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J. Lajoie

Publications and source records attributed to J. Lajoie.

4 recordsLinked to original sources

2025 EIC-France Workshop: Physics Highlights and Perspectives

This document presents a synthesis of the theory contributions and discussions from the 2nd EIC-France Workshop, held at IJCLab (Orsay) on 1-3 December 2025. The workshop brought together members of the French hadron-physics community to review recent theoretical developments relevant to the future Electron-Ion Collider (EIC) and to coordinate national efforts in preparation for its early physics program. The report first summarizes the collider's initial running conditions and luminosity performance, as outlined in the EIC Early Science Matrix. It then provides concise overviews of the theoretical presentations on inclusive, semi-inclusive, exclusive, heavy-flavor, and small-x physics. Based on these discussions, two measurements emerged as especially well suited for early EIC operation and strongly aligned with areas of established French expertise: inclusive diffraction and inclusive quarkonium production. These channels offer clean signatures, robust theoretical interpretability, and direct sensitivity to fundamental QCD phenomena such as gluon saturation, heavy-quark dynamics, and the small-x structure of hadrons and nuclei. In addition, the workshop identified longer-term physics opportunities that will benefit from the full capabilities of the EIC after its ramp-up phase. These include accessing the three-dimensional structure of the pion through the Sullivan process and a broader program of exclusive three-body final states, both of which represent high-impact avenues for exploring hadronic structure and non-perturbative QCD. Together, the elements summarized in this report provide a coherent overview of the strategic priorities and scientific ambitions shaping the French community's contribution to the EIC physics program.

hep-ph↗

Design and Simulated Performance of Calorimetry Systems for the ECCE Detector at the Electron Ion Collider

We describe the design and performance the calorimeter systems used in the ECCE detector design to achieve the overall performance specifications cost-effectively with careful consideration of appropriate technical and schedule risks. The calorimeter systems consist of three electromagnetic calorimeters, covering the combined pseudorapdity range from -3.7 to 3.8 and two hadronic calorimeters. Key calorimeter performances which include energy and position resolutions, reconstruction efficiency, and particle identification will be presented.

physics.ins-det↗

A Proposal for the Muon Piston Calorimeter Extension (MPC-EX) to the PHENIX Experiment at RHIC

The PHENIX MPC-EX detector is a Si-W preshower extension to the existing PHENIX Muon Piston Calorimeters (MPC). The MPC-EX will consist of eight layers of alternating W absorber and Si mini-pad sensors and will be installed in time for RHIC Run-15. Covering a large pseudorapidity range, 3.1 < eta < 3.8, the MPC-EX and MPC access high-x partons in the projectile nucleon (and low-x partons in the target nucleon) in p+A and transversely polarized proton-proton collisions at 200 GeV. With the addition of the MPC-EX, the neutral pion reconstruction range extends to energies > 80 GeV, a factor of four improvement over current capabilities. Not only will the MPC-EX strengthen PHENIX's existing forward neutral pion and jet measurements, it also provides the necessary neutral pion rejection to make a prompt photon measurement feasible in both p+A and p+p collisions. With this neutral pion rejection, prompt (direct + fragmentation) photon yields at high p_T, p_T > 3 GeV, can be statistically extracted using a double ratio method. In p+A collisions direct photons at forward rapidities are optimally sensitive to the gluon distribution because, unlike pions, direct photons are only produced by processes that are directly sensitive to the gluon distribution at leading order. A measurement of the forward prompt photon R_pA will cleanly access and greatly expand our understanding of the gluon nuclear parton distribution functions and provide important information about the initial state in heavy ion collisions. In transversely polarized p+p collisions the MPC-EX will make possible a measurement of the prompt photon single spin asymmetry A_N, and will help elucidate the correlation of valence partons in the proton with the proton spin.

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Prompt Photon A_N with the PHENIX MPC-EX Detector

The PHENIX MPC-EX detector is a Si-W preshower extension to the existing Muon Piston Calorimeters (MPC). Covering the pseudorapidity range 3.1 <eta < 3.8, the MPC-EX and MPC access high-x partons in the projectile nucleon The combined detectors will make possible a measurement of the prompt photon single spin asymmetry A_N in 200GeV transversely polarized p+p collisions, which will help elucidate the correlation of the transverse motion of valence partons in the proton with the proton spin.

nucl-ex↗