Kirtiman Ghosh

Compressed supersymmetry at 14 TeV LHC

In this work we study the collider phenomenology of a compressed supersymmetric model with gluino (e) and the lightest neutralino (e � 0 ). All other sparticles are assumed to be heavy. We consider gluino pair production at the 14 TeV LHC and present the mass reach of gluino as a function of mass splitting between gluino and the the lightest neutralino. We find that the gluino mass below 1 TeV can be excluded at 95% CL with integrated luminosity of 100 fb 1 for extreme degenerate case where mass separation between gluino and the lightest neutralino is about 20 GeV. On the other hand, the lower bound on the mass of gluino increases to 1.2 - 1.3 TeV if the mass splitting between the gluino and e � 0 is about 200 GeV. This result shows that for degenerate gluino, the current mass limit may extend approximately 400-500 GeV at 14 TeV LHC.

Search for the minimal universal extra dimension model at the LHC with {radical}(s)=7 TeV

Universal Extra Dimension (UED) model is one of the popular extension of the Standard Model (SM) which offers interesting phenomenology. In the minimal UED (mUED) model, Kaluza-Klein (KK) parity conservation ensures that n = 1 KK states can only be pair produced at colliders and the lightest KK particle is stable. In most of the parameter space, first KK excitation of SM hypercharge gauge boson is the lightest one and it can be a viable dark matter candidate. Thus, the decay of n = 1 KK particles will always involve missing transverse energy (ET / ) as well as leptons and jets. The production cross sections of n = 1 KK particles are large and such particles may be observed at the Large Hadron Collider (LHC). We explore the mUED discovery potential of the LHC with p s = 7 TeV in the multileptonic final states. Since in the early LHC run, precise determination of ET / may not be possible, we examine the LHC reach with and without using ET / information. We observe that ET / cut will not improve mUED discovery reach significantly. We have found that opposite sign di-lepton channel is the most promising discovery mode and with first fb 1 of collected luminosity, LHC will be able to discover the strongly interacting n = 1 KK particles with masses upto 800 � 900 GeV. PACS numbers: 13.85.Qk, 12.60.-i,14.80.Rt

Signals of an invisibly decaying Higgs boson in a scalar dark matter scenario: A study for the Large Hadron Collider

We consider the collider phenomenology of a singlet Majoron model with softly broken lepton number. Lepton number is spontaneously broken when the real part of a new singlet scalar develops a vacuum expectation value. With the additional soft terms violating lepton numbers, the imaginary part of this singlet scalar becomes a massive pseudo-Majoron which can account for the dark matter. In the presence of the coupling of the pseudo-Majoron with the standard model (SM) Higgs, the SM Higgs mostly decays into a pair of pseudo-Majorons, giving rise to E T signals at a hadron collider. Since the Higgs visible decay branching fractions get reduced in the presence of this invisible decay mode, the bounds on the SM Higgs mass from the CERN LEP and Tevatron experiments get diluted, and the invisible decay channel of the Higgs becomes important for the discovery of low mass Higgs at the Large Hadron Collider.

Top quark jets as a probe of the constrained minimal supersymmetric standard model with a degenerate top squark and lightest supersymmetric particle.

X iv :1 20 7. 24 29 v1 [ he pph ] 1 0 Ju l 2 01 2 Top jets as a probe of degenerate stop-NLSP LSP scenario in the framework of cMSSM Kirtiman Ghosh, Katri Huitu, Jari Laamanen and Lasse Leinonen Department of Physics, and Helsinki Institute of Physics, FIN-00014 University of Helsinki, Finland and Theoretical High Energy Physics, IMAPP, Faculty of Science, Radboud University Nijmegen Mailbox 79, P.O. Box 9010, NL-6500 GL Nijmegen, The Netherlands kirti.gh@gmail.com, katri.huitu@helsinki.fi, j.laamanen@science.ru.nl, lasse.leinonen@helsinki.fi

Exploring two universal extra dimensions at the CERN LHC

A bstractWe discuss the signatures, at the LHC, of the (1,0)-th Kaluza-Klein (KK) gluon and quarks in the framework of the two universal extra dimensional (2UED) model. Once produced, these particles typically suffer a cascade of decays terminating in the Dark Matter candidate apart from Standard Model particles. In this article, we are interested in focus on a particular signature of 2UED wherein the final state comprises of at least four jets in association with a hard photon and missing transverse energy. Several kinematic cuts are devised to enhance the signal to background ratio. Finally, as a road map to parameter determination at the LHC, we point out an interesting correlation between the peak position of the Meff distributions with the compactification radius R and the cut-off scale Ms.

Discrimination of low missing energy look-alikes at the LHC

The problem of discriminating possible scenarios of TeV scale new physics with large missing energy signature at the Large Hadron Collider (LHC) has received some attention in the recent past. We consider the complementary, and yet unexplored, case of theories predicting much softer missing energy spectra. As there is enough scope for such models to fake each other by having similar final states at the LHC, we have outlined a systematic method based on a combination of different kinematic features which can be used to distinguish among different possibilities. These features often trace back to the underlying mass spectrum and the spins of the new particles present in these models. As examples of “low missing energy look-alikes”, we consider Supersymmetry with R-parity violation, Universal Extra Dimensions with both KK-parity conserved and KK-parity violated and the Littlest Higgs model with T-parity violated by the Wess-Zumino-Witten anomaly term. Through detailed Monte Carlo analysis of the four and higher lepton final states predicted by these models, we show that the models in their minimal forms may be distinguished at the LHC, while non-minimal variations can always leave scope for further confusion. We find that, for strongly interacting new particle mass-scale ∼600 GeV (1 TeV), the simplest versions of the different theories can be discriminated at the LHC running at

Probing sterile neutrinos in the framework of inverse seesaw mechanism through leptoquark productions

\sqrt {s} = 14\;{\text{TeV}}

Degenerate SUSY search at the 8 TeV LHC

within an integrated luminosity of 5 (30) fb−1.

Collider signatures of mirror fermions in the framework of a left-right mirror model

We consider an extension of the Standard Model (SM) augmented by two neutral singlet fermions per generation and a leptoquark. In order to generate the light neutrino masses and mixing, we incorporate inverse seesaw mechanism. The right handed neutrino production in this model is significantly larger than the conventional inverse seesaw scenario. We analyze the different collider signatures of this model and find that the final states associated with three or more leptons, multi jet and at least one b-tagged and (or)

The LHC Diphoton excess at 750 GeV in the framework of the Constrained Minimal Supersymmetric Standard Model

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