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Kamales Kar

Publications and source records attributed to Kamales Kar.

At least 19 recordsLinked to original sources
arXiv2024

Elastic scattering of supernova neutrinos with electrons in xenon

Neutrinos from a Galactic core collapse supernova can undergo elastic scattering with electrons in xenon atoms in liquid xenon based dark matter detectors giving rise to electrons of kinetic energy up to a few MeV. We calculate the scattered electron spectrum and the number of such elastic scattering events expected for a typical Galactic core collapse supernova in a xenon target. Although the expected number of events is small (compared to, for example, inelastic neutrino-nucleus charged current interaction with xenon nuclei, that also gives rise to final state electrons), the distinct spectral shape of the scattered electrons may allow identification of the elastic scattering events. Further, while the process is dominated by neutrinos and antineutrinos of electron flavor, it receives contributions from all the six neutrino species. Identification of the electron scattering events may, therefore, allow an estimation of the relative fractions of the total supernova explosion energy going into electron flavored and non-electron flavored neutrinos.

hep-ph↗
arXiv2022

Inelastic charged current interaction of supernova neutrinos in two-phase liquid xenon dark matter detectors

It has been known that neutrinos from supernova (SN) bursts can give rise to nuclear recoil (NR) signals arising from coherent elastic neutrino-nucleus scattering (CE$ν$NS) interaction, a neutral current (NC) process, of the neutrinos with xenon nuclei in future large (multi-ton scale) liquid xenon (LXe) detectors employed for dark matter search, depending on the SN progenitor mass and distance to the SN. In this paper, we show that the same detectors will also be sensitive to inelastic charged current (CC) interactions of the SN electron neutrinos ($ν_e$CC) with the xenon nuclei. Such interactions, while creating an electron in the final state, also leave the post-interaction target nucleus in an excited state, the subsequent deexcitation of which produces, among other particles, gamma rays and neutrons. The electron and deexcitation gamma rays will give ``electron recoil" (ER) type signals, while the deexcitation neutrons produce, through their multiple scattering on the xenon nuclei, further xenon nuclear recoils that will also give NR signals (in addition to those produced through the CE$ν$NS interactions). We discuss the observable scintillation and ionization signals associated with SN neutrino induced CE$ν$NS and $ν_e$CC events in a generic LXe detector and argue that upcoming sufficiently large LXe detectors should be able to detect both these types of events due to neutrinos from reasonably close by SN bursts. We also note that since the total CC induced ER and NR signals receive contributions predominantly from $ν_e$CC interactions while the CE$ν$NS contribution comes from NC interactions of {\emph all the six species of neutrinos}, identification of the $ν_e$CC and CE$ν$NS origin events may offer the possibility of extracting useful information about the distribution of the total SN explosion energy going into different neutrino flavors.

hep-ph↗
arXiv2022

Simulation of Nuclear Recoils due to Supernova Neutrino-induced Neutrons in Liquid Xenon Detectors

Neutrinos from supernova (SN) bursts can give rise to detectable number of nuclear recoil (NR) events through the coherent elastic neutrino-nucleus scattering (CE$ν$NS) process in large scale liquid xenon detectors designed for direct dark matter search, depending on the SN progenitor mass and distance. Here we show that in addition to the direct NR events due to CE$ν$NS process, the SN neutrinos can give rise to additional nuclear recoils due to the elastic scattering of neutrons produced through inelastic interaction of the neutrinos with the xenon nuclei. We find that the contribution of the supernova neutrino-induced neutrons ($ν$I$n$) can significantly modify the total xenon NR spectrum at large recoil energies compared to that expected from the CE$ν$NS process alone. Moreover, for recoil energies $\gtrsim20$ keV, dominant contribution is obtained from the ($ν$I$n$) events. We numerically calculate the observable S1 and S2 signals due to both CE$ν$NS and $ν$I$n$ processes for a typical liquid xenon based detector, accounting for the multiple scattering effects of the neutrons in the case of $ν$I$n$, and find that sufficiently large signal events, those with S1$\gtrsim$50 photo-electrons (PE) and S2$\gtrsim$2300 PE, come mainly from the $ν$I$n$ scatterings.

astro-ph.HE↗
arXiv2020

Supernova neutrino detection through neutron emission by nuclei

Neutrinos from core collapse supernovae can excite nuclei of some detector materials beyond their neutron emission thresholds. Detection of these neutrons can give valuable information about the supernova explosion mechanism and possibly also throw light on neutrino properties. In this article, we give a brief review of the basic physics of neutrino induced neutron emission and describe the results of some recent calculations of supernova neutrino induced neutrons for some specific target detector materials due to charged current (CC) interactions of the electron flavored neutrinos and antineutrinos as well as due to neutral current (NC) interactions of neutrinos and antineutrinos of all flavors with the detector nuclei. We highlight the fact that a detector material such as lead with a relatively large neutron excess produces neutrons dominantly through the CC interaction of the $ν_e$s, whereas a material such as iron with small neutron excess produces neutrons dominantly through the combined NC interaction of all the six neutrino and antineutrino species. This raises the interesting possibility of probing the fraction of mu- and tau flavored neutrinos (which interact only through NC interaction) in the supernova neutrino flux by means of simultaneous detection of a supernova in a lead and an iron detector, for example.

hep-ph↗
arXiv2017

Isospin nonconservation for fp-shell nuclei by spectral distribution theory

The one- plus two-body isospin nonconserving nuclear interactions are included in the prediction of ground state energies of fp shell nuclei using spectral distribution theory. This in turn is used to calculate the linear term in the isobaric mass-multiplet equation and the predictions are then compared to experimental values after the addition of the Coulomb contribution. The agreement is found to be reasonable as observed for sd shell nuclei earlier. One also sees that in this method the contribution to the linear term comes almost completely from the one body isovector Hamiltonian and that results in a huge simplification of the problem.

nucl-th↗
arXiv2017

Detecting supernova neutrinos with iron and lead detectors

Supernova (SN) neutrinos can excite the nuclei of various detector materials beyond their neutron emission thresholds through charged current (CC) and neutral current (NC) interactions. The emitted neutrons, if detected, can be a signal for the supernova event. Here we present the results of our study of SN neutrino detection through the neutron channel in lead ($^{208} {\rm Pb}$) and iron ($^{56} {\rm Fe}$) detectors for realistic neutrino fluxes and energies given by the recent Basel/Darmstadt simulations for a 18 solar mass progenitor SN at a distance of 10 kpc. We find that, in general, the number of neutrons emitted per kTon of detector material for the neutrino luminosities and average energies of the different neutrino species as given by the Basel/Darmstadt simulations are significantly lower than those estimated in previous studies based on the results of earlier SN simulations. At the same time, we highlight the fact that, although the total number of neutrons produced per kTon in a iron detector is more than an order of magnitude lower than that for lead, the dominance of the flavor blind NC events in the case of iron, as opposed to dominance of $ν_e$ induced CC events in the case of lead, offers a complementarity between the two detector materials so that simultaneous detection of SN neutrinos in a lead and a sufficiently large iron detector suitably instrumented for neutron detection may allow estimating the fraction of the total $μ$ and $τ$ flavored neutrinos in the SN neutrino flux and thereby probing the emission mechanism as well as flavor oscillation scenarios of the SN neutrinos.

astro-ph.HE↗
arXiv2015

Study of isospin nonconservation in the framework of spectral distribution theory

The observed isospin-symmetry breaking in light nuclei are caused not only by the Coulomb interaction but by the isovector one and two body plus isotensor two body nuclear interactions as well. Spectral distribution theory which treats nuclear spectroscopy and other structural properties in a statistical framework was earlier applied to isospin conserving Hamiltonians only. In this paper we extend that to include the nuclear interactions non-scalar in isospin and work out examples in sd shell to calculate the linear term in the isobaric mass-multiplet equation originating from these non-scalar parts.

nucl-th↗
arXiv2013

Observing supernova neutrino light curve in future dark matter detectors

The possibility of observing supernova (SN) neutrinos through the process of coherent elastic neutrino-nucleus scattering (CENNS) in future ton scale detectors designed primarily for direct detection of dark matter is investigated. In particular, we focus on the possibility of distinguishing the various phases of the SN neutrino emission. The neutrino emission rates from the recent long term Basel/Darmstadt simulations are used to calculate the expected event rates. The recent state-of-the-art SN simulations predict closer fluxes among different neutrino flavors and lower average energies compared to the earlier simulation models. We find that our estimated total event rates are typically a factor of two lower than those predicted using older simulation models. We further find that, with optimistic assumptions on the detector's time resolution (~ 10 ms) and energy threshold (~ 0.1 keV), the neutrinos associated with the accretion phase of the SN can in principle be demarcated out with, for example, a 10-ton Xe detector, although distinguishing the neutrinos associated with the neutronization burst phase of the explosion would typically require several tens of ton detectors. We also comment on the possibility of studying the properties of non-electron flavor neutrinos from the CENNS of SN neutrinos.

astro-ph.HE↗
arXiv2012

Statistical Spectroscopy for Neutron-rich sd-Shell Nuclei

Statistical spectroscopic results using the spectral distribution theory are obtained for the structure of neutron-rich light nuclei going towards the drip line and compared to experimental values available. These results will be useful for nuclear astrophysics problems where often averaged nuclear properties are adequate.

nucl-th↗
arXiv2011

On the Observability of Collective Flavor Oscillations in Diffuse Supernova Neutrino Background

Collective flavor oscillations are known to bring multiple splits in the supernova (SN) neutrino and antineutrino spectra. These spectral splits depend not only on the mass hierarchy of the neutrinos but also on the initial relative flux composition. Observation of spectral splits in a future galactic supernova signal is expected to throw light on the mass hierarchy pattern of the neutrinos. However, since the Diffuse Supernova Neutrino Background (DSNB) comprises of a superposition of neutrino fluxes from all past supernovae, and since different supernovae are expected to have slightly different initial fluxes, it is pertinent to check if the hierarchy dependent signature of collective oscillations can survive this averaging of the flux spectra. Since the actual distribution of SN with initial relative flux spectra of the neutrinos and antineutrinos is unknown, we assume a log-normal distribution for them. We study the dependence of the hierarchy sensitivity to the mean and variance of the log-normal distribution function. We find that the hierarchy sensitivity depends crucially on the mean value of the relative initial luminosity. The effect of the width is to reduce the hierarchy sensitivity for all values of the mean initial relative luminosity. We find that in the very small mixing angle ($θ_{13}$) limit considering only statistical errors even for very moderate values of variance, there is almost no detectable hierarchy sensitivity if the mean relative luminosities of $ν_e$ and $\barν_e$ are greater than 1.

hep-ph↗
arXiv2010

Collective Flavor Oscillations Of Supernova Neutrinos and r-Process Nucleosynthesis

Neutrino-neutrino interactions inside core-collapse supernovae may give rise to collective flavor oscillations resulting in swap between flavors. These oscillations depend on the initial energy spectra, and relative fluxes or relative luminosities of the neutrinos. It has been observed that departure from energy equipartition among different flavors can give rise to one or more sharp spectral swap over energy, termed as splits. We study the occurrence of splits in the neutrino and antineutrino spectra, varying the initial relative fluxes for different models of initial energy spectrum, in both normal and inverted hierarchy. These initial relative flux variations give rise to several possible split patterns whereas variation over different models of energy spectra give similar results. We explore the effect of these spectral splits on the electron fraction, $Y_e$, that governs r-process nucleosynthesis inside supernovae. Since spectral splits modify the electron neutrino and antineutrino spectra in the region where r-process is postulated to happen, and since the pattern of spectral splits depends on the initial conditions of the spectra and the neutrino mass hierarchy, we show that the condition $Y_e < 0.5$ required for successful r-process nucleosynthesis will lead to constraints on the initial spectral conditions, for a given neutrino mass hierarchy.

hep-ph↗
arXiv2009

Effect of Collective Flavor Oscillations on the Diffuse Supernova Neutrino Background

Collective flavor oscillations driven by neutrino-neutrino self interaction inside core-collapse supernovae have now been shown to bring drastic changes in the resultant neutrino fluxes. This would in turn significantly affect the diffuse supernova neutrino background (DSNB), created by all core-collapse supernovae that have exploded in the past. In view of these collective effects, we re-analyze the potential of detecting the DSNB in currently running and planned large-scale detectors meant for detecting both electron neutrinos and antineutrinos. The next generation detectors should be able to observe DSNB fluxes. Under certain conducive conditions, one could learn about neutrino parameters. For instance, it might be possible to determine the neutrino mass hierarchy, even if theta_{13} is almost zero.

hep-ph↗
arXiv2008

Beta decay rates for r-process for nuclei near neutron number N=82

For r-process nucleosynthesis the beta decay rates of very neutron-rich nuclei are important ingredients. We consider the region around the neutron number N=82 and calculate the half-lives and rates for a number of nuclei. Forms for beta strength functions based on spectral distribution methods are used. The calculated half-lives are first compared to the observed values and then predictions are made for very neutron-rich nuclei close to drip line for which no experimental values are available.

astro-ph↗
arXiv2008

Upper Limit on the Cosmic Gamma-Ray Burst Rate from High Energy Diffuse Neutrino Background

We derive upper limits on the ratio $f_{GRB/CCSN}(z) \equiv R_{GRB}(z)/R_{CCSN}(z) \equiv f_{GRB/CCSN}(0)(1+z)^α$, the ratio of the rate, $R_{GRB}$, of long-duration Gamma Ray Bursts (GRBs) to the rate, $R_{CCSN}$, of core-collapse supernovae (CCSNe) in the Universe ($z$ being the cosmological redshift and $α\geq 0$), by using the upper limit on the diffuse TeV--PeV neutrino background given by the AMANDA-II experiment in the South Pole, under the assumption that GRBs are sources of TeV--PeV neutrinos produced from decay of charged pions produced in $pγ$ interaction of protons accelerated to ultrahigh energies at internal shocks within GRB jets. For the assumed ``concordance model'' of cosmic star formation rate, $R_{SF}$, with $R_{CCSN}(z) \propto R_{SF}(z)$, our conservative upper limits are $f_{GRB/CCSN}(0)\leq 5.0\times10^{-3}$ for $α=0$, and $f_{GRB/CCSN}(0)\leq 1.1\times10^{-3}$ for $α=2$, for example. These limits are already comparable to (and, for $α\geq 1$ already more restrictive than) the current upper limit on this ratio inferred from other astronomical considerations, thus providing a useful independent probe of and constraint on the CCSN-GRB connection. Non-detection of a diffuse TeV--PeV neutrino background by the up-coming IceCube detector in the South pole after three years of operation, for example, will bring down the upper limit on $f_{GRB/CCSN}(0)$ to below few $\times10^{-5}$ level, while a detection will confirm the hypothesis of proton acceleration to ultrahigh energies in GRBs and will potentially also yield the true rate of occurrence of these events in the Universe.

astro-ph↗
arXiv2008

A GEANT-based study of atmospheric neutrino oscillation parameters at INO

We have studied the dependence of the allowed space of the atmospheric neutrino oscillation parameters on the time of exposure for a magnetized Iron CALorimeter (ICAL) detector at the India-based Neutrino Observatory (INO). We have performed a Monte Carlo simulation for a 50 kTon ICAL detector generating events by the neutrino generator NUANCE and simulating the detector response by GEANT. A chi-square analysis for the ratio of the up-going and down-going neutrinos as a function of $L/E$ is performed and the allowed regions at 90% and 99% CL are displayed. These results are found to be better than the current experimental results of MINOS and Super-K. The possibilities of further improvement have also been discussed.

hep-ph↗