M.G. Sapozhnikov

Abundant φ-meson production in pp annihilation at rest and strangeness in the nucleon

Abstract A large apparent violation of the OZI rule has recently been found in many channels in p p annihilation at LEAR. An interpretation of these data in terms of the “shake-out” and “rearrangement” of an intrinsic s s component of the nucleon wave function is proposed. This gives a channel-dependent, non-universal modification of the naive OZI prediction. Within this approach, we interpret the strong excess of φ production in S-wave p p annihilations in terms of the polarization of the nucleons s s component indicated by deep inelastic lepton-nucleon scattering experiments. This interpretation could be tested by measurements of s s meson production ratios in p p annihilation at rest and by experiments with polarized beams and polarized targets. We also propose a test of the intrinsic strangeness hypothesis in φ production in high-momentum transfer processes, via a difference in constituent counting rules from gluon-mediated production.

Low-energy Antiproton Neon Interaction

Abstract By means of a streamer chamber exposed to the LEAR antiproton beams, the total reaction cross sections, the charged-prong multiplicity distributions and lower limits for the production of negative pions and K s 0 in the p-Ne interaction were measured at 19.6, 48.7 and 179.6 MeV. Annihilation was found to be dominant over all other non-elastic p-Ne processes. An analysis of Ne and other nuclei data in the frame of the Glauber theory allowed us to determine the ratio between the p-n and the p-p cross sections. An analysis in the light of INC model predictions allowed us to show up events which can be interpreted as annihilations having occurred deeply inside the nuclei.

Inelastic interaction of antiprotons with 4He nuclei between 200 and 600 MeV/c

The antiproton-helium reaction cross section has been measured at 19.6 and 48.7 MeV with a streamer chamber in a magnetic field. Charged prongs and negative pion multiplicities and cross sections for the production of 3He are given. A comparison with p 2H is performed. he previously obtained 179.6 MeV results are also taken into account.

p4He reaction cross section at 610 MeV/c

Abstract Antiproton helium reaction cross section has been measured at 179.6 MeV with a self shunted streamer chamber in a magnetic field. Charged prong multiplicity, branching ratios and 3He production probability are given. Comparison with p 2 H data is performed.

φ and ω meson production in n¯p annihilation and the OZI rule

Abstract The φπ + /ωπ + ratio from n ¯ p annihilations on a liquid hydrogen target, for n ¯ momenta between 64 and 297 MeV/ c , was measured using the OBELIX spectrometer at LEAR. The ratio R ( ϕ π / ω π ) = σ ( n ¯ p → ϕ π + ) / σ ( n ¯ p → ω π + ) turned out 0.110±0.015 stat ±0.006 syst . Implications of this result on the OZI rule are discussed.

Antiproton-helium annihilation around 45 MeV/c

Abstract The p ¯ 4 He annihilation cross section averaged over the interval 40–50 MeV/c has been measured using a streamer chamber in a magnetic field. The measured value is 1342±250 mb. It agrees with a behaviour like 1/p of the annihilation cross section. Our result has been obtained at the lowest momentum achieved till now in measurements of antiproton annihilation in flight.

Pontecorvo reactions of two-body antiproton annihilation in deuterium

Abstract Rare annihilation reactions for stopped antiprotons in deuterium p d →π − p, K + Σ − , K 0 Λ model described by the triangle diagram. It was found that the probabilities W of these processes are very sensitive to the behaviour of the deuteron wave function at small distances as well as to the meson form factors. It appears that the ratios R (KX) = W (KX) W(π − p ) are much less model-dependent and are about 10−2 for R(K0Λ) and 10−4 for R(K+Σ−.

Astrophysical aspects of antiproton interaction with 4He (antimatter in the universe)

Abstract We show that the experimental information on p 4 He annihilation may impose limits on the possible amount of anti-matter in the early universe and other important cosmological topics, predicted by some variants of GUT cosmology.

Hadronic probes of the polarized intrinsic strangeness of the nucleon

Abstract We have previously interpreted the various large apparent violations of the naive Okubo–Zweig–Iizuka (OZI) rule found in many channels in p p annihilation at LEAR as evidence for an intrinsic polarized s s component of the nucleon wave function. The model is further supported by new data from LEAR and elsewhere. Here we discuss in more detail the possible form of the s s component of the nucleon wave function, interpret the new data and clarify the relative roles of strangeness shake-out and rearrangement, discuss whether alternative interpretations are still allowed by the new data, and propose more tests of the model.

Elastic scattering of π±-Mesons on3He in the energy interval (68÷208) MeV

SummaryDifferent cross-section measurements of elastic scattering of π± on3He are presented. The study was done both for positive and negative pions at 98, 120, 135, 145, 156 MeV, for negative pions also at 198 and 208 MeV and for positive pions also at 68MeV. The experiment was carried out with a high-pressure helium self-shunted streamer chamber surrounded by a hodoscope of scintillation counters. The results are compared with optical-model calculations using spin-and isospin-dependent potentials. The energy dependence of the total elastic (π±,3He) scattering cross-section is discussed. Estimates of the (π3He3H) coupling constant according to the theory of Chew and Low are presented.RiassuntoSono presenti i risultati della misura della sezione d’urto differenziale di diffusione elastica (π+,3He) a 68, 98, 120, 135, 145, 156 MeV e (π−,3He) as 98, 120, 135, 145, 156, 198, 208 MeV. I dati sperimentali sono confrontati con le previsioni del modello ottico ed inoltre viene fatta una stima della costante di accoppiamento (π3He3H).РеэюмеИэмерены дифференциальные сечения упругого рассеяния пионов на ядрах3He при знергиях 68, 98, 120,135, 145, 156, 198, 208 MзB. Эксперименты вы-полнены на гелиевой стримерной камере высокого давления. Данные сопоста-вляются с расчетами по оптииеской модели. Даются оценки констаяты свяэиf2(π3He3H).