We observe a resonancelike structure in the total cross section for hadron production by e+e− colliding beams at a mass of 4414 ± 7 MeV having a total width Γ=33±10 MeV. From the area under this resonance, we deduce the partial width to electron pairs to be Γee=440±140 eV. Further structure of comparable width is present near 4.1 GeV.
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We have measured the inclusive cross section for the reactions p+n→p+X and π++n→p+X at 100 GeV/c in the kinematic region |t|<1.0 GeV2. The data were obtained from an exposure of the Fermilab 30-in. deuterium-filled bubble chamber to a tagged positively charged beam. The differential cross sections for these reactions are observed to scale in the ratio of the pn and π+n total cross sections and to be consistent with the predictions of a Reggeized one-pion-exchange model.
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We present a comparative study of inclusive and semi-inclusive pion production in pp collisions at 102 and 400 GeV/ c . In particular, we examine the correlation between transverse and longitudinal momentum variables and the energy dependence of invariant cross sections.
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The inclusive production of π and η mesons at 90° from proton-proton collisions has been measured at the CERN ISR at centre-of-mass energies between 23.5 and 62.4 GeV. The momentum correlation of charged particles emitted together with a large transverse momentum pion has also been studied, using two magnetic spectrometers each centred at 90°.
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We present the inclusive and semi-inclusive production of protons, π+, π−, for the full range of kinematic variables, from 7850 inelastic interactions obtained in the 4.7 m liquid-hydrogen bubble chamber Mirabelle at the Serpukhov accelerator and with an incident proton beam of 69 GeV/c. We compare the data with those at other energies, and we give the results of different phenomenological fits.
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The reactions e + d → e ' + p S + p + π − and e + d → e ' + n S + n + π + were measured detecting electron and pion in coincidence at an invariant hadronic mass of 2.19 GeV. The measurements were performed at electron four-momentum transfer squared of f 2 = 0.70 and 1.35 GeV 2 in the range of t = ( γ v − π ) 2 between t min and −1.0 GeV 2 . The cross section d 2 σ / dtdφ of the reaction e + n → e' + p + π − was determined.
ACTUALLY RATIO OF PI- TO PI+ PRODUCTION OFF DEUTERIUM.
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The production of multipion events by e + e − annihilation has been measured at centre of mass energies 915,990 and 1076 MeV. Both channels e + e − → π + π − π o and e + e − → π + π − π + π − have been analysed. An energy threshold effect analysed. An energy threshold effect around 919 MeV ( m ω + m π o ) has been evidenced for the π + π − π o π o channel and the cross section is consistent with the quasi two-body process e + e − → ωπ o . The cross section for π + π − π + π − is lower by an order of magnitude and increases with the energy.
SYSTEMATIC ERROR INCLUDED. RADIATIVE EFFECT (<15 PCT) INCLUDED.
MULTIHADRON PRODUCTION CROSS SECTION DEDUCED AS SUM OF FOUR PION CHANNELS.
An analysis of the Kπ-system in the mass region of the K ∗ (1780), based on a sample of 46000 K s o π + final states, is presented. Evidence for a relatively narrow width, τ ≈ 100 MeV, and for the spin parity assignment J P = 3 − is found.
SLOPE DETERMINED WITHIN 0.2 < -T < 0.8 GEV**2 AND USED TO ESTIMATE TOTAL CROSS SECTION.
A partial wave analysis of the K 0 π + π − system produced in the charge exchange reaction K − p → ( K 0 π + π − ) n at 4.2 GeV/ c has been performed both as a function of Kππ mass and of t ′. The 1 + S wave forms the largest contribution to the K ππ system and peaks at roughly the same mass as the Q in diffractive K ππ production. The polarization properties of the 1 + S ( K ∗ π) and 1 + S (Kϱ) waves differ fromt those of the diffractive 1 + wave. There is some evidence for a resonance contribution to 1 + S ( K ∗ π) . The strong 2 + wave the K ∗ (1420) and the K ϱ/ K ∗ ϱ decay branching ratio determined to be 0.36±0.10. An enhancement with spin-parity 1 − is observed under K ∗ (1420) .
CROSS SECTION CORRECTED FOR BREIT-WIGNER TAILS, THE TP CUT, UNSEEN <AK0 PI> AND <K RHO> DECAY MODES. BRANCHING RATIO K*(1420) --> <K RHO>/<K* PI> = 0.36 +- 0.10.
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Based on a sample of about 3500 events, we have measured the total and differential cross sections of p p → n n in the 700–760 MeV/ c incident momentum region. It is found that σ CE = 10.7 ± 0.2 mb at the average momentum of 730 MeV/ c . The differential angular distribution is characterised by a sharp peak and a dip in the forward direction followed by a secondary maximum. The position of the dip corresponds to | t | ≈ m π 2 . These results are compared with the predictions of the model of Bryan-Phillips. On the other hand, this dip-bump structure can be well understood on a simple picture involving a π exchange and a constant background (for | t | ≲ 3 m π 2 ).
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