Gisela Ranft

Azimuthal correlations in 40 GeV/c π−p collisions and the independent cluster model

Abstract Data on azimuthal correlations and their rapidity dependence are presented in inclusive and semi-inclusive reactions π − p → π + π + X,→ π − π − X and π + π − X at 40 GeV/ c . They show a long range as well as a short range effect. The short range effect, leading to different behaviour of d N /d φ near φ = 0 of like and unlike pion pairs is explained by identical and unidentical particle statistics. The predictions of the independent cluster model for the azimuthal asymmetry are in qualitative agreement with data of this experiment as well as those at 102 and 205 GeV/ c .

Identical particle effect in azimuthal correlations at small rapidity separation

Abstract The difference of the short range effect observed in azimuthal correlations of like and unlike particle pairs is interpreted as due to an identical and unidentical boson effect, resp., in the decay of clusters produced in the central region of hadron hadron collisions.

The velocity weight function F(λ) of the thermodynamical model and the multi-Regge model

Abstract Using the multi-Regge model we calculate the velocity weight function U(λ) which approximately agrees with the empirically determined function F(λ) of the thermodynamical model at energies between 10 and 30 GeV c except near λ = 0. Negatively charged particle spectra are represented well at 19.2 GeV c . U(λ) depends weakly an the primary energy as compared to the energy independence of F(λ). Presently it is not clear how this energy dependence will change if more multi-Regge graphs are included in the calculation of U(λ).

Interference of QCD and weak interactions and the detection of vector bosons by hadronic jets: pp and collisions with polarized and unpolarized beams

Abstract Two-jet and single-jet cross sections and spin asymmetries are studied in polarized and unpolarized proton-proton and antiproton-proton collisions at collider energies s = 200 to 1000 GeV . It is found that the interference terms between strong (QCD) and weak interactions strongly influence the parity violating weak cross section; especially, the vector boson peaks in pp cross sections and parity violating asymmetries are masked almost completely at the lower part of the energy range considered. In p p collisions the vector boson peaks survive and a measurement of parity-violating asymmetries of double- and single-jet cross sections should lead to clear signals of the vector bosons.

Effect of Bose-Einstein statistics on two-particle azimuthal and rapidity correlations

Abstract The short-range effect in azimuthal and rapidity correlations can be explained within the independent cluster model taking into account the cluster transverse momentum and the Bose-effect (identical particle effect) in the single as well as the two-cluster term. Good agreement with data from Dubna, NAL and ISR is obtained. From the data we determine parameters related to the longitudinal and transverse dimensions of the clusters.

Semiinclusive Two-Particle Correlations and Independent Cluster Emission at ISR Energies

Abstract Semiinclusive two-particle correlations are calculated in the independent cluster emission model. The resulting semi-inclusive correlation functions ϱ 2 n ( y 1 = y 2 = 0) agree rather than well experimental data, esp. with respect to the multiplicity dependence. The average number of charged particles per cluster found from comparison with semiinclusive data is 2.5 charged particles per cluster, a value found earlier also from analysis of inclusive correlations.

Multiplicity distributions in a multiperipheral fireball model

Abstract Multiplicity distributions are studied in the thermodynamic model. The approximate Koba, Nielsen, Olesen scaling behaviour of the data and Wroblewskis linear law can be understood in the thermodynamic model with multiperipheral production of fireballs. This production mechanism is also essential to understand two-particle rapidity correlations especially in the ISR energy range. There are contributions from diffractive and non-diffractive production of fireballs in the model, which agrees in this sense with the two-component models used recently to discuss multiplicity distributions. In contrast to other models, however, the non-diffractive component taken separately exhibits approximate KNO-scaling and accounts rather well for the behaviour of the data up to 300 GeV. For the fireball production mechanism choosen the cross section of the diffractive component is expected to be smaller than in other models and can lead to a two-maxima multiplicity distribution only at energies higher than predicted in other models.

QCD predictions for large-p⊥ hadron production by polarized hadrons

Abstract Cross sections are given for the scattering of polarized quarks and antiquarks according to lowest-order QCD perturbation theory. Non-vanishing spin asymmetries lead to observable effects for large-p⊥ hadron production in collisions of polarized hadrons, which are proposed as a test of the relevance of the QCD picture for large-p⊥ reactions.

Gauge vector boson pair production at\(\bar p\)p collider energies

AbstractWithin the standardSU(2)×U(1) model differential cross sections and angular distributions of all polarization states are studied for all channels of gauge vector boson pairs accessible in hadron hadron collisions,W+W−,Z0Z0,Zγ,ZW, γW. The zero in the unpolarized angular distribution ofq