Neutralino dark matter in light Higgs boson scenario

Phenomenology of neutralino dark matter in the minimal supersymmetric model is discussed for a scenario where the lightest Higgs boson mass is lighter than 114.4 GeV$114.4\text{GeV}$. We show that the scenario is consistent not only with many collider experiments but also with the observed relic abundance of dark matter. The allowed region may be probed by experiments of Bs→μ⁺μ⁻$B_s\to {\mu }^{+}{\mu }^{-}$ in near future. The scenario predicts a large scattering cross section between the dark matter and ordinary matter and thus it may be tested in present direct detection experiments of dark matter.     

Photons from dark matter in a (non-universal) extra dimension model

We study the multi-wavelength signal induced by pairs annihilations at the galactic center (GC) of a recently proposed dark matter (DM) candidate. The weakly interacting massive particle (WIMP) candidate, named A₋$A_{-}$, is the first Kaluza–Klein mode of a five-dimensional Abelian gauge boson. Electroweak precision tests and the DM cosmological bound constrain its mass and pair annihilation rate in small ranges, leading to precise predictions of indirect signals from what concerns the particle physics side. The related multi-wavelength emission is expected to be faint, unless a significant enhancement of the DM density is present at the GC. We find that in this case, and depending on few additional assumptions, the next generation of gamma-ray and wide-field radio observations can test the model, possibly even with the detection of the induced monochromatic gamma-ray emission.     

Explaining the DAMA signal with WIMPless dark matter

WIMPless dark matter provides a framework in which dark matter particles with a wide range of masses naturally have the correct thermal relic density. We show that WIMPless dark matter with mass around 2–10 GeV can explain the annual modulation observed by the DAMA experiment without violating the constraints of other dark matter searches. This explanation implies distinctive and promising signals for other direct detection experiments, GLAST, and the LHC.     

On prospects for dark matter indirect detection in the Constrained MSSM

We apply a rigorous statistical analysis to the Constrained MSSM to derive the most probable ranges of the diffuse gamma radiation flux from the direction of the Galactic center and of the positron flux from the Galactic halo due to neutralino dark matter annihilation, for several different choices of the halo model and propagation model parameters. We find that, for a specified halo profile, and assuming flat priors, the 68% probability range of the integrated γ-ray flux spans about one order of magnitude, while the 95% probability range can be much larger and extend over four orders of magnitude (even exceeding five for a tiny region at small neutralino mass). The detectability of the signal by GLAST depending primarily on the cuspiness of the halo profile. The positron flux, on the other hand, appears to be too small to be detectable by PAMELA, unless the boost factor is at least of order ten and/or the halo profile is extremely cuspy. We also briefly discuss the sensitivity of our results to the choice of priors.     

Single Production of Vector-Like Top Quark in the Littlest Higgs Model at TeV Energy e-γ Colliders

The existence of a new coloured vector-like heavy fermion T is a crucial prediction in little Higgs models, which play a key role in breaking the electroweak symmetry. The littlest Higgs model is the most economical one among various little Higgs models. In the context of the littlest Higgs model, we study single production of the new heavy vector-like quark and discuss the possibility of detecting this new particle in the future LC experiment. It is found thai, the production cross section is in the range of 1.7× 10^-3 - 30 fb at TeV energy electron-photon collider with √s- 3 TeV and a yearly integrated luminosity of ,￡ = 500 fb^-1.     

Probing the reheating temperature at colliders and with primordial nucleosynthesis

Considering gravitino dark matter scenarios with a long-lived charged slepton, we show that collider measurements of the slepton mass and its lifetime can probe not only the gravitino mass but also the post-inflationary reheating temperature TR$T_{\mathrm{R}}$. In a model independent way, we derive upper limits on TR$T_{\mathrm{R}}$ and discuss them in light of the constraints from the primordial catalysis of ⁶Li through bound-state effects. In the collider-friendly region of slepton masses below 1 TeV, the obtained conservative estimate of the maximum reheating temperature is about TR=3×¹⁰⁹ GeV$T_{\mathrm{R}}=3\times {10}^9\text{GeV}$ for the limiting case of a small gluino–slepton mass splitting and about TR=¹⁰⁸ GeV$T_{\mathrm{R}}={10}^8\text{GeV}$ for the case that is typical for universal soft supersymmetry breaking parameters at the scale of grand unification. We find that a determination of the gluino–slepton mass ratio at the Large Hadron Collider will test the possibility of TR>¹⁰⁹ GeV$T_{\mathrm{R}}>{10}^9\text{GeV}$ and thereby the viability of thermal leptogenesis with hierarchical heavy right-handed Majorana neutrinos.     

Mini little Higgs and dark matter

We construct a little Higgs model with the most minimal extension of the standard model gauge group by an extra U(1)$U(1)$ gauge symmetry. For specific charge assignments of scalars, an approximate U(3)$U(3)$ global symmetry appears in the cutoff-squared scalar mass terms generated from gauge bosons at one-loop level. Hence, the Higgs boson, identified as a pseudo-Goldstone boson of the broken global symmetry, has its mass radiatively protected up to scales of 5–10 TeV. In this model, a Z₂$Z_2$ symmetry, ensuring the two U(1)$U(1)$ gauge groups to be identical, also makes the extra massive neutral gauge boson stable and a viable dark matter candidate with a promising prospect of direct detection.     

Upward muon signals at neutrino detectors as a probe of dark matter properties

We study upward muon flux at neutrino detectors such as Super-Kamiokande resulting from high-energy neutrinos produced by the dark matter annihilation/decay at the Galactic center. In particular, we distinguish showering and non-showering muons as their energy loss processes inside the detector, and show that this information is useful for discriminating dark matter models.     

Late energy injection and cosmological constraints in axino dark matter scenarios

Taking into account effects of late energy injection, we examine big bang nucleosynthesis (BBN) constraints on axino dark matter scenarios with long-lived charged sleptons. We calculate 4-body slepton decays into the axino, a lepton, and a quark–antiquark pair since they govern late hadronic energy injection and associated BBN constraints. For supersymmetric hadronic axion models, we present the obtained hadronic BBN constraints and show that they can be more restrictive than the ones associated with catalyzed BBN via slepton-bound-state formation. From the BBN constraints on hadronic and electromagnetic energy release, we find new upper limits on the Peccei–Quinn scale.     

SUSY constraints from relic density: High sensitivity to pre-BBN expansion rate

The sensitivity of the lightest supersymmetric particle relic density calculation to the variation of the cosmological expansion rate before nucleosynthesis is discussed. Such a modification of the expansion rate, even extremely modest and with no consequence on the cosmological observations, can greatly enhance the calculated relic density, and therefore change the constraints on the SUSY parameter space drastically. We illustrate this variation in two examples of SUSY models, and show that it is unsafe to use the lower bound of the WMAP limits in order to constrain supersymmetry. We therefore suggest to use only the upper value ΩDMh²<0.135${\Omega }_{\mathrm{DM}}{h}^2<0.135$.     

Probing light pseudoscalar particles using synchrotron light

The need for purely laboratory-based light pseudoscalar particles searches has been emphasized many times in the literature, since astrophysical bounds on these particles rely on several assumptions to calculate the flux produced in stellar plasmas. In this Letter we study the use of light from synchrotron accelerators as a source for a photon regeneration experiment also know as “light shining through a wall”. Such an experiment can significantly improve present limits on the pseudoscalar particle mass and the pseudoscalar–photon coupling constant obtained from laser experiments. This is possible even using a small number of powerful magnets (B∼10 T$B\sim 10\text{T}$), due to the large incident photon flux. On the other hand, the use of a broadband incident photon-beam instead of infrared or optical lasers allows a significant improvement in the mass reach of the experiment (it is possible to test masses up to 0.01 eV without a drop in sensitivity). Large, but still feasible, configurations can explore in a quite model-independent way a large part of the parameter space examined by solar searches and HB stars in globular clusters. Additionally, the proposal may be useful for testing string motivated effective theories containing light and weakly interacting particles.     

Early Universe cosmology in the light of the mirror dark matter interpretation of the DAMA/Libra signal

Mirror dark matter provides a simple framework for which to explain the DAMA/LIBRA annual modulation signal consistently with the null results of the other direct detection experiments. The simplest possibility involves ordinary matter interacting with mirror dark matter via photon–mirror photon kinetic mixing of strength ?∼¹⁰⁻⁹$\mathrm{?}\sim {10}^{-9}$. We confirm that photon–mirror photon mixing of this magnitude is consistent with constraints from ordinary Big Bang nucleosynthesis as well as the more stringent constraints from cosmic microwave background measurements and large scale structure considerations.     

Axion condensate as a model for dark matter halos

Localized solutions of an axion-like scalar model with a periodic self-interaction are analyzed as a model of dark matter halos. It is shown that such a cold Bose–Einstein type condensate can provide a substantial contribution to the observed rotations curves of galaxies, as well provide a soliton type interpretation of the dark matter ‘bullets’ observed via gravitational lensing in merging clusters.     

Accelerating Universe with spacetime torsion but without dark matter and dark energy

It is shown that cosmological equations for homogeneous isotropic models deduced in the framework of the Poincaré gauge theory of gravity by certain restrictions on indefinite parameters of gravitational Lagrangian take at asymptotics the same form as cosmological equations of general relativity theory for ΛCDM-model. Terms related to dark matter and dark energy in cosmological equations of standard theory for ΛCDM-model are connected in considered theory with the change of gravitational interaction provoked by spacetime torsion.     

Distinguishing between dark matter and pulsar origins of the ATIC electron spectrum with atmospheric Cherenkov telescopes

Recent results from the Advanced Thin Ionization Calorimeter (ATIC) balloon experiment have identified the presence of a spectral feature between approximately 300 and 800 GeV in the cosmic ray electron spectrum. This spectral feature appears to imply the existence of a local (1 kpc) source of high energy electrons. Emission from a local pulsar and dark matter annihilations have each been put forth as possible origins of this signal. In this Letter, we consider the sensitivity of ground based atmospheric Cherenkov telescopes to electrons and show that observatories such as HESS and VERITAS should be able to resolve this feature with sufficient precision to discriminate between the dark matter and pulsar hypotheses with considerably greater than 5σ significance, even for conservative assumptions regarding their performance. In addition, this feature provides an opportunity to perform an absolute calibration of the energy scale of ground based, gamma ray telescopes.     

Light response of a pure liquid Xenon scintillator irradiated with 2.5 MeV neutrons

In this paper the results obtained by exposing a pure liquid Xenon scintillator to 2.5 MeV neutrons are presented. In particular, the ratio of the measured amount of light from a recoil nucleus to the amount of light from an electron of the same kinetic energy has been investigated. Results substantially in agreement with previous determinations are obtained. A figure of r = 0.46 ± 0.10 is cumulatively obtained.     

The νMSM,inflation, and dark matter

We show how to enlarge the νMSM (the minimal extension of the Standard Model by three right-handed neutrinos) to incorporate inflation and provide a common source for electroweak symmetry breaking and for right-handed neutrino masses. In addition to inflation, the resulting theory can explain simultaneously dark matter and the baryon asymmetry of the Universe; it is consistent with experiments on neutrino oscillations and with all astrophysical and cosmological constraints on sterile neutrino as a dark matter candidate. The mass of inflaton can be much smaller than the electroweak scale.     

Modified Newton's gravity in Finsler space as a possible alternative to dark matter hypothesis

A modified Newton's gravity is obtained as the weak field approximation of the Einstein's equation in Finsler space. It is found that a specified Finsler structure makes the modified Newton's gravity equivalent to the modified Newtonian dynamics (MOND). In the framework of Finsler geometry, the flat rotation curves of spiral galaxies can be deduced naturally without invoking dark matter.