A Search for the LHCb Charmed 'Pentaquark' using Photo-Production of $J/{\psi}$ at Threshold in Hall C at Jefferson Lab
| Autor: | Meziani, Z. -E., Joosten, S., Paolone, M., Chudakov, E., Jones, M., Adhikari, K., Aniol, K., Armstrong, W., Arrington, J., Asaturyan, A., Atac, H., Bae, S., Bhatt, H., Bhetuwal, D., Chen, J. -P., Chen, X., Choi, H., Choi, S., Diefenthaler, M., Dunne, J., Dupré, R., Duran, B., Dutta, D., El-Fassi, L., Fu, Q., Gao, H., Go, H., Gu, C., Ha, J., Hafidi, K., Hansen, O., Hattawy, M., Higinbotham, D., Huber, G. M., Markowitz, P., Meekins, D., Mkrtchyan, H., Nouicer, R., Li, W., Li, X., Liu, T., Peng, C., Pentchev, L., Pooser, E., Rehfuss, M., Sparveris, N., Tadevosyan, V., Wang, R., Wesselmann, F. R., Wood, S., Xiong, W., Yan, X., Ye, L., Ye, Z., Zafar, A., Zhang, Y., Zhao, F., Zhao, Z., Zhamkochyana, S. |
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| Rok vydání: | 2016 |
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| Druh dokumentu: | Working Paper |
| Popis: | We propose to measure the photo-production cross section of $J/{\psi}$ near threshold, in search of the recently observed LHCb hidden-charm resonances $P_c$(4380) and $P_c$(4450) consistent with 'pentaquarks'. The observation of these resonances in photo-production will provide strong evidence of the true resonance nature of the LHCb states, distinguishing them from kinematic enhancements. A bremsstrahlung photon beam produced with an 11 GeV electron beam at CEBAF covers the energy range of $J/{\psi}$ production from the threshold photo-production energy of 8.2 GeV, to an energy beyond the presumed $P_c$(4450) resonance. The experiment will be carried out in Hall C at Jefferson Lab using a 50{\mu}A electron beam incident on a 9% copper radiator. The resulting photon beam passes through a 15 cm liquid hydrogen target, producing $J/{\psi}$ mesons through a diffractive process in the $t$-channel, or through a resonant process in the $s$- and $u$-channel. The decay $e^+e^-$ pair of the $J/{\psi}$ will be detected in coincidence using the two high-momentum spectrometers of Hall C. The spectrometer settings have been optimized to distinguish the resonant $s$- and $u$-channel production from the diffractive $t$-channel $J/{\psi}$ production. The $s$- and $u$-channel production of the charmed 5-quark resonance dominates the $t$-distribution at large $t$. The momentum and angular resolution of the spectrometers is sufficient to observe a clear resonance enhancement in the total cross section and $t$-distribution. We request a total of 11 days of beam time with 9 days to carry the main experiment and 2 days to acquire the needed $t$-channel elastic $J/{\psi}$ production data for a calibration measurement. This calibration measurement in itself will greatly enhance our knowledge of $t$-channel elastic $J/{\psi}$ production near threshold. Comment: This document is an updated version of the original proposal PR12-16-007, which was approved with an 'A' rating and a 'high-impact' label by the Jefferson Lab PAC 44 in July 2016. The experiment was awarded 11 days of beam time |
| Databáze: | arXiv |
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