Aqueye+: a new ultrafast single photon counter for optical high time resolution astrophysics

Aqueye+ is a new ultrafast optical single photon counter, based on single photon avalanche photodiodes (SPAD) and a 4-fold split-pupil concept. It is a completely revisited version of its predecessor, Aqueye, successfully mounted at the 182 cm Copernicus telescope in Asiago. Here we will present the new technological features implemented on Aqueye+, namely a state of the art timing system, a dedicated and optimized optical train, a high sensitivity and high frame rate field camera and remote control, which will give Aqueye plus much superior performances with respect to its predecessor, unparalleled by any other existing fast photometer. The instrument will host also an optical vorticity module to achieve high performance astronomical coronography and a real time acquisition of atmospheric seeing unit. The present paper describes the instrument and its first performances.Comment: Proceedings of the SPIE, Volume 9504, id. 95040C 14 pp. (2015

Cancellation of Infrared Divergences in Hadronic Annihilation Decays of Heavy Quarkonia

In the framework of a newly developed factorization formalism which is based on NRQCD, explicit cancellations are shown for the infrared divergences that appeared in the previously calculated hadronic annihilation decay rates of P-wave and D-wave heavy quarkonia. We extend them to a more general case that to leading order in $v^2$ and next-to-leading order in $\alpha_s$, the infrared divergences in the annihilation amplitudes of color-singlet $Q\bar{Q}(^{2S+1}L_J)$ pair can be removed by including the contributions of color-octet operators $Q\bar{Q}(^{2S+1}(L-1)_{J'})$, $Q\bar{Q}(^{2S+1}(L-3)_{J''})$, ... in NRQCD. We also give the decay widths of $^3D_J\rightarrow LH$ at leading order in $\alpha_s$.Comment: 8 pages, LaTex(3 figures included), to be publishe

Rigorous QCD Predictions for Decays of P-Wave Quarkonia

Rigorous QCD predictions for decay rates of the P-wave states of heavy quarkonia are presented. They are based on a new factorization theorem which is valid to leading order in the heavy quark velocity and to all orders in the running coupling constant of QCD. The decay rates for all four P states into light hadronic or electromagnetic final states are expressed in terms of two phenomenological parameters, whose coefficients are perturbatively calculable. Logarithms of the binding energy encountered in previous perturbative calculations of P-wave decays are factored into a phenomenological parameter that is related to the probability for the heavy quark-antiquark pair to be in a color-octet S-wave state. Applying these predictions to charmonium, we use measured decay rates for the \chione and \chitwo to predict the decay rates of the \chizero and $h_c$.Comment: 13 page

Less Minimal Flavour Violation

We consider the approximate U(2)^3 flavour symmetry exhibited by the quark sector of the Standard Model and all its possible breaking terms appearing in the quark Yukawa couplings. Taking an Effective Field Theory point of view, we determine the current bounds on these parameters, assumed to control the breaking of flavour in a generic extension of the Standard Model at a reference scale Lambda. In particular, a significant bound from epsilon'/epsilon is derived, which is relevant to Minimal Flavour Violation as well. In the up-quark sector, the recently observed CP violation in D -> pi+ pi-, K+ K- decays might be accounted for in this generic framework, consistently with any other constraint.Comment: 15 pages, 1 figur

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

Photoproduction of h_c

Using the NRQCD factorization formalism, we calculate the total cross section for the photoproduction of h_c mesons. We include color-octet and color-singlet mechanisms as well as next-to-leading order perturbative QCD corrections. The theoretical prediction depends on two nonperturbative matrix elements that are not well determined from existing data on charmonium production. For reasonable values of these matrix elements, the cross section is large enough that the h_c may be observable at the E831 experiment and at the HERA experiments.Comment: Revtex file 8 pages, 1 figure. Macros needed: epsf,floats,rotate Minor typos changed, and reference added. Version to be published in Phys.Rev.

QCD Corrections in two-Higgs-doublet extensions of the Standard Model with Minimal Flavor Violation

We present the QCD corrections to R_b and to the Delta B=1 effective Hamiltonian in models with a second Higgs field that couples to the quarks respecting the criterion of Minimal Flavor Violation, thus belonging either to the (1,2)_1/2 or to the (8,2)_1/2 representation of SU(3)xSU(2)xU(1). After the inclusion of the QCD corrections, the prediction for R_b becomes practically insensitive to the choice of renormalization scheme for the top mass, which for the type-I and type-II models translates in a more robust lower bound on tan(beta). The QCD-corrected determinations of Rb and BR(B->Xs gamma) are used to discuss the constraints on the couplings of a (colored) charged Higgs boson to top and bottom quarks.Comment: 19 pages, 7 figures. v2: version published in Phys. Rev. D, with additional reference and not