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Title: Global Λ hyperon polarization in nuclear collisions

Abstract

The extreme energy densities generated by ultra-relativistic collisions between heavy atomic nuclei produce a state of matter that behaves surprisingly like a fluid, with exceptionally high temperature and low viscosity. Non-central collisions have angular momenta of the order of 1,000ћ, and the resulting fluid may have a strong vortical structure that must be understood to describe the fluid properly. The vortical structure is also of particular interest because the restoration of fundamental symmetries of quantum chromodynamics is expected to produce novel physical effects in the presence of strong vorticity. But, no experimental indications of fluid vorticity in heavy ion collisions have yet been found. Since vorticity represents a local rotational structure of the fluid, spin–orbit coupling can lead to preferential orientation of particle spins along the direction of rotation. Here we present measurements of an alignment between the global angular momentum of a non-central collision and the spin of emitted particles (in this case the collision occurs between gold nuclei and produces Λ baryons), revealing that the fluid produced in heavy ion collisions is the most vortical system so far observed. (At high energies, this fluid is a quark–gluon plasma.) We find that Λ and hyperons show a positive polarizationmore » of the order of a few per cent, consistent with some hydrodynamic predictions. (A hyperon is a particle composed of three quarks, at least one of which is a strange quark; the remainder are up and down quarks, found in protons and neutrons.) A previous measurement that reported a null result, that is, zero polarization, at higher collision energies is seen to be consistent with the trend of our observations, though with larger statistical uncertainties. Furthermore, these data provide experimental access to the vortical structure of the nearly ideal liquid created in a heavy ion collision and should prove valuable in the development of hydrodynamic models that quantitatively connect observations to the theory of the strong force.« less

Authors:
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Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States). Relativistic Heavy Ion Collider (RHIC)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Org.:
STAR Collaboration
OSTI Identifier:
1392218
Report Number(s):
BNL-114181-2017-JA
Journal ID: ISSN 0028-0836; R&D Project: PO 004; KB0202012
Grant/Contract Number:
SC0012704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Name: Nature (London); Journal Volume: 548; Journal Issue: 7665; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; experimental nuclear physics; fluid dynamics

Citation Formats

Adamczyk, L., Adkins, J. K., Agakishiev, G., Aggarwal, M. M., Ahammed, Z., Ajitanand, N. N., Alekseev, I., Anderson, D. M., Aoyama, R., Aparin, A., Arkhipkin, D., Aschenauer, E. C., Ashraf, M. U., Attri, A., Averichev, G. S., Bai, X., Bairathi, V., Behera, A., Bellwied, R., Bhasin, A., Bhati, A. K., Bhattarai, P., Bielcik, J., Bielcikova, J., Bland, L. C., Bordyuzhin, I. G., Bouchet, J., Brandenburg, J. D., Brandin, A. V., Brown, D., Bunzarov, I., Butterworth, J., Caines, H., de la Barca Sánchez, M. Calderón, Campbell, J. M., Cebra, D., Chakaberia, I., Chaloupka, P., Chang, Z., Chankova-Bunzarova, N., Chatterjee, A., Chattopadhyay, S., Chen, X., Chen, J. H., Chen, X., Cheng, J., Cherney, M., Christie, W., Contin, G., Crawford, H. J., Das, S., De Silva, L. C., Debbe, R. R., Dedovich, T. G., Deng, J., Derevschikov, A. A., Didenko, L., Dilks, C., Dong, X., Drachenberg, J. L., Draper, J. E., Dunkelberger, L. E., Dunlop, J. C., Efimov, L. G., 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, C. E., Fulek, L., Gagliardi, C. A., Garand, D., Geurts, F., Gibson, A., Girard, M., Grosnick, D., Gunarathne, D. S., Guo, Y., Gupta, A., Gupta, S., Guryn, W., Hamad, A. I., Hamed, A., Harlenderova, A., Harris, J. W., He, L., Heppelmann, S., Heppelmann, S., Hirsch, A., Hoffmann, G. W., Horvat, S., Huang, T., Huang, B., Huang, X., Huang, H. Z., Humanic, T. J., Huo, P., Igo, G., Jacobs, W. W., Jentsch, A., Jia, J., Jiang, K., Jowzaee, S., Judd, E. G., Kabana, S., Kalinkin, D., Kang, K., Kauder, K., Ke, H. W., Keane, D., Kechechyan, A., Khan, Z., Kikoła, D. P., Kisel, I., Kisiel, A., Kochenda, L., Kocmanek, M., Kollegger, T., Kosarzewski, L. K., Kraishan, A. F., Kravtsov, P., Krueger, K., Kulathunga, N., Kumar, L., Kvapil, J., Kwasizur, J. H., Lacey, R., Landgraf, J. M., Landry, K. D., Lauret, J., Lebedev, A., Lednicky, R., Lee, J. H., Li, X., Li, C., Li, W., Li, Y., Lidrych, J., Lin, T., Lisa, M. A., Liu, H., Liu, P., Liu, Y., Liu, F., Ljubicic, T., Llope, W. J., Lomnitz, M., Longacre, R. S., Luo, S., Luo, X., Ma, G. L., Ma, L., Ma, Y. G., Ma, R., Magdy, N., Majka, R., Mallick, D., Margetis, S., Markert, C., Matis, H. S., Meehan, K., Mei, J. C., Miller, Z. W., Minaev, N. G., Mioduszewski, S., Mishra, D., Mizuno, S., Mohanty, B., Mondal, M. M., Morozov, D. A., Mustafa, M. K., Nasim, Md., Nayak, T. K., Nelson, J. M., Nie, M., Nigmatkulov, G., Niida, T., Nogach, L. V., Nonaka, T., Nurushev, S. B., Odyniec, G., Ogawa, A., Oh, K., Okorokov, V. A., Olvitt, D., Page, B. S., Pak, R., Pandit, Y., Panebratsev, Y., Pawlik, B., Pei, H., Perkins, C., Pile, P., Pluta, J., Poniatowska, K., Porter, J., Posik, M., Poskanzer, A. M., Pruthi, N. K., Przybycien, M., Putschke, J., Qiu, H., Quintero, A., Ramachandran, S., Ray, R. L., Reed, R., Rehbein, M. J., Ritter, H. G., Roberts, J. B., Rogachevskiy, O. V., Romero, J. L., Roth, J. D., Ruan, L., Rusnak, J., Rusnakova, O., Sahoo, N. R., Sahu, P. K., Salur, S., Sandweiss, J., Saur, M., Schambach, J., Schmah, A. M., Schmidke, W. B., Schmitz, N., Schweid, B. R., Seger, J., Sergeeva, M., Seyboth, P., Shah, N., Shahaliev, E., Shanmuganathan, P. V., Shao, M., Sharma, A., Sharma, M. K., Shen, W. Q., Shi, Z., Shi, S. S., Shou, Q. Y., Sichtermann, E. P., Sikora, R., Simko, M., Singha, S., Skoby, M. J., Smirnov, N., Smirnov, D., Solyst, W., Song, L., Sorensen, P., Spinka, H. M., Srivastava, B., Stanislaus, T. D. S., Strikhanov, M., Stringfellow, B., Sugiura, T., Sumbera, M., Summa, B., Sun, Y., Sun, X. M., Sun, X., Surrow, B., Svirida, D. N., Tang, A. H., Tang, Z., Taranenko, A., Tarnowsky, T., Tawfik, A., Thäder, J., Thomas, J. H., Timmins, A. R., Tlusty, D., Todoroki, T., Tokarev, M., Trentalange, S., Tribble, R. E., Tribedy, P., Tripathy, S. K., Trzeciak, B. A., Tsai, O. D., Ullrich, T., Underwood, D. G., Upsal, I., Van Buren, G., van Nieuwenhuizen, G., Vasiliev, A. N., Videbæk, F., Vokal, S., Voloshin, S. A., Vossen, A., Wang, G., Wang, Y., Wang, F., Wang, Y., Webb, J. C., Webb, G., Wen, L., Westfall, G. D., Wieman, H., Wissink, S. W., Witt, R., Wu, Y., Xiao, Z. G., Xie, W., Xie, G., Xu, J., Xu, N., Xu, Q. H., Xu, Y. F., Xu, Z., Yang, Y., Yang, Q., Yang, C., Yang, S., Ye, Z., Ye, Z., Yi, L., Yip, K., Yoo, I. -K., Yu, N., Zbroszczyk, H., Zha, W., Zhang, Z., Zhang, X. P., Zhang, J. B., Zhang, S., Zhang, J., Zhang, Y., Zhang, J., Zhang, S., Zhao, J., Zhong, C., Zhou, L., Zhou, C., Zhu, X., Zhu, Z., and Zyzak, M.. Global Λ hyperon polarization in nuclear collisions. United States: N. p., 2017. Web. doi:10.1038/nature23004.
Adamczyk, L., Adkins, J. K., Agakishiev, G., Aggarwal, M. M., Ahammed, Z., Ajitanand, N. N., Alekseev, I., Anderson, D. M., Aoyama, R., Aparin, A., Arkhipkin, D., Aschenauer, E. C., Ashraf, M. U., Attri, A., Averichev, G. S., Bai, X., Bairathi, V., Behera, A., Bellwied, R., Bhasin, A., Bhati, A. K., Bhattarai, P., Bielcik, J., Bielcikova, J., Bland, L. C., Bordyuzhin, I. G., Bouchet, J., Brandenburg, J. D., Brandin, A. V., Brown, D., Bunzarov, I., Butterworth, J., Caines, H., de la Barca Sánchez, M. Calderón, Campbell, J. M., Cebra, D., Chakaberia, I., Chaloupka, P., Chang, Z., Chankova-Bunzarova, N., Chatterjee, A., Chattopadhyay, S., Chen, X., Chen, J. H., Chen, X., Cheng, J., Cherney, M., Christie, W., Contin, G., Crawford, H. J., Das, S., De Silva, L. C., Debbe, R. R., Dedovich, T. G., Deng, J., Derevschikov, A. A., Didenko, L., Dilks, C., Dong, X., Drachenberg, J. L., Draper, J. E., Dunkelberger, L. E., Dunlop, J. C., Efimov, L. G., 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, C. E., Fulek, L., Gagliardi, C. A., Garand, D., Geurts, F., Gibson, A., Girard, M., Grosnick, D., Gunarathne, D. S., Guo, Y., Gupta, A., Gupta, S., Guryn, W., Hamad, A. I., Hamed, A., Harlenderova, A., Harris, J. W., He, L., Heppelmann, S., Heppelmann, S., Hirsch, A., Hoffmann, G. W., Horvat, S., Huang, T., Huang, B., Huang, X., Huang, H. Z., Humanic, T. J., Huo, P., Igo, G., Jacobs, W. W., Jentsch, A., Jia, J., Jiang, K., Jowzaee, S., Judd, E. G., Kabana, S., Kalinkin, D., Kang, K., Kauder, K., Ke, H. W., Keane, D., Kechechyan, A., Khan, Z., Kikoła, D. P., Kisel, I., Kisiel, A., Kochenda, L., Kocmanek, M., Kollegger, T., Kosarzewski, L. K., Kraishan, A. F., Kravtsov, P., Krueger, K., Kulathunga, N., Kumar, L., Kvapil, J., Kwasizur, J. H., Lacey, R., Landgraf, J. M., Landry, K. D., Lauret, J., Lebedev, A., Lednicky, R., Lee, J. H., Li, X., Li, C., Li, W., Li, Y., Lidrych, J., Lin, T., Lisa, M. A., Liu, H., Liu, P., Liu, Y., Liu, F., Ljubicic, T., Llope, W. J., Lomnitz, M., Longacre, R. S., Luo, S., Luo, X., Ma, G. L., Ma, L., Ma, Y. G., Ma, R., Magdy, N., Majka, R., Mallick, D., Margetis, S., Markert, C., Matis, H. S., Meehan, K., Mei, J. C., Miller, Z. W., Minaev, N. G., Mioduszewski, S., Mishra, D., Mizuno, S., Mohanty, B., Mondal, M. M., Morozov, D. A., Mustafa, M. K., Nasim, Md., Nayak, T. K., Nelson, J. M., Nie, M., Nigmatkulov, G., Niida, T., Nogach, L. V., Nonaka, T., Nurushev, S. B., Odyniec, G., Ogawa, A., Oh, K., Okorokov, V. A., Olvitt, D., Page, B. S., Pak, R., Pandit, Y., Panebratsev, Y., Pawlik, B., Pei, H., Perkins, C., Pile, P., Pluta, J., Poniatowska, K., Porter, J., Posik, M., Poskanzer, A. M., Pruthi, N. K., Przybycien, M., Putschke, J., Qiu, H., Quintero, A., Ramachandran, S., Ray, R. L., Reed, R., Rehbein, M. J., Ritter, H. G., Roberts, J. B., Rogachevskiy, O. V., Romero, J. L., Roth, J. D., Ruan, L., Rusnak, J., Rusnakova, O., Sahoo, N. R., Sahu, P. K., Salur, S., Sandweiss, J., Saur, M., Schambach, J., Schmah, A. M., Schmidke, W. B., Schmitz, N., Schweid, B. R., Seger, J., Sergeeva, M., Seyboth, P., Shah, N., Shahaliev, E., Shanmuganathan, P. V., Shao, M., Sharma, A., Sharma, M. K., Shen, W. Q., Shi, Z., Shi, S. S., Shou, Q. Y., Sichtermann, E. P., Sikora, R., Simko, M., Singha, S., Skoby, M. J., Smirnov, N., Smirnov, D., Solyst, W., Song, L., Sorensen, P., Spinka, H. M., Srivastava, B., Stanislaus, T. D. S., Strikhanov, M., Stringfellow, B., Sugiura, T., Sumbera, M., Summa, B., Sun, Y., Sun, X. M., Sun, X., Surrow, B., Svirida, D. N., Tang, A. H., Tang, Z., Taranenko, A., Tarnowsky, T., Tawfik, A., Thäder, J., Thomas, J. H., Timmins, A. R., Tlusty, D., Todoroki, T., Tokarev, M., Trentalange, S., Tribble, R. E., Tribedy, P., Tripathy, S. K., Trzeciak, B. A., Tsai, O. D., Ullrich, T., Underwood, D. G., Upsal, I., Van Buren, G., van Nieuwenhuizen, G., Vasiliev, A. N., Videbæk, F., Vokal, S., Voloshin, S. A., Vossen, A., Wang, G., Wang, Y., Wang, F., Wang, Y., Webb, J. C., Webb, G., Wen, L., Westfall, G. D., Wieman, H., Wissink, S. W., Witt, R., Wu, Y., Xiao, Z. G., Xie, W., Xie, G., Xu, J., Xu, N., Xu, Q. H., Xu, Y. F., Xu, Z., Yang, Y., Yang, Q., Yang, C., Yang, S., Ye, Z., Ye, Z., Yi, L., Yip, K., Yoo, I. -K., Yu, N., Zbroszczyk, H., Zha, W., Zhang, Z., Zhang, X. P., Zhang, J. B., Zhang, S., Zhang, J., Zhang, Y., Zhang, J., Zhang, S., Zhao, J., Zhong, C., Zhou, L., Zhou, C., Zhu, X., Zhu, Z., & Zyzak, M.. Global Λ hyperon polarization in nuclear collisions. United States. doi:10.1038/nature23004.
Adamczyk, L., Adkins, J. K., Agakishiev, G., Aggarwal, M. M., Ahammed, Z., Ajitanand, N. N., Alekseev, I., Anderson, D. M., Aoyama, R., Aparin, A., Arkhipkin, D., Aschenauer, E. C., Ashraf, M. U., Attri, A., Averichev, G. S., Bai, X., Bairathi, V., Behera, A., Bellwied, R., Bhasin, A., Bhati, A. K., Bhattarai, P., Bielcik, J., Bielcikova, J., Bland, L. C., Bordyuzhin, I. G., Bouchet, J., Brandenburg, J. D., Brandin, A. V., Brown, D., Bunzarov, I., Butterworth, J., Caines, H., de la Barca Sánchez, M. Calderón, Campbell, J. M., Cebra, D., Chakaberia, I., Chaloupka, P., Chang, Z., Chankova-Bunzarova, N., Chatterjee, A., Chattopadhyay, S., Chen, X., Chen, J. H., Chen, X., Cheng, J., Cherney, M., Christie, W., Contin, G., Crawford, H. J., Das, S., De Silva, L. C., Debbe, R. R., Dedovich, T. G., Deng, J., Derevschikov, A. A., Didenko, L., Dilks, C., Dong, X., Drachenberg, J. L., Draper, J. E., Dunkelberger, L. E., Dunlop, J. C., Efimov, L. G., 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, C. E., Fulek, L., Gagliardi, C. A., Garand, D., Geurts, F., Gibson, A., Girard, M., Grosnick, D., Gunarathne, D. S., Guo, Y., Gupta, A., Gupta, S., Guryn, W., Hamad, A. I., Hamed, A., Harlenderova, A., Harris, J. W., He, L., Heppelmann, S., Heppelmann, S., Hirsch, A., Hoffmann, G. W., Horvat, S., Huang, T., Huang, B., Huang, X., Huang, H. Z., Humanic, T. J., Huo, P., Igo, G., Jacobs, W. W., Jentsch, A., Jia, J., Jiang, K., Jowzaee, S., Judd, E. G., Kabana, S., Kalinkin, D., Kang, K., Kauder, K., Ke, H. W., Keane, D., Kechechyan, A., Khan, Z., Kikoła, D. P., Kisel, I., Kisiel, A., Kochenda, L., Kocmanek, M., Kollegger, T., Kosarzewski, L. K., Kraishan, A. F., Kravtsov, P., Krueger, K., Kulathunga, N., Kumar, L., Kvapil, J., Kwasizur, J. H., Lacey, R., Landgraf, J. M., Landry, K. D., Lauret, J., Lebedev, A., Lednicky, R., Lee, J. H., Li, X., Li, C., Li, W., Li, Y., Lidrych, J., Lin, T., Lisa, M. A., Liu, H., Liu, P., Liu, Y., Liu, F., Ljubicic, T., Llope, W. J., Lomnitz, M., Longacre, R. S., Luo, S., Luo, X., Ma, G. L., Ma, L., Ma, Y. G., Ma, R., Magdy, N., Majka, R., Mallick, D., Margetis, S., Markert, C., Matis, H. S., Meehan, K., Mei, J. C., Miller, Z. W., Minaev, N. G., Mioduszewski, S., Mishra, D., Mizuno, S., Mohanty, B., Mondal, M. M., Morozov, D. A., Mustafa, M. K., Nasim, Md., Nayak, T. K., Nelson, J. M., Nie, M., Nigmatkulov, G., Niida, T., Nogach, L. V., Nonaka, T., Nurushev, S. B., Odyniec, G., Ogawa, A., Oh, K., Okorokov, V. A., Olvitt, D., Page, B. S., Pak, R., Pandit, Y., Panebratsev, Y., Pawlik, B., Pei, H., Perkins, C., Pile, P., Pluta, J., Poniatowska, K., Porter, J., Posik, M., Poskanzer, A. M., Pruthi, N. K., Przybycien, M., Putschke, J., Qiu, H., Quintero, A., Ramachandran, S., Ray, R. L., Reed, R., Rehbein, M. J., Ritter, H. G., Roberts, J. B., Rogachevskiy, O. V., Romero, J. L., Roth, J. D., Ruan, L., Rusnak, J., Rusnakova, O., Sahoo, N. R., Sahu, P. K., Salur, S., Sandweiss, J., Saur, M., Schambach, J., Schmah, A. M., Schmidke, W. B., Schmitz, N., Schweid, B. R., Seger, J., Sergeeva, M., Seyboth, P., Shah, N., Shahaliev, E., Shanmuganathan, P. V., Shao, M., Sharma, A., Sharma, M. K., Shen, W. Q., Shi, Z., Shi, S. S., Shou, Q. Y., Sichtermann, E. P., Sikora, R., Simko, M., Singha, S., Skoby, M. J., Smirnov, N., Smirnov, D., Solyst, W., Song, L., Sorensen, P., Spinka, H. M., Srivastava, B., Stanislaus, T. D. S., Strikhanov, M., Stringfellow, B., Sugiura, T., Sumbera, M., Summa, B., Sun, Y., Sun, X. M., Sun, X., Surrow, B., Svirida, D. N., Tang, A. H., Tang, Z., Taranenko, A., Tarnowsky, T., Tawfik, A., Thäder, J., Thomas, J. H., Timmins, A. R., Tlusty, D., Todoroki, T., Tokarev, M., Trentalange, S., Tribble, R. E., Tribedy, P., Tripathy, S. K., Trzeciak, B. A., Tsai, O. D., Ullrich, T., Underwood, D. G., Upsal, I., Van Buren, G., van Nieuwenhuizen, G., Vasiliev, A. N., Videbæk, F., Vokal, S., Voloshin, S. A., Vossen, A., Wang, G., Wang, Y., Wang, F., Wang, Y., Webb, J. C., Webb, G., Wen, L., Westfall, G. D., Wieman, H., Wissink, S. W., Witt, R., Wu, Y., Xiao, Z. G., Xie, W., Xie, G., Xu, J., Xu, N., Xu, Q. H., Xu, Y. F., Xu, Z., Yang, Y., Yang, Q., Yang, C., Yang, S., Ye, Z., Ye, Z., Yi, L., Yip, K., Yoo, I. -K., Yu, N., Zbroszczyk, H., Zha, W., Zhang, Z., Zhang, X. P., Zhang, J. B., Zhang, S., Zhang, J., Zhang, Y., Zhang, J., Zhang, S., Zhao, J., Zhong, C., Zhou, L., Zhou, C., Zhu, X., Zhu, Z., and Zyzak, M.. Wed . "Global Λ hyperon polarization in nuclear collisions". United States. doi:10.1038/nature23004.
@article{osti_1392218,
title = {Global Λ hyperon polarization in nuclear collisions},
author = {Adamczyk, L. and Adkins, J. K. and Agakishiev, G. and Aggarwal, M. M. and Ahammed, Z. and Ajitanand, N. N. and Alekseev, I. and Anderson, D. M. and Aoyama, R. and Aparin, A. and Arkhipkin, D. and Aschenauer, E. C. and Ashraf, M. U. and Attri, A. and Averichev, G. S. and Bai, X. and Bairathi, V. and Behera, A. and Bellwied, R. and Bhasin, A. and Bhati, A. K. and Bhattarai, P. and Bielcik, J. and Bielcikova, J. and Bland, L. C. and Bordyuzhin, I. G. and Bouchet, J. and Brandenburg, J. D. and Brandin, A. V. and Brown, D. and Bunzarov, I. and Butterworth, J. and Caines, H. and de la Barca Sánchez, M. Calderón and Campbell, J. M. and Cebra, D. and Chakaberia, I. and Chaloupka, P. and Chang, Z. and Chankova-Bunzarova, N. and Chatterjee, A. and Chattopadhyay, S. and Chen, X. and Chen, J. H. and Chen, X. and Cheng, J. and Cherney, M. and Christie, W. and Contin, G. and Crawford, H. J. and Das, S. and De Silva, L. C. and Debbe, R. R. and Dedovich, T. G. and Deng, J. and Derevschikov, A. A. and Didenko, L. and Dilks, C. and Dong, X. and Drachenberg, J. L. and Draper, J. E. and Dunkelberger, L. E. and Dunlop, J. C. and Efimov, L. G. and Elsey, N. and Engelage, J. and Eppley, G. and Esha, R. and Esumi, S. and Evdokimov, O. and Ewigleben, J. and Eyser, O. and Fatemi, R. and Fazio, S. and Federic, P. and Federicova, P. and Fedorisin, J. and Feng, Z. and Filip, P. and Finch, E. and Fisyak, Y. and Flores, C. E. and Fulek, L. and Gagliardi, C. A. and Garand, D. and Geurts, F. and Gibson, A. and Girard, M. and Grosnick, D. and Gunarathne, D. S. and Guo, Y. and Gupta, A. and Gupta, S. and Guryn, W. and Hamad, A. I. and Hamed, A. and Harlenderova, A. and Harris, J. W. and He, L. and Heppelmann, S. and Heppelmann, S. and Hirsch, A. and Hoffmann, G. W. and Horvat, S. and Huang, T. and Huang, B. and Huang, X. and Huang, H. Z. and Humanic, T. J. and Huo, P. and Igo, G. and Jacobs, W. W. and Jentsch, A. and Jia, J. and Jiang, K. and Jowzaee, S. and Judd, E. G. and Kabana, S. and Kalinkin, D. and Kang, K. and Kauder, K. and Ke, H. W. and Keane, D. and Kechechyan, A. and Khan, Z. and Kikoła, D. P. and Kisel, I. and Kisiel, A. and Kochenda, L. and Kocmanek, M. and Kollegger, T. and Kosarzewski, L. K. and Kraishan, A. F. and Kravtsov, P. and Krueger, K. and Kulathunga, N. and Kumar, L. and Kvapil, J. and Kwasizur, J. H. and Lacey, R. and Landgraf, J. M. and Landry, K. D. and Lauret, J. and Lebedev, A. and Lednicky, R. and Lee, J. H. and Li, X. and Li, C. and Li, W. and Li, Y. and Lidrych, J. and Lin, T. and Lisa, M. A. and Liu, H. and Liu, P. and Liu, Y. and Liu, F. and Ljubicic, T. and Llope, W. J. and Lomnitz, M. and Longacre, R. S. and Luo, S. and Luo, X. and Ma, G. L. and Ma, L. and Ma, Y. G. and Ma, R. and Magdy, N. and Majka, R. and Mallick, D. and Margetis, S. and Markert, C. and Matis, H. S. and Meehan, K. and Mei, J. C. and Miller, Z. W. and Minaev, N. G. and Mioduszewski, S. and Mishra, D. and Mizuno, S. and Mohanty, B. and Mondal, M. M. and Morozov, D. A. and Mustafa, M. K. and Nasim, Md. and Nayak, T. K. and Nelson, J. M. and Nie, M. and Nigmatkulov, G. and Niida, T. and Nogach, L. V. and Nonaka, T. and Nurushev, S. B. and Odyniec, G. and Ogawa, A. and Oh, K. and Okorokov, V. A. and Olvitt, D. and Page, B. S. and Pak, R. and Pandit, Y. and Panebratsev, Y. and Pawlik, B. and Pei, H. and Perkins, C. and Pile, P. and Pluta, J. and Poniatowska, K. and Porter, J. and Posik, M. and Poskanzer, A. M. and Pruthi, N. K. and Przybycien, M. and Putschke, J. and Qiu, H. and Quintero, A. and Ramachandran, S. and Ray, R. L. and Reed, R. and Rehbein, M. J. and Ritter, H. G. and Roberts, J. B. and Rogachevskiy, O. V. and Romero, J. L. and Roth, J. D. and Ruan, L. and Rusnak, J. and Rusnakova, O. and Sahoo, N. R. and Sahu, P. K. and Salur, S. and Sandweiss, J. and Saur, M. and Schambach, J. and Schmah, A. M. and Schmidke, W. B. and Schmitz, N. and Schweid, B. R. and Seger, J. and Sergeeva, M. and Seyboth, P. and Shah, N. and Shahaliev, E. and Shanmuganathan, P. V. and Shao, M. and Sharma, A. and Sharma, M. K. and Shen, W. Q. and Shi, Z. and Shi, S. S. and Shou, Q. Y. and Sichtermann, E. P. and Sikora, R. and Simko, M. and Singha, S. and Skoby, M. J. and Smirnov, N. and Smirnov, D. and Solyst, W. and Song, L. and Sorensen, P. and Spinka, H. M. and Srivastava, B. and Stanislaus, T. D. S. and Strikhanov, M. and Stringfellow, B. and Sugiura, T. and Sumbera, M. and Summa, B. and Sun, Y. and Sun, X. M. and Sun, X. and Surrow, B. and Svirida, D. N. and Tang, A. H. and Tang, Z. and Taranenko, A. and Tarnowsky, T. and Tawfik, A. and Thäder, J. and Thomas, J. H. and Timmins, A. R. and Tlusty, D. and Todoroki, T. and Tokarev, M. and Trentalange, S. and Tribble, R. E. and Tribedy, P. and Tripathy, S. K. and Trzeciak, B. A. and Tsai, O. D. and Ullrich, T. and Underwood, D. G. and Upsal, I. and Van Buren, G. and van Nieuwenhuizen, G. and Vasiliev, A. N. and Videbæk, F. and Vokal, S. and Voloshin, S. A. and Vossen, A. and Wang, G. and Wang, Y. and Wang, F. and Wang, Y. and Webb, J. C. and Webb, G. and Wen, L. and Westfall, G. D. and Wieman, H. and Wissink, S. W. and Witt, R. and Wu, Y. and Xiao, Z. G. and Xie, W. and Xie, G. and Xu, J. and Xu, N. and Xu, Q. H. and Xu, Y. F. and Xu, Z. and Yang, Y. and Yang, Q. and Yang, C. and Yang, S. and Ye, Z. and Ye, Z. and Yi, L. and Yip, K. and Yoo, I. -K. and Yu, N. and Zbroszczyk, H. and Zha, W. and Zhang, Z. and Zhang, X. P. and Zhang, J. B. and Zhang, S. and Zhang, J. and Zhang, Y. and Zhang, J. and Zhang, S. and Zhao, J. and Zhong, C. and Zhou, L. and Zhou, C. and Zhu, X. and Zhu, Z. and Zyzak, M.},
abstractNote = {The extreme energy densities generated by ultra-relativistic collisions between heavy atomic nuclei produce a state of matter that behaves surprisingly like a fluid, with exceptionally high temperature and low viscosity. Non-central collisions have angular momenta of the order of 1,000ћ, and the resulting fluid may have a strong vortical structure that must be understood to describe the fluid properly. The vortical structure is also of particular interest because the restoration of fundamental symmetries of quantum chromodynamics is expected to produce novel physical effects in the presence of strong vorticity. But, no experimental indications of fluid vorticity in heavy ion collisions have yet been found. Since vorticity represents a local rotational structure of the fluid, spin–orbit coupling can lead to preferential orientation of particle spins along the direction of rotation. Here we present measurements of an alignment between the global angular momentum of a non-central collision and the spin of emitted particles (in this case the collision occurs between gold nuclei and produces Λ baryons), revealing that the fluid produced in heavy ion collisions is the most vortical system so far observed. (At high energies, this fluid is a quark–gluon plasma.) We find that Λ and hyperons show a positive polarization of the order of a few per cent, consistent with some hydrodynamic predictions. (A hyperon is a particle composed of three quarks, at least one of which is a strange quark; the remainder are up and down quarks, found in protons and neutrons.) A previous measurement that reported a null result, that is, zero polarization, at higher collision energies is seen to be consistent with the trend of our observations, though with larger statistical uncertainties. Furthermore, these data provide experimental access to the vortical structure of the nearly ideal liquid created in a heavy ion collision and should prove valuable in the development of hydrodynamic models that quantitatively connect observations to the theory of the strong force.},
doi = {10.1038/nature23004},
journal = {Nature (London)},
number = 7665,
volume = 548,
place = {United States},
year = {Wed Aug 02 00:00:00 EDT 2017},
month = {Wed Aug 02 00:00:00 EDT 2017}
}

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