Scaling features of charged-hadron spectra in AA collisions at RHIC in z presentation
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ELEMENTARY PARTICLES AND FIELDS Theory
Scaling Features of Charged-Hadron Spectra in AA Collisions at RHIC in z Presentation* M. V. Tokarev1)** and I. Zborovsky´ 2)*** Received March 21, 2008; in final form, August 15, 2008
Abstract—Results of analysis of experimental data on inclusive spectra of charged hadrons produced in heavy-ion collisions at RHIC are shown in z presentation. The data indicate similarity as a characteristic feature of mechanism of hadron production at high energies. It is argued that this property includes structure of the colliding objects, interaction of their constituents, and character of the fragmentation process. Relation of the scaling variable z with the entropy and “specific heat” of the interacting system is discussed. A microscopic scenario of the constituent interactions connected with the momentum distribution of hadrons in the final state is suggested. We estimate energy losses of particles in the produced matter characterized by the multiplicity density dNch /dη. PACS numbers: 25.75.Bh, 24.80.+y, 11.30.Ly DOI: 10.1134/S1063778809030211
1. INTRODUCTION The measurements of particle spectra at Relativistic Heavy Ion Collider (RHIC) led to the discovery of a substantial suppression of hadron yields in nucleus– nucleus collisions relative to proton–proton data [1– 4]. The suppression is observed in the region of high transverse momenta, typically more than few GeV/c. It is connected with the energy radiations of the outgoing high-pT partons propagating through dense matter formed in the central collisions of heavy nuclei. The energy losses in the dense medium are substantially larger than in the vacuum. Quantification of the effect in the final state is a difficult problem depending on complicated calculations and model assumptions. In this paper we analyze spectra of charged hadrons measured in heavy-ion collisions at RHIC and suggest a microscopic interpretation of the spectrum suppression in the framework of data z presentation. The approach is based on general principles valid in pp and AA interactions at high energies. Above systems represent collisions of extended objects interacting in terms of their constituents. Production of particles from the constituent interactions is governed by the principles of selfsimilarity, locality, and fractality. The self-similarity ∗
The text was submitted by the authors in English. Joint Institute for Nuclear Research, Dubna, Russia. 2) Nuclear Physics Institute, Academy of Sciences of the ˇ z, ˇ Czech Republic. Czech Republic, Re ** E-mail: [email protected] *** E-mail: [email protected] 1)
of hadron production is valid both in soft and hard physics. The locality and fractality are applied to hard processes at small scales. The principles are manifested by the z scaling [5] observed in pp collisions at high energies. The scaling includes particle spectra for various selection criteria with different charged multiplicities Nch . The general principles apply in the nucleus–nucleus interactions as well. We demonstrate that particle spectra for
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