Abstract
We report on the first measurements of J/ψ production at very low transverse momentum (p_{T}<0.2 GeV/c) in hadronic Au+Au collisions at sqrt[s_{NN}]=200 GeV and U+U collisions at sqrt[s_{NN}]=193 GeV. Remarkably, the inferred nuclear modification factor of J/ψ at midrapidity in Au+Au (U+U) collisions reaches about 24 (52) for p_{T}<0.05 GeV/c in the 60%-80% collision centrality class. This noteworthy enhancement cannot be explained by hadronic production accompanied by cold and hot medium effects. In addition, the dN/dt distribution of J/ψ for the very low p_{T} range is presented for the first time. The distribution is consistent with that expected from the Au nucleus and shows a hint of interference. Comparison of the measurements to theoretical calculations of coherent production shows that the excess yield can be described reasonably well and reveals a partial disruption of coherent production in semicentral collisions, perhaps due to the violent hadronic interactions. Incorporating theoretical calculations, the results strongly suggest that the dramatic enhancement of J/ψ yield observed at extremely low p_{T} originates from coherent photon-nucleus interactions. In particular, coherently produced J/ψ's in violent hadronic collisions may provide a novel probe of the quark-gluon plasma.
Highlights
Comparison of the measurements to theoretical calculations of coherent production shows that the excess yield can be described reasonably well and reveals a partial disruption of coherent production in semicentral collisions, perhaps due to the violent hadronic interactions
Incorporating theoretical calculations, the results strongly suggest that the dramatic enhancement of J=ψ yield observed at extremely low pT originates from coherent photon-nucleus interactions
J=ψ suppression in heavy-ion collisions has been proposed as a “smoking gun” of quark-gluon plasma (QGP) formation [2] owing to the color screening effect in the deconfined medium
Summary
J. Adam,12 L. Adamczyk,2 J. R. Adams,35 J. K. Adkins,26 G. Agakishiev,24 M. M. Aggarwal,37 Z. Ahammed,57 I. Alekseev,3,31 D. M. Anderson,51 R. Aoyama,54 A. Aparin,24 D. Arkhipkin,5 E. C. Aschenauer,5 M. U. Ashraf,53 F. Atetalla,25 A. Attri,37 G. S. Averichev,24 V. Bairathi,32 K. Barish,9 A. J. Bassill,9 A. Behera,49 R. Bellwied,19 A. Bhasin,23 A. K. Bhati,37 J. Bielcik,13 J. Bielcikova,34 L. C. Bland,5 I. G. Bordyuzhin,3 J. D. Brandenburg,5 A. V. Brandin,31 J. Bryslawskyj,9 I. Bunzarov,24 J. Butterworth,42 H. Caines,60 M. Calderón de la Barca Sánchez,7 D. Cebra,7 I. Chakaberia,25,46 P. Chaloupka,13 B. K. Chan,8 F-H. Chang,33 Z. Chang,5 N. Chankova-Bunzarova,24 A. Chatterjee,57 S. Chattopadhyay,57 J. H. Chen,47 X. Chen,45 J. Cheng,53 M. Cherney,12 W. Christie,5 H. J. Crawford,6 M. Csanad,15 S. Das,10 T. G. Dedovich,24 I. M. Deppner,18 A. A. Derevschikov,39 L. Didenko,5 C. Dilks,38 X. Dong,27 J. L. Drachenberg,1 J. C. Dunlop,5 T. Edmonds,40 N. Elsey,59 J. Engelage,6 G. Eppley,42 R. Esha,8 S. Esumi,54 O. Evdokimov,11 J. Ewigleben,28 O. Eyser,5 R. Fatemi,26 S. Fazio,5 P. Federic,34 J. Fedorisin,24 Y. Feng,40 P. Filip,24 E. Finch,48 Y. Fisyak,5 L. Fulek,2 C. A. Gagliardi,51 T. Galatyuk,14 F. Geurts,42 A. Gibson,56 D. Grosnick,56 A. Gupta,23 W. Guryn,5 A. I. Hamad,25 A. Hamed,51 J. W. Harris,60 L. He,40 S. Heppelmann,7 S. Heppelmann,38 N. Herrmann,18 L. Holub,13 Y. Hong,27 S. Horvat,60 B. Huang,11 H. Z. Huang,8 S. L. Huang,49 T. Huang,33 X. Huang,53 T. J. Humanic,35 P. Huo,49 G. Igo,8 W. W. Jacobs,21 A. Jentsch,52 J. Jia,5,49 K. Jiang,45 S. Jowzaee,59 X. Ju,45 E. G. Judd,6 S. Kabana,25 S. Kagamaster,28 D. Kalinkin,21 K. Kang,53 D. Kapukchyan,9 K. Kauder,5 H. W. Ke,5 D. Keane,25 A. Kechechyan,24 M. Kelsey,27 D. P. Kikoła,58 C. Kim,9 T. A. Kinghorn,7 I. Kisel,16 A. Kisiel,58 M. Kocan,13 L. Kochenda,31 L. K. Kosarzewski,13 L. Kramarik,13 P. Kravtsov,31 K. Krueger,4 N. Kulathunga Mudiyanselage,19 L. Kumar,37 R. Kunnawalkam Elayavalli,59 J. H. Kwasizur,21 R. Lacey,49 J. M. Landgraf,5 J. Lauret,5 A. Lebedev,5 R. Lednicky,24 J. H. Lee,5 C. Li,45 W. Li,42 W. Li,47 X. Li,45 Y. Li,53 Y. Liang,25 R. Licenik,13 T. Lin,51 A. Lipiec,58 M. A. Lisa,35 F. Liu,10 H. Liu,21 P. Liu,49 P. Liu,47 X. Liu,35 Y. Liu,51 Z. Liu,45 T. Ljubicic,5 W. J. Llope,59 M. Lomnitz,27 R. S. Longacre,5 S. Luo,11 X. Luo,10 G. L. Ma,47 L. Ma,17 R. Ma,5 Y. G. Ma,47 N. Magdy,11 R. Majka,60 D. Mallick,32 S. Margetis,25 C. Markert,52 H. S. Matis,27 O. Matonoha,13 J. A. Mazer,43 K. Meehan,7 J. C. Mei,46 N. G. Minaev,39 S. Mioduszewski,51 D. Mishra,32 B. Mohanty,32 M. M. Mondal,22 I. Mooney,59 Z. Moravcova,13 D. A. Morozov,39 Md. Nasim,8 K. Nayak,10 J. M. Nelson,6 D. B. Nemes,60 M. Nie,46 G. Nigmatkulov,31 T. Niida,59 L. V. Nogach,39 T. Nonaka,10 G. Odyniec,27 A. Ogawa,5 K. Oh,41 S. Oh,60 V. A. Okorokov,31 B. S. Page,5 R. Pak,5 Y. Panebratsev,24 B. Pawlik,36 H. Pei,10 C. Perkins,6 R. L. Pinter,15 J. Pluta,58 J. Porter,27 M. Posik,50 N. K. Pruthi,37 M. Przybycien,2 J. Putschke,59 A. Quintero,50 S. K. Radhakrishnan,27 S. Ramachandran,26 R. L. Ray,52 R. Reed,28 H. G. Ritter,27 J. B. Roberts,42 O. V. Rogachevskiy,24 J. L. Romero,7 L. Ruan,5 J. Rusnak,34 O. Rusnakova,13 N. R. Sahoo,51 P. K. Sahu,22 S. Salur,43 J. Sandweiss,60 J. Schambach,52 W. B. Schmidke,5 N. Schmitz,29 B. R. Schweid,49 F. Seck,14 J. Seger,12 M. Sergeeva,8 R. Seto,9 P. Seyboth,29 N. Shah,47 E. Shahaliev,24 P. V. Shanmuganathan,28 M. Shao,45 F. Shen,46 W. Q. Shen,47 S. S. Shi,10 Q. Y. Shou,47 E. P. Sichtermann,27 S. Siejka,58 R. Sikora,2 M. Simko,34 JSingh,37 S. Singha,25 D. Smirnov,5 N. Smirnov,60 W. Solyst,21 P. Sorensen,5 H. M. Spinka,4 B. Srivastava,40 T. D. S. Stanislaus,56 D. J. Stewart,60 M. Strikhanov,31 B. Stringfellow,40 A. A. P. Suaide,44 T. Sugiura,54 M. Sumbera,34 B. Summa,38 X. M. Sun,10 Y. Sun,45 Y. Sun,20 B. Surrow,50 D. N. Svirida,3 P. Szymanski,58 A. H. Tang,5 Z. Tang,45 A. Taranenko,31 T. Tarnowsky,30 J. H. Thomas,27 A. R. Timmins,19 T. Todoroki,5 M. Tokarev,24 C. A. Tomkiel,28 S. Trentalange,8 R. E. Tribble,51 P. Tribedy,5 S. K. Tripathy,22 O. D. Tsai,8 B. Tu,10 T. Ullrich,5 D. G. Underwood,4 I. Upsal,46,5 G. Van Buren,5 J. Vanek,34 A. N. Vasiliev,39 I. Vassiliev,16 F. Videbæk,5 S. Vokal,24 S. A. Voloshin,59 F. Wang,40 G. Wang,8 P. Wang,45 Y. Wang,10 Y. Wang,53 J. C. Webb,5 L. Wen,8 G. D. Westfall,30 H. Wieman,27 S. W. Wissink,21 R. Witt,55 Y. Wu,25 Z. G. Xiao,53 G. Xie,11 W. Xie,40 H. Xu,20 N. Xu,27 Q. H. Xu,46 Y. F. Xu,47 Z. Xu,5 C. Yang,46 Q. Yang,46 S. Yang,5 Y. Yang,33 Z. Ye,42 Z. Ye,11 L. Yi,46 K. Yip,5 I.-K. Yoo,41 H. Zbroszczyk,58 W. Zha ,45 D. Zhang,10 L. Zhang,10 S. Zhang,45 S. Zhang,47 X. P. Zhang,53 Y. Zhang,45 Z. Zhang,47 J. Zhao,40 C. Zhong,47 C. Zhou,47 X. Zhu,53 Z. Zhu,46 M. K. Zurek,27 and M. Zyzak16
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