arXiv subjects

Abhijit Bandyopadhyay

Publications and source records attributed to Abhijit Bandyopadhyay.

At least 37 records · Page 2Linked to original sources

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↗

arXiv2014

Semi-classical treatment of $k$-essence effect on cosmic temperature

A phenomenological model is described for Cosmic Microwave Background Radiation (CMBR) evolution with dark energy an essential ingredient in the form of a $k-$essence scalar field. The following features of this evolution can be successfully obtained from this model: (a) the {\it observed} variation of the rate of change of scale factor $a(t)$, i.e. $\dot a$, with time and (b) the {\it observed} value of the epoch when the universe went from a decelerating phase to an accelerated phase. These two features have been matched with graphical transcriptions of SNe Ia data. The model also indicates that the evolution is sensitive to the presence of inhomogeneity and this sensitivity increases as one goes further into the past. Further, the value of the inhomogeneity parameter determines the epoch of switch over to an accelerated phase. A positive value of inhomogeneity parameter leads to switch over at earlier epochs, while a negative value leads to switch over at later epochs. If the value of the inhomogeneity parameter is a bit negative then the crossover point from deceleration to acceleration gives better agreement with the observed value.

gr-qc↗

arXiv2013

Quintom scalar field : Varying dark energy equation of state obtained from recent SNe Ia, BAO and OHD data

From the analysis of Supernova Ia data alongwith Observational Hubble Data (OHD) and Baryon Acoustic Oscillation (BAO) data, we attempt to find out the nature of a scalar potential that may be responsible for the Dark Energy of the universe. We demonstrate that in order to explain the varying dark energy equation of state ($ω_X(z)$) as obtained in a model independent way from the analyses of observational data, we need to invoke a quintom scalar field having a "quintessence" part for $ω_X(z) > -1$ and a "phantom" part for $ω_X(z) < -1$. We consider a Gaussian type potential for these scalar fields and compare the dark energy equation of state derived from such potential with the one computed from the data analysis.

astro-ph.CO↗

arXiv2012

On Diurnal and Annual Variations of Directional Detection Rates of Dark Matter

Direction sensitive direct detection of Weakly Interacting Massive Particles (WIMPs) as dark matter would provide an unambiguous non-gravitational signature of dark matter (DM). The diurnal variation of DM signal due to earth's rotation around its own axis can be a significant signature for galactic WIMPs. Because of particular orientation of earth's axis of rotation with respect to WIMP wind direction, the apparent direction of WIMP wind as observed at a detector can alter widely over a day. In this work we calculate the directional detection rates with their daily and yearly modulations in earth-bound dark matter experiments considering detailed features of the geometry and dynamics of the earth-sun system along with the solar motion in galactic frame. A separate halo model namely the dark disc model other than the usual standard halo model for dark matter halo is also considered and the results for two models are compared. We demonstrate the results for two types of gas detectors namely DRIFT (target material CS2) and NEWAGE (target material CF4) that use Time Projection Chamber techniques for measuring directionality of the recoil nucleus. The WIMP mass and recoil energy dependence of the daily variation of event rates are computed for specific detector and the sensitive ranges of mass and recoil energies for the considered detector are probed.

hep-ph↗

arXiv2012

The $k$-essence scalar field in the context of Supernova Ia Observations

A $k$-essence scalar field model having (non canonical) Lagrangian of the form $L=-V(ϕ)F(X)$ where $X=1/2g^{μν}\nabla_μϕ\nabla_νϕ$ with constant $V(ϕ)$ is shown to be consistent with luminosity distance-redshift data observed for type Ia Supernova. For constant $V(ϕ)$, $F(X)$ satisfies a scaling relation which is used to set up a differential equation involving the Hubble parameter $H$, the scale factor $a$ and the $k$-essence field $ϕ$. $H$ and $a$ are extracted from SNe Ia data and using the differential equation the time dependence of the field $ϕ$ is found to be: $ϕ(t) \sim λ_0 + λ_1 t + λ_2 t^2$. The constants $λ_i$ have been determined. The time dependence is similar to that of the quintessence scalar field (having canonical kinetic energy) responsible for homogeneous inflation. Furthermore, the scaling relation and the obtained time dependence of the field $ϕ$ is used to determine the $X$-dependence of the function $F(X)$.

astro-ph.CO↗

arXiv2011

Reconstructing the equation of state and density parameter for dark energy from combined analysis of recent SNe Ia, OHD and BAO data

We adopt a model independent method to reconstruct the dark energy equation of state by analyzing 5 sets of SNe Ia data along with Baryon Acoustic Oscillation (BAO) and Observational Hubble Data (OHD). The SNe Ia data sets include the most recent UNION2 data and other data compilations from the year 2007 to the present. We assume a closed form parametrization of the luminosity distance in terms of redshift and perform a $χ^2$ analysis of the observational data. The matter density at the present epoch $Ω_m^0$ is also taken to be a parameter in the analysis and its best-fit values are obtained for each of the data sets. We found a strong dependence of dark energy equation of state on the matter density in the present and earlier epoch. From the analysis, we also predict the lower limit of matter density parameter at an earlier epoch within 1$σ$ confidence level for a flat FRW universe. The dark energy equation of state appears to be a slow varying function of $z$. The variation of dark energy density parameter and the matter density parameter are also shown along with their 1$σ$ variations.

astro-ph.CO↗

arXiv2010

Constraining Scalar Singlet Dark Matter with CDMS, XENON and DAMA and Prediction for Direct Detection Rates

We consider a simplest extension of the Standard Model (SM) through the incorporation of a real scalar singlet and an additional discrete $Z_2$ symmetry. The model admits the neutral scalar singlet to be stable and thus, a viable component of dark matter. We explore the parameter space of the model keeping in view the constraints arise from different dark matter direct detection experiments through WIMP-nucleon scattering. First of all, we have utilised the data obtained from CDMS, XENON-10 and XENON-100 collaborations. We further constraint the parameter space from the DAMA collaboration results (both with and without channelling) and CoGeNT collaboration results. Throughout our analysis, the constraint arises due to the observed relic density of dark matter reported by WMAP experiment, is also incorporated. Utilising all those constraints, on the model parameter space, we calculate the event rates and the annual variation of event rates in the context of a Liquid Argon Detector experiment.

hep-ph↗

arXiv2010

Interpreting the bounds on Solar Dark Matter induced muons at Super-Kamiokande in the light of CDMS results

We consider the recent limits on dark matter - nucleon elastic scattering cross section from the analysis of CDMS II collaboration using the two signal events observed in CDMS experiment. With these limits we try to interpret the Super-Kamiokande (SK) bounds on the detection rates of up-going muons induced by the neutrinos that are produced in the sun from the decay of annihilation products of dark matter (WIMPs) captured in the solar core. Calculated rates of up-going muons for different annihilation channels at SK using CDMS bounds are found to be orders below the predicted upper limits of such up-going muon rates at SK. Thus there exists room for enhancement (boost) of the calculated rates using CDMS limits for interpreting SK bounds. Such a feature is expected to represent the PAMELA data with the current CDMS limits. We also show the dependence of such a possible enhancement factor (boost) on WIMP mass for different WIMP annihilation channels.

hep-ph↗

arXiv2008

Neutrino Oscillation Parameters After High Statistics KamLAND Results

We do a re-analysis to asses the impact of the results of the Borexino experiment and the recent 2.8 KTy KamLAND data on the solar neutrino oscillation parameters. The current Borexino results are found to have no impact on the allowed solar neutrino parameter space. The new KamLAND data causes a significant reduction of the allowed range of $Δm^2_{21}$, determining it with an unprecedented precision of 8.3% at 3$σ$. The precision of $Δm^2_{21}$ is controlled practically by the KamLAND data alone. Inclusion of new KamLAND results also improves the upper bound on $\sin^2θ_{12}$, but the precision of this parameter continues to be controlled by the solar data. The third mixing angle is constrained to be $\sin^2θ_{13} < 0.063$ at $3σ$ from a combined fit to the solar, KamLAND, atmospheric and CHOOZ results. We also address the issue of how much further reduction of allowed range of $Δm^2_{21}$ and $\sin^2θ_{12}$ is possible with increased statistics from KamLAND. We find that there is a sharp reduction of the $3σ$ ``spread'' with enhanced statistics till about 10 KTy after which the spread tends to flatten out reaching to less than 4% with 15 KTy data. For $\sin^2θ_{12}$ however, the spread is more than 25% even after 20 KTy exposure and assuming $θ_{12} < π/4$, as dictated by the solar data. We show that with a KamLAND like reactor ``SPMIN'' experiment at a distance of $\sim$ 60 km, the spread of $\sin^2θ_{12}$ could be reduced to about 5% at $3σ$ level while $Δm_{21}^2$ could be determined to within 4%, with just 3 KTy exposure.

hep-ph↗

arXiv2007

The (3+2) Neutrino Mass Spectrum and Double Chooz

The implications of extra sterile neutrinos for the Double Chooz experiment is expounded. The so-called ``3+2'' mass spectrum with 2 sterile neutrinos mixed with the active ones, is still allowed by the global neutrino data including MiniBooNE. We probe its impact on the resultant reactor antineutrino signal at the near and far detector of the Double Chooz experiment. The oscillations driven by the additional mass squared difference due to the sterile states bring an energy independent constant suppression at both the near and far detectors. We study to what extent the measurement of $θ_{13}$ would get affected due to the presence of sterile mixing. We also give the projected sensitivity that Double Chooz will have to constrain the extra mixing angles associated with the sterile states.

hep-ph↗

arXiv2006

Constraints on flavor-dependent long range forces from neutrino experiments

We study the impact of flavor-dependent long range leptonic forces mediated by the $L_e-L_μ$ or $L_e -L_τ$ gauge bosons on the solar neutrino oscillations, when the interaction range $R_{LR}$ is much larger than the Earth-Sun distance. The solar and atmospheric neutrino mass scales do not get trivially decoupled in this situation even if $θ_{13}$ is vanishingly small. In addition, for $α\gsim 10^{-52}$ and normal hierarchy, resonant enhancement of $θ_{13}$ may give rise to strong energy dependent effects on the $ν_e$ survival probability. A complete three generation analysis of the solar neutrino and KamLAND data gives the $3σ$ limits $α_{eμ} < 3.4 \times 10^{-53}$ and $α_{eτ} < 2.5 \times 10^{-53}$ when $R_{LR}$ is much smaller than our distance from the galactic center. With larger $R_{LR}$, the collective LR potential due to all the electrons in the galaxy becomes significant and the constraints on $α$ become stronger by upto two orders of magnitude.

hep-ph↗

arXiv2006

Constraints on flavor-dependent long range forces from solar neutrinos and KamLAND

Flavor-dependent long range (LR) leptonic forces, like those mediated by the $L_e-L_μ$ or $L_e -L_τ$ gauge bosons, constitute a minimal extension of the standard model that preserves its renormalizability. We study the impact of such interactions on the solar neutrino oscillations when the interaction range $R_{LR}$ is much larger than the Earth-Sun distance. The LR potential can dominate over the standard charged current potential inside the Sun in spite of strong constraints on the coupling $α$ of the LR force coming from the atmospheric neutrino data and laboratory search for new forces. We demonstrate that the solar and atmospheric neutrino mass scales do not get trivially decoupled even if $θ_{13}$ is vanishingly small. In addition, for $α\gsim 10^{-52}$ and normal hierarchy, resonant enhancement of $θ_{13}$ results in nontrivial energy dependent effects on the $ν_e$ survival probability. We perform a complete three generation analysis, and obtain constraints on $α$ through a global fit to the solar neutrino and KamLAND data. We get the $3σ$ limits $α_{eμ} < 3.4 \times 10^{-53}$ and $α_{eτ} < 2.5 \times 10^{-53}$ when $R_{LR}$ is much smaller than our distance from the galactic center. With larger $R_{LR}$, the collective LR potential due to all the electrons in the galaxy becomes significant and the constraints on $α$ become stronger by upto two orders of magnitude.

hep-ph↗

arXiv2006

Solar Model Parameters and Direct Measurements of Solar Neutrino Fluxes

We explore a novel possibility of determining the solar model parameters, which serve as input in the calculations of the solar neutrino fluxes, by exploiting the data from direct measurements of the fluxes. More specifically, we use the rather precise value of the $^8B$ neutrino flux, $ϕ_B$ obtained from the global analysis of the solar neutrino and KamLAND data, to derive constraints on each of the solar model parameters on which $ϕ_B$ depends. We also use more precise values of $^7Be$ and $pp$ fluxes as can be obtained from future prospective data and discuss whether such measurements can help in reducing the uncertainties of one or more input parameters of the Standard Solar Model.

hep-ph↗

arXiv2005

High Precision Measurements of $θ_{\odot}$ in Solar and Reactor Neutrino Experiments

We discuss the possibilities of high precision measurement of the solar neutrino mixing angle $θ_\odot \equiv θ_{12}$ in solar and reactor neutrino experiments. The improvements in the determination of $\sin^2θ_{12}$, which can be achieved with the expected increase of statistics and reduction of systematic errors in the currently operating solar and KamLAND experiments, are summarised. The potential of LowNu $ν-e$ elastic scattering experiment, designed to measure the $pp$ solar neutrino flux, for high precision determination of $\sin^2θ_{12}$, is investigated in detail. The accuracy in the measurement of $\sin^2θ_{12}$, which can be achieved in a reactor experiment with a baseline $L \sim (50-70)$ km, corresponding to a Survival Probability MINimum (SPMIN), is thoroughly studied. We include the effect of the uncertainty in the value of $\sin^2θ_{13}$ in the analyses. A LowNu measurement of the $pp$ neutrino flux with a 1% error would allow to determine $\sin^2θ_{12}$ with an error of 14% (17%) at 3$σ$ from a two-generation (three-generation) analysis. The same parameter $\sin^2θ_{12}$ can be measured with an uncertainty of 2% (6%) at 1$σ$ (3$σ$) in a reactor experiment with $L \sim60 $ km, statistics of $\sim$60 GWkTy and systematic error of 2%. For the same statistics, the increase of the systematic error from 2% to 5% leads to an increase in the uncertainty in $\sin^2θ_{12}$ from 6% to 9% at 3$σ$. The inclusion of the $\sin^2θ_{13}$ uncertainty in the analysis changes the error on $\sin^2θ_{12}$ to 3% (9%). The effect of $\sin^2θ_{13}$ uncertainty on the $\sin^2θ_{12}$ measurement in both types of experiments is considerably smaller than naively expected.

hep-ph↗

arXiv2004

Update of the solar neutrino oscillation analysis with the 766 Ty KamLAND spectrum

We investigate the impact of the 766.3 Ty KamLAND spectrum data on the determination of the solar neutrino oscillation parameters. We show that the observed spectrum distortion in the KamLAND experiment firmly establishes $Δm^2_{21}$ to lie in the low-LMA solution region. The high-LMA solution is excluded at more than 4$σ$ by the global solar neutrino and KamLAND spectrum data. The maximal solar neutrino mixing is ruled out at $6σ$ level. The $3σ$ allowed region in the $Δm^2_{21}-\sin^2θ_{12}$ plane is found to be remarkably stable with respect to leaving out the data from one of the solar neutrino experiments from the global analysis. We perform a three flavor neutrino oscillation analysis of the global solar neutrino and KamLAND spectrum data as well. The $3σ$ upper limit on $\sin^2θ_{13}$ is found to be $ \sin^2θ_{13} <0.055$. We derive predictions for the CC to NC event rate ratio and day-night (D-N) asymmetry in the CC event rate, measured in the SNO experiment, and for the suppression of the event rate in the BOREXINO and LowNu experiments. Prospective high precision measurements of the solar neutrino oscillation parameters are also discussed.

hep-ph↗

arXiv2004

Global Analysis of Neutrino Oscillation

We present the constraints on neutrino oscillation parameters $Δm^2_{\odot}$ and $θ_{\odot}$ governing the solar neutrino oscillations from two generation analysis of solar and KamLAND data. We include the latest 766.3 ton year KamLAND data in our analysis. We also present the allowed values of parameters $Δm^2_{atm}$ and $\sin^2θ_{atm}$ from two generation oscillation analysis of SuperKamiokande atmospheric and K2K data. For both cases we discuss the precision achieved in the present set of experiments and also how the precision can be improved in future. We also obtain the bounds on $θ_{13}$ from three generation analysis of global oscillation data. We emphasise on the roles played by different data sets in constraining the allowed parameter ranges.

hep-ph↗

arXiv2003

Prospects of probing $θ_{13}$ and neutrino mass hierarchy by Supernova Neutrinos in KamLAND

In this paper we study the physics potential of the KamLAND detector in probing neutrino oscillation parameters through observation of supernova neutrinos. In particular, we discuss the possibilities of probing the mixing angle $θ_{13}$ and determining the sign of $Δm^2_{32}$ from the total charged current(CC) event rates on the proton and $^{12}{C}$ target, as well as from the CC spectra. We discuss the chances of probing the earth matter effect induced modulations from the observation of CC spectra in the different CC reactions in KamLAND and find the volume required to get a statistically significant signature of the earth matter effect in different energy bins. We also calculate the event rates expected in the neutral current (NC) reactions on Carbon and free proton and investigate if the charged current to neutral current ratios, which are free of the absolute luminosity uncertainty in the supernova neutrino fluxes, can be useful in probing the oscillation parameters.

hep-ph↗

arXiv2003

Constraints on neutrino oscillation parameters from the SNO salt phase data

The physics implications of the just published salt phase data from the SNO experiment are examined. The effect of these data on the allowed ranges of the solar neutrino oscillation parameters, $Δ_m^2_{21}$ and $\sin^2θ_{12}$, are studied in the cases of two- and three- neutrino mixing. In the latter case we derive an upper limit on the angle $θ_{13}$. Constraints on the solar $ν_e$ transitions into a mixture of active and sterile neutrinos are also presented. Finally, we give predictions for the day-night asymmetry in the SNO experiment, for the event rate in the BOREXINO and LowNu experiments, and discuss briefly the constraints on the solar neutrino oscillation parameters which can be obtained with prospective KamLAND data.

hep-ph↗