JOB DESCRIPTION

We invite applications for a highly motivated post-doctoral researcher for a 2-year duration to work on the study of quarkonium photoproduction in peripheral to central Pb-Pb collisions with Run3 data in ALICE. The candidate will work on the analysis of the photoproduced J/psi polarization in peripheral Pb-Pb collisions, in the dimuon decay channel, with the ALICE forward muon spectrometer. Benefiting from the high statistics to be collected in 2022, the candidate will also extend the current J/psi photoproduction cross section measurements toward most central collisions, and to other quarkonia (Psi(2S), Ups(1S)) if feasible. 

The researcher will be based at IJCLab, Orsay, France in the ALICE group with frequent travels to CERN. The position is funded for two years and can be filled as soon as 1st. November 2022. 

DESCRIPTION OF THE PROJECT

The project concerns the analysis of ALICE Run3 data. ALICE offers unique capabilities to study quarkonium production at low transverse momentum over a wide rapidity range. In ultra-peripheral collisions (UPC), nuclei are separated by impact parameters larger than the sum of their radii and therefore hadronic interactions are strongly suppressed. Photoproduction of vector mesons, in such collisions, gives insight into the gluon distribution of the incoming Pb nuclei over a broad range of Bjorken-x values. The first indication of J/psi coherent photoproduction measured by ALICE [1] at forward rapidity in Peripheral Collisions (PC) with nuclear overlap brings yet another handle to this kind of measurements. The experimental and theoretical challenges of quarkonium photoproduction measurements in AA collisions with nuclear overlap, are still manyfold. Indeed, the observed J/psi excess at low transverse momentum (pT), interpreted as originating from coherent photoproduction, imposes great challenges for the existing coherent photoproduction models, especially in explaining how the broken nuclei satisfy the requirement of coherence. The high statistics Pb-Pb data foreseen in Run3 will permit the measurement for the first time of the J/psi excess polarization allowing one to confirm the photoproduction origin of the excess. The measurement of the excess in thin centrality intervals will be conducted at forward rapidity, to study potential QGP-like effects on the photoproduced J/psi yield. If statistics allow, the previous studies will be extended to other quarkonia for the first time.

The ALICE IJCLab group is composed of 5 permanent researchers, 2 PhD students, and 1 postdoc. We are deeply involved in quarkonium analyses at forward rapidity in all colliding systems, as well as in heavy flavor production and Z boson production. The group is responsible for and built the first tracking station of the muon spectrometer. During LS2, the group was strongly involved in the upgrade of the muon tracking chamber electronics. 

The post-doctoral position is part of the broader local 4-year research program “Gluodynamics” from the P2IO labex, which aims at : i.) the investigation of the QCD force and radiation within QCD fluids ; ii.) the understanding of the nucleon and nuclear geometry and the conceptual and practical connections between this and the hot QCD fields of research ; iii.) the development of future projects for QCD research at the LHC and at the EIC.

EXPECTED PROFILE

Applicants are expected to hold a PhD degree in subatomic physics or in a related field. Good programming and computational skills are required. In particular, experience in simulations and data analysis, in a large experimental collaboration, will be considered a plus. The eligible candidate should be able to communicate at a scientific level in English. Knowledge of French, although not essential, would be useful. The University of Paris-Saclay is an equal opportunity/affirmative action employer.

The appointment is for two years (P2IO labex funding). To be eligible, applicants must have obtained their PhD degree by the date of appointment and preferentially no more than 2 years ago, at the start of the contract (applicants with a PhD obtained no more than 5 years ago would however still be considered).

Monthly gross salary will be between €2744 and €3161, depending on the candidate experience. It corresponds to a net salary before income tax ranging from €2200 to €2535. 

APPLICATION: 

The applications (including a CV, a statement of research, a cover letter) are to be sent to: 

Laure Massacrier - laure.massacrier@ijclab.in2p3.fr 

Cynthia Hadjidakis - cynthia.hadjidakis@ijclab.in2p3.fr 

The applicants should arrange 3 letters of recommendation to be sent separately at the same address.

In addition, an online application needs to be filled at the following link: https://emploi.cnrs.fr/Offres/CDD/UMR9012-MARLOU-023/Default.aspx?lang=EN

For further information please contact Laure Massacrier and Cynthia Hadjidakis. 

LABORATORIES INVOLVED

Laboratoire de Physique des 2 infinis Irène Joliot-Curie (IJCLab)

15, Rue G. Clemenceau

91405 ORSAY cedex (FRANCE) 

REFERENCES 

[1] Measurement of an excess in the yield of J/ψ at very low pT in Pb-Pb collisions at √sNN = 2.76 TeV

By J. Adam et al., Phys. Rev. Lett., 116(22):222301, 2016.