arXiv subjects

Bhaskar Dutta

Publications and source records attributed to Bhaskar Dutta.

At least 145 records · Page 8Linked to original sources

arXiv2016

Sensitivity to Z-prime and non-standard neutrino interactions from ultra-low threshold neutrino-nucleus coherent scattering

We discuss prospects for probing Z-prime and non-standard neutrino interactions using neutrino-nucleus coherent scattering with ultra-low energy (~ 10 eV) threshold Si and Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A&M University, and referencing available technology based upon economical and scalable detector arrays. For expected exposures, we show that sensitivity to the Z-prime mass is on the order of several TeV, and is complementary to the LHC search with low mass detectors in the near term. This technology is also shown to provide sensitivity to the neutrino magnetic moment, at a level that surpasses terrestrial limits, and is competitive with more stringent astrophysical bounds. We demonstrate the benefits of combining silicon and germanium detectors for distinguishing between classes of models of new physics, and for suppressing correlated systematic uncertainties.

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arXiv2016

Probing the Goldstone equivalence theorem in Heavy Weak Doublet Decays

This paper investigates the decays from heavy higgsino-like weak-doublets into Z, h bosons and missing particles. When pair-produced at the LHC, the subsequent Z, h to 2l, 2b decays in the doublet decay cascade can yield 4l, 2l 2b, and 4b + MET + jets final states. Mutual observation of any two of these channels would provide information on the the associated doublets' decay branching fractions into a Z or h, thereby probing the Goldstone equivalence relation, shedding additional light on the Higgs sector of beyond the Standard Model theories, and facilitating the discrimination of various contending models, in turn. We compare the Z/h decay ratio expected in the Minimal Supersymmetric model, the Next-to Minimal Supersymmetric model and a minimal singlet-doublet dark matter model. Additionally, we conduct a full Monte Carlo analysis of the prospects for detecting the targeted final states during 14 TeV running of the LHC in the context of a representative NMSSM benchmark model.

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arXiv2016

No $ν$ floors: Effective field theory treatment of the neutrino background in direct dark matter detection experiments

Distinguishing a dark matter interaction from an astrophysical neutrino-induced interaction will be major challenge for future direct dark matter searches. In this paper, we consider this issue within non-relativistic Effective Field Theory (EFT), which provides a well-motivated theoretical framework for determining nuclear responses to dark matter scattering events. We analyze the nuclear energy recoil spectra from the different dark matter-nucleon EFT operators, and compare to the nuclear recoil energy spectra that is predicted to be induced by astrophysical neutrino sources. We determine that for 11 of the 14 possible operators, the dark matter-induced recoil spectra can be cleanly distinguished from the corresponding neutrino-induced recoil spectra with moderate size detector technologies that are now being pursued, e.g., these operators would require 0.5 tonne years to be distinguished from the neutrino background for low mass dark matter. Our results imply that in most models detectors with good energy resolution will be able to distinguish a dark matter signal from a neutrino signal, without the need for much larger detectors that must rely on additional information from timing or direction.

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arXiv2016

Interpretation of the diphoton excess at CMS and ATLAS

We consider the diphoton resonance at the 13 TeV LHC in a consistent model with new scalars and vector-like fermions added to the Standard Model (SM), which can be constructed from orbifold grand unified theories and string models. The gauge coupling unification can be achieved, neutrino masses can be generated radiatively, and electroweak vacuum stability problem can be solved. To explain the diphoton resonance, we study a spin-0 particle, and discuss various associated final states.

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arXiv2016

Neutralinos and Sleptons at the LHC in Light of Muon $(g-2)_μ$

We study the muon $(g-2)_μ$ anomaly in light of neutralino dark matter and the LHC. We scan the MSSM parameters relevant to $(g-2)_μ$ and focus on three distinct cases with different neutralino compositions. We find that the 2$σ$ range of $(g-2)_μ$ requires the smuon ($\tildeμ_1$) to be lighter than $\sim$ 500 (1000) GeV for $\tan β=10\,(50)$. Correspondingly the two lightest neutralinos, $\tildeχ_{1}^0, \tildeχ_{2}^0$, have to be lighter than $\sim$ 300 (650) GeV and 900 (1000) GeV respectively. We explore the prospects of searching the light smuon and neutralinos at the LHC, in conjunction with constraints arising from indirect dark matter (DM) detection experiments. The upcoming run of the LHC will be able to set $95\%$ CL exclusion limit on $M_{\tildeχ_{2}^0}$ ($\sim 475 - 1300$ GeV) and $m_{\tilde{l}}$ ($\sim 670-775$ GeV) with $M_{\tildeχ_{1}^0} \sim 100-250$ GeV at 3000 fb$^{-1}$ luminosity in multi-lepton + missing energy channel.

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arXiv2015

Distinguishing Neutrino Mass Hierarchies using Dark Matter Annihilation Signals at IceCube

We explore the possibility of distinguishing neutrino mass hierarchies through the neutrino signal from dark matter annihilation at neutrino telescopes. We consider a simple extension of the standard model where the neutrino masses and mixing angles are obtained via the type-II seesaw mechanism as an explicit example. We show that future extensions of IceCube neutrino telescope may detect the neutrino signal from DM annihilation at the Galactic Center and inside the Sun, and differentiate between the normal and inverted mass hierarchies, in this model.

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arXiv2015

Confronting Galactic center and dwarf spheroidal gamma-ray observations with cascade annihilation models

Many particle dark matter models predict that the dark matter undergoes cascade annihilations, i.e. the annihilation products are 4-body final states. In the context of model-independent cascade annihilation models, we study the compatibility of the dark matter interpretation of the Fermi- LAT Galactic center gamma-ray emission with null detections from dwarf spheroidal galaxies. For canonical values of the Milky Way density profile and the local dark matter density, we find that the dark matter interpretation to the Galactic center emission is strongly constrained. However, uncertainties in the dark matter distribution weaken the constraints and leave open dark matter interpretations over a wide range of mass scales.

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arXiv2015

Probing Compressed Bottom Squarks with Boosted Jets and Shape Analysis

A feasibility study is presented for the search of the lightest bottom squark (sbottom) in a compressed scenario, where its mass difference from the lightest neutralino is 5 GeV. Two separate studies are performed: $(1)$ final state containing two VBF-like tagging jets, missing transverse energy, and zero or one $b$-tagged jet; and $(2)$ final state consisting of initial state radiation (ISR) jet, missing transverse energy, and at least one $b$-tagged jet. An analysis of the shape of the missing transverse energy distribution for signal and background is performed in each case, leading to significant improvement over a cut and count analysis, especially after incorporating the consideration of systematics and pileup. The shape analysis in the VBF-like tagging jet study leads to a $3σ$ exclusion potential of sbottoms with mass up to $530 \, (462)$ GeV for an integrated luminosity of $300$ fb$^{-1}$ at 14 TeV, with $5\%$ systematics and PU $= 0 \, (50)$.

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arXiv2015

Dilepton Mass Endpoint in the NMSSM

NMSSM scenarios are investigated to explain an excess in the opposite-sign dilepton mass distribution in events with dilepton, jets and missing transverse energy reported by the CMS experiment. We show that the NMSSM scenarios can possess unique features to explain this excess, and can be distinguished from the MSSM scenarios in the ongoing LHC runs as well as direct detection experiments.

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arXiv2015

The Leptoquark Implication from the CMS and IceCube Experiments

The recent excess in the CMS measurements of $eejj$ and $eνjj$ channels and the emergence of PeV comsic neutrino events at the IceCube experiment share an intriguing implication for a leptoquark with a 600-650 GeV mass. We investigate the CMS constraints on the flavor structure of a scenario with the minimal leptoquark Yukawa couplings and correlate such a scenario to the resonant enhancement in the very high energy shower event rates at the IceCube. We find for a single leptoquark, the CMS signals require large couplings to the third generation leptons. This leads to an enhancement in the $ν_τ$-nucleon scattering cross-section and subsequently more $ν_τ$ events at PeV energies. However, a visible enhancement above the Standard Model scattering would require a leptoquark Yukawa coupling larger than one that can be easily tested at the upcoming LHC runs.

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arXiv2015

Exploring the Doubly Charged Higgs of the Left-Right Symmetric Model using Vector Boson Fusion-like Events at the LHC

This paper studies the pair production of the doubly charged Higgs boson of the left-right symmetric models using multilepton final state in the vector boson fusion (VBF)-like processes. The study is performed in the framework consistent with the model's correction to the standard model $ρ_{EW}$ parameter. VBF topological cuts, number of leptons in the final state and $p_T$ cuts on the leptons are found to be effective in suppressing the background. Significant mass reach can be achieved for exclusion/discovery of the doubly charge Higgs boson for the upcoming LHC run with a luminosity of $\mathcal{O}(10^3)$ fb$^{-1}$.

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arXiv2015

Probing Compressed Sleptons at the LHC using Vector Boson Fusion Processes

The vector boson fusion (VBF) topology at the Large Hadron Collider at 14 TeV provides an opportunity to search for new physics. A feasibility study for the search of sleptons in a compressed mass spectra scenario is presented in the final state of two jets, one or two low $p_{T}$ non-resonant leptons, and missing energy. The presence of the VBF tagged jets and missing energy are effective in reducing Standard Model backgrounds. Using smuon production with a mass difference between $\tilde{l}_{L}$ and $\tildeχ_{1}^0$ of 5-15 GeV, the significance of observing the signal events is found to be $\sim$ 3-6$σ$ for $m_{\tilde{l}}$=115-135 GeV, considering an integrated luminosity of 3000 fb$^{-1}$.

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arXiv2015

Enhancement of Br(B_d -> mu^+mu^-)/Br(B_s -> mu^+mu^-) in Supersymmetric Unified Models

We explain the 2.3 sigma deviation in the recent measurements of the neutral B mesons decay into muon pairs from the standard model prediction in the framework of supersymmetric grand unified models using anti-symmetric coupling as a new source of flavor violation. We show a correlation between the B_d -> mu^+mu^- decay and the CP phase in the B_d -> J/psi K decay and that their deviations from the standard model predictions can be explained after satisfying constraints arising from various hadronic and leptonic rare decay processes, B-bar{B}, K-bar{K} oscillations data and electric dipole moments of electron and neutron. The allowed parameter space is typically represented by pseudoscalar Higgs mass m_A < 1 TeV and tan beta_H (= {v_u}/{v_d}) < 20 for squark and gluino masses around 2 TeV.

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arXiv2015

Non-thermal CMSSM with a 125 GeV Higgs

We study the phenomenology of the CMSSM/mSUGRA with non-thermal neutralino dark matter. Besides the standard parameters of the CMSSM we include the reheating temperature as an extra parameter. Imposing radiative electroweak symmetry breaking with a Higgs mass around 125 GeV and no dark matter overproduction, we contrast the scenario with different experimental bounds from colliders (LEP, LHC), cosmic microwave background (Planck), direct (LUX, XENON100, CDMS, IceCube) and indirect (Fermi) dark matter searches. The allowed parameter space is characterised by a Higgsino-like LSP with a mass around 300 GeV. The observed dark matter abundance can be saturated for reheating temperatures around 2 GeV while larger temperatures require extra non-neutralino dark matter candidates and extend the allowed parameter space. Sfermion and gluino masses are in the few TeV region. These scenarios can be achieved in string models of sequestered supersymmetry breaking which avoid cosmological moduli problems and are compatible with gauge coupling unification. Astrophysics and particle physics experiments will fully investigate this non-thermal scenario in the near future.

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arXiv2014

Dark Matter from Late Invisible Decays to/of Gravitinos

In this work, we sift a simple supersymmetric framework of late invisible decays to/of the gravitino. We investigate two cases where the gravitino is the lightest supersymmetric particle or the next-to-lightest supersymmetric particle. The next-to-lightest supersymmetric particle decays into two dark matter candidates and has a long lifetime due to gravitationally suppressed interactions. However, because of the absence of any hadronic or electromagnetic products, it satisfies the tight bounds set by big bang nucleosynthesis and cosmic microwaved background. One or both of the dark matter candidates produced in invisible decays can contribute to the amount of dark radiation and suppress perturbations at scales that are being probed by the galaxy power spectrum and the Lyman-alpha forest data. We show that these constraints are satisfied in large regions of the parameter space and, as a result, the late invisible decays to/of the gravitino can be responsible for the entire dark matter relic abundance.

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arXiv2014

Third Generation in Cascade Decays

In supersymmetric models with gluinos around 1000-2000 GeV, new physics searches based on cascade decay products of the gluino are viable at the next run of the LHC. We investigate a scenario where the light stop is lighter than the gluino and both are lighter than all other squarks, and show that its signal can be established using multi b-jet, multi W and/or multi lepton final state topologies. We then utilize both boosted and conventional jet topologies in the final state in conjunction with di-tau production as a probe of the stau-neutralino co-annihilation region responsible for the model's dark matter content. This study is performed in the specific context of one such phenomenologically viable model named No-Scale F-SU(5).

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arXiv2014

Light Higgsino Decays as a Probe of the NMSSM

In the Next-to Minimal Supersymmetric Standard Model (NMSSM), a sizable coupling $λ$ between the singlet and Higgs fields can naturally accommodate the observed Higgs boson mass of 125 GeV. This large coupling also results in a large separation between the Higgsino and singlino mass scales in the neutralino sector to evade stringent constraints from direct detection experiments. Most of the natural parameter space in this setup therefore contains light Higgsinos that can decay into the singlino and the 125 GeV Higgs. If the Higgsinos are to be light enough to be produced at the LHC, the mass gap $m_{\tildeχ^0_2} -(m_{\tildeχ^0_1} +m_h)$ is generally fairly low, resulting in small missing energy. We study the collider phenomenology of this process and demonstrate that the 4$b+j+{E\!\!\!\!/_{\rm T}}$ signal arising from $pp\rightarrow\tildeχ_i^0\tildeχ_j^0jj$ process can be a viable channel to search for this low mass gap region at the 14 TeV LHC. In addition, we find that a potential signal from the LHC search, in tandem with direct detection experiments, can distinguish the NMSSM from the analogous process in the MSSM, where the bino plays the role of the singlino, for positive values of the $μ$ parameter even when the additional singlet-dominated (pseudo)scalars are absent or indistinguishable from the Higgs in the decay.

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arXiv2014

3.5 keV X-ray line and R-Parity Conserving Supersymmetry

We present some R-parity conserving supersymmetric models which can accommodate the 3.5 keV X-ray line reported in recent spectral studies of the Perseus galaxy cluster and the Andromeda galaxy. Within the Minimal Supersymmetric Standard Model (MSSM) framework, the dark matter (DM) gravitino (or the axino) with mass of around 7 keV decays into a massless neutralino (bino) and a photon with lifetime ~10^{28} sec. The massless bino contributes to the effective number of neutrino species N_eff and future data will test this prediction. In the context of NMSSM, we first consider scenarios where the bino is massless and the singlino mass is around 7 keV. We also consider quasi-degenerate bino-singlino scenarios where the mass scale of DM particles are O(GeV) or larger. In such a scenario we require the mass gap to generate the 3.5 keV line. We comment on the possibility of a 7 keV singlino decaying via R parity violating couplings while all other neutralinos are heavy.

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