Delayed clusters accompanying nonmesonic weak decay of the Λ\Lambda-hypernuclei: a clue to nonleptonic processes

The nonmesonic decay of $\Lambda$-hypernuclei provides access to the nonleptonic weak decay process $\Lambda N \to NN$, which is achievable only through the observation of hypernuclear ground-state decays. We continue the discussion of some specific cases which make it possible to detect a few exclusive transitions, namely, the stripping of nucleon from the ground state results in a resonance state decaying via emission of two clusters. Delayed clusters accompanying weak decay of light hypernuclei give a unique information on spin dependence of the weak decay matrix elements.Comment: Presented at International Bogolyubov Conference "Problems of Theoretical and Mathematical Physics" (dedicated to the 100th anniversary of the birth of N.N.~Bogolyubov) Dubna, Russia, August 21 - 27, 200

Fast hadron freeze-out generator, part II: noncentral collisions

The fast Monte Carlo procedure of hadron generation developed in our previous work is extended to describe noncentral collisions of nuclei. We consider different possibilities to introduce appropriate asymmetry of the freeze-out hyper-surface and flow velocity profile. For comparison with other models and experimental data we demonstrate the results based on the standard parametrizations of the hadron freeze-out hyper-surface and flow velocity profile assuming either a common chemical and thermal freeze-out or the chemically frozen evolution from chemical to thermal freeze-out. The C++ generator code is written under the ROOT framework and is available for public use at http://uhkm.jinr.ru/Comment: 27 pages including 7 figures as EPS-files; prepared using LaTeX package for publication in Physical Review

Centrality dependence of the expansion dynamics in Pb-Pb collisions at 158 A GeV/c

Two-particle correlation functions of negatively charged hadrons from Pb-Pb collisions at 158 GeV/c per nucleon have been measured by the WA97 experiment at the CERN SPS. A Coulomb correction procedure that assumes an expanding source has been implemented. Within the framework of an expanding thermalized source model the size and dynamical state of the collision fireball at freeze-out have been reconstructed as a function of the centrality of the collision. Less central collisions exhibit a different dynamics than central ones: both transverse and longitudinal expansion velocities are slower, the expansion duration is shorter and the system freezes out showing smaller dimensions and higher temperature.Comment: 22 pages, 11 figures, Te

Transverse Momentum and Rapidity Dependence of HBT Correlations in Au+Au Collisions at sqrt(s_NN) = 62.4 and 200 GeV

Two-particle correlations of identical charged pion pairs from Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeV were measured by the PHOBOS experiment at RHIC. Data for the 15% most central events were analyzed with Bertsch-Pratt and Yano-Koonin-Podgoretskii parameterizations using pairs with rapidities of 0.4 < y_{\pi\pi} < 1.3 and transverse momenta 0.1 < k_T < 1.4 GeV/c. The Bertsch-Pratt radii R_o and R_l decrease as a function of pair transverse momentum, while R_s is consistent with a weaker dependence. R_o and R_s are independent of collision energy, while R_l shows a slight increase. The source rapidity y_{ykp} scales roughly with the pair rapidity y_{\pi\pi}, indicating strong dynamical correlations.Comment: 5 pages, 4 figures, 2 tables, submitted to Phys. Rev.

Rapidity and k_T dependence of HBT correlations in Au+Au collisions at 200 GeV with PHOBOS

Two-particle correlations of identical charged pion pairs from Au+Au collisions at sqrt(s_NN) = 200 GeV were measured by the PHOBOS experiment at RHIC. Data for the most central (0--15%) events were analyzed with Bertsch-Pratt (BP) and Yano-Koonin-Podgoretskii (YKP) parameterizations using pairs with rapidities of 0.4 < y < 1.3 and transverse momenta 0.1 < k_T < 1.4 GeV/c. The Bertsch-Pratt radii decrease as a function of pair transverse momentum. The pair rapidity Y_pipi roughly scales with the source rapidity Y_YKP, indicating strong dynamical correlations.Comment: 5 pages, 2 figures. To appear in the proceedings of Seventeenth International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California from January 11-17, 2004. Submitted to Journal of Physics G: Nuclear and Particle Physic

Sensitivity of HBT interferometry to the microscopic dynamics of freeze-out

We study the HBT interferometry of ultra-relativistic nuclear collisions using a freezeout model in which free pions emerge in the course of the last binary collisions in the hadron gas. We show that the HBT correlators of both identical and non-identical pions change with respect to the case of independent pion production. Practical consequences for the design of the event generator with the built in Bose-Einstein correlations are discussed. We argue that the scheme of inclusive measurement of the HBT correlation function does not require the symmetrization of the multi-pion transition amplitudes (wave-functions).Comment: 22 pages, 3 epsf figures, RevTe

Totally Chaotic Poissonian-Like Sources in Multiparticle Production Processes?

In all multiparticle processes the concept of sources directly emitting finally observed secondaries (mostly pions) plays crucial role. Here we shall present them from yet another point of view in which elementary sources composing all processes (from e+e- annihilation, via pp up to AA interactions) remain both totally 'chaotic' and Poissonian at the same time.Comment: 24 pages in plain LaTex (the only change: the file includes also figures this time