Initial-state fluctuations in collisions between light and heavy ions

Welsh, Kevin; Singer, Jordan; Heinz, Ulrich

doi:10.1103/physrevc.94.024919

Cited by 70 publications

(84 citation statements)

References 88 publications

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“…1-2, within wounded quark models. These studies lead to the correct negative sign of SC(2,3) at high multiplicities but the magnitude is off [18][19][20]. Also without hydrodynamic evolution, qualitative agreement with the p+Pb results has been achieved in an initial state model where the partons in the projectile coherently scatter off the color fields in the heavy nuclear target [21,22].…”

Section: Introductionmentioning

confidence: 93%

Symmetric cumulants as a probe of the proton substructure at LHC energies

2018

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We present a systematic study of the normalized symmetric cumulants, NSC(n,m), at the eccentricity level in proton-proton interactions at √ s = 13 TeV within a wounded hot spot approach. We focus our attention on the influence of spatial correlations between the proton constituents, in our case gluonic hot spots, on this observable. We notice that the presence of short-range repulsive correlations between the hot spots systematically decreases the values of NSC(2,3) and NSC(2,4) in midto ultra-central collisions while increases them in peripheral interactions. In the case of NSC(2,3) we find that, as suggested by data, an anti-correlation of ε2 and ε3 in ultra-central collisions, i.e. NSC(2,3) < 0, is possible within the correlated scenario while it never occurs without correlations when the number of gluonic hot spots is set to three. We attribute this fact to the decisive role of correlations on enlarging the probability of interaction topologies that reduce the value of NSC(2,3) and, eventually, make it negative. Further, we explore the dependence of our conclusions on the number of hot spots, the values of the hot spot radius and the repulsive core distance. Our results add evidence to the idea that considering spatial correlations between the subnucleonic degrees of freedom of the proton may have a strong impact on the initial state properties of proton-proton interactions [1].

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Section: Introductionmentioning

confidence: 93%

Symmetric cumulants as a probe of the proton substructure at LHC energies

2018

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“…Quantitative hydrodynamic predictions of azimuthal correlations in pp and pPb systems still have large uncertainties, mainly due to limited knowledge of initial-state fluctuations of energy deposition at sub-nucleonic scales [35][36][37]. Detailed modeling of initial-state fluctuations in pp and pPb collisions [38] can be further constrained by the study of v n coefficient correlations. For example, a positive correlation between v 2 and v 3 is predicted in pp collisions over the full multiplicity range [38], the opposite to what is observed in PbPb collisions [18].…”

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confidence: 99%

“…Detailed modeling of initial-state fluctuations in pp and pPb collisions [38] can be further constrained by the study of v n coefficient correlations. For example, a positive correlation between v 2 and v 3 is predicted in pp collisions over the full multiplicity range [38], the opposite to what is observed in PbPb collisions [18]. Measuring v n correlations in small colliding systems will help to understand if a common paradigm to describe collectivity in all hadronic systems can be found.This Letter presents high precision measurements of anisotropy coefficients v 4 in pp at √ s = 13 TeV, pPb at √ s NN = 8.16 TeV, and PbPb at √ s NN = 5.02 TeV using data from the CMS experiment.…”

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confidence: 99%

Observation of Correlated Azimuthal Anisotropy Fourier Harmonics in pp and p+Pb Collisions at the LHC

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2018

Phys. Rev. Lett.

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The azimuthal anisotropy Fourier coefficients (v n ) in 8.16 TeV pPb data are extracted via long-range two-particle correlations as a function of event multiplicity and compared to corresponding results in pp and PbPb collisions. Using a four-particle cumulant technique, v n correlations are measured for the first time in pp and pPb collisions. The v 2 and v 4 coefficients are found to be positively correlated in all collision systems. For high multiplicity pPb collisions an anticorrelation of v 2 and v 3 is observed, with a similar correlation strength as in PbPb data at the same multiplicity. The new correlation results strengthen the case for a common origin of the collectivity seen in pPb and PbPb collisions in the measured multiplicity range.

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“…We note that the focus of this paper has been on small scale structure in large PbPb collisions. Recently, it has been shown that small systems such as pPb and pp may provide more clues about small scale structure [35,[81][82][83][84]. We leave a deeper study on small systems for a later work.…”

Section: Discussionmentioning

confidence: 99%

Sensitivity of observables to coarse-graining size in heavy-ion collisions

et al. 2018

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An open question in the field of heavy-ion collisions is to what extent the size of initial inhomogeneities in the system affects measured observables. Here we present a method to smooth out these inhomogeneities with minimal effect on global properties, in order to quantify the effect of shortrange features of the initial state. We show a comparison of hydrodynamic predictions with original and smoothened initial conditions for four models of initial conditions and various observables. Integrated observables (integrated vn, scaled vn distributions, normalized symmetric cumulants, event-plane correlations) as well as most differential observables (vn(pT )) show little dependence on the inhomogeneity sizes, and instead are sensitive only to the largest-scale geometric structure. However other differential observables such as the flow factorization ratio and sub-leading principal components are more sensitive to the granularity and could be a good tool to probe the short-scale dynamics of the initial stages of a heavy-ion collision, which are not currently well understood.

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Initial-state fluctuations in collisions between light and heavy ions

Cited by 70 publications

References 88 publications

Symmetric cumulants as a probe of the proton substructure at LHC energies

Symmetric cumulants as a probe of the proton substructure at LHC energies

Observation of Correlated Azimuthal Anisotropy Fourier Harmonics in pp and p+Pb Collisions at the LHC

Sensitivity of observables to coarse-graining size in heavy-ion collisions

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