Wounded quarks inA+A,p+A, andp+pcollisions

Abstract

We explore predictions of the wounded quark model for particle production and properties of the initial state formed in ultrarelativistic heavy-ion collisions. The approach is applied uniformly to A+A collisions in a wide collision energy range, as well as for p+A and p+p collisions at the CERN Large Hadron Collider (LHC). We find that generically the predictions from wounded quarks for such features as eccentricities or initial sizes are close (within 15%) to predictions of the wounded nucleon model with an amended binary component. A larger difference is found for the size in p+Pb system, where the wounded quark model yields a smaller (more compact) initial fireball than the standard wounded nucleon model. The inclusion of subnucleonic degrees of freedom allows us to analyze p+p collisions in an analogous way, with predictions that can be used in further collective evolution. The approximate linear dependence of particle production in A+A collisions on the number of wounded quarks, as found in previous studies, makes the approach based on wounded quarks natural. Importantly, at the LHC energies we find approximate uniformity in particle production from wounded quarks, where at a given collision energy per nucleon pair similar production of initial entropy per source is needed to explain the particle production from p+p collisions up to A+A collisions. We also discuss the sensitivity of the wounded quark model predictions to distribution of quarks in nucleons, distribution of nucleons in nuclei, and to the quark-quark inelasticity profile in the impact parameter. In our procedure, the quark-quark inelasticity profile is chosen in such a way that the experiment-based parametrization of the proton-proton inelasticity profile is properly reproduced. The parameters of the overlaid multiplicity distribution is fixed from p+p and p+Pb data.PACS numbers: 25.75Gz, 25.75.Ld

Mid-rapidity charged hadron transverse spherocity in pp collisions simulated with Pythia

“…Perhaps the most interesting result is the discovery of sQGP-like (ridge-like and flow-like behavior) features in small systems like those created in pp and p-Pb collisions [1][2][3][4][5][6]. The origin of such effects is still far from being understood, for instance, it has been shown that hydro calculations, where the formation of a hot and dense QCD medium is implicitly assumed, can describe qualitatively many features of data [7][8][9]. But, other approaches suggest that the phenomenon can be produced by initial state effects [10][11][12].…”

On wounded constituents in nuclear collisions

“…2 we show fireball eccentricities resulting from the wounded constituents in p+p collisions at the LHC. Both the ellipticity and triangularity are large, hence may lead to substantial harmonic flow, in accordance to the collectivity mechanism expected for collisions of small systems [22][23][24][25] at sufficiently high multiplicity. The eccentricities do not depend strongly on the multiplicity of produced particles (centrality), which shows that they originate from fluctuations and not the geometry of the collision.…”

“…In this talk we summarize the main results of our recent paper [1], where we explore predictions of the wounded quark model for particle production and the properties of the initial state formed in ultra-relativistic collisions of atomic nuclei.Particle-particle interactions at high energies usually lead to copious production of new particles whose number rises as a function of the collision energy. The charged particle multiplicity (N ch ) and its pseudorapidity density (dN ch /dη) are fundamental measurable quantities which serve as important characteristics of the global properties of the system.…”

“…In this talk we summarize the main results of our recent paper [1], where we explore predictions of the wounded quark model for particle production and the properties of the initial state formed in ultra-relativistic collisions of atomic nuclei.…”

“…One of the interesting results of [1] is that taking into account subnucleonic degrees of freedom in the description of the early phase of the collision one obtains the linear dependence of production of particles as a function of the number of wounded constituents, namely…”