Document Type
Report
Publication Date
2016
Pages
1-23
Abstract
We propose to measure the photo-production cross section of J/Ψ near threshold in search of the recently observed LHCb hidden charm resonances Pc(4380) and Pc(4450) consistent with "pentaquarks." The observation of these resonances in photo-production is important to differentiate the true resonance nature of the LHCb states from kinematics enhancements. The bremsstrahlung photon beam produced with an 11 GeV electron beam at CEBAF enables us to cover the energy range of J/Ψ production from the threshold photo-production energy of 8.2 GeV to an energy beyond the presumed Pc(4450) resonance production. The proposed experiment will be carried out in Hall C using a 50 μA incident electron beam current striking a 9% copper radiator that will produce a bremsstrahlung photon beam passing through a 15 cm liquid hydrogen target and producing J/Ψ mesons, either through a diffractive process in the t-channel or a resonant process through the s- and u-channel. The decay e+e- pairs of the J/Ψ will be detected in coincidence using the two high momentum spectrometers of Hall C, namely the existing HMS and the newly built SHMS. The SHMS will be set at 34.5° in order to detect the corresponding electrons of these pairs.
The settings were optimized to distinguish the resonance s- and u-channel production from its diffractive t-channel production of the J/Ψ. Compared to the t-channel production of the J/Ψ, the s- and u-channel production of the charmed 5-quark resonance appears to dominate the t distribution at large t. Furthermore, the momentum and angular resolution of the spectrometers allow the reconstruction of the photon energy and the Mandelstam variable t with a resolution sufficient to observe a clear resonant enhancement in the total cross section or the t distribution as shown in the projected results. This setup is also optimized to minimize the absolute rate of leptons in both spectrometers and thus the rate of accidental coincidences between the two spectrometers.
We request a total of 11 days of beam time with 9 days to carry the bulk of the proposed experiment and 2 days to acquire the needed t-channel elastic J/Ψ production data for a calibration measurement. This calibration measurement in itself will greatly enhance our knowledge of t-channel elastic J/Ψ production near threshold.
Rights
© 2016 The Authors and Thomas Jefferson National Accelerator Facility.
Included with the kind written permission of the author, in accordance with copyright holder policy.
Original Publication Citation
Asaturyan, A., Mkrtchyan, H., Tadevosyan, V., Zhamkochyan, S., Arrington, J., Armstrong, W., Hafidi, K., Hattawy, M., Ye, Z., Aniol, K., Gao, H., Zhao, Z., Liu, T., Yan, X., Gu, C., Peng, C., Li, X., Xiong, W., Markowitz, P.,…Wood, S. (2016). A search for the LHCb charmed pentaquark using photoproduction of J/Ψ at Threshold in Hall C at Jefferson Lab (Report No. NASA/CR-2018-220043). Thomas Jefferson National Accelerator Facility.
ORCID
0000-0003-2086-2807 (Hattawy)
Repository Citation
Asaturyan, A.; Mkrtchyan, H.; Tadevosyan, T.; Zhamkochyan, S.; Arrington, J.; Armstrong, W.; Hafidi, K.; Hattawy, M.; Ye, Z.; Aniol, K.; Gao, H.; Zhao, Z.; Liu, T.; Yan, X.; Gu, C.; Peng, C.; Li, X.; Xiong, W.; Markowitz, P.; Adhikari, K.; Bhatt, H.; Bhetuwal, D.; Dunne, J.; Dutta, D.; El-Fassi, L.; Ye, L.; Wesselmann, F. R.; Chen, X.; Fu, Q.; Wang, R.; Zhang, Y.; Zhao, F.; Dupré, R.; Huber, G. M.; Li, W.; Zafar, A.; Bae, S.; Choi, H.; Choi, S.; Go, H.; Ha, J.; Atac, H.; Duran, B.; Joosten, S.; Meziani, Z.-E.; Paolone, M.; Rehfuss, M.; Sparveris, N.; Chen, J.-P.; Chudakov, E.; Diefenthaler, M.; Hansen, O.; Higinbotham, D.; Jones, M.; Meekins, D.; Pentchev, L.; Pooser, E.; and Wood, S., "A Search for the LHCb Charmed "Pentaquark" Using Photoproduction of J/Ψ at Threshold in Hall C at Jefferson Lab" (2016). Physics Faculty Publications. 909.
https://digitalcommons.odu.edu/physics_fac_pubs/909
Comments
An experiment proposal to JLab-PAC44.