Haut PDF Correlation between mean transverse momentum and anisotropic flow in heavy-ion collisions

Correlation between mean transverse momentum and anisotropic flow in heavy-ion collisions

Correlation between mean transverse momentum and anisotropic flow in heavy-ion collisions

IV. CONCLUSIONS We have shown that ATLAS results on ρ n in Pb+Pb collisions can be explained by hydrodynamics. The mech- anism driving the correlation between the mean trans- verse momentum and anisotropic flow in Pb+Pb colli- sions can be traced back to the initial density profile, i.e., to the early stages of the collision. This implies in turn that this observable has limited sensitivity to the details of the hydrodynamic expansion in general, and to the transport coefficients of the fluid in particular, as nicely confirmed by the hydrodynamic results (Fig. 9) of Ref. [42]. We have found that hp t i fluctuations are driven
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Collision-geometry fluctuations and triangular flow in heavy-ion collisions

Collision-geometry fluctuations and triangular flow in heavy-ion collisions

associated ridge particles was detected, also consistent with triangular flow. VI. SUMMARY We have introduced the concepts of participant triangularity and triangular flow, which quantify the triangular anisotropy in the initial and final states of heavy-ion collisions. It has been shown that inclusive and triggered two-particle azimuthal correlations at large η in heavy-ion collisions are well described by the first three Fourier components. It has been demonstrated that event-by-event fluctuations lead to a finite triangularity value in Glauber Monte Carlo events and that this triangular anisotropy in the initial geometry leads to a triangular anisotropy in particle production in the AMPT model. The third Fourier coefficient of azimuthal correlations at large pseudorapidity separations have been found to be dominated by triangular flow in the model. We have studied the ratio of the third and second Fourier coefficients of azimuthal correlations in experimental data and the AMPT model as a function of centrality, pseudorapidity range and trigger particle momentum. A qualitative agreement between data and model has been observed. This suggests that the ridge and broad away-side features observed in two-particle correlation measurements in Au + Au collisions contain a significant, and perhaps dominant, contribution from triangular flow. Our findings support previous evidence from
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Isospin tracing : a probe of nonequilibrium in central heavy ion collisions

Isospin tracing : a probe of nonequilibrium in central heavy ion collisions

After the inspection of the centrality dependence of Fig. 2, we show in Fig. 3 the rapidity dependence of RZ for the most central collisions. For this purpose we use the proton yield (A) whose relatively high cross sec- tions permit a fine subdivision of the rapidity bins. In- verting projectile and target changes, as expected, the sign of the RZ-values; besides that, both results agree within errors. The dashed-dotted line (±0.393 y (0) ) describes an average of both measurements (being the same except for the sign) and can be used to deconvo- lute the overall measured rapidity distribution dN/dy (0) (Fig. 3b) for Ru+Ru into separated rapidity distribu- tions for the projectile- and for the target-nucleons. For each rapidity bin, the number of projectile (target) nu- cleons was obtained as Npr = 0.5 (1 + 0.393 y (0) ) N (Ntr = 0.5 (1 − 0.393 y (0) ) N ). The overall dN/dy (0) distribution was obtained by extrapolating the measured transverse momentum spectra, within the backward de- tector acceptance, according to the procedure described in [5]. After deconvolution a shift between the two de- duced rapidity distributions emerges, demonstrating that a memory of the initial target/projectile translatory mo- tion survives throughout a central collision.
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Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at $\snn=2.76$ TeV

Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at $\snn=2.76$ TeV

respectively, and Ψ n is the n-th harmonic symmetry plane angle. For a smooth matter distribution in the colliding nuclei, the symmetry planes of all harmonics coincide with the reaction plane defined by the beam direction and the impact parameter, the vector connecting the centers of the two colliding nuclei at closest approach. In this case, for particles produced at midrapidity, all odd Fourier coefficients are zero by symmetry. Due to event-by-event fluctuations of the positions of the participating nucleons inside the nuclei, the shape of the initial energy density of the heavy-ion collision in general is not symmetric with respect to the reaction plane, and the Ψ n may deviate from the reaction plane. This gives rise to
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Viscous corrections to anisotropic flow and transverse momentum spectra from transport theory

Viscous corrections to anisotropic flow and transverse momentum spectra from transport theory

3 Institut de physique th´ eorique, Universit´ e Paris Saclay, CNRS, CEA, F-91191 Gif-sur-Yvette, France (Dated: July 13, 2015) Viscous hydrodynamics is commonly used to model the evolution of the matter created in an ultra-relativistic heavy-ion collision. It provides a good description of transverse momentum spectra and anisotropic flow. These observables, however, cannot be consistently derived using viscous hydrodynamics alone, because they depend on the microscopic interactions at freeze-out. We derive the ideal hydrodynamic limit and the first-order viscous correction to anisotropic flow (v 2 , v 3 and v 4 )
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Linear and cubic response to the initial eccentricity in heavy-ion collisions

Linear and cubic response to the initial eccentricity in heavy-ion collisions

sions above 35% centrality [11]. This has been recently shown to result from a slight upward curvature of the relation between v 2 and ε 2 [12]. In Sec. II, we show that these deviations can be quan- tified by adding a cubic response term to the usual linear response. We study the variation of the response coeffi- cients as a function of centrality in hydrodynamics. In Sec. III, we study the effect of the cubic response on elliptic flow fluctuations in relation with LHC data. In Sec. IV, we study the deviations between anisotropic flow and the predictor.
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Production of muons from heavy-flavour hadron decays at high transverse momentum in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ and 2.76 TeV

Production of muons from heavy-flavour hadron decays at high transverse momentum in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ and 2.76 TeV

The measured R AA is compared with various model predictions such as TAMU [56] and SCET [57] (Fig. 2, left), and MC@sHQ+EPOS2 [58, 59] (Fig. 2, right). In the TAMU model, the interactions are described by elastic collisions only. The SCET model implements medium-induced gluon radiation via modified splitting functions with finite quark masses. These SCET calculations depend on the coupling constant g which describes the coupling strength between hard partons and the QGP medium. Its value is g = 1.9–2. In the MC@sHQ+EPOS2 model, two different options are considered, including either energy loss from medium-induced gluon radiation and collisional (elastic) processes or only collisional energy loss. In the scenario with pure collisional energy loss, the scattering rates are scaled by a global factor K larger than unity (K = 1.5) in order to reproduce the R AA and elliptic flow of open heavy- flavour hadrons measured at midrapidity at the LHC [58]. With a combination of collisional and radiative energy loss, the scaling factor is K = 0.8. All these models also consider a nuclear modification of the PDF (EPS09) [17]. Note that in the MC@sHQ+EPOS2 model shadowing is not considered for beauty- quark production. In addition to independent fragmentation, a contribution of hadronisation via quark recombination is included in all models with the exception of SCET. The SCET calculations provide a fair description of the data in central collisions but deviate from the data in peripheral collisions. The TAMU calculations underestimate the suppression at p T > 6 GeV/c in central and semi-central collisions, in particular. Both versions of the MC@sHQ+EPOS2 model, without and with radiative energy loss, describe the measurement within uncertainties for all centrality classes over the entire p T interval. The results obtained at forward rapidity for muons from heavy-flavour hadron decays at √ s NN = 5.02 TeV complement those obtained at midrapidity for the electrons from heavy-flavour hadron decays [24] by the ALICE collaboration as well as the prompt D-meson [25, 26] and beauty measurements via B ± mesons [31], non-prompt D 0 [31] and J/ψ [30] by the ALICE and CMS collaborations. The measured R AA of muons from heavy-flavour hadron decays for p T > 8 GeV/c is compatible with that obtained for beauty (D 0 and J/ψ from beauty hadrons, B ± ) for p hadron T > 10 GeV/c [30, 31] within uncertainties, although in a different kinematic region (different p T and y intervals).
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Skewness of mean transverse momentum fluctuations in heavy-ion collisions

Skewness of mean transverse momentum fluctuations in heavy-ion collisions

w = N −1/4 σ, (B17) so that both conditions (B16) are satisfied in the limit N  1. We generate a large number of Monte Carlo events. For each event, we sample the positions of N sources, where N is the same for all events, according to the dis- tribution (B8). The initial entropy density in the event is then defined by Eqs. (B1) and (B15). We then compute the corresponding energy density, (x), using the equa- tion of state, Eq. (B9). Since the equation of state is scale invariant, the final results are independent of the normal- ization constant in Eq. (B15). We carry out two sets of calculations, using two different values of the speed of sound: c 2
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Reverse engineering of heavy-ion collisions : unraveling initial conditions from anisotropic flow data

Reverse engineering of heavy-ion collisions : unraveling initial conditions from anisotropic flow data

Neglected in these analyses is the first Fourier harmonic V 1 . The observed V 1 is smaller than V 2 and V 3 [ 3 , 10 ], and receives a sizable contribution from global momentum conservation [ 14 , 15 ], which makes its interpretation less straightforward. Fluctuations are expected to create a di- pole asymmetry in the system [ 16 ], resulting in a specific directed flow pattern, with high transverse momentum particles flowing in the direction of the steepest gradient and low p T particles flowing in the opposite direction. Hints of this directed flow have been extracted from pub- lished V 1 data at the Relativistic Heavy-Ion Collider (RHIC) by two of the authors [ 17 ], and its magnitude and p T -dependence were shown to be in agreement with ideal hydrodynamic calculations [ 18 ]. Note that this quan- tity is distinct from the directed flow observable that has been obtained in the past from measurements employing a rapidity-odd projection [ 19 ]. That rapidity-odd v 1 gives a negligible contribution to V 1 near midrapidity and repre- sents different physics [ 20 ].
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Primordial non-Gaussianity in heavy-ion collisions

Primordial non-Gaussianity in heavy-ion collisions

(Dated: August 7, 2019) We show that experimental data on cumulants of anisotropic flow in heavy-ion collisions probe the non-Gaussian statistics of the energy density field created right after the collision. We carry out a perturbative expansion of the initial anisotropies of the system in terms of its density fluctuations. We argue that the correlation between the magnitudes of elliptic flow and triangular flow, dubbed sc(3, 2), is generically of the same sign and order of magnitude as the kurtosis of triangular flow in a hydrodynamic picture. The experimental observation that these quantities are negative implies that the distribution of energy around a given point has positive skew.
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Isospin transport phenomena in semiperipheral heavy ion collisions at Fermi energies

Isospin transport phenomena in semiperipheral heavy ion collisions at Fermi energies

from the d/p ratio vs. v z (where v z is the particle centre of mass velocity component along the QP axis) and from < N > /Z vs. v z for Z=1,3,4. Concerning the isospin diffusion process [15-17], driven by the isospin gradient between target and projectile, exploiting the excellent isotopic resolution of FAZIA we observed a systematic isospin enrichment for the QP for the reaction on 48 Ca (Fig.3 of [12]), confirming other direct

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Centrality dependence of two-particle correlations in relativistic heavy ion collisions

Centrality dependence of two-particle correlations in relativistic heavy ion collisions

The offline event selection for p+p events are carried out for events with MinBias trigger, and, since the TO counters cannot be used for p+p triggering due to i[r]

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Systematics of central heavy ion collisions in the 1A GeV regime

Systematics of central heavy ion collisions in the 1A GeV regime

ple, studies of measured correlated adjacent detector hit probabilities in the Plastic Wall showed a worst case (Au+Au at 1.5A GeV) double hit probability of 8%, lowering the ap- parent total multiplicity, which was nearly compensated by a cross-talk between detector units of 6%, raising the apparent multiplicity. This cross talk was mainly due to imperfect alignment of the beam axis with the apparatus. The rationale for dropping further going detailed efficiency considerations within the filtered acceptances was that the charge bal- ances, after 4π reconstruction, were found to be accurate to typically 5% (see the tables in the appendix) for all the 25 system-energies studied, i.e. for a statistically significant sampling encompassing a large variation in energy and multiplicity. In our analysis the Plastic Wall and the CDC are treated as ’master’ detectors required for the registration of an ejectile. The Helitron efficiency was taken care of by matching its signals for H isotopes to Z=1 hits in the Plastic Wall after subtracting from the Plastic Wall hits the estimated pion contributions known from our earlier study [38]. At incident energies beyond 1A GeV, where the Plastic Wall showed a large background for Z ≥ 2, a matching of Z with the Helitron was required (in addition to track matching) using the energy loss signals and assuming for the Helitron the same efficiency as for Z=1. Other assumptions were found to be in conflict with the global charge balances. The Barrel, as a slave detector to the CDC, was used to improve isotope identification (for H and He) whenever its signal matched the CDC tracking. The mixing of adjacent particles is estimated to be less or equal to 10%, except for tritons and 3 He in the low energy run where it could be up to 20%.
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Coupling Constant Corrections in a Holographic Model of Heavy Ion Collisions

Coupling Constant Corrections in a Holographic Model of Heavy Ion Collisions

DOI: 10.1103/PhysRevLett.119.011601 Introduction. —Relativistic collisions of heavy ions at RHIC and LHC result in the formation of a strongly interacting state of matter known as the quark-gluon plasma (QGP). While these experiments provide an invaluable window into properties of quantum chromodynamics (QCD), our theoretical understanding of QGP in QCD remains far from complete. In recent years, gauge-gravity duality (holography) has enabled theoretical studies of certain, usually supersymmetric, classes of large-N field theories, which are most readily performed at infinitely strong ( ’t Hooft) coupling λ. As a result of those advances, many properties of QGP previously conceived as impen- etrably complex, such as its collective far-from-equilibrium behavior, can now be analyzed using numerical general relativity techniques. At infinite coupling, heavy ion collisions have been successfully modeled by (dual) colli- sions of gravitational shock waves in Einstein bulk theory with an extra dimension and a negative cosmological constant [1 –5] (see [6 –8] for reviews.).
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$J/\psi$ Production vs Transverse Momentum and Rapidity in p+p Collisions at $\sqrt{s}$ = 200 GeV

$J/\psi$ Production vs Transverse Momentum and Rapidity in p+p Collisions at $\sqrt{s}$ = 200 GeV

forward and backward rapidities over ∆φ = 360 ◦ . The data were recorded using a minimum bias trig- ger that requires at least one hit in each of the beam- beam counters (BBC) at forward and backward rapidity, 3.0 < |η| < 3.9. Di-electron events must pass an addi- tional trigger that consisted of an OR between the level-1 electron and photon triggers. The electron trigger re- quires matching hits between the EMCal and RICH in a small angular area with a minimum energy deposition of 0.4 GeV in any 2 ×2 patch of EMCal towers. The photon trigger requires a minimum energy deposition of 1.4 GeV in any 4×4 set of overlapping EMCal towers. A J/ψ trig- ger efficiency of 96% was achieved within the vertex range |z vtx | < 30 cm. Di-muon triggered events were selected
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In-medium effects in central heavy ion collisions at intermediate energies

In-medium effects in central heavy ion collisions at intermediate energies

Over the last decades, the Equation of State (EoS) of nuclear matter has been widely studied in nuclear re- actions in order to put constraints on theoretical mod- els. These latter aim to describe both nuclear proper- ties at microscopic scale and astrophysical phenomena at macroscopic scale. In the first case, the EoS allows to understand some aspects of the collision via the underly- ing mechanisms like deep inelastic scattering, fusion re- actions, collective motions to mention a few examples [1]. In the second one, the EoS allows to describe the heavy compact astrophysical objects, as for instance Core Col- lapse SuperNovae and the formation of neutron stars [2]. Transport properties of the nuclear medium, in partic-
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On the correlation between stiffness and strength properties of anisotropic laminates

On the correlation between stiffness and strength properties of anisotropic laminates

material. He considered a heterogeneous continuum composed of two constituents. The strength homogenisation was evaluated at both mesoscopic and macroscopic scales. The proposed model is very simple and makes use of the mixture law: at the macroscopic scale the strength is the average of the strengths of each constitutive phase, weighted by the corresponding material volume fraction. In [31] De Buhan and Taliercio addressed the same problem by extending the theoretical model proposed in [30] and by considering among the constitutive phases the presence of the fibre-matrix interface. The strength domain is assumed to vary point-wise and it is approximated by an equivalent homogenised strength field composed of two parts: the isotropic part, that does not depends upon the volume fraction, and the anisotropic one depending on the volume fraction of each phase. In [9] the most common phenomenological failure criteria (i.e. the Hill [22], Hoff- man [23], Tsai-Wu [24] and the Zhang-Evans [33] criteria) have been formulated in the mathematical framework of the polar method. This unified formulation through inva- tiants has been utilised to formulate and solve the problem of maximising the strength of a generic orthotropic sheet in terms of its material orientation. In [19] the unified formulation presented in [9] was generalised in order to formulate a homogenised failure criterion at the laminate level. The Tsai-Hill criterion was formulated (at the laminate level) in terms of the laminate strength invariants and the problem of maximising the strength of a laminated plate subject to in-plane loads was addressed.
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LOW AND INTERMEDIATE ENERGY HEAVY ION COLLISIONS IN THE SEMI-CLASSICAL MICROSCOPIC DESCRIPTION

LOW AND INTERMEDIATE ENERGY HEAVY ION COLLISIONS IN THE SEMI-CLASSICAL MICROSCOPIC DESCRIPTION

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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Analysis of scaling of energy and baryon densities in relativistic heavy-ion collisions

Analysis of scaling of energy and baryon densities in relativistic heavy-ion collisions

With the full E802/E866 data available, we have been able to determine and compare shapes and magnitudes of the rapidity distributions for reactions of varying numbe[r]

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Centrality, rapidity, and transverse momentum dependence of isolated prompt photon production in lead-lead collisions at

Centrality, rapidity, and transverse momentum dependence of isolated prompt photon production in lead-lead collisions at

DOI: 10.1103/PhysRevC.93.034914 I. INTRODUCTION Prompt photons are an important probe for the study of the hot, dense matter formed in the high-energy collision of heavy ions. Being colorless, they are transparent to the subsequent evolution of the matter and probe the very initial stages of the collision. Their production rates are therefore expected to be directly sensitive to the overall thickness of the colliding nuclear matter. The rates are also expected to be sensitive to modifications of the partonic structure of nucleons bound in a nucleus, which are implemented as nuclear modifications [ 1 – 3 ] to the parton distribution functions (PDFs) measured in deep-inelastic lepton-proton and proton-proton (pp) scattering experiments. These effects include nuclear shadowing (the depletion of the parton densities at low Bjorken x), antishadowing (an enhancement at moderate x), and the EMC effect [ 4 ]. Photon rates are also sensitive to final-state interactions in the hot and dense medium, via the conversion of high-energy quarks and gluons into photons through rescattering. This is predicted to lead to an increased photon production rate relative to standard expectations [ 5 , 6 ]. Prompt photons have two primary sources. The first is direct emission, which proceeds at leading order via quark-gluon Compton scattering qg → qγ or quark-antiquark annihilation
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