) < 1000 GeV, an artificial neural network is used to enhance the separation between single- and double-parton scattering based on the kinematics of the four leptons in the final state. An upper limit on the fraction of events originating from double-parton scattering is determined at 95% confidence level to be f(DPS) = 0.042, which results in an estimated lower limit on the effective cross section at 95% confidence level of 1.0 mb.

• 105. Bi, Huan-Yu
Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
Degeneracy relations in QCD and the equivalence of two systematic all-orders methods for setting the renormalization scale2015In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 748, p. 13-18Article in journal (Refereed)

The Principle of Maximum Conformality (PMC) eliminates QCD renormalization scale-setting uncertainties using fundamental renormalization group methods. The resulting scale-fixed pQCD predictions are independent of the choice of renormalization scheme and show rapid convergence. The coefficients of the scale-fixed couplings are identical to the corresponding conformal series with zero beta-function. Two all-orders methods for systematically implementing the PMC-scale setting procedure for existing high order calculations are discussed in this article. One implementation is based on the PMC-BLM correspondence (PMC-I); the other, more recent, method (PMC-II) uses the R-delta-scheme, a systematic generalization of the minimal subtraction renormalization scheme. Both approaches satisfy all of the principles of the renormalization group and lead to scale-fixed and scheme-independent predictions at each finite order. In this work, we show that PMC-I and PMC-II scale-setting methods are in practice equivalent to each other. We illustrate this equivalence for the four-loop calculations of the annihilation ratio Re+e- and the Higgs partial width Gamma(H -> b (b) over bar). Both methods lead to the same resummed ('conformal') series up to all orders. The small scale differences between the two approaches are reduced as additional renormalization group {beta(i)}-terms in the pQCD expansion are taken into account. We also show that special degeneracy relations, which underly the equivalence of the two PMC approaches and the resulting conformal features of the pQCD series, are in fact general properties of non-Abelian gauge theory.

• 106. Bomark, N.-E.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Photon, neutrino and charged particle spectra from R-violating gravitino decays2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 686, no 03-feb, p. 152-161Article in journal (Refereed)

We study photonic. neutrino and charged particle signatures from slow decays of gravitino dark matter in supersymmetric theories where R-parity is explicitly broken by trilinear operators Photons and (anti-)fermions from loop and tree-level processes give rise to spectra with distinct features, which. if observed, can give crucial input on the possible mass of the gravitino and the magnitude and flavour structure of R-violating operators. Within this framework, we make detailed comparisons of the theoretical predictions to the recent experimental data from PAMELA, ATIC and Fermi LAT.

• 107.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Institut de Física Corpuscular (CSIC–Universitat de València), Spain.
Constraining the invisible neutrino decay with KM3NeT-ORCA2019In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 789, p. 472-479Article in journal (Refereed)

Several theories of particle physics beyond the Standard Model consider that neutrinos can decay. In this work we assume that the standard mechanism of neutrino oscillations is altered by the decay of the heaviest neutrino mass state into a sterile neutrino and, depending on the model, a scalar or a Majoron. We study the sensitivity of the forthcoming KM3NeT-ORCA experiment to this scenario and find that it could improve the current bounds coming from oscillation experiments, where three-neutrino oscillations have been considered, by roughly two orders of magnitude. We also study how the presence of this neutrino decay can affect the determination of the atmospheric oscillation parameters sin(2) theta(23) and Delta m(31)(2), as well as the sensitivity to the neutrino mass ordering.

• 108. Ema, Yohei
Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
Higgs-inflaton mixing and vacuum stability2019In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 789, p. 373-377Article in journal (Refereed)

The quartic and trilinear Higgs field couplings to an additional real scalar are renormalizable, gauge and Lorentz invariant. Thus, on general grounds, one expects such couplings between the Higgs and an inflaton in quantum field theory. We find that the often omitted trilinear interaction is only weakly constrained by cosmology and could stabilize the electroweak vacuum by increasing the Higgs self coupling. The consequent Higgs-inflaton mixing can be as large as order one making a direct inflaton search possible at the LHC.

• 109.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
On the use of black hole binaries as probes of local dark energy properties2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 683, no 1, p. 7-10Article in journal (Refereed)

Accretion of dark energy onto black holes will take place when dark energy is not a cosmological constant. It has been proposed that the time evolution of the mass of the black holes in binary systems due to dark energy accretion could be detectable by gravitational radiation. This would make it possible to use observations of black hole binaries to measure local dark energy properties, e.g., to determine the sign of 1+w where w is the dark energy equation of state. In this Letter we show that such measurements are unfeasible due to the low accretion rates.

• 110. Freese, Katherine
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Dark matter collisions with the human body2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 717, no 1-3, p. 25-28Article in journal (Refereed)

We investigate the interactions of Weakly Interacting Massive Particles (WIMPs) with nuclei in the human body. We are motivated by the fact that WIMPS are excellent candidates for the dark matter in the Universe. Our estimates use a 70 kg human and a variety of WIMP masses and cross-sections. The contributions from individual elements in the body are presented and it is found that the dominant contribution is from scattering off of oxygen (hydrogen) nuclei for the spin-independent (spin-dependent) interactions. For the case of 60 GeV WIMPs, we find that, of the billions of WIMPs passing through a human body per second, roughly similar to 10 WIMPs hit one of the nuclei in the human body in an average year, if the scattering is at the maximum consistent with current bounds on WIMP interactions. We also study the 10-20 GeV WIMPs with much larger cross-sections that best fit the DAMA, COGENT, and CRESST data sets and find much higher rates: in this case as many as 10(5) WIMPs hit a nucleus in the human body in an average year, corresponding to almost one a minute. Though WIMP interactions are a source of radiation in the body, the annual exposure is negligible compared to that from other natural sources (including radon and cosmic rays), and the WIMP collisions are harmless to humans.

• 111.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, USA.
A novel approach to quantifying the sensitivity of current and future cosmological datasets to the neutrino mass ordering through Bayesian hierarchical modeling2017In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 775, p. 239-250Article in journal (Refereed)

We present a novel approach to derive constraints on neutrino masses, as well as on other cosmological parameters, from cosmological data, while taking into account our ignorance of the neutrino mass ordering. We derive constraints from a combination of current as well as future cosmological datasets on the total neutrino mass M-nu and on the mass fractions f(nu),i = m(i)/M-nu (where the index i = 1, 2, 3 indicates the three mass eigenstates) carried by each of the mass eigenstates m(i), after marginalizing over the (unknown) neutrino mass ordering, either normal ordering (NH) or inverted ordering (IH). The bounds on all the cosmological parameters, including those on the total neutrino mass, take therefore into account the uncertainty related to our ignorance of the mass hierarchy that is actually realized in nature. This novel approach is carried out in the framework of Bayesian analysis of a typical hierarchical problem, where the distribution of the parameters of the model depends on further parameters, the hyperparameters. In this context, the choice of the neutrino mass ordering is modeled via the discrete hyperparameter h(type), which we introduce in the usual Markov chain analysis. The preference from cosmological data for either the NH or the IH scenarios is then simply encoded in the posterior distribution of the hyper-parameter itself. Current cosmic microwave background (CMB) measurements assign equal odds to the two hierarchies, and are thus unable to distinguish between them. However, after the addition of baryon acoustic oscillation (BAO) measurements, a weak preference for the normal hierarchical scenario appears, with odds of 4 : 3 from Planck temperature and large-scale polarization in combination with BAO (3 : 2 if small-scale polarization is also included). Concerning next-generation cosmological experiments, forecasts suggest that the combination of upcoming CMB (COrE) and BAO surveys (DESI) may determine the neutrino mass hierarchy at a high statistical significance if the mass is very close to the minimal value allowed by oscillation experiments, as for NH and a fiducial value of M-nu = 0.06 eV there is a 9 : 1 preference of normal versus inverted hierarchy. On the contrary, if the sum of the masses is of the order of 0.1 eV or larger, even future cosmological observations will be inconclusive. The innovative statistical strategy exploited here represents a very simple, efficient and robust tool to study the sensitivity of present and future cosmological data to the neutrino mass hierarchy, and a sound competitor to the standard Bayesian model comparison. The unbiased limit on M-nu we obtain is crucial for ongoing and planned neutrinoless double beta decay searches.

• 112.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Chinese Academy of Sciences, China.
Effective field theories on solitons of generic shapes2015In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 747, p. 173-177Article in journal (Refereed)

A class of effective field theories for moduli or collective coordinates on solitons of generic shapes is constructed. As an illustration, we consider effective field theories living on solitons in the O(4) non-linear sigma model with higher-derivative terms.

• 113.
Kernforschungszentrum, Universität Karlsruche.
Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Institute for Physics, University of Basle. Institute for Physics, University of Basle. Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory. Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory. Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory. Centre de recherches nucléaries and Université Louis Pasteur, Strabourg. Dept. of Nuclear Physics, Univerity of Tessaloniki.
Strong interaction effects in antiprotonic 6Li/7Li atoms1984In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 137, no 56, p. 323-328Article in journal (Refereed)

The effects of strong interaction on the 3 –> 2 X-ray transition in antiprotonic 6Li/7Li atoms have been measured at the low energy -beam at CERN. For the shifts and widths of the levels the values [epsilon]2p = (-230 ï¿œ 72) eV, [Gamma]2p = (443 ï¿œ 210) eV, and [Gamma]3d = (0.130 ï¿œ 0.045) eV for 6Li, and [epsilon]2p = (-336 ï¿œ 60) eV, [Gamma]2p = (456 ï¿œ 190) eV, and [Gamma]3d = (0.210 ï¿œ 0.062) eV for 7Li were found. The data are compared with optical model predictions.

• 114.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Proof of consistency of nonlinear massive gravity in the Stuckelberg formulation2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 715, no 4-5, p. 335-339Article in journal (Refereed)

We address some recent concerns about the absence of the Boulware-Deser ghost in the Stuckelberg formulation of nonlinear massive gravity. First we provide general arguments for why any ghost analysis in the Stuckelberg formulation has to agree with existing consistency proofs that have been carried out without using Stuckelberg fields. We then demonstrate the absence of the ghost at the completely nonlinear level in the Stuckelberg formulation of the minimal massive gravity action. The constraint that removes the ghost field and the associated secondary constraint that eliminates its conjugate momentum are computed explicitly, confirming the consistency of the theory in the Stuckelberg formulation.

• 115.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Exact solution to the "auxiliary extra-dimension" model of massive gravity2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 702, no 1, p. 90-93Article in journal (Refereed)

The auxiliary extra-dimension model was proposed in order to provide a geometrical interpretation to modifications of general relativity, in particular to non-linear massive gravity. In this context, the theory was shown to be ghost free to third order in perturbations, in the decoupling limit. In this work, we exactly solve the equation of motion in the extra dimension, to obtain a purely 4-dimensional theory. Using this solution, it is shown that the ghost appears at the fourth order and beyond. We explore potential modifications to address the ghost issue and find that their consistent implementation requires going beyond the present framework.

• 116.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
On partially massless bimetric gravity2013In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 726, no 4-5, p. 834-838Article in journal (Refereed)

We extend the notion of the Higuchi bound and partial masslessness to ghost-free nonlinear bimetric theories. This can be achieved in a simple way by first considering linear massive spin-2 perturbations around maximally symmetric background solutions, for which the linear gauge symmetry at the Higuchi bound is easily identified. Then, requiring consistency between an appropriate subset of these transformations and the dynamical nature of the backgrounds, fixes all but one parameter in the bimetric interaction potential. This specifies the theory up to the value of the Fierz-Pauli mass and leads to the unique candidate for nonlinear partially massless bimetric theory.

• 117.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
A possibility to solve the problems with quantizing gravity2013In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 725, no 4-5, p. 473-476Article in journal (Refereed)

It is generally believed that quantum gravity is necessary to resolve the known tensions between general relativity and the quantum field theories of the standard model. Since perturbatively quantized gravity is non-renormalizable, the problem how to unify all interactions in a common framework has been open since the 1930s. Here, I propose a possibility to circumvent the known problems with quantizing gravity, as well as the known problems with leaving it unquantized: By changing the prescription for second quantization, a perturbative quantization of gravity is sufficient as an effective theory because matter becomes classical before the perturbative expansion breaks down. This is achieved by considering the vanishing commutator between a field and its conjugated momentum as a symmetry that is broken at low temperatures, and by this generates the quantum phase that we currently live in, while at high temperatures Planck's constant goes to zero.

• 118.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
A relativistic acoustic metric for planar black holes2016In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 752, p. 13-17Article in journal (Refereed)

We demonstrate here that the metric of a planar black hole in asymptotic anti-de Sitter space can, on a slice of dimension 3 + 1, be reproduced as a relativistic acoustic metric. This completes an earlier calculation in which the non-relativistic limit was used, and also serves to obtain a concrete form of the Lagrangian.

• 119. Jiménez, Jose Beltrán
Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
Spacetimes with vector distortion: Inflation from generalised Weyl geometry2016In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 756, p. 400-404Article in journal (Refereed)

Spacetime with general linear vector distortion is introduced. Thus, the torsion and the nonmetricity of the affine connection are assumed to be proportional to a vector field (and not its derivatives). The resulting two-parameter family of non-Riemannian geometries generalises the conformal Weyl geometry and some other interesting special cases. Taking into account the leading nonlinear correction to the Einstein-Hilbert action results uniquely in the one-parameter extension of the Starobinsky inflation known as the alpha-attractor. The most general quadratic curvature action introduces, in addition to the canonical vector kinetic term, novel ghost-free vector-tensor interactions.

• 120. Lowe, David A.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Iceland, Iceland.
Black hole complementarity: The inside view2014In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 737, p. 320-324Article in journal (Refereed)

Within the framework of black hole complementarity, a proposal is made for an approximate interior effective field theory description. For generic correlators of local operators on generic black hole states, it agrees with the exact exterior description in a region of overlapping validity, up to corrections that are too small to be measured by typical infalling observers.

• 121.
Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
Università di Ferrara and INFN, 44100 Ferrara, Italy. St. Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Università di Ferrara and INFN, 44100 Ferrara, Italy. Università di Ferrara and INFN, 44100 Ferrara, Italy. High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia. Università di Ferrara and INFN, 44100 Ferrara, Italy. INFN, Sezione di Ferrara, 44100 Ferrara, Italy. Università di Ferrara and INFN, 44100 Ferrara, Italy. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Physikalisches Institut II, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Jülich Center for Hadron Physics, 52425 Jülich, Germany. High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Universität Münster, 48149 Münster, Germany. St. Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Universität Münster, 48149 Münster, Germany. Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, 141980 Dubna, Russia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Università di Ferrara and INFN, 44100 Ferrara, Italy. High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, 141980 Dubna, Russia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, 141980 Dubna, Russia. Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, 141980 Dubna, Russia. Physics Department, Indiana University, Bloomington, IN 47405, USA. Institut für Kernphysik, Universität Münster, 48149 Münster, Germany. St. Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia. St. Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia. Physikalisches Institut II, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Universität Münster, 48149 Münster, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, 141980 Dubna, Russia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Physics Department, Indiana University, Bloomington, IN 47405, USA. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. INFN, Sezione di Ferrara, 44100 Ferrara, Italy. Università di Ferrara and INFN, 44100 Ferrara, Italy. Università di Ferrara and INFN, 44100 Ferrara, Italy. Physikalisches Institut II, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Zentralabteilung Technologie, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia. INFN, Sezione di Bari, 70126 Bari, Italy. Stockholm University, Faculty of Science, Department of Physics. Institut für Kern- und Hadronenphysik, Forschungszentrum Rossendorf, 01314 Dresden, Germany. St. Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Zentralinstitut für Elektronik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Department of Nuclear Reactions, Andrzej Soltan, Institute for Nuclear Studies, 00-681 Warsaw, Poland.
Polarizing a stored proton beam by spin flip?2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 674, no 4-5, p. 269-275Article in journal (Refereed)

We discuss polarizing a proton beam in a storage ring, either by selective removal or by spin flip of the stored ions. Prompted by recent, conflicting calculations, we have carried out a measurement of the spin-flip cross section in low-energy electron–proton scattering. The experiment uses the cooling electron beam at COSY as an electron target. The measured cross sections are too small for making spin flip a viable tool in polarizing a stored beam. This invalidates a recent proposal to use co-moving polarized positrons to polarize a stored antiproton beam.

• 122.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Yangzhou University, China; Shanghai Jiao Tong University, China.
GUP-corrected black hole thermodynamics and the maximum force conjecture2018In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 785, p. 217-220Article in journal (Refereed)

We show that thermodynamics for an asymptotically flat Schwarzschild black hole leads to a force of magnitude c(4)/(2G). This remains true if one considers the simplest form of correction due to the generalized uncertainty principle. We comment on the maximum force conjecture, the subtleties involved, as well as the discrepancies with previous results in the literature.

• 123. Reig, Mario
Stockholm University, Faculty of Science, Department of Physics. MIT, USA; Shanghai Jiao Tong University, China; Arizona State University, USA.
A model of comprehensive unification2017In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 774, p. 667-670Article in journal (Refereed)

Comprehensive - that is, gauge and family - unification using spinors has many attractive features, but it has been challenged to explain chirality. Here, by combining an orbifold construction with more traditional ideas, we address that difficulty. Our candidate model features three chiral families and leads to an acceptable result for quantitative unification of couplings. A potential target for accelerator and astronomical searches emerges.

• 124.
Kernforschungszentrum, Universität Karlsruche.
Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory . Institute for Physics, University of Basle. Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory . Kernforschungszentrum, Universität Karlsruche. Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory . Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Institute for Physics, University of Basle. Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory . Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Institute for Physics, University of Basle. Kernforschungszentrum, Universität Karlsruche. Kernforschungszentrum, Universität Karlsruche. Institute for Physics, University of Basle. Centre de recherches nucléaries and Université Louis Pasteur, Strabourg. Institute for Physics, University of Basle. Institute for Physics, University of Basle. Dept. of Nuclear Physics, Univerity of Tessaloniki.
New results in the search for narrow states in the p system below threshold1983In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 126, no 3-4, p. 284-288Article in journal (Refereed)

The γ-ray spectrum after p annihilation at rest was measured in two independent high-statistics runs. Both spectra show narrow peaks, corresponding to masses of 1210, 1638, 1694 and 1771 MeV.

• 125. Schonning, K.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University. Stockholm University. Stockholm University. Stockholm University.
Polarisation of the omega meson in the pd -> He-3 omega reaction at 1360 and 1450 MeV2008In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 668, no 4, p. 258-262Article in journal (Refereed)

The tensor polarisation of omega mesons produced in the pd -> He-3 omega reaction has been studied at two energies near threshold. The 3 He nuclei were detected in coincidence with the pi(0)pi(+)pi(-) or pi(0)gamma decay products of the omega. in contrast to the case of phi-meson production, the omega mesons are found to be unpolarised. This brings into question the applicability of the Okubo-Zweig-lizuka rule when comparing the production of vector mesons in low energy hadronic reactions.

• 126. Schonning, K.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics.
The pd -> He-3 eta pi(0) reaction at T-p=1450 MeV CELSIUS/WASA Collaboration2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 685, no 1, p. 33-37Article in journal (Refereed)

The cross section for the pd -> He-3 eta pi(0) reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring. The He-3 was detected in coincidence with four photons from the decays of the two mesons. The data indicate that the production mechanism involves the formation of the Delta(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant mass distributions Of all three pairs of final particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the pi(0) momentum in the He-3 pi(0) system.

• 127. Skorodko, T.
Stockholm University, Faculty of Science, Department of Physics.
Delta Delta excitation in proton-proton induced pi(0)pi(0) production2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 695, no 1-4, p. 115-123Article in journal (Refereed)

Exclusive measurements of the pp -> pp pi(0)pi(0) reaction have been performed at CELSIUS/WASA at energies from threshold up to T(p) = 1.3 GeV. Total and differential cross sections have been obtained. Here we concentrate on energies T(p) >= GeV. where the Delta Delta excitation becomes the leading process. No evidence is found for a significant ABC effect beyond that given by the conventional t-channel Delta Delta excitation. This holds also for the double-pionic fusion to the quasibound (2)He. The data are compared to model predictions, which are based on both pi- and rho-exchange. Total and differential cross sections are at variance with these predictions and call for a profound modification of the rho-exchange. A phenomenological modification allowing only a small rho-exchange contribution leads to a quantitative description of the data.

• 128.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, USA. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Center for Theoretical Physics, MIT, USA.
Dilute and dense axion stars2018In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 777, p. 64-72Article in journal (Refereed)

Axion stars are hypothetical objects formed of axions, obtained as localized and coherently oscillating solutions to their classical equation of motion. Depending on the value of the field amplitude at the core vertical bar theta(0)vertical bar vertical bar theta(r = 0)vertical bar, the equilibrium of the system arises from the balance of the kinetic pressure and either self-gravity or axion self-interactions. Starting from a general relativistic framework, we obtain the set of equations describing the configuration of the axion star, which we solve as a function of vertical bar theta(0)vertical bar. For small vertical bar theta(0)vertical bar less than or similar to 1, we reproduce results previously obtained in the literature, and we provide arguments for the stability of such configurations in terms of first principles. We compare qualitative analytical results with a numerical calculation. For large amplitudes vertical bar theta(0)vertical bar greater than or similar to 1, the axion field probes the full non-harmonic QCD chiral potential and the axion star enters the densebranch. Our numerical solutions show that in this latter regime the axions are relativistic, and that one should not use a single frequency approximation, as previously applied in the literature. We employ a multi-harmonic expansion to solve the relativistic equation for the axion field in the star, and demonstrate that higher modes cannot be neglected in the dense regime. We interpret the solutions in the dense regime as pseudo-breathers, and show that the life-time of such configurations is much smaller than any cosmological time scale.

• 129.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Uppsala University, Sweden.
Two-point functions of SU(2)-subsector and length-two operators in dCFT2017In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 773, p. 435-439Article in journal (Refereed)

We consider a particular set of two-point functions in the setting of N=4SYM with a defect, dual to the fuzzy-funnel solution for the probe D5-D3-brane system. The two-point functions in focus involve a single trace operator in the SU(2)-subsector of arbitrary length and a length-two operator built out of any scalars. By interpreting the contractions as a spin-chain operator, simple expressions were found for the leading contribution to the two-point functions, mapping them to earlier known formulas for the one-point functions in this setting.

• 130.
Stockholm University, Faculty of Science, Department of Physics.
Dependence of the $t\bar{t}$ Production Cross Section on the Transverse Momentum of the Top Quark2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 693, no 5, p. 515-521Article in journal (Refereed)

We present a measurement of the differential cross section for events produced in collisions at as a function of the transverse momentum (pT) of the top quark. The selected events contain a high-pT lepton (), a large imbalance in pT, four or more jets with at least one candidate for a b jet, and correspond to 1 fb−1 of integrated luminosity recorded with the D0 detector. Objects in the event are associated through a constrained kinematic fit to the process. Results from next and next-to-next-to-leading-order perturbative QCD calculations agree with the measured differential cross section. Comparisons are also provided to predictions from Monte Carlo event generators using QCD calculations at different levels of precision.

• 131.
Stockholm University, Faculty of Science, Department of Physics.
Determination of the Pole and $\bar{MS}$ Masses of the top quark from the $t\bar{t}$ Cross Section2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 703, no 4, p. 422-427Article in journal (Refereed)
• 132.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
High Mass Exclusive Diffractive Dijet Production in $p\bar{p}$ Collisions at $\sqrt{s}$ = 1.96 TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, no 3, p. 193-199Article in journal (Refereed)
• 133.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of Direct Photon Pair Production Cross Sections in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 690, p. 108-117Article in journal (Refereed)
• 134.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of Spin Correlation in $t\bar{t}$ Production Using Dilepton Final States2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 702, no 1, p. 16-23Article in journal (Refereed)

We measure the correlation between the spin of the top quark and the spin of the anti-top quark in final states produced in collisions at a center of mass energy , where is an electron or muon. The data correspond to an integrated luminosity of 5.4 fb−1 and were collected with the D0 detector at the Fermilab Tevatron collider. The correlation is extracted from the angles of the two leptons in the t and rest frames, yielding a correlation strength , in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.

• 135.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of the Dijet Invariant Mass Cross Section in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 693, no 5, p. 531-538Article in journal (Refereed)

The inclusive dijet production double differential cross section as a function of the dijet invariant mass and of the largest absolute rapidity of the two jets with the largest transverse momentum in an event is measured in collisions at using 0.7 fb−1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The measurement is performed in six rapidity regions up to a maximum rapidity of 2.4. Next-to-leading order perturbative QCD predictions are found to be in agreement with the data.

• 136.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of the Normalized $Z/\gamma^*\to\mu^+\mu^-$ Transverse Momentum Distribution in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 693, no 5, p. 522-530Article in journal (Refereed)

We present a new measurement of the Z/γ transverse momentum distribution in the range 0–330 GeV, in proton–antiproton collisions at . The measurement uses 0.97 fb−1 of integrated luminosity recorded by the D0 experiment and is the first using the Z/γμ+μ+X channel at this center-of-mass energy. This is also the first measurement of the Z/γ transverse momentum distribution that presents the result at the level of particles entering the detector, minimizing dependence on theoretical models. As any momentum of the Z/γ in the plane transverse to the incoming beams must be balanced by some recoiling system, primarily the result of QCD radiation in the initial state, this variable is an excellent probe of the underlying process. Tests of the predictions of QCD calculations and current event generators show they have varied success in describing the data. Using this measurement as an input to theoretical predictions will allow for a better description of hadron collider data and hence it will increase experimental sensitivity to rare signals.

• 137.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of the $t\bar{t}$ Production Cross Section Using Dilepton Events in $p\bar{p}$ Collisions2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 704, no 5, p. 403-410Article in journal (Refereed)
• 138.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of the t-channel Single Top Quark Production ross Section2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 682, p. 363-369Article in journal (Refereed)
• 139.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of the $WZ\rightarrow \ell\nu\ell\ell$ Cross Section and Limits on Anomalous Triple Gauge Couplings in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 695, no 1-4, p. 67-73Article in journal (Refereed)

We present a new measurement of the WZν (=e,μ) cross section and limits on anomalous triple gauge couplings. Using 4.1 fb−1 of integrated luminosity of collisions at , we observe 34 WZ candidate events with an estimated background of 6.0±0.4 events. We measure the WZ production cross section to be , in good agreement with the standard model prediction. We find no evidence for anomalous WWZ couplings and set 95% C.L. limits on the coupling parameters, −0.077<λZ<0.093 and −0.029<ΔκZ<0.080 in the HISZ parameterization for a Λ=2 TeV form factor scale. These are the best limits to date obtained from the direct measurement of the WWZ vertex.

• 140.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of Three-Jet Differential Cross Sections $d\sigma_{3jet}/dM_{3jet}$ in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 704, no 5, p. 434-441Article in journal (Refereed)
• 141.
Stockholm University, Faculty of Science, Department of Physics.
Measurement of $Z/gamma^*$+jet+X Angular Distributions in p\bar{p}$Collisions at$\sqrt{s}=1.96$TeV}2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 682, p. 370-380Article in journal (Refereed) • 142. Stockholm University, Faculty of Science, Department of Physics. Measurements of Inclusive$W$+jets Production Rates as a Function of Jet Transverse Momentum in$p\bar{p}$Collisions at$\sqrt{s}=1.96$TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, no 3, p. 200-207Article in journal (Refereed) • 143. Stockholm University, Faculty of Science, Department of Physics. Model-independent Measurement of$t$-channel Single Top Quark Production in$p\bar{p}$Collisions at$\sqrt{s}=1.96$TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, no 4, p. 313-319Article in journal (Refereed) We present a model-independent measurement of t-channel electroweak production of single top quarks in p collisions at root s = 1.96 TeV. Using 5.4 fb(-1) of integrated luminosity collected by the DO detector at the Fermilab Tevatron Collider, and selecting events containing an isolated electron or muon, missing transverse energy and one or two jets originating from the fragmentation of b quarks, we measure a cross section sigma (p (p) over bar -> tqb + X) = 2.90 +/- 0.59 (stat + syst) pb for a top quark mass of 172.5 GeV. The probability of the background to fluctuate and produce a signal as large as the one observed is 1.6 x 10(-8), corresponding to a significance of 5.5 standard deviations. • 144. Stockholm University, Faculty of Science, Department of Physics. Search for a Heavy Neutral Gauge Boson in the Dielectron Channel with 5.4 fb$^{-1}$of$p\bar{p}$Collisions at$\sqrt{s} = 1.96$TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 695, no 1-4, p. 88-94Article in journal (Refereed) We report the results of a search for a heavy neutral gauge boson Z decaying into the dielectron final state using data corresponding to an integrated luminosity of 5.4 fb−1 collected by the D0 experiment at the Fermilab Tevatron Collider. No significant excess above the standard model prediction is observed in the dielectron invariant-mass spectrum. We set depending on the dielectron invariant mass. These cross section limits are used to determine lower mass limits for Z bosons in a variety of models. For the sequential standard model Z boson a lower mass limit of 1023 GeV is obtained. • 145. Stockholm University, Faculty of Science, Department of Physics. Search for Anomalous$Wtb$Couplings in Single Top Quark Production in$p\bar{p}$Collisions at$\sqrt{s}=1.96$TeV2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 708, p. 21-26Article in journal (Refereed) We present new direct constraints on a general Wtb interaction using data corresponding to an integrated luminosity of 5.4 fb−1 collected by the D0 detector at the Tevatron collider. The standard model provides a purely left-handed vector coupling at the Wtb vertex, while the most general, lowest dimension Lagrangian allows right-handed vector and left- or right-handed tensor couplings as well. We obtain precise limits on these anomalous couplings by comparing the data to the expectations from different assumptions on the Wtb coupling • 146. Stockholm University, Faculty of Science, Department of Physics. Search for Charged Higgs Bosons in Top Quark Decays2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 682, p. 278-286Article in journal (Refereed) We present a search for charged Higgs bosons in top quark decays. We analyze the e+jets, μ+jets, ee, , μμ, τe and τμ final states from top quark pair production events, using data from about 1 fb−1 of integrated luminosity recorded by the DØ experiment at the Fermilab Tevatron Collider. We consider different scenarios of possible charged Higgs boson decays, one where the charged Higgs boson decays purely hadronically into a charm and a strange quark, another where it decays into a τ lepton and a τ neutrino and a third one where both decays appear. We extract limits on the branching ratio B(tH+b) for all these models. We use two methods, one where the production cross section is fixed, and one where the cross section is fitted simultaneously with B(tH+b). Based on the extracted limits, we exclude regions in the charged Higgs boson mass and tanβ parameter space for different scenarios of the minimal supersymmetric standard model • 147. Stockholm University, Faculty of Science, Department of Physics. Search for Flavor Changing Neutral Currents in Decays of Top Quarks2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, no 3, p. 313-320Article in journal (Refereed) We present a search for flavor changing neutral currents in decays of top quarks. The analysis is based on a search for (,=e,μ) final states using 4.1 fb−1 of integrated luminosity of collisions at . We extract limits on the branching ratio B(tZq) (q=u,c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B<3.2% at 95% C.L. • 148. Stockholm University, Faculty of Science, Department of Physics. Search for flavor changing neutral currents via quark–gluon couplings in single top quark production using 2.3 fb−1 of collisions2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 693, no 2, p. 81-87Article in journal (Refereed) We present a search for flavor changing neutral currents via quark–gluon couplings in a sample of single top quark final states corresponding to 2.3 fb−1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are σtgu<0.20 pb and σtgc<0.27 pb. These correspond to limits on the top quark decay branching fractions of B(tgu)<2.0×10−4 and B(tgc)<3.9×10−3. • 149. Stockholm University, Faculty of Science, Department of Physics. Search for Higgs bosons of the minimal supersymmetric standard model in p(p)over-bar collisions at root s=1.96 TeV D0 Collaboration2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 710, no 4-5, p. 569-577Article in journal (Refereed) We report results from searches for neutral Higgs bosons produced in p (p) over bar collisions recorded by the D0 experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the tau tau final state and in association with a b quark in the b tau tau and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tan beta > 20-30 for Higgs boson masses below 180 GeV. These are the most stringent constraints on MSSM Higgs boson production in p (p) over bar collisions. • 150. Stockholm University, Faculty of Science, Department of Physics. Search for Neutral Higgs Bosons in the Multi-b-jet Topology in 5.2fb$^{-1}$of$p\bar{p}$Collisions at$\sqrt{s}=1.96\$ TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 698, no 2, p. 97-104Article in journal (Refereed)

Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2 fb−1. In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model.

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