The method of Q-cumulants is a powerful tool for studying the fine details of azimuthal anisotropies in high energy nuclear collisions.This paper presents a new method,based on mathematical induction,to evaluate the a...The method of Q-cumulants is a powerful tool for studying the fine details of azimuthal anisotropies in high energy nuclear collisions.This paper presents a new method,based on mathematical induction,to evaluate the analytical form of high-order Q-cumulants.The capability of this method is demonstrated via a toy model that uses the elliptic power distribution to simulate the anisotropic emission of particles,quantified in terms of Fourier flow harmonics v_(n).The method can help in studying the large amount of event statistics that can be collected in the future and allow measurements of the very high central moments of the v_(2)distribution.This can,in turn,facilitate progress in understanding the initial geometry,the input to the hydrodynamic calculations of medium expansion in high energy nuclear collisions,and the constraints on it.展开更多
Recent LHC results on the appearance of sub-leading flow modes in Pb Pb collisions at 2.76 TeV, related to initial-state fluctuations, are analyzed and interpreted within the HYDJET++ model. Using the newly introduc...Recent LHC results on the appearance of sub-leading flow modes in Pb Pb collisions at 2.76 TeV, related to initial-state fluctuations, are analyzed and interpreted within the HYDJET++ model. Using the newly introduced Principal Component Analysis(PCA) method applied to two-particle azimuthal correlations extracted from the model calculations, the leading and sub-leading flow modes are studied as a function of the transverse momentum(p T) over a wide centrality range. The leading modes of the elliptic(v2^(1)) and triangular(v3^(1)) flow calculated with the HYDJET++ model reproduce rather well the v2 {2} and v3 {2} coefficients measured experimentally using the two-particle correlations. Within the p T 3 Ge V/c range, where hydrodynamics dominates, the sub-leading flow effects are greatest at the highest p T of around 3 Ge V/c. The sub-leading elliptic flow mode(v2^(2)), which corresponds to the n = 2 harmonic, has a small non-zero value and slowly increases from central to peripheral collisions, while the sub-leading triangular flow mode(v3^(2)), which corresponds to the n = 3 harmonic, is even smaller and does not depend on centrality. For n= 2, the relative magnitude of the effect measured with respect to the leading flow mode shows a shallow minimum for semi-central collisions and increases for very central and for peripheral collisions. For the n= 3 case, there is no centrality dependence. The sub-leading flow mode results obtained from the HYDJET++model are in rather good agreement with the experimental measurements of the CMS Collaboration.展开更多
基金the Ministry of Education Science and Technological Development,Republic of Serbia,the National Natural Science Foundation of China(12035006,12075085,12147219)the U.S.Department of Energy(de-sc0012910).
文摘The method of Q-cumulants is a powerful tool for studying the fine details of azimuthal anisotropies in high energy nuclear collisions.This paper presents a new method,based on mathematical induction,to evaluate the analytical form of high-order Q-cumulants.The capability of this method is demonstrated via a toy model that uses the elliptic power distribution to simulate the anisotropic emission of particles,quantified in terms of Fourier flow harmonics v_(n).The method can help in studying the large amount of event statistics that can be collected in the future and allow measurements of the very high central moments of the v_(2)distribution.This can,in turn,facilitate progress in understanding the initial geometry,the input to the hydrodynamic calculations of medium expansion in high energy nuclear collisions,and the constraints on it.
基金Supported by Ministry of Education,Science and Technological Development of the Republic of Serbia(171019)
文摘Recent LHC results on the appearance of sub-leading flow modes in Pb Pb collisions at 2.76 TeV, related to initial-state fluctuations, are analyzed and interpreted within the HYDJET++ model. Using the newly introduced Principal Component Analysis(PCA) method applied to two-particle azimuthal correlations extracted from the model calculations, the leading and sub-leading flow modes are studied as a function of the transverse momentum(p T) over a wide centrality range. The leading modes of the elliptic(v2^(1)) and triangular(v3^(1)) flow calculated with the HYDJET++ model reproduce rather well the v2 {2} and v3 {2} coefficients measured experimentally using the two-particle correlations. Within the p T 3 Ge V/c range, where hydrodynamics dominates, the sub-leading flow effects are greatest at the highest p T of around 3 Ge V/c. The sub-leading elliptic flow mode(v2^(2)), which corresponds to the n = 2 harmonic, has a small non-zero value and slowly increases from central to peripheral collisions, while the sub-leading triangular flow mode(v3^(2)), which corresponds to the n = 3 harmonic, is even smaller and does not depend on centrality. For n= 2, the relative magnitude of the effect measured with respect to the leading flow mode shows a shallow minimum for semi-central collisions and increases for very central and for peripheral collisions. For the n= 3 case, there is no centrality dependence. The sub-leading flow mode results obtained from the HYDJET++model are in rather good agreement with the experimental measurements of the CMS Collaboration.