First Measurement of Near-Threshold J/ψ Exclusive Photoproduction off the Proton

A Ali; M Amaryan; E G Anassontzis; A Austregesilo; M Baalouch; F Barbosa; J Barlow; A Barnes; E Barriga; T D Beattie; V V Berdnikov; T Black; W Boeglin; M Boer; W J Briscoe; T Britton; W K Brooks; B E Cannon; N Cao; E Chudakov; S Cole; O Cortes; V Crede; M M Dalton; T Daniels; A Deur; S Dobbs; A Dolgolenko; R Dotel; M Dugger; R Dzhygadlo; H Egiyan; A Ernst; P Eugenio; C Fanelli; S Fegan; A M Foda; J Foote; J Frye; S Furletov; L Gan; A Gasparian; V Gauzshtein; N Gevorgyan; C Gleason; K Goetzen; A Goncalves; V S Goryachev; L Guo; H Hakobyan; A Hamdi; S Han; J Hardin; G M Huber; A Hurley; D G Ireland; M M Ito; N S Jarvis; R T Jones; V Kakoyan; G Kalicy; M Kamel; C Kourkoumelis; S Kuleshov; I Kuznetsov; I Larin; D Lawrence; D I Lersch; H Li; W Li; B Liu; K Livingston; G J Lolos; V Lyubovitskij; D Mack; H Marukyan; V Matveev; M McCaughan; M McCracken; W McGinley; J McIntyre; C A Meyer; R Miskimen; R E Mitchell; F Mokaya; F Nerling; L Ng; A I Ostrovidov; Z Papandreou; M Patsyuk; P Pauli; R Pedroni; L Pentchev; K J Peters; W Phelps; E Pooser; N Qin; J Reinhold; B G Ritchie; L Robison; D Romanov; C Romero; C Salgado; A M Schertz; R A Schumacher; J Schwiening; K K Seth; X Shen; M R Shepherd; E S Smith; D I Sober; A Somov; S Somov; O Soto; J R Stevens; I I Strakovsky; K Suresh; V Tarasov; S Taylor; A Teymurazyan; A Thiel; G Vasileiadis; D Werthmüller; T Whitlatch; N Wickramaarachchi; M Williams; T Xiao; Y Yang; J Zarling; Z Zhang; G Zhao; Q Zhou; X Zhou; B Zihlmann; GlueX Collaboration

doi:10.1103/PhysRevLett.123.072001

First Measurement of Near-Threshold J/ψ Exclusive Photoproduction off the Proton

Phys Rev Lett. 2019 Aug 16;123(7):072001. doi: 10.1103/PhysRevLett.123.072001.

Authors

A Ali¹, M Amaryan², E G Anassontzis³, A Austregesilo⁴, M Baalouch², F Barbosa⁵, J Barlow⁶, A Barnes⁴, E Barriga⁶, T D Beattie⁷, V V Berdnikov⁸, T Black⁹, W Boeglin¹⁰, M Boer¹¹, W J Briscoe¹², T Britton⁵, W K Brooks¹³, B E Cannon⁶, N Cao¹⁴, E Chudakov⁵, S Cole¹⁵, O Cortes¹², V Crede⁶, M M Dalton⁵, T Daniels⁹, A Deur⁵, S Dobbs⁶, A Dolgolenko¹⁶, R Dotel¹⁰, M Dugger¹⁵, R Dzhygadlo¹, H Egiyan⁵, A Ernst⁶, P Eugenio⁶, C Fanelli¹⁷, S Fegan¹², A M Foda⁷, J Foote¹⁸, J Frye¹⁸, S Furletov⁵, L Gan⁹, A Gasparian¹⁹, V Gauzshtein^{20

21}, N Gevorgyan²², C Gleason¹⁸, K Goetzen¹, A Goncalves⁶, V S Goryachev¹⁶, L Guo¹⁰, H Hakobyan¹³, A Hamdi¹, S Han²³, J Hardin¹⁷, G M Huber⁷, A Hurley²⁴, D G Ireland²⁵, M M Ito⁵, N S Jarvis⁴, R T Jones²⁶, V Kakoyan²², G Kalicy¹¹, M Kamel¹⁰, C Kourkoumelis³, S Kuleshov¹³, I Kuznetsov^{20

21}, I Larin²⁷, D Lawrence⁵, D I Lersch⁶, H Li⁴, W Li²⁴, B Liu¹⁴, K Livingston²⁵, G J Lolos⁷, V Lyubovitskij^{20

21}, D Mack⁵, H Marukyan²², V Matveev¹⁶, M McCaughan⁵, M McCracken⁴, W McGinley⁴, J McIntyre²⁶, C A Meyer⁴, R Miskimen²⁷, R E Mitchell¹⁸, F Mokaya²⁶, F Nerling¹, L Ng⁶, A I Ostrovidov⁶, Z Papandreou⁷, M Patsyuk¹⁷, P Pauli²⁵, R Pedroni¹⁹, L Pentchev⁵, K J Peters¹, W Phelps¹², E Pooser⁵, N Qin²⁸, J Reinhold¹⁰, B G Ritchie¹⁵, L Robison²⁸, D Romanov⁸, C Romero¹³, C Salgado²⁹, A M Schertz²⁴, R A Schumacher⁴, J Schwiening¹, K K Seth²⁸, X Shen¹⁴, M R Shepherd¹⁸, E S Smith⁵, D I Sober¹¹, A Somov⁵, S Somov⁸, O Soto¹³, J R Stevens²⁴, I I Strakovsky¹², K Suresh⁷, V Tarasov¹⁶, S Taylor⁵, A Teymurazyan⁷, A Thiel²⁵, G Vasileiadis³, D Werthmüller²⁵, T Whitlatch⁵, N Wickramaarachchi², M Williams¹⁷, T Xiao²⁸, Y Yang¹⁷, J Zarling¹⁸, Z Zhang²³, G Zhao¹⁴, Q Zhou¹⁴, X Zhou²³, B Zihlmann⁵; GlueX Collaboration

Affiliations

¹ GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany.
² Old Dominion University, Norfolk, Virginia 23529, USA.
³ National and Kapodistrian University of Athens, 15771 Athens, Greece.
⁴ Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
⁵ Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
⁶ Florida State University, Tallahassee, Florida 32306, USA.
⁷ University of Regina, Regina, Saskatchewan, Canada S4S 0A2.
⁸ National Research Nuclear University Moscow Engineering Physics Institute, Moscow 115409, Russia.
⁹ University of North Carolina at Wilmington, Wilmington, North Carolina 28403, USA.
¹⁰ Florida International University, Miami, Florida 33199, USA.
¹¹ The Catholic University of America, Washington, D.C. 20064, USA.
¹² The George Washington University, Washington, D.C. 20052, USA.
¹³ Universidad Técnica Federico Santa María, Casilla 110-V Valparaíso, Chile.
¹⁴ Institute of High Energy Physics, Beijing 100049, People's Republic of China.
¹⁵ Arizona State University, Tempe, Arizona 85287, USA.
¹⁶ National Research Centre Kurchatov Institute, Institute for Theoretical and Experimental Physics, Moscow 117259, Russia.
¹⁷ Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
¹⁸ Indiana University, Bloomington, Indiana 47405, USA.
¹⁹ North Carolina A&T State University, Greensboro, North Carolina 27411, USA.
²⁰ Tomsk State University, 634050 Tomsk, Russia.
²¹ Tomsk Polytechnic University, 634050 Tomsk, Russia.
²² A.I. Alikhanian National Science Laboratory (Yerevan Physics Institute), 0036 Yerevan, Armenia.
²³ Wuhan University, Wuhan, Hubei 430072, People's Republic of China.
²⁴ College of William and Mary, Williamsburg, Virginia 23185, USA.
²⁵ University of Glasgow, Glasgow G12 8QQ, United Kingdom.
²⁶ University of Connecticut, Storrs, Connecticut 06269, USA.
²⁷ University of Massachusetts, Amherst, Massachusetts 01003, USA.
²⁸ Northwestern University, Evanston, Illinois 60208, USA.
²⁹ Norfolk State University, Norfolk, Virginia 23504, USA.

PMID: 31491124
DOI: 10.1103/PhysRevLett.123.072001

Abstract

We report on the measurement of the γp→J/ψp cross section from E_{γ}=11.8 GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment. We find that the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section dσ/dt has an exponential slope of 1.67±0.39 GeV^{-2} at 10.7 GeV average energy. The LHCb pentaquark candidates P_{c}^{+} can be produced in the s channel of this reaction. We see no evidence for them and set model-dependent upper limits on their branching fractions B(P_{c}^{+}→J/ψp) and cross sections σ(γp→P_{c}^{+})×B(P_{c}^{+}→J/ψp).