Tue·Sep 12, 2023Tuesday·September 12, 2023

1. 01*

   Thermal photon measurements at PHENIX

   Roli Esha (for the PHENIX Collaboration)🇺🇸

   Photons are emitted at all stages of relativistic heavy-ion collisions and do not interact with the medium strongly. With access to the versatility of RHIC, measurements of low momentum direct photons are made possible across different system size and beam energies. An excess of direct photons, above prompt photon production from hard scattering processes, is observed for a system size corresponding to $d{N}_{ch}/d\eta$ of 20-30, with a large azimuthal anisotropy and a characteristic dependence on collision centrality. After subtracting the prompt photon component, the inverse slope of the spectrum is continuously increasing with the effective temperature ranging from 250 MeV/c at $p_T$ of 1-2 GeV/c to about 400 MeV/c at 2-4 GeV/c. Within the experimental uncertainty, there is no indication of a system size dependence of the inverse slope. In this proceeding, results from Au+Au collisions from the PHENIX experiment will be presented.

   nucl-exPoS(2024)·1 citation
2. 02*

   Spin decoherence and off-resonance behavior of radiofrequency-driven spin rotations in storage rings

   N.N. Nikolaev🇷🇺 · F. Rathmann🇩🇪 · J. Slim🇩🇪 · A. Andres🇩🇪 · V. Hejny🇩🇪 · A. Nass🇩🇪 · A. Kacharava🇩🇪 · P. Lenisa🇮🇹 · J. Pretz🇩🇪 · A. Saleev🇮🇹 · V. Shmakova🇮🇹 · H. Soltner🇩🇪 and 51 other authors

   Radiofrequency-driven resonant spin rotators are routinely used as standard instruments in polarization experiments in particle and nuclear physics. Maintaining the continuous exact parametric spin-resonance condition of the equality of the spin rotator and the spin precession frequency during operation constitutes one of the challenges. We present a detailed analytic description of the impact of detuning the exact spin resonance on the vertical and the in-plane precessing components of the polarization. An important part of the formalism presented here is the consideration of experimentally relevant spin-decoherence effects. We discuss applications of the developed formalism to the interpretation of the experimental data on the novel pilot bunch approach to control the spin-resonance condition during the operation of the radiofrequency-driven Wien filter that is used as a spin rotator in the first direct deuteron electric dipole moment measurement at COSY. We emphasize the potential importance of the hitherto unexplored phase of the envelope of the horizontal polarization as an indicator of the stability of the radiofrequency-driven spin rotations in storage rings. The work presented here serves as a satellite publication to the work published concurrently on the proof of principle experiment about the so-called pilot bunch approach that was developed to provide co-magnetometry for the deuteron electric dipole moment experiment at COSY.

   ↳ physics.acc-phhep-exnucl-exPhys.Rev.Accel.Beams(2024)·7 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.