Gravitational helicity interaction

For gravitational deflections of massless particles of given helicity from a classical rotating body, we describe the general relativity corrections to the geometric optics approximation. We compute the corresponding scattering cross sections for neutrinos, photons and gravitons to lowest order in the gravitational coupling constant. We find that the helicity coupling to spacetime geometry modifies the ray deflection formula of the geometric optics, so that rays of different helicity are deflected by different amounts. We also discuss the validity range of the Born approximation.Comment: 16 pages, 1 figure, to be published in Nuclear Physics

Mutual cosideration of b→sγb\to s\gamma and μ→eγ\mu\to e\gamma in supersymmetric SO(10) grand unification

We compare the branching ratios for $b\rightarrow s\gamma$ and $\mu\rightarrow e\gamma$ in terms of constraining the parameter space in supersymmetric SO(10) grand unification models where supersymmetry is broken softly near the Planck scale by generationally symmetric operators. We observe two general cases. One with small $\tan\beta =2$ and the other one with large $\tan\beta$ having third generation Yukawa coupling unification at the GUT scale. \newline\indent We show that for small $\tan\beta$ the branching ratio constraints allow only a smaller region of parameter space for $\mu>0$ compared to $\mu<0$ for gluino mass \alt 500 GeV. With large $\tan\beta$, we find acceptable regions of parameter space with \left|\mu \right|\alt 1 TeV only for $\mu<0$. The dominant constraint on large $\tan\beta$ with $\mu >0$ parameter space is found to be given by the $b\rightarrow s\gamma$ branching ratio, while for large $\tan\beta$ with $\mu <0$ it is found to be given by the $\mu\rightarrow e\gamma$ branching ratio. In many of these acceptable regions, we find that the $\mu\rightarrow e\gamma$ branching ratio is predicted to be within one order of magnitude of its current experimental bound. We also show that the usually neglected gluino mediated diagrams in $b\rightarrow s\gamma$ can not be ignored in some regions of parameter space, especially for large $\tan\beta$ scenarios when the gluino mass is near its lower experimental bound.Comment: 14 pages (Latex), 4 PS figs (uuencoded, epsf.tex), slight modification in text, as to appear in Physics Letters

Role of Long-Range Correlations on the Quenching of Spectroscopic Factors

We consider the proton and neutron quasiparticle orbits around the closed-shell 56Ni and 48Ca isotopes. It is found that large model spaces (beyond the capability of shell-model applications) are necessary for predicting the quenchings of spectroscopic factors. The particle-vibration coupling is identified as the principal mechanism. Additional correlations--due to configuration with several particle-hole excitations--are estimated using shell-model calculations and generate an extra reduction which is < ~4% for most quasiparticle states. The theoretical calculations nicely agree with (e,e'p) and heavy ion knock-out experiments. These results open a new path for a microscopic understanding of the shell-model.Comment: Minor comments added and typos corrected. Accepted for publication on Phys. Rev. Let

Effects of an intermediate scale in SUSY grand unification

We discuss the production of lepton flavor violation and EDMs and the viability of the $b-\tau$ unification hypothesis in SUSY grand unification with an intermediate gauge symmetry breaking scale.Comment: 3 pages (Latex, esprc2.sty used), talk given at 4th International Conference on Supersymmetry (SUSY '96, College Park, MD, May 29 - June 1, 1996

Optical phase coherent timing of the Crab nebula pulsar with Iqueye at the ESO New Technology Telescope

The Crab nebula pulsar was observed in 2009 January and December with a novel very fast optical photon counter, Iqueye, mounted at the ESO 3.5 m New Technology Telescope. Thanks to the exquisite quality of the Iqueye data, we computed accurate phase coherent timing solutions for the two observing runs and over the entire year 2009. Our statistical uncertainty on the determination of the phase of the main pulse and the rotational period of the pulsar for short (a few days) time intervals are $\approx 1 \, \mu$s and ~0.5 ps, respectively. Comparison with the Jodrell Bank radio ephemerides shows that the optical pulse leads the radio one by ~240 $\mu$s in January and ~160 $\mu$s in December, in agreement with a number of other measurements performed after 1996. A third-order polynomial fit adequately describes the spin-down for the 2009 January plus December optical observations. The phase noise is consistent with being Gaussian distributed with a dispersion $\sigma$ of $\approx 15 \, \mu$s in most observations, in agreement with theoretical expectations for photon noise-induced phase variability.Comment: 10 pages, 5 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Neutrino masses and flavor symmetries

The problem of neutrino masses and mixing angles is analysed in a class of supersymmetric grand unified models, with SO(10) gauge symmetry and global U(2) flavour symmetry. Adopting the seesaw mechanism for the generation of the neutrino masses, one obtains a mass matrix for the left-handed neutrinos which is directly related to the parameters of the charged sector, while the unknown parameters of the right-handed Majorana mass matrix are inglobed in a single factor.Comment: 17 pages, 1 eps figure, uses graphicx.sty, LaTeX 2e, to be published on "Il Nuovo Cimento

QCD Radiative Corrections to the Leptonic Decay Rate of the B_c Meson

The QCD radiative corrections to the leptonic decay rate of the $B_c$ meson are calculated using the formalism of nonrelativistic QCD (NRQCD) to separate short-distance and long-distance effects. The $B_c$ decay constant is factored into a sum of NRQCD matrix elements each multiplied by a short-distance coefficient. The short-distance coefficient for the leading matrix element is calculated to order $\alpha_s$ by matching a perturbative calculation in full QCD with the corresponding perturbative calculation in NRQCD. This short-distance correction decreases the leptonic decay rate by approximately $15\%$.Comment: Changed Eq. 2 to read 1/(8 \pi), put in a missing i M_{B_c} in Eq. 18, and put in a normalisation factor of 2 M_{B_c} in Eq. 19

The History of the Mysterious Eclipses of KH 15D: Asiago Observatory, 1967-1982

We are gathering archival observations to determine the photometric history of the unique and unexplained eclipses of the pre-main-sequence star KH 15D. Here we present a light curve from 1967-1982, based on photographic plates from Asiago Observatory. During this time, the system alternated periodically between bright and faint states, as observed today. However, the bright state was 0.9 mag brighter than the modern value, and the fractional variation between bright and faint states (Delta I = 0.7 mag) was smaller than observed today (3.5 mag). A possible explanation for these findings is that the system contains a second star that was previously blended with the eclipsing star, but is now completely obscured.Comment: Accepted to AJ. 24 pages, 10 figures, 2 tables. v2: Phase error corrected in figures 8 and 1

Supersymmetry phenomenology beyond the MSSM after 5/fb of LHC data

We briefly review the status of motivated beyond-the-MSSM phenomenology in the light of the LHC searches to date. In particular, we discuss the conceptual consequences of the exclusion bounds, of the hint for a Higgs boson at about 125 GeV, and of interpreting the excess of direct CP violation in the charm sector as a signal of New Physics. We try to go into the various topics in a compact way while providing a relatively rich list of references, with particular attention to the most recent developments.Comment: 20 pages + refs. v2: minor modifications, published versio