Sudhir Kumar Gupta - Monash University

Sudhir Kumar Gupta
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Name
Sudhir Kumar Gupta
Affiliation
Monash University
City
Caulfield East
Country
Australia

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Pub Categories

 
High Energy Physics - Phenomenology (21)
 
High Energy Physics - Experiment (6)
 
Instrumentation and Methods for Astrophysics (1)
 
Solar and Stellar Astrophysics (1)

Publications Authored By Sudhir Kumar Gupta

We study the flavor-changing couplings of the Higgs-boson with the top-quark using the processes: (a) pp --> tt, (b) pp --> t_bar j, and, (c) pp --> t_bar j h at the LHC in light of current discovery of a 126 GeV Higgs-Boson. Sensitivities for the flavor-changing couplings are estimated using the LHC data that was collected until spring 2013. It is found that the process (c) is the most capable of yielding the best upper bound on the flavor-changing couplings with 2 sigma level sensitivities of {|xi_{tc}^2 + xi_{tu}^2|}^{1/2} <= 4. Read More

The ATLAS and CMS collaborations have recently published new limits on CP conserving anomalous couplings from the $W\gamma$ and $Z\gamma$ production processes. We study the corresponding limits that can be placed on the CP violating anomalous couplings $\kappa_tilde_\gamma$ and $h^1_{\gamma, Z}$ at the LHC. We find that the process $pp --> W\gamma$ at 14 TeV can place the 95% CL limit $|\kappa_tilde_\gamma| <~ 0. Read More

We study the connection between the same sign top (SST) and the top quark forward-backward asymmetry $A^t_{FB}$. We find that a large class of new physics models that have been proposed to account for the $A^t_{FB}$ lead to SST quark production rate much larger than the observed rate at the LHC and consequently are severely constrained or ruled out. Our model independent, general, operator analysis shows that none of the tree-level flavor-changing operators are able to explain $A^t_{FB}$ and simultaneously remain consistent with the same-sign top-quark production constraints from the LHC data. Read More

In a Peccei-Quinn extension of supergravity the h --> \gamma\gamma detection rate can be significantly enhanced due to the reduction of the total Higgs decay width. To assess the viability of various Peccei-Quinn extensions of minimal supergravity we perform a Bayesian analysis on three such scenarios. The main constraints on these models come from the currently observed Higgs boson like state by the Large Hadron Collider and from the WMAP observation of dark matter abundance. Read More

We consider the phenomenology of the fourth generation heavy quarks which would be pair produced at the LHC. We show that if such a quark with a mass in the phenomenologically interesting range of 400 GeV--600 GeV decays to a light quark and a W-boson, it will produce a signal in a number of channels which can be seen above the background from the three generation Standard Model processes. In particular, such quarks could be seen in channels where multiple jets are present with large missing momentum and either a single hard lepton, an opposite sign hard lepton pair or a same sign lepton pair. Read More

We consider the possibility of studying new physics that singles out the tau-lepton at the LHC. We concentrate on the tau-lepton charge asymmetry in tau+tau- pair production as a tool to probe this physics beyond the Standard Model. We consider two generic scenarios for the new physics. Read More

We analyse same sign dilepton signatures in a non-universal flavor changing Z' model. These arise due to tt (or t_bar t_bar) production processes due to the semi-leptonic decays of (anti)tops. We also discuss top reconstruction and spin measurement using the variable MT2 and MT2-Assisted On-Shell (MAOS) Momentum} techniques and will also provide a comparison with the on-shell mass relation method. Read More

2010Jun
Affiliations: 1Iowa State University, 2Iowa State University

We investigate triphoton signals of the Randall-Sundram model at the Large Hadron Collider. Such a signal can be an important probe to the RS model as these are relatively cleaner from the hadronic activity and bear significant rate. The corresponding standard model background has also been studied in detail. Read More

2010May
Affiliations: 1Iowa State University, 2Iowa State University

Models with a non-universal Z' exhibit in general flavor changing neutral currents (FCNC) at tree-level. When the Z' couplings favor the third generation, flavor changing transitions of the form Z'tc and Z'tu could be large enough to be observable at the LHC. In this paper we explore this possibility using the associated production of a single top-quark with the Z' and find that integrated luminosities of a few hundred fb$^{-1}$ are necessary to probe the interesting region of parameter space. Read More

2009Dec

We discuss T-odd correlations between jet and lepton momenta in tt_bar events at the Tevatron that can be used to search for CP violation. We identify correlations suitable for the lepton plus jets and purely hadronic top-quark pair decay channels. As an example of CP violation we consider the top-quark anomalous couplings, including its chromo-electric dipole moment, and we estimate the limits that can be placed at the Tevatron. Read More

Littlest Higgs model with T-parity and Minimal Supersymmtric standard Model with R-parity both give similar signatures in collider experiment with a huge amount of missing energy depending upon mass of the lightest T-odd/R-odd particle. In this talk, I will discuss possibility of distinguishing the two models at the LHC in hadronically quiet signal where masses of R-odd particles are identical to masses of T-odd particles. Read More

In this talk, I review the T-odd correlations induced by CP violating anomalous top-quark couplings at both production and decay level in the process gg --> t t_bar --> (b mu+ nu_mu) (b_bar mu-nu_mu_bar). In addition I will also focus on experimental sensitivities corresponding to the anomalous couplings at the LHC. Read More

A new instrument with a dual-beam H-alpha Doppler system is being developed at the Udaipur Solar Observatory (USO) in order to improve the quality and quantity of data on quiet, activated and erupting filaments and prominences on the Sun, especially those associated with geo-effective coronal mass ejections. These data can be potentially used to construct three-dimensional topology of erupting filaments as they leave the surface of the Sun and can be compared with multi-wavelength data obtained from space missions such as STEREO, SOHO, and Hinode. The characterization of various optical components for the instrument is being carried out, and some preliminary results are described in the paper. Read More

2009May
Affiliations: 1Iowa State University, 2Iowa State University, 3Iowa State University

We study the T odd correlations induced by CP violating anomalous top-quark couplings at both production and decay level in the process gg --> t t_bar --> (b mu+ nu_mu) (b_bar mu- nu_mu_bar). We consider several counting asymmetries at the parton level and find the ones with the most sensitivity to each of these anomalous couplings at the LHC. Read More

We study B_s --> mu+ mu- in the context of the R-parity violating minimal supergravity in the high tan beta regime. We find that the lowest value of the branching ratio can go well below the present LHCb sensitivity and hence B_s --> mu+ mu- can even be invisible to the LHC. We also find that the present upper bound on Br(B_s --> mu+ mu-) puts strong constraint on the minimal supergravity parameter space. Read More

We consider the Littlest Higgs Model with T-parity (LHT), in the parameter region where a heavy neutrino is the lightest T-odd particle (LTP). Having emphasized that this corresponds to a sizable region in the parameter space of the theory, we show that both the Cryogenic Dark Matter Search (CDMS) and Xenon10 experiments disallow the entire region where the masses of the new particles in LHT can lie within several TeV. Therefore, any observation of the signals of a heavy neutrino LTP is likely to seriously reopen the issue of cold dark matter in the universe. Read More

We investigate charged tracks signals of a supersymmetric scenario, where the lighter stop is the next-to-lightest supersymmetric particle (NLSP). It is found that such an NLSP is stable on the scale of the detector at the LHC if one has a right-chiral sneutrino as the lightest supersymmetric particle (LSP). After identifying some benchmark points in the parameter space of a supergravity scenario with non-universal scalar masses, we study a few specific classes of signals, namely, stop pair production and gluino pair production followed by each decaying into a stop and a top. Read More

We study a supersymmetric scenario where the lighter tau-sneutrino is the lightest supersymmetric particle, while the lighter stau-state is the next lightest. Such a scenario can be motivated within the framework of minimal supergravity, with just the addition of a right-chiral neutrino superfield. Such a spectrum leads to rather unusual signals of supersymmetry, showing stable tracks of the stau in the muon chambers. Read More

2007Aug
Affiliations: 1Harish-Chandra Research Institute, 2Harish-Chandra Research Institute, 3Harish-Chandra Research Institute, 4Harish-Chandra Research Institute, 5Harish-Chandra Research Institute

We analyse hadronically quiet trilepton signatures in the T-parity conserving Littlest Higgs model and in R-parity conserving supersymmetry at the Large Hadron Collider. We identify the regions of the parameter space where such signals can reveal the presence of these new physics models above the Standard Model background and distinguish them from each other, even in a situation when the mass spectrum of the Littlest Higgs model resembles the supersymmetric pattern. Read More

2007Jan
Affiliations: 1Harish-Chandra Research Institute, 2Harish-Chandra Research Institute, 3Harish-Chandra Research Institute

We investigate the signals of a supersymmetric scenario where the lighter tau-sneutrino is the lightest supersymmetric particle, while the lighter stau-state is the next lightest. We confirm that such a scenario can be motivated within the framework of minimal supergravity, with just the addition of a right-chiral neutrino superfield. Such a spectrum leads to rather unusual signals of supersymmetry, showing stable tracks of the stau in the muon chambers. Read More

2005Oct
Affiliations: 1Harish-Chandra Research Institute, 2Harish-Chandra Research Institute, 3Harish-Chandra Research Institute

We examine the possibility of detecting signals of split supersymmetry in the loop-induced decay h --> gamma gamma of the Higgs boson at the Large Hadron Collider, where charginos, as surviving light fermions of the supersymmetric spectrum, can contribute in the loop. We perform a detailed study of uncertainties in various parameters involved in the analysis, and thus the net uncertainty in the standard model prediction of the rate. After a thorough scan of the parameter space, taking all constraints into account, we conclude that it will be very difficult to infer about split supersymmetry from Higgs signals alone. Read More

In the recently proposed `split supersymmetry' scenario, the squark and slepton masses are allowed to be at a high scale while the gauginos and Higgsinos are within a TeV. We show that in a theory with broken R-parity, the parameter space of such a scenario allows a situation where the lightest neutralino is still stable on the cosmological scale and can be a dark matter candidate. We also separate the cases where (a) it may be invisible but not a dark matter candidate, or (b) it may decay showing a displaced vertex. Read More