UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2009 Meeting


Section: Nuclear and Elementary Particles Physics


Title:
On the correlations in nuclear collisions at high energies


Authors:
Al Jipa*, C Besliu*, St Velica*, M Calin*, V Covlea**, T Esanu*, E Stan***


Affiliation:
* Atomic and Nuclear Physics Chair, Faculty of Physics, University of Bucharest, ROMANIA

** Optics, Plasma, Laser and Spectroscopy Chair, Faculty

of Physics, University of Bucharest, ROMANIA

***Institute of Space Science, Bucharest, ROMANIA


E-mail
stefania_neo@yahoo.com stefaniavelica@gmail.com


Keywords:
correlation, high energy collisions, transversal momentum, longitudinal momentum, rapidity


Abstract:
On the basis of experimental results obtained in the BRAHMS Collaboration, we studied correlations between physical quantities that can offer information on the formation of a new phase of the nuclear matter, highly excited and dense. The main types of correlations investigated are those between rapidity and transverse momentum, net charge and rapidity, respectively.. In this analysis the experimental results obtained in nucleus-nucleus and proton-proton collisions by the BRAHMS Collaboration, at the available energies at the Relativistic Heavy Ion Collider from Brookhaven National Laboratory (USA) were used. The main results presented are for Au-Au and Cu-Cu collisions at . The rapidity range − 0.1 < y < 3.5 was chosen in the investigation of the rapidity-transverse momentum correlation and transverse momentum-longitudinal momentum, therfore the most experimental evidences for the quark-gluon plasma formation are related to it. The study of correlations between transverse momentum-longitudinal momentum did not indicate a significant change in the behavior from the classical expected anticorrelation. In the analysis of the correlation between rapidity and transverse momentum, for the and mesons, the particles detected with the BRAHMS experimental set-up, a regularity in the behaviour of these mesons was observed, under 1,5 GeV/c. The values of the correlation coefficients change significantly for values higher than 1,5 GeV/c. It is important to see the modification of these coefficinets for rapidities higher than 3. This behaviour could be associated with the behaviour of the nuclear modification factor in the rapidity ranges: y < 2 and y > 2. These are determined by the suppression of high transverse momentum. These results confirm the importance of correlations and fluctuations studies for characterization of the different possible phases of the nuclear matter. The obtained results are in good agreement with other experimental results.