[en] We present first measurements of the pseudorapidity and azimuth (η, φ) bin-size dependence of event-wise mean transverse-momentum (p_t) fluctuations for Au-Au collisions at √s_NN=200 GeV. We invert that dependence to obtain p_t autocorrelations on differences (η_Δ, φ_Δ) interpreted to represent velocity/temperature distributions on (η, φ). The general form of the autocorrelations suggests that the basic correlation mechanism is parton fragmentation. The autocorrelations vary rapidly with collision centrality, which suggests that fragmentation is strongly modified by a dissipative medium in the more central Au-Au collisions relative to peripheral or p-p collisions. (letter to the editor)

[en] We present the first study of the energy dependence of p_t angular correlations inferred from event-wise mean transverse momentum (p_t) fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies √s_NN = 19.6, 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. p_t angular correlation structure suggests that the principal source of p_t correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with √s_NN from the onset of observable jet-related (p_t) fluctuations near 10 GeV

[en] The advancement of experimental techniques, to extract the nuclear level density (NLD) and to measure the thermodynamical properties of the excited nuclei, have opened up a new platform to explore the response of the nuclear systems subjected to the thermodynamical changes and consequently the structural changes that impact the nuclear level density and emission spectra of the decaying nuclear systems. The significance of shell effects and the quenching of shell effects with the excitation energies on NLD is studied. Since the residual excitation energy (U_th) after particle evaporation has significant dependence on the separation energy S_N, the accurate determination of the value of S_N is essential for which the inclusion of shell correction energy is important. Excitation energy and NLD are shown to be impacted significantly by the shell effects, shell correction energy. The magic nucleus and deformed nucleus respond to excitation differently which gets reflected in NLD. Large deformation in odd-Z ⁶⁹As than even-even ⁷⁰Ge, contributes more to the level density but convergence of NLD curves with increasing excitation indicates the quenching of shell effects

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No abstract available

[en] In ultrarelativistic heavy-ion collision, the event-by-event variation of the elliptic flow v ₂ reflects fluctuations in the shape of the initial state of the system. This allows to select events with the same centrality but different initial geometry. This selection technique, Event Shape Engineering, has been used in the analysis of charge-dependent two- and three-particle correlations in Pb-Pb collisions at $\sqrt{s}$${}_{NN}$ = 2.76 TeV. The two-particle correlator $⟨<!--\; ???\; -->$cos(φ _α-φ _β)$⟩<!--\; ???\; -->$, calculated for different combinations of charges α and β, is almost independent of v ₂ (for a given centrality), while the three-particle correlator $⟨<!--\; ???\; -->$cos(φ _α+φ _β-2ψ ₂)$⟩<!--\; ???\; -->$ scales almost linearly both with the event v ₂ and charge-particle pseudorapidity density. The charge dependence of the three-particle correlator is often interpreted as evidence for the Chiral Magnetic Effect (CME), a parity violating effect of the strong interaction. However, its measured dependence on v ₂ points to a large non-CME contribution to the correlator. Comparing the results with Monte Carlo calculations including a magnetic field due to the spectators, the upper limit of the CME signal contribution to the three-particle correlator in the 10-15% centrality interval is found to be 26-33% at 95% confidence level.

[en] The chemical parameters used in reactive transport models are not known accurately due to the complexity and the heterogeneous conditions of a real domain. A reactive transport model needs five kinds of inputs: the hydraulic properties of the domain, the chemical reactions occurring and the chemical parameters, the boundary and initial conditions. We will focus here on the chemical part of the problem. To describe a reactive transport model, a set of chemical reactions is first chosen and after that the corresponding parameters are obtained, whatever the way. Nevertheless, the required chemical parameters are not known exactly. Because the described phenomena are non linear, low precision on the determination of the parameters can lead to rejection of an accurate set of reactions. Moreover it is not possible to determine if the divergence between the experimental results and the calculated one is due to a wrong set of reactions or to a insufficiently precise determination of the parameters. Today, parameter estimation is mainly done using batch experiments under unique experimental conditions with tools like FITEQL. Estimated parameters are then accurate for batch reactor and for a given experimental state such as imposed pH or fixed ionic force. Extrapolating these parameters to a natural uncontrolled systems is then very hazardous. We will present the development of an efficient algorithm in order to estimate the chemical parameters using Monte-Carlo method. The objective is to estimate these parameters using multi-conditional experiments. It will then be possible to make predictions under variable conditions (pH, ionic strength) which are more representative of natural systems. (authors)

[en] The correlations between event-by-event fluctuations of anisotropic flow harmonic amplitudes have been measured in Pb-Pb collisions at $\sqrt{s}$${}_{NN}$=2.76 TeV with the ALICE detector at the Large Hadron Collider. The results are reported in terms of multiparticle correlation observables dubbed symmetric cumulants. These observables are robust against biases originating from nonflow effects. The centrality dependence of correlations between the higher order harmonics (the quadrangular v ₄ and pentagonal v ₅ flow) and the lower order harmonics (the elliptic v ₂ and triangular v ₃ flow) is presented. The transverse momentum dependences of correlations between v ₃ and v ₂ and between v ₄ and v ₂ are also reported. The results are compared to calculations from viscous hydrodynamics and a multiphase transport (AMPT) model calculations. The comparisons to viscous hydrodynamic models demonstrate that the different order harmonic correlations respond differently to the initial conditions and the temperature dependence of the ratio of shear viscosity to entropy density (η/s). A small average value of η/s is favored independent of the specific choice of initial conditions in the models. The calculations with the AMPT initial conditions yield results closest to the measurements. Correlations among the magnitudes of v ₂, v ₃, and v ₄ show moderate p _T dependence in midcentral collisions. This might be an indication of possible viscous corrections to the equilibrium distribution at hadronic freeze-out, which might help to understand the possible contribution of bulk viscosity in the hadronic phase of the system. Lastly, together with existing measurements of individual flow harmonics, the presented results provide further constraints on the initial conditions and the transport properties of the system produced in heavy-ion collisions.

[en] We present measurements of bulk properties of the matter produced in Au+Au collisions at √s_NN= 7.7, 11.5, 19.6, 27, and 39 GeV using identified hadrons (π^±, K^±, p, and p̄) from the STAR experiment in the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). Midrapidity (| y | < 0.1) results for multiplicity densities dN / dy, average transverse momenta 〈pT〉, and particle ratios are presented. The chemical and kinetic freeze-out dynamics at these energies are discussed and presented as a function of collision centrality and energy. These results constitute the systematic measurements of bulk properties of matter formed in heavy-ion collisions over a broad range of energy (or baryon chemical potential) at RHIC.

[en] Here we present the first measurement of charge-dependent directed flow in Cu + Au collisions at √s$- (NN)$ = 200 GeV . The results are presented as a function of the particle transverse momentum and pseudorapidity for different centralities. A finite difference between the directed flow of positive and negative charged particles is observed that qualitatively agrees with the expectations from the effects of the initial strong electric field between two colliding ions with different nuclear charges. The measured difference in directed flow is much smaller than that obtained from the parton-hadron-string-dynamics model, which suggests that most of the electric charges, i.e., quarks and antiquarks, have not yet been created during the lifetime of the strong electric field, which is of the order of, or less than, 1fm / c .