Change search
Refine search result
13141516 751 - 791 of 791
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 751.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Eriksson, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Gellerstedt, Karl
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hellman, Sten
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansen, Marianne
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, K. Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Jon-And, Kerstin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kim, Hyeon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Klimek, Pawel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lesser, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Lundberg, Johan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Milstead, David A.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Nordkvist, Björn
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ohm, Christian C.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Papadelis, Aras
    Stockholm University, Faculty of Science, Department of Physics.
    Sellden, Björn
    Stockholm University, Faculty of Science, Department of Physics.
    Silverstein, Samuel B.
    Stockholm University, Faculty of Science, Department of Physics.
    Sjölin, Jörgen
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Tylmad, Maja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Yang, Zhaoyu
    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 polarisation of W bosons produced with large transverse momentum in pp collisions at root s=7 TeV with the ATLAS experiment2012In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 72, no 5, p. 2001-Article in journal (Refereed)
    Abstract [en]

    This paper describes an analysis of the angular distribution of W -> e nu and W -> mu nu decays, using data from pp collisions at root s = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb(-1). Using the decay lepton transverse momentum and the missing transverse momentum, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f(0), f(L) and f(R) over two ranges of W transverse momentum (p(T)(W)) : 35 < p(T)(W) < 50 GeV and p(T)(W) > 50 GeV. Good agreement is found with theoretical predictions. For p(T)(W) > 50 GeV, the values of f(0) and f(L) - f(R), averaged over charge and lepton flavour, are measured to be: f(0) = 0.127 +/- 0.030 +/- 0.108 and f(L) - f(R) = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.

  • 752.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Hansson, Per
    Sjölin, Jörgen
    Stockholm University, Faculty of Science, Department of Physics.
    Tylmad, Maja
    Stockholm University, Faculty of Science, Department of Physics.
    Fake Isolated Muon Background in Searches for Supersymmetry with two Muons in the Final State2010Report (Other academic)
    Abstract [en]

    We study a data-driven technique to derive the contamination from fake isolated muons in a search for supersymmetric (SUSY) particles, in final states with two high pT muons. The signal sample is characterized by jets, missing transverse energy and two high pT muons, isolated from calorimeter energy. In real data, a fraction of the selected events will arise from processes where at least one of the isolated muons is not truly isolated, but rather arises in conjunction with a jet. We illustrate how to determine the contribution from fake isolated muons, to the signal sample. The method is demonstrated with a simple SUSY analysis of the di-muon sample. We study a range of potential systematic effects arising from the extrapolation from the control sample to the signal region.

  • 753.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Evidence for production of single top quarks and first direct measurement of vertical bar V-tb vertical bar2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 98, no 18, p. 181802-Article in journal (Refereed)
    Abstract [en]

    The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron < p(p)over bar > collider. Using a 0.9 fb(-1) dataset, we apply a multivariate analysis to separate signal from background and measure sigma(< p(p)over bar >-> tb+X,tqb+X)=4.9 +/- 1.4 pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.035%, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa matrix element that describes the Wtb coupling and find 0.68 <vertical bar V-tb vertical bar <= 1 at 95% C.L. within the standard model.

  • 754.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental Discrimination Between Charge 2e/3 Top Quark and Charge 4e/3 Exotic Quark Production Scenarios2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 98, no 4, p. 041801-Article in journal (Refereed)
    Abstract [en]

    We present the first experimental discrimination between the 2e/3 and 4e/3 top quark electric charge scenarios, using top quark pairs (t (t) over bar) produced in p (p) over bar collisions at root s =1.96 TeV by the Fermilab Tevatron Collider. We use 370 pb(-1) of data collected by the D0 experiment and select events with at least one high transverse momentum electron or muon, high transverse energy imbalance, and four or more jets. We discriminate between b- and (b) over bar -quark jets by using the charge and momenta of tracks within the jet cones. The data are consistent with the expected electric charge, |q|=2e/3. We exclude, at the 92% C.L., that the sample is solely due to the production of exotic quark pairs Q (Q) over bar with |q|=4e/3. We place an upper limit on the fraction of Q (Q) over bar pairs rho < 0.80 at the 90% C.L

  • 755.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Lifetime Difference and CP-Violating Phase in the $B_s^0$ System2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 98, no 12, p. 121801-Article in journal (Refereed)
    Abstract [en]

    From an analysis of the decay B-s(0)-> J/psi phi, we obtain the width difference between the light and heavy mass eigenstates Delta Gamma equivalent to(Gamma(L)-Gamma(H))=0.17 +/- 0.09(stat)+/- 0.02(syst) ps(-1) and the CP-violating phase phi(s)=-0.79 +/- 0.56(stat)(-0.01)(+0.14)(syst). Under the hypothesis of no CP violation (phi(s)equivalent to 0), we obtain 1/Gamma=tau/(B-s(0))=1.52 +/- 0.08(stat)(-0.03)(+0.01)(syst) ps and Delta Gamma=0.12(-0.10)(+0.08)(stat)+/- 0.02(syst) ps(-1). The data sample corresponds to an integrated luminosity of about 1.1 fb(-1) accumulated with the D0 detector at the Fermilab Tevatron collider. This is the first direct measurement of the CP-violating mixing phase in the B-s(0) system.

  • 756.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the charge asymmetry in semileptonic B-s(0) decays2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Physical Review Letters, Vol. 98, no 15, p. 151801-Article in journal (Refereed)
    Abstract [en]

    We have performed the first direct measurement of the time-integrated flavor untagged charge asymmetry in semileptonic B-s(0) decays A(SL)(s,unt) by comparing the decay rate of B-s(0) -> mu(+) D-s(-) nu X, where D-s(-) -> phi pi(-) and phi -> K+K-, with the charge-conjugate (B) over bar (0)(s) decay rate. This sample was selected from 1: 3 fb(-1) of data collected by the D0 experiment in run II of the Fermilab Tevatron collider. We obtain A(SL)(s,unt) = [1.23 +/- 0.97(stat) +/- 0.17(syst)] x 10(-2). Assuming that Delta m(s)/(Gamma) over bar (s) >> 1, this result can be translated into a measurement of the CP-violating phase in B-s(0) mixing: Delta Gamma(s)/Delta m(s) tan phi(s) = [2.45 +/- 1.93(stat) +/- 0.35(syst)] x 10(-2).

  • 757.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Single Production of Scalar Leptoquarks in $p-ar{p}$ Collisions Decaying into Muons and Quarks with the D0 Detector2007In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 647, no 2-3, p. 74-81Article in journal (Refereed)
    Abstract [en]

    lWe report on a search for second generation leptoquarks (LQ(2)) which decay into a muon plus quark in (p) over barp collisions at a center-of-mass energy of root s = 1.96 TeV in the DO detector using an integrated luminosity of about 300 pb(-1). No evidence for a leptoquark signal is observed and an upper bound on the product of the cross section for single leptoquark production times branching fraction into a quark and a muon was determined for second generation scalar leptoquaiks as a function of the leptoquark mass. This result has been combined with a previously published DO search for leptoquark pair production to obtain leptoquark mass limits as a function of the leptoquark-muon-quark coupling, lambda. Assuming lambda = 1, lower limits on the mass of a second generation scalar leptoquark coupling to a u quark and a muon are m(LQ2) > 274 GeV and m(LQ2) > 226 GeV for beta = 1 and beta = 1/2, respectively.

  • 758.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for techniparticles in e plus jets events at D02007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 98, no 22, p. 221801-Article in journal (Refereed)
    Abstract [en]

     We search for the technicolor process p(p) over bar ->rho(T)/omega(T)-> W pi(T) in events containing one electron and two jets, in data corresponding to an integrated luminosity of 390 pb(-1), recorded by the D0 experiment at the Fermilab Tevatron. Technicolor predicts that technipions pi(T) decay dominantly into b(b) over bar, b(c) over bar, or (b) over barc, depending on their charge. In these events b and c quarks are identified by their secondary decay vertices within jets. Two analysis methods based on topological variables are presented. Since no excess above the standard model prediction was found, the result is presented as an exclusion in the pi(T) vs rho(T) mass plane for a given set of model parameters.

  • 759.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for the Pair Production of Scalar Top Quarks in the Acoplanar Charm Jet Topology in ppbar Collisions at sqrt(s)=1.96 TeV2007In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 645, no 2-3, p. 119-127Article in journal (Refereed)
    Abstract [en]

    A search for the pair production of scalar top quarks, (t) over tilde, has been performed in 360 pb(-1) of data from pp collisions at a center-of-mass energy of 1.96 TeV, collected by the D phi detector at the Fermilab Tevatron collider. The (t) over tilde decay mode considered is (t) over tilde -> c (chi) over tilde (0)(1), where (chi) over tilde (0)(1) is the lightest supersymmetric particle. The topology analyzed therefore consists of a pair of acoplanar heavy-flavor jets with missing transverse energy. The data and standard model expectation are in agreement, anda 95% C.L. exclusion domain in the (m((t) over tilde), m((chi) over tilde1)(0)) plane has been determined, extending the domain excluded by previous experiments.

  • 760.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Strandberg
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the top quark mass in the lepton plus jets channel using the ideogram method2007In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 75, no 9, p. 092001-Article in journal (Refereed)
    Abstract [en]

    A measurement of the top quark mass using events with one charged lepton, missing transverse energy, and jets in the final state, collected by the D0 detector from p (p) over bar collisions at root s=1.96 TeV at the Fermilab Tevatron collider, is presented. A constrained fit is used to fully reconstruct the kinematics of the events. For every event a top quark mass likelihood is calculated taking into account all possible jet assignments and the probability that an event is signal or background. Lifetime-based identification of b jets is employed to enhance the separation between t (t) over bar signal and background from other physics processes and to improve the assignment of the observed jets to the quarks in the t (1) over bar hypothesis. We extract a multiplicative jet energy scale (JES) factor in situ, greatly reducing the systematic effect related to the jet energy measurement. In a data sample with an integrated luminosity of 425 pb(-1), we observe 230 candidate events, with an estimated background of 123 events, and measure m(t)=173.7 +/- 4.4(stat+JES)(-2.0)(+2.1)(syst) GeV. This result represents the first application of the ideogram technique to the measurement of the top quark mass in lepton+jets events.

  • 761.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik K.
    Stockholm University, Faculty of Science, Department of Physics.
    Leinonen, Lena
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the electron structure function F-2(e) at LEP energies2014In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 737, p. 39-47Article in journal (Refereed)
    Abstract [en]

    The hadronic part of the electron structure function F-2(e) has been measured for the first time, using e(+)e(-) data collected by the DELPHI experiment at LEP, at centre-of-mass energies of root s = 91.2-209.5 GeV. The data analysis is simpler than that of the measurement of the photon structure function. The electron structure function F-2(e) data are compared to predictions of phenomenological models based on the photon structure function. It is shown that the contribution of large target photon virtualities is significant. The data presented can serve as a cross-check of the photon structure function F-2(gamma) analyses and help in refining existing parameterisations.

  • 762.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    A Study of $b\bar{b}$ Production in $e^+e^-$ Collisions at $\sqrt{s} = 130-207$ GeV2009In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 60, p. 1-15Article in journal (Refereed)
    Abstract [en]

    Measurements are presented of R b, the ratio of the b[`(b)]bb  cross-section to the q[`(q)]qq cross-section in e+e collisions, and the forward-backward asymmetry A FBb at twelve energy points in the range Ös=130s=130  –207 GeV. These results are found to be consistent with the Standard Model expectations. The measurements are used to set limits on new physics scenarios involving contact interactions.

  • 763.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    A Study of the b-quark Fragmentation Function with the DELPHI Detector at LEP I and an Averaged Distribution Obtained at the Z Pole2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 2, p. 1557-Article in journal (Refereed)
    Abstract [en]

    The nature of b-quark jet hadronisation has been investigated using data taken at the Z peak by the DELPHI detector at LEP. Two complementary methods are used to reconstruct the energy of weakly decaying b-hadrons, E(B)(weak). The average value of x(B)(weak) = E(B)(weak)/E(beam) is measured to be 0.699 +/- 0.011. The resulting x(B)(weak) distribution is then analysed in the framework of two choices for the perturbative contribution (parton shower and Next to Leading Log QCD calculation) in order to extract measurements of the non-perturbative contribution to be used in studies of b-hadron production in other experimental environments than LEP. In the parton shower framework, data favour the Lund model ansatz and corresponding values of its parameters have been determined within PYTHIA 6.156 from DELPHI data: a = 1.84(-0.21)(+0.23) and b = 0.642(-0.063)(+0.073) GeV(-2), with a correlation factor rho = 92.2%. Combining the data on the b-quark fragmentation distributions with those obtained at the Z peak by ALEPH, OPAL and SLD, the average value of x(B)(weak) is found to be 0.7092 +/- 0.0025 and the non-perturbative fragmentation component is extracted. Using the combined distribution, a better determination of the Lund parameters is also obtained: a = 1.48(-0.10)(+0.11) and b = 0.509(-0.023)(+0.024) GeV(-2), with a correlation factor rho = 92.6%.

  • 764.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    Correlations Between Polarisation States of W Particles in the Reaction $e^-e^+\to W^-W^+$ at LEP2 Energies 189--209 GeV2009In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 63, p. 611-623Article in journal (Refereed)
  • 765.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    Inclusive Single-Particle Production in Two-Photon Collisions at LEP II with the DELPHI Detector2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 678, p. 444-449Article in journal (Refereed)
  • 766.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    Measurements of CP-conserving Trilinear Gauge Boson Couplings WWV (V$\equiv\gamma$,Z) in $e^+e^-$ Collisions at LEP22010In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 66, p. 35-56Article in journal (Refereed)
    Abstract [en]

    The data taken by Delphi at centre-of-mass energies between 189 and 209 GeV are used to place limits on the CP-conserving trilinear gauge boson couplings , λ γ and Δκ γ associated to W + W and single W production at Lep2. Using data from the jj ν, jjjj, jjX and X final states, where j, and X represent a jet, a lepton and missing four-momentum, respectively, the following limits are set on the couplings when one parameter is allowed to vary and the others are set to their Standard Model values of zero: Results are also presented when two or three parameters are allowed to vary. All observations are consistent with the predictions of the Standard Model and supersede the previous results on these gauge coupling parameters published by Delphi. This paper is dedicated to the memory of Professor Paul Booth who was Delphi Deputy Spokesperson from 1989 to 1994. He played a key role in the final installation and commissioning of the Delphi detector as well as leading the Liverpool group for many years thereafter

  • 767.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    Search for One Large Extra Dimension with the DELPHI Detector at LEP2009In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 60, p. 17-23Article in journal (Refereed)
    Abstract [en]

    Single photons detected by the DELPHI experiment at LEP2 in the years 1997–2000 are reanalysed to investigate the existence of a single extra dimension in a modified ADD scenario with slightly warped large extra dimensions. The data collected at centre-of-mass energies between 180 and 209 GeV for an integrated luminosity of ∼650 pb−1 agree with the predictions of the Standard Model and allow a limit to be set on graviton emission in one large extra dimension. The limit obtained on the fundamental mass scale M D is 1.69 TeV/c 2 at 95% CL, with an expected limit of 1.71 TeV/c 2.

  • 768.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Single Top Quark Production via Contact Interactions at LEP22011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 2, p. 1555-Article in journal (Refereed)
    Abstract [en]

    Single top quark production via four-fermion contact interactions associated to flavour-changing neutral currents was searched for in data taken by the DELPHI detector at LEP2. The data were accumulated at centre-of-mass energies ranging from 189 to 209 GeV, with an integrated luminosity of 598.1 pb−1. No evidence for a signal was found. Limits on the energy scale Λ, were set for scalar-, vector- and tensor-like coupling scenarios.

  • 769.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    Study of the Dependence of Direct Soft Photon Production on the Jet Characteristics in Hadronic Z Decays2010In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 67, p. 343-366Article in journal (Refereed)
    Abstract [en]

    An analysis of the direct soft photon production rate as a function of the parent jet characteristics is presented, based on hadronic events collected by the DELPHI experiment at LEP1. The dependences of the photon rates on the jet kinematic characteristics (momentum, mass, etc.) and on the jet charged, neutral and total hadron multiplicities are reported. Up to a scale factor of about four, which characterizes the overall value of the soft photon excess, a similarity of the observed soft photon behavior to that of the inner hadronic bremsstrahlung predictions is found for the momentum, mass, and jet charged multiplicity dependences. However for the dependence of the soft photon rate on the jet neutral and total hadron multiplicities a prominent difference is found for the observed soft photon signal as compared to the expected bremsstrahlung from final state hadrons. The observed linear increase of the soft photon production rate with the jet total hadron multiplicity and its strong dependence on the jet neutral multiplicity suggest that the rate is proportional to the number of quark pairs produced in the fragmentation process, with the neutral pairs being more effectively radiating than the charged ones

  • 770.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jon-And, Kerstin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the production fraction times branching fraction f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda)2011In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 84, no 3, p. 031102-Article in journal (Refereed)
    Abstract [en]

    The Lambda(b)(udb) baryon is observed in the decay Lambda(b) -> J/psi Lambda using 6.1fb(-1) of p (p) over bar collisions collected with the D0 detector at root s = 1/96 TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B(0) -> J/psi K(s)(0) is measured to be 0.345 +/- 0.034(stat) +/- 0.033(syst) +/- 0.003(PDG). Using the world average value of f(b -> B(0)) . B(B(0) -> J/psi K(s)(0) = (1.74 +/- 0.08) x 10(-5), we obtain f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda) = (6.01 +/- 0.60(stat) +/- 0.58(syst) +/- 0.28(PDG)) x 10(-5). This measurement represents an improvement in precision by about a factor of 3 with respect to the current world average.

  • 771.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Combination of $t\bar{t}$ Cross Section Measurements and Constraints on the Mass of the Top Quark and its Decays into Charged Higgs Bosons2009In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 80, p. 071102-Article in journal (Refereed)
    Abstract [en]

    We combine measurements of the top quark pair production cross section in pp̅ collisions in the ℓ+jets, ℓℓ, and τℓ final states (where ℓ is an electron or muon) at a center of mass energy of √s=1.96  TeV in 1  fb-1 of data collected with the D0 detector. For a top quark mass of 170  GeV/c2, we obtain σtt̅ =8.18-0.87+0.98  pb in agreement with the theoretical prediction. Based on predictions from higher order quantum chromodynamics, we extract a mass for the top quark from the combined tt̅ cross section, consistent with the world average of the top quark mass. In addition, the ratios of tt̅ cross sections in different final states are used to set upper limits on the branching fractions B(t→H+b→τ+νb) and B(t→H+b→cs̅ b) as a function of the charged Higgs boson mass.

  • 772.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Evidence for Decay $B_s^0\to D_s^{(\ast)}D_s^{(\ast)}$ and a Measurement of $\Delta\Gamma_s^{CP}/\Gamma_s$2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 091801-Article in journal (Refereed)
    Abstract [en]

    We search for the semi-inclusive process Bs0→Ds(*)Ds(*) using 2.8  fb-1 of pp̅ collisions at √s=1.96  TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We observe 26.6±8.4 signal events with a significance above background of 3.2 standard deviations yielding a branching ratio of B(Bs0→Ds(*)Ds(*))=0.035±0.010(stat.)±0.011(syst.). Under certain theoretical assumptions, these double-charm final states saturate CP-even eigenstates in the Bs0 decays resulting in a width difference of ΔΓsCPs=0.072±0.021(stat.)±0.022(syst.).

  • 773.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Evidence of $WW$ and $WZ$ Production with Lepton + Jets Final States in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 161801-Article in journal (Refereed)
    Abstract [en]

    We present first evidence for WW+WZ production in lepton+jets final states at a hadron collider. The data correspond to 1.07  fb-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron in pp̅ collisions at √s=1.96  TeV. The observed cross section for WW+WZ production is 20.2±4.5  pb, consistent with the standard model and more precise than previous measurements in fully leptonic final states. The probability that background fluctuations alone produce this excess is <5.4×10-6, which corresponds to a significance of 4.4 standard deviations.

  • 774.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of $\gamma+b+X$ and $\gamma+c+X$ Production Cross Sections in $p\bar{p}$ Collisions at $\sqrt{s}=$1.96 TeV2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 192002-Article in journal (Refereed)
    Abstract [en]

    First measurements of the differential cross sections d3σ/(dpTγdyγdyjet) for the inclusive production of a photon in association with a heavy quark (b, c) jet are presented, covering photon transverse momenta 30<pTγ<150  GeV, photon rapidities |yγ|<1.0, jet rapidities |yjet|<0.8, and jet transverse momenta pTjet>15  GeV. The results are based on an integrated luminosity of 1  fb-1 in pp̅ collisions at √s=1.96  TeV recorded with the D0 detector at the Fermilab Tevatron Collider. The results are compared with next-to-leading order perturbative QCD predictions.

  • 775.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the $t\bar{t}$ Production Cross Section and Top Quark Mass Extraction Using Dilepton Events in $p\bar{p}$ Collisions2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 679, p. 177-185Article in journal (Refereed)
  • 776.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the Top Quark Mass in Final States with Two Leptons2009In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 80, p. 092006-Article in journal (Refereed)
  • 777.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the $WW$ Production Cross Section with Dilepton Final States in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV and Limits on Anomalous Trilinear Gauge Couplings}2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, p. 191801-Article in journal (Refereed)
  • 778.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the $Z\gamma\to\nu\bar{\nu}\gamma$ Cross Section and Limits on Anomalous $ZZ\gamma$ and $Z\gamma\gamma$ Couplings in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 201802-Article in journal (Refereed)
    Abstract [en]

    We present the first observation of the Zγ→νν̅ γ process at the Fermilab Tevatron at 5.1 standard deviations significance, based on 3.6  fb-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp̅ Collider at √s=1.96  TeV. The measured Zγ production cross section multiplied by the branching fraction of Z→νν̅ is 32±9(stat+syst)±2(lumi)  fb for the photon ET>90  GeV. It is in agreement with the standard model prediction of 39±4  fb. We set limits on anomalous trilinear Zγγ and ZZγ gauge boson couplings, most of which are the most restrictive to date.

  • 779.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Measurements of Differential Cross Sections of $Z/\gamma^*$+jets+X Events in $\bar{p}p$ Collisions at $\sqrt{s}=1.96$ TeV}2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 678, p. 45-54Article in journal (Refereed)
  • 780.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Model-independent Measurement of the W-Boson Helicity in Top-Quark Decays at D02008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 6, p. 062004-Article in journal (Refereed)
    Abstract [en]

    We present the first model-independent measurement of the helicity of W bosons produced in top quark decays, based on a 1 fb(-1) sample of candidate t (t) over bar events in the dilepton and lepton plus jets channels collected by the D0 detector at the Fermilab Tevatron p (p) over bar Collider. We reconstruct the angle theta(*) between the momenta of the down-type fermion and the top quark in the W boson rest frame for each top quark decay. A fit of the resulting cos theta(*) distribution finds that the fraction of longitudinal W bosons f(0)=0.425 +/- 0.166(stat)+/- 0.102(syst) and the fraction of right-handed W bosons f(+)=0.119 +/- 0.090(stat)+/- 0.053(syst), which is consistent at the 30% C.L. with the standard model.

  • 781.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Observation of Single Top Quark Production2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, p. 092001-Article in journal (Refereed)
  • 782.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Relative Rates of B Meson Decays into $\psi(2S)$ and $J/\psi$ Mesons2009In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 79, p. 111102-Article in journal (Refereed)
  • 783.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Admixture of Scalar Top Quarks in the $t\bar{t}$ Lepton+Jets Final State at $\sqrt{s}=$1.96 TeV2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 674, p. 4-10Article in journal (Refereed)
    Abstract [en]

    A search for pair production of the lightest supersymmetric partner of the top quark, , is performed in the lepton + jets channel using 0.9 fb−1 of data collected by the DØ experiment. Kinematic differences between and the dominant top quark pair production background are used to separate the two processes. First limits from Run II of the Fermilab Tevatron Collider for the scalar top quark decaying to a chargino and a b quark () are obtained for scalar top quark masses of 130–190 GeV and chargino masses of 90–150 GeV.

  • 784.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Anomalous Top Quark Couplings with the D0 Detector2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 092002-Article in journal (Refereed)
    Abstract [en]

    Anomalous Wtb couplings modify the angular correlations of the top-quark decay products and change the single top-quark production cross section. We present limits on anomalous top-quark couplings by combining information from W boson helicity measurements in top-quark decays and anomalous coupling searches in the single top-quark final state. We set limits on right-handed vector couplings as well as left-handed and right-handed tensor couplings based on about 1  fb-1 of data collected by the D0 experiment.

  • 785.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Associated Production of Charginos and Neutralinos in the Trilepton Final State Using 2.3 fb$^{-1}$ of Data2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 680, p. 34-43Article in journal (Refereed)
  • 786.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Charged Higgs Bosons Decaying into Top and Bottom Quarks in $p\bar{p}$ Collisions2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 191802-Article in journal (Refereed)
    Abstract [en]

    We describe a search for production of a charged Higgs boson, qq̅ →H+, reconstructed in the tb̅ final state in the mass range 180≤MH+≤300  GeV. The search was undertaken at the Fermilab Tevatron collider with a center-of-mass energy √s=1.96  TeV and uses 0.9  fb-1 of data collected with the D0 detector. We find no evidence for charged Higgs boson production and set upper limits on the production cross section in the types I, II, and III two-Higgs-doublet models (2HDMs). An excluded region in the (MH+, tan⁡β) plane for type I 2HDM is presented.

  • 787.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Long-Lived Charged Massive Particles with the D0 Detector2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 161802-Article in journal (Refereed)
    Abstract [en]

    We search for long-lived charged massive particles using 1.1  fb-1 of data collected by the D0 detector at the Fermilab Tevatron pp̅ Collider. Time-of-flight information is used to search for pair produced long-lived tau sleptons, gauginolike charginos, and Higgsino-like charginos. We find no evidence of a signal and set 95% C.L. cross section upper limits for staus, which vary from 0.31 to 0.04 pb for stau masses between 60 and 300 GeV. We also set lower mass limits of 206 GeV (171 GeV) for pair produced charged gauginos (Higgsinos).

  • 788.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Resonant Diphoton Production with the D0 Detector2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 231801-Article in journal (Refereed)
  • 789.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for the lightest scalar top quark in events with two leptons in p(p)over-bar collisions at root s=1.96 TeV2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 675, no 3-4, p. 289-296Article in journal (Refereed)
    Abstract [en]

    We report results of a search for the pair production of the lightest supersymmetric partner of the top quark, (t) over bar (1), using a data set corresponding to an integrated luminosity of 1 fb(-1) collected by the D circle divide detector at a p (p) over bar center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. Both scalar top quarks are assumed to decay into a b quark, a charged lepton and a scalar neutrino. The search is performed in the electron Plus muon and dielectron final states. The signal topology consists of two isolated leptons, missing transverse energy, and jets. We find no evidence for this process and exclude regions of parameter space in the framework of the minimal supersymmetric standard model.

  • 790.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Search for the Standard Model Higgs Boson in Tau Final States2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 251801-Article in journal (Refereed)
  • 791.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Gollub, N
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the Lifetime of the $B^\pm_c$ Meson in the Semileptonic Decay Channel2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, p. 092001-Article in journal (Refereed)
    Abstract [en]

    Using approximately 1.3  fb-1 of data collected by the D0 detector between 2002 and 2006, we measure the lifetime of the Bc± meson in the Bc±→J/ψμ±+X final state. A simultaneous unbinned likelihood fit to the J/ψ+μ invariant mass and lifetime distributions yields a signal of 881±80(stat) candidates and a lifetime measurement of τ(Bc±)=0.448-0.036+0.038(stat)±0.032(syst)  ps.

13141516 751 - 791 of 791
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf