1. Coherent diffractive photoproduction of $ρ^{0}$ mesons on gold nuclei at RHIC
- Author
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Collaboration, STAR, Adamczyk, L, Adkins, JK, Agakishiev, G, Aggarwal, MM, Ahammed, Z, Ajitanand, NN, Alekseev, I, Anderson, DM, Aoyama, R, Aparin, A, Arkhipkin, D, Aschenauer, EC, Ashraf, MU, Attri, A, Averichev, GS, Bai, X, Bairathi, V, Behera, A, Bellwied, R, Bhasin, A, Bhati, AK, Bhattarai, P, Bielcik, J, Bielcikova, J, Bland, LC, Bordyuzhin, IG, Bouchet, J, Brandenburg, JD, Brandin, AV, Brown, D, Bunzarov, I, Butterworth, J, Caines, H, Sánchez, MCDLB, Campbell, JM, Cebra, D, Chakaberia, I, Chaloupka, P, Chang, Z, Chankova-Bunzarova, N, Chatterjee, A, Chattopadhyay, S, Chen, X, Chen, JH, Cheng, J, Cherney, M, Christie, W, Contin, G, Crawford, HJ, Das, S, Silva, LCD, Debbe, RR, Dedovich, TG, Deng, J, Derevschikov, AA, Didenko, L, Dilks, C, Dong, X, Drachenberg, JL, Draper, JE, Dunkelberger, LE, Dunlop, JC, Efimov, LG, Elsey, N, Engelage, J, Eppley, G, Esha, R, Esumi, S, Evdokimov, O, Ewigleben, J, Eyser, O, Fatemi, R, Fazio, S, Federic, P, Federicova, P, Fedorisin, J, Feng, Z, Filip, P, Finch, E, Fisyak, Y, Flores, CE, Fujita, J, Fulek, L, Gagliardi, CA, Garand, D, Geurts, F, Gibson, A, Girard, M, Grosnick, D, Gunarathne, DS, Guo, Y, Gupta, A, Gupta, S, Guryn, W, Hamad, AI, Hamed, A, Harlenderova, A, Harris, JW, He, L, Heppelmann, S, Hirsch, A, Hoffmann, GW, Horvat, S, Huang, B, Huang, T, Huang, HZ, Huang, X, Humanic, TJ, Huo, P, Igo, G, Jacobs, WW, Jentsch, A, Jia, J, Jiang, K, Jowzaee, S, Judd, EG, Kabana, S, Kalinkin, D, Kang, K, Kauder, K, Ke, HW, Keane, D, Kechechyan, A, Khan, Z, Kikoła, DP, Kisel, I, Kisiel, A, Klein, SR, Kochenda, L, Kocmanek, M, Kollegger, T, Kosarzewski, LK, Kraishan, AF, Kravtsov, P, Krueger, K, Kulathunga, N, Kumar, L, Kvapil, J, Kwasizur, JH, Lacey, R, Landgraf, JM, Landry, KD, Lauret, J, Lebedev, A, Lednicky, R, Lee, JH, Li, W, Li, X, Li, C, Li, Y, Lidrych, J, Lin, T, Lisa, MA, Liu, Y, Liu, F, Liu, H, Liu, P, Ljubicic, T, Llope, WJ, Lomnitz, M, Longacre, RS, Luo, S, Luo, X, Ma, GL, Ma, YG, Ma, L, Ma, R, Magdy, N, Majka, R, Mallick, D, Margetis, S, Markert, C, Matis, HS, Meehan, K, Mei, JC, Miller, ZW, Minaev, NG, Mioduszewski, S, Mishra, D, Mizuno, S, Mohanty, B, Mondal, MM, Morozov, DA, Mustafa, MK, Nasim, M, Nayak, TK, Nelson, JM, Nie, M, Nigmatkulov, G, Niida, T, Nogach, LV, Nonaka, T, Nurushev, SB, Odyniec, G, Ogawa, A, Oh, K, Okorokov, VA, Jr, DO, Page, BS, Pak, R, Pandit, Y, Panebratsev, Y, Pawlik, B, Pei, H, Perkins, C, Pile, P, Pluta, J, Poniatowska, K, Porter, J, Posik, M, Poskanzer, AM, Pruthi, NK, Przybycien, M, Putschke, J, Qiu, H, Quintero, A, Ramachandran, S, Ray, RL, Reed, R, Rehbein, MJ, Ritter, HG, Roberts, JB, Rogachevskiy, OV, Romero, JL, Roth, JD, Ruan, L, Rusnak, J, Rusnakova, O, Sahoo, NR, Sahu, PK, Salur, S, Sandweiss, J, Saur, M, Schambach, J, Schmah, AM, Schmidke, WB, Schmitz, N, Schweid, BR, Seger, J, Sergeeva, M, Seyboth, P, Shah, N, Shahaliev, E, Shanmuganathan, PV, Shao, M, Sharma, A, Sharma, MK, Shen, WQ, Shi, Z, Shi, SS, Shou, QY, Sichtermann, EP, Sikora, R, Simko, M, Singha, S, Skoby, MJ, Smirnov, N, Smirnov, D, Solyst, W, Song, L, Sorensen, P, Spinka, HM, Srivastava, B, Stanislaus, TDS, Strikhanov, M, Stringfellow, B, Sugiura, T, Sumbera, M, Summa, B, Sun, Y, Sun, XM, Sun, X, Surrow, B, Svirida, DN, Tang, AH, Tang, Z, Taranenko, A, Tarnowsky, T, Tawfik, A, Thäder, J, Thomas, JH, Timmins, AR, Tlusty, D, Todoroki, T, Tokarev, M, Trentalange, S, Tribble, RE, Tribedy, P, Tripathy, SK, Trzeciak, BA, Tsai, OD, Ullrich, T, Underwood, DG, Upsal, I, Buren, GV, Nieuwenhuizen, GV, Vasiliev, AN, Videbæk, F, Vokal, S, Voloshin, SA, Vossen, A, Wang, G, Wang, Y, Wang, F, Webb, JC, Webb, G, Wen, L, Westfall, GD, Wieman, H, Wissink, SW, Witt, R, Wu, Y, Xiao, ZG, Xie, W, Xie, G, Xu, J, Xu, N, Xu, QH, Xu, YF, Xu, Z, Yang, Y, Yang, Q, Yang, C, Yang, S, Ye, Z, Yi, L, Yip, K, Yoo, I-K, Yu, N, Zbroszczyk, H, Zha, W, Zhang, Z, Zhang, XP, Zhang, JB, Zhang, S, Zhang, J, Zhang, Y, Zhao, J, Zhong, C, Zhou, L, Zhou, C, Zhu, X, Zhu, Z, and Zyzak, M
- Subjects
hep-ex ,Nuclear Experiment ,nucl-ex - Abstract
The STAR Collaboration reports on the photoproduction of $\pi^+\pi^-$ pairs in gold-gold collisions at a center-of-mass energy of 200 GeV/nucleon-pair. These pion pairs are produced when a nearly-real photon emitted by one ion scatters from the other ion. We fit the $\pi^+\pi^-$ invariant mass spectrum with a combination of $\rho$ and $\omega$ resonances and a direct $\pi^+\pi^-$ continuum. This is the first observation of the $\omega$ in ultra-peripheral collisions, and the first measurement of $\rho-\omega$ interference at energies where photoproduction is dominated by Pomeron exchange. The $\omega$ amplitude is consistent with the measured $\gamma p\rightarrow \omega p$ cross section, a classical Glauber calculation and the $\omega\rightarrow\pi^+\pi^-$ branching ratio. The $\omega$ phase angle is similar to that observed at much lower energies, showing that the $\rho-\omega$ phase difference does not depend significantly on photon energy. The $\rho^0$ differential cross section $d\sigma/dt$ exhibits a clear diffraction pattern, compatible with scattering from a gold nucleus, with 2 minima visible. The positions of the diffractive minima agree better with the predictions of a quantum Glauber calculation that does not include nuclear shadowing than with a calculation that does include shadowing.
- Published
- 2018