Transverse polarization of $\Lambda$ hyperons from quasireal   photoproduction on nuclei

The HERMES Collaboration: A. Airapetian; N. Akopov; Z. Akopov; E.C.; Aschenauer; W. Augustyniak; R. Avakian; A. Avetissian; E. Avetisyan; S.; Belostotski; N. Bianchi; H.P. Blok; A. Borissov; J. Bowles; I. Brodski; V.; Bryzgalov; J. Burns; M. Capiluppi; G.P. Capitani; E. Cisbani; G. Ciullo; M.; Contalbrigo; P.F. Dalpiaz; W. Deconinck; R. De Leo; L. De Nardo; E. De; Sanctis; M. Diefenthaler; P. Di Nezza; M. D\"uren; M. Ehrenfried; G.; Elbakian; F. Ellinghaus; R. Fabbri; A. Fantoni; L. Felawka; S. Frullani; D.; Gabbert; G. Gapienko; V. Gapienko; F. Garibaldi; G. Gavrilov; V. Gharibyan,; F. Giordano; S. Gliske; M. Golembiovskaya; C. Hadjidakis; M. Hartig; D.; Hasch; A. Hillenbrand; M. Hoek; Y. Holler; I. Hristova; Y. Imazu; A.; Ivanilov; H.E. Jackson; H.S. Jo; S. Joosten; R. Kaiser; G. Karyan; T. Keri,; E. Kinney; A. Kisselev; N. Kobayashi; V. Korotkov; V. Kozlov; P. Kravchenko,; V.G. Krivokhijine; L. Lagamba; L. Lapik\'as; I. Lehmann; P. Lenisa; A.; L\'opez Ruiz; W. Lorenzon; X.-G. Lu; B.-Q. Ma; D. Mahon; N.C.R. Makins; S.I.; Manaenkov; Y. Mao; B. Marianski; A. Martinez de la Ossa; H. Marukyan; C.A.; Miller; Y. Miyachi; A. Movsisyan; V. Muccifora; M. Murray; A. Mussgiller; E.; Nappi; Y. Naryshkin; A. Nass; M. Negodaev; W.-D. Nowak; L.L. Pappalardo; R.; Perez-Benito; P.E. Reimer; A.R. Reolon; C. Riedl; K. Rith; G. Rosner; A.; Rostomyan; J. Rubin; D. Ryckbosch; Y. Salomatin; F. Sanftl; A. Sch\"afer; G.; Schnell; K.P. Sch\"uler; B. Seitz; T.-A. Shibata; V. Shutov; M. Stancari; M.; Statera; E. Steffens; J.J.M. Steijger; J. Stewart; F. Stinzing; S. Taroian,; A. Terkulov; R. Truty; A. Trzcinski; M. Tytgat; A. Vandenbroucke; Y. Van; Haarlem; C. Van Hulse; D. Veretennikov; V. Vikhrov; I. Vilardi; S. Wang; S.; Yaschenko; Z. Ye; W. Yu; V. Zagrebelnyy; D. Zeiler; B. Zihlmann; P. Zupranski

arXiv:1406.3236·hep-ex·October 22, 2014

Transverse polarization of $\Lambda$ hyperons from quasireal photoproduction on nuclei

The HERMES Collaboration: A. Airapetian, N. Akopov, Z. Akopov, E.C., Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S., Belostotski, N. Bianchi, H.P. Blok, A. Borissov, J. Bowles, I. Brodski, V., Bryzgalov, J. Burns, M. Capiluppi, G.P. Capitani, E. Cisbani

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TL;DR

This study measures the transverse polarization of Lambda hyperons produced via quasireal photoproduction on various nuclei, revealing positive polarization for light targets and near-zero for heavier nuclei, providing insights into spin transfer mechanisms.

Contribution

It presents the first systematic measurement of Lambda hyperon polarization across different nuclear targets in quasireal photoproduction, highlighting nuclear dependence of polarization effects.

Findings

01

Positive polarization observed for light nuclei

02

Polarization compatible with zero for heavy nuclei

03

Nuclear dependence of hyperon polarization

Abstract

The transverse polarization of $Λ$ hyperons was measured in inclusive quasireal photoproduction for various target nuclei ranging from hydrogen to xenon. The data were obtained by the HERMES experiment at HERA using the 27.6 GeV lepton beam and nuclear gas targets internal to the lepton storage ring. The polarization observed is positive for light target nuclei and is compatible with zero for krypton and xenon.

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