Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFactorization breaking for higher moments of harmonic flow
173
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We study correlations between the harmonic flow vectors squared measured at different transverse momenta. One of the flow harmonics squared is taken at a fixed transverse momentum and correlated to the momentum averaged harmonic flow squared of the same order. Such four particle correlators, dependent on transverse momentum, have been recently measured experimentally. The correlation based on four-particle correlators allows the independent measurement of the flow vector and flow magnitude correlation coefficient. Also, the correlation of the harmonic flow angles as a function of transverse momentum can be extracted. Results are compared to the preliminary data of the ALICE Collaboration. We also present the predictions for the momentum dependent correlation coefficient between mixed flow harmonics. The correlations between squares of mixed harmonics can serve as a way to independently measure the flow vector, flow magnitude, and flow angle correlations, and could be used to gain additional information on the fluctuating initial state and the dynamics in heavy-ion collisions.
rate research
Read More
Higher order symmetric cumulants of global collective observables in heavy ion collisions are studied. The symmetric cumulants can be straightforwardly constructed for scalar observables: the average transverse momentum, the multiplicity, and the squares of harmonic flow vectors. Third and fourth order cumulants are calculated in the hydrodynamic model. A linear predictor of the average transverse momentum and harmonic flow coefficients in a collision is used to predict the value of the cumulants from the moments of the initial distribution. The symmetric cumulants divided by the averages (or the standard deviations) of the considered observables can be used as a fine tool to study correlations present in the initial state of the collision.
The collective harmonic flow in heavy-ion collisions correlates particles at all transverse momenta to be emitted preferably some directions. The factorization breaking coefficient measures the small decorrelation of the flow harmonics at two different transverse momenta. Using the hydrodynamic model I study in details the decorrelation of the harmonic flow due to the flow angle and the flow magnitude decorrelation at two transverse momenta. The effect can be seen in experiment measuring factorization breaking coefficients for the square of the harmonic flow vector at two transverse momenta. The hydrodynamic model predicts that the decorrelation of the flow magnitudes is about one half of the decorrelation of the overall flow (combining flow angle and flow magnitude decorrelations). These results are consistent with the principal component analysis of correlators of flow vectors squared.
The dynamical development of expanding Quark-gluon Plasma (QGP) flow is studied in a 3+1D fluid dynamical model with a globally symmetric, initial condition. We minimize fluctuations arising from complex dynamical processes at finite impact parameters and from fluctuating random initial conditions to have a conservative fluid dynamical background estimate for the statistical distributions of the thermodynamical parameters. We also avoid a phase transition in the equation of state, and we let the matter supercool during the expansion. Then central Pb+Pb collisions at $sqrt{s_{NN}} = 2.76$ TeV are studied in an almost perfect fluid dynamical model, with azimuthally symmetric initial state generated in a dynamical flux-tube model. The general development of thermodynamical extensives are also shown for lower energies. We observe considerable deviations from a thermal equilibrium source as a consequence of the fluid dynamical expansion arising from a least fluctuating initial state.
The correlation between the harmonic flow and the transverse flow in relativistic heavy ion collisions is calculated in the hydrodynamic model. The partial correlation coefficient, corrected for fluctuations of multiplicity, is compared to experimental data. Estimators of the final transverse and harmonic flow are used to predict the value of the correlation coefficient from the moments of the initial distribution. A good description of the hydrodynamic simulation results is obtained if the estimator for the final transverse flow, besides the most important transverse size and entropy, includes also the eccentricities.
The directed flow of particles produced in ultrarelativistic heavy ion collisions at SPS and RHIC is so small that currently available methods of analysis are at the border of applicability. Standard two-particle and flow-vector methods are biased by large nonflow correlations. On the other hand, cumulants of four-particle correlations, which are free from this bias, are plagued by large statistical errors. Here, we present a new method based on three-particle correlations, which uses the property that elliptic flow is large at these energies. This method may also be useful at intermediate energies, near the balance energy where directed flow vanishes.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
