Orateur
Description
In this contribution I would like to report on our recent computations [1] of exclusive $\chi_c$ productions in high-energy electron-proton collisions. $\chi_c$ quarkonia are $C$-even and serve as a probe of the odderon amplitude in the proton which is an off-forward generalized transverse momentum distribution formed by at least three gluons in a $C$-odd state. We are motivated by the odderon discovery of the TOTEM and D0 collaborations [2,3] in $pp$ vs $p\bar{p}$ elastic collisions. Our main goal is to investigate the potential for the odderon detection at the future EIC. The computation is based on the Color Glass Condensate framework, where we numerically solve the Balitsky-Kovchegov evolution equation for coupled pomeron-odderon system [4]. Our initial conditions are based on a microscopic quark model computation [5] that is an essential for a proper account of the so-called Donnachie-Landshoff mechanism according to which even a large-$|t|$ scattering would not break up the proton if it involves a three-gluon exchange. Our comprehensive results cover the exclusive production of the complete $\chi_{cJ}$ family ($J = 0, 1, 2$) [1]. In our computation we pay special attention to the interference with the Primakoff process where our model computation predicts a constructive interference of the odderon and the Primakoff contributions. We find that while the Primakoff component in the total cross section dominates the low-$|t|$ region, the odderon takes over at moderate $|t| \approx 1$ GeV$^2$. Thanks to the constructive interference of the odderon and the photon we find an excess of events with respect to the Primakoff background in the moderate $|t|$ range. Our estimates suggest about a dozen $\chi_c$ events per month from the $\chi_c \to J/\psi+\gamma$ decay channel and at the top EIC energy.
[1] SB, A. Dumitru, A. Kaushik, L. Motyka, T. Stebel, in preparation
[2] TOTEM collaboration, Eur. Phys. J. C 80, 91 (2020)
[3] D0 collaboration, Phys. Rev. D 86, 012009 (2012)
[4] SB, D. Horvatic, A. Kaushik, E. A. Vivoda, Phys. Rev. D 108 (2023) 7, 074005
[5] A. Dumitru, H. Mantysaari, R. Paatelainen, Phys. Rev. D 107, L011501 (2023)
