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Register a new userGlauber Monte Carlo predictions for ultra-relativistic collisions with ${}^{16}{rm O}$
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We explore Glauber Monte Carlo predictions for the planned ultra-relativistic ${}^{16}{rm O}$+${}^{16}{rm O}$ and p+${}^{16}{rm O}$ collisions, as well as for collisions of ${}^{16}{rm O}$ on heavy targets. In particular, we present specific collective flow measures which are approximately independent on the hydrodynamic response of the system, such as the ratios of eccentricities obtained from cumulants with different numbers of particles, or correlations of ellipticity and triangularity described by the normalized symmetric cumulants. We use the state-of-the-art correlated nuclear distributions for ${}^{16}{rm O}$ and compare the results to the uncorrelated case, finding moderate effects for the most central collisions. We also consider the wounded quark model, which turns out to yield similar results to the wounded nucleon model for the considered measures. The purpose of our study is to prepare some ground for the upcoming experimental proposals, as well as to provide input for possible more detailed dynamical studies with hydrodynamics or transport codes.
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We discuss multiplicity fluctuations of charged particles produced in nuclear collisions measured event-by-event by the NA49 experiment at CERN SPS within the Glauber Monte Carlo approach. We use the concepts of wounded nucleons and wounded quarks in the mechanism of multiparticle production to characterize multiplicity fluctuations expressed by the scaled variance of multiplicity distribution. Although Wounded Nucleon Model correctly reproduce the centrality dependence of the average multiplicity in Pb+Pb collisions, it completely fails in description of corresponding centrality dependence of scaled variance of multiplicity distribution. Using subnucleonic degrees of freedom, i.e. wounded quarks within Wounded Quark Model, it is possible to describe quite well the multiplicity distribution of charged particles produced in proton+proton interactions. However, the Wounded Quark Model with parameters describing multiplicity distribution of particles produced in proton+proton interactions substantially exceeds the average multiplicity of charged particles produced in Pb+Pb collisions. To obtain values of average multiplicities close to those experimentally measured in Pb+Pb collisions, the concept of shadowed quark sources is implemented. Wounded Quark Model with implemented shadowing source scenario reproduces the centrality dependence of scaled variance of multiplicity distribution of charged particles produced in Pb+Pb collisions in the range from the most central to mid-peripheral interactions.
In hydrodynamicalmodeling of heavy-ion collisions the initial state spatial anisotropies translate into momentum anisotropies of the final state particle distributions. Thus, understanding the origin of the initial anisotropies and quantifying their uncertainties is important for the extraction of specific QCD matter properties, such as viscosity, from the experimental data. In this work we study the wounded nucleon approach in the Monte Carlo Glauber model framework, focusing especially on the uncertainties which arise from the modeling of the nucleon-nucleon interactions between the colliding nucleon pairs and nucleon-nucleon correlations inside the colliding nuclei. We compare the black disk model and a probabilistic profile function approach for the inelastic nucleon-nucleon interactions, and study the effects of initial state correlations using state-of-theart modeling of these.
Next-to-leading order (NLO) QCD predictions for the production of heavy quarks in proton-proton collisions are presented within three different approaches to quark mass, resummation and fragmentation effects. In particular, new NLO and parton shower simulations with POWHEG are performed in the ALICE kinematic regime at three different centre-of-mass energies, including scale and parton density variations, in order to establish a reliable baseline for future detailed studies of heavy-quark suppression in heavy-ion collisions. Very good agreement of POWHEG is found with FONLL, in particular for centrally produced D^0, D^+ and D^*+ mesons and electrons from charm and bottom quark decays, but also with the generally somewhat higher GM-VFNS predictions within the theoretical uncertainties. The latter are dominated by scale rather than quark mass variations. Parton density uncertainties for charm and bottom quark production are computed here with POWHEG for the first time and shown to be dominant in the forward regime, e.g. for muons coming from heavy-flavour decays. The fragmentation into D_s^+ mesons seems to require further tuning within the NLO Monte Carlo approach.
The parity-transfer $({}^{16}{rm O},{}^{16}{rm F}(0^-,{rm g.s.}))$ reaction is presented as a new probe for investigating isovector $0^-$ states in nuclei. The properties of $0^-$ states provide a stringent test of the threshold density for pion condensation in nuclear matter. Utilizing a $0^+ rightarrow 0^-$ transition in the projectile, the parity-transfer reaction transfers an internal parity to a target nucleus, resulting in a unique sensitivity to unnatural-parity states. Consequently, the selectivity for $0^-$ states is higher than in other reactions employed to date. The probe was applied to a study of the $0^-$ states in ${}^{12}{rm B}$ via the ${}^{12}{rm C}({}^{16}{rm O},{}^{16}{rm F}(0^-,{rm g.s.}))$ reaction at $247~{rm MeV/u}$. The excitation energy spectra were deduced by detecting the ${}^{15}{rm O}+p$ pair produced in the decay of the ${}^{16}{rm F}$ ejectile. A known $0^-$ state at $E_x = 9.3~{rm MeV}$ was observed with an unprecedentedly high signal-to-noise ratio. The data also revealed new candidates of $0^-$ states at $E_x=6.6 pm 0.4$ and $14.8 pm 0.3~{rm MeV}$. The results demonstrate the high efficiency of $0^-$ state detection by the parity-transfer reaction.
We present the results of an improved Monte Carlo Glauber (MCG) model of relevance for collisions involving nuclei at center-of-mass energies of BNL RHIC ($sqrt{s_{rm NN}}=0.2$ TeV), CERN LHC ($sqrt{s_{rm NN}}=2.76$-$8.8$ TeV), and proposed future hadron colliders ($sqrt{s_{rm NN}}approx 10$-$63$ TeV). The inelastic pp cross sections as a function of $sqrt{s_{rm NN}}$ are obtained from a precise data-driven parametrization that exploits the many available measurements at LHC collision energies. We describe the nuclear transverse profile with two separated 2-parameter Fermi distributions for protons and neutrons to account for their different densities close to the nuclear periphery. Furthermore, we model the nucleon degrees of freedom inside the nucleus through a lattice with a minimum nodal separation, combined with a recentering and reweighting procedure, that overcomes some limitations of previous MCG approaches. The nuclear overlap function, number of participant nucleons and binary nucleon-nucleon collisions, participant eccentricity and triangularity, overlap area and average path length are presented in intervals of percentile centrality for lead-lead (PbPb) and proton-lead (pPb) collisions at all collision energies. We demonstrate for collisions at $sqrt{s_{rm NN}}=5.02$ TeV that the central values of the Glauber quantities change by up to 7%, in a few bins of reaction centrality, due to the improvements implemented, though typically remain within the previously assigned systematic uncertainties, while their associated uncertainties are generally smaller (mostly below 5%) at all centralities than for earlier calculations. Tables for all quantities versus centrality at present and foreseen collision energies involving Pb nuclei, as well as for collisions of XeXe at $sqrt{s_{rm NN}}=5.44$, and AuAu and CuCu at $sqrt{s_{rm NN}}=0.2$ TeV, are provided.
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