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Reference : UMR6457-POLGOS-001
Workplace : NANTES
Date of publication : Monday, February 15, 2021
Scientific Responsible name : Pol-Bernard Gossiaux
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
PhD title: “improved theoretical treatment of quarkonia production in ultrarelativistic heavy ion collisions through dynamical recombination”
The context: The interpretation of the ultrarelativisitc heavy ion collision (URHIC) data collected at the CERN and RHIC Collider is the center of interest of the high energy theory group at Subatech. We have developed in the recent years the event generator EPOS3 to study the soft physics as well as EPOS-HQ to study heavy quarks which traverse the plasma of quark and gluons, formed in these reactions. The goal of this approach is to develop a program which reproduces simultaneously the heavy as well as the light quark physics to reduce the uncertainties inherent in this approaches because the underlying theory of strong interactions, the Quantum-Chromo-Dynamics (QCD) can only solved in special cases.
Among various “hard probes” of particular interest is the so called “quarkonia suppression” suggested by Matsui and Satz. Quarkonia are bound states of heavy quarks, stable in the vacuum which would be dissolved at finite temperature when immerged in a quark gluon plasma due to the QCD equivalent of the Debye screening mechanisms. Due to such phenomenon, quarkonia are often referred to as “QGP thermometer”, as various bound states would dissolve at different temperature above the deconfinement temperature Tc. Although this picture is quite appealing, its concrete implementation in numerical models is often performed with pretty crude approximations and assumptions, for instance neglecting finite dynamical time scales inherent to the ultrarelativistic heavy ion collision. In recent years, one has also realized that some quarkonia could be formed at or prior to the transition towards the confined phase by 2 heavy quarks stemming from disconnected origins. This so called “recombination mechanism” is usually modelled assuming quasi-stationary bound states what also constitutes a questionable approximation.
During the last years, we (among some researchers) have started to investigate the feasibility to deal with quarkonia formation in URHIC adopting the viewpoint and concepts of the so-called “open quantum system” (see f.i. ref. [1-3]), which appears to be the correct dynamical framework for such situation. In particular, we were able to treat the somehow simpler case of bottomonia production at the large hadron collider (LHC) where only one beauty-antibeauty pair is considered, with promising perspectives. More recently, we have investigated the question of open-quantum system resorting to Linblad-like equations acting on the operator-density, simplified by resorting to semi-classical approximations . This approach could be quite relevant in order to deal with the production of charmonia in AA collisions, a process which appears to be dominated by the recombination of exogenous pairs happening when the QGP cools down. Oppositely to what is often admitted in the literature, it appears that this recombination process is a rather slow process, requiring energy dissipative exchanges with the heat bath to happen efficiently…
The thesis project: During the PhD thesis, we plan to pursue the investigation of quarkonia production in URHIC resorting to the concepts and methods of open quantum systems. In particular, we will focus our investigations on the topic of the dynamical Q-Qbar confinement that is restored during the cooling down of the QGP, that will be treated in the open-quantum system approach; possibly, the method will be extended to address the question of the hadronization of heavy quarks into open flavor mesons (and hadrons) in order to aim at a universal description,… Apart from theoretical developments, some part of the PhD is expected to be devoted to phenomenological studies on the URHIC studied experimentally at RHIC and LHC colliders. This could encompass some extension to the proton-nucleus case as well. This project offers the possibility to perform significant progresses in this highly debated topic of probing one of the most intriguing state of matter ever discovered by Mankind. It will help the candidate to develop skills both in the field of theoretical nuclear and particle physics, as well as in statistical physics, while being balanced between theoretical developments and numerical investigations. It can thus be considered as a real springboard for the candidate's future career.
Located on the site "La Chantrerie" in the north of Nantes, the SUBAtomics Physics and Associated TECHnologies laboratory (Subatech) is a mixed research unit (UMR 6457) between IMT Atlantique, the University of Nantes and the CNRS/IN2P3. Fully integrated into major global scientific collaborations, Subatech's research activities revolve around the fields of nuclear, hadronic, particle and astroparticle physics, and radiochemistry. Subatech carries out fundamental research and applied research in the fields of energy, environment and health. Mastery of technologies associated with these fields is a key factor for the success of laboratory projects.
The group: The theory group of SUBATECH is composed of 14 permanent senior researchers (among them 9 oriented towards high energy physics), 2 postdocs and 6 PhD students. Further general information can be found on our website http://www-subatech.in2p3.fr.
Constraints and risks
The candidate: We expect from the candidate a solid background in theoretical physics, especially of the different aspects of QCD as well as basic knowledge in numerical physics. Candidates with good knowledge of open quantum systems are encouraged to apply as well, even if they have a less extended background in QCD.
In addition to disciplinary knowledge, the expected skills are: hindsight, ability to carry out long and complex tasks by implementing control processes, spirit of initiative, imagination.
Candidates should post a resume including a transcript of their grades during their master studies, a statement of their research interests and a motivation letter. Candidates for te auditions should be ready to provide two letters of recommendation
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