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Since their discovery, fluctuations in the initial state of heavy-ion collisions have been understood as originating mostly from the random positions of nucleons within the colliding nuclei. We consider an alternative approach where all the…

We determine the uncorrelated modes that characterize the fluctuations in a semi-realistic model for the initial state of high-energy nuclear collisions, consisting of hot spots whose positions are distributed independently. Varying the…

Nuclear Theory · Physics 2025-01-14 Nicolas Borghini , Hendrik Roch , Alicia Schütte

We present a number of independent flow observables that can be measured using multiparticle azimuthal correlations in heavy-ion collisions. Some of these observables are already well known, such as v2{2} and v2{4}, but most are new--in…

Nuclear Theory · Physics 2012-06-18 Rajeev S. Bhalerao , Matthew Luzum , Jean-Yves Ollitrault

Elliptic flow, $v_2$, and triangular flow, $v_3$, are to a good approximation linearly proportional to the corresponding spatial anisotropies of the initial density profile, $\varepsilon_2$ and $\varepsilon_3$. Using event-by-event…

Nuclear Theory · Physics 2017-05-25 Giuliano Giacalone , Jacquelyn Noronha-Hostler , Jean-Yves Ollitrault

We discuss limiting fragmentation within a few currently popular phenomenological models. We show that popular Glauber-inspired models of particle production in heavy ion collisions, such as the two-component model, generally fail to…

Nuclear Theory · Physics 2019-11-13 Kayman J. Gonçalves , Andre V. Giannini , David D. Chinellato , Giorgio Torrieri

The initial conditions in heavy-ion collisions are calculated in many different frameworks. The importance of nucleon position fluctuations within the nucleus and sub-nucleon structure has been established when modeling initial conditions…

Nuclear Theory · Physics 2021-02-17 R. Snyder , M. Byres , S. H. Lim , J. L. Nagle

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…

Fluctuations in the initial QCD matter density distribution are found to enhance the production of thermal photons significantly in the range 2 \leq pT \leq 4 GeV/c compared to a smooth initial state averaged profile in ideal hydrodynamic…

Nuclear Theory · Physics 2015-06-04 Rupa Chatterjee , Hannu Holopainen , Thorsten Renk , Kari J. Eskola

Large spatial density fluctuations in high-energy heavy-ion collisions can come from many sources: initial transverse density fluctuations, non-central collisions, phase transitions, surface tension, and fragmentations. The common presence…

High Energy Physics - Phenomenology · Physics 2008-11-26 Cheuk-Yin Wong , Wei-Ning Zhang

This Letter reports on the first measurements of transverse momentum dependent flow angle $\Psi_n$ and flow magnitude $v_n$ fluctuations, determined using new four-particle correlators. The measurements are performed for various…

Nuclear Experiment · Physics 2023-06-22 ALICE Collaboration

The understanding of heavy ion collisions and its quark-gluon plasma formation requires a complicated interplay of rich physics in a wealth of experimental data. In this work we compare for identified particles the transverse momentum…

Nuclear Theory · Physics 2021-05-26 Govert Nijs , Wilke van der Schee , Umut Gürsoy , Raimond Snellings

We briefly review advances in understanding the initial stages of a heavy ion collision. In particular the focus is on moving from parametrizing the initial state to calculating its properties from QCD, consistently with the description of…

High Energy Physics - Phenomenology · Physics 2015-09-16 T. Lappi

The fluid-dynamical modeling of a nuclear collision at high energy usually starts shortly after the collision. A major source of uncertainty comes from the detailed modeling of the initial state. While the collision itself likely involves…

Nuclear Theory · Physics 2025-04-16 Andreas Kirchner , Federica Capellino , Eduardo Grossi , Stefan Floerchinger

We analyze measures of the azimuthal asymmetry, in particular the participant harmonic moments, epsilon*, in a variety of Glauber-like models for the early stage of collisions at RHIC. Quantitative comparisons indicate substantial model…

Nuclear Theory · Physics 2008-12-18 Wojciech Broniowski , Piotr Bozek , Maciej Rybczynski

Fluctuation and correlation observables are often measured using multi-particle correlation methods and therefore mutually probe the origins of genuine correlations present in multi-particle distribution functions. We investigate the common…

Nuclear Theory · Physics 2015-06-11 Sean Gavin , George Moschelli

A current goal of relativistic heavy ion collisions experiments is the search for a Color Glass Condensate as the limiting state of QCD matter at very high density. In viscous hydrodynamics simulations, a standard Glauber initial condition…

Nuclear Theory · Physics 2015-06-15 M. Ruggieri , F. Scardina , S. Plumari , V. Greco

A comparison is made between results obtained using smooth initial conditions and event-by-event initial conditions in the hydrodynamical description of relativistic nuclear collisions. Some new results on directed flow are also included.

One important challenge in our field is to understand the initial condition of the QGP and constrain it using sensitive experimental observables. Recent studies show that the Pearson Correlation Coefficient between ${\bm V}_n$ and…

Nuclear Experiment · Physics 2022-10-04 Somadutta Bhatta

The Color Glass Condensate is an effective theory description for the small momentum fraction x degrees of freedom in a high energy hadron or nucleus, which can be understood in terms of strong classical gluon fields. We discuss the…

High Energy Physics - Phenomenology · Physics 2009-10-02 T. Lappi

A key ingredient of hydrodynamical modeling of relativistic heavy ion collisions is thermal initial conditions, an input that is the consequence of a pre-thermal dynamics which is not completely understood yet. In the paper we employ a…

Nuclear Theory · Physics 2015-01-22 V. Yu. Naboka , S. V. Akkelin , Iu. A. Karpenko , Yu. M. Sinyukov