Santosh Kumar Rai

Signatures for right-handed neutrinos at the large hadron collider.

We explore possible signatures for right-handed neutrinos in a TeV scale B-L extension of the standard model at the Large Hadron Collider. The studied four lepton signal has a tiny standard model background. We find the signal experimentally accessible at the LHC for the considered parameter regions.

750 GeV diphoton excess in a U(1) hidden symmetry model

Recent results from the experimental collaborations at LHC give hints of a resonance in the diphoton channel at an invariant mass of 750 GeV. We show that such a scalar resonance would be possible in an

Probing top charged-Higgs production using top polarization at the Large Hadron Collider

U(1)

Top quark asymmetry and Wjj excess at CDF from gauged flavor symmetry.

extension of the SM where the extended symmetry is hidden and yet to be discovered. We explore the possibilities of accommodating this excess by introducing a minimal extension to the matter content and highlight the parameter space that can accommodate the observed diphoton resonance in the model. The model also predicts new interesting signals that may be observed at the current LHC run.

Higgs data confronts Sequential Fourth Generation Fermions in the Higgs Triplet Model

We study single top production in association with a charged Higgs in the type II two Higgs doublet model at the Large Hadron Collider. The polarization of the top, reflected in the angular distributions of its decay products, can be a sensitive probe of new physics in its production. We present theoretically expected polarizations of the top for top charged-Higgs production, which is significantly different from that in the closely related process of tW production in the Standard Model. We then show that an azimuthal asymmetry, constructed from the decay lepton angular distribution in the laboratory frame, is a sensitive probe of top polarization and can be used to constrain parameters involved in top charged-Higgs production.

Single production of sleptons with polarized tops at the large hadron collider

We show that the scalar sector needed for fermion mass generation when the flavor symmetry of the standard model is maximally gauged can consistently explain two anomalies reported recently by the CDF Collaboration-the forward-backward asymmetry in tt pair production and the dijet invariant mass in the Wjj channel. A pair of nearly degenerate scalar doublets with masses in the range 150-200 GeV explain these anomalies, with additional scalars predicted in the mass range 100-400 GeV. Consistency of such low scale flavor physics with flavor-changing processes is shown, and expectations for the LHC are outlined.

New Signals for Doubly-Charged Scalars and Fermions at the Large Hadron Collider

We investigate the effect of introducing a sequential generation of chiral fermions in the Higgs Triplet Model with nontrivial mixing between the doublet and triplet Higgs. We use the available LHC data for Higgs boson production and decay rates, the constraints on the fourth generation masses, and impose electroweak precision constraints from the S, T and U parameters. Our analysis shows that an SM-like Higgs boson state at ~125 GeV can be accommodated in the Higgs Triplet Model with four generations, and thus, that four generations survive collider and electroweak precision constraints in models beyond SM.

Signals of doubly-charged Higgsinos at the CERN Large Hadron Collider

We study the production of a single charged slepton in association with a top quark in a R-parity violating supersymmetric model with lepton number violating interactions at the Large Hadron Collider. We find that the longitudinal polarization asymmetry of the top quark in such a production mode is significantly different from that in the production of a single top or a top pair in the Standard Model for a wide range of slepton masses. Our signal analysis shows that the top-slepton associate production leads to final states with distinct kinematic signatures, which differ from the Standard Model background.

Disentangling the Unparticles with polarized beams at e+e- colliders

Several extensions of the Standard Model have light doubly-charged Higgs bosons in their particle spectrum. The supersymmetric versions of these models introduce fermionic superpartners of these doubly-charged Higgs bosons, the Higgsinos, which also remain light. In this work we analyze a new collider signal resulting from the pair production and decay of a light doubly-charged Higgsino to an even lighter doublycharged Higgs boson. We focus on the minimal left-right supersymmetric model with automatic R-parity conservation, which predicts such a light doubly-charged Higgs boson and its Higgsino partner at the TeV scale, which are singlets of SU(2)L. We investigate the distinctive signatures of these particles with four leptons and missing transverse energy in the final state at the Large Hadron Collider and show that the discovery reach for both particles can be increased in this channel.

Comparison of neutralino and sneutrino dark matter in a model with spontaneous CP violation

Several supersymmetric models with extended gauge structures, motivated by either grand unification or by neutrino mass generation, predict light doubly-charged Higgsinos. In this work we study productions and decays of doubly-charged Higgsinos present in left-right supersymmetric models, and show that they invariably lead to novel collider signals not found in the minimal supersymmetric model or in any of its extensions motivated by the {mu} problem or even in extra dimensional theories. We investigate their distinctive signatures at the Large Hadron Collider in both pair- and single-production modes, and show that they are powerful tools in determining the underlying model via the measurements at the Large Hadron Collider experiments.