A. Zallo

Unexpected features of e+e- \rightarrow p \overline{{p}} and e+e- \rightarrow \Lambda \overline{{\Lambda}} cross-sections near threshold

Unexpected features of the BaBar data on e+e- in baryon-antibaryon cross sections are discussed. These data have been collected, with unprecedented accuracy, by means of the initial state radiation technique, which is particularly suitable in giving good acceptance and energy resolution at threshold. A striking feature observed in the BaBar data is the non-vanishing cross section at threshold for all these processes. This is the expectation due to the Coulomb enhancement factor acting on a charged fermion pair. In the case of e+e- in proton-antiproton it is found that Coulomb final state interactions largely dominate the cross section and the form factor is |G^p(4M^2_p)|~1, which could be a general feature for baryons. In the case of neutral baryons an interpretation of the non-vanishing cross section at threshold is suggested, based on quark electromagnetic interaction and taking into account the asymmetry between attractive and repulsive Coulomb factors. Besides strange baryon cross sections are compared to U-spin invariance predictions.

The photomultiplier gain monitoring system for the E687 electromagnetic calorimeter at Fermilab

Abstract The nitrogen pulsed laser monitoring system for the outer electromagnetic calorimeter of the E687 photoproduction experiment, investigating charm and beauty states at the Fermilab Tevatron, is described. The system is reliable, economical and allows a photomultipliers gain stability control as good as 1%.

A study of the short-term rate effect in Philips XP-2008 photomultiplier tubes

Abstract A detailed study of the rate effect under experimental conditions typical of accelerators is presented. Gain variations for Philips XP2008 (now available as XP2071B) photomultiplier tubes and their time dependences have been studied as functions of pulse amplitude and frequency, and the tubes high voltage supply.

The BaBar detector for muon identification and neutral hadron detection

Abstract The BaBar experiment is projected to study CP violation in B decays. Muon detection and KL0 identification are achieved by an Instrumented Flux Return (IFR) system based on resistive plate chamber detectors. In this paper the general layout of the IFR system will be described.

Single and multiple muon events in the LVD detector

Abstract Expected rates of deep-underground muons in the LVD detector, at a vertical depth of 3600 hg/cm 2 s.r. (standard rock) at the Gran Sasso, were obtained through Monte Carlo simulation. Two different generators were developed to reproduce single and multiple muon distributions at our detector level. The main purpose was to evaluate the potentiality of the apparatus in studying chemical composition and energy spectra of primary cosmic rays in the range 10 14 –10 16 eV through the detection of muon bundles of high multiplicity. Sensitivity of the detector was checked by comparing event-rate predictions for three different models of the primary composition: the Maryland spectrum, the “low energy composition” model, and the NUSEX parametrization (with spectral index of iron γ Fe = 2.60 and 2.70). We predict a single muon rate in the apparatus of about 3.26×10 6 events/year. Preliminary results for multiple muon-event detection show that we can separate with a good sensitivity different primary compositions in the multiplicity region around n = 10.

A multitarget solid state device studying relativistic heavy ion fragments

Abstract A multilayer solid state device which is both an active target and tracking detector is proposed for an electronic experiment investigating the so-called anomalons and studying their production mechanism, interaction cross-section and lifetime. The experimental method is based on triggering the reinteractions in two targets of heavy fragments, originated in a production target by a relativistic ion beam. This method greatly increases the sensitivity to the anomalons effect when compared to other proposed electronic experiments. Solid state devices seem to provide a resolving technique for the study of these short-lived states among high-multiplicity final systems.