G. Cara Romeo

Evidence of the same multiparticle production mechanism in p−p collisions as in e+e− annihilation

Abstract The split-field magnet spectrometer at the CERN intersecting storage rings was used to measure, in p−p collisions at s 62 GeV , the inclusive momentum distribution of the charged particles produced in the same hemisphere as the leading proton ( x >0.4). A new scaling variable was introduced in order to take into account baryon-number conservation effects in p−p interactions. It is shown that distributions in this variable are in good agreement with the momentum distribution of the hadrons produced in e + e − annihilation. The results suggest that the multiparticle production mechanism in p−p collisions is the same as in e + e − provided that the effects of baryon-number conservation are removed.

Evidence for a new particle with naked «beauty» and for its associated production in high-energy (pp) interactions

SummaryEvidence is reported for the existence, with six-standard-deviation significance, of a new particle: the heaviest baryon observed so far, whose mass is measured to bem=(5425−75+175) MeV/c2. Its width is compatible with zero. It is electrically neutral and it decays into a proton, a Do and a π–. This particle is produced in association with a hadronic state whose semi-leptonic decay contains a positive electron. The partial cross-section for the observed effect is Δσ=(3.8±1.2)·10−35 cm2. The interpretation of these results is in terms of the associated production of naked-«beauty» states in (pp) interactions at

The ZEUS vertex detector: Design and prototype test

\sqrt 8 = 62 GeV c.m.

The «leading»-particle effect in hadron physics

GeV c.m. energy. The new particle is identified as the first «beauty»-flavoured baryon with quark composition (udb),i.e. the Λb0. The discrimination power of the experiment against «known» physics is of the order of 10−10.

Measurements of in and out distributions in high-energy pp interactions

Abstract The average charged multiplicity in proton-proton interactions has been studied at √ s = 62 GeV. A very good agreement with the average charged multiplicity measured in e + e − annihilation at different energies is obtained by redefining, in p-p, the correct energies available for particle production. This means that a p-p collision at √ s = 62 GeV does in fact correspond to a large range of effective hadronic energies available for particle production.

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

Abstract A gas vertex detector, operated with dimethylether (DME) at atmospheric pressure, is presently being built for the ZEUS experiment at HERA. Its main design features, together with the performances of a prototype measured at various operating voltages, particle rates and geometrical conditions on a CERN Proton Synchrotron test beam, are presented. A spatial resolution down to 35 μm and an average wire efficiency of 96% have been achieved, for a 3 mm gas gap relative to each sense wire.

The fractional momentum distribution in p-p collisions compared with e + e − annihilation

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.

A study of the multigap RPC at the gamma irradiation facility at CERN

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.