Conveners
Heavy Ions: 1
- Gian Michele Innocenti (Massachusetts Inst. of Technology (US))
Heavy Ions: 2
- Andrea Rossi (Universita e INFN, Padova (IT))
Heavy Ions: 3
- Francesca Bellini (CERN)
Heavy Ions: 4
- In Kwon Yoo (Pusan National University (KR))
Heavy Ions: 5
- Byungsik Hong (Korea University (KR))
Heavy Ions: 6
- Ralf Averbeck (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))
We present new results on quarkonia production in pPb collisions, using the data collected in 2016 at 8.16 TeV nucleon-nucleon centre-of-mass energy, in the unique forward region (pseudorapidity between 2 and 5) covered by the LHCb detector. Both forward and backward rapidities are covered thanks to the possibility of beam reversal. Measurements include the vector bottomonia states and the...
In pp collisions at LHC energies, charmonium resonances are predominantly produced in hard scattering processes and a subsequent hadronization of the heavy quark pair into a bound state. The production process involves very different energy scales, with the initial quark pair being produced in a high-$Q^2$ process that allows for a perturbative treatment while the following formation of the...
The nuclear modification factors of the ground and excited states of J/psi were measured via dimuon channels in pPb and PbPb collisions at 5.02 TeV. The analysis was performed as functions of collision centrality, rapidity, and transverse momentum. The results are discussed in the framework of the modified nuclear parton distribution function (for pPb) and the interaction of charmonia with...
Charm mesons are excellent probes for studying the properties of the hot and dense medium created in heavy-ion collisions. The measurement of their nuclear modification factor, elliptic and triangular flow can provide strong constraints for the mechanisms of in-medium energy loss. In this talk, the latest measurements of the $D^0$ in PbPb collisions at 5.02 TeV will be presented.
Heavy quarks (charm and beauty) are effective probes of the properties of the Quark-Gluon Plasma (QGP) formed in high-energy heavy-ion collisions at the LHC. Produced mainly in initial hard parton scatterings on shorter time scales compared to the QGP formation time, they witness the full evolution of the system, interacting with the medium constituents and losing energy. The measurement of...
A rich set of open heavy flavour states is observed by LHCb in pPb collisions data collected at 5 and 8.16 TeV nucleon-nucleon center-of-mass energy. Results include the new measurements of production of beauty hadrons in pA collisions through cleanly reconstructed exclusive decays. Open charm states include the Lambda_c baryon, that was also observed in pA collisions for the first time by LHCb.
The relative yields and the nuclear modification factors of the ground and excited Upsilon states were measured via dimuon channels in PbPb collisions at 5.02 TeV. The analysis was performed as functions of collision centrality, rapidity, and transverse momentum. The results in PbPb are compared with the previous ones in pPb collisions. The results are discussed in terms of the sequential...
Beauty quark production in heavy-ion collisions is considered to be one of the key measurements to address the flavour-dependence of in-medium energy loss in heavy-ion collisions. On the other hand, the measurement of the production of strange beauty mesons can provide fundamental insights into the relevance of mechanisms of beauty recombination in the quark-gluon plasma. In this talk, we will...
The measurement of strangeness production is one of the powerful tools to study the thermal properties of the QGP and while strangeness enhancement is a well established experimental observation in heavy ion collisions, its interpretation is still debated.
In particular the study of (multi-)strangeness particle production as a function of the event multiplicity in different collision...
Anisotropic flow plays a critical role in understanding the properties of the quark-gluon plasma. In this talk we present the elliptic and triangular flow of identified particles in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The measurements are presented at mid-rapidity for a wide range of particle transverse momenta. The results are compared to those for elliptic and triangular...
Elliptic flow of direct photons in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV from ALICE
Direct photons are produced in all stages of a ultrarelativistic heavy-ion collisions and are sensitive to details of the space-time evolution of the produced medium. The low ${\textit p}_{\rm T}$ part of the direct photon spectrum is expected to be dominated by thermal direct photons - thermal...
HYDJET++ model combines the description of soft processes with the treatment of hard partons propagating medium. The model is employed for the analysis of PbPb collisions at LHC energies, particularly, the azimuthal anisotropy phenomena, flow, femtoscopy, hard probes. The influence of geometric and dynamical anisotropies on the development of flow harmonics and, simultaneously, on the second-...
Recent observations at RHIC and the LHC of two- and multi-particle correlations in high multiplicity relativistic proton-proton and proton-ion collisions and similarity of the results to those observed in central heavy-ion collisions are often interpreted as an evidence for collective particle production in small collision systems. These results motivate a study in even smaller systems, such...
The azimuthal anisotropies of particle yields observed in relativistic
heavy-ion collisions have been traditionally considered as a strong
evidence of the formation on a deconfined quark-gluon plasma produced in
these collisions. However multiple recent measurements from the ATLAS
Collaboration in pp and p+Pb systems show similar features as those
observed in Pb+Pb collisions, indicating...
First results on two-particle angular correlations for charged particles emitted in $e^+e^-$ collisions using 730 $pb^{-1}$ of data collected between 91 and 209 GeV with the ALEPH detector at LEP are presented. With the archived data, the correlation functions are studied over a broad range of pseudorapidity $\eta$ (rapidity $y$) and azimuthal angle $\phi$ with respect to the electron-positron...
The NICA (Nuclotron-based Ion Collider fAcility) project is under realization at the Joint Institute for Nuclear Research (JINR, Dubna). The main goal of the project is an experimental study of hot and dense strongly interacting matter in heavy ion (up to Au) collisions at center-of-mass energies up to 11 GeV per nucleon. The physics program will be performed at two experiments, BM@N...
LHCb has the unique capability to study collisions of the LHC beams on fixed targets. Internal gas targets of Helium, Neon and Argon have been used so far. Updated results and prospects on soft particle production and open and hidden charm productions will be presented. The measurements are of great interest to cosmic ray physics. The charm production measurements provide crucial constraints...
The exploration of the QCD phase diagram (T-$\mu_{B}$) particularly the search for a phase transition from hadronic to partonic degrees of freedom and the QCD critical point is one of the most challenging theoretical and experimental tasks in present heavy ion physics. Unfortunately the QCD predictions are to a large extent qualitative, as QCD phenomenology at finite temperature and baryon...
Energy-frontier DIS can be realised at CERN through an energy recovery linac that would produce 60 GeV electrons to collide with the HL-LHC or later HE-LHC (LHeC) or eventually the FCC hadron beams (FCC-eh). It would deliver electron-lead collisions with centre-of-mass energies in the range 0.8-2.2 TeV per nucleon, and luminosities exceeding $5\times 10^{32}$ cm$^{−2}$s$^{−1}$. In this talk we...
We review the physics opportunities [1] which are offered by a next generation and multi-purpose fixed-target program exploiting the LHC beams in order to study $pp$, $pd$ and $pA$ collisions at $\sqrt{s_{NN}} \sim 115$ GeV as well as Pb$p$ and Pb$A$ collisions at $\sqrt{s_{NN}} \sim 72$ GeV. These opportunities span spin, heavy-ion, nucleon-structure and astroparticle physics.
We propose two...
LHCb offers the opportunity to perform unique correlation and production measurements at forward rapidity beyond the heavy-flavour sector: direct photons can be reconstructed with good resolution via conversions in the material of the detector, primary tracks can be exploited to perform precise correlation measurements. Recent measurements including the nuclear modification factor of isolated...
Relativistic heavy-ion collision events containing rare final states
involving high transverse momentum objects provide in situ probe which
allow characterization of the hot, dense QCD matter formed in these
collisions. When compared with comparable yields in proton-lead and
proton-proton collisions, hadronic jets and quarkonia (both for charm
and bottom quarks) are observed to have...
The exclusive photoproduction of the heavy vector mesons
J/ψ
is investigated in the context of
peripheral lead-lead collisions for the energies available at the LHC,
√
s
= 2
.
76
TeV and
√
s
= 5
.
02
TeV. In order to evaluate the robustness of the light-cone color dipole formalism, previously tested
in the ultraperipheral regime, it was calculated the rapidity distribution as well as the...
We compute the prompt photon production by gluon fusion and the v2 harmonic coefficient for a the magnetized medium created in heavy-ion collisions. Our calculation is based in the existence of very intense magnetic fields at the early times of the collisions which varies from 1 to 3 times pion mass squared, and open new channels to the photon production. Our calculation take into account...
The exploration of QCD phase diagram and study of the dynamics and mechanism of particle production in heavy-ion collisions is one of the research interests in the field of high energy physics. In addition, the search for the QCD critical point in the phase diagram has been the main motivation to carry out the Beam Energy Scan Phase - I (BES-I) program at the Relativistic Heavy Ion Collider...
The critical phenomena of strongly interacting matter are presented in the random fluctuation walk model at finite temperature. The phase transitions are considered in systems where the Critical Point (CP) is a distinct singular one existence of which is dictated by the dynamics of conformal symmetry breaking.
The physical approach to the effective CP is predicted through the influence...
Particle production at LHC energies involves perturbative (hard) and non-perturbative (soft) QCD regimes. The charged-particle multiplicity cannot be calculated using purely perturbative methods and is generally described by phenomenological models. In this contribution, we report on soft QCD variables, such as inelastic, single, double and central diffractive cross-sections, charged-particle...
The LHC heavy-ion physics programme aims at investigating the fundamental properties of nuclear matter under extreme conditions of energy density and temperature, where a transition to a Quark-Gluon Plasma (QGP) is expected. Jets, the sprays of hadrons resulting from the fragmentation of high-energy partons, are one of the most powerful probes for QGP transport properties, due to the...
Spin alignment of K$^{*0}$ vector mesons produced in non-central heavy-ion collisions could occur due to the presence of large angular momentum and large magnetic field expected in the initial stages of the collisions. This phenomenon leads to a non-uniform angular distribution of the decay daughters of K$^{*0}$ with respect to its quantization axis in the rest frame of K$^{*0}$. This...
Yields of W and Z bosons can be used to probe the nuclear parton distribution functions of quarks and antiquarks. Results on W boson and Drell-Yan production in pPb collisions using the CMS detector will be presented. The lepton decay channel is used to study both positive and negative W bosons as a function of lepton pseudorapidity. Rapidity and charge asymmetries in the W yield are studied....
Low-mass dielectron pairs are unique experimental tool for the studies of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions at the LHC. Such pairs are produced during all stages of the collision and carry the information about the whole space-time evolution of the system unperturbed by final-state interactions. The dielectron continuum is very rich in physics...
The charged-particle transverse momentum spectrum in pp collisions is an important observable for testing perturbative QCD calculations and serves as a reference for heavy-ion collisions to study the properties of deconfined matter created in nucleus-nucleus (AA) collisions. The study of inclusive charged particle spectra gives information on parton energy loss in the medium created in AA...
