arXiv subjects

S. K. Singh

Publications and source records attributed to S. K. Singh.

At least 55 records · Page 3Linked to original sources

arXiv2022

Charged current (anti)neutrino induced eta production off the nucleon

The charged current (anti)neutrino induced eta production from the nucleons is studied in a model based on the effective Lagrangians to evaluate the contribution from the nonresonant and resonant diagrams. The contribution from the nonresonant background terms has been obtained using a microscopic model based on the SU(3) chiral Lagrangians. The contribution from the resonant diagrams due to the low lying $S_{11}(1535)$, $S_{11} (1650)$, and $P_{11} (1710)$ resonances has been evaluated using an effective phenomenological Lagrangian with its parameters determined from the experimental values of their branching ratios and decay widths to the $Nη$ channel. The model is first used to reproduce satisfactorily the experimental data from the MAINZ and JLab on the total cross sections for the photo- and electro- production of $η$ mesons, which fixes the model parameters in the vector current interaction. The PCAC hypothesis and generalized Goldberger-Treiman relation are used to fix the parameters of the axial vector interaction. The model is then applied to study the weak production of eta mesons induced by the neutrinos and antineutrinos, and predicts the numerical values for the $Q^2$-distribution, $η$-momentum distribution, and the total cross section for the reactions $ν_μ + n \longrightarrow μ^{-} + p + η$ and $\barν_μ + p \longrightarrow μ^+ + n + η$ in the energy region up to 2 GeV. It is found that the photo, electro, and (anti)neutrino production of eta mesons is dominated by the contribution from the $S_{11}(1535)$ resonance. The results discussed in this work are relevant for the present and future accelerator experiments like MicroBooNE, T2K, NOvA, MINERvA, T2-HyperK and DUNE as well as for the atmospheric neutrino experiments.

hep-ph↗

arXiv2022

Strong photon antibunching effect in a double cavity optomechanical system with intracavity squeezed light

We study the behaviour of the second-order correlation function in a double cavity optomechanical system and a degenerate optical parametric amplifier (OPA) is placed in each cavity. The first cavity is additionally driven by a weak classical laser field. The occurrence of strong photon antibunching effect in these two coupled cavities is observed. For suitable values of optomechanical coupling strength as well as photon hopping process, the system can exhibit a very strong photon antibunching effect. Our study also shows that the unconventional photon blockade occurs in both coupling, i.e. the weak coupling as well as in the strong coupling regimes as compared to the conventional photon blockade which occurs only in the strong coupling regime. We get a very strong photon antibunching effect under the unconventional photon blockade mechanism than the conventional photon blockade mechanism. Our study can be also used for the generation of single photon in coupled nonlinear optomechanical systems.

quant-ph↗

arXiv2022

User Association in Dense mmWave Networks as Restless Bandits

We study the problem of user association, i.e., determining which base station (BS) a user should associate with, in a dense millimeter wave (mmWave) network. In our system model, in each time slot, a user arrives with some probability in a region with a relatively small geographical area served by a dense mmWave network. Our goal is to devise an association policy under which, in each time slot in which a user arrives, it is assigned to exactly one BS so as to minimize the weighted average amount of time that users spend in the system. The above problem is a restless multi-armed bandit problem and is provably hard to solve. We prove that the problem is Whittle indexable, and based on this result, propose an association policy under which an arriving user is associated with the BS having the smallest Whittle index. Using simulations, we show that our proposed policy outperforms several user association policies proposed in prior work.

cs.IT↗

arXiv2022

Nuclear medium effects in the deep inelastic $ν_τ/\barν_τ-^{40}Ar$ scattering at DUNE energies

The nuclear medium effects are studied in the $ν_τ/\barν_τ$ interactions from nuclei in the deep inelastic scattering (DIS) region and applied to the $^{40}Ar$ nucleus to obtain the scattering cross sections in the energy region of the proposed DUNE experiment. The free nucleon structure functions ($F_{iN}(x,Q^2);~(i=1-5)$) have been calculated at the next-to-leading order (NLO) using Martin-Motylinski-Harland Lang-Thorne 2014 as well as The Coordinated Theoretical-Experimental Project on QCD parameterizations for parton distribution functions (PDFs) and including the effect of perturbative and nonperturbative QCD corrections \cite{Ansari:2020xne}. These free nucleon structure functions are then convoluted with the nucleon spectral function in the nucleus to obtain the nuclear structure functions ($F_{iA}(x,Q^2);~(i=1-5)$). The nucleon spectral function takes into account the Fermi motion and the binding energy of the nucleons as well as the nucleon correlations within the nucleus. These nuclear structure functions are then used to calculate the deep inelastic scattering cross sections. Moreover, the contribution of $π$ and $ρ$ mesons as well as the corrections due to the shadowing and antishadowing effects in the relevant kinematic region of the Bjorken variable $x$ are also included. The numerical results for the cross sections have been presented and compared with the results obtained in the phenomenological approach using nuclear structure functions from nCTEQnu.

nucl-th↗

arXiv2022

Record-quality GaAs two-dimensional hole systems

The complex band structure, large spin-orbit induced band splitting, and heavy effective mass of two-dimensional (2D) hole systems hosted in GaAs quantum wells render them rich platforms to study many-body physics and ballistic transport phenomena. Here we report ultra-high-quality (001) GaAs 2D hole systems, fabricated using molecular beam epitaxy and modulation doping, with mobility values as high as $5.8\times10^6$ cm$^2$/Vs at a hole density of $p=1.3\times10^{11}$ /cm$^2$, implying a mean-free path of $\simeq27$ $μ$m. In the low-temperature magnetoresistance trace of this sample, we observe high-order fractional quantum Hall states up to the Landau level filling $ν=12/25$ near $ν=1/2$. Furthermore, we see a deep minimum develop at $ν=1/5$ in the magnetoresistance of a sample with a much lower hole density of $p=4.0\times10^{10}$ /cm$^2$ where we measure a mobility of $3.6\times10^6$ cm$^2$/Vs. These improvements in sample quality were achieved by reduction of residual impurities both in the GaAs channel and the AlGaAs barrier material, as well as optimization in design of the sample structure.

cond-mat.mes-hall↗

arXiv2022

An Automated Pipeline for Ultra-Violet Imaging Telescope (UVIT)

We describe a versatile pipeline for processing the data collected by the Ultra-Violet Imaging Telescope (UVIT) on board Indian Multi-wavelength astronomical satellite AstroSat.The UVIT instrument carries out simultaneous astronomical imaging through selected filters / gratings in Far-Ultra-Violet (FUV), Near-Ultra-Violet & visible (VIS) bands of the targeted circular sky field (~ 0.5 deg dia). This pipeline converts the data (Level-1) emanating from UVIT in their raw primitive format supplemented by inputs from the spacecraft sub-systems into UV sky images (& slitless grating spectra) and associated products readily usable by astronomers (Level-2). The primary products include maps of Intensity (rate of photon arrival), error on Intensity and effective Exposure. The pipeline is open source, extensively user configurable with many selectable parameters and its execution is fully automated. The key ingredients of the pipeline includes - extraction of drift in pointing of the spacecraft, and disturbances in pointing due to internal movements; application of various corrections to measured position in the detector for each photon - e.g. differential pointing with respect to a reference frame for shift and add operation, systematic effects and artifacts in the optics of the telescopes and detectors, exposure tracking on the sky, alignment of sky products from multi-episode exposures to generate a consolidated set and astrometry. Detailed logs of operations and intermediate products for every processing stage are accessible via user selectable options. While large number of selectable parameters are available for the user, a well characterized standard default set is used for executing this pipeline at the Payload Operation Centre (POC) for UVIT and selected products are archived and disseminated by the Indian Space Research Organization (ISRO) through its ISSDC portal.

astro-ph.IM↗

arXiv2022

Nuclear medium effects in lepton-nucleus DIS in the region of $x \gtrsim 1$

The nuclear medium effects in the nuclear structure functions and differential cross sections in the deep inelastic scattering (DIS) of charged lepton and neutrino from nuclear targets are studied in the region of large $x$ including $x\ge 1$. The nuclear medium effects due to the Fermi motion and the binding energy of nucleons and the nucleon correlations are included using nucleon spectral function calculated in a microscopic field theoretical model. The numerical results for the nuclear structure functions and the cross sections are obtained using the nucleon structure function evaluated at the next-to-next-to-leading order (NNLO) with the Martin-Motylinski-Harland Lang-Thorne (MMHT) parameterization of the nucleonic parton distribution functions (PDFs) and are compared with the available experimental data on electron scattering from the Jefferson Lab (JLab) and SLAC Nuclear Physics Facility (NPAS). In the case of neutrino scattering the results are relevant for understanding the DIS contributions to the recent inclusive cross sections measured by the Main Injector Neutrino ExpeRiment to study v-A interactions (MINERvA) as well as theoretical predictions are made for Deep Underground Neutrino Experiment (DUNE). The importance of isoscalarity corrections in heavier nuclear targets as well as the effect of the kinematic cut on the CM energy $W$ in defining the DIS region have also been discussed.

hep-ph↗

arXiv2022

Enhanced weak force sensing through atom-based coherent noise cancellation in a hybrid cavity optomechanical system

We investigate weak force-sensing based on coherent quantum noise cancellation in a nonlinear hybrid optomechanical system. The optomechanical cavity contains a moveable mechanical mirror, a fixed semitransparent mirror, an ensemble of ultracold atoms, and an optical parametric amplifier (OPA). Using the coherent quantum noise cancellation (CQNC) process, one can eliminate the back action noise at all frequencies. Also by tuning the OPA parameters, one can suppress the quantum shot-noise at lower frequencies than the resonant frequency. In the CQNC scheme, the damping rate of the mechanical oscillator matches the damping rate of the atomic ensemble, which is experimentally achievable even for a low-frequency mechanical oscillator with a high-quality factor. Elimination of the back action noise and suppression of the shot noise significantly enhance force sensing and thus overcome the standard quantum limit of weak force sensing. This hybrid scheme can play an essential role in the realization of quantum optomechanical sensors and quantum control.

quant-ph↗

arXiv2022

Hyperon production in quasielastic $\barν_τ-$nucleon scattering

The theoretical results for the total cross sections and polarization components of the $τ^{+}$ lepton produced in the charged current induced $|ΔS| = 1$ quasielastic $\barν_τ- N$ scattering leading to hyperons ($Λ, Σ$) have been presented assuming T invariance. The theoretical uncertainties arising due to the use of different vector, axial vector and pseudoscalar form factors as well as the effect of SU(3) symmetry breaking have been studied. We have also presented, for the first time, a comparison of the total cross sections for the production of $e,μ,τ$ leptons to facilitate the implications of lepton flavor universality~(LFU) in the $|ΔS| = 1$ quasielastic reactions induced by the antineutrinos of all flavors i.e., $ν_{l};~l=e,μ,τ$.

hep-ph↗

arXiv2021

Rivet, RivetHZTool and HERA -- A validation effort for coding HERA measurements for Rivet

During the DESY summer student program 2021, young scientists from more than 13 different countries worked together, connecting from remote, to provide computer codes within the Rivet framework for 19 HERA measurements. Most of these measurements were originally available within the HZTool package, but no longer accessible for modern analysis packages such as Rivet. The temporary RivetHZTool interface was used to validate most of the new Rivet plugins.

hep-ph↗

arXiv2021

T-violating effect in $ν_τ (\barν_τ)-$nucleon quasielastic scattering

The production cross sections and polarization observables of the $τ$ leptons produced in the $|ΔS| = 0$ and $1$ induced $ν_τ(\barν_τ)-N$ quasielastic scattering have been studied. The effect of T violation, in the case of $ΔS=0$ and 1 processes, and the SU(3) symmetry breaking effects, in the case of $ΔS=1$ processes, on the total scattering cross sections as well polarization observables are explored. Experimentally, it would be possible to observe these effects in the forthcoming (anti)neutrino experiments like DUNE, SHiP and DsTau.

hep-ph↗

arXiv2021

Neutrinos and their interactions

We present a short overview of the importance of the study of "Neutrino Interactions in the Intermediate and High Energy Region", with an introduction to the neutrinos and a very brief description about the collection of invited articles.

hep-ph↗

arXiv2021

Interplay of Bound Magnetic Polaron and p-d exchange interaction in Co-doped 3C-SiC

Bound Magnetic Polarons (BMP) have been proposed to play an important role in doped wide band gap semiconductors. We report the experimental evidence supporting polaronic magnetism and the role of defects on it. Temperature variation of electron paramagnetic resonance study reveals that the valence state of cobalt is 2+ and its nearest environment in the system is distorted tetrahedral in nature. Room temperature ferromagnetism have been found in all the doped [Co (1, 3, 5) % doped 3C-SiC] samples. The Curie temperature, TC of the samples have been found to be above 800 K. The isothermal magnetization plots, to determine the strength of domain wall pinning were analyzed using the Jiles-Atherton Model. The temperature variation of the anisotropic constant was determined using Law of Approach to saturation (LAS), which decreases with increase in temperature. Quantitative analysis of magnetic interaction has been carried out and the result is explained by using BMP Model, which probably arises out of the exchange interaction of Co2+ ions with related (Si, C) defects.

cond-mat.mtrl-sci↗

arXiv2021

F+ Center Exchange Mechanism and Magneto Crystalline Anisotropy in Ni doped 3C-SiC

We report the experimental evidence in support of room temperature ferromagnetism in Ni doped 3C-SiC. Curie temperature is found to be > 350 K. Temperature dependent Electron paramagnetic resonance (EPR) study reveals that the valence state of Ni is 2+ and its environmental symmetry. A clear shift in both XRD and Raman peak confirms the incorporation of Ni in the host lattice. The variation in number of vacancies $V_{\mathrm{Si}}$, $V_{\mathrm{C}}$ and the number of free electron due to doping is consistent with the change in magnetization of the system. A direct correlation of ferromagnetic order (FM) with F+ centers exchange mechanism is established. The temperature variation of the anisotropic constant was determined using Law of Approach to Saturation (LAS). It was found that effective magnetic anisotropic constant decreases with increase in temperature. The EPR line width of the annealed sample increases with decrease in temperature, whereas the integrated intensity decreases with decrease in temperature. This could be due to incomplete quenching of orbital angular momentum in Si$_{x}$Ni$_{1-x}$C. In addition to this, the orbital degeneracy of fast relaxing impurity such as Ni in the cubic crystal field is not completely removed. This results in the line width decrease with increase in temperature.

cond-mat.mtrl-sci↗

arXiv2021

Melting phase diagram of bubble phases in high Landau levels

A low-disorder, two-dimensional electron system (2DES) subjected to a large perpendicular magnetic field and cooled to very low temperatures provides a rich platform for studies of many-body quantum phases. The magnetic field quenches the electrons' kinetic energy and quantizes the energy into a set of Landau levels, allowing the Coulomb interaction to dominate. In excited Landau levels, the fine interplay between short- and long-range interactions stabilizes bubble phases, Wigner crystals with more than one electron per unit cell. Here we present the screening properties of bubble phases, probed via a simple capacitance technique where the 2DES is placed between a top and a bottom gate and the electric field penetrating through the 2DES is measured. The bubbles formed at very low temperatures screen the electric field poorly as they are pinned by the residual disorder potential, allowing a large electric field to reach the top gate. As the temperature is increased, the penetrating electric field decreases and, surprisingly, exhibits a pronounced minimum at a temperature that appears to coincide with the melting temperature of the bubble phase. We deduce a quantitative phase diagram for the transition from bubble to liquid phases for Landau level filling factors $4\leqν\leq5$.

cond-mat.mes-hall↗

arXiv2021

$\barν_μ$ induced quasielastic production of hyperons leading to pions

The quasielastic production cross sections and polarizations of the hyperons induced by ${\barν}_μ$ on the free nucleon as well as from $^{40}$Ar in the sub-GeV energy region has been reviewed [1-5]. The effects of the second class currents in the axial vector sector with and without T-invariance as well as the effect of SU(3) symmetry breaking are also studied. We find that the cross sections and the various polarization components can effectively be used to determine the axial vector transition form factors in the strangeness sector and to test the validity of various symmetries of the weak hadronic currents like G-invariance, T-invariance and SU(3) symmetry. These hyperons decay dominantly into pions giving an additional contribution to the weak pion production induced by the antineutrinos. In the case of nuclear targets like $^{40}$Ar, this contribution is shown to be significant when compared with the pion production by the $Δ$ excitations in the energy range of $E_{\barν_μ} \le 0.7$ GeV [1]. This study could be useful for the DUNE experiment where argon will be used as the target material and the electronic imaging of particles is possible and the particle tracks can be identified.

hep-ph↗

arXiv2021

Deep inelastic (anti)neutrino-nucleus scattering

The present status of the field theoretical model studies of the deep inelastic scattering induced by (anti)neutrino on the nuclear targets in a wide range of Bjorken variable $x$ and four momentum transfer square $Q^2$, has been reviewed~\cite{Haider:2011qs,Haider:2012nf,Haider:2016zrk,Zaidi:2019mfd,Zaidi:2019asc,Ansari:2020xne}. The effect of the nonperturbative corrections such as target mass correction and higher twist effects, perturbative evolution of the parton densities, nuclear medium modifications in the nucleon structure functions, nuclear isoscalarity corrections on the weak nuclear structure functions have been discussed. These structure functions have been used to obtain the differential scattering cross sections. The various nuclear medium effects like the Fermi motion, binding energy, nucleon correlations, mesonic contributions, shadowing and antishadowing corrections relevant in the different regions of $x$ and $Q^2$ have been discussed. The numerical results for the structure functions and the cross sections are compared with some of the available experimental data including the recent results from MINERvA. The predictions are made in argon nuclear target which is planned to be used as a target material in DUNE at the Fermilab.

hep-ph↗

arXiv2021

The low energy inclusive $ν_μ (ν_{e})-^{12}$C scattering revisited

We have reviewed the current status of the inclusive neutrino scattering from $^{12}$C in the low energy region corresponding to the neutrino beams from the pion, muon and kaon decaying at rest. The theoretical calculations of total cross sections in various nuclear models with special emphasis on the recent experiments with the monoenergetic neutrinos from KDAR [1] along with the older experiments from KARMEN and LSND collaborations have been discussed in the context of the recent works by Akbar et al. [2] and Nikolakopoulos et al. [3]. The inadequacy of the various theoretical models used to explain the experimental results on the inclusive neutrino scattering from nuclei at low energies has been highlighted and the need for a better understanding of the nuclear medium effects beyond the impulse approximation has been emphasized.

hep-ph↗