118736479
Direct detection with dark mediators
We introduce dark mediator Dark matter (dmDM) where the dark and visible sectors are connected by at least one light mediator carrying the same dark charge that stabilizes DM. is coupled to the Standard Model via an operator qq =, and to dark matter via a Yukawa coupling y c . Direct detection is
119118716
Induced electroweak symmetry breaking and supersymmetric naturalness
In this paper we study a new class of supersymmetric models that can explain a 125 GeV Higgs without fine-tuning. These models contain additional `auxiliary Higgs' fields with large tree-level quartic interaction terms but no Yukawa couplings. These have electroweak-breaking vacuum expectation values, and contribute to the VEVs of the MSSM Higgs fields either through an induced quartic or through an induced tadpole. The quartic interactions for the auxiliary Higgs fields can arise from either D-terms or F-terms. The tadpole mechanism has been previously studied in strongly-coupled models with large D-terms, referred to as `superconformal technicolor.' The perturbative models studied here preserve gauge coupling unification in the simplest possible way, namely that all new fields are in complete SU(5) multiplets. The models are consistent with the observed properties of the 125 GeV Higgs-like boson as well as precision electroweak constraints, and predict a rich phenomenology of new Higgs states at the weak scale. The tuning is less than 10% in almost all of the phenomenologically allowed parameter space. If electroweak symmetry is broken by an induced tadpole, the cubic and quartic Higgs self-couplings are significantly smaller than in the standard model.
119232932
Leptogenesis with composite neutrinos
Models with composite singlet neutrinos can give small Majorana or Dirac masses to the active neutrinos. The mechanism is based on the fact that conserved chiral symmetries give massless neutrinos at the renormalizable level. Thus, they acquire very small masses due to non-renormalizable terms. We investigate such models in two aspects. First, we find UV completions for them and then we investigate the possibility of giving leptogenesis. We find that these models offer new possibilities for leptogenesis. Models with Majorana masses can exhibit standard leptogenesis. Models with Dirac masses can provide a realization of Dirac type leptogenesis with mass scale that can be as low as 10 TeV.
55446956
Missing energy signatures of dark matter at the LHC
We use ATLAS and CMS searches in the mono-jet + missing energy and mono-photon + missing energy final state to set limits on the couplings of dark matter to quarks and gluons. Working in an effective field theory framework we compare several existing mono-jet analyses and find that searches with high p_T cuts are more sensitive to dark matter. We constrain the suppression scale of the effective dark matter-Standard Model interactions, and convert these limits into bounds on the cross sections relevant to direct and indirect detection. We find that, for certain types of operators, in particular spin-independent dark matter-gluon couplings and spin-dependent dark matter-quark couplings, LHC constraints from the mono-jet channel are competitive with, or superior to, limits from direct searches up to dark matter masses of order 1 TeV. Comparing to indirect searches, we exclude, at 90% C.L., dark matter annihilating to quarks with the annihilation cross section of a thermal relic for masses below ~ 15-70 GeV, depending on the Lorentz structure of the effective couplings. Mono-photon limits are somewhat weaker than mono-jet bounds, but still provide an important cross check in the case of a discovery in mono-jets. We also discuss the possibility that dark matter--Standard Model interactions at LHC energies cannot be described by effective operators, in which case we find that constraints can become either significantly stronger, or considerably weaker, depending on the mass and width of the intermediate particle. We also discuss the special case of dark matter coupling to the Higgs boson, and we show that searches for invisible Higgs decays would provide superior sensitivity, particularly for a light Higgs mass and light dark matter.
51428350
Soft RPV through the baryon portal
A bstractSupersymmetric (SUSY) models with R-parity generically predict sparticle decays with invisible neutralinos, which yield distinctive missing energy events at colliders. Since most LHC searches are designed with this expectation, the putative bounds on sparticle masses become considerably weaker if R-parity is violated so that squarks and gluinos decay to jets with large QCD backgrounds. Here we introduce a scenario in which baryonic R-parity violation (RPV) arises effectively from soft SUSY breaking interactions, but leptonic RPV remains accidentally forbidden to evade constraints from proton decay and FCNCs. The model features a global R-symmetry that initially forbids RPV interactions, a hidden R-breaking sector, and a heavy mediator that communicates this breaking to the visible sector. After R-symmetry breaking, the mediator is integrated out and an effective RPV A-term arises at tree level; RPV couplings between quarks and squarks arise only at loop level and receive additional suppression. Although this mediator must be heavy compared to soft masses, the model introduces no new hierarchy since viable RPV can arise when the mediator mass is near the SUSY breaking scale. In generic regions of parameter space, a light thermally-produced gravitino is stable and can be a viable dark matter candidate.
119226535
LEP shines light on dark matter
Dark matter pair production at high energy colliders may leave observable signatures in the energy and momentum spectra of the objects recoiling against the dark matter. We use LEP data on mono-photon events with large missing energy to constrain the coupling of dark matter to electrons. Within a large class of models, our limits are complementary to and competitive with limits on dark matter annihilation and on WIMP-nucleon scattering from indirect and direct searches. Our limits, however, do not suer from systematic and astrophysical uncertainties associated with direct and indirect limits. For example, we are able to rule out light (. 10 GeV) thermal relic dark matter with universal couplings exclusively to charged leptons. In addition, for dark matter mass below about 80 GeV, LEP limits are stronger than Fermi constraints on annihilation into charged leptons in dwarf spheroidal galaxies. Within its kinematic reach, LEP also provides the strongest constraints on the spin-dependent direct detection cross section in models with universal couplings to both quarks and leptons. In such models the strongest limit is also set on spin independent scattering for dark matter masses below 4 GeV. Throughout our discussion, we consider both low energy eective theories of dark matter, as well as several motivated renormalizable scenarios involving light mediators.
122883218
Radiative Corrections to Electron-Proton Scattering
The radiative corrections to the electron-proton scattering are calculated with the effects of the proton recoil taken into account. We assumed the experimental conditions of Hofstadter et al. at Stanford, namely only the final electrons are momentum-analyzed. The anisotropy in the maximum energy of photons which can be emitted and the radiation from the proton current are the two main effects due to the proton recoil, and both effects are considered. The mesonic effects in the two-photon exchange diagrams are not considered. Other than the uncertainty in the mesonic effects, our formula is good up to about 5 Bev.
53605181
An updated analysis of Inert Higgs Doublet Model in light of the recent results from LUX, PLANCK, AMS-02 and LHC
In light of the recent discovery by the ATLAS and CMS experiments at the Large Hadron Collider (LHC) of a Higgs-like particle with a narrow mass range of 125–126 GeV, we perform an updated analysis on one of the popular scalar dark matter models, the Inert Higgs Doublet Model (IHDM). We take into account in our likelihood analysis of various experimental constraints, including recent relic density measurement, dark matter direct and indirect detection constraints as well as the latest collider constraints on the invisible decay width of the Higgs boson and monojet search at the LHC. It is shown that if the invisible decay of the standard model Higgs boson is open, LHC as well as direct detection experiments like LUX and XENON100 could put stringent limits on the Higgs boson couplings to dark matter. We find that the most favoured parameter space for IHDM corresponds to dark matter with a mass less than 100 GeV or so. In particular, the best-fit points are at the dark matter mass around 70 GeV where the invisible Higgs decay to dark matter is closed. Scalar dark matter in the higher mass range of 0.5–4 TeV is also explored in our study. Projectedmore » sensitivities for the future experiments of monojet at LHC-14, XENON1T and AMS-02 one year antiproton flux are shown to put further constraints on the existing parameter space of IHDM.« less
120043110
Bayesian implications of collider and SUSY dark matter direct and indirect searches
In this talk we present our recent Bayesian analyses of the Constrained MSSM in which the model's parameter space is constrained by the CMS αT 1.1/fb data at the LHC, the XENON100 dark matter direct detection data, and Fermi-LAT γ-ray data from dwarf spheroidal galaxies (dSphs). We also show that the projected one-year sensitivities for annihilation-induced neutrinos from the Sun in the 86-string configuration of IceCube/DeepCore have the potential to yield additional constraining power on the parameter space of the CMSSM.
2397140
Search for new mechanism of CP violation through tau decay and semileptonic decay at hadrons
If CP is violated in any decay process involving leptons it will signify the existence of a new force (called the X boson) responsible for CP violation that may be the key to understanding matter-antimatter asymmetry in the universe. The author discusses the signatures of CP violation in (1) the decay of tau lepton, and (2) the semileptonic decay of {pi}, K, D, B and t particles by measuring the polarization of the charged lepton in the decay. The author discusses how the coupling constants and their phases of the coupling of the X boson to 9 quark vertices and 3 lepton vertices can be obtained through 12 decay processes.
18956502
Global fits of the Non-Universal Higgs Model
We examine the Non-Universal Higgs Model (NUHM) with the help of a Markov Chain Monte Carlo scanning technique and Bayesian statistics. The method allows us to reveal more fully the remarkably rich and complex structure of the model and also some new interesting features. In particular we find that, for large ranges of parameters, the neutralino dark matter in the model is higgsino-like with mass close to 1 TeV. This feature does depend to some extent on the prior but generically results from a mild focussing effect in the running of one of the Higgs masses that we also point out. On the other hand, the usual bino-like neutralino is also present, and in some sense is favored by a more robust prior and a better average chi–square. In spite of experimental constraints often favoring different regions of parameter space than in the Constrained MSSM, most observational consequences appear fairly similar, which will make it challenging to experimentally distinguish the two models.