L. Cugusi

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.

The FENICE detector at the e+e− collider ADONE

The FENICE detector, installed at the Frascati e+ e− storage ring ADONE, for measuring the neutron e.m. form factors in the timelike region, is described. FENICE is a nonmagnetic detector and consists of a complex array of scintillators, limited streamer tubes and iron converters for detecting mainly the process e+ e− → nn. Antineutrons are identified by the charged prongs produced in their annihilation and the antineutron velocity is measured by the retrieved annihilation time with respect to the beam crossing time. Neutrons are detected in plastic scintillator layers. To reduce the cosmic rays background a concrete shield, covered by an active veto system, is added.

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.

Measurement of the Cross-section For E(+)e(-)-]hadrons Near the Nucleon-antinucleon Threshold By the Fenice Experiment

SummaryFENICE preliminary results on the measurement of the total cross-section for e+e− → hadrons and of the e+e− → 6π cross-section, in the centre-of-mass energy range 1.8–2.5 GeV, are reported.

A New Measurement of J-psi-]n(n)over-bar

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 New measurement of j / psi ---> n anti-n.

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.

The FENICE detector at ADONE

A detector to measure the neutron e.m. form factors in the time-like region, through the e/sup +/e/sup -/ to nn reaction, is described. The FENICE experiment, at the Frascati e/sup +/e/sup -/ storage ring ADONE, has been conceived in such a way as to maximize the detection efficiency for this measurement in the c.m. energy interval from the threshold up to the J/ Psi . The apparatus is a complex array of scintillators, limited streamer tubes, and iron convertors. To reduce the cosmic-ray background a concrete shield has been built around the detector and the shield is covered by an active veto system. Antineutrons are detected by means of the charged prongs produced in annihilation events, and their energy is measured by a time-of-flight technique. Neutrons are detected by means of plastic scintillators. There are basically two types of trigger: n trigger and charged trigger. An associative memory helps to recognize the charged tracks coming from the interaction zone. The data acquisition system relies on a mu VAX 3200. A transputer module takes care of data readout and formatting. The online software is based on the Fermilab VAXONLINE system.<<ETX>>