Document Type
Report
Publication Date
2020
Pages
1-12
Abstract
Experiment E12-06-106 (RG-D) aims to study the color transparency (CT) phenomenon in the exclusive diffractive p⁰ electro-production off nuclei, using the CLAS-12 spectrometer in Hall-B. This experiment was endorsed by PAC30 back in 2006 and was reviewed by PAC36 in 2010 [1], at which time it was approved for 60 PAC days and granted the B+ rating.
CT is one of the underlying properties of Quantum Chromo Dynamics (QCD) related to the presence of color degrees of freedom in the strongly interacting matter. It refers to the suppression of interactions of the colorless small size configuration in the nuclear medium at high momentum transfer. This compact configuration exhibits very small cross sections due to the cancellation of the color fields between its quarks, thus it is expected to travel through the nucleus experiencing reduced attenuation. Furthermore, the experimental signature of CT is the significat rise of the nuclear transparency, TA, defined as the ratio of the cross section per nucleon on a bound nucleon to that on a free nucleon, with the four momentum transfer squared (Q²) involved in the reaction.
CT has previously been observed at high energies, and its onset was recently reported at lower Q² in both 6GeV JLab experiments of pion [2] and p⁰ [3] electro-production in Hall-C and Hall-B, respectively. Probing the CT effects in meson production is crucial for understanding the dynamical evolution from these exotic short-lived configurations into ordinary hadrons, and thus validates the QCD factorization theorem that is important for accessing Generalized Parton Distributions in deep exclusive meson processes.
The proposed measurements with an 11 GeV electron beam energy intend to study CT effects at fixed coherence length¹ and extend the Q² range up to 5.5 (GeV/c)², which will allow for significant increase in the momentum and energy transfer to produce smaller configurations that live longer and escape the nuclear medium intact. Therefore, we request 60 PAC days to study the Q²-dependence of the nuclear transparency off the nuclei ¹²C, ⁶³Cu, ¹¹⁸SN, and Deuterium. This beamtime was confirmed with a more realistic simulation that has been performed using the CLAS12 GEant-4 Monte-Carlo package (GEMC) and a new target assembly that is currently built by the Hall-B engineers.
Rights
© 2020 The Authors and Thomas Jefferson National Accelerator Facility. All Rights Reserved.
Included with the permission of the author, in accordance with the policy of the copyright holders.
Original Publication Citation
Armstrong, W., Ayerbe, C., Brooks, W., Chetry, T., Dupré, R., Dutta, D., El Alaoui, A., El Fassi, L., Joosten, S., Kim, J., Hafidi, K., Hattawy, M., Holtrop, M., López, J., Meziani, Z.-E., Mineeva, T., Mustapha, B., Peng, C., Weinstein, L., & Xie, J. (2020). Jeopardy update on E12-06-106: RG-D experiment study of color transparency in exclusive vector meson electroproduction off nuclei (Report No.E12-06-106). Thomas Jefferson National Accelerator Facility. https://www.jlab.org/exp_prog/proposals/20/Jeopardy/Run%20Group%20D_Update.pdf
ORCID
0000-0003-2086-2807 (Hattawy)
Repository Citation
Armstrong, W.; Ayerbe, C.; Brooks, W.; Chetry, T.; Dupré, R.; Dutta, D.; El Alaoui, A.; El Fassi, L.; Joosten, S.; Kim, J.; Hafidi, K.; Hattawy, M.; Holtrop, M.; Lopez, J.; Meziani, Z. -E.; Mineeva, T.; Mustapha, B.; Peng, C.; Weinstein, L.; and Xie, J., "Jeopardy Update on E12-06-106: RG-D Experiment Study of Color Transparency in Exclusive Vector Meson Electroproduction off Nuclei" (2020). Physics Faculty Publications. 912.
https://digitalcommons.odu.edu/physics_fac_pubs/912
Comments
For the CLAS Collaboration.