The electromagnetic form factors of the neutron in the time-like region have been measured for the first time, from the threshold up to q 2 ⋟ 6 GeV 2 . The neutron magnetic form factor turns out to be larger than the proton one; the angular distribution suggests that for the neutron, at variance with the proton case, electric and magnetic form factors could be different. Further measurements are also reported, concerning the proton form factors and the Σ Σ production, together with the multihadronic cross section and the J / Γ branching ratio into n n .
The uncertainty on the evaluated cross section is given by the quadratic combination of the following terms: the statistical uncertainty on the number of events, the statistical and systematic uncertainty on the luminosity (about 6PCT), the systematic uncertainty on the efficiency evaluation, dominated by the scanning efficiency contribution (about 15PCT). The SQRT(S) values with (C=NOMIN) and (C=SHIFT) correspond to the nominal energy and shifted energy analysis (see text of paper for details).
The uncertainty on the evaluated cross section is given by the quadratic combination of the following terms: the statistical uncertainty on the number of events, the statistical and systematic uncertainty on the luminosity (about 6PCT), the systematic uncertainty on the efficiency evaluation, dominated by the scanning efficiency contribution (about 15PCT). The NEUTRON formfactor value are calculated in two hypotheses: GE = GM and GE = 0.
The uncertainty on the evaluated cross section is given by the quadratic combination of the statistical and systematic uncertainties.
The cross section for the process e + e − → p p has been measured in the s range 3.6–5.9 GeV 2 by the FENICE experiment at the e + e − Adone storage ring and the proton electromagnetic form factor has been extracted.
Cross section measurement.
Proton form-factor measurement.
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No description provided.
An optical spark-chamber counter experiment at Adone, the Italian colliding electron-positron ring, has succeeded in measuring the cross-section for the process e+e−→p\(\bar p\) near threshold (Ec.m.=2.1 GeV). The result isσ(e+e−→p\(\bar p\))=(0.91±0.22) nb.
ISOTROPIC ANGULAR DISTRIBUTION ASSUMED.
The e + e − → p p cross section has been measured between 1925 and 2180 MeV. About 50 p p events were detected. The total cross section decreases from 1.31 ± 0.4 nb near 1937 MeV to 0.55 ± 0.2 nb near 2135 MeV. The proton form factors | G E | 2 and | G M | 2 , assumed identical, decrease from 0.15 ± 0.05 to 0.043 ± 0.015. They are an order of magnitude higher than predicted by the well-known dipole fit. The energy range has been scanned in steps of about 2 MeV. No significant structure was found in this p p sample.
TOTAL CROSS SECTION ASSUMING ISOTROPIC PRODUCTION. RADIATIVE CORRECTIONS CALCULATED USING PEAKING APPROXIMATION (ABOUT 20 PCT). AUTHORS ALSO QUOTE RESULTS FOR LIMITED (COSMIC RAY FREE) ACCEPTANCE AS A CHECK. FORM FACTOR DERIVED ASSUMING ELECTRIC AND MAGNETIC FORM FACTORS EQUAL IN MAGNITUDE.
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