Colour rope model for extreme relativistic heavy ion collisions

It is experimentally observed that the width of the KNO multiplicity distribution -or the negative binomial parameter, 1/k-for pp collisions, in the energy region 10 √ s 1800 GeV, is an increasing function of the energy. We argue that in models with parton or string saturation such trend will necessary change: at some energy the distribution will start to become narrower. In the framework of percolating strings, we have estimated the change to occur at an energy of the order of 5-10 TeV.

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“…In Figure 1 we present plots of (11) and (12). The average multiplicity is, naturally, a growing function of the density.…”

Section: The Toy Modelmentioning

confidence: 99%

“…It is the parameter η that controls clustering: when N strings cluster, the effective colour charge is not proportional to N but, due to the vectorial nature of colour summation [12], is proportional to F (η)N, where [13] …”

Section: Theoretical Frameworkmentioning

confidence: 99%

Density saturation and the decrease of the normalised width of the multiplicity distribution in high energy pp collisions

et al. 2004

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“…This initial-state model is used as for all configurations assuming transparency and QGP. It assumes an initial interpenetration of Lorentz-contracted slabs (in most present models considered as Color Glass Condensate), and strong attractive coherent Yang-Mills fields act between these end slabs, with large string tension (according to the color rope model [20]). During the slowing down of these expanding fields the original net baryon charge is considered to be longitudinally uniformly distributed in the streak-by-streak expanding system and then, in the subsequent initial Riemann scaling expansion, the net baryon charge follows this expansion.…”

mentioning

confidence: 99%

Vorticity in peripheral collisions at the Facility for Antiproton and Ion Research and at the JINR Nuclotron-based Ion Collider fAcility

et al. 2014

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The flow vorticity development is studied in the reaction plane of peripheral relativistic heavy-ion reactions at energies just above the threshold of the transition to a quark-gluon plasma (QGP). Earlier calculations at higher energies with larger initial angular momentum predicted significant vorticity leading to measurable polarization. Here we discuss the possibility of vorticity and circulation in dense plasma at lower temperatures. In low-viscosity QGP this vorticity still remains significant. Fluid dynamical processes in heavy-ion reactions were studied for a long time [1][2][3], and their use is becoming more dominant in recent years. With the quark-gluon plasma (QGP) production in these reactions, the scope of the fluid dynamical studies is widening at the same time [4]. As in the present studies, both different fluctuating modes and global collective processes lead to flow observables, so it becomes important to separate or split the two types of flow processes from each other [5,6]. This separation would help the precise analysis of both processes.In peripheral heavy-ion reactions due to the initial angular momentum, the initial state of the fluid dynamical stage of the collision dynamics has shear flow characteristics, and this leads to rotation [7] and even the Kelvin-Helmholtz instability (KHI) [8] in the reaction plane for a low-viscosity quark-gluon plasma. This possibility was indicated by high-resolution computational fluid dynamics (CFD) calculations using the Particle in Cell (PIC) method. We study the development of these processes in a (3 + 1)-dimensional (3 + 1)D configuration to describe the energy and momentum balance realistically. The presently used relativistic PICR hydro was the first, which included the QGP equation of state (EoS) [9], the y and p t spectra were evaluated and the softening of the EoS was predicted in 1994, leading to a strong change of p x (y)/a [or v 1 (y)], [10][11][12], which led to the prediction of the third flow component or antiflow [13]. This was then measured at the BNL Relativistic Heavy-Ion Collider (RHIC) and presented in 2006 [14]. Just as in the publications discussing the RHIC (including the Beam Energy Scan) results [15][16][17][18], here we also used the initial-state model assuming transparency and strong attractive fields with accurate impact-parameter dependence and rapidity distribution in the transverse plane [19]. This initial-state model is used as for all configurations assuming transparency and QGP. It assumes an initial interpenetration of Lorentz-contracted slabs (in most present models considered as Color Glass Condensate), and strong attractive coherent Yang-Mills fields act between these end slabs, with large string tension (according to the color rope model [20]). During the slowing down of these expanding fields the original net baryon charge is considered to be longitudinally uniformly distributed in the streak-by-streak expanding system and then, in the subsequent initial Riemann scaling expansion, the net baryon charge follows thi...

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“…Obviously the standard UrQMD calculation, which can be seen as a baseline of known hadronic physics, strongly underestimates the (multi-)strange particle yields in central collisions, in particular in the case of the Ω − . Only the inclusion of non-hadronic medium effects, like color-ropes [32], which are simulated by increasing the string-tension for central collisions, enhances the yield to a level of near-compatibility with the data. Similar findings have also been made in the context of HIJING calculations [33].…”

Section: Multi-strange Baryonsmentioning

confidence: 99%