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  • 1.
    Baum, Sebastian
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden.;Stockholm Univ, Roslagstullsbacken 23, S-10691 Stockholm, Sweden..
    Freese, Katherine
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden.; Stockholm Univ, Roslagstullsbacken 23, S-10691 Stockholm, Sweden.;Univ Michigan, Dept Phys, Leinweber Ctr Theoret Phys, Ann Arbor, MI 48109 USA..
    Kelso, Chris
    Univ North Florida, Dept Phys, Jacksonville, FL 32224 USA..
    Dark Matter implications of DAMA/LIBRA-phase2 results2019Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 789, s. 262-269Artikel i tidskrift (Refereegranskat)
    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. Elsevier B.V.

  • 2.
    Baum, Sebastian
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Freese, Katherine
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. University of Michigan, United States; Stockholm University, Sweden.
    Shah, N. R.
    Shakya, B.
    NMSSM Higgs boson search strategies at the LHC and the mono-Higgs signature in particular2017Ingår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, nr 11, artikel-id 115036Artikel i tidskrift (Refereegranskat)
    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 tanβ, large mA 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.

  • 3.
    Baum, Sebastian
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Oskar Klein Ctr Cosmoparticle Phys, Dept Phys, Alba Nova, S-10691 Stockholm, Sweden; Stockholm Univ, Roslagstullsbacken 23, S-10691 Stockholm, Sweden.
    Shah, Nausheen R.
    Wayne State Univ, Dept Phys & Astron, Detroit, MI 48201 USA..
    Freese, Katherine
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Oskar Klein Ctr Cosmoparticle Phys, Dept Phys, Alba Nova, S-10691 Stockholm, Sweden.; Stockholm Univ, Roslagstullsbacken 23, S-10691 Stockholm, Sweden; Univ Michigan, Leinweber Ctr Theoret Phys, Dept Phys, Ann Arbor, MI 48109 USA.
    The NMSSM is within reach of the LHC: mass correlations & decay signatures2019Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, artikel-id 011Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Baum, Sebastian
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Visinelli, Luca
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Freese, Katherine
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Stengel, Patrick
    Dark matter capture, subdominant WIMPs, and neutrino observatories2017Ingår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, nr 4, artikel-id 043007Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Drukier, Andrzej K.
    et al.
    Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, Alba Nova, S-10691 Stockholm, Sweden..
    Baum, Sebastian
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, Alba Nova, S-10691 Stockholm, Sweden ; .
    Freese, Katherine
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, Alba Nova, S-10691 Stockholm, Sweden ; Univ Michigan, Leinweber Ctr Theoret Phys, Ann Arbor, MI 48109 USA.
    Gorski, Maciej
    Natl Ctr Nucl Res, PL-05400 Otwock, Swierk, Poland..
    Stengel, Patrick
    Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, Alba Nova, S-10691 Stockholm, Sweden..
    Paleo-detectors: Searching for dark matter with ancient minerals2019Ingår i: PHYSICAL REVIEW D, Vol. 99, nr 4, artikel-id 043014Artikel i tidskrift (Refereegranskat)
    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 m(chi) less than or similar to 10 GeV extends to WIMP-nucleon cross sections many orders of magnitude smaller than current upper limits. For heavier WIMPs with masses m(z) greater than or similar to 30 GeV cross sections a factor of a few to similar to 100 smaller than current upper limits can be probed by paleo-detectors.

  • 6.
    Edwards, Thomas D. P.
    et al.
    Univ Amsterdam, Inst Theoret Phys Amsterdam, Gravitat Astroparticle Phys Amsterdam GRAPPA, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands.;Univ Amsterdam, Delta Inst Theoret Phys, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands..
    Kavanagh, Bradley J.
    Univ Amsterdam, Inst Theoret Phys Amsterdam, Gravitat Astroparticle Phys Amsterdam GRAPPA, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands.;Univ Amsterdam, Delta Inst Theoret Phys, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands..
    Weniger, Christoph
    Univ Amsterdam, Inst Theoret Phys Amsterdam, Gravitat Astroparticle Phys Amsterdam GRAPPA, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands.;Univ Amsterdam, Delta Inst Theoret Phys, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands..
    Baum, Sebastian
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden ; Stockholm Univ, Roslagstullsbacken 23, S-10691 Stockholm, Sweden.
    Drukier, Andrzej K.
    Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden..
    Freese, Katherine
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden ; Stockholm Univ, Roslagstullsbacken 23, S-10691 Stockholm, Sweden ; Univ Michigan, Leinweber Ctr Theoret Phys, Ann Arbor, MI 48109 USA.
    Gorski, Maciej
    Natl Ctr Nucl Res, PL-05400 Otwock, Swierk, Poland..
    Stengel, Patrick
    Stockholm Univ, Dept Phys, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden..
    Digging for dark matter: Spectral analysis and discovery potential of paleo-detectors2019Ingår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 99, nr 4, artikel-id 043541Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    Freese, Katherine
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Lopez, Alejandro
    Shah, Nausheen R.
    Shakya, Bibhushan
    MSSM A-funnel and the galactic center excess: prospects for the LHC and direct detection experiments2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, artikel-id 059Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The pseudoscalar resonance or "A-funnel" in the Minimal Supersymmetric Standard Model (MSSM) is a widely studied framework for explaining dark matter that can yield interesting indirect detection and collider signals. The well-known Galactic Center excess (GCE) at GeV energies in the gamma ray spectrum, consistent with annihilation of a less than or similar to 40 GeV dark matter particle, has more recently been shown to be compatible with significantly heavier masses following reanalysis of the background. In this paper, we explore the LHC and direct detection implications of interpreting the GCE in this extended mass window within the MSSM A-funnel framework. We find that compatibility with relic density, signal strength, collider constraints, and Higgs data can be simultaneously achieved with appropriate parameter choices. The compatible regions give very sharp predictions of 200-600 GeV CP-odd/even Higgs bosons at low tan beta at the LHC and spin-independent cross sections approximate to 10(-11) pb at direct detection experiments. Regardless of consistency with the GCE, this study serves as a useful template of the strong correlations between indirect, direct, and LHC signatures of the MSSM A-funnel region.

  • 8.
    Freese, Katherine
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. University of Stockholm, Sweden.
    Rindler-Daller, Tanja
    Spolyar, Douglas
    Valluri, Monica
    Dark stars: a review2016Ingår i: Reports on progress in physics (Print), ISSN 0034-4885, E-ISSN 1361-6633, Vol. 79, nr 6, artikel-id 066902Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only <= 0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (similar to 10 AU) and cool (surface temperatures similar to 10 000 K) objects. We follow the evolution of dark stars from their inception at similar to 1M(circle dot) as they accrete mass from their surroundings to become supermassive stars, some even reaching masses >10(6)M(circle dot) and luminosities >10(10)L(circle dot), making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.

  • 9. Kelso, Chris
    et al.
    Savage, Christopher
    Valluri, Monica
    Freese, Katherine
    Stinson, Gregory S.
    Bailin, Jeremy
    The impact of baryons on the direct detection of dark matter2016Ingår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, nr 8, artikel-id 071Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spatial and velocity distributions of dark matter particles in the Milky Way Halo affect the signals expected to be observed in searches for dark matter. Results from direct detection experiments are often analyzed assuming a simple isothermal distribution of dark matter, the Standard Halo Model (SHM). Yet there has been skepticism regarding the validity of this simple model due to the complicated gravitational collapse and merger history of actual galaxies. In this paper we compare the SHM to the results of cosmological hydrodynamical simulations of galaxy formation to investigate whether or not the SHM is a good representation of the true WIMP distribution in the analysis of direct detection data. We examine two Milky Way-like galaxies from the MaGICC cosmological simulations (a) with dark matter only and (b) with baryonic physics included. The inclusion of baryons drives the shape of the DM halo to become more spherical and makes the velocity distribution of dark matter particles less anisotropic especially at large heliocentric velocities, thereby making the SHM a better fit. We also note that we do not find a significant disk-like rotating dark matter component in either of the two galaxy halos with baryons that we examine, suggesting that dark disks are not a generic prediction of cosmological hydrodynamical simulations. We conclude that in the Solar neighborhood, the SHM is in fact a good approximation to the true dark matter distribution in these cosmological simulations (with baryons) which are reasonable representations of the Milky Way, and hence can also be used for the purpose of dark matter direct detection calculations.

  • 10. Scaffidi, Andre
    et al.
    Freese, Katherine
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Li, Jinmian
    Savage, Christopher
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    White, Martin
    Williams, Anthony G.
    Gamma rays from muons from WIMPs: Implementation of radiative muon decays for dark matter analyses2016Ingår i: Physical Review D, ISSN 2470-0010, Vol. 93, nr 11, artikel-id 115024Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dark matter searches in gamma ray final states often make use of the fact that photons can be produced from final state muons. Modern Monte Carlo generators and dark matter codes include the effects of final state radiation from muons produced in the dark matter annihilation process itself, but neglect the O(1%) radiative correction that arises from the subsequent muon decay. After implementing this correction we demonstrate the effect that it can have on dark matter phenomenology by considering the case of dark matter annihilation to four muons via scalar mediator production. We first show that the AMS-02 positron excess can no longer easily be made consistent with this final state once the Fermi-LAT dwarf limits are calculated with the inclusion of radiative muon decays, and we next show that the Fermi-LAT galactic center gamma excess can be improved with this final state after inclusion of the same effect. We provide code and tables for the implementation of this effect in the popular dark matter code micrOMEGAs, providing a solution for any model producing final state muons.

  • 11. Visinelli, Luca
    et al.
    Baum, Sebastian
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholms universitet, Sverige.
    Redondo, Javier
    Freese, Katherine
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholms universitet, Sverige.
    Wilczek, Frank
    Dilute and dense axion stars2018Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 777, s. 64-72Artikel i tidskrift (Refereegranskat)
    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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