C. Voci

Measurement of the electromagnetic form factor of the proton in the time-like region

Abstract The cross section for the process e + e − → p p has been measured in the s range 3.6–5.9 GeV2 by the FENICE experiment at the e+e− Adone storage ring and the proton electromagnetic form factor has been extracted.

First measurement of the neutron electromagnetic form factor in the time-like region

Abstract The first measurement of the neutron form factor in the time-like region has been performed by the FENICE experiment at the ADONE e + e − storage ring. Results at q 2 = 4.0 and 4.4 (GeV/ c ) 2 , together with a new measurement of the proton form factor are presented here.

Measurement of the total e+e− → hadrons cross section near the e+e− →NN threshold

Abstract A new measurement of the total e + e − → hadrons cross-section in the centre of mass energy range 1.8-2.5 GeV, performed by the FENICE experiment at the Frascati e + e − storage ring ADONE, is presented. The behaviour of the total cross section together with the proton electromagnetic time-like form factor is discussed in terms of a narrow vector resonance close to the nucleon-antinucleon threshold.

Measurement of the Annihilation Cross-Section for Antineutrons on Fe from 100 to 531 MeV/c

The cross-section for annihilation on Fe from 100 to 531 MeV/c was measured by means of a layered absorption detector. The cross-sections are related to the free N annihilation cross-sections by a simple A2/3 scaling law, indicating a surface process.

An experimental study of antineutron detection

Abstract The main features of a new type of antineutron detector are described. It consists of modules of scintillators, limited streamer tube planes and iron converters. The energy of the antineutrons is measured by time of flight with a resolution of 800 ps FWHM. The vertex of annihilation is reconstructed with a precision of 8 cm FWHM. The trigger conditions can be selected following the chosen topology of the events.

A Study of the bar n Production on Nuclei by bar p of 550 MeV/c

Inclusive spectra produced at 0° by the interaction of 550 MeV/c s on C, Al, Cu and Pb targets were measured. The results are discussed in the framework of simple models on incoherent particle production by complex nuclei.

A new measurement of Jψ→nn

A new measurement of the branching ratio of J/ψ → nn, B nn = (1.90 ± 0.55) × 10 −3 , has been achieved by the FENICE detector at the e + e − storage ring ADONE in FrascatiA new measurement of the branching ratio of J/psi-->nnBAR, B(nnBAR) = (1.90 +/- 0.55) X 10(-3), has been achieved by the FENICE detector at the e+e- storage ring ADONE in Frascati.

A Low Energy Antineutron Detector

A detector for antineutrons in the momentum range 0.1 - 1 Gev/c, to be used at LEAR faci= lity at CERN, is described. The antineutrons are detected by means of the charged pions produced in an annihilation event and their energy is determined by a time of flight mea= surement. The detector consist of 10 equal modules; each one contains: an iron slab (the converter) of 20×20×1 cm , a scintillation of the same dimensions for T.O.F. measurements, an iron sheet of 100×100×0.2 cm that stops the low energy high ionizing particles and finally a plane of limited streamer tubes with 1 cm pitch and read-out on both horizontal and vertical cohordinates. Principal features of the detector are: T.O.F. resolution of 0.5 ns, spatial resolution of 1 cm in both vertical and horizontal directions, estimated efficien= cy of 0.65.

A Large Area, Fine Grained Neutron Hodoscope

Results of measurements of the performances of a time-of-flight neutron hodoscope consisting of 50 slabs of plastic scintillator, 100 × 2 × 5 cm3 each, are described. The efficiency and the spatial localization properties along a slab were studied with a variable energy (2.4 to 16.4 MeV) neutron beam. The hodoscope was finally used in the experiment PS 178 at the LEAR facility at CERN.

Perspectives of Antineutron Physics

Experimental data in (bar n) interactions are up to now rather scarce, mainly due to the lack of suitable beams. With the recent improvements of (bar p) beams and with the advent of the LEAR facility at CERN, it is now the time of thinking of new experiments in order to study the properties and the interactions of an elementary particle like the (bar n). In the following we will discuss briefly how we can obtain (bar n) beams, how we can detect these particles and finally some significant experiments that can be performed.