CETUP* 2013

Preprints


  • Isospin-Violating Dark Matter Benchmarks for Snowmass 2013
    • Abstract: Isospin-violating dark matter (IVDM) generalizes the standard spin-independent scattering parameter space by introducing one additional parameter, the neutron-to-proton coupling ratio f_n/f_p. In IVDM the implications of direct detection experiments can be altered significantly. We review the motivations for considering IVDM and present benchmark models that illustrate some of the qualitatively different possibilities. IVDM strongly motivates the use of a variety of target nuclei in direct detection experiments.
    • Contributors: Jason Kumar, Jonathan L. Feng, Danny Marfatia and David Sanford
    • Preprint Number: CETUP2013-001
  • Phenomenology of Dirac Neutralino Dark Matter
    • Contributors: Matthew R. Buckley, Dan Hooper and Jason Kumar
    • Preprint Number: CETUP2013-002
  • Non-thermal Dark Matter in String Compacti fications
    • Contributors: Rouzbeh Allahverdi, Michele Cicoli, Bhaskar Dutta, Kuver Sinha
    • Preprint Number: CETUP2013-003
  • Lowering the Threshold in the DAMA Dark Matter Search
    • Abstract: The DAMA experiment searches for Weakly Interacting Massive Particle (WIMP) dark matter via its expected but rare interactions within the detector, where the interaction rates will modulate throughout the year due to the orbital motion of the Earth. Over the course of more than 10 years of operation, DAMA has indeed detected a strong modulation in the event rate above the detector threshold of 2 keVee. Under standard assumptions regarding the dark matter halo and WIMP interactions, this signal is consistent with that expected of WIMPs of two different approximate masses: ~10 GeV and ~70 GeV. We examine how a lower threshold, allowed by recent upgrades to the DAMA detector, may shed light on this situation. We find that the lower threshold data should rule out one of the two mass ranges in the spin-independent case at a minimum of the 2.6-sigma level in the worst case scenario. It is unlikely, however, that the data will discriminate between spin-independent and spin-dependent interactions, although for some particular measurements of the modulation in the lowest energy bins this could be achieved. Our findings illustrate the importance of a low threshold in modulation searches.
    • Contributors: Chris Kelso, Pearl Sandick and Christopher Savage
    • Preprint Number: CETUP2013-004
  • Cosmic Variance of the Spectral Index from Mode Coupling
    • Abstract: We demonstrate that local, scale-dependent non-Gaussianity can generate cosmic variance uncertainty in the observed spectral index of primordial curvature perturbations. In a universe much larger than our current Hubble volume, locally unobservable long wavelength modes can induce a scale-dependence in the power spectrum of typical subvolumes, so that the observed spectral index varies at a cosmologically significant level (|Delta n_s| ~ O(0.04)). Similarly, we show that the observed bispectrum can have an induced scale dependence that varies about the global shape. If tensor modes are coupled to long wavelength modes of a second field, the locally observed tensor power and spectral index can also vary. All of these effects, which can be introduced in models where the observed non-Gaussianity is consistent with bounds from the {\it Planck} satellite, loosen the constraints that observations place on the parameters of theories of inflation with mode coupling. We suggest observational constraints that future measurements could aim for to close this window of cosmic variance uncertainty.
    • Contributors: Joseph Bramante, Jason Kumar, Elliot Nelson and Sarah Shandera
    • Preprint Number: CETUP2013-005
  • LHC Phenomenology of SO(10) models with Yukawa Unification
    • Contributors: A. Anandakrishnan, B. Bryant, S. Raby and A. Wingerter
    • Preprint Number: CETUP2013-006
  • Unified framework for matter and dark matter
    • Abstract: Dark matter may be stable in the same way that the proton is stable. This hints at the possibility of a grand unified theory incorporating both matter and dark matter. A simplest example is discussed with a natural application to the radiative (scotogenic) generation of neutrino mass.
    • Contributors: Ernest Ma
    • Preprint Number: CETUP2013-007
  • On sbottom resonances in Dark Matter scattering
    • Abstract: A resonance in the neutralino-nucleus elastic scattering cross section is usually purported when the neutralino-sbottom mass difference ms-mx is equal to the bottom quark mass mb~4 GeV. Such a scenario has been discussed as a viable model for light (~10 GeV) neutralino dark matter as explanation of possible DAMA and CoGeNT direct detection signals. Here we give physical and analytical arguments showing that the sbottom resonance may actually not be there. In particular, we show analytically that the one-loop gluon-neutralino scattering amplitude has no pole at ms=mx+mb, while by analytic continuation to the regime ms less than mx, it develops a pole at ms=mx-mb. In the limit of vanishing gluon momenta, this pole corresponds to the only cut of the neutralino self-energy diagram with a quark and a squark running in the loop, when the decay process x to s+b becomes kinematically allowed. The pole can be interpreted as the formation of a sbqqq resonant state (where qqq are the nucleon valence quarks), which is however kinematically not accessible if the neutralino is the LSP. Our analysis shows that the common practice of estimating the neutralino-nucleon cross section by introducing an ad-hoc pole at ms=mx+mb into the effective four-fermion interaction (also including higher-twist effects) should be discouraged, since it corresponds to adding a spurious pole to the scattering process at the center-of-mass energy ms=mb. Our considerations can be extended from the specific case of supersymmetry to other similar cases in which the dark matter particle scatters off nucleons through the exchange of a b-flavored state almost degenerate in mass with the dark matter particle, such as for instance in theories with extra dimensions and in other mass-degenerate dark matter scenarios recently discussed in the literature.
    • Contributors: Paolo Gondolo, Stefano Scopel
    • Preprint Number: CETUP2013-008
  • Sparticle Spectroscopy from SO(10) GUT with a Unified Higgs Sector
    • Abstract: We study the low energy implications, especially the particle spectroscopy, of SO(10) grand unification in which the SO(10) symmetry is broken to the Standard Model gauge group with a single pair of $(144+\overline{144})$ dimensional Higgs multiplet (unified Higgs sector). In this class of models, the asymptotic relation $Y_b\approx Y_{\tau}\approx Y_t/6$ among the third generation quark and lepton Yukawa couplings can be derived. This relation leads to the prediction $\tan\beta \approx 14$, where $\tan\beta$ is the well known MSSM parameter. We find that this type of Yukawa coupling unification {(YU) is realized only by employing non-universal soft supersymmety breaking terms, dictated by SO(10) symmetry, for the gauginos. A 125 GeV Higgs boson mass is also found to be consistent with YU at the $\sim 5\%$ level. Without imposing a constraint on the relic abundance of dark matter in these models, the squark and slepton masses, with the exception of the stop, exceed 2 TeV and the gluino is heavier than 1 TeV. We show that the neutralino in this model is an acceptable dark mater candidate through the neutralino-stop coannihilation scenario, with the stop quark being relatively light ($\gtrsim 500$ GeV)}.
    • Contributors: M. Adeel Ajaib, Ilia Gogoladze and Qaisar Shafi
    • Preprint Number: CETUP2013-009
  • On baryogenesis from dark matter annihilation
    • Abstract: We study in detail the conditions to generate the baryon asymmetry of the Universe from the annihilation of dark matter. This scenario requires a low energy mechanism for thermal baryogenesis, hence we first discuss some of these mechanisms together with the specific constraints due to the connection with the dark matter sector. Then we show that, contrary to what stated in previous studies, it is possible to generate the cosmological asymmetry without adding a light sterile dark sector, both in models with violation and with conservation of $B-L$. In addition, one of the models we propose yields some connection to neutrino masses.
    • Contributors: Nicolas Bernal, Stefano Colucci, Francois-Xavier Josse-Michaux, J. Racker, Lorenzo Ubaldi
    • Preprint Number: CETUP2013-010
  • Dipole Moment Bounds on Dark Matter Annihilation
    • Abstract: We consider constraints on simplified models in which scalar dark matter annihilates to light charged leptons through the exchange of charged mediators. We find that loop diagrams will contribute corrections to the magnetic and electric dipole moments of the light charged leptons, and experimental constraints on these corrections place significant bounds on the dark matter annihilation cross section. In particular, annihilation to electrons with an observable cross section would be ruled out, while annihilation to muons is only permitted if the dominant contributions arise from CP-violating interactions.
    • Contributors: Keita Fukushima and Jason Kumar
    • Preprint Number: CETUP2013-011
  • Constraining the $Z^{\prime}$ Mass in 331 Models using Direct Dark Matter Detection
    • Abstract: We investigate a 331 extension of the Standard Model gauge sector which accommodates neutrino masses and where the lightest of the heavy neutrinos is a viable WIMP dark matter candidate. In this model, processes mediated by the additional $Z^{\prime}$ gauge boson set both the WIMP relic abundance and the scattering cross section of WIMPs off of nuclei. We calculate the WIMP relic abundance including the important effect of coannihilation across the heavy neutrino sector. We find that the recent XENON results put very stringent bounds on the mass of the extra gauge boson, $M_{Z^{\prime}} > 1.6$~TeV, for WIMPs lighter than 1~TeV. Finally, we comment on how our bounds on the $Z^{\prime}$ mass impact generic 331-like models and on implications for LHC phenomenology.
    • Contributors: Stefano Profumo and Farinaldo S. Queiroz
    • Preprint Number: CETUP2013-012
  • SU(5) x SU(5) Twinification And D2 Parity
    • Contributors: Zurab Tavartkiladze
    • Preprint Number: CETUP2013-013
  • A 331 WIMPy Dark Radiation Model
    • Abstract: Recent observations suggest that the number of relativistic degrees of freedom in the early universe might exceed what predicted in the standard cosmological model. If even a small, percent-level fraction of dark matter particles are produced relativistically, they could mimic the effect of an extra realistic species at matter-radiation equality while obeying BBN, CMB and Structure Formation bounds. We show that this scenario is quite naturally realized with a weak-scale dark matter particle and a high-scale ``mother' particle within a well motivated 3-3-1 gauge model, which is particularly interesting for being consistent with electroweak precision measurements, with recent LHC results, and for offering a convincing explanation for the number of generations in the Standard Model.
    • Contributors: Chris Kelso,C. A. de S. Pires,Stefano Profumo,Farinaldo S. Queiroz and P. S. Rodrigues da Silva
    • Preprint Number: CETUP2013-014
  • WIMPy Leptogenesis With Absorptive Final State Interactions
    • Contributors: Jason Kumar and Patrick Stengel
    • Preprint Number: CETUP2013-015
  • Higgs phenomenology in Type-I 2HDM with $\bm{U(1)_H}$ Higgs gauge symmetry
    • Contributors: P. Ko, Yuji Omura and Chaehyun Yu
    • Preprint Number: CETUP2013-016
  • Supernova Constraints on MeV Dark Sectors from e+e− Annihilations
    • Abstract: Theories with dark forces and dark sectors are of interest for dark matter models. In this paper we find the region in parameter space that is constrained by supernova cooling constraints when the models include dark sector particles with masses around 100 MeV or less. We include only interactions with electrons and positrons. The constraint is important for small mixing parameters.
    • Contributors: Herbert Dreiner, Jean-Francois Fortin, Christoph Hanhart, and Lorenzo Ubaldi
    • Preprint Number: CETUP2013-017
  • Direct Detection Portals for Self-interacting Dark Matter
    • Abstract: Dark matter self-interactions can affect the small scale structure of the Universe, reducing the central densities of dwarfs and low surface brightness galaxies in accord with observations. From a particle physics point of view, this points toward the existence of a 1 - 100 MeV particle in the dark sector that mediates self-interactions. Since mediator particles will generically couple to the Standard Model, direct detection experiments provide sensitive probes of self-interacting dark matter. We consider three minimal mechanisms for coupling the dark and visible sectors: photon kinetic mixing, Z boson mass mixing, and the Higgs portal. Self-interacting dark matter motivates a new benchmark paradigm for direct detection via momentum-dependent interactions, and ton-scale experiments will cover astrophysically motivated parameter regimes that are unconstrained by current limits. Direct detection is a complementary avenue to constrain velocity-dependent self-interactions that evade astrophysical bounds from large scales, such as the Bullet cluster.
    • Contributors: Manoj Kaplinghat, Sean Tulin, and Hai-Bo Yu
    • Preprint Number: CETUP2013-018
  • Towards the minimal renormalizable supersymmetric $E_6$ model
    • Abstract: We find an explicit renormalizable supersymmetric E6 model with all the ingredients for being realistic. It consists of the Higgs sector 351prime+ 351primebar+27+ 27bar, which breaks E6 directly to the Standard Model gauge group. Three copies of 27 dimensional representations then describe the matter sector, while an extra 27+27bar pair is needed to successfully split the Standard Model Higgs doublet from the heavy Higgs triplet. Also, we show why some other simpler E6 models fail to be realistic at the renormalizable level.
    • Contributors: Borut Bajc and Vasja Susic
    • Preprint Number: CETUP2013-019
  • Matter-Neutrino Resonance Above Merging Compact Objects
    • Abstract: Accretion disks arising from neutron star- neutron star mergers or black hole- neutron star merg- ers, produce large numbers of neutrinos and antineutrinos. In contrast to other astrophysical sce- narios, like supernovae, in mergers the antineutrinos outnumber the neutrinos. This antineutrino dominance gives neutrinos from merger disks the opportunity to exhibit new oscillation physics, ie, a matter-neutrino resonance. We explore this resonance, finding that consequences can be a large transition of νe to other flavors. We present numerical calculations of neutrinos from merger disks and compare with a single energy model. We explain both the basic features and the conditions for a transition.
    • Contributors: A. Malkus , A. Friedland, and G. C. McLaughlin
    • Preprint Number: CETUP2013-020