Previous efforts on the extraction of jet quenching parameter $\hat{q}$ were mainly focused on the production suppression of $\pi^0$. However, we have achieved some understanding of the production suppression patterns of different mesons by conducting $R_{\rm AA}$ and particle ratios calculations and analysis for $\pi^0$, $\eta$, $\rho^0$ and $\phi$.
In this work, we pave the way to further...
The first measurements of $\Sigma^{0}$ and $\overline{\Sigma}^{0}$ baryons transverse momentum ($p_{\rm{T}}$) spectra, integrated yields and mean $p_{\rm T}$ in pp collisions at $\sqrt{s} = 7$ TeV at the LHC are presented. The $\Sigma^{0}$ ($\overline{\Sigma}^{0}$) signal is reconstructed via the $\Lambda$ ($\overline{\Lambda}$) + $\gamma$ decay channel by invariant mass analysis. The...
Quarkonia suppression in heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) experiments indicate the quark-gluon plasma (QGP) formation in such collisions. Recent experiments at LHC has given some indications of hot matter effect in asymmetric p$-$Pb nuclear collisions. Here, we employ a theoretical model to investigate the bottomonium...
The observed suppression of single inclusive jets in heavy-ion collisions at LHC has a very weak $p_T$ dependence over a large range of $p_T$=50-1000 GeV and is almost independent of the colliding energy, though the initial energy density of the formed QGP has increased significantly from $\sqrt{s}$=2.76 to 5.02 TeV. The single inclusive hadron suppression, however, has strong $p_{T}$...
Using the extraordinary versatility of RHIC in selecting different colliding species, the PHENIX experiment has collected data in p+Al, p+Au, d+Au, and 3He+Au at 200 GeV center-of-mass energy and conducted a comprehensive set of anisotropic flow measurements. These geometry-controlled experiments provide a unique testing ground for early state dynamics using different theoretical models. ...
The production of heavy quarkonia in high-energy nuclear collisions is a sensitive probe of Quantum Chromo Dynamics (QCD) due to the large scale of the heavy quark mass relative to the hadronization scale. The angular distributions of the decay leptons from quarkonia bound states together with quarkonia absolute yields are key observables sensitive to their production mechanisms. PHENIX has...
In relativistic heavy-ion collisions, a parton while traversing through the QGP
medium gets modified energetically followed by fragmentation and hadronisation,
leading to final state hadrons. This modification is reflected in the ratio of the pT spectra of final state hadrons from heavy-ion (AA) collisions to that of proton-proton (pp) collisions i.e. in the nuclear modification factors (RAA...
While collision centrality for large heavy ion systems is well defined
both theoretically and in the experiments, the same is not true when
very asymmetric systems (like p/d+A) collide. In light of some surprising
and in part contradictory results on the centrality dependence of certain
observables in p/d+A collisions that emerged since 2012 from RHIC and LHC,
the very concept of the...
The ALICE experiment at the LHC is designed to investigate the properties of the Quark-Gluon Plasma by studying high energy pp, p-Pb and Pb-Pb collisions. The measurement of the charged particles production and their nuclear modification factor at high transverse momentum can help to shed light on the parton energy loss in the medium. In ALICE, the identification of charged particles is...
Low-mass dielectron measurements play an essential role in the study of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions. They are produced in all stages of the collision and are not affected by final-state interactions. Thus, they provide a penetrating probe of the created medium.
In the dielectron intermediate-mass region a measurement of the thermal radiation...
The equation of state (EoS) of quark-gluon plasma (QGP) using a phenomenological model is studied with the effect of magnetic field. The model results provide EoS of QGP which are in good agreement with Lattice QCD results. This model is successfully applied to the description of the properties of quark-gluon plasma created in the collision of nucleons. Thus, the effect of magnetic field shows...
Heavy flavour probes provide important information about the in-medium properties of the quark gluon plasma produced in heavy-ion collisions. In this work, we investigate the effects of (2+1)d event-by-event fluctuating hydrodynamic backgrounds on the nuclear suppression factor and momentum anisotropies of heavy flavour mesons and non-photonic electrons [1,2]. Using the state-of-the-art D and...
High energy particles traversing through medium primarily lose energy by showering through hard bremsstrahlung and pair production. These splitting processes are coherent over large distances in the very high energy limit, leading to suppression from the LPM effect. Avoiding soft-gluon approximations, we study the cases where the coherence lengths of two consecutive splittings overlap (which...
In this talk, we study the hydrodynamic collectivity in Pb + Pb collisions at 2.76 TeV and 5.02 TeV and proton + proton collisions at 13 TeV using the iEBE-VISHNU hybrid model. For Pb + Pb collision systems, we use TRENTo and AMPT initial conditions. With properly chosen and turned parameter sets, our model calculations can nicely describe various flow obsevables in 2.76 TeV and 5.02 TeV Pb +...
Jets are produced from the fragmentation of hard scattered partons (quarks and gluons) in high energy collisions. Jets originating from quarks and gluons, which differ in their color charges, are expected to have different properties (jet fragmentation, jet constituents multiplicity, jet size). In experiments, measurements of inclusive jets contain contributions from both quarks and gluons....
Direct photons produced in Compton and annihilation hard process at the leading order can be calculated by perturbative QCD. Photon-hadron correlations in heavy-ion collisions allow us to investigate medium induced jet modifications. Correlations between photon triggers and associated charged hadrons are used to study the jet fragmentation function of away side jets generated together with the...
In high-energy pp collisions, there can be a substantial contribution from Multi-Parton Interactions (MPI) in particle production mechanisms. In this case, several interactions at the partonic level occur in a single pp collision and this implies a correlation between the particle production and the total event multiplicity. At the LHC energies, MPI might occur at hard momentum scales, thus...
The JETSCAPE Collaboration (Jet Energy-loss Tomography with a Statistically and Computationally Advanced Program Envelope) has developed and released an innovative, modular and flexible event generator to be used by the heavy-ion community [1]. The wide range of physical processes that take place in a heavy-ion collision, coupled with the lack of consensus on the underlying physical...
Heavy flavor probes consist of an important asset to the study of the properties of the quark gluon plasma formed in heavy ion collisions. Furthermore, the longitudinal dependence of observables in addition to the mid-rapidity regime can provide further insight on the dynamics of the medium. In this work we investigate D mesons coupling with the medium in the rapidity range $-5.0 < y < 5.0$...
Low-mass dimuon production, including decays of light neutral mesons η, ρ, ω, φ, provides key information on the hot and dense state of strongly interacting matter produced in ultra-relativistic heavy-ion collisions. The proper baseline for these observations is provided by the measurements of low-mass dimuons in pp collisions, which also allows for the tuning of light particle production...
Jet is the collection of concentrated final state hadrons produced from the fragmentation of hard scattered parton in high energy hadronic, leptonic or heavy-ion collision. In proton-proton (pp) collisions, measurement of jet production cross-sections and jet properties provide validation for perturbative Quantum Chromo Dynamics (pQCD) and gives detailed insight into the parton to jet...
The measurement of hadrons containing heavy quarks produced in heavy-ion collisions is a very effective tool to study the Quark Gluon Plasma (QGP). Heavy quarks are produced in the very early stages of the collisions via hard scattering processes, they probe the whole medium evolution and lose energy via elastic and radiative processes. However, in order to obtain information regarding the QGP...
The heavy-ion physics program of the ALICE experiment at the LHC aims to reveal the properties of strongly interacting QCD matter, the so-called Quark-Gluon Plasma(QGP), which is formed under extreme energy density conditions.
Jets are well calibrated and established probes of the QGP properties. At the
formation of QGP, initial energies of the hard scattered partons, which are the
origin of...
Data collected by the ATLAS experiment during the 2015 Pb+Pb and 2017 Xe+Xe LHC runs offer new opportunities to study charged particle azimuthal anisotropies in heavy ion collisions. This should improve the understanding of initial conditions of nuclear collisions, hydrodynamical behavior of quark-gluon plasma and parton energy loss. ATLAS measurements of differential and inclusive Fourier...
Bottomonia are important probes of the quark-gluon plasma since they are produced at early times and propagate through the medium. The production cross sections of the three Y states (1S, 2S, 3S) were measured by CMS in pp, pPb and PbPb collisions at 5.02 TeV. A strong suppression is observed in PbPb collisions but the Y(3S) was not observed clearly in PbPb collisions. This suppression was...
One of Richard Feynman's shortest and most cited papers concerns his prediction that for very high energy collisions, the analyticity condition for quantum fields should cause the fragmentation of a nuclear target to become independent of the collision energy. CMS has measured the pseudorapidity dependence of charged-hadron multiplicity and transverse energy for a wide range of energies and...
High multiplicity events of small colliding systems at high c.m.s. energies show similar collective features to heavy ion collisions with comparable multiplicities, such as long-range near-side correlations and v_n coefficients [1,2]. Whether this behaviour may be attributed to the presence of a deconfined state in small systems is an open question.
Recent analyses of pp and p-Pb collisions...
A jet is a spray of collimated hadrons originated in the fragmentation of an energetic
parton. The cross section measurement provides a good test for pQCD calculations,
and jet production in pp collisions constitutes a reference for jet quenching
study in nucleus-nucleus collisions. In addition, the measurements in different
multiplicity intervals will provide insights to understand the...
In heavy-ion collisions, beauty quarks are created in the initial stage via hard parton scattering and experience the full evolution of the Quark Gluon Plasma (QGP). Thus, studying beauty hadrons is important to our understanding of the mass dependence of energy loss in this deconfined medium. We can extract information about energy loss by measuring the nuclear modification factor of beauty...
We here present two frameworks that allow generating a wide range of predictions from the dynamical energy loss formalism [1,2]. In distinction to majority of other methods, the dynamical energy loss formalism takes into account a realistic medium composed of dynamical scattering centers. The first framework (DREENA-C) [1] applies to the medium with constant temperature, while the second...
In heavy-ion collisions, the Quark-Gluon Plasma is formed. While jets, created in these collisions, traverse this hot and dense medium, they can interact with it. This interaction can be studied by direct jet reconstruction at high transverse momentum and by two-particle angular correlation measurements in the regime which is not accessible by the jet reconstruction algorithms. In...
The JETSCAPE Collaboration (Jet Energy-loss Tomography with a Statistically and Computationally Advanced Program Envelope) has developed and released an innovative, modular and flexible event generator to be used by the heavy-ion community. In this talk we discuss simulations of p+p collisions using this generator, with emphasis on jet production and jet observables. We present calculations of...
In Pb-Pb collisions at the LHC, a hot and dense medium of deconfined quarks and gluons is formed (Quark-Gluon Plasma, QGP).
The QGP is conjectured to be the state of matter of the early Universe up to few microseconds after the Big Bang and may still exist in the core of neutron stars. One of the most striking signatures of the QGP formation in heavy-ion collisions is the suppression of jet...
As hard scattered partons traverse and interact with the quark-gluon plasma (QGP), they lose energy, and the resulting jet is expected to be broadened. Thus, by comparing the modified jets from Au+Au to p+p collisions, one can study the properties of the QGP. Using a high-$p_T$ $\pi^0$ as a proxy for the jet, $\pi^0$-hadron correlations can be used to measure modifications to jets. A previous...
The large elliptic flow discovered at RHIC energies continuously increases also in the highest beam energy $\sqrt{s_{NN}}$=$5.02$~TeV in LHC. This was expected by calculations utilizing viscous hydrodynamics. These calculations also demonstrated that the shear viscosity to the entropy density ratio ($\eta/s$) of the created medium is close to a universal lower bound $1/4\pi$ in heavy ion...
Under extreme conditions of temperature and pressure, Quantum Chromodynamics predicts the formation of the Quark-Gluon Plasma (QGP). Heavy-ion collisions at ultra-relativistic energies at the Large Hadron Collider produce the optimal conditions to form the QGP in the laboratory. The hot QCD matter is produced within an unprecedented strong magnetic field, whose properties and effects have not...
Heavy quarks are initially produced in nuclear collisions and the number is conserved during the evolution of the system. We establish a sequential coalescence model with charm conservation and apply it to charmed hadron production at RHIC and LHC energies. The charm conservation enhances the earlier formed hadrons and reduces the later formed ones, which leads to a $D_s/D^0$ enhancement and a...
We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differential number correlation functions, $R_{2}( \Delta \eta, \Delta \varphi)$, and transverse momentum correlation functions, $P_{2}( \Delta \eta, \Delta \varphi)$, of charged particles produced in pp collisions at the LHC centre-of-mass energy $\sqrt{\textit{s}}$ = 2.76 TeV with the PYTHIA and HERWIG...
Besides the measurements of inclusive jet yield and its modification in heavy-ion collisions compared to that in proton-proton (jet RAA ), there is considerable interest in the measurements of intra-jet properties like jet shape, fragmentation function (FF) etc. These observables are seen to be sensitive to the microscopic details of jet-medium interactions and provide insights on the...
We introduce a novel fragmentation function parametrization
based on the non-extensive statistical phenomena. Parametrization of
the leading order fragmentation functions is made for the
hadronization of partons to charged pions, kaons, and protons. The
obtained parameters are result of fit to data from electron-positron
annihilation, however contains information on the statistical
properties...
Understanding the energy loss of partons traversing the strongly interacting matter created in heavy ion collisions is one of key goals of the heavy ion physics program. In this talk we present results of phenomenological analyses of various recent jet quenching data. The core of the model used in these analyses is based on the shift formalism which allows for an extraction of the magnitude of...
Heavy flavours are useful probes for the study of cold and hot QCD matter. Therefore, having a good understanding and control on the formulas describing their production is primordial.
We will start with the detailed analysis of the following 4 statements:
- At small-x the main contribution comes from $gg \rightarrow Q\bar{Q}$
- At small-x the gluon distribution is much bigger than the...
