arXiv subjects

Cesar A. Bernardes

Publications and source records attributed to Cesar A. Bernardes.

7 recordsLinked to original sources

arXiv2026

Study of the thermodynamic properties of hot QCD matter with the CMS experiment

These proceedings summarize recent CMS measurements at the LHC that extract the squared speed of sound, $c_s^2$, of strongly interacting matter at extreme temperatures from the multiplicity dependence of the mean transverse momentum in ultra-central lead-lead (PbPb) collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02\ \mathrm{TeV}$. The analysis yields $c_s^2 = 0.241 \pm 0.002\, (\mathrm{stat}) \pm 0.016\, (\mathrm{syst})$ at an effective temperature of $T_{\mathrm{eff}} = 219 \pm 8\, (\mathrm{syst})\,\mathrm{MeV}$, in good agreement with lattice-QCD calculations. Complementary studies in proton-lead (pPb) collisions are also presented to investigate possible quark-gluon plasma signatures in smaller systems.

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arXiv2026

Nonflow suppression in flow analysis with a maximum likelihood estimator

We show that the maximum likelihood estimator (MLE) is an effective tool for mitigating non-flow effects in flow analysis. To this end, one constructs two toy models that simulate non-flow contributions corresponding to particle decay and momentum conservation, respectively. The performance of MLE is analyzed by comparing it against standard approaches such as particle correlation and event plane methods. For both cases, MLE is observed to provide a reasonable estimate of the underlying flow harmonics, and in particular, its performance can be further improved when the specific form of the likelihood in the presence of non-flow can be assessed. The dependencies of extracted flow harmonics on the multiplicity of individual events and the total number of events are analyzed. Additionally, it is shown that the proposed approach performs efficiently in addressing deficiencies in detector acceptance. These findings suggest MLE as a compelling alternative to standard methods for flow analysis.

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arXiv2026

Study of Collective Phenomena in Heavy-Ion Collisions Using CMS Open Data

In this work, we present preliminary results from a measurement of the recently proposed observable, $v_0(p_T)$, in lead-lead (PbPb) collisions at $\sqrt{s_{NN}}=2.76 \text{ TeV}$, using public data from the CMS Open Data portal. This observable is directly sensitive to radial flow and characterizes the transverse momentum ($p_T$) dependence of radial flow fluctuations, serving as probe of collective phenomena in the quark-gluon plasma (QGP) formed in heavy-ion collisions. Consistently with the ATLAS results at $\sqrt{s_{NN}}=5.02 \text{ TeV}$, we observe the three key features of collective radial flow: long-range correlations in pseudorapidity ($η$), a centrality-independent shape as a function of $p_T$, and factorization in $p_T$. The results presented in this work are generally compatible, within uncertainties, with the ATLAS measurements at $\sqrt{s_{NN}}=5.02\text{ TeV}$ reported in Phys. Rev. Lett. 136, 032301 (2026).

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arXiv2025

Analysis of flow factorization and event-plane correlations based on a maximum likelihood estimator

In this study, we use the maximum likelihood estimator (MLE) to explore factorization and event-plane correlations in relativistic heavy-ion collisions. Our analyses incorporate both numerical simulations and publicly available data from the CMS Collaboration. We focus on Au+Au collisions at 200 GeV and Pb+Pb collisions at 2.76 TeV. The differential flows obtained for various centrality windows and momentum cuts are consistent with conventional methodologies such as multi-particle cumulants and event-plane methods. Leveraging these findings, we proceed to undertake further analysis of flow factorization and event-plane correlations. These quantities are relevant because of their sensitivity to initial-state fluctuations. While higher-order correlators might provide different implementations of factorization ratio, the MLE estimator is readily applied to these scenarios. Moreover, MLE's unique capabilities allow us to compute specific correlators that are typically inaccessible by other means. As an asymptotically normal and unbiased estimator, MLE provides a valuable alternative tool for flow and correlation analysis.

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arXiv2024

Extracting the speed of sound in the strongly interacting matter created in relativistic nuclear collisions with the CMS experiment

A hot and dense matter exhibiting collective flow behavior with almost no viscous dissipation has been discovered in ultrarelativistic nuclear collisions. To constrain the fundamental degrees of freedom and equation of state of this matter, these proceedings present an extraction of its speed of sound using head-on lead-lead collision data collected by the CMS experiment at a center-of-mass energy per nucleon pair of 5.02 TeV. The measurement is based on an analysis of the observed charged multiplicity dependence of the average particle transverse momentum in ultra-central events (impact parameter of nearly zero), a variable which probes the system temperature as a function of entropy density at a fixed volume. Results are compared with hydrodynamic simulations and lattice quantum chromodynamics (QCD) predictions of the equation of state at high temperatures and small chemical potential. Implications to search for QCD phase transition and the critical point are discussed.

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arXiv2022

Recent results on femtoscopic correlations with the CMS experiment

The study of femtoscopic correlations in high-energy collisions is a powerful tool to investigate the space-time structure of the particle emitting region formed in such collisions, as well as to probe interactions that the involved particles may undergo after being emitted. An overview of the recent results from the CMS experiment at the LHC on the two-particle femtoscopic correlations measurements using charged particles and identified hadrons in pp and PbPb collisions is presented. In general, the femtoscopic parameters are obtained assuming a Gaussian or an exponential shape to describe the emitting source distribution. In some cases, however, the generalized Gaussian, i.e., the symmetric alpha-stable Lévy distribution, is favored to describe the source. Some of the measurements allow to extract the parameters of the strong interaction felt by hadrons using their femtoscopic correlations. The studies are performed in a wide range of the pair average transverse momentum (or average transverse mass) and charged particle multiplicities. In addition, prospects for future physics results using the CMS experiment are also discussed.

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arXiv2021

Recent results of $\text{D}^{0}$ mesons azimuthal anisotropy using the CMS detector

In a relativistic heavy ion collision, heavy flavor (charm and bottom) quarks are mostly created via hard processes at the early stage of the collisions. We present the latest results of the azimuthal anisotropy coefficients $v_{\text{n}}$ for prompt and nonprompt $\text{D}^{0}$ mesons in PbPb, pPb, and pp collisions from the CMS experiment. The studies are about collectivity phenomena in smaller systems (pp and pPb collisions), searches for the effects of very strong electromagnetic fields created in the initial stages of ultrarelativistic PbPb collisions, and charm quark energy loss in the quark-gluon plasma.

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