The TPC/Two-Gamma Collaboration has measured the inclusive cross section for production of charmed D ∗± mesons in photon-photon collisions. The reaction utilized was e + e - →e + e - D ∗± X, with D ∗± →D O π +- , D O →K -+ π ± , and either zero or one outgoing e ± detected. The result, σ(e + e - → e + e - D ∗± X) = 74±26±19 pb , is in agreement with the quark parton mo del prediction for e + e - → e + e - c c , combined with a Lund model for the hadronization of the charmed quarks.
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Properties of the hadron multiplicity distributions in 280 GeV/c μ+p interactions have been investigated. The c.m. energy dependence in the range from 4 to 20 GeV of the total charged multiplicities are presented. No variation faster than logarithmic is seen in the energy range of this experiment. Comparison with νp and data at lower energy has been made and shows good agreement between μ+p and total charged multiplicities. It has been found that the average forward multiplicity (charged hadrons with xF > 0) exceeds the average backward multiplicity (charged hadrons with xF < 0) in the whole energy range and presents a different energy variation. The average forward multiplicity has been compared to e+e− data and shows a similar dependence on energy. Little correlation was observed between the forward and backward multiplicities indicating that the current and target regions fragment almost independently.
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The measurements of the z and p T 2 distribution of hadrons produced in the interactions of 200 GeV muons with copper and carbon nuclei are shown in different x Bj and virtual photon energy intervals. Effects of the jet scattering are seen at the lowest virtual photon energies while for energies above 70 GeV there is no evidence of these effects. Comparison with a theoretical model indicates that at high jet energies the parton fragmentation distance is greater than the nuclear radius and that the parton absorption cross section is less than 10 mb.
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The production of J/ ϑ and ϑ′ has been measured in 250 GeV muon iron interactions. The measured total cross sections are σ ( μ N → μ J/ ϑ X)=0.74±0.14 nb and σ ( μ N → μϑ ′X)=0.16 ± 0.07 nb. An upper limit on the cross section times branching ratio for ϒ production of BR · σ ( μ N → μϒ X) < 5.2 × 10 −38 cm 2 (at 90% confidence level) is obtained. About half the J/ ϑ cross section is found to have Z ⩾ 0.95 (where Z = E (J/ ϑ / ν ). The first-order photon-gluon fusion model agrees well with the measured Q 2 and ν dependence of the J/ ϑ data and is used to extract the gluon momentum distribution. However, higher order QCD effects are needed to explain the Z distribution of the J/ ϑ and the observed broadening of the P t 2 distribution with decreasing Z . The decay angular distributions of the J/ ϑ are found to be flat in the s -channel frame, but there is evidence for polarisation in the t -channel frame.
NUMBERS ARE CROSS-SECTIONS FOR PSI AND PSI(PRIME) BUT CROSS-SECTION*BR.RATIO FOR THE UPSILON.
THE COHERENT PRODUCTION IS NOT SUBTRACTED.
THE COHERENT PRODUCTION IS SUBTRACTED.
The cross sections for J ψ production have been measured in interactions of 280 GeV μ + on hydrogen and deuterium (H, D) and also in interactions of 250 GeV μ + on iron. The single-nucleon cross sections in iron are found to be larger than those in H, D. The mean ratio of the iron to H, D photoproduction cross sections in the range 60 < v < 200 GeV is 1.45 ±0.12 (statistical) ±0.22 (systematic error). Within the framework of the photon-gluon fusion model, this indicates that the gluon density per nucleon is ∼45% larger in iron than in H, D in the range 0.026 < x < 0.085, on a mass scale Q 2 eff ∼M 2 J ψ .
First table is from combined H and DEUT data at 280 Gev. Second table is from FE data at 250 Gev.
First table is from combined H and DEUT data at 280 Gev. Second table is from FE data at 250 Gev.
THIS TABLE IS THE RATIO OF THE EFFECTIVE GLUON DISTRIBUTIONS IN IRON AND HYDROGEN(DEUTERIUM) ASSUMING THAT PHOTON-GLUON FUSION IS THE RELEVANT MECHANISM FOR J/PSI PRODUCTION.
Results are presented on the transverse momentum distributions of charged hadrons in 280 GeV muon-proton deep inelastic interactions. The transverse momenta are defined relative to the accurately measured virtual photon direction and the experiment has almost complete angular acceptance for the final state hadrons. Significantly larger values of the average transverse momentum squared are found for the forward going hadrons than for the target remnants. This result, combined with a study of the rapidity region over which the transverse momentum is compensated, can be explained by a significant contribution from soft gluon radiation, but not by a large value of the primordial transverse momentum of the struck quark.
Errors given are statistical only.
Errors are statistical only.
Errors are statistical only.
The production of K 0 s, Λs and Λ s has been studied in a 280 GeV muon-proton scattering experiment with almost complete coverage of all kinematic regions. A study is made of the dependence of the multiplicities on the hadronic centre of mass energy, W , and of the Feynman x distributions. It is found that K 0 and Λ production is mostly central and increases strongly with W , whereas Λ production comes mainly from the remnant target system and is only weakly W dependent.
AVERAGE VALUES OF VARIABLES ARE <Q**2>=12GEV**2 , <NU>=76GEV , <W**2>=130GEV**2 , <X BJ>=0.11.
AVERAGE VALUES OF VARIABLES ARE <Q**2>=12GEV**2 , <NU>=76GEV , <W**2>=130GEV**2 , <X BJ>=0.11.
AVERAGE VALUES OF VARIABLES ARE <Q**2>=12GEV**2 , <NU>=76GEV , <W**2>=130GEV**2 , <X BJ>=0.11.
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Backward Multiplicity.
Forward Multiplicity.
No description provided.
Inclusive ϱ 0 meson production has been measured in 120 GeV and 280 GeV muon-proton interactions. Distributions of z and p T 2 are presented. Primary ϱ 0 production is found to be equal to that of π 0 production within errors.
No description provided.
No description provided.
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