Document Type

Report

Publication Date

2018

Pages

E12-11-003B (30 pp.)

Abstract

Exclusive, near-threshold quasi-real photoproduction of J/ψ off the deuteron provides attractive opportunities to study interesting physics. Besides studying the gluonic structure of bound nucleons and the deuteron (in coherent production), studying the final-state interactions allows a direct access to the elementary J/ψN cross section. There is one measurement of the near-threshold quasi-elastic J/ψ production off the deuteron, however data on final-state interactions or of the coherent cross section do not exist. With its high luminosity and large acceptance, the CLAS12 detector is well suited to measure near-threshold photoproduction of J/ψ off the deuteron.

This is a proposal to measure the differential cross section of the incoherent and coherent production of J/ψ meson off the deuteron. The reactions yd → J/ψpn and yd → Jψd will be measured in untagged quasi-real photoproduction, where all the final state particles (the nucleon(s) or deuteron, and the lepton pair from the J/ψ decay) are detected and the photon is reconstructed via 4-momentum conservation. The incoherent measurement will provide data on the gluon form factors of bound nucleons and on the J/ψN interaction. The coherent measurement will be the first measurement, albeit with low statistics, of the gluonic structure of the deuteron. The same reactions will also be accessed with the Forward Tagger (FT), where the small-Q² photon kinematics is measured by the FT and all but one final-state particles are detected in the CLAS12.

We will be able to measure J/ψ production off the quasi-free neutron by measuring a high-energy (p > 1 GeV/c) neutron in the CLAS forward calorimeters in the fully exclusive untagged real photoproduction and will be in position to search for isospin partners of the LHCb pentaquarks P⁰c(4380) and P⁰c(4450).

This is a run-group proposal to join Run Group B (RG B). RG B provides a window of opportunity for a first measurement at JLab of these processes. The measurement considered here does not require any additional detection system than already planned for RG B. We will need an additional trigger for charged particles in opposite sectors that will add 20% to the trigger rate. This trigger was tested and used by Run Group A in their 2018 run. The proposal is an extension of the E12-12-001 experiment.

Rights

© 2018 The Authors.

Included with the kind written permission of the author.

Comments

A Run Group B Proposal.

Original Publication Citation

Baker, M. D., Freese, A. J., Guo, L., Hyde, C., Ilieva, Y., McKinnon, B., Nadel-Turonski, P., Sargsian, M., Kubarovsky, V., Stepanyan, S., Zachariou, N., & Zhao, Z. W. (2018). Study of J/ψ photoproduction off deuteron. (Report No. E12-11-003B) . Thomas Jefferson National Accelerator Facility.

ORCID

0000-0001-7282-8120 (Hyde)

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