Non-Standard Time Reversal for Particle Multiplets and the Spin-Flavor Structure of Hadrons

We show that a system of quarks interacting with chiral fields provides a physical representation of a ``non-standard'' time reversal for particle multiplets proposed by Weinberg. As an application, we argue that, if the internal structure of hadrons is described by a chiral lagrangian, the so-called time-reversal-odd quark distribution functions might not be forbidden by time-reversal invariance.Comment: 2 pages, proceedings of "The Spin Structure of the Proton", ECT - Trento, July 2001. Eds. S Bass, A De Roeck and A Deshpand

Synchrotron oscillation damping due to beam-beam collisions

In DA{\Phi}NE, the Frascati e+/e- collider, the crab waist collision scheme has been successfully implemented in 2008 and 2009. During the collision operations for Siddharta experiment, an unusual synchrotron damping effect has been observed. Indeed, with the longitudinal feedback switched off, the positron beam becomes unstable with beam currents in the order of 200-300 mA. The longitudinal instability is damped by bringing the positron beam in collision with a high current electron beam (~2A). Besides, we have observed a shift of \approx 600Hz in the residual synchrotron sidebands. Precise measurements have been performed by using both a commercial spectrum analyzer and the diagnostics capabilities of the DA{\Phi}NE longitudinal bunch-by-bunch feedback. This damping effect has been observed in DA{\Phi}NE for the first time during collisions with the crab waist scheme. Our explanation is that beam collisions with a large crossing angle produce a longitudinal tune shift and a longitudinal tune spread, providing Landau damping of synchrotron oscillations.Comment: 3 pages, 5 figures, talk presented to IPAC'10 - Kyoto - May 24-28 201

Dynamics of Phase Transitions in Asymmetric Nuclear Matter

We present several possibilities offered by the reaction dynamics of dissipative heavy ion collisions to study in detail the symmetry term of the nuclear equation of state, $EOS$. In particular we discuss isospin effects on the nuclear liquid-gas phase transition, {\it Isospin Distillation}, and on collective flows. We stress the importance of a microscopic relativistic structure of the effective interaction in the isovector channel. The possibility of an {\it early} transition to deconfined matter in high isospin density regions is also suggested. We finally select {\it Eleven} observables, in different beam energy regions, that appear rather sensitive to the isovector part of the nuclear $EOS$, in particular in more exclusive experiments.Comment: 8 pages, 7 figures, ISPUN02 Conference, Halong-Vietnam, Nov.20-25 2002, to appear in Nucl.Phys.A. Elsevier Proceedings Styl

Prospects for intermediate mass black hole binary searches with advanced gravitational-wave detectors

We estimated the sensitivity of the upcoming advanced, ground-based gravitational-wave observatories (the upgraded LIGO and Virgo and the KAGRA interferometers) to coalescing intermediate mass black hole binaries (IMBHB). We added waveforms modeling the gravitational radiation emitted by IMBHBs to detectors' simulated data and searched for the injected signals with the coherent WaveBurst algorithm. The tested binary's parameter space covers non-spinning IMBHBs with source-frame total masses between 50 and 1050 $\text{M}_{\odot}$ and mass ratios between $1/6$ and 1$\,$. We found that advanced detectors could be sensitive to these systems up to a range of a few Gpc. A theoretical model was adopted to estimate the expected observation rates, yielding up to a few tens of events per year. Thus, our results indicate that advanced detectors will have a reasonable chance to collect the first direct evidence for intermediate mass black holes and open a new, intriguing channel for probing the Universe over cosmological scales.Comment: 9 pages, 4 figures, corrected the name of one author (previously misspelled

Testing Deconfinement at High Isospin Density

We study the transition from hadronic matter to a mixed phase of quarks and hadrons at high baryon and isospin densities reached in heavy ion collisions. We focus our attention on the role played by the nucleon symmetry energy at high density.In this respect the inclusion of a scalar isovector meson, the \delta-coupling, in the Hadron Lagrangian appears rather important. We study in detail the formation of a drop of quark matter in the mixed phase, and we discuss the effects on the quark drop nucleation probability of the finite size and finite time duration of the high density region. We find that, if the parameters of quark models are fixed so that the existence of quark stars is allowed, then the density at which a mixed phase starts forming drops dramatically in the range Z/A \sim 0.3--0.4. This opens the possibility to verify the Witten-Bodmer hypothesis on absolute stability of quark matter using ground-based experiments in which neutron-rich nuclei are employed. These experiments can also provide rather stringent constraints on the Equation of State (EoS) to be used for describing the pre-Supernova gravitational collapse. Consistent simulations of neutron rich heavy ion collisions are performed in order to show that even at relatively low energies, in the few AGeV range, the system can enter such unstable mixed phase. Some precursor observables are suggested, in particular a ``neutron trapping'' effect.Comment: 32 pages, 14 figures, elsart late

Quiescent times in Gamma-Ray-Bursts: hints of a dormant inner engine

We perform a statistical analysis of the temporal structure of long Gamma-Ray-Bursts (GRBs). First we consider a sample of bursts in which a long quiescent time is present. Comparing the pre-quiescence with the post-quiescence emission we show that they display similar temporal structures, hardness ratios and emitted powers, but, on the average, the post-quiescence emission is roughly twice as long as the pre-quiescence emission. We then consider a sample of long and bright GRBs. We show that the duration of each emission period is compatible with the duration of an active period computed in various inner engine models. At the contrary, if the inner engine is assumed to be always active, i.e. also during the quiescent times, in several cases the total duration of the burst largely exceeds the theoretical durations. Our analysis therefore does not support the interpretation of long quiescent times in terms of stochastic modulation of a continuous wind. Instead the quiescent times can be interpreted as dormancy periods of the inner engine. Before and after a dormancy period the inner engine produces similar emissions.Comment: 17 pages, 7 figures. New version after referee's comments. Two figures adde

Enhancing the significance of gravitational wave bursts through signal classification

The quest to observe gravitational waves challenges our ability to discriminate signals from detector noise. This issue is especially relevant for transient gravitational waves searches with a robust eyes wide open approach, the so called all- sky burst searches. Here we show how signal classification methods inspired by broad astrophysical characteristics can be implemented in all-sky burst searches preserving their generality. In our case study, we apply a multivariate analyses based on artificial neural networks to classify waves emitted in compact binary coalescences. We enhance by orders of magnitude the significance of signals belonging to this broad astrophysical class against the noise background. Alternatively, at a given level of mis-classification of noise events, we can detect about 1/4 more of the total signal population. We also show that a more general strategy of signal classification can actually be performed, by testing the ability of artificial neural networks in discriminating different signal classes. The possible impact on future observations by the LIGO-Virgo network of detectors is discussed by analysing recoloured noise from previous LIGO-Virgo data with coherent WaveBurst, one of the flagship pipelines dedicated to all-sky searches for transient gravitational waves