The influence of Bose-Einstein correlations on intermittency inp\bar p collisions at\sqrt s = 630 GeV

The influence of Bose-Einstein correlations on the rise of factorial moments is small in the 1-dimensional phase space given by the pseudorapidity η, where the 2-body correlation function is dominated by unlike-sign particle correlations. Contraily, the influence is dominant in the higher dimensional phase space. This is shown by using correlation integrals. They exhibit clear power law dependences on the four-momentum transferQ ² for all orders investigated (i=2–5). When searching for the origin of this behaviour, we found that the Bose-Einstein ratio itself shows a steep rise forQ ²→0, compatible with a power law.     

Bose-Einstein correlations inK + p and π+ p at 250 GeV/c

Two-pion correlations are studied for pions of like charge inK ⁺ p andπ ⁺ p collisions at 250 GeV/c. An enhanced production is observed at small momentum difference and is attributed to Bose-Einstein interference between identical particles. A systematic study is presented on the influence of parametrization and reference sample. Interpreted in terms of the Kopylov-Podgoretskii parametrization a size of the emitting regionr _K ≈1.4 fm is found. The Lorentz invariant parametrization of Goldhaber givesr _G ≈0.8 fm. With fixed parametrization, similarity is found for hadronhadron,e ⁺ e ^? and lepton-hadron collisions. No multiplicity or angular dependence is found at our energy.     

Inclusive production of charged pions in p+p collisions at 158 GeV/c beam momentum

New results on the production of charged pions in p+p interactions are presented. The data come from a sample of 4.8 million inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. Pions are identified by energy loss measurement in a large TPC tracking system which covers a major fraction of the production phase space. Inclusive invariant cross sections are given on a grid of nearly 300 bins per charge over intervals from 0 to 2 GeV/c in transverse momentum and from 0 to 0.85 in Feynman x. The results are compared to existing data in overlapping energy ranges. Arrival of the final proofs: 8 December 2005     

Inclusive production of charged pions in p?+?C collisions at 158?GeV/c beam momentum

The production of charged pions in minimum bias p+C interactions is studied using a sample of 377000 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.8 GeV/c in transverse momentum and from -0.1 to 0.5 in Feynman x_F. Inclusive invariant cross sections are given on a grid of 270 bins per charge, thus offering for the first time a dense coverage of the projectile hemisphere and of the cross-over region into the target fragmentation zone.     

Rapidity dependence of multiplicity distributions in proton-nucleus collisions at 360 GeV/c

Multiplicity distributions in various rapidity intervals for charged particles produced in collisions of 360 GeV/c protons with aluminium (Al) and gold (Au) targets are presented. The data were analysed separately for the forward and backward hemispheres. Each distribution is well described by a negative binomial distribution. The experimental distributions are compared with the predictions of the multichain model calculated by the Monte Carlo program MCMHA in which the intranuclear cascade process is included, and also with the Lund Monte Carlo FRITIOF. The results of MCMHA reproduce quite well the multiplicity distributions for various rapidity intervals.     

Two-particle correlations in 360 GeV/cp p interactions

Two particle correlations of hadrons produced in 360 GeV/cpp interactions are investigated in the transverse plane and in rapidity. The data were obtained at the European hybrid spectrometer equipped with a rapid cycling bubble chamber. The observed transverse and rapidity correlations are compared with the one string LUND-and a two string dual parton-model. These models predict in general stronger correlations in the transverse plane and much weaker correlations in rapidity than found in the data. The LUND-FRITIOF-and multichain dual parton models provide a better reproduction of the data, although the agreement is not yet satisfactory. Only the UA5 cluster model GENCL shows agreement with the data.     

Rapidity and azimuthal correlations in π − p and π −C collisions at 40 GeV/c

New results are presented that were obtained from an analysis of experimental data on rapidity and azimuthal correlations in π ^? p and π ^?C collisions at 40 GeV/c. Some nonstandard methods for seeking correlations are developed. Dynamical correlations associated with fluctuations of the number of intranuclear collisions at a given multiplicity are discovered in π ^?C collisions. It is shown that the Lund model cannot describe the experimental data being discussed.     

Multiparticle production in proton-nucleus collisions at 360 GeV/c using the European Hybrid spectrometer

360 GeV/c proton interactions with aluminium (Al) and gold (Au) targets are studied using the European Hybrid Spectrometer (EHS) equipped with the Rapid Cycling Bubble Chamber (RCBC). Multiplicities, rapidity distributions and correlations between leading and other produced particles are presented and compared with Monte Carlo calculations based on the multi-chain and Lund models.     

Two-kaon correlations in central Pb+Pb collisions at 158 a GeV/c

Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.     

An event mixing technique for Bose-Einstein correlations of two pions in photoproduction around 1 GeV

We have developed an event mixing technique to observe Bose-Einstein correlations (BEC) between two identical neutral pions produced in photo-induced reactions in the non-perturbative QCD energy region. It is found that the missing-mass consistency cut and the pion-energy cut are essential for the event mixing method to effectively extract BEC observables. A Monte Carlo (MC) simulation is used to validate these constraints and confirms the efficiency of this method. Our work paves the way for similar BEC studies at lower energies where the multiplicity of emitted bosons is limited.     

Angular distributions of muon pairs produced by 194 GeV/c negative pions

We present the angular distributions of muon pairs obtained in a high-statistics experiment using a 194-GeV/c π^- impinging on a tungsten target. Our results are based on the analysis of 145,000 events with positive Feynmanx and mass above 4.07 GeV/c², excluding the ? region. Simple first-order QCD relations allow us to determine the ratio of annihilation with hard-gluon emission to the sum of annihilation with hard-gluon emission and hard-gluon Compton scattering, which is found to be about 58% to 75%. We determine the parton square intrinsic transverse momenta to be of the order of 0.6 (GeV/c)², and about 30% larger in the pion than in the nucleon. At largex ₁, our data agree with the higher-twist hypothesis, and support the interpretation of the relevant scale parameter as the dimuon square transverse momentum.     

Collective characteristics of hadron systems produced in beam fragmentation of π+ p collisions at 250 GeV/c

Collective characteristics are studied of hadrons produced in beam fragmentation of non-single-diffractive π⁺ p-interactions at 250 GeV/c. An attempt is made to obtain experimental information on the properties of leading cluster production and fragmentation. On average, the leading cluster carries 0.8±0.1 of the incident momentum, so that the mean value of the inelasticity coefficient of 〈k〉=0.2±0.1 is significantly smaller than that deduced from leading single hadron spectra. The momentum transfer distribution shows that nonsingle-diffractive processes are less peripheral than diffraction dissociation. The analysis of thrust and sphericity shows jet-like structure of pion fragmentation, that of the charge flow an average forward charge of 〈Q _f 〉=0.45±0.04, in agreement with the average charge of the beam valence quarks. Our data are compared to diffraction dissociation and to the Fritiof model.     

Properties of high-energy pions emitted from heavy-ion collisions at 1 GeV/nucleon

Positively charged pions and protons from collisions of Ne+NaF and Au+Au at 1 GeV/nucleon incident energy were measured near midrapidity. The center-of-mass pion spectra deviate from a Maxwell-Boltzmann distribution. The slope of the high-energy part of the pion spectra varies significantly with the system mass and little with the size of the reaction zone. While the total pion yield rises linearly with the number of participant nucleons, the highenergy component increases more than linearly.     

Thermal emission of pions in antiproton-proton annihilation at 12 GeV/c

Using data of \(\bar pp\) annihilation at 12 GeV/c we have found that centrally-emitted pions follow a thermal energy spectrum with an inclusive temperature of 111±2 MeV, the same as has been found for pions produced in πp collisions at 16 GeV/c. An analysis of individual high-multiplicity events to search for fluctuations in the temperature parameter on an event-byevent basis has been made, using two different methods. We obtained the value 0.18±0.02 for the relative dispersion of the temperature fluctuations.