Prospects of indirect searches for dark matter annihilations in the earth with ICAL@INO

We study the prospects of detecting muon events at the upcoming Iron CALorimeter (ICAL) detector to be built at the proposed India-based Neutrino Observatory (INO) facility due to neutrinos arising out of annihilation of Weakly Interactive Massive Particles (WIMP) in the centre of the earth. The atmospheric neutrinos coming from the direction of earth core presents an irreducible background. We consider 50kt $\times$ 10 years of ICAL running and WIMP masses between 10-100 GeV and present 90 \% C.L. exclusion sensitivity limits on $\sigma_{SI}$ which is the WIMP-nucleon Spin Independent (SI) interaction cross-section. The expected sensitivity limits calculated for ICAL for the WIMP annihilation in the earth are more stringent than the limits obtained by any other indirect detection experiment. For a WIMP mass of ~$52.14 \textup{ GeV}$, where the signal fluxes are enhanced due to resonance capture of WIMP in earth due to Fe nuclei, the sensitivity limits, assuming 100\% branching ratio for each channel, are : $\sigma_{SI} =1.02\times 10^{-44}~cm^2$ for the $\tau^{+} \tau^{-}$ channel and $\sigma_{SI} =5.36\times 10^{-44} ~cm^2$ for the $b ~\bar{b}$ channel.Comment: 20 pages, 1 table and 11 figure

The Reach of INO for Atmospheric Neutrino Oscillation Parameters

The India-based Neutrino Observatory (INO) will host a 50 kt magnetized iron calorimeter (ICAL@INO) for the study of atmospheric neutrinos. Using the detector resolutions and efficiencies obtained by the INO collaboration from a full-detector GEANT4-based simulation, we determine the reach of this experiment for the measurement of the atmospheric neutrino mixing parameters ($\sin^2 \theta_{23}$ and $|\Delta m_{32}^2 |$). We also explore the sensitivity of this experiment to the deviation of $\theta_{23}$ from maximal mixing, and its octant.Comment: 19 pages, 18 pdf figures, Uses pdflate

Neutrino Physics with Non-Standard Interactions at INO

Non-standard neutrino interactions (NSI) involved in neutrino propagation inside Earth matter could potentially alter atmospheric neutrino fluxes. In this work, we look at the impact of these NSI on the signal at the ICAL detector to be built at the India-based Neutrino Observatory (INO). We show how the sensitivity to the neutrino mass hierarchy of ICAL changes in the presence of NSI. The mass hierarchy sensitivity is shown to be rather sensitive to the NSI parameters $\epsilon_{e\mu}$ and $\epsilon_{e\tau}$, while the dependence on $\epsilon_{\mu\tau}$ and $\epsilon_{\tau\tau}$ is seen to be very mild, once the $\chi^2$ is marginalised over oscillation and NSI parameters. If the NSI are large enough, the event spectrum at ICAL is expected to be altered and this can be used to discover new physics. We calculate the lower limit on NSI parameters above which ICAL could discover NSI at a given C.L. from 10 years of data. If NSI were too small, the null signal at ICAL can constrain the NSI parameters. We give upper limits on the NSI parameters at any given C.L. that one is expected to put from 10 years of running of ICAL. Finally, we give C.L. contours in the NSI parameter space that is expected to be still allowed from 10 years of running of the experiment.Comment: 24 pages, minor improvement

Evidence of Conformational Changes in Adsorbed Lysozyme Molecule on Silver Colloids

In this article, we discuss metal-protein interactions in the Ag-lysozyme complex by spectroscopic measurements. The analysis of the variation in relative intensities of SERS bands reveal the orientation and the change in conformation of the protein molecules on the Ag surface with time. The interaction kinetics of metal-protein complexes has been analyzed over a period of three hours via both Raman and absorption measurements. Our analysis indicates that the Ag nanoparticles most likely interact with Trp-123 which is in close proximity to Phe-34 of the lysozyme molecule.Comment: 15 pages, 6 figure

Quantitative Analysis of Hydrogenated DLC Films by Visible Raman Spectroscopy

The correlations between properties of hydrogenated diamond like carbon films and their Raman spectra have been investigated. The films are prepared by plasma deposition technique, keeping different hydrogen to methane ratio during the growth process. The hydrogen concentration, sp$^3$ content, hardness and optical Tauc gap of the materials have been estimated from a detail analysis of their Raman spectra. We have also measured the same parameters of the films by using other commonly used techniques, like sp$^3$ content in films by x-ray photoelectron spectroscopy, their Tauc gap by ellipsometric measurements and hardness by micro-hardness testing. The reasons for the mismatch between the characteristics of the films, as obtained by Raman measurements and by the above mentioned techniques, have been discussed. We emphasize on the importance of the visible Raman spectroscopy in reliably predicting the above key properties of DLC films.Comment: 19 pages, 8 figure

Exploring quantum properties of bipartite mixed states under coherent and incoherent basis

Quantum coherence and quantum entanglement are two different manifestations of the superposition principle. In this article we show that the right choice of basis to be used to estimate coherence is the separable basis. The quantum coherence estimated using the Bell basis does not represent the coherence in the system, since there is a coherence in the system due to the choice of the basis states. We first compute the entanglement and quantum coherence in the two qubit mixed states prepared using the Bell states and one of the states from the computational basis. The quantum coherence is estimated using the l1-norm of coherence, the entanglement is measured using the concurrence and the mixedness is measured using the linear entropy. Then we estimate these quantities in the Bell basis and establish that coherence should be measured only in separable basis, whereas entanglement and mixedness can be measured in any basis. We then calculate the teleportation fidelity of these mixed states and find the regions where the states have a fidelity greater than the classical teleportation fidelity. We also examine the violation of the Bell-CHSH inequality to verify the quantum nonlocal correlations in the system. The estimation of the above mentioned quantum correlations, teleportation fidelity and the verification of Bell-CHSH inequality is also done for bipartite states obtained from the tripartite systems by the tracing out of one of their qubits. We find that for some of these states teleportation is possible even when the Bell-CHSH inequality is not violated, signifying that nonlocality is not a necessary condition for quantum teleportation.Comment: 18 pages, 3 figure