Amitava Datta

Reduced LHC constraints for higgsino-like heavier electroweakinos

As a sequel to our earlier work on wino-dominated ˜ � ± and ˜ � 0 (wino models), we focus on the pMSSM models where ˜ � ± , ˜ � 0 and ˜ � 0 are either higgsino dominated (higgsino models) or admixtures of significant amount of higgsino and wino components (mixed models), with or without light sleptons. The LHC constraints in the trilepton channel are significantly weaker even in the presence of light sleptons, especially in the higgsino models, compared to those mostly studied by the LHC collaborations with wino-dominated ˜ � ± and ˜

Neutralino dark matter confronted by the LHC constraints on electroweak SUSY signals

A bstractThe supersymmetric particles (sparticles) belonging exclusively to the electroweak sector of the minimal supersymmetric standard model (MSSM) may hold the key to the observed dark matter relic density in the universe even if all strongly interacting sparticles are very heavy. The importance of the light EW sparticles in DM physics and in producing spectacular collider signals is emphasized. It is shown that even the preliminary data on the direct searches of these sparticles at the LHC, significantly constrain the parameter space of the MSSM compatible with the observed relic density and provide useful hints about the future search prospects. If in addition to the electroweak sparticles the gluinos are also within the reach of the LHC experiments, then the gluino mass limits in the light slepton scenario obtained via the canonical jets + / channel may be relaxed by as much as 25 % compared to the existing limits. But the corresponding same sign dilepton (SSD) + jets + / signal will yield enhanced limits competitive with the strongest limits currently available. This is illustrated with the help of benchmark scenarios at the generator level using PYTHIA. If the gluinos are just beyond the current reach of the LHC, then the generic n-lepton + m-jets + missing energy signal may discriminate between different DM producing mechanisms by comparing the signals corresponding to different values of n. This is illustrated by simulating the signals for n = 0 and n = 2 (the SSD signal).

Search for top squarks at Tevatron inspired by dark matter and electroweak baryogenesis

Abstract The search for the top squark ( t ˜ 1 ) within the kinematic reach of Tevatron Run II is of great contemporary interest. Such a t ˜ 1 can explain the baryon asymmetry of the universe provided 120 GeV ⩽ m t ˜ 1 ⩽ m t . Moreover if Δ m ≡ m t ˜ 1 − m χ ˜ 1 0 is small, where χ ˜ 1 0 is the lightest supersymmetric particle (LSP), the dark matter relic density as obtained from the WMAP data may be explained via t ˜ 1 -LSP coannihilation. In this scenario the decay t ˜ 1 → c χ ˜ 1 0 is likely to occur with 100% branching ratio but for small Δ m the conventional di-jet + E T signal becomes unobservable. We propose a new search strategy based on the di-jet + E T signature accompanied by an isolated cluster of energy which arises from a decaying heavy particle with characteristic decay length. Our preliminary simulations with Pythia indicate that for 100 GeV ⩽ m t ˜ 1 ⩽ 130 GeV this signal may be observable while somewhat lager m t ˜ 1 may still provide hints of new physics.

Can R-parity violation lower sin2β?

Abstract Recent time-dependent CP asymmetry measurements in the B d → J / ψK S channel by the BaBar and Belle Collaborations yield somewhat lower values of sin2 β compared to the one obtained from the standard model fit. If the inconsistency between these numbers persists with more statistics, this will signal new physics contaminating the B d → J / ψK S channel, thus disturbing the extraction of β . We show that the R -parity-violating interactions in supersymmetric theories can provide extra new phases which play a role in significantly reducing the above CP asymmetry, thus explaining why BaBar and Belle report lower values of sin2 β . The same couplings also affect the B d → φK S decay rate and asymmetry, explain the B → η ′ K anomaly, and predict nonzero CP asymmetry in dominant B s decays. The scenario will be tested in the ongoing and upcoming B factories.

Yukawa unification and unstable minima of the supersymmetric scalar potential

Motivated by the possibilities of

Tracking down the elusive charginos/neutralinos through {tau} leptons at the Large Hadron Collider

b\ensuremath{-}\ensuremath{\tau}

Supersymmetric dark matter at the LHC 7-TeV run

or

Electroweak precision data, light sleptons and stability of the SUSY scalar potential

t\ensuremath{-}b\ensuremath{-}\ensuremath{\tau}

LHC signature of the minimal SUGRA model with a large soft scalar mass

Yukawa unification in the supersymmetric grand unified theories, we consider the dangerous directions of the supersymmetric potential for large values of

Many faces of low mass neutralino dark matter in the unconstrained MSSM, LHC data and new signals

\mathrm{tan}\ensuremath{\beta}(\ensuremath{\gtrsim}30),