Recently, the Fermi-LAT collaboration reported upper limits on the GeV gamma-ray flux from nearby clusters of galaxies. Motivated by these limits, we study corresponding constraints on gamma-ray emissions from two specific decaying dark matter models, one via grand unification scale suppressed operators and the other via R-parity violating operators. Both can account for the PAMELA and Fermi-LAT excesses of e ± . For GUT decaying dark matter, the gamma-rays from the M49 and Fornax clusters, with energy in the range of 1 to 10 GeV, lead to the most stringent constraints to date. As a result, this dark matter is disfavored with conventional model of e ± background. In addition, it is likely that some tension exists between the Fermi-LAT e ± excess and the gamma-ray constraints for any decaying dark matter model, provided conventional model of e ± background is adopted. Nevertheless, the GUT decaying dark matter can still solely account for the PAMELA positron fraction excess without violating the gamma-ray constraints.For the gravitino dark matter model with R-parity violation, cluster observations do not give tight constraints. This is because a different e ± background has been adopted which leads to relatively light dark matter mass around 200 GeV. *
Editor: M. Cvetič Dipole operatorsσ μν F μν b requires the helicity flip in the involving quark states thus the breaking of chiral U (3) Q × U (3) d .On the other hand, the b quark mass generation is also a consequence of chiral U (3) Q × U (3) d symmetry breaking. Therefore, in many models, there might be strong correlation between the b → sγ and b quark Yukawa coupling. In this Letter, we use non-decoupling MSSM model to illustrate this feature. In the scenario, the light Higgs boson may evade the direct search experiments at LEPII or Tevatron while the 125 GeV Higgs-like boson is identified as the heavy Higgs boson in the spectrum. A light charged Higgs is close to the heavy Higgs boson which is of 125 GeV and its contribution to b → sγ requires large supersymmetric correction with large PQ and R-symmetry breaking. The large supersymmetric contribution at the same time significantly modifies the b quark Yukawa coupling. With combined flavor constraints B → X s γ and B s → μ + μ − and direct constraints on Higgs properties, we find best fit scenarios with light stop of O(500 GeV), negative A t around −750 GeV and large μ-term of 2-3 TeV. In addition, reduction in bb partial width may also result in large enhancement of τ τ decay branching fraction. Large parameter region in the survival space under all bounds may be further constrained by H → τ τ if no excess of τ τ is confirmed at LHC. We only identify a small parameter region with significant H → hh decay that is consistent with all bounds and reduced τ τ decay branching fraction. In the end, if current dark matter mostly consists of neutralino, direct detection experiments like XENON100 also puts stringent bound over this scenario with light Higgs bosons. The light stops which are required by flavor constraints can further enhance the scattering cross section.
Motivated by the observed excess of the di-photon signal in Higgs searches, σ γγ /σ SM ≃ 1.5, we argue that models with enhanced Γ(h → γγ) alone are the most favorable scenarios when the latest LHC/Tevatron results are all taken into account. We study the phenomenology of a supersymmetric scenario of light stau first proposed by Carena et. al. [1] that predicts a 125 GeV SM-like Higgs boson with enhanced diphoton decay through light stau loops. Since it is extremely challenging to search the Drell-Yan stau pair at the LHC due to the small production rate, we focus on the parameter space with enhanced production of inclusive stau pairs, in particular, via bb fusion or gaugino pairs. We study its phenomenology in both pure leptonic tau τ ± ℓ channels and hadronic tau tagged τ h channels. We find the same-sign dilepton fromχ ± 1χ 0 2 → τ ± ℓ τ ± ℓ + X may significantly improve the discovery potential with even 7-8 TeV LHC of O(30 fb −1 ) data. In the case of hadronic tau pair, we use the final state j +τ h τ h + E T to search and find that even with the most optimistic region of M 2 ∼ 200 − 300 GeV, it requires at least 50 fb −1 data of 14 TeV LHC to reach a significance of 3.5 σ. Therefore, we conclude it is difficult to claim discovery only through hadronic tau based on the data by the 2012 shut-down. 5 σ reach for our most optimistic region then requires 100 fb −1 data with 14 TeV running.a Corresponding
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