The production of antineutrons and charged Σ's in e+e− annihilations has been measured at s=4 and 7 GeV and at the ψ(3.1) resonance. Two packages containing spark chambers, steel plates, and scintillation counters were added to each side of the Mark I detector at SPEAR. Antineutrons were identified by annihilations which produced large-angle charged prongs characteristic of a high-Q reaction. The resulting antineutron cross sections and momentum distributions are consistent with previous antiproton results. Charged Σ's were detected by forming mass combinations with the n's and charged tracks in the Mark I. A clear signal is seen in the 7-GeV and ψ data, with little or no signal at s=4 GeV. The increase in Σ± production between 4 and 7 GeV is consistent with simple expectations for charmed-baryon production. A search for the decays Λc−→Σ±π∓π− and Σc*Σc→Λc−π± yields no significant peaks. An upper limit, at the 90% confidence level, of σΛcB(Λc→Σ±π∓π−)<56 pb is set.
No description provided.
THE ANTI-SIGMA PRODUCTION CROSS SECTIONS WERE REPORTED IN T. FERGUSON ET AL., PL 79B, 161 (1978).
NOTE THAT TWICE THE ANTI-NEUTRON CROSS SECTIONS ARE PLOTTED IN THE FIGURES. NUMERICAL VALUES OF DATA ON FIGURES SUPPLIED BY T. FERGUSON.
The experimentally determined average charged-particle multiplicities, 〈nX〉, of the systems, X, produced in the following reactions for 147 GeV/c incident pion momentum are presented as functions of the square of the invariant mass of X, MX2, and of |t|:π−p→πfast−X, π−p→pX, π−p→Δ++X, π−p→(π−π+)ρ0X, and π−p→Λ0X. Details of the analysis are discussed. These data can be fit by the expression 〈nX〉=A+B ln MX2+C|t| and the coefficients obtained for B are equal within their uncertainties. C is significantly different from zero only for π−p→πfast−X. These results and 〈nX〉 data from other inclusive and total-inelastic-reaction studies are discussed in terms of a simple model which assumes contributions to 〈nX〉 from the target-fragmentation, the central, and the beam-fragmentation regions in the case of total-inelastic reactions. For inclusive reactions, either the beam or target fragmentation is replaced by an exchange-particle-fragmentation contribution. The s, t, and MX2 dependence of the parameters of the model are deduced from triple-Regge considerations. The data are found to be consistent with the model and values are presented for the parameters.
No description provided.
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The inclusive production of π 0 at large values of p T in pp collisions at the ISR has been studied. In this experiment the two photons are resolved and separately measured for p T values of up to 6 GeV/ c , giving confidence that the desired signal has been separated from various backgrounds.
No description provided.
We have observed e + e − hadrons at C.M. energies of 13 GeV and 17 GeV at PETRA using the TASSO detector. We find R (13 GeV) = 5.6 ± 0.7 and R (17 GeV) = 4.0 ± 0.7. The additional systematic uncertainty is 20%. Comparing inclusive charged hadron spectra we observe scaling between 5 GeV and 17 GeV for x = p / p beam > 0.2; however the 13 GeV cross section is above the 17 GeV cross section for smaller x . This may be due to copious bb̄ production. The events become increasingly jet like at high energies as evidenced by a shrinking sphericity distribution with increasing energy.
TAU HEAVY LEPTON CONTRIBUTION SUBTRACTED.
THESE DATA FOR S*D(SIG)/DX AT 13 AND 17 GEV ARE INCLUDED IN THE RECORD OF R. BRANDELIK ET AL., PL 89B, 418 (1980).
We find an increase in ∑ ± production between E cm = 4 and 7 GeV which is consistent with charmed baryon production models. A search for the decay ∧ c − → ∑ ± π ± π − yields no significant peaks.
43 +- 16 ANTI-SIGMAS DETECTED ALTOGETHER.
The polarisation parameters Σ, P and T have been measured for the process γ p→ π 0 p in the photon energy range 1300–2100 MeV and c.m. angles between 30° and 110°, in an experiment with a polarised beam and polarised target. The results are compared with a recent theoretical analysis which fits data from threshold to 16 GeV. The new data are in general agreement with the analysis, but with some significant discrepancies in detail.
No description provided.
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First results from the magnetic detector PLUTO at the new e + e − storage ring PETRA are shown. The ratio R of the cross section for hadron production to that for μ-pair production has been measured to be R = 5.0 ± 0.5 at 13 GeV and 4.3 ±0.5 at 17 GeV. Both values have an additional systematic error of 20%. The events show a typical 2-jet structure. The mean transverse momentum approaches a constant value with increasing energy implying a shrinkage of the jet opening angle.
TAU HEAVY LEPTON PAIR CONTRIBUTIONS HAVE BEEN SUBTRACTED. R AT 13 AND 17 GEV, TOGETHER WITH SOME SELECTED LOWER ENERGY MEASUREMENTS FROM PLUTO AT DORIS.
Data from earlier preprint DESY-79-06. NUMERICAL VALUES MEASURED OFF GRAPH IN PREPRINT.
Inclusive V0 production in 6.5-GeV/c K−p interactions is studied using the ANL 12-ft-diameter hydrogen bubble chamber. The total cross sections for inclusive K¯0 and Λ0 production are σ(K¯0)=7.98±0.49 mb and σ(Λ0)=3.94±0.24 mb. Semi-inclusive differential cross sections are determined as functions of Feynman x and transverse momentum squared of the V0's and of four-momentum transfer to the V0. The average charge multiplicity, the ratio 〈nc〉D, and the correlation function f2cc for the neutrally charged hadronic system recoiling from the V0 are determined as functions of the mass of the recoiling system. Results are used to examine universal aspects of multiparticle production.
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CROSS-OVER IS AT -T = 0.17 +- 0.02 GEV**2. DIVIDE BY 20 TO GET D(SIG)/DT IN MB/GEV**2. CORRECTED FOR LOST EVENTS FOR -T < 0.12 GEV**2.
FROM QUADRATIC EXPONENTIAL FIT TO D(SIG)/DT. BOTH STATISTICAL AND SYSTEMATIC ERRORS INCLUDED IN VALUES.
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