We present evidence for the exclusive reaction e+e−→Ds±Ds*∓, observed with the Mark III detector at the SLAC storage ring SPEAR. The Ds± is reconstructed in the φπ± decay mode, while the Ds*∓ is detected as a narrow peak in the recoil-mass distribution. The mass of the Ds* is found to be 2109.3±2.1±3.1 MeV/c2, yielding a Ds*−Ds mass difference of 137.9±2.1±4.3 MeV/c2. The width of the Ds* is <22 MeV/c2 at the 90%-confidence level. The observed signal corresponds to σ(e+e−→Ds+Ds*−+Ds−Ds*+)B(Ds+→φπ+)=30±6±11 pb at s=4.14 GeV.
No description provided.
The isoscalar nucleon structure functionsF2(x, Q2) andxF3(x, Q2) are measured in the range 0<Q2<64 GeV2, 1.7<W2<250 GeV2,x<0.7 using ν and\(\bar v\) interactions on neon in BEBC. The data are used to evaluate possible higher twist contributions and to determine their impact on the evaluation of the QCD parameter Λ. In contrast to previous analyses reaching to such lowW2 values, it is found that a low\(\Lambda _{\overline {MS} } \) value in the neighbourhood of 100 MeV describes the data adequately and that the contribution of dynamical higher twist effects is small and negative.
No description provided.
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Results are presented on π + p and K + p elastic scattering at 250 GeV/ c , the highest momentum so far reached for positive meson beams. The experiment (NA22) was performed with the european hybrid spectrometer. The π + p elastic cross section stays constant with energy while the K + p cross section increases.
No description provided.
No description provided.
ERRORS IN ELASTIC CROSS SECTIONS INCLUDE SYSTEMATIC ERRORS.
The ratio of the cross section for Σ0 inclusive production to the cross section for Λ0 inclusive production has been measured with 28.5-GeV/c protons incident on a beryllium target at an average laboratory production angle of 4°. This ratio was measured to be 0.278±0.011±0.05, where the uncertainties are statistical and systematic in that order. The ratio does not depend strongly on the momentum of the produced particle between 10 and 24 GeV/c. The effect of Σ0 contamination on previous determinations of the polarization of inclusively produced Λ0’s is discussed.
No description provided.
No description provided.
We have observed diffraction dissociation of KL0 mesons with a carbon target into the exclusive final states KS0π+π−, KS0ω, and KS0φ. The diffraction production cross section for these states is not strongly dependent on the incident energy, varying at most by 30% between 75 and 150 GeV. The mass distributions do not change appreciably as a function of laboratory energy. The ratio of the diffractive mass-threshold production of K*±π∓, KS0ρ, KS0ω, and KS0φ is compared with previously obtained lower-energy data.
TP (=T-TMIN) distribution for K0S PI+ PI- events satisfying the diffractive cuts.
TP distributions for K0S OMEGA and K0S PHI events which satisfy the diffractive cuts.
CROSS SECTIONS PER NUCLEUS.
Clear evidence is presented for the production of an Ω ∗− resonance of mass 2253±13 MeV/ c 2 and width 81±38 MeV/ c 2 in K − p interactions at 11 GeV/ c . The state is observed in the Ξ (1530)K̄ decay mode, and the corresponding inclusive cross section is estimated to be 630±180 nb. Comparisons are made with theoretical predictions and with similar states observed inhyperon beam induced data.
No description provided.
The production of strange baryons Σ± (1385) and Ξ− has been observed in e+e− annihilations at 29 GeV center-of-mass energy, by use of data obtained with the High Resolution Spectrometer at the SLAC storage ring PEP. The total mean multiplicities are measured to be 〈nΣ±(1385)〉=0.033±0.006±0.005 and &〉=0.016±0.004 ±0.004 per hadronic event. The results are in good agreement with the Lund string model.
Lund model extrapolation to full x range.
Lund model extrapolation to full x range.
No description provided.
Multihadronic e+e− annihilation events at a center-of-mass energy of 29 GeV have been studied with both the original (PEP 5) Mark II and the upgraded Mark II detectors. Detector-corrected distributions from global shape analyses such as aplanarity, Q2-Q1, sphericity, thrust, minor value, oblateness, and jet masses, and inclusive charged-particle distributions including x, rapidity, p⊥, and particle flow are presented. These distributions are compared with predictions from various multihadron event models which use leading-logarithmic shower evolution or QCD matrix elements at the parton level and string or cluster fragmentation for hadronization. The new generation of parton-shower models gives, on the average, a better description of the data than the previous parton-shower models. The energy behavior of these models is compared to existing e+e− data. The predictions of the models at a center-of-mass energy of 93 GeV, roughly the expected mass of the Z0, are also presented.
Aplanarity distribution.
QX Distribution(QX=SQRT(3)*(Q3-Q2)).
The (Q2-Q1) distribution.
The production of\(\bar D\) mesons in neutroncarbon interactions at 40–70 GeV/c has been investigated. The\(\bar D\) mesons were detected via the hadronic decay modes\(\bar D^0\to K^{* + } (892)\pi ^ -\) andD−→K*+(892)π−π−. In the kinematical regionxF>0.5 andpT<1 GeV/c the following inclusive cross sections were measured:\(\sigma _{\bar D^0 }= (28 \pm 14)\mu b\) and\(\sigma _{D^ -}= (28 \pm 13)\mu b\) per carbon nucleus. The invariant longitudinal momentum spectra can be described by (1−x)N with\(N_{\bar D^0 }= 1.1 \pm 0.5 \pm 0.4\) and\(N_{D^ -}= 0.8 \pm 0.4 \pm 0.4\) The transverse momentum spectra were parametrized by exp (−BpT2) with\(B_{\bar D^0 }= (1.2_{ - 0.9}^{ + 1.1} )({{GeV} \mathord{\left/ {\vphantom {{GeV} c}} \right. \kern-\nulldelimiterspace} c})^{ - 2} \) and\(B_{D^ -}= (1.8_{ - 1.0}^{ + 1.3} )({{GeV} \mathord{\left/ {\vphantom {{GeV} c}} \right. \kern-\nulldelimiterspace} c})^{ - 2} \).
No description provided.
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Mean charged multiplicity for NSD events extrapolated to the full phase space.
Charged particle pseudorapidity density for NSD events at pseudorapidiy = 0.
Corrected charged particle multiplicity distribution for NSD events.
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