Signatures of Sneutrino NLSP in Gravitino Dark Matter Scenario at the LHC

We present the phenomenology of a supersymmetric model with sneutrino as the next to lightest supersymmetric particle (NLSP) in the gravitino dark matter scenario at the LHC. We focus on the leptonic signatures and study the feasibility of a particular trilepton signature as a possible discovery channel of supersymmetry.Comment: 4 pages, talk at SUSY09 conference, Boston, USA, June 200

CP Violating Lepton Asymmetry from B Decays in Supersymmetric Grand Unified Theories

We investigate the effect of the dimuon CP asymmetry from the B decay modes, recently observed at 3.2 sigma deviation from the Standard Model (SM) by the D0 collaboration, in the context of SU(5) and SO(10) GUT models. We exhibit that a large amount of flavor violation between the second and the third generation is generated due to the large neutrino atmospheric mixing angle and this flavor violation can be responsible for the observed large CP asymmetry due to the presence of new phases (not present in the CKM matrix) in the Yukawa couplings. We also study the implication of the parameter space in these GUT models with large CP violating lepton asymmetry for different phenomenologies, e.g., Br(tau -> mu + gamma), Br(B_s -> mu + mu) at the Fermilab, direct detection of dark matter (DM) in the ongoing detectors and measurement of muon flux from solar neutrinos at the IceCube experiment.Comment: 23 pages, 5 figure

Tau-Sneutrino NLSP and Multilepton Signatures at the LHC

In models with gravitino as the lightest supersymmetric particle(LSP), the next to lightest supersymmetric particle (NLSP) can have a long lifetime and appear stable in collider experiments. We study the leptonic signatures of such a scenario with tau-sneutrino as the NLSP, which is realized in the non-universal Higgs masses scenario. We focus on an interesting trilepton signature with two like-sign taus and an electron or a muon of opposite sign. The neutralinos and charginos are quite heavy in the model considered, and the trilepton signal comes mostly from the slepton-sneutrino production. We identify the relevant backgrounds, taking into account tau decays, and devise a set of cuts to optimize this trilepton signal. We simulate signal and backgrounds at the LHC with 14 TeV center-of-mass energy. Although the sleptons in this model are relatively light, O(100 GeV), discovery is more demanding compared to typical neutralino LSP scenarios. The trilepton signal requires large amount of accumulated data, at least ~80 fb^-1, at the CM energy of 14 TeV.Comment: 25 pages, 6 figures, minor changes to match the version published in Phys.Rev.

The Phenomenology of Gravitino Dark Matter Scenarios in Supergravity Models

We review the phenomenology of gravitino dark matter within supergravity framework. Gravitino can be dark matter if it is the lightest supersymmetric particle, which is stable if R-parity is conserved. There are several distinct scenarios depending on what the next to lightest supersymmetric particle (NLSP) is. We discuss the constraints and summarize the phenomenology of neutralino, stau, stop and sneutrino NLSPs.Comment: 10 pages, contributed to the proceedings of the Seventh International Heidelberg Conference on Dark Matter in Astro and Particle Physics (Dark 2009), Christchurch, New Zealand, 18-24 January 200

MSSM inflation, dark matter, and the LHC

Inflation can occur near a point of inflection in the potential of flat directions of the Minimal Supersymmetric Standard Model. In this paper we elaborate on the complementarity between the bounds from Cosmic Microwave Background measurements, dark matter and particle physics phenomenology in determining the underlying parameters of MSSM inflation by specializing to the Minimal Supergravity scenario. We show that the future measurements from the Large Hadron Collider in tandem with all these constraints will significantly restrict the allowed parameter space. We also suggest a new perspective on the fine tuning issue of MSSM inflation. With quantum corrections taken into account, the necessary condition between the soft supersymmetry breaking parameters in the inflaton potential can be satisfied at scales of interest without a fine tuning of their boundary values at a high scale. The requirement that this happens at the inflection point determines a dimensionless coupling, which is associated with a non-renormalizable interaction term in the Lagrangian and has no bearing for phenomenology, to very high accuracy.Comment: 9 pages, 9 figure

The MSSM Parameter Space with Non-Universal Higgs Masses

Without assuming that Higgs masses have the same values as other scalar masses at the input GUT scale, we combine constraints on the minimal supersymmetric extension of the Standard Model (MSSM) coming from the cold dark matter density with the limits from direct searches at accelerators such as LEP, indirect measurements such as b to s gamma decay and the anomalous magnetic moment of the muon. The requirement that Higgs masses-squared be positive at the GUT scale imposes important restrictions on the MSSM parameter space, as does the requirement that the LSP be neutral. We analyze the interplay of these constraints in the (mu, m_A), (mu, m_{1/2}), (m_{1/2}, m_0) and (m_A, tan beta) planes. These exhibit new features not seen in the corresponding planes in the constrained MSSM in which universality is extended to Higgs masses.Comment: 18 pages, latex, 10 eps figure

Cosmological scenario of stop NLSP with gravitino LSP and the cosmic lithium problem

The discrepancy on Li^7 and Li^6 abundances between the observational data and the standard Big Bang Nucleosynthesis theory prediction has been a nagging problem in astrophysics and cosmology, given the highly attractive and succesful Big Bang paradigm. One possible solution of this lithium problem is through hadronic decays of a massive metastable particle which alter the primordial element abundances. We explore this possibility using gravitino dark matter framework in which the next lightest supersymmetric particle (NLSP) is typically long-lived. We found that stop NLSP can provide an attractive solution to the lithium problem.Comment: 12 pages, 3 figure