arXiv subjects

Abhijit Bandyopadhyay

Publications and source records attributed to Abhijit Bandyopadhyay.

48 records · Page 3Linked to original sources

arXiv2003

Solar Neutrino Oscillation Parameters after KamLAND

We explore the impact of the data from the KamLAND experiment in constraining neutrino mass and mixing angles involved in solar neutrino oscillations. In particular we discuss the precision with which we can determine the the mass squared difference $Δm^2_{solar}$ and the mixing angle $θ_{solar}$ from combined solar and KamLAND data. We show that the precision with which $Δm^_{solar}$ can be determined improves drastically with the KamLAND data but the sensitivity of KamLAND to the mixing angle is not as good. We study the effect of enhanced statistics in KamLAND as well as reduced systematics in improving the precision. We also show the effect of the SNO salt data in improving the precision. Finally we discuss how a dedicated reactor experiment with a baseline of 70 km can improve the $θ_{solar}$ sensitivity by a large amount.

hep-ph↗

arXiv2003

On the Measurement of Solar Neutrino Oscillation Parameters with KamLAND

A new reactor power plant Shika-2, with a power of approximately 4 GW and at a distance of about 88 km from the KamLAND detector is scheduled to start operating in March 2006. We study the impact of the $\barν_e$ flux from this reactor on the sensitivity of the KamLAND experiment to the solar neutrino oscillation parameters. We present results on prospective determination of $Δm^2_\odot$ and $\sin^2θ_\odot$ using the combined data from KamLAND and the solar neutrino experiments, including the effect of the Shika-2 contribution to the KamLAND signal and the latest data from the salt enriched phase of the SNO experiment. We find that contrary to the expectations, the addition of the Shika-2 reactor flux does not improve the $\sin^2θ_\odot$ sensitivity of KamLAND, while the ambiguity in $Δm^2_\odot$ measurement may even increase, as a result of the averaging effect between Kashiwazaki and the Shika-2 reactor contributions to the KamLAND signal.

hep-ph↗

arXiv2003

Testing the solar LMA region with KamLAND data

We investigate the potential of 3 kiloTon-years(kTy) of KamLAND data to further constrain the $Δm^2$ and $\tan^2θ$ values compared to those presently allowed by existing KamLAND and global solar data. We study the extent, dependence and characteristics of this sensitivity in and around the two parts of the LMA region that are currently allowed. Our analysis with 3 kTy simulated spectra shows that KamLAND spectrum data by itself can constrain $Δm^2$ with high precision. Combining the spectrum with global solar data further tightens the constraints on allowed values of $\tan^2θ$ and $Δm^2$. We also study the effects of future neutral current data with a total error of 7% from the Sudbury Neutrino Observatory. We find that these future measurements offer the potential of considerable precision in determining the oscillation parameters (specially the mass parameter).

hep-ph↗

arXiv2003

Exploring the sensitivity of current and future experiments to $θ_{\odot}$

However the allowed range of $θ_{\odot}$ ($θ_{12}$) did not change much with the inclusion of the KamLAND results. In this paper we probe if future data from KamLAND can increase the accuracy of the allowed range in $θ_{\odot}$ and conclude that even after 3 kton-year of statistics and most optimistic error estimates, KamLAND {\it may} find it hard to significantly improve the bounds on the mixing angle obtained from the solar neutrino data. We discuss the $θ_{12}$ sensitivity of the survival probabilities in matter (vacuum) as is relevant for the solar (KamLAND) experiments. We find that the presence of matter effects in the survival probabilities for $^8B$ neutrinos give the solar neutrino experiments SK and SNO an edge over KamLAND, as far as $θ_{12}$ sensitivity is concerned, particularly near maximal mixing. Among solar neutrino experiments we identify SNO as the most promising candidate for constraining $θ_{12}$ and make a projected sensitivity test for the mixing angle by reducing the error in the neutral current measurement at SNO. Finally we argue that the most accurate bounds on $θ_{12}$ can be achieved in a reactor experiment, if the corresponding baseline and energy can be tuned to a minimum in the survival probability. We propose a new reactor experiment which can give the value of $\tan^2θ_{12}$ to within 14%. We also discuss the future Borexino and LowNu experiments.

hep-ph↗

arXiv2003

The Solar Neutrino Problem after the first results from Kamland

The first results from the KamLAND experiment have provided confirmational evidence for the Large Mixing Angle (LMA) MSW solution to the solar neutrino problem. We do a global analysis of solar and the recently announced KamLAND data (both rate and spectrum) and investigate its effect on the allowed region in the $Δm^2-\tan^2θ$ plane. The best-fit from a combined analysis which uses the KamLAND rate plus global solar data comes at $Δm^2 = 6.06 \times 10^{-5}$ eV $^2$ and $\tan^2θ=0.42$, very close to the global solar best-fit, leaving a large allowed region within the global solar LMA contour. The inclusion of the KamLAND spectral data in the global fit gives a best-fit $Δm^2 = 7.15 \times 10^{-5}$ eV $^2$ and $\tan^2θ=0.42$ and constrains the allowed areas within LMA, leaving essentially two allowed zones. Maximal mixing though allowed by the KamLAND data alone is disfavored by the global solar data and remains disallowed at about $3σ$. The LOW solution is now ruled out at about 5$σ$ w.r.t. the LMA solution.

hep-ph↗

arXiv2002

Neutrino decay confronts the SNO data

We investigate the status of the neutrino decay solution to the solar neutrino problem in the context of the recent results from Sudbury Neutrino Observatory (SNO). We present the results of global $χ^2$-analysis for both two and three generation cases with one of the mass states being allowed to decay and include the effect of both decay and mixing. We find that the Large Mixing Angle (LMA) region which is the currently favoured solution of the solar neutrino problem is affected significantly by decay. We present the allowed areas in the $Δm^2-\tan^2θ$ plane for different allowed values of $α$ and examine how these areas change with the inclusion of decay. We obtain bounds on the decay constant $α$ in this region which implies a rest frame life time $τ_0/m_{2} > 8.7 \times 10^{-5}$ sec/eV for the unstable neutrino state. We conclude that the arrival of the neutral current results from SNO further disfavors the neutrino decay solution to the solar neutrino problem leaving a very small window for the decay constant $α$ which could still be allowed.

hep-ph↗

arXiv2002

SNO and the solar neutrino problem

We study the implication of the first neutral current (NC) data from SNO. We perform model independent and model dependent analyses of the solar neutrino data. The inclusion of the first SNO NC data in the model independent analysis determines the allowed ranges of $^{8}{B}$ flux normalization and the $ν_e$ survival probability more precisely than what was possible from the SK and SNO CC combination. Transitions to pure sterile states are seen to be hugely disfavored however transition to ``mixed'' states are still viable with a probability of finding about 30% sterile component in the resultant beam at $1σ$. We perform global $ν_e-ν_{active}$ oscillation analyses of solar neutrino data including the recent SNO results. LMA emerges as a huge favorite while LOW appears at the $3σ$ level. All the other solutions are disfavored at $3σ$ while SMA is virtually ruled out. Maximal mixing is disfavored at $3σ$. We explore in some details the reasons for the incompatibility of the maximal mixing solution and the LOW solution with the global solar neutrino data.

hep-ph↗

arXiv2002

Implications of the first neutral current data from SNO for Solar Neutrino Oscillation

We perform model independent and model dependent analyses of solar neutrino data including the neutral current event rate from SNO. The inclusion of the first SNO NC data in the model independent analysis determines the allowed ranges of $^{8}{B}$ flux normalisation and the $ν_e$ survival probability more precisely than what was possible from the SK and SNO CC combination. We perform global $ν_e-ν_{active}$ oscillation analyses of solar neutrino data using the NC rate instead of the SSM prediction for the $^{8}{B}$ flux, in view of the large uncertainty in the latter. The LMA gives the best solution, while the LOW solution is allowed only at the $3σ$ level.

hep-ph↗

arXiv2002

What can the SNO Neutral Current Rate teach us about the Solar Neutrino Anomaly

We investigate how the anticipated neutral current rate from $SNO$ will sharpen our understanding of the solar neutrino anomaly. Quantitative analyses are performed with representative values of this rate in the expected range of $0.8 - 1.2$. This would provide a $5 - 10 σ$ signal for $ν_e$ transition into a state containing an active neutrino component. Assuming this state to be purely active one can estimate both the $^8B$ neutrino flux and the $ν_e$ survival probability to a much higher precision than currently possible. Finally the measured value of the $NC$ rate will have profound implications for the mass and mixing parameters of the solar neutrino oscillation solution.

hep-ph↗

arXiv2002

Three Generation Neutrino Oscillation Parameters after SNO

We examine the solar neutrino problem in the context of the realistic three neutrino mixing scenario including the SNO charged current (CC) rate. The two independent mass squared differences $Δm^2_{21}$ and $Δm^2_{31} \approx Δm^2_{32}$ are taken to be in the solar and atmospheric ranges respectively. We incorporate the constraints on $Δ$m$^2_{31}$ as obtained by the SuperKamiokande atmospheric neutrino data and determine the allowed values of $Δm^2_{21}$, $θ_{12}$ and $θ_{13}$ from a combined analysis of solar and CHOOZ data. Our aim is to probe the changes in the values of the mass and mixing parameters with the inclusion of the SNO data as well as the changes in the two-generation parameter region obtained from the solar neutrino analysis with the inclusion of the third generation. We find that the inclusion of the SNO CC rate in the combined solar + CHOOZ analysis puts a more restrictive bound on $θ_{13}$. Since the allowed values of $θ_{13}$ are constrained to very small values by the CHOOZ experiment there is no qualitative change over the two generation allowed regions in the $Δm^2_{21} - \tan^2 θ_{12}$ plane. The best-fit comes in the LMA region and no allowed area is obtained in the SMA region at 3$σ$ level from combined solar and CHOOZ analysis.

hep-ph↗

arXiv2001

Impact of the first SNO results on Neutrino Mass and Mixing

We investigate the implications of the SNO charged-current (CC) and electron scattering (ES) measurements of solar \br neutrino fluxes for neutrino mass and mixing parameters by performing a global and unified $χ^2$ analysis of the solar neutrino data in the framework of two neutrino mixing. We consider both $ν_e -ν_{active}$ and $ν_e -ν_{sterile}$ solutions and perform (i) analysis of the total rates data of Cl, Ga, SK and SNO experiments and (ii) global analysis including the total rates data, the recoil electron spectrum data of SK and the CC spectrum observed at SNO. For the $ν_e-ν_{active}$ case the inclusion of the SNO results in the analysis of the total rates reduces(enhances) the goodness-of-fit (GOF) of the SMA(LMA) solution. The flat spectrum observed at SK further favours the LMA solution over the SMA solution and no allowed area is obtained in the SMA region at 3$σ$ level from the global analysis. For the $ν_e -ν_{sterile}$ case, with the inclusion of the SNO results, all the solutions are disfavoured with a probability of more than 99% from the total rates analysis while for the global analysis the GOF of these become much worse.

hep-ph↗

arXiv2001

MSW mediated neutrino decay and the solar neutrino problem

We investigate the solar neutrino problem assuming simultaneous presence of MSW transitions in the sun and neutrino decay on the way from sun to earth. We do a global $χ^2$-analysis of the data on total rates in Cl, Ga and Superkamiokande (SK) experiments and the SK day-night spectrum data and determine the changes in the allowed region in the $\dm - \tan^2θ$ plane in presence of decay. We also discuss the implications for unstable neutrinos in the SNO experiment.

hep-ph↗