Post-doctoral researcher in Accelerator Physics : Sensitivity studies for the Compton polarimeters of FCCee beam energy calibration (M/F)

Job Description

Missions

The Future Circular Collider of positron and electron beams is a Higgs factory planned at CERN. It will also produce a copious amount of electroweak bosons. In particular, the success of the electroweak measurements program at the Z boson pole requires excellent control of the beam energy with a relative precision of 10-6. This will be achieved with the resonant depolarization procedure, which exploits the existence of depolarizing resonances at specific energy values related to spin dynamics in a circular accelerator. Polarized electron and positron bunches will be specifically used for this purpose. They will be scanned to search for these resonances, and their polarization will be measured at the same time to find specific points where the beam polarization is significantly degraded. Regular measurements will thus be carried out to track beam energy fluctuations, for example induced by tidal forces. To this end, it will be necessary to integrate polarimeters, using the Compton process, for each beam. The Accelerator Pole ILE group is involved in their design and plays a major role in it. A preliminary concept has been presented and seems to allow polarization measurement with an accuracy of the order of parts per thousand or better, which should be sufficient to achieve the targeted precision in beam energy measurement. It has also been demonstrated that Compton polarimeters can be directly used to measure the residual longitudinal polarization of beams with a similar precision, an uncertainty that contributes to the systematic uncertainty in electroweak asymmetry measurements. Furthermore, they can be used to directly measure beam energy with an accuracy of the order of 10-4 by measuring the position of particles scattered by the Compton interaction. This will provide complementary information with the resonant depolarization technique and will be particularly interesting at higher beam energies for which the resonant depolarization technique cannot be applied. Precise studies of systematic uncertainties are necessary to establish the detector's performance.
The fixed-term researcher will work under supervision of Aurélien MARTENS in the ILE group of Accelerator pole and in close collaboration with a PhD student at IJCLab, and external collaborators..
References: N.Yu. Muchnoi 2022 JINST 17 P10014
A. Martens et al 2023 JINST 18
A. Blondel et al. arXiv: 1909:12245

Activity

The main activity and responsibility of the IJCLab group is to provide the detailed sensitivity study and polarisation extraction from simulations. The researcher will use standalone simulation and develop the studies to provide systematics and detailed studies of many potential limiations. Simulation of background and their impact on the extraction will be part of the work. This will be done in collaboration with the current PhD student (thesis to be defened in Oct 2027), to take over this work to provide a list of main systematic uncertainties for the measurement. All of these efforts will be carried out in collaboration with colleagues from CERN. Existing collaboration with partner in IHEP, will allow, depending on the motivation of the candidate, and beam availability to take part in experiments at BEPC2 to measure polarisation with pixel sensors in IHEP, the foreseen technology for FCC-ee detectors for the Compton polarimeter. This activity will be complemented by experimental developments aiming to control the optical polarization with extreme precision, better than parts per thousand. Indeed, this is a limiting systematic uncertainty for precision Compton polarimetry measurements. These efforts will involve developing an optical test bench and demonstrating the feasibility of real-time optical polarization diagnostics. The results obtained will be regularly presented at meetings of the FCC-ee EPOL group. Depending on the profile and interests of the candidate, she/he might contribute to some preparation of sensitivity studies for analysis of tau decays at FCC-ee.
Weekly meetings (or more frequent if necessary) will be organized to monitor and resolve encountered difficulties.

Your Profil

Skills

The candidate must hold a PhD in instrumentation or subatomic physics, with a willingness to work mainly on simulations. Interest in performing experiments (laser and/or detectors for accelerators) is a plus. Knowledge of detector physics, accelerator physics, and/or particle physics is a plus. Expertise in instrumentation is interesting but not critical for the envisioned work. Programming experience is also beneficial. Excellent written and spoken English is required; knowledge of French is a plus but not necessary. We are looking for a curious individual capable of tackling a variety of physics questions at the interface of particle physics and detectors. The recruited individual will work with remote collaborators, process numerous sets of simulated data, and be required to report their work concisely. They must also be autonomous in their daily work.

Your Work Environment

The Irène Joliot-Curie Physics Laboratory of 2 Infinities (IJCLab) is a UMR under the supervision of the CNRS (IN2P3), the University of Paris-Saclay and the University of Paris is located on the campus of the University of Paris -Saclay in Orsay. The laboratory is located on the campus of the Université Paris-Sud, Université Paris-Saclay in Orsay. The campus is located 20 km south of Paris and easily accessible by RER in 35 minutes.
IJCLab was born in 2020 from the merger of five units (CSNSM, IMNC, IPN, LAL, LPT). The staff is made up of nearly 560 permanent (340 engineers, technicians and administrators and 220 researchers and teacher-researchers) and approximately 200 non-permanent including 120 doctoral students. The research themes of the laboratory are nuclear physics, high energy physics, theoretical physics, astroparticles, astrophysics and cosmology, particle accelerators, energy and the environment and health. IJCLab has very significant technical capacities (around 280 IT) in all the major fields required to design, develop / implement the experimental devices necessary for its scientific activity, as well as the design, development and use of instruments. .
The researcher will work within the ILE group (4 faculty researchers, 3 CNRS researchers, 2 PhD students) of the accelerator physics department, which has developed expertise over more than twenty years in Compton interaction for the production of high-energy photons, ranging from tens of keV for medical and imaging applications, to a few MeV for nuclear physics, and several GeV for electron beam diagnostics for particle physics colliders. A significant part of the activities focuses on designing systems for precise diagnostics of electron beam polarization. The proposed work will thus fully align with the group's scientific objectives.
IJCLAB bases its recruitment policy on the promotion of equality, diversity and inclusion. Essential values, they allow the professional development of agents, who are real actors in a collective success, but also the development of the laboratory itself.

Compensation and benefits

Compensation

Between €3,131.32 and €3,569.85 gross per month, depending on experience.

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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