arXiv subjects

Utpal Chattopadhyay

Publications and source records attributed to Utpal Chattopadhyay.

At least 37 records · Page 2Linked to original sources

arXiv2014

The Electroweak Sector of the pMSSM in the Light of LHC - 8 TeV and Other Data

Using the chargino-neutralino and slepton search results from the LHC in conjunction with the WMAP/PLANCK and $(g-2)_μ$ data, we constrain several generic pMSSM models with decoupled strongly interacting sparticles, heavier Higgs bosons and characterized by different hierarchies among the EW sparticles. We find that some of them are already under pressure and this number increases if bounds from direct detection experiments like LUX are taken into account, keeping in mind the associated uncertainties. The XENON1T experiment is likely to scrutinize the remaining models closely. Analysing models with heavy squarks, a light gluino along with widely different EW sectors, we show that the limits on gluino mass are not likely to be below 1.1 TeV, if a multichannel analysis of the LHC data is performed. Using this light gluino scenario we further illustrate that in future LHC experiments the models with different EW sectors can be distinguished from each other by the relative sizes of the $n$-leptons + $m$-jets + ${\mbox{${E\!\!\!\!/_T}$}}$ signals for different choices of $n$.

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arXiv2013

Implications of 98 GeV and 125 GeV Higgs scenario in non-decoupling SUSY with updated ATLAS, CMS and PLANCK data

We discuss both MSSM and NMSSM scenarios in which the lightest Higgs boson with $m_h=98$~GeV is consistent with the small excess ($\sim 2.3 σ$) observed at the LEP in $e^+ e^-\rightarrow Zh$, with $h \rightarrow b {\bar b}$ process and the heavier Higgs boson of mass close to 125~GeV as the observed candidate of the SM Higgs like particle at the LHC. We show the allowed regions in the non-decoupling Higgs zone of MSSM parameter space which are consistent with several low energy constraints coming from heavy flavour physics, latest experimental data on Higgs signals and lower limit on superparticle masses from 7~TeV and 8~TeV LHC run. We also implement the constraints from the relic density of the cold dark matter as obtained from the recent PLANCK data. Additionally, we discuss the possibility of observing the light Higgs boson of mass 98~GeV at the 14~TeV LHC run via $pp \rightarrow V h$, with $h \rightarrow b \bar b$ using the technique of jet substructure. Our analysis shows that at 14~TeV LHC run with 300 ${\rm fb}^{-1}$ luminosity the signal efficiency of such a light Higgs boson is at most 2.5$σ$. Finally, we make a comment on the prospect of proposed $e^+ e^-$ ILC to discover/exclude this light Higgs boson.

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arXiv2013

Implication of Higgs at 125 GeV within Stochastic Superspace Framework

We revisit the issue of considering stochasticity of Grassmannian coordinates in N=1 superspace, which was analyzed previously by Kobakhidze {\it et al}. In this stochastic supersymmetry(SUSY) framework, the soft SUSY breaking terms of the minimal supersymmetric Standard Model(MSSM) such as the bilinear Higgs mixing, trilinear coupling as well as the gaugino mass parameters are all proportional to a single mass parameter ξ, a measure of supersymmetry breaking arising out of stochasticity. While a nonvanishing trilinear coupling at the high scale is a natural outcome of the framework, a favorable signature for obtaining the lighter Higgs boson mass $m_h$ at 125 GeV, the model produces tachyonic sleptons or staus turning to be too light. The previous analyses took $Λ$, the scale at which input parameters are given, to be larger than the gauge coupling unification scale $M_G$ in order to generate acceptable scalar masses radiatively at the electroweak scale. Still this was inadequate for obtaining $m_h$ at 125 GeV. We find that Higgs at 125 GeV is highly achievable provided we are ready to accommodate a nonvanishing scalar mass soft SUSY breaking term similar to what is done in minimal anomaly mediated SUSY breaking (AMSB) in contrast to a pure AMSB setup. Thus, the model can easily accommodate Higgs data, LHC limits of squark masses, WMAP data for dark matter relic density, flavor physics constraints and XENON100 data. In contrast to the previous analyses we consider $Λ=M_G$, thus avoiding any ambiguities of a post-grand unified theory physics. The idea of stochastic superspace can easily be generalized to various scenarios beyond the MSSM . PACS Nos: 12.60.Jv, 04.65.+e, 95.30.Cq, 95.35.+d

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arXiv2010

Probing the light Higgs pole resonance annihilation of dark matter in the light of XENON100 and CDMS-II observations

We consider the prospect of lightest neutralino (${\tilde χ}_1^0$) as a dark matter candidate in the light of recent interesting observations from the XENON100 and CDMS-II experiments in minimal supergravity framework with large $\tanβ$ and non-vanishing $A_0$. Within the WMAP satisfied zone, there is a large direct detection reach of lighter ${\tilde χ}_1^0$ in the lighter Higgs boson mediated resonance annihilation domain of the above scenario. It is seen that the heavier Higgs boson plays a dominating role in the ${\tilde χ}_1^0-p$ cross-section in the associated zone of parameter space in spite of having a larger mass. Possible LHC signatures are discussed.

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arXiv2010

Non-universal scalar mass scenario with Higgs funnel region of SUSY dark matter: a signal-based analysis for the Large Hadron Collider

We perform a multilepton channel analysis in the context of the Large Hadron Collider (LHC) for Wilkinson Microwave Anisotropy Probe (WMAP) compatible points in a model with non-universal scalar masses, which admits a Higgs funnel region of supersymmetry dark matter even for a small $\tanβ$. In addition to two and three-lepton final states, four-lepton events, too, are shown to be useful for this purpose. We also compare the collider signatures in similar channels for WMAP compatible points in the minimal supergravity (mSUGRA) framework with similar gluino masses. Some definite features of such non-universal scenario emerge from the analysis.

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arXiv2009

Mixed Neutralino Dark Matter in Nonuniversal Gaugino Mass Models

We have considered nonuniversal gaugino mass models of supergravity, arising from a mixture of two superfield contributions to the gauge kinetic term, belonging to a singlet and a nonsinglet representation of the GUT group. In particular we analyse two models, where the contributing superfields belong to the singlet and the 75-dimensional, and the singlet and the 200-dimensional representations of SU(5). The resulting lightest superparticle is a mixed bino-higgsino state in the first case and a mixed bino-wino-higgsino state in the second. In both cases one obtains cosmologically compatible dark matter relic density over broad regions of the parameter space. We predict promising signals in direct dark matter detection experiments as well as in indirect detection experiments via high energy neutrinos coming from their pair-annihilation in the Sun. Besides, we find interesting $γ$-ray signal rates that will be probed in the Fermi Gamma-ray Space Telescope. We also expect promising collider signals at LHC in both cases.

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arXiv2009

Higgs funnel region of SUSY dark matter for small $\tanβ$ and renormalization group effects on pseudoscalar Higgs boson with scalar mass non-universality

A non-universal scalar mass supergravity type of model is explored where the first two generation of scalars and the third generation of sleptons may be very massive. Lighter or vanishing third generation of squarks as well as Higgs scalars at the unification scale cause the radiative electroweak symmetry breaking constraint to be less prohibitive. Thus, both FCNC/CP-violation problems as well as the naturalness problem are within control. We identify a large slepton mass effect in the RGE of $m_{H_D}^2$ (for the down type of Higgs) that may turn the later negative at the electroweak scale even for a small $\tanβ$. A hyperbolic branch/focus point like effect is found for $m_A^2$ that may result in very light Higgs spectra. The lightest stable particle is dominantly a bino that pair annihilates via Higgs exchange, giving rise to a WMAP satisfied relic density region for all $\tanβ$. Detection prospects of such LSPs in the upcoming dark matter experiments both of direct and indirect types (photon flux) are interesting. The Higgs bosons and the third generation of squarks are light in this scenario and these may be easily probed besides charginos and neutralinos in the early runs of LHC.

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arXiv2007

Non-zero trilinear parameter in the mSUGRA model - dark matter and collider signals at Tevatron and LHC

Phenomenologically viable and interesting regions of parameter space in the minimal super-gravity (mSUGRA) model with small $m_0$ and small $m_{1/2}$ consistent with the WMAP data on dark matter relic density and the bound on the mass of the lightest Higgs scalar $ m_h>$ 114 GeV from LEP2 open up if the rather adhoc assumption $A_0$=0, where $A_0$ is the common trilinear soft breaking parameter, employed in most of the existing analyses is relaxed. Since this region corresponds to relatively light squarks and gluinos which are likely to be probed extensively in the very early stages of the LHC experiments, the consequences of moderate or large negative values of $A_0$ are examined in detail. We find that in this region several processes including lightest supersymmetric particle (LSP) pair annihilation, LSP - lighter tau slepton (${\tilde τ}_1$) coannihilation and LSP - lighter top squark (${\tilde t}_1$) coannihilation contribute to the observed dark matter relic density. %\sout{The possibility that a relic density producing ${\tilde t}_1$ can be %observed at the current experiments at the Tevatron is wide open.} The possibility that a ${\tilde t}_1$ that can participate in coannihilation with the lightest neutralino to satisfy the WMAP bound on relic density and at the same time be observed at the current experiments at the Tevatron is wide open. At the LHC a large number of squark - gluino events lead to a very distinctive semi-inclusive signature $τ^\pm$+X$_τ$ (anything without a tau lepton) with a characteristic size much larger than $e^\pm$+X$_e$ or $μ^\pm$+X$_μ$ events.

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arXiv2007

Looking for a heavy wino LSP in collider and dark matter experiments

We investigate the phenomenology of a wino LSP as obtained in AMSB and some string models. The WMAP constraint on the DM relic density implies a wino LSP mass of 2.0-2.3 TeV. We find a viable signature for such a heavy wino at CLIC, operating at its highest CM energy of 5 TeV. One also expects a viable monochromatic $γ$-ray signal from its pair-annihilation at the galactic centre at least for cuspy DM halo profiles.

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arXiv2005

Large evolution of the bilinear Higgs coupling parameter in SUSY models and reduction of phase sensitivity

The phases in a generic low-energy supersymmetric model are severely constrained by the experimental upper bounds on the electric dipole moments of the electron and the neutron. Coupled with the requirement of radiative electroweak symmetry breaking, this results in a large degree of fine tuning of the phase parameters at the unification scale. In supergravity type models, this corresponds to very highly tuned values for the phases of the bilinear Higgs coupling parameter $B$ and the universal trilinear coupling $A_0$. We identify a cancellation/enhancement mechanism associated with the renormalization group evolution of $B$, which, in turn, reduces such fine-tuning quite appreciably without taking recourse to very large masses for the supersymmetric partners. We find a significant amount of reduction of this fine-tuning in nonuniversal gaugino mass models that do not introduce any new phases.

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arXiv2005

Looking for a Heavy Higgsino LSP in Collider and Dark Matter Experiments

A large part of the mSUGRA parameter space satisfying the WMAP constraint on the dark matter relic density corresponds to a higgsino LSP of mass $\simeq 1$ TeV. We find a promising signal for this LSP at CLIC, particularly with polarized electron and positron beams. One also expects a viable monochromatic $γ$-ray signal from its pair annihilation at the galactic center at least for cuspy DM halo profiles. All these results hold equally for the higgsino LSP of other SUSY models like the non-universal scalar or gaugino mass models and the so-called inverted hierarchy and more minimal supersymmetry models.

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arXiv2005

Testing SUGRA Models

A brief review is given of the ways of testing SUGRA unified models and a class of string models using data from precision electroweak experiments, Yukawa unification constraints, and constraints from dark matter experiments. Models discussed in detail include mSUGRA, extended SUGRA model with non-universalities within SO(10) grand unification, and effective theories with modular invariant soft breaking within a generic heterotic string framework. The implications of the Hyperbolic Branch including the focus point and inversion regions for the discovery of supersymmetry in collider experiments and for the detection of dark matter in the direct detection experiments are also discussed.

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arXiv2004

Upper limits on sparticle masses from WMAP dark matter constraints with modular invariant soft breaking

An analysis of dark matter within the framework of modular invariant soft breaking is given. In such scenarios inclusion of the radiative electroweak symmetry breaking constraint determines $\tanβ$ which leads to a more constrained analysis. It is shown that for $μ$ positive for this constrained system the WMAP data leads to upper limits on sparticle masses that lie within reach of the LHC with also the possibility that some sparticles may be accessible at RUNII of the Tevatron.

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arXiv2004

Summary of the Activities of the Working Group I on High Energy and Collider Physics

This is a summary of the projects undertaken by the Working Group I on High Energy Collider Physics at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8) held at the Indian Institute of Technology, Mumbai, January 5-16, 2004. The topics covered are (i) Higgs searches (ii) supersymmetry searches (iii) extra dimensions and (iv) linear collider.

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arXiv2004

Modular Invariant Soft Breaking, WMAP, Dark Matter and Sparticle Mass Limits

An analysis of soft breaking under the constraint of modular invariance is given. The role of dilaton and moduli dependent front factors in achieving a modular invariant $V_{soft}$ is emphasized. Further, it is shown that in string models $\tanβ$ is no longer a free parameter but is determined in terms of $α_{string}$ and the other soft parameters by the constraints of modular invariance and radiative electroweak symmetry breaking. The above framework is then used to analyze the neutralino relic density consistent with the WMAP data at self dual points in the Kahler and complex structure moduli. One finds that the combined set of constraints arising from modular invariant soft breaking, radiative electroweak symmetry breaking and WMAP lead to upper limits on sparticle masses for $μ>0$. These limits are investigated for a class of models and found to lie within reach of the Tevatron and of the Large Hadron Collider (LHC). Further, an analysis of the neutralino-proton cross section shows that dark matter in these models can be explored in CDMS (Soudan), GENIUS and ZEPLIN. While the analysis is carried out within the general framework of heterotic strings, the possibility that the results of the analysis may extend to a broader class of string models, such as models based on intersecting D branes, is also discussed.

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arXiv2003

WMAP Data and Recent Developments in Supersymmetric Dark Matter

A brief review is given of the recent developments in the analyses of supersymmetric dark matter. Chief among these is the very accurate determination of the amount of cold dark matter in the universe from analyses using WMAP data. The implications of this data for the mSUGRA parameter space are analyzed. It is shown that the data admits solutions on the hyperbolic branch (HB) of the radiative breaking of the electroweak symmetry. A part of the hyperbolic branch lies in the so called inversion region where the LSP neutralino $χ_1^0$ becomes essentially a pure Higgsino and degenerate with the next to the lightest neutralino $χ_2^0$ and the light chargino $χ_1^{\pm}$. Thus some of the conventional signals for the observation of supersymmetry at colliders (e.g., the missing energy signals) do not operate in this region. On the other hand the inversion region contains a high degree of degeneracy of $χ_1^0$, $χ_2^0$, $χ_1^{\pm}$ leading to coannihilations which allow for the satisfaction of the WMAP relic density constraints deep on the hyperbolic branch. Further, an analysis of the neutralino-proton cross sections in this region reveals that this region can still be accessible to dark matter experiments in the future. Constraints from $g_μ-2$ and from $B^0_s\to μ^+μ^-$ are discussed. Future prospects are also discussed.

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arXiv2003

WMAP Constraints, SUSY Dark Matter and Implications for the Direct Detection of SUSY

Recently, WMAP has measured the cosmological parameters to a much greater accuracy. We analyze the implications of this more precise measurement for supersymmetric dark matter and for the direct detection of supersymmetry at accelerators. We consider mSUGRA including also the hyperbolic branch in the radiative breaking of the electroweak symmetry. On the part of the hyperbolic branch where the lightest neutralino is dominantly a higgsino rather than being mostly a bino, the relic density constraints are satisfied by coannihilation with the next lightest neutralino and the light chargino. Including this branch the lightest neutralino mass satisfies $m_{χ_1^0}\leq 1200$ GeV for $\tanβ\leq 50$. Constraints of $b\to s+γ$ and of $g_μ-2$ are also analyzed. It is shown that the neutralino-proton cross section in each case will fall within the reach of dark matter experiments. Possibility for the direct detection of supersymmetry is discussed in the allowed regions of the parameter space consistent with WMAP constraints. A brief discussion of the hyperbolic branch and focus point region (HB/FP) is also given.

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arXiv2003

Higgsino Dark Matter in a SUGRA Model with Nonuniversal Gaugino Masses

We study a specific SUGRA model with nonuniversal gaugino masses as an alternative to the minimal SUGRA model in the context of supersymmetric dark matter. The lightest supersymmetric particle in this model comes out to be a Higgsino dominated instead of a bino dominated lightest neutralino. The thermal relic density of this Higgsino dark matter is somewhat lower than the cosmologically favoured range, which means it may be only a subdominant component of the cold dark matter. Nonetheless, it predicts favourable rates of indirect detection, which can be seen in square-km size neutrino telescopes.

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