M. Spinetti

TOTAL CROSS-SECTION FOR HADRONIC PRODUCTION BY E+E- ANNIHILATION IN THE TOTAL CM ENERGY-RANGE 1.42-3.09 GEV

Abstract We report experimental results on the cross section for the reaction e + e − → hadrons as a function of the total c.m. energy in the range W = 1.42–3.09 GeV. The results, combined with those already existing below the charm threshold, clearly indicate a structure for R ( W ) = α ( e + e − → hadrons)/ α ( e + e − → μ + μ − ) in that energy region.

The transverse-momentum distributions of particles produced in pp reactions and comparison with e+ e−

SummaryFollowing our previous work, the comparison of the properties of multihadron systems, produced in high-energy pp reactions, with hadron jets produced in e+ e− annihilation, is further extended through the study of the inclusive distributions in the «reduced» variablepT/.A good agreement with e+ e− data is found.

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.

The «leading»-particle effect in hadron physics

SummaryA world review is presented of the «leading»-particle effect in hadron physics: baryon-baryon, baryon-antibaryon, mesonbaryon and photon-baryon processes are studied and compared with hadron production from an initial state which does not contain any hadron. In this latter case the «leading» effect is not present. It is shown that the «leading»-particle effect is fully present even in hadron interactions initiated by neutrinos. The importance of the «leading» effect in hadron physics is discussed.RiassuntoSi presenta una rassegna mondiale dell’effetto di particella «leading» in fisica adronica. Processi del tipo barione-barione, barione-antibarione, mesone-barione e fotone-barione sono studiati e confrontati con la produzione di adroni da uno stato iniziale che non contiene adroni. In quest’ultimo tipo di processi non è presente l’effetto «leading». Si dimostra che l’effetto di particella «leading» è sicuramente presente anche nelle interazioni iniziate da neutrini con adroni nello stato finale. Si discute infine l’importanza dell’effetto «leading» nella fisica adronica.РеэюмеПроводится аналиэ зффекта «лидируюшей» частицы в адронной фиэике. Исследуются барион-барионные, барион-антибарионные, меэон-барионные и протон-барионные процессы. Проводится сравнение с процессом обраэования адрона иэ начального состояния, которое не содержит адрона. В зтом последнем случае зффект «лидируюшей» частицы отсутствует. Покаэывается, что зффект «лидируюшей» частицы имеет место в адронных вэаимодействиях, инициированных нейтрино. Обсуждается важность зффекта «лидируюшей» частицы в адронной фиэике.

The ratio of charged-to-total energy in high-energy proton-proton interactions

Abstract The ratio of charged-to-total energy in multiparticle hadronic systems produced in pp interactions has been measured. The analysis has been performed using our technique of subtracting the “leading” baryon effects. The results are compared with e + e − annihilation data.

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 hadronic exclusive cross sections in e+e− annihilation from 1.42 to 2.20 GeV

Abstract Total cross sections for reactions e+e−→π+π−π0, π+π−π0, 2π+2π−π0, 2π+2π−2π0, 3π+3π− have been measured in the total c.m. energy range 1.42–2.20 GeV. Partial R=σhad/σσ+μ− values for two and four produced charged pions, and cross sections for positive and negative G-parity states are also reported.

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 inclusive transverse-momentum distribution in hadronic systems produced in proton-proton collisions

Summary. The single.particle inclusive transverse-momentum distribution in the multiparticle systems produced in low-1~T proton-proton interactions at ~- 30 and 62 GoV has been studied. The analysis was performed removing from the final state the leading proton and redefining the effective hadronie energy available for particle production. Excellent agreement for effective hadronic energies up to 13 GoV is found between (pp) and (e+e-). At higher energy the (pp) data show a less pronounced growth than the (e+e -) data.

Measurement of branching ratios and estimate of the phase of the strong decay amplitude

Abstract The results of new measurements of J/ψ→n n and J/ψ→p p performed by the FENICE experiment are reported. The relative phase φ, between the strong and the electromagnetic decay amplitudes, is achieved from the branching ratios J/ψ→N N and from the nucleon form factors measurements near the J/ψ. It turns out φ=89o±15o, in agreement with other J/ψ decay amplitudes.