arXiv subjects

Jacquelyn Noronha-Hostler

Publications and source records attributed to Jacquelyn Noronha-Hostler.

At least 127 records · Page 7Linked to original sources

arXiv2017

Jet modifications in event-by-event hydrodynamically evolving media

The nearly perfect fluid-like nature of the Quark Gluon Plasma may be understood through two key experimental signatures: collective flow and jet suppression. Event-by-event relativistic viscous hydrodynamics (with an extremely small shear viscosity to entropy density ratio) has been very successful at describing collective flow observables for the last 7 years. More recently, the effects of event-by-event fluctuations have been studied in the context of high $p_T$ particles that lose energy as they pass through the dense Quark Gluon Plasma liquid. In this summary of the corresponding plenary talk at Quark Matter 2017, the recent developments on the effects of event-by-event fluctuations on jet suppression are summarized.

nucl-th↗

arXiv2017

Constraining the hadronic spectrum through QCD thermodynamics on the lattice

Fluctuations of conserved charges allow to study the chemical composition of hadronic matter. A comparison between lattice simulations and the Hadron Resonance Gas (HRG) model suggested the existence of missing strange resonances. To clarify this issue we calculate the partial pressures of mesons and baryons with different strangeness quantum numbers using lattice simulations in the confined phase of QCD. In order to make this calculation feasible, we perform simulations at imaginary strangeness chemical potentials. We systematically study the effect of different hadronic spectra on thermodynamic observables in the HRG model and compare to lattice QCD results. We show that, for each hadronic sector, the well established states are not enough in order to have agreement with the lattice results. Additional states, either listed in the Particle Data Group booklet (PDG) but not well established, or predicted by the Quark Model (QM), are necessary in order to reproduce the lattice data. For mesons, it appears that the PDG and the quark model do not list enough strange mesons, or that, in this sector, interactions beyond those included in the HRG model are needed to reproduce the lattice QCD results.

hep-lat↗

arXiv2017

Skewness of elliptic flow fluctuations

Using event-by-event hydrodynamic calculations, we find that the fluctuations of the elliptic flow ($v_2$) in the reaction plane have a negative skew. We compare the skewness of $v_2$ fluctuations to that of initial eccentricity fluctuations. We show that skewness is the main effect lifting the degeneracy between higher-order cumulants, with negative skew corresponding to the hierarchy $v_2\{4\}>v_2\{6\}$ observed in Pb+Pb collisions at the LHC. We describe how the skewness can be measured experimentally and show that hydrodynamics naturally reproduces its magnitude and centrality dependence.

nucl-th↗

arXiv2016

Implications of Missing Resonances in Heavy Ions Collisions

Between 2004 until today many new resonances in the QCD spectrum have been added by the Particle Data Group. However, it is still possible that there are further states that have yet to be measured, as predicted by Lattice QCD calculations and Quark Models. In this paper I review how these missing states would influence the field of heavy-ion collisions. Additionally, the quantum numbers that characterize these missing states are also discussed.

nucl-th↗

arXiv2016

Heavy meson flow harmonics in event-by-event viscous relativistic hydrodynamics

Event-by-event viscous hydrodynamics is combined with heavy quark energy loss models to compute heavy flavor flow cumulants $v_2\{2\}$, $v_3\{2\}$, and $v_2\{4\}$ as well as the nuclear modification factors of $D^0$ and $B^0$ mesons in PbPb collisions at 2.76 TeV. Our results indicate that bottom quarks can flow as much as charm quarks in the $p_T$ range 8--30 GeV.

nucl-th↗

arXiv2016

Resolving the $R_{AA}$ to $v_n$ puzzle

After 10 years of struggling to simultaneously describe the nuclear modification factor $R_{AA}$ and flow harmonics $v_n$'s at high $p_T$, now theoretical models are able to reproduce experimental data well. The necessary theoretical developments such as event-by-event fluctuations, choice of initial conditions, and the scalar product method to calculate flow harmonics at high $p_T$ are reviewed. Additionally, a discussion of new proposed experimental observables known as Soft Hard Event Engineering (SHEE) that are sensitive to the path length dependence of the energy loss is included.

nucl-th↗

arXiv2016

Cumulants and nonlinear response of high $p_T$ harmonic flow at $\sqrt{s_{NN}}=5.02$ TeV

Event-by-event fluctuations caused by quantum mechanical fluctuations in the wave function of colliding nuclei in ultrarelativistic heavy ion collisions were recently shown to be necessary for the simultaneous description of $R_{AA}$ as well as the elliptic and triangular flow harmonics at high $p_T$ in PbPb collisions at the Large Hadron Collider. In fact, the presence of a finite triangular flow as well as cumulants of the flow harmonic distribution that differ from the mean are only possible when these event-by-event fluctuations are considered. In this paper we combine event-by-event viscous hydrodynamics and jet quenching to make predictions for high $p_T$ $R_{AA}$, $v_2\{2\}$, $v_3\{2\}$, and $v_2\{4\}$ in PbPb collisions at $\sqrt{s_{NN}}=5.02$ TeV. With an order of magnitude larger statistics we find that high $p_T$ elliptic flow does not scale linearly with the soft elliptical flow, as originally thought, but has deviations from perfectly linear scaling. A new experimental observable, which involves the difference between the ratio of harmonic flow cumulants at high and low $p_T$, is proposed to investigate the fluctuations of high $p_T$ flow harmonics and measure this nonlinear response. By varying the path length dependence of the energy loss and the viscosity of the evolving medium we find that $R_{AA}(p_T)$ and $v_2\{2\}(p_T)$ strongly depend on the choice for the path length dependence of the energy loss, which can be constrained using the new LHC run 2 data.

nucl-th↗

arXiv2016

Hydrodynamic Overview at Hot Quarks 2016

This presents an overview of relativistic hydrodynamic modeling in heavy-ion collisions prepared for Hot Quarks 2016, at South Padre Island, TX, USA. The influence of the initial state and viscosity on various experimental observables are discussed. Specific problems that arise in the hydrodynamical modeling at the Beam Energy Scan are briefly discussed.

nucl-th↗

arXiv2016

Hydrodynamic Predictions for Mixed Harmonic Correlations in 200 GeV Au+Au Collisions

Recent measurements at the LHC involve the correlation of different azimuthal flow harmonics $v_n$. These new observables add constraints to theoretical models and probe aspects of the system that are independent of the traditional single-harmonic measurements such as 2- and multi-particle cumulants $v_n\{m\}$. Many of these new observables have not yet been measured at RHIC, leaving an opportunity to make predictions as a test of models across energies. We make predictions using NeXSPheRIO, a hydrodynamical model which has accurately reproduced a large set of single-harmonic correlations in a large range of transverse momenta and centralities at RHIC. Our predictions thus provide an important baseline for comparison to correlations of flow harmonics, which contain non-trivial information about the initial state as well as QGP transport properties. We also point out significant biases that can appear when using wide centrality bins and non-trivial event weighting, necessitating care in performing experimental analyses and in comparing theoretical calculations to these measurements.

nucl-th↗

arXiv2016

Strangeness at finite temperature from Lattice QCD

The precision reached by recent lattice QCD results allows for the first time to investigate whether the measured hadronic spectrum is missing some additional strange states, which are predicted by the Quark Model but have not yet been detected. This can be done by comparing some sensitive thermodynamic observables from lattice QCD to the predictions of the Hadron Resonance Gas model (with the inclusion of decays [3]). We propose a set of specific observables, defined as linear combinations of conserved charge fluctuations, which allow to investigate this issue for baryons containing one or more strange quarks separately. Applications of these observables to isolate the multiplicity fluctuations of kaons from lattice QCD, and their comparison with the experimental results, are also discussed.

nucl-th↗

arXiv2016

Heavy flavor $R_\text{AA}$ and $v_n$ in event-by-event viscous relativistic hydrodynamics

Recently it has been shown that a realistic description of the medium via event-by-event viscous hydrodynamics plays an important role in the long-standing $R_\text{AA}$ vs. $v_2$ puzzle at high $p_T$. In this proceedings we begin to extend this approach to the heavy flavor sector by investigating the effects of full event-by-event fluctuating hydrodynamic backgrounds on the nuclear suppression factor and $v_2\{2\}$ of heavy flavor mesons and non-photonic electrons at intermediate to high $p_T$. We also show results for $v_3\{2\}$ of $B^0$ and D$^0$ for PbPb collisions at $\sqrt{s}=2.76$ TeV.

nucl-th↗

arXiv2016

The fluctuations of quadrangular flow

The ATLAS Collaboration has measured for the first time the fourth cumulant of quadrangular flow, $v_4\{4\}^4$. Unlike the fourth cumulants of elliptic and triangular flows, it presents a change of sign above 30\% centrality. We show that this change of sign is predicted by event-by-event hydrodynamics. We argue that it results from the combined effects of a nonlinear hydrodynamic response, which couples quadrangular flow to elliptic flow, and elliptic flow fluctuations.

nucl-th↗

arXiv2016

Kaon fluctuations from lattice QCD

We show that it is possible to isolate a set of kaon fluctuations in lattice QCD. By means of the Hadron Resonance Gas (HRG) model, we calculate the actual kaon second-to-first fluctuation ratio, which receives contribution from primordial kaons and resonance decays, and show that it is very close to the one obtained for primordial kaons in the Boltzmann approximation. The latter only involves the strangeness and electric charge chemical potentials, which are functions of $T$ and $μ_B$ due to the experimental constraint on strangeness and electric charge, and can therefore be calculated on the lattice. This provides an unambiguous method to extract the kaon freeze-out temperature, by comparing the lattice results to the experimental values for the corresponding fluctuations.

hep-ph↗

arXiv2016

Symmetric cumulants and event-plane correlations in Pb+Pb collisions

The ALICE Collaboration has recently measured the correlations between amplitudes of anisotropic flow in different Fourier harmonics, referred to as symmetric cumulants. We derive approximate relations between symmetric cumulants involving $v_4$ and $v_5$ and the event-plane correlations measured by ATLAS. The validity of these relations is tested using event-by-event hydrodynamic calculations. The corresponding results are in better agreement with ALICE data than existing hydrodynamic predictions. We make quantitative predictions for three symmetric cumulants which are not yet measured.

nucl-th↗

arXiv2016

Solving the $R_{AA}\otimes v_2$ puzzle

For the past ten years $R_{AA}(p_T)$, the nuclear modification factor that encodes the suppression of high $p_T$ particles due to energy loss within the medium was fairly well described by many theoretical models. However, the same models systematically under-predicted the high $p_T$ elliptic flow, $v_2$, which is experimentally measured as the correlation between soft and hard hadrons. All previous calculations neglected the effect of event-by-event fluctuations of an expanding viscous hydrodynamical background as well as the soft-hard flow harmonic correlations in the experimentally measured $v_2$. In this talk I show how event-by-event viscous hydrodynamics (computed using the v-USPhydro code) coupled to an energy loss model (BBMG) is able to simultaneously describe soft physics observables as well as the high-$p_T$ $R_{AA}$ and $v_2$. Suggestions for future more differential calculations at the LHC run2 are made to explore soft-hard flow correlations.

nucl-th↗

arXiv2016

Event-by-event hydrodynamics $+$ jet energy loss: A solution to the $R_{AA} \otimes v_2$ puzzle

High $p_T > 10$ GeV elliptic flow, which is experimentally measured via the correlation between soft and hard hadrons, receives competing contributions from event-by-event fluctuations of the low $p_T$ elliptic flow and event plane angle fluctuations in the soft sector. In this paper, a proper account of these event-by-event fluctuations in the soft sector, modeled via viscous hydrodynamics, is combined with a jet energy loss model to reveal that the positive contribution from low $p_T$ $v_2$ fluctuations overwhelms the negative contributions from event plane fluctuations. This leads to an enhancement of high $p_T > 10$ GeV elliptic flow in comparison to previous calculations and provides a natural solution to the decade long high $p_T$ $R_{AA} \otimes v_2$ puzzle. We also present the first theoretical calculation of high $p_T$ $v_3$, which is shown to be compatible with current LHC data. Furthermore, we discuss how short wavelength jet-medium physics can be deconvoluted from the physics of soft, bulk event-by-event flow observables using event shape engineering techniques.

nucl-th↗

arXiv2016

Hydrodynamic predictions for 5.02 TeV Pb-Pb collisions

We make predictions for momentum-integrated elliptic and triangular flow as well as mean transverse momentum for 5.02 TeV Pb-Pb collisions, as planned at the Large Hadron Collider. We use hydrodynamic calculations to predict the change of these observables as the center-of-mass collision energy evolves from 2.76 TeV to 5.02 TeV per nucleon pair. By using previously measured values as a baseline, we are able to make a robust prediction without relying on a particular model for initial conditions and without precise knowledge of medium properties such as viscosity. Thus, though the predicted changes are small, they can provide a significant test of the current hydrodynamic picture of heavy-ion collisions.

nucl-th↗

arXiv2016

Linear and cubic response to the initial eccentricity in heavy-ion collisions

We study the relation between elliptic flow, $v_2$ and the initial eccentricity, $\varepsilon_2$, in heavy-ion collisions, using hydrodynamic simulations. Significant deviations from linear eccentricity scaling are seen in more peripheral collisions. We identify the mechanism responsible for these deviations as a cubic response, which we argue is a generic property of the hydrodynamic response to the initial density profile. The cubic response increases elliptic flow fluctuations, thereby improving agreement of initial condition models with experimental data.

nucl-th↗