[Halld-physics] Hadron 2019 abstract

[Sean Dobbs]

Dear Colleagues,

I also to submit the following abstract to HADRON 2019.  Please let me
know if you have any comments by tomorrow.

Cheers,
Sean


Title:  First measurement of near-threshold J/ψ photoproduction

Abstract:
Photoproduction of charmonium near threshold gives an excellent probe
for studying the gluonic structure of the nucleon.  Of more recent
interest is the possibility of producing the Pc+ pentaquark candidates
reported by LHCb in the s-channel reaction:  gamma p -> Pc+ -> p
J/psi.  We report on the measurement of the total cross section
sigma(gamma p -> p J/psi) in 10 bins of photon beam energy down to the
threshold of E_\gamma = 8.2 GeV using a tagged photon beam with the
GlueX experiment at Jefferson Lab.  We find the cross section as a
function of beam energy to fall less steeply near threshold than
expectations from lowest-order calculations.  We also find no evidence
for the photoproduction of the Pc states and set upper limits on their
production and Br(Pc -> J/psi p).  We will also discuss the future
prospects for extending these measurements at GlueX.