R. Sh. Hakobyan

Factorial moments, cumulants and correlation integrals in Pi+P and K+P interactions at 250 Gev/C

AbstractA selected sample of 59200 π+p andK+p nonsingle-diffrative interactions at

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

\sqrt s

Negative binomials and multiplicity distributions in 250 GeV/cK+ and π+ interactions on Al and Au nuclei

=22 GeV is used to investigate one, two- and three-dimensional factorial moments, factorial cumulant moments, as well as correlation integrals. The rise of factorial moments and cumulants with decreasing phase-space volume is stronger when evaluated in three than in lower dimensions. Ratios of slopes are easier to obtain than the slopes themselves. Contrary to earlier findings, they turn out to depend on the dimension. The order dependence of the averaged ratios is better described by a Lévy stable law solution with μ=1.6 than by Gaussian approximation of the α-model (μ=2) or a second order phase transition (μ=0), but values μ>2 inconsistent with Lévy-type fluctuations are reached in a three-dimensional analysis. The multiparticle contributions to the factorial moments are calculated by means of factorial cumulant moments. A particular improvement of the method is that of correlation (or density) integrals. It leads to the conclusion that Bose-Einstein interference plays an important role in the intermittency effect, but indication is found for an interpretation alternative to the conventional view of Bose-Einstein correlations.

Rapidity and transverse momentum structure in Pi+ and K+ collisions with Al and Au nuclei at 250 GeV/c

A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to π+p and K+p collisions at 250 GeV/c. Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.061±0.010. a Supported by the Government of the Republic of Armenia, contractnumber 94-496 b Permanent address: Department of Physics, Jingzhou Teacher’s College, Hubei 434100, China c Onderzoeksdirecteur NFWO, Belgium d Supported by the Polish State Committee for Scientific ResearchAbstract A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to π + p and K + p collisions at 250 GeV/ c . Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.061±0.010.

Nuclear-target diffraction dissociation inπ+ and K+ collisions with Au and Al 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 regionrK≈1.4 fm is found. The Lorentz invariant parametrization of Goldhaber givesrG≈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.

Backward proton production in π+ and K+ collisions with Al and Au nuclei at 250 GeV/c

Multiplicity distributions, observed inK+ interactions with Al and Au nuclei at 250 GeV/c incident momentum are presented. They are analyzed in the framework of multiple collisions of the incident particle inside a nucleus. The probability distribution of the number of grey tracks is well described by the model of Andersson et al., if a negative binomial distribution is assumed for the distribution of the number of grey protons produced per elementary collision instead of the usual geometrical distribution. The analysis of the average and dispersion of the charge multiplicity distribution supports the validity of the multiple collision model, including results on correlations between forward and backward multiplicities.

Two- and three-dimensional analysis of bose-einstein correlations inπ+/K+p interactions at 250 GeV/c

The negative binomial distribution (NBD) is fitted to all charged and to negative particle multiplicity distributions in restricted rapidity intervals, both in the forward and backward c.m. hemispheres of positive meson interactions on Al and Au nuclei. For negative particle multiplicity distributions, the NBD parameters are also determined as a function ofng, the number of grey tracks, corresponding to varying number of intranuclear collisions. The data are interpreted in terms of the clan picture of Giovannini and Van Hove and compared to the MCMHA and Fritiof models. Both models reproduce quite well the global multiplicity distributions, but not when sub-samples are considered with fixed number of grey tracks. Regularities are better visible on the parton than on the particle level.

Angular dependence of Bose-Einstein Correlations in Interactions of Pi(+) and K+ Mesons with Protons and Nuclei at 250 GeV/c

An analysis is presented of the rapidity and transverse momentum distributions and of the nuclear stopping power in collisions ofπ+ andK+ mesons with Al and Au nuclei at 250 GeV/c. The experimental results are compared to predictions of the additive quark model and the dual parton model. The AQM offers an overall consistent description of the data in this experiment. The DPM reproduces reasonably well the rapidity spectra in the central and projectile fragmentation regions, but fails to describe the nuclear stopping power.