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  • 1.
    Baum, Sebastian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Dark Matter, Ancient Rocks, a Band of Higgs Bosons, and a Big Collider: or, Models of New Physics and Some Ways to Probe Them2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The past ~ 50 years have seen a remarkable success of particle physics. In the 1970s, the Standard Model was formulated and in 2012 its final ingredient, the Higgs boson, was discovered at the Large Hadron Collider (LHC). The Standard Model describes virtually all particle physics observable in the laboratory. However, despite this success, the Standard Model has a number of shortcomings. Some problems stem from its mathematical structure, most famously the hierarchy problem. Further, the Standard Model fails to describe the composition of our Universe, for example, it cannot explain the observed Dark Matter. Thus, the need for physics beyond the Standard Model is clear. A long series of experiments has been conducted to search for this new physics. Alas, these experiments came up empty handed.This thesis discusses two lines of work: 1) Arguably, the Higgs sector of the Standard Model is its least constrained part and simultaneously intimately related to many of the Standard Model's shortcomings. We discuss models extending the Higgs sector, both in a general and in a supersymmetric setting, and how they can be probed at the LHC. 2) A century after the first evidence for Dark Matter emerged, we still don't know what it is made up of. We discuss some models for Dark Matter, including axions and a particular model for Weakly Interacting Massive Particle (WIMP) Dark Matter. Then, we present some methods to search for WIMP Dark Matter, focusing on paleo-detectors, a proposed method where one would search for the traces of WIMP-nucleus interactions left in ancient minerals. 

  • 2.
    Baum, Sebastian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Digging for dark matter2019Inngår i: New scientist (1971), ISSN 0262-4079, Vol. 241, nr 3220, s. 37-39Artikkel i tidsskrift (Annet vitenskapelig)
  • 3.
    Baum, Sebastian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Exploring particle physics beyond the Standard Model2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The standard model of particle physics (SM) is arguably the best tested theory of physics, providing an accurate description of virtually all high energy particle physics phenomena observable in the laboratory. However, the SM also has a number of shortcomings: some of more theoretical nature such as the fine-tuning problem of the Higgs or the strong-CP problem, and some of more phenomenological nature such as not allowing for a satisfying implementation of neutrino masses and the lack of a suitable candidate for the observed dark matter of the Universe.

    The SM’s shortcomings have motivated the development of a large number of beyond the SM (BSM) particle physics models. However, no (conclusive) evidence for any BSM model has been found to date. The papers included in this thesis study different approaches to search for BSM physics:

    In [I], we studied bounds on weakly interacting massive particle (WIMP) DM models arising from the absence of neutrino signals from DM capture and subsequent DM pair-annihilation in dense astrophysical objects such as the Sun or the Earth. We interpreted these bounds in a model independent fashion, focusing in particular on the scaling of the bounds for the case where WIMPs comprise only a sub-dominant component of the DM. We also used a chemical composition of the Earth updated with respect to the previous literature, strengthening the bound on spin-dependent interactions from capture and annihilation in the Earth by approximately a factor 3.

    In [II], we studied the collider phenomenology of one particular BSM model, the next-to-minimal supersymmetric standard model (NMSSM). In particular, we focused on 1) the impact of the presence of the 125 GeV SM-like Higgs boson on the NMSSM parameter space, 2) the identification of NMSSM specific search channels at the LHC which allow to effectively probe the NMSSM parameter space allowed by more conventional searches, and 3) an in-depth study of one of these search channels, the mono-Higgs signature. As shown in [II], this channel allows to probe the low tan β , large m_A regime which is difficult to probe with conventional searches, and in contrast to many conventional Higgs searches, the reach of the mono-Higgs channel improves significantly with the increased luminosity expected to be collected at the LHC in current and future runs.

  • 4.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Carena, Marcela
    Shah, Nausheen R.
    Wagner, Carlos E. M.
    Higgs portals for thermal Dark Matter. EFT perspectives and the NMSSM2018Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, artikkel-id 069Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyze a low energy effective model of Dark Matter in which the thermal relic density is provided by a singlet Majorana fermion which interacts with the Higgs fields via higher dimensional operators. Direct detection signatures may be reduced if blind spot solutions exist, which naturally appear in models with extended Higgs sectors. Explicit mass terms for the Majorana fermion can be forbidden by a Z(3) symmetry, which in addition leads to a reduction of the number of higher dimensional operators. Moreover, a weak scale mass for the Majorana fermion is naturally obtained from the vacuum expectation value of a scalar singlet field. The proper relic density may be obtained by the s-channel interchange of Higgs and gauge bosons, with the longitudinal mode of the Z boson (the neutral Goldstone mode) playing a relevant role in the annihilation process. This model shares many properties with the Next-to-Minimal Supersymmetric extension of the Standard Model (NMSSM) with light singlinos and heavy scalar and gauge superpartners. In order to test the validity of the low energy effective field theory, we compare its predictions with those of the ultraviolet complete NMSSM. Extending our framework to include Z(3) neutral Majorana fermions, analogous to the bino in the NMSSM, we find the appearance of a new bino-singlino well tempered Dark Matter region.

  • 5.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Catena, Riccardo
    Conrad, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). University of Michigan, USA.
    Krauss, Martin B.
    Determining dark matter properties with a XENONnT/LZ signal and LHC Run 3 monojet searches2018Inngår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 97, nr 8, artikkel-id 083002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We develop a method to forecast the outcome of the LHC Run 3 based on the hypothetical detection of O(100) signal events at XENONnT. Our method relies on a systematic classification of renormalizable single-mediator models for dark matter-quark interactions and is valid for dark matter candidates of spin less than or equal to one. Applying our method to simulated data, we find that at the end of the LHC Run 3 only two mutually exclusive scenarios would be compatible with the detection of O(100) signal events at XENONnT. In the first scenario, the energy distribution of the signal events is featureless, as for canonical spin-independent interactions. In this case, if a monojet signal is detected at the LHC, dark matter must have spin 1/2 and interact with nucleons through a unique velocity-dependent operator. If a monojet signal is not detected, dark matter interacts with nucleons through canonical spin-independent interactions. In a second scenario, the spectral distribution of the signal events exhibits a bump at nonzero recoil energies. In this second case, a monojet signal can be detected at the LHC Run 3; dark matter must have spin 1/2 and interact with nucleons through a unique momentum-dependent operator. We therefore conclude that the observation of O(100) signal events at XENONnT combined with the detection, or the lack of detection, of a monojet signal at the LHC Run 3 would significantly narrow the range of possible dark matter-nucleon interactions. As we argued above, it can also provide key information on the dark matter particle spin.

  • 6.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Catena, Riccardo
    Krauss, Martin B.
    Impact of a XENONnT signal on LHC dijet searches2019Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 7, artikkel-id 015Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is well-known that dark matter (DM) direct detection experiments and the LHC are complementary, since they probe physical processes occurring at different energy scales. And yet, there are aspects of this complementarity which are still not fully understood, or exploited. For example, what is the impact that the discovery of DM at XENONnT would have on present and future searches for DM in LHC final states involving a pair of hadronic jets? In this work we investigate the impact of a XENONnT signal on the interpretation of current dijet searches at the LHC, and on the prospects for dijet signal discovery at the High-Luminosity (HL) LHC in the framework of simplified models. Specifically, we focus on a general class of simplified models where DM can have spin 0, 1/2 or 1, and interacts with quarks through the exchange of a scalar, pseudo-scalar, vector, or pseudo-vector mediator. We find that exclusion limits on the mediator's mass and its coupling to quarks from dijet searches at the LHC are significantly affected by a signal at XENONnT, and that O(100) signal events at XENONnT would drastically narrow the region in the parameter space of simplified models where a dijet signal can be discovered at 5 sigma C.L. at the HL-LHC.

  • 7.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Drukier, Andrzej K.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). University of Michigan, USA.
    Górski, Maciej
    Stengel, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Searching for Dark Matter with Paleo-DetectorsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A large experimental program is underway to extend the sensitivity of direct detection experiments, searching for interactions of Dark Matter with nuclei, down to the neutrino floor. However, such experiments are becoming increasingly difficult and costly due to the large target masses and exquisite background rejection needed for the necessary improvements in sensitivity. We investigate an alternative approach to the detection of Dark Matter--nucleon interactions: Searching for the persistent traces left by Dark Matter scattering in ancient minerals obtained from much deeper than current underground laboratories. We estimate the sensitivity of paleo-detectors, which extends far beyond current upper limits for a wide range of Dark Matter masses.

  • 8.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Kelso, Chris
    Dark Matter implications of DAMA/LIBRA-phase2 results2019Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 789, s. 262-269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, the DAMA/LIBRA collaboration released updated results from their search for the annual modulation signal from Dark Matter (DM) scattering in the detector. Besides approximately doubling the exposure of the DAMA/LIBRA data set, the updated photomultiplier tubes of the experiment allow a lower recoil energy threshold of I keV electron equivalent compared to the previous threshold of 2 keV electron equivalent. We study the compatibility of the observed modulation signal with DM scattering. Due to a conspiracy of multiple effects, the new data at low recoil energies is very powerful for testing the DM hypothesis. We find that canonical (isospin conserving) spin-independent DM-nucleon interactions are no longer a good fit to the observed modulation signal in the standard halo model. The canonical spin independent case is disfavored by the new data, with best fit points of a DM mass of similar to 8 GeV, disfavored by 5.2 sigma, or a mass of similar to 54GeV, disfavored by 2.5 sigma. Allowing for isospin violating spin independent interactions, we find a region with a good fit to the data with suppressed effective couplings to iodine for DM masses of similar to 10 GeV. We also consider spin-dependent DM-nucleon interactions, which yield good fits for similar DM masses of similar to 10 GeV or similar to 45 GeV.

  • 9.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). University of Michigan, USA.
    Shah, Nausheen R.
    Shakya, Bibhushan
    NMSSM Higgs boson search strategies at the LHC and the mono-Higgs signature in particular2017Inngår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, nr 11, artikkel-id 115036Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the collider phenomenology of the extended Higgs sector of the next-to-minimal supersymmetric Standard Model (NMSSM). The region of NMSSM parameter space favored by a 125 GeV SM-like Higgs and naturalness generically features a light Higgs and neutralino spectrum as well as a large O(1) coupling between the Higgs doublets and the NMSSM singlet fields. In such regimes, the heavier Higgs bosons can decay dominantly into lighter Higgs bosons and neutralinos. We study the prospects of observing such decays at the 13 TeV LHC, focusing on mono-Higgs signatures as probes of such regions of parameter space. We present results for the mono-Higgs reach in a framework easily applicable to other models featuring similar decay topologies. In the NMSSM, we find that the mono-Higgs channel can probe TeV scale Higgs bosons and has sensitivity even in the low tan beta, large m(A) regime that is difficult to probe in the MSSM. Unlike for many conventional Higgs searches, the reach of the mono-Higgs channel will improve significantly with the increased luminosity expected to be collected at the LHC in the ongoing and upcoming runs.

  • 10.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Shah, Nausheen R.
    Two Higgs doublets and a complex singlet: disentangling the decay topologies and associated phenomenology2018Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 12, artikkel-id 044Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a systematic study of an extension of the Standard Model (SM) with two Higgs doublets and one complex singlet (2HDM+S). In order to gain analytical understanding of the parameter space, we re-parameterize the 27 parameters in the Lagrangian by quantities more closely related to physical observables: physical masses, mixing angles, trilinear and quadratic couplings, and vacuum expectation values. Embedding the 125 GeV SM-like Higgs boson observed at the LHC places stringent constraints on the parameter space. In particular, the mixing of the SM-like interaction state with the remaining states is severely constrained, requiring approximate alignment without decoupling in the region of parameter space where the additional Higgs bosons are light enough to be accessible at the LHC. In contrast to 2HDM models, large branching ratios of the heavy Higgs bosons into two lighter Higgs bosons or a light Higgs and a Z boson, so-called Higgs cascade decays, are ubiquitous in the 2HDM+S. Using currently available limits, future projections, and our own collider simulations, we show that combining different final states arising from Higgs cascades would allow to probe most of the interesting region of parameter space with Higgs boson masses up to 1 TeV at the LHC with L = 3000 fb(-1) of data.

  • 11.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Shah, Nausheen R.
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). University of Michigan, U.S.A..
    The NMSSM is within reach of the LHC: mass correlations & decay signatures2019Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, artikkel-id 011Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Next-to-Minimal Supersymmetric Standard Model (NMSSM), the singlet extension of the MSSM which fixes many of the MSSM's shortcomings, is shown to be within reach of the upcoming runs of the Large Hadron Collider (LHC). A systematic treatment of the various Higgs decay channels and their interplay has been lacking due to the seemingly large number of free parameters in the NMSSM's Higgs sector. We demonstrate that due to the SM-like nature of the observed Higgs boson, the NMSSM's Higgs and neutralino sectors have highly correlated masses and couplings and can effectively be described by four physically intuitive parameters: the physical masses of the two CP-odd states and their mixing angle, and tan , which plays a minor role. The heavy Higgs bosons in the NMSSM have large branching ratios into pairs of lighter Higgs bosons or a light Higgs and a Z boson. Search channels arising via these Higgs cascades are unique to models like the NMSSM with a Higgs sector larger than that of the MSSM. In order to cover as much of the NMSSM parameter space as possible, one must combine conventional search strategies employing decays of the additional Higgs bosons into pairs of SM particles with Higgs cascade channels. We demonstrate that such a combination would allow a significant fraction of the viable NMSSM parameter space containing additional Higgs bosons with masses below 1 TeV to be probed at future runs of the LHC.

  • 12.
    Baum, Sebastian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Visinelli, Luca
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). University of Helsinki, Finland.
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). University of Michigan, USA.
    Stengel, Patrick
    Dark matter capture, subdominant WIMPs, and neutrino observatories2017Inngår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, nr 4, artikkel-id 043007Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Weakly interacting massive particles (WIMPs), which are among the best motivated dark matter (DM) candidates, could make up all or only a fraction of the total DM budget. We consider a scenario in which WIMPs are a subdominant DM component; such a scenario would affect both current direct and indirect bounds on the WIMP-nucleon scattering cross section. In this paper we focus on indirect searches for the neutrino flux produced by annihilation of subdominant WIMPs captured by the Sun or the Earth via either spin-dependent or spin-independent scattering. We derive the annihilation rate and the expected neutrino flux at neutrino observatories. In our computation, we include an updated chemical composition of the Earth with respect to the previous literature, leading to an increase of the Earth's capture rate for spin-dependent scattering by a factor of 3. Results are compared with current bounds from Super-Kamiokande and IceCube. We discuss the scaling of bounds from both direct and indirect detection methods with the WIMP abundance.

  • 13. Cuendis, S. Arguedas
    et al.
    Baier, J.
    Barth, K.
    Baum, Sebastian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Bayirli, A.
    Belov, A.
    Braeuninger, H.
    Cantatore, G.
    Carmona, J. M.
    Castel, J. F.
    Cetin, S. A.
    Dafni, T.
    Davenport, M.
    Dermenev, A.
    Desch, K.
    Dobrich, B.
    Fischer, H.
    Funk, W. g
    Garcia, J. A.
    Gardikiotis, A.
    Garza, J. G.
    Gninenko, S.
    Hasinoff, M. D.
    Hoffmann, D. H. H.
    Iguaz, F. J.
    Irastorza, I. G.
    Jakovcic, K.
    Kaminski, J.
    Karuza, M.
    Krieger, C.
    Lakic, B.
    Laurent, J. M.
    Luzon, G.
    Maroudas, M.
    Miceli, L.
    Neff, S.
    Ortega, I.
    Ozbey, A.
    Pivovaroff, M. J.
    Rosu, M.
    Ruz, J.
    Ruiz Choliz, E.
    Schmidt, S.
    Schumann, M.
    Semertzidis, Y. K.
    Solanki, S. K.
    Stewart, L.
    Tsagris, I.
    Vafeiadis, T.
    Vogel, J. K.
    Vretenar, M.
    Yildiz, S. C.
    Zioutas, K.
    First results on the search for chameleons with the KWISP detector at CAST2019Inngår i: Physics of the Dark Universe, ISSN 0953-8585, E-ISSN 2212-6864, Vol. 26, artikkel-id 100367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a first measurement with a sensitive opto-mechanical force sensor designed for the direct detection of coupling of real chameleons to matter. These dark energy candidates could be produced in the Sun and stream unimpeded to Earth. The KWISP detector installed on the CAST axion search experiment at CERN looks for tiny displacements of a thin membrane caused by the mechanical effect of solar chameleons. The displacements are detected by a Michelson interferometer with a homodyne readout scheme. The sensor benefits from the focusing action of the ABRIXAS X-ray telescope installed at CAST, which increases the chameleon flux on the membrane. A mechanical chopper placed between the telescope output and the detector modulates the incoming chameleon stream. We present the results of the solar chameleon measurements taken at CAST in July 2017, setting an upper bound on the force acting on the membrane of 80 pN at 95% confidence level. The detector is sensitive for direct coupling to matter 104 <= beta(m) <= 108, where the coupling to photons is locally bound to beta(gamma) <= 10(11).

  • 14.
    Drukier, Andrzej K.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Baum, Sebastian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). University of Michigan, USA.
    Górski, Maciej
    Stengel, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Paleo-detectors: Searching for Dark Matter with Ancient Minerals2019Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 99, nr 4, artikkel-id 043014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We explore paleo-detectors as an approach to the direct detection of weakly interacting massive particle (WIMP) dark matter radically different from conventional detectors. Instead of instrumenting a (large) target mass in a laboratory in order to observe WIMP-induced nuclear recoils in real time, the approach is to examine ancient minerals for traces of WIMP-nucleus interactions recorded over timescales as large as 1 Gyr. Here, we discuss the paleo-detector proposal in detail, including background sources and possible target materials. In order to suppress backgrounds induced by radioactive contaminants such as uranium, we propose to use minerals found in marine evaporites or in ultrabasic rocks. We estimate the sensitivity of paleo-detectors to spin-independent and spin-dependent WIMP-nucleus interactions. The sensitivity to low-mass WIMPs with masses mχ≲10  GeV extends to WIMP-nucleon cross sections many orders of magnitude smaller than current upper limits. For heavier WIMPs with masses mχ≳30  GeV cross sections a factor of a few to ∼100 smaller than current upper limits can be probed by paleo-detectors.

  • 15. Edwards, Thomas D. P.
    et al.
    Kavanagh, Bradley J.
    Weniger, Christoph
    Baum, Sebastian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Drukier, Andrzej K.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). University of Michigan, USA.
    Górski, Maciej
    Stengel, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Digging for dark matter: Spectral analysis and discovery potential of paleo-detectors2019Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 99, nr 4, artikkel-id 043541Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Paleo-detectors are a recently proposed method for the direct detection of dark matter (DM). In such detectors, one would search for the persistent damage features left by DM–nucleus interactions in ancient minerals. Initial sensitivity projections have shown that paleo-detectors could probe much of the remaining weakly interacting massive particle (WIMP) parameter space. In this paper, we improve upon the cut-and-count approach previously used to estimate the sensitivity by performing a full spectral analysis of the background- and DM-induced signal spectra. We consider two scenarios for the systematic errors on the background spectra: (i) systematic errors on the normalization only, and (ii) systematic errors on the shape of the backgrounds. We find that the projected sensitivity is rather robust to imperfect knowledge of the backgrounds. Finally, we study how well the parameters of the true WIMP model could be reconstructed in the hypothetical case of a WIMP discovery.

  • 16.
    Visinelli, Luca
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Baum, Sebastian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Redondo, Javier
    Freese, Katherine
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). University of Michigan, USA.
    Wilczek, Frank
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Center for Theoretical Physics, MIT, USA.
    Dilute and dense axion stars2018Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 777, s. 64-72Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

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