Transverse momentum ( p T ) distributions of inclusive photons and neutral pions at midrapidity are measured with a lead glass calorimeter in 60 and 200 A GeV 16 O + nucleus and proton + nucleus reactions . The variation of the average transverse momentum is investigated as function of centrality, determined by measurements of the remaining energy of the projectile and the charged particle multiplicity. For small values of the entropy, deduced from the multiplicity density, an increase in average p T is observed levelling off for larger values of entropy. The target-mass and energy dependence of π 0 p T distributions are presented.
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Results are presented from reactions of 60 A GeV and 200 A GeV 16 O projectiles with C, Cu, Ag, and Au nuclei. Energy spectra measured at zero degrees and transverse energy distributions in the pseudorapidity range from 2.4 to 5.5 are shown. The average transverse energy per participant is found to be nearly independent of target mass. Estimates of nuclear stopping and of attained energy densities are made.
STOPPING POWER IS THE QUANTITY GIVEN IN THIS TABLE. IT IS DEFINED AS ( D(ET(EXP)/D(ETA) / D(ET(THEORY)/D(ETA) ) AND THE DENOMINATOR IS TAKEN TO BE 0.5*E(HADRON IN CM). ETA IS THE PSEUDO-RAPIDITY.
The multiplicities of charged secondaries from inelastic αp and αα collisions have been measured using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. Corrected multiplicity distributions for αα and αp interactions are compared with those for pp interactions and with theoretical predictions.
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Differential cross sections for αα and αp scattering have been measured at √ s =125 and 88 GeV, respectively, in the t range from −0.2 to −0.8 (GeV/ c ) 2 using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. Comparison with theoretical calculations using the Glauber model confirms the importance of including inelastic shadowing effects in very high energy nucleus-nucleus elastic scattering.
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PLAB IS CALCULATED ASSUMING STATIONARY HELIUM TARGET.
The inclusive production of charged hadrons has been measured in αα and αp collisions at nucleon-nucleon c.m. energies (√s nn )of 31 and 44 GeV, respectively, for transverse momenta p T up to 5 GeV/ c in the central rapidity ( y ) region. at high p T the yields are consistent with being 4 times and 16 times highere than the ones in pp interactions at y =0, for αp and αα interactions, respectively. However, an enhancement over these factors, as expected from an earlier FNAL experiment, cannot be ruled out.
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The production of neutral pions by the interaction of 200A·GeV p and16O projectiles with a Au target has been studied in the pseudorapidity range 1.5≦η≦2.1. Transverse momentum spectra have been measured between 0.4 GeV/c and 3.6 GeV/c and their dependence on the centrality of the collision has been investigated. The peripheral-collision spectra display a marked change of slope with a hard component starting at about 1.8 GeV/c, in contrast to central-collision data. The data are discussed in comparison to p+p and α+α data from the ISR.
Data obtained with minimum bias trigger conditions.
Data obtained with minimum bias trigger conditions.
Data for central collisions.
We employ data taken by the JADE and OPAL experiments for an integrated QCD study in hadronic e+e- annihilations at c.m.s. energies ranging from 35 GeV through 189 GeV. The study is based on jet-multiplicity related observables. The observables are obtained to high jet resolution scales with the JADE, Durham, Cambridge and cone jet finders, and compared with the predictions of various QCD and Monte Carlo models. The strong coupling strength, alpha_s, is determined at each energy by fits of O(alpha_s^2) calculations, as well as matched O(alpha_s^2) and NLLA predictions, to the data. Matching schemes are compared, and the dependence of the results on the choice of the renormalization scale is investigated. The combination of the results using matched predictions gives alpha_s(MZ)=0.1187+{0.0034}-{0.0019}. The strong coupling is also obtained, at lower precision, from O(alpha_s^2) fits of the c.m.s. energy evolution of some of the observables. A qualitative comparison is made between the data and a recent MLLA prediction for mean jet multiplicities.
Overall result for ALPHAS at the Z0 mass from the combination of the ln R-matching results from the observables evolved using a three-loop running expression. The errors shown are total errors and contain all the statistics and systematics.
Weighted mean for ALPHAS at the Z0 mass determined from the energy evolutions of the mean values of the 2-jet cross sections obtained with the JADE and DURHAMschemes and the 3-jet fraction for the JADE, DURHAM and CAMBRIDGE schemes evaluted at a fixed YCUT.. The errors shown are total errors and contain all the statistics and systematics.
Combined results for ALPHA_S from fits of matched predicitions. The first systematic (DSYS) error is the experimental systematic, the second DSYS error isthe hadronization systematic and the third is the QCD scale error. The values of ALPHAS evolved to the Z0 mass using a three-loop evolution are also given.
Measurements of target asymmetries and double-polarization observables for the reaction $\gamma p\to p\pi^0\pi^0$ are reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility (Bonn University) using the Bonn frozen-spin butanol (C$_4$H$_9$OH) target, which provided transversely polarized protons. Linearly polarized photons were produced via bremsstrahlung off a diamond crystal. The data cover the photon energy range from $E_{\gamma}$=650 MeV to $E_{\gamma}$=2600 MeV and nearly the complete angular range. The results have been included in the BnGa partial wave analysis. Experimental results and the fit agree very well. Observed systematic differences in the branching ratios for decays of $N^*$ and $\Delta^*$ resonances are attributed to the internal structure of these excited nucleon states. Resonances which can be assigned to SU(6)$\times$O(3) two-oscillator configurations show larger branching ratios to intermediate states with non-zero intrinsic orbital angular momenta than resonances assigned to one-oscillator configurations.
Target asymmetry for $\pi^0\pi^0$ as a function of the polar angle for bins of the incident photon energy in the range of $E_\gamma$ = 650-2600 MeV.
Target asymmetry for $\pi^0\pi^0$ as a function of the $\pi^0\pi^0$ invariant mass for bins of the incident photon energy in the range of $E_\gamma$ = 650-2600 MeV.
Target asymmetry for $\pi^0\pi^0$ as a function of the $\phi^*$ angle for bins of the incident photon energy in the range of $E_\gamma$ = 650-2600 MeV.
The strong coupling constant, αs, has been determined in hadronic decays of theZ0 resonance, using measurements of seven observables relating to global event shapes, energy correlatio
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
The three polarization tensor components of the deuteron produced in the H( p , d )π + reaction have been measured for the first time. The experiment was performed using a vertically polarized proton beam produced by the SATURNE accelerator. The deuteron polarization was measured with the POLDER polarimeter. The three polarizing powers t 20 00 , t 21 00 and t 22 00 and the three spin-transfer observables t 20 11 , t 22 11 and t 22 11 have been extracted at a proton kinetic energy of 580 MeV over a wide angular range and at two fixed center-of-mass angles, 132° and 151°, between 800 and 1300 MeV. The six observables, calculated in the C.M. helicity frame, have been compared with predictions of the most refined partial-wave analyses and also with the predictions of a theoretical coupled-channel model which includes the NN-NΔ transition. The comparison between the data and the theory/partial-wave analyses shows some discrepancies which get worse with increasing proton energy. Adding these data to the world database should improve significantly future partial-wave analyses. The A y 0 analyzing power has also been measured over the same kinematical range. The partial-wave analysis predictions are in good agreement with this observable.
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