High-energy proton-proton (pp) collisions at large final state particle multiplicities exhibit heavy ion-like behaviors. Among many others, one of the peculiar feature of heavy ions is partonic energy loss (aka jet quenching) in the produced Quark-Gluon Plasma. The search for jet quenching effects also in small collision systems (such as pp) is warranted. To date no evidence of jet quenching...
Studying the quenching of high momentum particles in collision systems of various shapes and sizes provides crucial insights on the initial conditions and the transport properties of the QGP. Such insights can be obtained via investigations of the high transverse momentum ($p_T$) anisotropy harmonics and their collision energy and system-size dependence. We present the beam-energy and...
The sPHENIX detector at BNLโs Relativistic Heavy Ion Collider (RHIC) will measure a suite of unique jet and Upsilon observables with unprecedented statistics and kinematic reach at RHIC energies. A MAPS-based vertex detector upgrade to sPHENIX, the MVTX, will provide a precise determination of the impact parameter of tracks relative to the primary vertex in high multiplicity heavy ion...
In heavy-ion collisions, the observed non-zero second-order azimuthal anisotropy coefficient, $v_{2}$, for particles with high transverse momenta $\it{p}_{\rm T}$ is driven by the path-length dependent energy loss of hard partons travelling in the QGP, known as the jet quenching effect. Recent measurements show also a non-zero $v_{2}$ values for high $\it{p}_{\rm T}$ charged particles at high...
Measurements of two-particle correlations in $pp$ collisions show the presence of
long-range correlations along $\Delta\eta$ that are strikingly similar to
those seen in heavy-ion collisions.
In heavy-ion collisions, the long-range correlations are known to arise from the
collective dynamics of the produced quark-gluon plasma (QGP).
The similarity between the $pp$ and heavy-ion...
We establish the existence of a far-from-equilibrium attractor in weakly-coupled gauge theory undergoing one-dimensional Bjorken expansion. We demonstrate that the resulting far-from-equilibrium evolution is insensitive to certain features of the initial condition, including both the initial momentum-space anisotropy and initial occupancy. We find that this insensitivity extends beyond the...
Probing the quark gluon plasma in small system is a hot topic nowadays. By combining the thermal and hard parts, with the Cooper-Frye freeze-out, quark coalescence and hard parton fragmentation hadronization mechanisms, we investigate the $p_T$-spectra, the differential elliptic flow and the number of constituent quark (NCQ) scaling of pions, kaons and protons of high multiplicity p+ Pb...
The exploration of the fundamental structures of nucleon and nucleus has always thrived on the complementarity of lepton scattering and purely hadronic probes. With the Electron Ion Collider (EIC) on the horizon, it becomes more urgent than ever to complete key measurements in this regard with high precision in hadonic $p$+$p$ and $p$+Au collisions during the final years of RHIC running. When...
One of the most important discoveries at the LHC is the observation of collective-like behavior and strangeness enhancement in small collision systems (e.g. pp and p-Pb collisions). They effects are strikingly similar to those observed in heavy-ion collisions, where they are attributed to the production of a deconfined hot and dense medium, known as strongly interacting Quark-Gluon Plasma. In...
The axial-vector form factors of the decuplet baryons are investigated in the chiral constituent quark model using their explicit quark spin polarizations. The ``quark sea'' arises from the chiral symmetry breaking which results in the Goldstone bosons mediating the interaction between constituent quarks. The axial-vector form factors which have some physical significance corresponding to...
During the large hadron collider long shutdown 2 (LHC-LS2), the Muon Spectrometer of the ATLAS experiment known a major upgrade in the region 1.0 <ฮท< 1.3. motivated by the improving of the high-Pt measurement within the trigger system, where the old monitored drift tube chambers will be replaced by new ones in which an additional trigger detector RPC (resistive plate chambers) will be...
We present a way to construct 3D initial conditions for relativistic heavy-ion collisions based on the Glauber collision geometry [1]. Local energy and momentum conservation conditions are imposed to set non-trivial constraints on our longitudinal profilesโ parameterizations for the systemโs initial energy density and flow velocity. We show that the $\sqrt{T_A T_B}$ scaling of initial energy...
We introduce the Trajectum framework, a new heavy ion code which incorporates many of the necessary components to perform a heavy ion collision simulation in one executable. We use Trajectum to study a generalization of the TRENTo initial conditions, namely varying the free streaming velocity $v_\text{fs}$. In addition, we show the results of a Bayesian analysis performed with this...
The charmonium states with their different binding energies and radii dissolve at different temperatures of the medium produced in relativistic heavy-ion collisions. Relative yields of charmonium and thus their survival have potential to map the properties of Quark Gluon Plasma, the medium created in the collisions. In this study, we estimate the combined effect of color screening,...
Dileptons are a prime probe of the deconfined state of strongly interacting matter, the quark--gluon plasma (QGP), produced in high-energy heavy-ion collisions, as they are not affected by strong interactions after their creation.
A measurement of the thermal radiation from the QGP in the mass region between the $\phi$ and the $\rm J/\psi$ allows to estimate the medium temperature. In this...
Collective phenomena in heavy-ion collisions are very sensitive to initial geometry including nuclei deformation effects. Recent hydrodynamic model calculations suggest that such deformation effects can be probed by studying event-by-event mean $p_T$ ($\left \langle p_T \right \rangle$) fluctuation and the correlation between mean $p_T$ and harmonic flow. In particular, due to prolate shape of...
No existing model for the initial stages of a heavy-ion collision, when used as initial conditions for hydrodynamics simulations, can provide a satisfactory description of flow in ultra-central collisions. It is therefore useful to understand what properties the initial stages must have in order to be compatible with experimental data. To this end, we parameterize the early-time energy density...
We develop an Effective Field Theory (EFT) framework to compute jet substructure observables for heavy ion collision experiments.
We consider dijet events that accompany the formation of a Quark Gluon Plasma medium in a heavy ion collision and look at the simultaneous measurement of jet mass along with the transverse momentum imbalance between the jets accounting for both vacuum and medium...
We present the results of the second-order Fourier coefficients (v2), which characterizes the azimuthal anisotropy, in p+p, p+Au, and d+Au collisions at sqrt(sNN) = 200 GeV. The v2 values are calculated via the two-particle correlation method. To investigate the role of initial geometry effects, the measured v2 is extracted by two different kinematic selections. The two results are compared...
Over the last years, Machine Learning (ML) tools have been successfully applied to a wealth of problems in high-energy physics. Supervised ML methods allow for significant improvements in classification problems by taking into account correlations among observables and by learning the optimal selection from prepared samples. In this talk, we will discuss the application of ML for the...
Multiparticle correlation techniques have been used to study the nature of long-range collectivity in small collision systems. The subevent cumulant method was shown to significantly reduce the nonflow contributions compared to the standard cumulant method. However, a jet could fall across the boundary between two neighboring subevents and residual nonflow exists in this method. Requiring an...
Jet quenching is a possible consequence of the formation of a quark-gluon plasma (QGP) in collision systems, but to date no significant jet quenching has been observed in small systems. At the same time final states of pp and pPb collisions with large underlying event activity exhibit collective behavior that resembles hydrodynamic evolution. It is believed that observed level of the...
Studies of the production of light-flavor hadrons in different collision systems are of prominent importance to investigate the hadronisation process. Recently, the ALICE Collaboration has presented results from pp, pA and AA collisions, exploiting its detector's excellent tracking and PID capabilities down to low transverse momentum. Pions, kaons, protons and (multi-)strange hadrons have been...
In high energy heavy-ion collisions, the pre-equilibrium stage of the quark-gluon plasma (QGP) is the most crucial ingredient in the estimate of electromagnetic (EM) fields, especially for the lifetime of the magnetic field that plays a key role in the chiral magnetic effect (CME).
In this talk, we present a theoretical estimate for the realistic dynamical evolution of EM fields in the...
We present the computation of exclusive and inclusive dijet production in electron-proton and electron- nucleus collisions at small-x within the Color Glass Condensate effective field theory. We compute the cross- sections differentially in mean dijet momentum and momentum imbalance, as well as its corresponding elliptic anisotropy. For exclusive dijet production, we employ a dipole model with...
Heavy quarks, which are produced at the earliest stage of relativistic heavy-ion collisions, probe the entire history of the quark-gluon plasma that is created in the collision. Initially the plasma is populated with chromodynamic fields which can be treated as classical. In the talk transport of heavy quarks interacting with such long-wavelength chromodynamic fields will be discussed. The...
We calculate eccentricities in dilute-dense limit of pA collisions, by calculating correlations functions of the energy density field of the Glasma immediately after the collision event at proper time $\tau = 0^{+}$. The proton is treated as a collection of a finite number of hot spots of Gaussianly distributed color charges, as in the IPGlasma setup. The correlations of its color charges are...
In the present work, we study the effect of mass-modifications of kaons ($K$) and antikaons ($\bar{K}$) on the experimental observables relevant for nucleus-nucleus collisions. The in-medium masses of $K$ and $\bar{K}$ mesons evaluated using effective hadronic chiral SU(3) mean field model are implemented in A Multi-Phase Transport (AMPT) model to calculate different experimental...
We study the kinematics of nuclei after a collision at close to the speed of light. The nuclei are treated as sources of color-glass condensate that form gluon fields between the nuclei after the collision. We consider this field to be the driving force in the subsequent deceleration and transverse motion of the nuclei. We solve this problem for early times in the general situation, and we...
A new model denoted ICCING (Initial Conserved Charges in Nuclear Geometry) reconstructs the initial conditions of BSQ conserved charges in the QGP by sampling the ($g \rightarrow q\bar{q}$) splitting function over the initial energy density. I will discuss the new open source C++ version of ICCING, coupled to TRENTO. We find that even at top LHC energies that the initial conditions due to...
The ultra-peripheral Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV performed at the ATLAS experiment are used to
study a rare light-by-light scattering process, $\gamma\gamma\rightarrow\gamma\gamma$, allowed in Quantum Electrodynamics via a loop diagram.
The poster summarises recent light-by-light measurements conducted using a combination of 2015 and 2018 datasets recorded by...
We develop a framework to simulate the 3+1D dynamics of the initial energy deposition in heavy-ion collisions by taking into account the finite longitudinal extent of the colliding nuclei in the Color-Glass Condensate framework. Based on a simple model for the color charge distributions of the colliding nuclei, we demonstrate how the boost-invariant limit is recovered at high energies along...
Measurements made recently by the STAR collaboration show that the Lambda hyperons produced in relativistic heavy-ion collisions are subject to global spin polarization with respect to an axis coincident with the axis of rotation of the produced matter. Recently formulated formalism of relativistic hydrodynamics with spin, which is a generalization of the standard hydrodynamics, is a natural...
We show that high-$p_\perp$ $R_{AA}$ and $v_2$ are way more sensitive to the QGP thermalization time, $\tau_0$, than the distributions of low-$p_\perp$ particles, and that the high-$p_\perp$ observables prefer relatively late thermalization at $\tau_0$ โผ 1 fm/c. To calculate high-$p_\perp$ $R_{AA}$ and $v_2$, we employ our newly developed DREENA-A formalism, which combines state-of-the-art...
Understanding the relation between QCD evolution in the Bjorken limit and the Regge limit is crucial to achieve a complete and smooth picture of proton and nuclear structure. The hope in the small x regime, where gluon density is expected to reach saturation and the naif partonic picture is expected to break down, was that by computing higher-order corrections to small x evolution (BK...
In ultrarelativistic heavy-ion collisions, two-particle transverse momentum correlations provide information on the system dynamics and properties. Recently published results by ALICE on the two-particle transverse momentum correlator $G_{2}$ in Pb-Pb collisions demonstrate a narrowing of the correlation function in the azimuthal direction from peripheral to central collisions, which has...
The study of jets in heavy ion collisions provides important information about the interaction of partons with the quark-gluon plasma. Originating from hard scatterings among partons of the colliding nuclei, jets are affected by the entire space-time evolution of the medium, including the pre-equilibrium stage. I report on our numerical lattice simulations of jets traversing the...
We present a new Monte Carlo that generates events based on statistics
specified with any 1-point and 2-point function, including arbitrary
correlations.
Such a code can be useful for quickly generating events when
analytic formulas are known (for example from recent derivations of CGC
fluctuations), and for use in Bayesian analyses, where the initial state can
be characterized by...
Jets are powerful tools for probing the properties of quark-gluon plasma (QGP) formed in high-energy nucleus-nucleus (AA) collisions. Recent results in high-multiplicity pp collisions suggest that QGP is also formed in such collisions since they show similar features to those that are associated with QGP production in AA collisions. Measurement of jet properties in pp collisions as a function...
We study the response of a Bjorken-expanding quark-gluon plasma (QGP) to the passage of an energetic parton through it. By comparing results from Boltzmann equation under the relaxation time approximation with those from viscous hydrodynamics, we observe that the non-hydrodynamic response is significant when the medium excitations with wavelength shorter than the inverse of the relaxation time...
The properties of the strongly intensive variable ฮฃ [1] characterizing correlations between the number of particles produced in two observation windows separated by a rapidity interval in pp interactions at LHC energies are studied in the framework of the string fusion approach [2,3]. The analytical calculations are supplemented by the MC simulations permitting to take into account the...
Measurements of jet suppression and modification in heavy-ion collisions provide powerful and broad information on the dynamics of the hot, dense plasma formed in relativistic nucleus-nucleus collisions.
In this talk at the Initial Stages conference, we present measurements of jet energy loss and modification which are sensitive to the initial transverse geometry of Pb+Pb collisions.
The...
Using the CGC effective theory together with the hybrid factorisation, we study forward dijet production in proton-nucleus collisions beyond leading order. In this paper, we compute the "real" next-to-leading order (NLO) corrections, i.e. the radiative corrections associated with a three-parton final state, out of which only two are being measured. To that aim, we start by revisiting our...
A colliding system of ultra-relativistic heavy-ions is commonly simulated with phenomenological models, which include relativistic hydrodynamics and a hadronic cascade afterburner. Typically, any model of heavy-ion collisions must include some estimate of the initial conditions, whose properties are a subject of intense research. Also, many of the common approaches used in the field have no...
The ALICE experiment, located at the CERN LHC, is dedicated to study the physics of ultra-relativistic heavy-ion collisions. In order to operate the ALICE Time Projection Chamber (TPC) in continuous mode, recording the full minimum-bias interaction rate of 50 kHz in Pb โ Pb collisions, as anticipated at the LHC in Run 3 and beyond, the gated Multi Wire Proportional Chambers (MWPCs) were...
