K. Myklebost

Charged current elastic antineutrino interactions in propane

Abstract A sample of 766 antineutrino charged current elastic events has been used to extract the variation of the elastic cross section with antineutrino energy and the distribution of d N /d q 2 . The best fit value for the parameter M A obtained from these measurements is M A = 0.91 ± 0.04 GeV/ c 2 for M V = 0.84 GeV/ c 2 . A simultaneous determination of M A and M V gives M A = 0.94 ± 0.07, M V = 0.81

A study of the centrally produced π+π-π+π- channel in pp interactions at 450 GeV/c

The reaction pp ->pf (pi+pi-pi+pi-) ps has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dPT filter applied. In addition to the well known f1(1285) there is evidence for two JPC=2-+ states called the eta2(1620) and eta2(1875) and a broad scalar called the f0(2000). The production of these states as a function of the dPT kinematical filter shows the behaviour expected for qqbar states. In contrast, there is evidence for two states at 1.45 GeV and at 1.9 GeV which do not show the behaviour observed for qqbar states.Abstract The reaction pp → pf(π+ π− π+ π−)ps has been studied at 450 GeV/c in an experiment designed to search for gl states. A spin analysis has been performed and the dPT filter applied. In addition to the well know f1(1285) there is evidence for two JPC = 2−+ states called the η2(1620) and η2(1875) and a broad scalar called the f0(2000). The production of these states as a function of the dPT kinematical filter shows the behaviour expected for q q states. In contrast, there is evidence for two states at 1.45 GeV and at 1.9 GeV which do not show the behaviour observed for q q states.

Neutral strange-particle production in p̄20Ne reactions at 607 MeV/c

Abstract The Λ 0 and K 0 s production cross sections have been measured at 607 MeV/ c for the reaction p + 20 Ne → V 0 + X ( V 0 =Λ, 0 , K 0 s ) . The Λ 0 /K 0 s production ratio is found to be (2.3±0.7). The data are consistent with an evaporative character of the emission mechanism from a multinucleon system for Λ 0 and from one nucleon for K 0 s . The rapidity distributions of negative tracks in K 0 x events are different from those in Λ 0 events without V 0 .

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.

A study of the centrally produced φφ system in pp interactions at 450 GeV/c

The reaction pp ! pfps(K + K K + K ) in which the K + K K + K system is centrally produced has been studied at 450 GeV/c. production has been found to dominate this reaction and is compatible with being produced by double Pomeron exchange. An angular analysis of the system favours J PC =2 ++ and its dPT dependence is similar to that observed for glueball candidates.The reaction pp to pfps(K+K-K+K-) in which the K+K-K+K- system is centrally produced has been studied at 450 GeV/c. Phi phi production has been found to dominate this reaction and is compatible with being produced by double Pomeron exchange. An angular analysis of the phi phi system favours JPC = 2++ and its dPT dependence is similar to that observed for glueball candidates.

Strangeness production in antiproton annihilation at rest on 3He, 4He and 20Ne

Abstract New data are reported on antiproton annihilations at rest with production of Λ and K s 0 , using a streamer chamber with 3 He, 4 He and 20 Ne as gas targets. The data include Λ, K s 0 , ΛK s 0 and K s 0 K S 0 production rates and momentum distributions, π − momentum spectra, mean numbers of charged particles generally and of negatively charged particles separately for different reaction channels. The yields are compared to simple combinatorial calculations based on the extreme assumptions of Λ production via B = 1 or via B = 0 ( K rescattering) annihilations. Λ and K s 0 momentum spectra are compared to simple model calculations where B = 0 and B = 1 annihilations with and without final-state interactions are considered. A review of existing data on Λ and K s 0 production is presented, showing the dependence on the p momentum and on the mass number of the target.

Antiproton-neon annihilation at rest and at 607 MeV/c

Abstract The analysis is based upon pNe annihilation events at rest and at 607 MeV/c detected with a self-shunted streamer chamber exposed to the LEAR beams. The main measured quantities are the following: charged-prong multiplicity, negative pion multiplicity; momentum, angular and rapidity distributions. General distributions are given as well as distributions as functions of charged prong multiplicity. A correlation is found between high multiplicity and depth of the annihilation point. The data are compared with recent theoretical analyses.

A study of the KKπ channel produced centrally in pp interactions at 450 GeV/c

Results are presented of an analysis of the reactions pp ->pf(k0k+pi-)ps and pp ->pf(K0K0pi0)ps at 450 GeV/c. Clear f1(1285) and f1(1420) signals are seen and a spin parity analysis shows that both have IG JPC=0+ 1++. The f1(1285) decays to a0(980)pi and the f1(1420) decays to K* Kbar. Both states have a similar dependence as a function of dPT consistent with what has been observed for other qqbar states. Evidence is also presented for a K*Kbar decay mode of the eta2(1620).Abstract Results are presented of an analysis of the reactions pp → pf(KS0K±π±)ps and pp → pf(KS0KS0π0)ps at 450 GeV/c. Clear f1(1285) and f1(1420) signals are seen and a spin parity analysis shows that both have IGJPC = 0+1++. The f1(1285) decays to a0(980)π and the f1(1420) decays to K ∗ K . Both states have a similar dependence as a function of dPT consistent with has been observed for other q q states. Evidence is also presented for a K ∗ K decay mode of the η2(1620).

Production of strange particles in antineutrino interactions at the CERN PS

Abstract We have studied neutral strange particle production in the bubble chamber Gargamelle filled with propane and exposed to antineutrinos from the CERN PS. Cross sections are presented for Λ, Σ0 and K0 production. Associated production reactions (ΔS = 0) have been observed in the charged and the neutral current channels. From 45 candidates for the quasi-elastic reaction ν p → μ + Λ , on bound and free protons, estimates of the axial transition form factor MA have been made using the total cross section and the t distribution. The weighted average from the two methods is MA = 862 ± 190 MeV. From a subsample of 15 candidates for ν interactions on free protons in propane, with (28±6)% background from ν interactions on bound protons, we obtain MA = 883 ± 243 MeV. The polarization of the Λ hyperons has been studied for the quasi-elastic reaction. We observe a significant Λ polarization in the production plane, normal to the Λ line of flight. The observed polarizations agree well with the predicted theoretical polarizations without any contribution from second-class axial coupling.

Pionic annihilation of antiprotons stopped on 3He

Abstract The pionic annihilation of antiprotons stopped on 3 He nuclei in a self-shunted streamer chamber exposed to the antiproton beam of LEAR is studied. The data concern charged-particle multiplicity distributions, branching ratios for different final states, the probability of final-state interaction, π − , π + , p and d momentum spectra, like and unlike pion angular correlations, π and other charged-particle angular correlations. The comparison of the 3 He data with those obtained on 1 H, 2 H and 4 He does not reveal relevant effects due to the increase of the nucleon number; the small differences can be seen as due to a weak final-state interaction.