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We present a study of the demographics of major conferences in heavy ion physics. We look at the distribution of talks by gender for Quark Matter, Strangeness in Quark Matter, Initial Stages, and Hard Probes between 2011–2022. We find that women are often underrepresented among plenary speakers and usually underrepresented among parallel speakers. At Quark Matter, women are more likely to be given a poster presentation in lieu of an oral presentation. The Quark Matter summary talk has never been given by a woman. We discuss the collection of data and possible approaches to make the field more equitable and, therefore, more scientifically productive.

In this work, we obtain the leading corrections to the jet momentum broadening distribution in a QCD medium arising from the transverse flow of the matter. We first derive the single-particle propagator of a highly energetic parton resumming its multiple interactions with the homogeneous flowing matter, explicitly keeping the leading subeikonal flow terms. Then, we use this propagator to obtain the jet broadening distribution and its leading moments. We show that this distribution becomes anisotropic in the presence of transverse flow, since its odd moments are generally non-zero and proportional to the transverse velocity of the medium. Finally, we evaluate several odd moments, which we compare to the corresponding results at first order in opacity, showing that accounting for multiple in-medium scatterings is essential to describe some observables in dense nuclear matter., Comment: 29 pages, 2 figures, v2: journal version, references added

New measurements of jet quenching observables at RHIC and at the LHC, such as jet substructure observables, demand an increased precision in the theory calculations describing medium-induced radiation of gluons. Closed expressions for the gluon spectrum including a full resummation of multiple scatterings have been known for the past 20 years. Still they have only been evaluated in specific limits either taking a few terms in an opacity expansion or by employing a Gaussian approximation for the interaction potential -- which misses essential physical effects. We present here a new flexible method to compute the full spectrum for a realistic interaction potential, thus allowing us for the first time to properly quantify the effect of the all-order resummation of multiple scatterings. This new approach paves the way for precision phenomenological studies including multiple scattering effects such as coherence phenomena., Proceedings of Hard Probes 2020

In this work we use the all-order resummed solution of the BDMPS-Z spectrum to shed light on the dynamics that controls the in-medium radiation process for each kinematical regime. We find that multiple scatterings are essential to correctly describe the radiation process both in the low and mid-energy regime, while in the high-energy region one single hard scattering is enough. Furthermore, we compute the all-order spectrum when the medium is produced with a time delay with respect to the hard process in which the parent parton was created. The propagation of the hard parton though vacuum before the medium formation induces extra medium-induced radiation which might have an impact on phenomenological analyses., Comment: Proceedings of PANIC2021

A proper understanding of the physics of medium-induced gluon emissions is known to be of critical importance to describe the properties of strongly interacting matter under extreme conditions. In this regard, many theoretical efforts have been directed towards obtaining analytical calculations which might help us discerning the underlying physical picture and the dominant dynamics for different regimes. These analytical approaches rely on approximations whose validity is analyzed here by comparing their results with a recently developed numerical evaluation which includes all-order resummation of multiple scatterings. More specifically, by quantitatively comparing the energy spectrum and rates, we observe that three different regimes -- each with its corresponding physical picture -- emerge naturally from the equations: the high-energy regime where the emission process is dominated by a single hard scattering, the intermediate-energy regime where coherence effects among multiple scatterings become fundamental, and the low-energy regime where the dynamics is again dominated by a single scattering but where one must include the suppression factor due to the probability of not having any further scatterings (which is obtained through the resummation of virtual terms)., Comment: 17 pages, 7 figures. New appendix. Matches published version in JHEP

In our analysis, we combine event-by-event hydrodynamics, within the EKRT formulation, with jet quenching -ASW Quenching Weights- to obtain high- p T R AA for charged particles at RHIC and LHC energies for different centralities. By defining a K -factor that quantifies the departure of q ˆ from an ideal estimate, K = q ˆ / ( 2 ϵ 3 / 4 ) , we fit the single-inclusive experimental data for charged particles. This K -factor is larger at RHIC than at the LHC but, surprisingly, it is almost independent of the centrality of the collision.

We present here an extraction of the jet transport coefficient, q, using RHIC and LHC single-inclusive high-pT data for different centralities. We fit a K-factor that determines the deviation of this coefficient from an ideal estimate, K ≡ q / ( 2 ϵ 3 / 4 ) , where ϵ is given by hydrodynamic simulations. As obtained already in previous studies, this K-factor is found to be larger at RHIC than at the LHC. However it is, unexpectedly, basically no-dependent on the centrality of the collision. Taken at face value this result, the K-factor would not depend on local properties of the QGP as temperature, but on global collision variables such as the center of mass energy.

Talk from the Strong QCD from Hadron Structure Experiments Workshop 2019

Extracting information about the quark and gluon (or parton) structure of the nucleon from high-energy scattering data is a classic example of the inverse problem: the experimental cross sections are given by convolutions of the parton probability distributions with process-dependent hard coefficients that are perturbatively calculable from QCD. While most analyses in the past have been based on the maximum likelihood approach, it is becoming evident that Bayesian likelihood methods using Monte Carlo (MC) sampling techniques are increasingly needed to thoroughly explore the parameter space associated with the quantum probability distributions. This talk will review the recent developments in the application of MC techniques to global QCD analyses, which are leading to a paradigm shift in the phenomenological study of partonic structure of the nucleon, including the first simultaneous global analysis of collinear parton distributions and parton to hadron fragmentation functions. Future applications to the study of the 3-dimensional structure of the nucleon, in terms of transverse momentum dependent parton distributions, will be outlined.

It is shown that the excellent scaling of the elliptic flow found for all centralities, species and energies from RHIC to the LHC for $p_{T}$ less than the saturation momentum is a consequence of the energy lost by a parton interacting with the color field produced in a nucleus-nucleus collision. In particular, the deduced shape of the scaling curve describes correctly all the data. We discuss the possible extensions to higher $p_{T}$, proton-nucleus and proton-proton collisions as well as higher harmonics., Comment: 10 pages, 2 figures

We present some of the features shown by RHIC and LHC data concerning high density, emphasizing the differences and similarities between the big bang and the little big bang. We briefly discuss multiplicity rapidity distributions, geometric scaling, saturation momentum of gluons, harmonic moments, and longrange rapidity correlations.

The central goal of jet quenching studies in high-energy nuclear collisions is the characterization of those QCD medium properties that are accessible by these probes. Most of the discussion in the last years has been focused on the determination of the jet quenching parameter, $\hat q$. We present here an extraction of this parameter using data of inclusive particle suppression at RHIC and LHC energies for different centralities. Our approach consists of fitting a $K$ factor that quantifies the departure of this parameter from an ideal estimate, $K\equiv \hat q/(2\epsilon^{3/4})$, where $\hat q$ is determined by the local medium quantities as provided by hydrodynamical calculations. We find that this $K$ factor is larger at RHIC than at the LHC, as obtained already in previous analyses, but, surprisingly, it is almost independent of the centrality of the collision. Taken at face value, the $K$ factor would not depend on the local properties of the medium as energy density or temperature, but on global collision quantities such as the center of mass energy. This is a very intriguing, unexpected possibility for which we cannot yet provide a clear interpretation. We also comment on the limitations of the formalism that may affect this conclusion., Comment: 26 pages, 7 figures

The presence of scaling variables in experimental observables provide very valuable indications of the dynamics underlying a given physical process. In the last years, the search for geometric scaling, that is the presence of a scaling variable which encodes all geometrical information of the collision as well as other external quantities as the total energy, has been very active. This is motivated, in part, for being one of the genuine predictions of the Color Glass Condensate formalism for saturation of partonic densities. Here we extend these previous findings to the case of experimental data on elliptic flow. We find an excellent scaling for all centralities and energies, from RHIC to LHC, with a simple generalization of the scaling previously found for other observables and systems. Interestingly the case of the photons, difficult to reconcile in most formalisms, nicely fit the scaling curve. We discuss the possible interpretations of this finding in terms of initial or final state effects., Comment: 6 pages, 4 figures, accepted for publication in Phys Rev C

It is shown that the anomalous sharp increasing of the strength of the near-side ridge structures observed in Au-Au collisions at $\sqrt{s}=62$ and $\sqrt{s}=200$ GeV and the onset of the ridge structure in $p\text{Pb}$ and in $pp$ collisions can be naturally explained in the framework of string percolation. In all the cases the near-side strength reflects the collision area covered by the strings stretched between the colliding objects and therefore it is related to the shape of their profile functions. The dependence of the pseudorapidity and azimuthal widths on multiplicity and energy is qualitatively explained.

It is shown that by defining a suitable saturation momentum Qs, the pT distributions of pp and AA collisions for any centrality and energy depend only on τ = pT2/Qs2 for pT < Qs. The corresponding τ-lines present small differences for τ < 1 for different projectiles, targets and centralities. For τ < 1, the higher the energy or the larger the size of the participant nuclei, the larger suppression the respective spectra present. The integrated spectrum gives a fraction of the hard multiplicity in the range from 9 % for pp at 0.9 TeV to 2 % for Pb-Pb central collisions at 2.76 TeV.

It is shown that defining a suitable saturation momentum $Q_s$, the $p_T$ distributions of pp and AA collisions for any centrality and energy depend only on $\tau=p^2_T/Q_s^2$ for $p_T1$, the higher the energy or the larger the size of the participant nuclei, the larger suppression present the respective spectra. The integrated spectrum gives a fraction of the hard multiplicity in the range from 9% for pp at 0.9 TeV to 2% for Pb-Pb central collisions at 2.76 TeV., Comment: 7 pages, 5 figures, 1 table

We present a phenomenological study of the single- and double-inclusive suppression data of high-pT particles in central Pb-Pb collisions at LHC. The analysis is based on quenching weights for medium-induced gluon radiation computed in the multiple soft scattering approximation and embedded in a hydrodynamic description of the bulk medium.

It is shown that the anomalous sharp increasing of the strength of the near-side ridge structures observed in Au-Au collisions at s = 62 GeV and s = 200 GeV and the onset of the ridge structure in pPb and in pp collisions can be naturally explained in the framework of string percolation. In all the cases the near-side strength reflects the collision area covered by the strings stretched between the colliding objects and therefore it is related to the shape of their profile functions. The dependence of the pseudorapidty and azimuthal widths on multiplicty and energy is qualitatively explained.

The nuclear modification factor $R_{\rm AA}$ has been satisfactorily described by various jet quenching models. Nonetheless, all these formalisms, until very recently, underpredicted the high-$p_{\rm T}$ (> 10 GeV) elliptic flow $v_2$. We find that the simultaneous description of these observables requires to strongly suppress the quenching for the first $\sim 0.6$ fm after the collision. This shows the potential of jet quenching observables to constrain the dynamics of the initial stages of the evolution., Proceedings of the Hard Probes 2018 conference. 4 pages. 2 figures

The new precision era of jet quenching observables at both RHIC and the LHC calls for an improved and more precise description of in-medium gluon emissions. The development of new theoretical tools and analytical calculations to tackle this challenge has been hampered by the inability to include the effects of multiple scatterings with the medium using a realistic model for the parton-medium interactions. In this paper, we show how the analytical expressions for the full in-medium spectrum, including the resummation of all multiple scatterings, can be written in a form where the numerical evaluation can be easily performed without the need of the usually employed harmonic or single hard approximations. We present the transverse momentum and energy-dependent medium-induced gluon emission distributions for known realistic interaction models to illustrate how our framework can be applied beyond the limited kinematic regions of previous calculations., 21 pages, 8 figures. Figure 5 corrected, new Figures 7 and 8, discussion improved, and new appendix B. Matches published JHEP version