arXiv subjects

D. Indumathi

Publications and source records attributed to D. Indumathi.

At least 37 records · Page 2Linked to original sources

arXiv2015

Simulation studies of hadron energy resolution as a function of iron plate thickness at INO-ICAL

We report on a detailed simulation study of the hadron energy resolution as a function of the thickness of the absorber plates for the proposed Iron Calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO). We compare the hadron resolutions obtained with absorber thicknesses in the range 1.5--8 cm for neutrino interactions in the energy range 2--15 GeV, which is relevant to hadron production in atmospheric neutrino interactions. We find that at lower energies, the thickness dependence of energy resolution is steeper than at higher energies, however there is a thickness-independent contribution that dominates at the lower thicknesses discussed in this work. As a result, the gain in hadron energy resolution with decreasing plate thickness is marginal. We present the results in the form of fits to a function with energy-dependent exponent.

physics.ins-det↗

arXiv2014

A Simulations Study of the Muon Response of the Iron Calorimeter Detector at the India-based Neutrino Observatory

The magnetised Iron CALorimeter detector (ICAL), proposed to be built at the India-based Neutrino Observatory (INO), is designed to study atmospheric neutrino oscillations. The ICAL detector is optimized to measure the muon momentum, its direction and charge. A GEANT4-based package has been developed by the INO collaboration to simulate the ICAL geometry and propagation of particles through the detector. The simulated muon tracks are reconstructed using the Kalman Filter algorithm. Here we present the first study of the response of the ICAL detector to muons using this simulations package to determine the muon momentum and direction resolutions as well as their reconstruction and charge identification efficiencies. For 1-20 GeV/c muons in the central region of the detector, we obtain an average angle-dependent momentum resolution of 9-14%, an angular resolution of about a degree, reconstruction efficiency of about 80% and a correct charge identification of about 98%.

physics.ins-det↗

arXiv2013

Hadron energy response of the Iron Calorimeter detector at the India-based Neutrino Observatory

The results of a Monte Carlo simulation study of the hadron energy response for the magnetized Iron CALorimeter detector, ICAL, proposed to be located at the India-based Neutrino Observatory (INO) is presented. Using a GEANT4 modeling of the detector ICAL, interactions of atmospheric neutrinos with target nuclei are simulated. The detector response to hadrons propagating through it is investigated using the hadron hit multiplicity in the active detector elements. The detector response to charged pions of fixed energy is studied first, followed by the average response to the hadrons produced in atmospheric neutrino interactions using events simulated with the NUANCE event generator. The shape of the hit distribution is observed to fit the Vavilov distribution, which reduces to a Gaussian at high energies. In terms of the parameters of this distribution, we present the hadron energy resolution as a function of hadron energy, and the calibration of hadron energy as a function of the hit multiplicity. The energy resolution for hadrons is found to be in the range 85% (for 1GeV) -- 36% (for 15 GeV).

physics.ins-det↗

arXiv2013

Vector meson fragmentation using a model with broken SU(3) at the Next-to-Leading Order

A detailed study of fragmentation of vector mesons at the next-to-leading order (NLO) is given for e^+ e^- scattering. A model with broken SU(3) symmetry uses three input fragmentation functions α(x, Q^2), β(x,Q^2) and γ(x,Q^2) and a strangeness suppression parameter λto describe all the light quark fragmentation functions for the entire vector meson octet. At a starting low energy scale of Q_0^2 = 1.5 GeV^2 for three light quarks (u, d, s) along with initial parameterization, the fragmentation functions are evolved through DGLAP evolution equations at NLO and the cross-section is calculated. The heavy quarks contribution are added in appropriate thresholds during evolution. The results obtained are fitted at the momentum scale of \sqrt{s}= 91.2 GeV for LEP and SLD data. Good-quality fits are obtained for ρ, K^*, ωand ϕmesons, implying the consistency and efficiency of this model that explains the fragmentation functions of vector mesons both at the leading and the next to leading order in QCD. Keywords: vector meson, fragmentation, SU(3) symmetry, NLO .

hep-ph↗

arXiv2012

Study of vector meson fragmentation using a broken SU(3) model

Inclusive hadro production in e^+ e^- annihilation processes is examined to study the fragmentation process. A broken SU(3) model is used to determine the quark and gluon fragmentation functions of octet vector mesons, ρand K^*, in a simple way with an SU(3) breaking parameter λ. These are expressed in terms of just two light quark fragmentation functions, V(x, Q2) and γ(x, Q2) and the gluon fragmentation function Dg(x, Q2). These functions are parameterized at the low input scale of Q0^2 = 1.5 GeV2, evolved through LO DGLAP evolution including charm and bottom flavour at appropriate thresholds, and fitted by comparison with data at the Z-pole. The model is extended with the introduction of a few additional parameters to include a study of singlet--octet mixing and hence ωand ϕfragmentation. The model gives good fits to the available data for x >~ 0.01, where x is the scaled energy of the hadron. The model is then applied successfully to ω, ϕproduction in pp collisions at the Relativistic Heavy Ion Collider, RHIC; these data form an important base-line for the study of Quark Gluon Plasma in heavy nucleus collisions at RHIC, and also in future at the LHC.

hep-ph↗

arXiv2011

Group velocity of neutrino waves

We follow up on the analysis of Mecozzi and Bellini (arXiv:1110:1253v1) where they showed, in principle, the possibility of superluminal propagation of neutrinos, as indicated by the recent OPERA result. We refine the analysis by introducing wave packets for the superposition of energy eigenstates and discuss the implications of their results with realistic values for the mixing and mass parameters in a full three neutrino mixing scenario. Our analysis shows the possibility of superluminal propagation of neutrino flavour in a very narrow range of neutrino parameter space. Simultaneously this reduces the number of observable events drastically. Therefore, the OPERA result cannot be explained in this frame-work.

hep-ph↗

arXiv2011

Interim Design Report

The International Design Study for the Neutrino Factory (the IDS-NF) was established by the community at the ninth "International Workshop on Neutrino Factories, super-beams, and beta- beams" which was held in Okayama in August 2007. The IDS-NF mandate is to deliver the Reference Design Report (RDR) for the facility on the timescale of 2012/13. In addition, the mandate for the study [3] requires an Interim Design Report to be delivered midway through the project as a step on the way to the RDR. This document, the IDR, has two functions: it marks the point in the IDS-NF at which the emphasis turns to the engineering studies required to deliver the RDR and it documents baseline concepts for the accelerator complex, the neutrino detectors, and the instrumentation systems. The IDS-NF is, in essence, a site-independent study. Example sites, CERN, FNAL, and RAL, have been identified to allow site-specific issues to be addressed in the cost analysis that will be presented in the RDR. The choice of example sites should not be interpreted as implying a preferred choice of site for the facility.

hep-ex↗

arXiv2011

Tau contamination in the platinum channel at neutrino factories

The platinum channel (ν_e or anti-ν_e appearance) has been proposed at neutrino factories as an additional channel that could help in lifting degeneracies and improving sensitivities to neutrino oscillation parameters, viz., θ_{13}, δ_{CP}, mass hierarchy, deviation of θ_{23} from maximality and its octant. This channel corresponds to ν_μ-> ν_e (or the corresponding anti-particle) oscillations of the initial neutrino flux, with the subsequent detection of (positrons) electrons from charged current interactions of the (anti-) ν_e in the detector. For small values of θ_{13}, the dominant ν_μ\to ν_τ(or corresponding anti-particle) oscillation results in this signal being swamped by electrons arising from the leptonic decay of taus produced in charge-current interactions of ν_τ(anti-ν_τ) with the detector. We examine for the first time the role of this tau contamination to the electron events sample and find that it plays a significant role in the platinum channel compared to other channels, not only at high energy neutrino factories but surprisingly even at low energy neutrino factories. Even when the platinum channel is considered in combination with other channels such as the golden (muon appearance) or muon disappearance channel, the tau contamination results in a loss in precision of the measured parameters.

hep-ph↗

arXiv2009

Effect of tau neutrino contribution to muon signals at neutrino factories

We discuss precision measurements of the leading atmospheric parameters at a standard neutrino factory with a detector that is sensitive to muons alone. The oscillation of the muon- and electron neutrinos in the neutrino factory beam to tau neutrinos adds to the muon events sample (both right sign and wrong sign) via leptonic decays of the taus produced through charge-current interactions in the detector. In particular, we study how this affects a precision measurement of the atmospheric mixing parameters and the deviation of nu_mu <--> nu_tau mixing from maximality. In spite of the enhancement of the number of events due to the additional tau contribution, the determination of the atmospheric mixing angle and the deviation from maximality will be poorer. We show that it is impossible to devise satisfactory cuts to remove this tau contamination. Neglect of these tau contributions will lead to an incorrect conclusion about the precision obtainable at such a neutrino factory.

hep-ph↗

arXiv2009

Tau contribution and precision measurement of theta23 at a neutrino factory

We discuss precision measurements of the leading atmospheric parameters at a standard neutrino factory. The oscillation of the muon and electron neutrinos (anti-neutrinos) to tau neutrinos (anti-neutrinos) adds to the muon events sample (both right sign and wrong sign) via leptonic decays of the taus produced through charge-current interactions in the detector. We focus on how this contribution affects a precision measurement of the atmospheric mixing parameters and the deviation of muon neutrino -- tau neutrino mixing from maximality.

hep-ph↗

arXiv2009

An extended model for nonet pseudo-scalar meson fragmentation

An SU(3) symmetric model with high predictivity for octet meson (π, K) quark fragmentation functions with a simple approach to SU(3) symmetry breaking (due to the relatively heavy strange quarks) is extended to the singlet sector, with some reasonable assumptions, in order to study ηand η' fragmentation. Due to the presence of SU(3) symmetry, fits to the πand K data help to constrain the fragmentation functions for ηand η' mesons. The use of 2-jet and 3-jet (especially the gluon jet) inclusive meson production in e^+e^- collisions and π, ηinclusive production in p p collisions enable the extraction of the gluon fragmentation functions as well. While sea quarks in strange mesons (K^{+-},K^0,Kbar^0) and the heavier η, η' mesons are suppressed by a factor of lambda_H = m_π^2/m_H^2 < 0.1 for H=K,η,η', the gluons are not as severely suppressed: f_g^H=0.3--0.35. A detailed parametrisation of the three independent fragmentation functions V(x, Q2), γ(x, Q2), and D_g(x, Q2) are given in LO QCD; all nonet meson gluon fragmentation functions and quark fragmentation functions of all flavours can be expressed in terms of these functions with a few model parameters including λ_H and f_g. The data prefer a nonet mixing angle -24deg<=θ_P<=-16deg and rule out no-mixing.

hep-ph↗

arXiv2006

Neutrino oscillation probabilities: Sensitivity to parameters

We study in detail the sensitivity of neutrino oscillation probabilities to the fundamental neutrino parameters and their possible determination through experiments. The first part of the paper is devoted to the broad theme of isolating regions in the neutrino (and anti-neutrino) energy and propagation length that are sensitive to the oscillation parameters. Such a study is relevant to neutrinos both from the Earth's atmosphere or from a neutrino factory. For completeness we discuss the sensitivity, however small, to the parameters involved in a three-generation framework, and to the Earth matter density profile. We then study processes relevant to atmospheric neutrinos which are sensitive to and allow precision measurements of the mixing angle theta_23 and mass-squared difference delta_32 apart from the mixing angle theta_13. Crucial to this analysis is charge identification; detectors having this capability can isolate these matter effects. In particular, we address the issue of using matter effects to determine whether the mixing angle theta_23 is maximal, and, if not, to explore how well its octant can be determined. When realistic detector resolutions are included, we find that deviations of about 15% (20%) from a maximal value of sin^2 theta_23=1/2 can be measured at 95% (99%) CL provided theta_13 is non-zero, sin^2 theta_13 >= 0.015, and the neutrino mass ordering is normal, with fairly large exposures of 1000 kton-years.

hep-ph↗

arXiv2004

A question of hierarchy: matter effects with atmospheric neutrinos and anti-neutrinos

It is by now established that neutrinos mix, have (different) non-zero masses, and therefore oscillate. The oscillation parameters themselves, however, are not all well-known. An open problem is that of the neutrino mass hierarchy. We study the possibility of determining the neutrino mass hierarchy with atmospheric neutrinos using an iron calorimeter detector capable of charge identification such as the proposed MONOLITH and ICAL/INO detectors. We find that such detectors are sensitive to the sign of the mass-squared difference, δ_{32} = m_3^2 - m_2^2, provided the as-yet unknown mixing angle between the first and third generations, θ_{13}, is greater than 6 degrees (\sin^2 2θ_{13} > 0.04). A result with a significance greater than 90% CL requires large exposures (more than 500 kton-years) as well as good energy and angular resolution of the detected muons (better than 15%), especially for small θ_{13}. Hence obtaining definitive results with such a detector is difficult, unless θ_{13} turns out to be large. In contrast, such detectors can establish a clear oscillation pattern in atmospheric neutrinos in about 150 kton-years, therefore determining the absolute value of δ_{32} and \sin^2 2 θ_{23} to within 10%.

hep-ph↗

arXiv2004

Working Group Report: Neutrino and Astroparticle Physics

This is the report of neutrino and astroparticle physics working group at WHEPP-8. We present the discussions carried out during the workshop on selected topics in the above fields and also indicate progress made subsequently. The neutrino physics subgroup studied the possibilites of constraining neutrino masses, mixing and CPT violation in lepton sector from future experiments. Neutrino mass models in the context of abelian horizontal symmetries, warped extra dimensions and in presence of triplet Higgs were studied. Effect of threshold corrections on radiative magnification of mixing angles was investigated. The astroparticle physics subgroup focused on how various particle physics inputs affect the CMBR fluctuation spectrum, and on brane cosmology. This report also contains an introduction on how to use the publicly available code CMBFAST to calculate the CMBR fluctuations.

hep-ph↗

arXiv2003

Random sampling of an AC source: A tool to teach probabilistic observations

An undergraduate level experiment is described to demonstrate the role of probabilistic observations in physics. A capacitor and a DC voltmeter are used to randomly sample an AC voltage source. The resulting probability distribution is analyzed to extract information about the AC source. Different characteristic probability distributions arising from various AC waveforms are calculated and experimentally measured. The reconstruction of the AC waveform is demonstrated from the measured probability distribution under certain restricted circumstances. The results are also compared with a simulated data sample. We propose this as a pedagogical tool to teach probabilistic measurements and their manipulations.

physics.ed-ph↗

arXiv2002

Implications on neutrino oscillation plus decay from recent solar neutrino data

Recently the Sudbury Neutrino Observatory (SNO) has measured both the rates as well as the day-night asymmetries in the flux of neutrinos from the Sun in the charged-current (CC), neutral-current (NC) and elastic scattering (ES) channels. Motivated by the small but negative day-night asymmetry in the NC channel at SNO (1.2 standard deviations away from zero), we consider whether such a non-zero asymmetry can be generated in a framework where active neutrinos can both oscillate and decay, since the NC day-night asymmetry is zero in a frame-work that includes pure oscillations of active flavours. We find that the neutral current day-night asymmetry is strictly zero when we include both oscillations and decay. The result holds for arbitrary number of active neutrino species, with some reasonable assumptions on the decay parameters. Hence, a non-zero asymmetry in the neutral current sector, if it survives, can only come from oscillations/decay into sterile flavours. We also examine the allowed region of parameter space coming from a combined analysis of the total event rates in the charged-current, neutral current and elastic scattering sectors in a two-flavour framework, and find that the neutral current rates are most sensitive to (and hence restrict considerably) the allowed values of the decay parameter involving the life-time of the heavier mass eigenstate to $τ_{2_0} > 10^{-4}$ s for eV mass neutrinos.

hep-ph↗

arXiv2002

Implications of recent solar neutrino observations: an analysis of charged current data

We have analysed the recent results from the observation of charged current ν_e d \to e^- p p events from solar neutrinos by the Sudbury Neutrino Observatory SNO assuming neutrino oscillations with three active flavours. The data seem to prefer a low mass-squared difference and large mixing angle solution (the so-called LOW solution) in (12) parameter space. However, when combined with the Gallium charged current interaction data from Gallex and GNO, distinct (1σ) allowed regions corresponding to the large mixing angle (LMA) and small mixing angle (SMA) appear while the LOW solution is disfavoured upto 3σstandard deviation. The physical electron neutrino survival probability corresponding to these best fit solutions are then determined and analysed for their energy dependence.

hep-ph↗

arXiv2001

J/ψproduction through resolved photon processes at e+ e- colliders

We consider J/psi photoproduction in e+ e- as well as linear photon colliders. We find that the process is dominated by the resolved photon channel. Both the once-resolved and twice-resolved cross-sections are sensitive to (different combinations of) the colour octet matrix elements. Hence, this may be a good testing ground for colour octet contributions in NRQCD. On the other hand, the once-resolved J/psi production cross-section, particularly in a linear photon collider, is sensitive to the gluon content of the photon. Hence these cross-sections can be used to determine the parton distribution functions, especially the gluon distribution, in a photon, if the colour octet matrix elements are known.

hep-ph↗