Abhijit Samanta

Exploration prospects of a long baseline beta beam neutrino experiment with an iron calorimeter detector

Abstract A high intensity source of a single neutrino flavour with known spectrum is most desirable for precision measurements, the consensus direction for the future. The beta beam is an especially suitable option for this. We discuss the prospects of a very long baseline beta beam experiment with a magnetized iron calorimeter detector. In particular, with the source at CERN and the detector at the proposed India-based Neutrino Observatory (INO) the baseline is near the ‘magic’ value where the effect of the CP phase is small. We observe that this experiment will be well suited to determine the sign of m 3 2 − m 2 2 and will be capable of probing θ 13 down to about 1°.

The mass hierarchy with atmospheric neutrinos at INO

Abstract We study the neutrino mass hierarchy at the magnetized Iron CALorimeter (ICAL) detector at India-based Neutrino Observatory with atmospheric neutrino events generated by the Monte Carlo event generator Nuance. We judicially choose the observables so that the possible systematic uncertainties can be reduced. The resolution as a function of both energy and zenith angle simultaneously is obtained for neutrinos and anti-neutrinos separately from thousand years un-oscillated atmospheric neutrino events at ICAL to migrate number of events from neutrino energy and zenith angle bins to muon energy and zenith angle bins. The resonance ranges in terms of directly measurable quantities like muon energy and zenith angle are found using this resolution function at different input values of θ 13 . Then, the marginalized χ 2 s are studied for different input values of θ 13 with its resonance ranges taking input data in muon energy and zenith angle bins. Finally, we find that the mass hierarchy can be explored up to a lower value of θ 13 ≈ 5 ° with confidence level >95% in this set up.

Discrimination of the mass hierarchy with atmospheric neutrinos at a magnetized muon detector

We have studied the mass hierarchy with atmospheric neutrinos considering the muon energy and zenith angle of the event at the magnetized iron calorimeter detector. For {chi}{sup 2} analysis we have migrated the number of events from neutrino energy and zenith angle bins to muon energy and zenith angle bins using the two-dimensional energy-angle correlated resolution functions. Then the {chi}{sup 2} is marginalized considering all possible systematic uncertainties of the atmospheric neutrino flux and cross section. The effects of the ranges of oscillation parameters on the marginalization are also studied. The lower limit of the range of {theta}{sub 13} for marginalization is found to be very crucial in determining the sensitivity of hierarchy for a given {theta}{sub 13}. Finally, we show that one can discriminate atmospheric neutrino mass hierarchy at >90% C.L. if the lower limit of {theta}{sub 13{>=}}5 deg.

New bounds on slepton and Wino masses in anomaly mediated supersymmetry breaking models

Supersymmetry (SUSY), if it exists, must be broken, and this breaking cannot take place in the observable sector (OS). Thus one envisages a hidden sector (HS), whose fields are all singlets under the SM gauge group, where SUSY is broken. The key question is how to convey the breaking to the OS. One option is to consider a contact interaction between the HS and the OS fields in the Kahler potential, suppressed by the Planck mass squared. This tree-level interaction induces SUSY breaking in the OS; such models are generically known as supergravity (SUGRA) type models, where the gravitino mass is of the order of 1 TeV. Recently, one came to note that if the OS and the HS live in two distinct 3-branes separated by a finite distance along a fifth compactified dimension, there is no tree-level term in the Kahler potential that transmit SUSY breaking from the HS to the OS. However, a superconformal anomaly may induce the SUSY breaking in the OS (this term is present in the SUGRA type models too, but is suppressed in comparison to the usual softbreaking terms). To generate the weak scale masses of the sparticles, the gravitino mass must be of the order of tens of TeV. Such models are generically known as anomaly-mediated SUSY breaking (AMSB) models [5,6]. AMSB, alongwith the radiative electroweak symmetry breaking condition, should fix the sparticle spectrum completely in terms of three parameters: m3/2 (the mass of the fermionic component of the compensator superfield, and equal to the gravitino mass), tan β (ratio of the vacuum expectation values (VEV) of the two Higgs fields), and sign(� ). The gaugino masses M1, M2 and M3, and the trilinear couplings (generically denoted by A) can be obtained from the relevant renormalization group (RG) β-functions and anomalous dimensions. The sfermion masses, as well as the Higgs mass parameters, are also determined by m3/2; unfortunately, for sfermions that do not couple to asymptotically free gauge groups (i.e., both right and left sleptons), the masses come out to be tachyonic. The remedy is sought by putting a positive definite mass squared term m 2 in the GUT scale boundary conditions. This is not exactly an ad hoc prescription; there are a number of physical motivations for the introduction of such a term, mostly related to the presence of extra field(s) in the bulk. Such models with a universal m0 for all scalars are called the minimal AMSB (mAMSB) models [5,6]. The phenomenology of such models has been at the focus of attention of many recent works [7–12], and we also confine our discussions within the scope of mAMSB models. With four free parameters in the model, one can determine the complete particle spectrum. A few key observations can be immediately made [5–9]: (i) The lighter chargino ˜ χ ± is almost degenerate with the

Probing CPT violation in neutrino oscillation: A three flavor analysis

Abstract We have studied CPT violation in neutrino oscillation considering three flavor framework with matter effect. We have constructed a new way to find the oscillation probability incorporating CPT violating terms without any approximation. Then CPT violation with atmospheric neutrinos for a magnetized iron calorimeter detector considering the muons (directly measurable with high resolution) of the charge current events has been studied for zero and nonzero θ 13 values. It is found that a potential bound of δ b 32 ≲ 6 × 10 − 24 GeV at 99% CL can be obtained with 1 Mton.year exposure of this detector; and unlike neutrino beam experiments, there is no possibility to generate ‘fake’ CPT violation due to matter effect with atmospheric neutrinos. The advantages of atmospheric neutrinos to discriminate CPT violation from CP violation and nonstandard interactions are also discussed.

Comparison of the sensitivities of the parameters with atmospheric neutrinos for different analysis methods

In the atmospheric neutrino experiments the primary problems are the huge uncertainties of flux, very rapid fall of flux with increase of energy, the energy dependent wide resolutions of energy and zenith angle between true neutrinos and reconstructed neutrinos. These all in together make the choice of binning of the data for chi-square analysis complicated. The large iron calorimeter has the ability to measure the energy and the direction of the muon with high resolution. From the bending of the track in the magnetic field it can also distinguish its charge. We have analyzed the atmospheric neutrino oscillation generating events by Nuance and then considering the muons produced in the charge current interactions as the reconstructed neutrinos. This practically takes into account the major problem of wide resolutions. We have binned the data in three ways: (i) in the grids of logE-logL plane, (ii) in the grids of logE-cos{theta}{sub zenith} plane, and (iii) in the bins of log(L/E). We have performed a marginalized {chi}{sup 2} study over {delta}m{sub 32}{sup 2}, {theta}{sub 13} and {theta}{sub 23} for neutrinos and antineutrinos separately for each method and finally compared the results.

The Role and Detectability of the Charm Contribution to Ultra High Energy Neutrino Fluxes

It is widely believed that charm meson production and decay may play an important role in high energy astrophysical sources of neutrinos, especially those that are baryon-rich, providing an environment conducive to pp interactions. Using slow-jet supernovae (SJS) as an example of such a source, we study the detectability of high-energy neutrinos, paying particular attention to those produced from charmed-mesons. We highlight important distinguishing features in the ultra-high energy neutrino flux which would act as markers for the role of charm in the source. In particular, charm leads to significant event rates at higher energies, after the conventional (π,K) neutrino fluxes fall off. We calculate event rates both for a nearby single source and for diffuse SJS fluxes for an IceCube-like detector. By comparing muon event rates for the conventional and prompt fluxes in different energy bins, we demonstrate the striking energy dependence in the rates induced by the presence of charm. We also show that it leads to an energy dependant flux ratio of shower to muon events, providing an additional important diagnostic tool for the presence of prompt neutrinos. Motivated by the infusion of high energy anti-electron neutrinos into the flux by charm decay, we also study the detectability of the Glashow resonance due to these sources.

Prospects of measuring the leptonic CP phase with atmospheric neutrinos

We have studied the prospects of measuring the CP violating phase with atmospheric neutrinos at a large magnetized iron calorimeter detector considering the muons (directly measurable) of the neutrino events generated by a Monte Carlo event generator Nuance. The effect of {theta}{sub 13} and {delta}{sub CP} appears dominantly neither in atmospheric neutrino oscillation nor in solar neutrino oscillation, but appears as subleading in both cases. These are observable in the range of E{approx}1 GeV for atmospheric neutrino, where solar and atmospheric oscillation couple. In this regime, the quasielastic events dominate and the energy resolution is very good, but the angular resolution is very poor. Unlike beam experiments this poor angular resolution acts against its measurements. However, we find that one can be able to distinguish {delta}{sub CP}{approx_equal}0 deg. and 180 deg. at 90% confidence level. We find no significant sensitivity for {delta}{sub CP}{approx_equal}90 deg. or 270 deg.

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.