arXiv subjects

A. Ghosh

Publications and source records attributed to A. Ghosh.

At least 55 records · Page 3Linked to original sources

arXiv2022

Measurement of inclusive charged-current $ν_{\numu}$ scattering on hydrocarbon at { } 6 GeV with low three-momentum transfer

The \minerva experiment reports double-differential cross-section measurements for $ν_μ$-carbon interactions with three-momentum transfer $|\vec{q}| < 1.2$ GeV obtained with medium energy exposures in the NuMI beam. These measurements are performed as a function of the three-momentum transfer and an energy transfer estimator called the available energy defined as the energy that would be visible in the detector. The double differential cross sections are compared to the GENIE and NuWro predictions along with the modified version of GENIE which incorporates new models for better agreement with earlier measurements from MINERvA. In these measurements, the quasi-elastic, resonance, and multi-nucleon knockout processes appear at different kinematics in this two-dimensional space. The results can be used to improve models for neutrino interactions needed by neutrino oscillation experiments.

hep-ex↗

arXiv2022

Single Particle Configurations of the Excited States of $^{203}$Po

Excited states of the $^{203}$Po ($Z = 84, N = 119$) have been investigated after populating them through $^{194}$Pt($^{13}$C,4n) fusion-evaporation reaction at E$_{beam}$ = 74 MeV and using a large array of Compton suppressed HPGe clover detectors as the detection setup for the emitted $γ$-rays. Standard techniques of $γ$-ray spectroscopy have been applied towards establishing the level structure of the nucleus. Twenty new $γ$-ray transitions have been identified therein, through $γ-γ$ coincidence measurements, and spin-parity assignments of several states have been determined or confirmed, following the angular correlation and linear polarization measurements on the observed $γ$-rays. The excited states have been interpreted in the framework of large basis shell model calculations, while comparing their calculated and experimental energies. They have been principally ascribed to proton population in the $h_{9/2}$ and $i_{13/2}$ orbitals outside the $Z = 82$ closure and neutron occupation of the $f_{5/2}$, $p_{3/2}$ and $i_{13/2}$ orbitals in the $N = 126$ shell.

nucl-ex↗

arXiv2022

Multi-wavelength analysis of short GRB 201221D and its comparison with other high \& low redshift short GRBs

We present a detailed analysis of short GRB 201221D lying at redshift $z= 1.045$. We analyse the high-energy data of the burst and compare it with the sample of short gamma-ray bursts (SGRBs). The prompt emission characteristics are typical of those seen in the case of other SGRBs except for the peak energy ($E_{\rm p}$), which lies at the softer end (generally observed in the case of long bursts). We estimate the host galaxy properties by utilising the {\sc Python}-based software {\sc Prospector} to fit the spectral energy distribution of the host. The burst lies at a high redshift relative to the SGRB sample with a median redshift of $z=0.47$. We compare the burst characteristics with other SGRBs with known redshifts along with GRB 200826A (SGRB originated from a collapsar). A careful examination of the characteristics of SGRBs at different redshifts reveals that some of the SGRBs lying at high redshifts have properties similar to long GRBs indicating they might have originated from collapsars. Further study of these GRBs can help to explore the broad picture of progenitor systems of SGRBs.

astro-ph.HE↗

arXiv2022

Simultaneous measurement of proton and lepton kinematics in quasielastic-like $ν_μ$-hydrocarbon interactions from 2 to 20 GeV

Neutrino charged-current quasielastic-like scattering, a reaction category extensively used in neutrino oscillation measurements, probes nuclear effects that govern neutrino-nucleus interactions. This Letter reports the first measurement of the triple-differential cross section for $ν_μ$ quasielastic-like reactions using the hydrocarbon medium of the MINERvA detector exposed to a wide-band beam spanning 2 $\leq$ E$_ν\leq$ 20 GeV. The measurement maps the correlations among transverse and longitudinal muon momenta and summed proton kinetic energies, and compares them to predictions from a state-of-art simulation. Discrepancies are observed that likely reflect shortfalls with modeling of pion and nucleon intranuclear scattering and/or spectator nucleon ejection from struck nuclei. The separate determination of leptonic and hadronic variables can inform experimental approaches to neutrino-energy estimation.

hep-ex↗

arXiv2022

Use of Neutrino Scattering Events with Low Hadronic Recoil to Inform Neutrino Flux and Detector Energy Scale

Charged-current neutrino interactions with low hadronic recoil ("low-nu") have a cross-section that is approximately constant versus neutrino energy. These interactions have been used to measure the shape of neutrino fluxes as a function of neutrino energy at accelerator-based neutrino experiments such as CCFR, NuTeV, MINOS and MINERvA. In this paper, we demonstrate that low-nu events can be used to measure parameters of neutrino flux and detector models and that utilization of event distributions over the upstream detector face can discriminate among parameters that affect the neutrino flux model. From fitting a large sample of low-nu events obtained by exposing MINERvA to the NuMI medium-energy beam, we find that the best-fit flux parameters are within their a priori uncertainties, but the energy scale of muons reconstructed in the MINOS detector is shifted by 3.6% (or 1.8 times the a priori uncertainty on that parameter). These fit results are now used in all MINERvA cross-section measurements, and this technique can be applied by other experiments operating at MINERvA energies, such as DUNE.

hep-ex↗

arXiv2022

Cosmology in the dark: How compact binaries formation impact the gravitational-waves cosmological measurements

Information about the mass spectrum of compact stars can be used to infer cosmological parameters from gravitational waves (GW) in the absence of redshift measurements obtained from electromagnetic (EM) observations. This method will be fundamental in measuring and testing cosmology with GWs for current and future ground-based GW detectors where the majority part of sources are detected without an associated EM counterpart. In this proceeding, we will discuss the prospects and limitations of this approach for studying cosmology. We will show that, even when assuming GW detectors with current sensitivities, the determination of the Hubble constant is strongly degenerate with the maximum mass for black hole production. We will discuss how assuming wrong models for the underlying population of black hole events can bias the Hubble constant estimate up to 40\%.

gr-qc↗

arXiv2022

Neutral pion reconstruction using machine learning in the MINERvA experiment at $\langle E_ν\rangle \sim 6$ GeV

This paper presents a novel neutral-pion reconstruction that takes advantage of the machine learning technique of semantic segmentation using MINERvA data collected between 2013-2017, with an average neutrino energy of $6$ GeV. Semantic segmentation improves the purity of neutral pion reconstruction from two gammas from 71\% to 89\% and improves the efficiency of the reconstruction by approximately 40\%. We demonstrate our method in a charged current neutral pion production analysis where a single neutral pion is reconstructed. This technique is applicable to modern tracking calorimeters, such as the new generation of liquid-argon time projection chambers, exposed to neutrino beams with $\langle E_ν\rangle$ between 1-10 GeV. In such experiments it can facilitate the identification of ionization hits which are associated with electromagnetic showers, thereby enabling improved reconstruction of charged-current $ν_e$ events arising from $ν_μ \rightarrow ν_{e}$ appearance.

hep-ex↗

arXiv2022

Statistical analysis of the causes of excess variance in the 21 cm signal power spectra obtained with the Low-Frequency Array

The detection of the 21 cm signal of neutral hydrogen from the Epoch of Reionization (EoR) is challenging due to bright foreground sources, radio frequency interference (RFI), the ionosphere, and instrumental effects. Even after correcting for these effects in the calibration step and applying foreground removal techniques, the remaining residuals in the observed 21 cm power spectra are still above the thermal noise, which is referred to as the "excess variance." We study potential causes of this excess variance based on 13 nights of data obtained with the Low-Frequency Array (LOFAR). We focused on the impact of gain errors, the sky model, and ionospheric effects on the excess variance by correlating the relevant parameters such as the gain variance over time or frequency, local sidereal time (LST), diffractive scale, and phase structure-function slope with the level of excess variance. Our analysis shows that excess variance has an LST dependence, which is related to the power from the sky. And the simulated Stokes I power spectra from bright sources and the excess variance show a similar progression over LST with the minimum power appearing at LST bin 6h to 9h. This LST dependence is also present in sky images of the residual Stokes I of the observations. In very-wide sky images, we demonstrate that the extra power comes exactly from the direction of bright and distant sources Cassiopeia A and Cygnus A with the array beam patterns. These results suggest that the level of excess variance in the 21 cm signal power spectra is related to sky effects and, hence, it depends on LST. In particular, very bright and distant sources such as Cassiopeia A and Cygnus A can dominate the effect. This is in line with earlier studies and offers a path forward toward a solution since the correlation between the sky-related effects and the excess variance is non-negligible.

astro-ph.CO↗

arXiv2022

Constraint of the MINERvA Medium Energy Neutrino Flux using Neutrino-Electron Elastic Scattering

Elastic neutrino scattering on electrons is a precisely-known purely leptonic process that provides a standard candle for measuring neutrino flux in conventional neutrino beams. Using a total sample of 810 neutino-electron scatters after background subtraction, the measurement reduces the normalization uncertainty on the muon neutrino NuMI flux between 2 and 20 GeV from 7.5% to 3.9%. This is the most precise measurement of neutrino-electron scattering to date, will reduce uncertainties on MINERvA's absolute cross section measurements, and demonstrates a technique that can be used in future neutrino beams such as LBNF.

hep-ex↗

arXiv2022

Magnetostriction in microwave synthesized La0.5Ba0.5CoO3

A single-phase polycrystalline La0.5Ba0.5CoO3-d sample was synthesized by microwave irradiation within 20 minutes of processing time and its structural, magnetic, electrical, and magnetostrictive properties were investigated. While the temperature dependence of field-cooled magnetization (M) in a field of H = 0.5 kOe indicates the onset of ferromagnetic transition at TC = 177 K, irreversibility between the zero field-cooled and field cooled M(T) persists even at H = 3 kOe. M(H) at 10 K does not saturate at the maximum available field and has a much smaller value (0.87 μB/Co in a field of 50 kOe) than 1.9 μB/Co expected for spin-only contribution from intermediate Co3+ and Co4+ spins. The resistivity shows insulating behavior down to 10 K and only a small magnetoresistance (~ 2% for H = 70 kOe) occurs around TC. All these results suggest a magnetically heterogeneous ground state with weakly interacting ferromagnetic clusters coexisting with a non-ferromagnetic phase. The length of the sample expands in the direction of the applied magnetic field (positive magnetostriction) and does not show saturation even at 50 kOe. The magnetostriction has a maximum value (= 252 ppm) at 10 K and it decreases with increasing temperature. The smaller value of magnetostriction compared to the available data on La0.5Sr0.5CoO3 suggests that non-ferromagnetic matrix is most likely antiferromagnetic and it restrains the field-induced expansion of ferromagnetic clusters in the microwave synthesized La0.5Ba0.5CoO3-d sample.

cond-mat.mtrl-sci↗

arXiv2022

Anomalous Nernst effect in La0.5Ca0.5Coo3

We report the occurrence of the anomalous Nernst effect (ANE) in polycrystalline perovskite La0.5Ca0.5CoO3. The sample is ferromagnetic below TC = 147 K and resistivity shows non-metallic behavior above and below the TC with only a small negative magnetoresistance (~2%) around TC. Field dependence of magnetization at 10 K shows large hysteresis with a coercive field of 6 kOe but a small magnetization ~ 0.64 Bohr magneton/Co even in a field of 50 kOe, which indicates the presence of magnetically heterogeneous ground state consisting of ferromagnetic and non-ferromagnetic phases. The field dependence of the Nernst thermopower (Sxy) at low temperatures shows complete saturation but the magnetization does not. This indicates that the ANE in La0.5Ca0.5CoO3 depends only on the transport properties of the ferromagnetic phase, while it is not affected by the non-ferromagnetic phase. Due to the higher value of remnant Sxy, the magnetized polycrystalline sample exhibits ANE in absence of an external magnetic field.

cond-mat.mtrl-sci↗

arXiv2022

Vertex finding in neutrino-nucleus interaction: A Model Architecture Comparison

We compare different neural network architectures for Machine Learning (ML) algorithms designed to identify the neutrino interaction vertex position in the MINERvA detector. The architectures developed and optimized by hand are compared with the architectures developed in an automated way using the package "Multi-node Evolutionary Neural Networks for Deep Learning" (MENNDL), developed at Oak Ridge National Laboratory (ORNL). The two architectures resulted in a similar performance which suggests that the systematics associated with the optimized network architecture are small. Furthermore, we find that while the domain expert hand-tuned network was the best performer, the differences were negligible and the auto-generated networks performed well. There is always a trade-off between human, and computer resources for network optimization and this work suggests that automated optimization, assuming resources are available, provides a compelling way to save significant expert time.

hep-ex↗

arXiv2021

Constraining the NuMI neutrino flux using inverse muon decay reactions in MINERvA

Inverse muon decay, $ν_μe^-\toμ^-ν_e$, is a reaction whose cross-section can be predicted with very small uncertainties. It has a neutrino energy threshold of $\approx 11$ GeV and can be used to constrain the high-energy part of the flux in the NuMI neutrino beam. This reaction is the dominant source of events which only contain high-energy muons nearly parallel to the direction of the neutrino beam. We have isolated a sample of hundreds of such events in neutrino and anti-neutrino enhanced beams, and have constrained the predicted high-energy flux.

hep-ex↗

arXiv2021

A numerical study of 21-cm signal suppression and noise increase in direction-dependent calibration of LOFAR data

We investigate systematic effects in direction dependent gain calibration in the context of the Low-Frequency Array (LOFAR) 21-cm Epoch of Reionization (EoR) experiment. The LOFAR EoR Key Science Project aims to detect the 21-cm signal of neutral hydrogen on interferometric baselines of $50-250 λ$. We show that suppression of faint signals can effectively be avoided by calibrating these short baselines using only the longer baselines. However, this approach causes an excess variance on the short baselines due to small gain errors induced by overfitting during calibration. We apply a regularised expectation-maximisation algorithm with consensus optimisation (sagecal-co) to real data with simulated signals to show that overfitting can be largely mitigated by penalising spectrally non-smooth gain solutions during calibration. This reduces the excess power with about a factor 4 in the simulations. Our results agree with earlier theoretical analysis of this bias-variance trade off and support the gain-calibration approach to the LOFAR 21-cm signal data.

astro-ph.CO↗

arXiv2021

Magnon-polarons in van der Waals antiferromagnet FePS3

The hybridization of magnons (spin waves) with phonons, if sufficiently strong and comprising long wavelength excitations, may offer a new playground when manipulating the magnetically ordered systems with light. Applying a magnetic field to a quasi-2D antiferromagnet, FePS3, we tune the magnon-gap excitation towards coincidence with the initially lower-in-energy phonon modes. Hybrid magnon-phonon modes, the magnon polarons are unveiled with demonstration of a pronounced avoided crossing between the otherwise bare magnon and phonon excitations. The magnon polarons in FePS3 are primary traced with Raman scattering experiments, but, as we show, they also couple directly to terahertz photons, what evokes their further explorations in the domain of antiferromagnetic optospintronics.

cond-mat.mtrl-sci↗

arXiv2021

Photometric variability of the pre-main sequence stars towards the Sh 2-190 region

We present the results from our time-series imaging data taken with the 1.3m Devasthal fast optical telescope and 0.81m Tenagara telescope in $V$, $R_{c}$, $I_{c}$ bands covering an area of $\sim18^\prime.4\times 18^\prime.4$ towards the star-forming region Sh 2-190. This photometric data helped us to explore the nature of the variability of pre-main sequence (PMS) stars. We have identified 85 PMS variables, i.e., 37 Class II and 48 Class III sources. Forty-five of the PMS variables are showing periodicity in their light curves. We show that the stars with thicker discs and envelopes rotate slower and exhibit larger photometric variations compared to their disc-less counterparts. This result suggests that rotation of the PMS stars is regulated by the presence of circumstellar discs. We also found that the period of the stars show a decreasing trend with increasing mass in the range of $\sim$0.5-2.5 M$_\odot$. Our result indicates that most of the variability in Class II sources is ascribed to the presence of thick disc, while the presence of cool spots on the stellar surface causes the brightness variation in Class III sources. X-ray activities in the PMS stars were found to be at the saturation level reported for the main sequence (MS) stars. The younger counterparts of the PMS variables are showing less X-ray activity hinting towards a less significant role of a stellar disc in X-ray generation.

astro-ph.SR↗

arXiv2021

Anomalous Nernst thermopower and giant magnetostriction in microwave synthesized La0.5Sr0.5CoO3

Ferromagnetic metallic oxides have potential applications in spincaloric devices which utilize the spin property of charge carriers for interconversion of heat and electricity through the spin Seebeck or the anomalous Nernst effect or both. In this work, we synthesized polycrystalline La0.5S0.5CoO3 by microwave irradiation method and studied its transverse thermoelectric voltage (Nernst thermopower) and change in the linear dimension of the sample (Joule magnetostriction) in response to external magnetic fields. In addition, magnetization, temperature dependences of electrical resistivity, and longitudinal Seebeck coefficient (Sxx) in absence of an external magnetic field were also measured. The sample is ferromagnetic with a Curie temperature of TC = 247 K and shows a metal-like resistivity above and below TC with a negative sign of Sxx suggesting charge transport due to electrons. Magnetic field dependence of the Nernst thermopower (Sxy) at a fixed temperature shows a rapid increase at low fields and a tendency to saturate at high fields as like the magnetization. Anomalous contribution to Sxy was extracted from total Sxy measured and it exhibits a maximum value of ~ 0.21 microV/K at 180 K for H = 50 kOe, which is comparable to the value found in a single crystal for a lower Sr content. The Joule magnetostriction is positive, i.e., the length of the sample expands along the direction of the magnetic field and it does not saturate even at 50 kOe. The magnetostriction increases with decreasing temperature below TC and reaches a maximum value of 500 ppm at T = 40 K and below. Coexistence of the anomalous Nernst thermopower and giant magnetostriction in a single compound has potential applications for thermal energy harvesting and low-temperature actuators, respectively.

cond-mat.mtrl-sci↗

arXiv2021

Cosmology in the dark: On the importance of source population models for gravitational-wave cosmology

Knowledge of the shape of the mass spectrum of compact objects can be used to help break the degeneracy between the mass and redshift of the gravitational wave (GW) sources, and thus can be used to infer cosmological parameters in the absence of redshift measurements obtained from electromagnetic observations. In this paper, we study extensively different aspects of this approach, including its computational limits and achievable accuracy. We focus on ground-based detectors with current and future sensitivities, we first perform the analysis of an extensive set of simulated data with a hierarchical Bayesian scheme inferring population and cosmological parameters. We consider a population model (power-law plus Gaussian) which exhibits characteristic scales (extremes of the mass spectrum, presence of an accumulation point) that allows an indirect estimate of the source redshift. Our analysis of this catalog highlights and quantifies the tight interplay between source population and cosmological parameters, as well as the influence of initial assumptions (whether formulated on the source or cosmological parameters). We then validate our results by an "end-to-end" analysis using simulated GW data and posterior samples generated from Bayesian samplers used for GW parameter estimation, thus mirroring the analysis chain used for observational data for the first time in literature. Our results then lead us to re-examine the estimation of $H_0$ obtained with GWTC-1, and we show explicitly how population assumptions impact the final $H_0$ result. Our results underline the importance of inferring population and cosmological parameters jointly (and not separately as is often assumed). The only exception, as we discuss, is if an electromagnetic counterpart was to be observed for all the BBH events: then the population assumptions have less impact on the estimation of cosmological parameters.

gr-qc↗