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Sandhya Choubey

Publications and source records attributed to Sandhya Choubey.

At least 91 records · Page 5Linked to original sources
arXiv2008

Unraveling neutrino parameters with a magical beta-beam experiment at INO

We expound in detail the physics reach of an experimental set-up in which the proposed large magnetized iron detector at the India-based Neutrino Observatory (INO) would serve as the far detector for a so-called beta-beam. If this pure $\nue$ and/or $\anue$ beam is shot from some source location like CERN such that the source-detector distance $L \simeq 7500$ km, the impact of the CP phase $δ_{CP}$ on the oscillation probability and associated parameter correlation and degeneracies are almost negligible. This ``magical'' beta-beam experiment would have unprecedented sensitivity to the neutrino mass hierarchy and $θ_{13}$, two of the missing ingredients needed for our understanding of the neutrino sector. With Lorentz boost $γ=650$ and irrespective of the true value of $δ_{CP}$, the neutrino mass hierarchy could be determined at $3σ$ C.L. if $\sin^22θ_{13}{\rm {(true)}} > 5.6 \times 10^{-4}$ and we can expect an unambiguous signal for $θ_{13}$ at $3σ$ C.L. if $\sin^22θ_{13}{\rm {(true)}} > 5.1 \times 10^{-4}$ independent of the true neutrino mass hierarchy.

hep-ph↗
arXiv2007

Physics with Beta-Beam

A Beta-beam would be a high intensity source of pure $ν_e$ and/or $\barν_e$ flux with known spectrum, ideal for precision measurements. Myriad of possible set-ups with suitable choices of baselines, detectors and the beta-beam neutrino source with desired energies have been put forth in the literature. In this talk we present a comparitive discussion of the physics reach of a few such experimental set-ups.

hep-ph↗
arXiv2007

Signature of sterile species in atmospheric neutrino data at neutrino telescopes

The MiniBooNE results have still not been able to comprehensively rule out the oscillation interpretation of the LSND experiment. So far the so-called short baseline experiments with energy in the MeV range and baseline of few meters have been probing the existence of sterile neutrinos. We show how signatures of these extra sterile states could be obtained in TeV energy range atmospheric neutrinos travelling distances of thousands of kilometers. Atmospheric neutrinos in the TeV range would be detected by the upcoming neutrino telescopes. Of course vacuum oscillations of these neutrinos would be very small. However, we show that resonant matter effects inside the Earth could enhance these very tiny oscillations into near-maximal transitions, which should be hard to miss. We show that imprint of sterile neutrinos could be unambiguously obtained in this high energy atmospheric neutrino event sample. Not only would neutrino telescopes tell the presence of sterile neutrinos, it should also be possible for them to distinguish between the different possible mass and mixing scenarios with additional sterile states.

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arXiv2007

Confusing Sterile Neutrinos with Deviation from Tribimaximal Mixing at Neutrino Telescopes

We expound the impact of extra sterile species on the ultra high energy neutrino fluxes in neutrino telescopes. We use three types of well-known flux ratios and compare the values of these flux ratios in presence of sterile neutrinos, with those predicted by deviation from the tribimaximal mixing scheme. We show that in the upcoming neutrino telescopes, its easy to confuse between the signature of sterile neutrinos with that of the deviation from tribimaximal mixing. We also show that if the measured flux ratios acquire a value well outside the range predicted by the standard scenario with three active neutrinos only, it might be possible to tell the presence of extra sterile neutrinos by observing ultra high energy neutrinos in future neutrino telescopes.

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arXiv2007

Magic Baseline Beta Beam

We study the physics reach of an experiment where neutrinos produced in a beta-beam facility at CERN are observed in a large magnetized iron calorimeter (ICAL) at the India-based Neutrino Observatory (INO). The CERN-INO distance is close to the so-called "magic" baseline which helps evade some of the parameter degeneracies and allows for a better measurement of the neutrino mass hierarchy and $θ_{13}$.

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↗
arXiv2007

Neutrino parameters from matter effects in $P_{ee}$ at long baselines

We show that the earth matter effects in the ${\rm {ν_e \to ν_e}}$ survival probability can be used to cleanly determine the third leptonic mixing angle $θ_{13}$ and the sign of the atmospheric neutrino mass squared difference, $Δm^2_{31}$, using a $β$-beam as a $ν_e$ source.

hep-ph↗
arXiv2007

Turbulent Supernova Shock Waves and the Sterile Neutrino Signature in Megaton Water Detectors

The signatures of sterile neutrinos in the supernova neutrino signal in megaton water Cerenkov detectors are studied. Time dependent modulation of the neutrino signal emerging from the sharp changes in the oscillation probability due to shock waves is shown to be a smoking gun for the existence of sterile neutrinos. These modulations and indeed the entire neutrino oscillation signal is found to be different for the case with just three active neutrinos and the cases where there are additional sterile species mixed with the active neutrinos. The effect of turbulence is taken into account and it is found that the effect of the shock waves, while modifed, remain significant and measurable. Supernova neutrino signals in water detectors can therefore give unambiguous proof for the existence of sterile neutrinos, the sensitivity extending beyond that for terrestial neutrino experiments. In addition the time dependent modulations in the signal due to shock waves can be used to trace the evolution of the shock wave inside the supernova.

hep-ph↗
arXiv2007

Neutrino mass hierarchy and $θ_{13}$ with a magic baseline beta-beam experiment

We underscore the physics advantage of an experiment where neutrinos produced in a beta-beam facility at CERN are observed in a large magnetized iron calorimeter (ICAL) at the India-based Neutrino Observatory (INO). The CERN-INO distance is close to the so-called "magic" baseline which helps evade some of the parameter degeneracies and allows for a better measurement of the neutrino mass hierarchy and $θ_{13}$. We expound the possibility of using radioactive $^8B$ and $^{8}Li$ as the source isotopes for the $\nue$ and $\anue$ beta-beam, respectively, and show that very good sensitivity to both the mass hierarchy and $θ_{13}$ is possible with a boost $γ$ in the 250-500 ballpark.

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arXiv2006

Modified Zee mass matrix with zero-sum condition

We modify the Zee mass matrix by adding a real one parameter perturbation which is purely diagonal and trace-less. We show that in this way we can explain both solar and atmospheric neutrino oscillation data. There is a correlation between the deviation from strict maximality of $|U_{μ3}|= 1/\sqrt{2}$, with the emergence of a small but non-zero $U_{e3}$. We calculate how big a value can $U_{e3}$ get when we restrict ourselves within the allowed regions of solar and atmospheric neutrino masses and mixing angles. We also discuss the impact of a $S_2$ permutation symmetry on our mass matrix and show how a small $U_{e3} \ne 0$ can emerge when this $S_2$ permutation symmetry between the second and the third generation is broken.

hep-ph↗
arXiv2006

Probing neutrino oscillations from supernovae shock waves via the IceCube detector

The time dependent neutrino oscillation signals due to the passage of a shock wave through the supernovae are analyzed for the case of three active neutrinos and also for the case that there are two additional sterile neutrinos. It is shown that, even without flavour identification and energy measurement, detailed information about the masses and mixing angles of the neutrinos may be obtained with a detector with excellent time resolution such as IceCube. Such a signal would also give important information about the nature of the shock wave within the supernovae.

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arXiv2006

What we can learn from atmospheric neutrinos

Physics potential of future measurements of atmospheric neutrinos is explored. Observation of $Δm^2_{21}$ driven sub-dominant effects and $θ_{13}$ driven large matter effects in atmospheric neutrinos can be used to study the deviation of $θ_{23}$ from maximality and its octant. Neutrino mass hierarchy can be determined extremely well due to the large matter effects. New physics can be constrained both in standard atmospheric neutrino experiments as well as in future neutrino telescopes.

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↗
arXiv2006

Probing the deviation from maximal mixing of atmospheric neutrinos

Pioneering atmospheric muon neutrino experiments have demonstrated the near-maximal magnitude of the flavor mixing angle $θ_{23}$. But the precise value of the deviation $D \equiv 1/2 - \sin^2 θ_{23}$ from maximality (if nonzero) needs to be known, being of great interest -- especially to builders of neutrino mass and mixing models. We quantitatively investigate in a three generation framework the feasibility of determining $D$ in a statistically significant manner from studies of the atmospheric $ν_μ,\barν_μ$ survival probability including both vacuum oscillations and matter effects. We show how this determination will be sharpened by considering the up-down ratios of observed $ν_μ$- and $\barν_μ$-induced events and the differences of these ratios in specified energy and zenith angle bins. We consider 1 Megaton year of exposure to a magnetized iron calorimeter such as the proposed INO detector ICAL, taking into account both energy and zenith angle resolution functions. The sensitivity of such an exposure and the dependence of the determination of $D$ on the concerned oscillation parameters are discussed in detail. The vital use of matter effects in fixing the octant of $θ_{23}$ is highlighted.

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arXiv2005

Probing the neutrino mass matrix in next generation neutrino oscillation experiments

We review the current status of the neutrino mass and mixing parameters needed to reconstruct the neutrino mass matrix. A comparative study of the precision in the measurement of oscillation parameters expected from the next generation solar, atmospheric, reactor and accelerator based experiments is presented. We discuss the potential of $0νββ$ experiments in determining the neutrino mass hierarchy and the importance of a better $θ_{12}$ measurement for it.

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↗
arXiv2005

A Flavor Symmetry for quasi-degenerate Neutrinos: L_mu-L_tau

We consider the flavor symmetry L_mu - L_tau for the neutrino mass matrix. The most general neutrino mass matrix conserving L_mu - L_tau predicts quasi-degenerate neutrino masses with one maximal and two zero mixing angles. The presence of L_mu - L_tau can also be motivated by the near-bimaximal form of the neutrino mixing matrix. Furthermore, it is a special case of mu-tau symmetric mass matrices. Breaking the flavor symmetry by adding a small flavor-blind term to the neutrino mass matrix and/or by applying radiative corrections is shown to reproduce the observed neutrino oscillation phenomenology. Both the normal and inverted mass ordering can be accommodated within this scheme. Moderate cancellation for neutrinoless double beta decay is expected. The observables U_{e3}^2 and |1/2 - \sin^2θ_{23}| are proportional to the inverse of the fourth power of the common neutrino mass scale. We comment on whether the atmospheric neutrino mixing is expected to lie above or below pi/4. We finally present a model based on the see-saw mechanism which generates a light neutrino mass matrix with an (approximate) L_mu - L_tau flavor symmetry. This is a minimal model with just one standard Higgs doublet and three heavy right-handed neutrinos. It needs only small values for the soft L_mu - L_tau breaking terms to reproduce the phenomenological viable mass textures analyzed.

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