Anisotropic flow from Lee–Yang zeros: a practical guide

Borghini, Nicolas; Bhalerao, Rajeev S.; Ollitrault, Jean-Yves

doi:10.1088/0954-3899/30/8/092

Cited by 46 publications

(57 citation statements)

References 11 publications

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“…To further investigate the multiparticle nature of the observed long-range correlations, we present measurements for pPb collisions at √ s NN = 5.02 TeV of multiparticle correlations using six-and eight-particle cumulant methods [17,18] and also results based on the Lee-Yang Zeros (LYZ) method [19,20] involving correlations among all particles. The pPb data are obtained by the CMS experiment during the 2013 pPb run at the LHC.…”

Section: Introductionmentioning

confidence: 99%

Azimuthal anisotropy of charged particles from multiparticle correlations in pPb and PbPb collisions with CMS

Wang

2014

Nuclear Physics A

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Motivated by two-and four-particle azimuthal correlation measurements that suggest possible collective flow for charged particles emitted in pPb collisions at √ s N N =5.02 TeV, we extend the correlation results for these collisions using the six-and eight-particle cumulant methods, and the Lee-Yang Zeros method. CMS has an extensive program studying azimuthal harmonic coefficients for both PbPb and pPb collisions using various methods. The current pPb results will be presented in this context. The data were collected by the CMS experiment at the LHC using both minimum bias and highmultiplicity collision triggers over a wide range in pseudorapidity. The results are compared to 2.76 TeV semi-peripheral PbPb collision data collected in 2011 covering a similar range of particle multiplicities. The second-order azimuthal anisotropy Fourier harmonic (v 2 ) is shown for the different methods. A comparison of the six-and greater particle correlations to the previously published twoand four-particle correlation results sheds light on the multiparticle nature of the azimuthal anisotropy. The results are also discussed in terms of recent calculations that explore the role of participant fluctuations on measurements of higher-order particle correlations in pPb collisions. AbstractMotivated by two-and four-particle azimuthal correlation measurements that suggest possible collective flow for charged particles emitted in pPb collisions at √ s NN = 5.02 TeV, we extend the correlation results for these collisions using the six-and eight-particle cumulant methods, and the Lee-Yang Zeros method. CMS has an extensive program studying azimuthal harmonic coefficients for both PbPb and pPb collisions using various methods. The current pPb results will be presented in this context. The data were collected by the CMS experiment at the LHC using both minimum bias and high-multiplicity collision triggers over a wide range in pseudorapidity. The results are compared to 2.76 TeV semi-peripheral PbPb collision data collected in 2011 covering a similar range of particle multiplicities. The second-order azimuthal anisotropy Fourier harmonic (v 2 ) is shown for the different methods. A comparison of the six-and greater particle correlations to the previously published two-and four-particle correlation results sheds light on the multiparticle nature of the azimuthal anisotropy. The results are also discussed in terms of recent calculations that explore the role of participant fluctuations on measurements of higher-order particle correlations in pPb collisions.

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Section: Introductionmentioning

confidence: 99%

Azimuthal anisotropy of charged particles from multiparticle correlations in pPb and PbPb collisions with CMS

Wang

2014

Nuclear Physics A

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“…A first possibility is to start from already existing models of correlations, which make predictions for definite quantities, and to try to deal with the pair-flow observables so as to relate them to these quantities. This was attempted in reference [4], where we showed how to use the two-particle flow observables to recover previously-used quantities in models of quantum correlations [6] or high-p T jet-like correlations [7]. The second approach consists in predicting directly the values of the pair-flow coefficients v pair c,n and v pair s,n within the framework of given models, relating their behaviour to the various parameters of the models.…”

Section: Summary and Applicationsmentioning

confidence: 99%

“…Beyond that, two arbitrary particles may also be correlated, for various reasons: a) they may be the decay products of a short-lived particle that decays before reaching the detectors, or b) they may both belong to a (di)jet originating from a hard parton scattering, or c) they may be identical particles whose wave-functions interfere. Whatever the physical mechanism involved, the resulting two-particle correlation will depend on the azimuths of the particles if the short-lived parent particles flow (case a), or because the anisotropy of the interacting region results in anisotropic patterns of parton energy loss [2] (case b) and interferometry [3] (case c).The purpose of this paper is to present model-independent observables that characterize in a general way azimuthally-sensitive two-particle correlations, without any prejudice on the underlying physical mechanism [4]. We then discuss the experimental measurement of these observables, i.e., the measurement of the particlepair distribution with respect to the reaction plane.…”

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confidence: 99%

“…The purpose of this paper is to present model-independent observables that characterize in a general way azimuthally-sensitive two-particle correlations, without any prejudice on the underlying physical mechanism [4]. We then discuss the experimental measurement of these observables, i.e., the measurement of the particlepair distribution with respect to the reaction plane.…”

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Characterization and analysis of azimuthally sensitive correlations

Borghini

2005

J. Phys. G: Nucl. Part. Phys.

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Abstract. A unified framework for describing the azimuthal dependence of two-particle correlations in heavy-ion collisions is introduced, together with the methods for measuring the corresponding observables. The generalization to azimuthal correlations between more than two particles is presented.The high amount of data that modern nucleus-nucleus experiments can accumulate allow novel types of measurements, giving new information on the physics involved. An emerging class of experimental analyses thus consists in studying the dependence in azimuth of various observables in non-central collisions, investigating correlations with the impact-parameter direction.A celebrated example of such a correlation with the reaction plane is the azimuthal dependence of single-particle emission, the so-called (one-particle) anisotropic flow (for a review, see [1]). In the following, we shall focus on the dependence with the azimuth of two-particle production. If the single-particle production is azimuthally dependent, the two-particle production depends on the azimuth as well. Beyond that, two arbitrary particles may also be correlated, for various reasons: a) they may be the decay products of a short-lived particle that decays before reaching the detectors, or b) they may both belong to a (di)jet originating from a hard parton scattering, or c) they may be identical particles whose wave-functions interfere. Whatever the physical mechanism involved, the resulting two-particle correlation will depend on the azimuths of the particles if the short-lived parent particles flow (case a), or because the anisotropy of the interacting region results in anisotropic patterns of parton energy loss [2] (case b) and interferometry [3] (case c).The purpose of this paper is to present model-independent observables that characterize in a general way azimuthally-sensitive two-particle correlations, without any prejudice on the underlying physical mechanism [4]. We then discuss the experimental measurement of these observables, i.e., the measurement of the particlepair distribution with respect to the reaction plane. In particular, we shall mention methods of analysis that do not require to estimate the reaction plane, in opposition to those currently used [5][6][7]. Finally, we comment on the last step of the analysis, namely relating the observables we propose to models of the two-particle correlations. Quite obviously, that procedure is model-dependent, and we shall present several possible ways to tackle the issue. We shall conclude by generalizing the overall approach to correlations between more than two particles.

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“…One of main features of Quark Gluon Plasma is its hydrodynamic behavior characterized by v n coefficients extracted using methods like two-and many-particle correlations [1], the scalar product (SP) [2,3] and the Lee-Yang Zero (LYZ) [4,5]. The CMS collaboration measured v 2 coefficient in PbPb collisions over a wide p T range up to 100 GeV/c [6].…”

Section: Introductionmentioning

confidence: 99%

Azimuthal anisotropies and initial-state fluctuations from SPS to LHC energies

Milošević

2017

EPJ Web Conf.

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Abstract. The v 3 coefficient, obtained using the PbAu data from the CERES detector at the top SPS energy of √ s NN = 17.3 GeV, is presented. The v 2 is measured over a p T range up to 100 GeV/c in PbPb collisions collected with the CMS detector. The v 2 {2} of charged and strange particles emitted in pp collisions shows a mass ordering effect. The v 2 {4} and v 2 {6} are comparable to the v 2 {2}, and thus supports the collective nature of the long-range correlations in high-multiplicity pp collisions at 13 TeV. Principle Component Analysis (PCA) of two-particle harmonics (V nΔ ) is studied in PbPb and high-multiplicity pPb collisions at the LHC. The factorization breaking of the V nΔ can be attributed to the effect of initial-state fluctuations. Using a PCA, the V nΔ are characterized through the leading and sub-leading modes. The leading modes are essentially equivalent to the v n {2}. The sub-leading modes represent the largest sources of factorization breaking.

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Anisotropic flow from Lee–Yang zeros: a practical guide

Abstract: Abstract. We present a new method to analyze anisotropic flow from the genuine correlation among a large number of particles, focusing on the practical implementation of the method.

Cited by 46 publications

References 11 publications

Azimuthal anisotropy of charged particles from multiparticle correlations in pPb and PbPb collisions with CMS

Azimuthal anisotropy of charged particles from multiparticle correlations in pPb and PbPb collisions with CMS

Characterization and analysis of azimuthally sensitive correlations

Azimuthal anisotropies and initial-state fluctuations from SPS to LHC energies

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