• Improved measurement of the longitudinal spin transfer to Λ and Λ¯ hyperons in polarized proton-proton collisions at s=200  GeV

      Adam, J; Adamczyk, L; Adams, JR; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Alekseev, I; Anderson, DM; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, EC; Ashraf, MU; Atetalla, F; Attri, A; Averichev, GS; Bai, X; Bairathi, V; Barish, K; Bassill, AJ; Behera, A; Bellwied, R; Bhasin, A; Bhati, AK; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Brandenburg, JD; Brandin, AV; Brown, D; Bryslawskyj, J; Bunzarov, I; Butterworth, J; Caines, H; Calderón De La Barca Sánchez, M; Cebra, D; Cendejas, R; Chakaberia, I; Chaloupka, P; Chan, BK; Chang, F-H; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, JH; Chen, X; Chen, X; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Csanad, M; Das, S; Dedovich, TG; Deng, J; Deppner, IM; Derevschikov, AA; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; 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; Filip, P; Finch, E; Fisyak, Y; Flores, CE; Fulek, L; Gagliardi, CA; Galatyuk, T; Geurts, F; Gibson, A; Grosnick, D; Gunarathne, DS; Guo, Y; Gupta, A; Guryn, W; Hamad, AI; Hamed, A; Harlenderova, A; Harris, JW; He, L; Heppelmann, S; Heppelmann, S; Herrmann, N; Hirsch, A; Holub, L; Hong, Y; Horvat, S; Huang, B; Huang, HZ; Huang, SL; Huang, T; Huang, X; Humanic, TJ; Huo, P; Igo, G; Jacobs, WW; Jentsch, A; Jia, J; Jiang, K; Jowzaee, S; Ju, X; Judd, EG; Kabana, S; Kagamaster, S; Kalinkin, D; Kang, K; Kapukchyan, D; Kauder, K; Ke, HW; Keane, D; Kechechyan, A; Kikoła, DP; Kim, C; Kinghorn, TA; Kisel, I; Kisiel, A; Kochenda, L; Kosarzewski, LK; Kraishan, AF; Kramarik, L; Krauth, L; Kravtsov, P; Krueger, K; Kulathunga, N; Kumar, L; Kunnawalkam Elayavalli, R; Kvapil, J; Kwasizur, JH; Lacey, R; Landgraf, JM; Lauret, J; Lebedev, A; Lednicky, R; Lee, JH; Li, C; Li, W; Li, X; Li, Y; Liang, Y; Lidrych, J; Lin, T; Lipiec, A; Lisa, MA; Liu, F; Liu, H; Liu, P; Liu, P; Liu, Y; Liu, Z; Ljubicic, T; Llope, WJ; Lomnitz, M; Longacre, RS; Luo, S; Luo, X; Ma, GL; Ma, L; Ma, R; Ma, YG; Magdy, N; Majka, R; Mallick, D; Margetis, S; Markert, C; Matis, HS; Matonoha, O; Mazer, JA; Meehan, K; Mei, JC; Minaev, NG; Mioduszewski, S; Mishra, D; Mohanty, B; Mondal, MM; Mooney, I; Morozov, DA; Nasim, Md; Negrete, JD; Nelson, JM; Nemes, DB; Nie, M; Nigmatkulov, G; Niida, T; Nogach, LV; Nonaka, T; Odyniec, G; Ogawa, A; Oh, K; Oh, S; Okorokov, VA; Olvitt, D; Page, BS; Pak, R; Panebratsev, Y; Pawlik, B; Pei, H; Perkins, C; Pinter, RL; Pluta, J; Porter, J; Posik, M; Pruthi, NK; Przybycien, M; Putschke, J; Quintero, A; Radhakrishnan, SK; Ramachandran, S; Ray, RL; Reed, R; Ritter, HG; Roberts, JB; Rogachevskiy, OV; Romero, JL; Ruan, L; Rusnak, J; Rusnakova, O; Sahoo, NR; Sahu, PK; Salur, S; Sandweiss, J; Schambach, J; Schmah, AM; Schmidke, WB; Schmitz, N; Schweid, BR; Seck, F; Seger, J; Sergeeva, M; Seto, R; Seyboth, P; Shah, N; Shahaliev, E; Shanmuganathan, PV; Shao, M; Shen, F; Shen, WQ; Shi, SS; Shou, QY; Sichtermann, EP; Siejka, S; Sikora, R; Simko, M; Singh, J; Singha, S; Smirnov, D; Smirnov, N; Solyst, W; Sorensen, P; Spinka, HM; Srivastava, B; Stanislaus, TDS; Stewart, DJ; Strikhanov, M; Stringfellow, B; Suaide, AAP; Sugiura, T; Sumbera, M; Summa, B; Sun, XM; Sun, X; Sun, Y; Surrow, B; Svirida, DN; Szymanski, P; Tang, AH; Tang, Z; Taranenko, A; Tarnowsky, T; Thomas, JH; Timmins, AR; Tlusty, D; Todoroki, T; Tokarev, M; Tomkiel, CA; Trentalange, S; Tribble, RE; Tribedy, P; Tripathy, SK; Tsai, OD; Tu, B; Ullrich, T; Underwood, DG; Upsal, I; Van Buren, G; Vanek, J; Vasiliev, AN; Vassiliev, I; Videbæk, F; Vokal, S; Voloshin, SA; Vossen, A; Wang, F; Wang, G; Wang, P; Wang, Y; Wang, Y; Webb, JC; Wen, L; Westfall, GD; Wieman, H; Wissink, SW; Witt, R; Wu, Y; Xiao, ZG; Xie, G; Xie, W; Xu, J; Xu, N; Xu, QH; Xu, YF; Xu, Z; Yang, C; Yang, Q; Yang, S; Yang, Y; Ye, Z; Ye, Z; Yi, L; Yip, K; Yoo, I-K; Yu, N; Zbroszczyk, H; Zha, W; Zhang, J; Zhang, J; Zhang, L; Zhang, S; Zhang, S; Zhang, XP; Zhang, Y; Zhang, Z; Zhao, J; Zhong, C; Zhou, C; Zhu, X; Zhu, Z; Zyzak, M (2018-12-01)
      The longitudinal spin transfer $D_{LL}$ to $\Lambda$ and $\bar{\Lambda}$ hyperons produced in high-energy polarized proton--proton collisions is expected to be sensitive to the helicity distribution functions of strange quarks and anti-quarks of the proton, and to longitudinally polarized fragmentation functions. We report an improved measurement of $D_{LL}$ from data obtained at a center-of-mass energy of $\sqrt{s}$ = 200 GeV with the STAR detector at RHIC. The data have an approximately twelve times larger figure-of-merit than prior results and cover $|\eta|<$ 1.2 in pseudo-rapidity with transverse momenta $p_T$ up to 6 GeV/c. In the forward scattering hemisphere at largest $p_T$, the longitudinal spin transfer is found to be $D_{LL}$ = -0.036 $\pm$ 0.048 (stat) $\pm$ 0.013(sys) for $\Lambda$ hyperons and $D_{LL}$ = 0.032 $\pm$ 0.043\,(stat) $\pm$ 0.013\,(sys) for $\bar{\Lambda}$ anti-hyperons. The dependences on $\eta$ and $p_T$ are presented and compared with model evaluations.
    • Longitudinal double-spin asymmetries for pi(0)s in the forward direction for 510 GeV polarized pp collisions

      Adam, J; Adamczyk, L; Adams, JR; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Ajitanand, NN; Alekseev, I; Anderson, DM; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, EC; Ashraf, MU; Atetalla, F; Attri, A; Averichev, GS; Bai, X; Bairathi, V; Barish, K; Bassill, AJ; Behera, A; Bellwied, R; Bhasin, A; Bhati, AK; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Brandenburg, JD; Brandin, AV; Brown, D; Bryslawskyj, J; Bunzarov, I; Butterworth, J; Caines, H; Sanchez, M Calderon de la Barca; Campbell, JM; Cebra, D; Chakaberia, I; Chaloupka, P; Chang, F-H; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, JH; Chen, X; Chen, X; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Das, S; Dedovich, TG; Deppner, IM; Derevschikov, AA; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; 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; Filip, P; Finch, E; Fisyak, Y; Flores, CE; Fulek, L; Gagliardi, CA; Galatyuk, T; Geurts, F; Gibson, A; Grosnick, D; Gunarathne, DS; Guo, Y; Gupta, A; Guryn, W; Hamad, AI; Hamed, A; Harlenderova, A; Harris, JW; He, L; Heppelmann, S; Heppelmann, S; Herrmann, N; Hirsch, A; Holub, L; Horvat, S; Huang, X; Huang, B; Huang, SL; Huang, HZ; Huang, T; Humanic, TJ; Huo, P; Igo, G; Jacobs, WW; Jentsch, A; Jia, J; Jiang, K; Jowzaee, S; Judd, EG; Kabana, S; Kalinkin, D; Kang, K; Kapukchyan, D; Kauder, K; Ke, HW; Keane, D; Kechechyan, A; Kikola, DP; Kim, C; Kinghorn, TA; Kisel, I; Kisiel, A; Kochenda, L; Kosarzewski, LK; Kraishan, AF; Kramarik, L; Krauth, L; Kravtsov, P; Krueger, K; Kulathunga, N; Kumar, S; Kumar, L; Kvapil, J; Kwasizur, JH; Lacey, R; Landgraf, JM; Lauret, J; Lebedev, A; Lednicky, R; Lee, JH; Li, X; Li, C; Li, W; Li, Y; Liang, Y; Lidrych, J; Lin, T; Lipiec, A; Lisa, MA; Liu, F; Liu, P; Liu, H; Liu, Y; Ljubicic, T; Llope, WJ; Lomnitz, M; Longacre, RS; Luo, X; Luo, S; Ma, GL; Ma, YG; Ma, L; Ma, R; Magdy, N; Majka, R; Mallick, D; Margetis, S; Markert, C; Matis, HS; Matonoha, O; Mayes, D; Mazer, JA; Meehan, K; Mei, JC; Minaev, NG; Mioduszewski, S; Mishra, D; Mohanty, B; Mondal, MM; Mooney, I; Morozov, DA; Nasim, Md; Negrete, JD; Nelson, JM; Nemes, DB; Nie, M; Nigmatkulov, G; Niida, T; Nogach, LV; Nonaka, T; Nurushev, SB; Odyniec, G; Ogawa, A; Oh, K; Oh, S; Okorokov, VA; Jr, Olvitt D; Page, BS; Pak, R; Panebratsev, Y; Pawlik, B; Pei, H; Perkins, C; Pluta, J; Porter, J; Posik, M; Pruthi, NK; Przybycien, M; Putschke, J; Quintero, A; Radhakrishnan, SK; Ramachandran, S; Ray, RL; Reed, R; Ritter, HG; Roberts, JB; Rogachevskiy, OV; Romero, JL; Ruan, L; Rusnak, J; Rusnakova, O; Sahoo, NR; Sahu, PK; Salur, S; Sandweiss, J; Schambach, J; Schmah, AM; Schmidke, WB; Schmitz, N; Schweid, BR; Seck, F; Seger, J; Sergeeva, M; Seto, R; Seyboth, P; Shah, N; Shahaliev, E; Shanmuganathan, PV; Shao, M; Shen, WQ; Shen, F; Shi, SS; Shou, QY; Sichtermann, EP; Siejka, S; Sikora, R; Simko, M; Singha, S; Smirnov, N; Smirnov, D; Solyst, W; Sorensen, P; Spinka, HM; Srivastava, B; Stanislaus, TDS; Stewart, DJ; Strikhanov, M; Stringfellow, B; Suaide, AAP; Sugiura, T; Sumbera, M; Summa, B; Sun, Y; Sun, X; Sun, XM; Surrow, B; Svirida, DN; Szymanski, P; Tang, Z; Tang, AH; Taranenko, A; Tarnowsky, T; Thomas, JH; Timmins, AR; Tlusty, D; Todoroki, T; Tokarev, M; Tomkiel, CA; Trentalange, S; Tribble, RE; Tribedy, P; Tripathy, SK; Tsai, OD; Tu, B; Ullrich, T; Underwood, DG; Upsal, I; Van Buren, G; Vanek, J; Vasiliev, AN; Vassiliev, I; Videbaek, F; Vokal, S; Voloshin, SA; Vossen, A; Wang, G; Wang, Y; Wang, F; Wang, Y; Webb, JC; Wen, L; Westfall, GD; Wieman, H; Wissink, SW; Witt, R; Wu, Y; Xiao, ZG; Xie, G; Xie, W; Xu, QH; Xu, Z; Xu, J; Xu, YF; Xu, N; Yang, S; Yang, C; Yang, Q; Yang, Y; Ye, Z; Yi, L; Yip, K; Yoo, I-K; Yu, N; Zbroszczyk, H; Zha, W; Zhang, Z; Zhang, L; Zhang, Y; Zhang, XP; Zhang, J; Zhang, S; Zhang, S; Zhang, J; Zhao, J; Zhong, C; Zhou, C; Zhou, L; Zhu, Z; Zhu, X; Zyzak, M; Collaboration, STAR (2018-08-27)
      The STAR Collaboration reports measurements of the longitudinal double-spin asymmetry, $A_{LL}$, for neutral pions produced at forward directions in polarized proton-proton collisions, at a center-of-mass energy of $510$ GeV. Results are given for transverse momenta in the range $2<p_{T}<10$ GeV/$c$ within two regions of pseudorapidity that span $2.65<\eta<3.9$. These results are sensitive to the polarized gluon parton distribution function, $\Delta g(x)$, down to the region of Bjorken $x \sim 10^{-3}$. The asymmetries observed are less than $\pm 5 \cdot 10^{-3}$ in magnitude, and will help constrain the contribution to the spin of the proton from polarized gluons at low $x$, when combined with other measurements as part of a global analysis.