The pressure-amorphized state in zirconium tungstate: a precursor to decomposition

In contrast to widely accepted view that pressure-induced amorphization arises due to kinetic hindrance of equilibrium phase transitions, here we provide evidence that the metastable pressure-amorphized state in zirconium tungstate is a precursor to decomposition of the compound into a mixture of simple oxides. This is from the volume collapse ΔV across amorphization, which is obtained for the first time by measuring linear dimensions of irreversibly amorphized samples during their recovery to the original cubic phase upon isochronal annealing up to 1000 K. The anomalously large ΔV of 25.7 ± 1.2% being the same as that expected for the decomposition indicates that this amorphous state is probably a precursor to kinetically hindered decomposition. A P–T diagram of the compound is also proposed

Constraining nuclear physics parameters with current and future COHERENT data

Motivated by the recent observation of coherent elastic neutrino-nucleus scattering (CE$\nu$NS) at the COHERENT experiment, our goal is to explore its potential in probing important nuclear structure parameters. We show that the recent COHERENT data offers unique opportunities to investigate the neutron nuclear form factor. Our present calculations are based on the deformed Shell Model (DSM) method which leads to a better fit of the recent CE$\nu$NS data, as compared to known phenomenological form factors such as the Helm-type, symmetrized Fermi and Klein-Nystrand. The attainable sensitivities and the prospects of improvement during the next phase of the COHERENT experiment are also considered and analyzed in the framework of two upgrade scenarios.Comment: 13 pages, 5 figures, 2 tables; v2: minor corrections, version to appear in PL

Can there be neutrino oscillation in Gamma-Ray Bursts fireball ?

The central engine which powers the Gamma-Ray Burst (GRB) fireball, produces neutrinos in the energy range of about 5-20 MeV. Fractions of these neutrinos may propagate through the fireball which is far away from the central engine. We have studied the propagation of these neutrinos through the fireball which is contaminated by baryons and have shown that, resonant conversion of neutrinos are possible for the oscillations of nu_e to nu_{mu,tau}, nu_e to nu_s and anti-nu_(mu,tou) to anti-nu_s if the neutrino mass square difference and mixing angle are in the atmospheric and/or LSND range. On the other hand it is probably difficult for neutrinos to have resonant oscillation if the neutrino parameters are in the solar neutrino range. From the resonance condition we have estimated the fireball temperature and the baryon load in it.Comment: 4 pages, two column text, To be published in Phys. Rev.

Multi-GeV neutrinos due to neutro anti-neutron oscillation in Gamma-Ray Burst Fireballs

The long and short gamma-ray bursts are believed to be produced due to collapse of massive stars and merger of compact binaries respectively. All these objects are rich in neutron and the jet outflow from these objects must have a neutron component in it. By postulating the neutron anti-neutron oscillation in the gamma-ray burst fireball, we show that, 19-38 GeV neutrinos and anti-neutrinos can be produced due to annihilation of anti-neutrons with the background neutrons. These neutrinos and anti-neutrinos will be produced before the 5-10 GeV neutrinos due to dynamical decoupling of neutrons from the rest of the fireball. Observation of these neutrinos will shed more light on the nature of the GRB progenitors and also be a unique signature of physics beyond the standard model. A possible way of detecting these neutrinos in future is also discussed.Comment: 4 pages, two columns, revtex styl

Bivariate tt-distribution for transition matrix elements in Breit-Wigner to Gaussian domains of interacting particle systems

Interacting many-particle systems with a mean-field one body part plus a chaos generating random two-body interaction having strength $\lambda$, exhibit Poisson to GOE and Breit-Wigner (BW) to Gaussian transitions in level fluctuations and strength functions with transition points marked by $\lambda=\lambda_c$ and $\lambda=\lambda_F$, respectively; $\lambda_F >> \lambda_c$. For these systems theory for matrix elements of one-body transition operators is available, as valid in the Gaussian domain, with $\lambda > \lambda_F$, in terms of orbitals occupation numbers, level densities and an integral involving a bivariate Gaussian in the initial and final energies. Here we show that, using bivariate $t$-distribution, the theory extends below from the Gaussian regime to the BW regime up to $\lambda=\lambda_c$. This is well tested in numerical calculations for six spinless fermions in twelve single particle states.Comment: 7 pages, 2 figure

High-Q and temperature stable photonic biosensor based on grating waveguides

In this work, analytical modeling and parameter evaluation of a photonic biosensor using cascaded silicon grating waveguides is illustrated. The sensor design consists of two cascaded waveguides with symmetric sidewall gratings to broaden the stop band region of the transmission spectra. In the work, the structure is first analyzed using the transfer matrix method. The parameter values are then optimized to obtain a sharper resonant peak in the center of the stop band. Notably, the resonant band of this structure provides a high Q factor (of 1.544 × 105), which significantly improves the limits of detection. The sensor has been designed to detect the presence of biomaterial material (seen corresponding to a change in refractive index) on its surface by changing the change in device resonant wavelength. In this study, the effect of temperature on the detection of such biomaterials has also been evaluated, as has the temperature sensitivity of the device which is -0.0075nm/oC, over a temperature range of 18 oC to 34 oC

Inflation in minimal left-right symmetric model with spontaneous D-parity breaking

We present a simplest inflationary scenario in the minimal left-right symmetric model with spontaneous D-parity breaking, which is a well motivated particle physics model for neutrino masses. This leads us to connect the observed anisotropies in the cosmic microwave background to the sub-eV neutrino masses. The baryon asymmetry via the leptogenesis route is also discussed briefly.Comment: (v1) 4 pages, 1 figure; (v2) typos corrected; (v3) title and abstract changed, numerical estimates given, minor changes; (v4) 5 pages, relations between the neutrino masses and the CMB fluctuations become more explicit, miscellaneous changes, to appear in Physical Review

Crystal structure of an antibody bound to an immunodominant peptide epitope: novel features in peptide-antibody recognition

The crystal structure of Fab of an Ab PC283 complexed with its corresponding peptide Ag, PS1 (HQLDPAFGANSTNPD), derived from the hepatitis B virus surface Ag was determined. The PS1 stretch Gln2P to Phe7P is present in the Ag binding site of the Ab, while the next three residues of the peptide are raised above the binding groove. The residues Ser11P, Thr12P, and Asn13P then loop back onto the Ag-binding site of the Ab. The last two residues, Pro14P and Asp15P, extend outside the binding site without forming any contacts with the Ab. The PC283-PS1 complex is among the few examples where the light chain complementarity-determining regions show more interactions than the heavy chain complementarity-determining regions, and a distal framework residue is involved in Ag binding. As seen from the crystal structure, most of the contacts between peptide and Ab are through the five residues, Leu3-Asp4-Pro5-Ala6-Phe7, of PS1. The paratope is predominantly hydrophobic with aromatic residues lining the binding pocket, although a salt bridge also contributes to stabilizing the Ag-Ab interaction. The molecular surface area buried upon PS1 binding is 756 Å2 for the peptide and 625 Å2 for the Fab, which is higher than what has been seen to date for Ab-peptide complexes. A comparison between PC283 structure and a homology model of its germline ancestor suggests that paratope optimization for PS1 occurs by improving both charge and shape complementarity

Novel neutrino-floor and dark matter searches with deformed shell model calculations

Event detection rates for WIMP-nucleus interactions are calculated for $^{71}$Ga, $^{73}$Ge, $^{75}$As and $^{127}$I (direct dark matter detectors). The nuclear structure form factors, that are rather independent of the underlying beyond the Standard Model particle physics scenario assumed, are evaluated within the context of the deformed nuclear shell model (DSM) based on Hartree-Fock nuclear states. Along with the previously published DSM results for $^{73}$Ge, the neutrino-floor due to coherent elastic neutrino-nucleus scattering (CE$\nu$NS), an important source of background to dark matter searches, is extensively calculated. The impact of new contributions to CE$\nu$NS due to neutrino magnetic moments and $Z^\prime$ mediators at direct dark matter detection experiments is also examined and discussed. The results show that the neutrino-floor constitutes a crucial source of background events for multi-ton scale detectors with sub-keV capabilities.Comment: 16 pages, 12 figures, 3 Tables; 1 figure and 1 table added; references added; matches published versio