We have obtained the branching ratios for p p annihilation at rest into π + π − and K + K − in a pure p p initial angular momentum state L = 1. A gaseous hydrogen target at normal pressure and temperature was used and events associated with transitions of the antiprotonic atom to the 2p level were selected by detecting the Balmer X-ray series. The branching ratios for p p annihilation into π + π − and K + K − from the 2p state are (4.81 ± 0.49) × 10 −3 and (2.87 ± 0.51) × 10 −4 , respect The pion yield is slightly larger than in liquid hydrogen, where L = 0 annihilation dominates, while the kaon yield is suppressed by a factor of four. Using these and previous data, we derive the branching ratios for pp annihilation into all ππ and K K modes from S and P states. A measurement in gaseous hydrogen, without X-ray requirement, yields the branching ratios (4.30 ± 0.14) × 10 −3 and (6.92 ± 0.41) × 10 −4 . With the known branching ratios of (3.33 ± 0.17) × 10 −3 and (1.01 ± 0.05) × 10 −3 in liquid hydrogen, we find that (50.3 ± 6.4)% of all annihilations in gas at NTP occur in the initial angular momentum state L = 1.
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
We have measured the deuteron A ( Q 2 ) structure function in the momentum transfer region between 1 and 18 fm −2 . The accuracy of the data ranges from 2 to 6%. These measurements allow a sensitive test of theoretical predictions. We find that meson-exchange currents and relativistic corrections significantly improve the agreement between experiment and theory. We investigate the sensitivity of A ( Q 2 ) to the nucleon-nucleon interaction and to the neutron electric form factor G E n ( Q 2 ). Our analysis shows that G E n ( Q 2 ) can be extracted from these data with a significantly improved accuracy. The model dependence of this analysis is discussed.
Axis error includes +- 15/15 contribution.
Axis error includes +- 15/15 contribution.
Axis error includes +- 15/15 contribution.
Analysing powers and differential cross sections for p p → π − π + and p p → K − K + have been measured over the full angular range using a polarised target at LEAR at 20 beam momenta from 360 to 1550 MeV/ c . Discrepancies in the normalisation of earlier d σ/ d Ω data at low momenta are clarified. Above 1000 MeV/ c , A 0N results confirm values close to +1 over most of the angular range for both reactions, in excellent agreement with earlier data of lower statistics. Below 1000 MeV/ c , where the analysing power is measured for the first time, large variations of A 0N with energy and angle are present.
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We present a study of the inclusive η production based on 300 000 hadronic Z 0 decays. The measured inclusive momentum distribution can be reproduced by parton shower Monte Carlo programs and also by an analytical QCD calculation. Comparing our results with low energy e + e − data, we find that QCD describes both the shape and the energy evolution of the η spectrum. The comparison of η production rates in quark- and gluon-enriched jet samples does not show statistically significant evidence for more abundant production of η mesons in gluon fragmentation.
Differential cross section for inclusive eta production, normalized to the total hadronic cross section.
Differential cross section for inclusive eta production, normalized to the total hadronic cross section.
A measurement of the cross-sections for single and double prompt photon production in p p interactions at s = 630 GeV is presented. The data sample corresponds to an integrated luminosity of 13.2 pb −1 . The results are in good agreement with the predictions of perturbative QCD. The signal from double prompt photon production has a statistical significance of 4.3 standard deviations.
There is an overall systematic error of 9 pct not included in the table.
Errors quoted include statistical and all PT dependent systematic uncertainties. There is in addition a 6.8 pct overall normalization uncertainty.
This work represents the results of an experimental investigation of the electromagnetic dissociation of 200 GeV/nucleon 16 O and 32 S ions in nuclear emulsions. Exclusive channels involving charged fragments have been studied as a function of the energy released, and, assuming a Weizsäcker-Williams spectrum of virtual photons, there is a good agreement with results for the (γ, p) processes obtained with real photons. However, the rates found for other processes are larger, in particular for the (γ, α) on both nuclei. The values of the total integrated absorption cross sections are generally larger than those obtained from real photon experiments but the extent of the discrepancy depends strongly upon which photon results are used in the comparison.
ELECTROMAGNETIC DISSOCIATION IN NUCLEAR EMULSION.
ELECTROMAGNETIC DISSOCIATION IN NUCLEAR EMULSION.
NUCLEUS IS THE EMULSION.
The mean multiplicity and the angular distribution of the charged pions produced in the n̄ annihilation on Fe in the range from 12 to 140 MeV is presented. The experimental technique and methods of analysis are described. A comparison with the p̄ results is performed, together with a discussion of some possible pion-nucleus interaction mechanisms in the above n̄ energy range.
No description provided.
The production of μ−e+ dileptons by muon neutrinos is studied in a high-statistics bubble-chamber experiment. The experiment consisted of exposing the Fermilab 15-ft bubble chamber filled with a heavy Ne-H2 mix to a wideband neutrino beam. In a total sample of 146 700±11 700 charged-current interactions, 461 events with an e+(Pe+>300 MeV/c) and a μ− are observed. The rate for μ−e+ dilepton production in measured to be (0.42±0.06)%. The energy dependence of this rate is presented. The kinematic distributions for the μ−e+ events are consistent with charm production and subsequent semileptonic decay. A total of 60 KS0 and 31 Λ0 decays were observed in the μ−e+ event sample. The measured rates for neutral-strange-particle production are 0.78±0.12 K0K¯0's and 0.19±0.04 Λ0's per μ−e+ event. Finally, rates for Λc+, D0, and D+ production in charged-current νμ interactions are derived. They are found to be (4−2+10)%, (1.7−0.7+0.5)%, and (1.3−0.5+0.4)%, respectively.
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We present preliminary results on the measurement of a variety of exclusive hadron interactions at center of mass scattering angles of 90°. Data are also presented which show the relative transparency of nuclei to πp and pp elastic scattering in this kinematic range.
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This paper presents and contrasts features of the inelastic nuclear reactions of 200 GeV/nucleon 16 O and 32 S ions with emulsion nuclei. Both the multiplicities of shower particles and the extent of target fragmentation have been studied for varying degress of disruption of the projectile nuclei. The results may be interpreted within a simple geometrical model. In particular the rapidity distributions of those events which exhibit complete projectile break-up without any overt sign of low-energy target fragmentation have been determined. The interaction of secondary projectile fragments of charge two or more issuing from oxygen interactions were also studied and the mean free paths in emulsion of the primary 16 O and 32 S ions and all such fragments have been compared to those predicted by a simple Glauber model.
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