Collective flows of protons andπ−mesons in2H+C,Ta and He

Abstract

Abstract. Collective flows of protons and negative pions have been studied in 2 H+C, Ta and He+C, Ta collisions at energy of 3.4 GeV/nucleon. The data has been obtained by 2m Propane Bubble Chamber (PBC-500) at JINR. It is found that the directed flow of protons and π − -mesons characterized by d< P x >/d(y) increases with increase of the mass numbers of colliding nucleus pairs; the elliptic proton flow points out of the reaction plane and also strengthens as system mass increases; the negative pion directed flow is in the reaction plane as proton one for the lighter ( 2 H+C, He+C) systems and in the opposite direction for the heavier ( 2 H+Ta, He+Ta) systems. In 2 H+C, He+C, C+C, C+Ne, 2 H+Ta, He+Ta, C+Cu and C+Ta collisions, the linear dependence of directed and elliptic flow parameters from mass numbers of projectile and target nuclei ─ (A P . A T ) 1/2 , is similar for protons while for π − -mesons the dependence of directed flow parameters is stronger. The Ultra-relativistic Quantum Molecular Dynamical Model (UrQMD) enlarged by the Statistical Multi-fragmentation Model (SMM) satisfactorily describes the obtained experimental results for all pairs of nuclei. The data for such asymmetric nuclear collisions are obtained for the first time.

Study of collective flows of protons and $π^{-}$ -mesons in p(C, Ta) and He(Li, C) collisions at momenta of 4.2, 4.5 and 10 AGeV/c

“…It is apparent that the π − mesons and protons flow are in the opposite in-plane directions, in the forward and backward hemispheres, in all nuclear systems. The flow parameter absolute values for π − mesons and protons decrease with increasing of projectile momentum and of mass numbers A T of target nuclei, what is opposite the results in nucleus-nucleus collisions ( 2 H + C, He + C, C + C, 2 H + Ta, He + Ta, and C + Ta collisions) obtained at the same energy and on the same setup [18], [20]. Interestingly, the proton and π − mesons collective flow parameters in He+C collisions of SKM-200-GIBS with the pure, solid thin targets are comparable with those from collisions with C 3 H 8 (PBC-500, our earlier results) [20].…”

“…In order to study the properties of nucleus-nucleus interactions, the collective flows of protons, pions and Λ hyperons were previously investigated [17]- [20] by the authors of the present paper at beam energies of 3.4 and 3.7 AGeV. According to the study, the flow parameters of protons and negative pions increase at an increase of the mass of projectile and target nuclei ((A P + A T ) 1/2 ) in 2 H + C, He + C, C + C, C + Ne, 2 H + Ta, He + Ta, C + Cu, and C + Ta collisions.…”

On transverse momentum spectra of negative pions in 12C+181Ta collisions at 4.2A GeV/c

“…40 It is necessary to mention that the collective flow of protons and negative pions was also observed experimentally in He+C, C+C, C+Ne, C+Cu and C+Ta collisions within the momentum range of 4.2-4.5A GeV/c. 27,41,42 Hence, the observed twotemperature shape of the transverse momentum spectrum of the negative pions produced in 12 C+ 181 Ta collisions at 4.2A GeV/c could also be interpreted by the collective flow effects. The spectral temperatures (T 1 , T 2 ) of π − mesons in 12 C+ 181 Ta collisions at 4.2A GeV/c and their relative contributions (R 1 , R 2 ) extracted in the present work from fitting the p t spectra by the two-temperature Hagedorn and the twotemperature Boltzmann functions are presented in Table 3.…”

Phenomenological analysis of rapidity distribution of negative pions in central 12C+12C collisions at $\sqrt{s_{nn}} = 3.14\, {\rm GeV}$

“…The collective flow of protons and negative pions was also observed experimentally in He+C, C+C, C+Ne, C+Cu and C+Ta collisions at a momentum range of 4.2A-4.5A GeV/c. 48,71,72 One can have a rough estimate for an average width (∆y centr ) of central rapidity region for pions coming from expansion and freeze-out of a compressed nuclear matter in central 12 C+ 12 C collisions at √ s nn = 3.14 GeV. As the longitudinal component of the collective flow of the particles, in the case of central symmetric collisions, expands simultaneously with the same β L to opposite longitudinal directions from the cm of collision system, the rough estimate for ∆y centr can be proposed as follows:…”