Search results for "elliptic flow"
showing 10 items of 111 documents
Thermal photon v3 at LHC from fluctuating initial conditions
2014
Abstract We calculate the triangular flow parameter v 3 of thermal photons for 0–40% central collisions of Pb nuclei at LHC using an event-by-event hydrodynamic model with fluctuating initial conditions. Thermal photon v 3 with respect to the participant plane angle is found to be positive and significant compared to the elliptic flow parameter v 2 of thermal photons. In addition, photon v 3 as a function of p T shows similar qualitative nature to photon v 2 in the region 1 p T 6 GeV / c . We argue that while v 3 originates from ϵ 3 deformations of the initial state density distribution, fast buildup of radial flow due to fluctuations is the main driving mechanism for the observed large val…
Hydrodynamic simulation of elliptic flow
1999
We use a hydrodynamic model to study the space-time evolution transverse to the beam direction in ultrarelativistic heavy-ion collisions with nonzero impact parameters. We focus on the influence of early pressure on the development of radial and elliptic flow. We show that at high energies elliptic flow is generated only during the initial stages of the expansion while radial flow continues to grow until freeze-out. Quantitative comparisons with SPS data from semiperipheral Pb+Pb collisions suggest the applicability of hydrodynamical concepts already $\approx$ 1 fm/c after impact.
Evolution of fluctuations in the initial state of heavy-ion collisions from RHIC to LHC
2019
Fluctuations in the initial state of heavy-ion collisions are larger at RHIC energy than at LHC energy. This fact can be inferred from recent measurements of the fluctuations of the particle multiplicities and of elliptic flow performed at the two different energies. We show that an analytical description of the initial energy-density field and its fluctuations motivated by the color glass condensate (CGC) effective theory predicts and quantitatively captures the measured energy evolution of these observables. The crucial feature is that fluctuations in the CGC scale like the inverse of the saturation scale of the nuclei.
Measurement of the azimuthal anisotropy for charged particle production insNN=2.76TeV lead-lead collisions with the ATLAS detector
2012
Differential measurements of charged particle azimuthal anisotropy are presented for lead-lead collisions at root sNN = 2.76 TeV with the ATLAS detector at the LHC, based on an integrated luminosity of approximately 8 mu b(-1). This anisotropy is characterized via a Fourier expansion of the distribution of charged particles in azimuthal angle relative to the reaction plane, with the coefficients v(n) denoting the magnitude of the anisotropy. Significant v(2)-v(6) values are obtained as a function of transverse momentum (0.5 = 3 are found to vary weakly with both eta and centrality, and their p(T) dependencies are found to follow an approximate scaling relation, v(n)(1/n)(p(T)) proportional …
Energy loss in a fluctuating hydrodynamical background
2011
Recently it has become apparent that event-by-event fluctuations in the initial state of hydrodynamical modelling of ultrarelativistic heavy-ion collisions are crucial in order to understand the full centrality dependence of the elliptic flow coefficient v_2. In particular, in central collisions the density fluctuations play a major role in generating the spatial eccentricity in the initial state. This raises the question to what degree high P_T physics, in particular leading-parton energy loss, which takes place in the background of an evolving medium, is sensitive to the presence of the event-by-event density fluctuations in the background. In this work, we report results for the effects …
Elliptic flow from event-by-event hydrodynamics with fluctuating initial state
2011
We develop an event-by-event ideal hydrodynamical framework where initial state density fluctuations are present and where we use a similar flow-analysis method as in the experiments to make a one-to-one $v_2$ comparison with the measured data. Our studies also show that the participant plane is quite a good approximation for the event plane.
Measurement of the (anti-)3He elliptic flow in Pb–Pb collisions at sNN=5.02TeV
2020
The elliptic flow ( v 2 ) of (anti-) 3He is measured in Pb–Pb collisions at s NN = 5.02 TeV in the transverse-momentum ( p T ) range of 2–6 GeV/c for the centrality classes 0–20%, 20–40%, and 40–60% using the event-plane method. This measurement is compared to that of pions, kaons, and protons at the same center-of-mass energy. A clear mass ordering is observed at low p T , as expected from relativistic hydrodynamics. The violation of the scaling of v 2 with the number of constituent quarks at low p T , already observed for identified hadrons and deuterons at LHC energies, is confirmed also for (anti-) 3He. The elliptic flow of (anti-) 3He is underestimated by the Blast-Wave model and overe…
Measurement of deuteron spectra and elliptic flow in Pb–Pb collisions at √sNN = 2.76 TeV at the LHC
2017
The transverse momentum (pT) spectra and elliptic flow coefficient (v2) of deuterons and anti-deuterons at mid-rapidity (|y| 1.8 GeV/c within the experimental uncertainties. The measurement of the coalescence parameter B2 is performed, showing a pT dependence in contrast with the simplest coalescence model, which fails to reproduce also the measured v2 coefficient. In addition, the coalescence parameter B2 and the elliptic flow coefficient in the 20–40% centrality interval are compared with the AMPT model which is able, in its version without string melting, to reproduce the measured v2(pT) and the B2(pT) trend. peerReviewed
J/ψElliptic Flow in Pb-Pb Collisions atsNN=2.76 TeV
2013
We report on the first measurement of inclusive J/psi elliptic flow v(2) in heavy-ion collisions at the LHC. The measurement is performed with the ALICE detector in Pb-Pb collisions at root s(NN) = 2.76 TeV in the rapidity range 2.5 < y < 4.0. The dependence of the J/psi v(2) on the collision centrality and on the J/psi transverse momentum is studied in the range 0 <= p(T) < 10 GeV/c. For semicentral Pb-Pb collisions at root s(NN) = 2.76 TeV, an indication of nonzero v(2) is observed with a largest measured value of v(2) = 0.116 +/-0.046(stat) +/- 0.029(syst) for J/psi in the transverse momentum range 2 <= p(T) < 4 GeV/c. The elliptic flow measurement complements the previously reported ALI…
Correlated gluonic hot spots meet symmetric cumulants data at LHC energies
2019
We present a systematic study on the influence of spatial correlations between the proton constituents, in our case gluonic hot spots, their size and their number on the symmetric cumulant SC(2, 3), at the eccentricity level, within a Monte Carlo Glauber framework [1]. When modeling the proton as composed by 3 gluonic hot spots, the most common assumption in the literature, we find that the inclusion of spatial correlations is indispensable to reproduce the negative sign of SC(2, 3) in the highest centrality bins as dictated by data. Further, the subtle interplay between the different scales of the problem is discussed. To conclude, the possibility of feeding a 2+1D viscous hydrodynamic sim…