Results on charged particle production in pp̄ collision at s 1 2 = 540 GeV are presented. The data were obtained at the CERN pp̄ collider using the UA1 detector, operated without magnetic field. The central particle density is 3.3 + - 0.2 per unit o pseudo-rapidity for non-diffractive events. KNO scaling of the multiplicity distributions withresults from ISR energies is observed.
An analysis of theA-dependence of the target-diffractive cross-section is presented. Data on thet-dependence of the cross section are fitted in the usual exponential form. The mean multiplicity of negative particles produced diffractively is found not to be sensitive to the nuclear mass. TheA-dependence of the emitted proton multiplicity and the angular distributions of the produced charged particles suggest re-scattering of the emitted particles on other nucleons of the nucleus. All these facts are compared with results obtained by Monte-Carlo simulation according to a two-component Dual Parton Model.
Central collisions of O16 nuclei with the Ag107 and Br80 nuclei in nuclear emulsion at 14.6, 60, and 200 GeV/nucleon are compared with proton-emulsion data at equivalent energies. The multiplicities of produced charged secondaries are consistent with the predictions of superposition models. At 200 GeV/nucleon the central particle pseudorapidity density is 58±2 for those events with multiplicities exceeding 200 particles.
None
We present a study of the structure of hadronic events recorded by the L3 detector at LEP at the center of mass energies of 161 and 172 GeV. The data sample corresponds to an integrated luminosity of 21.25 pb −1 collected during the high energy runs of 1996. The distributions of event shape variables and the energy dependence of their mean values are well reproduced by QCD models. From a comparison of the data with resummed O ( α s 2 ) QCD calculations, we determine the strong coupling constant at the two energies. Combining this with our earlier measurements we find that the strong coupling constant decreases with increasing energy as expected in QCD.
None
Measurements of the midrapidity transverse energy distribution, $d\Et/d\eta$, are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV and additionally for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=62.4$ and 130 GeV. The $d\Et/d\eta$ distributions are first compared with the number of nucleon participants $N_{\rm part}$, number of binary collisions $N_{\rm coll}$, and number of constituent-quark participants $N_{qp}$ calculated from a Glauber model based on the nuclear geometry. For Au$+$Au, $\mean{d\Et/d\eta}/N_{\rm part}$ increases with $N_{\rm part}$, while $\mean{d\Et/d\eta}/N_{qp}$ is approximately constant for all three energies. This indicates that the two component ansatz, $dE_{T}/d\eta \propto (1-x) N_{\rm part}/2 + x N_{\rm coll}$, which has been used to represent $E_T$ distributions, is simply a proxy for $N_{qp}$, and that the $N_{\rm coll}$ term does not represent a hard-scattering component in $E_T$ distributions. The $dE_{T}/d\eta$ distributions of Au$+$Au and $d$$+$Au are then calculated from the measured $p$$+$$p$ $E_T$ distribution using two models that both reproduce the Au$+$Au data. However, while the number-of-constituent-quark-participant model agrees well with the $d$$+$Au data, the additive-quark model does not.
None
Forum