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Observation of Λ Hyperon Local Polarization in p-Pb Collisions at sqrt[s_{NN}]=8.16  TeV.

Publication ,  Journal Article
Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, JW; Benato, L; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, PS; Li, A ...
Published in: Phys Rev Lett
September 26, 2025

The polarization of the Λ and Λ[over ¯] hyperons along the beam direction has been measured in proton-lead (p-Pb) collisions at a center-of-mass energy per nucleon pair of 8.16 TeV. The data were obtained with the CMS detector at the LHC and correspond to an integrated luminosity of 186.0±6.5  nb^{-1}. A significant azimuthal dependence of the hyperon polarization, characterized by the second-order Fourier sine coefficient P_{z,s2}, is observed. The P_{z,s2} values decrease as a function of charged particle multiplicity, but increase with transverse momentum. A hydrodynamic model that describes the observed P_{z,s2} values in nucleus-nucleus collisions by introducing vorticity effects does not reproduce either the sign or the magnitude of the p-Pb results. These observations pose a challenge to the current theoretical implementation of spin polarization in heavy ion collisions and offer new insights into the origin of spin polarization in hadronic collisions at LHC energies.

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Published In

Phys Rev Lett

DOI

EISSN

1079-7114

Publication Date

September 26, 2025

Volume

135

Issue

13

Start / End Page

132301

Location

United States

Related Subject Headings

  • General Physics
  • 51 Physical sciences
  • 49 Mathematical sciences
  • 40 Engineering
  • 09 Engineering
  • 02 Physical Sciences
  • 01 Mathematical Sciences
 

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Hayrapetyan, A., Tumasyan, A., Adam, W., Andrejkovic, J. W., Benato, L., Bergauer, T., … Kramer, T. (2025). Observation of Λ Hyperon Local Polarization in p-Pb Collisions at sqrt[s_{NN}]=8.16  TeV. Phys Rev Lett, 135(13), 132301. https://doi.org/10.1103/6ywq-gm61
Hayrapetyan, A., A. Tumasyan, W. Adam, J. W. Andrejkovic, L. Benato, T. Bergauer, S. Chatterjee, et al. “Observation of Λ Hyperon Local Polarization in p-Pb Collisions at sqrt[s_{NN}]=8.16  TeV.Phys Rev Lett 135, no. 13 (September 26, 2025): 132301. https://doi.org/10.1103/6ywq-gm61.
Hayrapetyan A, Tumasyan A, Adam W, Andrejkovic JW, Benato L, Bergauer T, et al. Observation of Λ Hyperon Local Polarization in p-Pb Collisions at sqrt[s_{NN}]=8.16  TeV. Phys Rev Lett. 2025 Sep 26;135(13):132301.
Hayrapetyan, A., et al. “Observation of Λ Hyperon Local Polarization in p-Pb Collisions at sqrt[s_{NN}]=8.16  TeV.Phys Rev Lett, vol. 135, no. 13, Sept. 2025, p. 132301. Pubmed, doi:10.1103/6ywq-gm61.
Hayrapetyan A, Tumasyan A, Adam W, Andrejkovic JW, Benato L, Bergauer T, Chatterjee S, Damanakis K, Dragicevic M, Hussain PS, Jeitler M, Krammer N, Li A, Liko D, Mikulec I, Schieck J, Schöfbeck R, Schwarz D, Sonawane M, Waltenberger W, Wulz C-E, Janssen T, Van Laer T, Van Mechelen P, Breugelmans N, D’Hondt J, Dansana S, De Moor A, Delcourt M, Heyen F, Lowette S, Makarenko I, Müller D, Tavernier S, Tytgat M, Van Onsem GP, Van Putte S, Vannerom D, Bilin B, Clerbaux B, Das AK, De Bruyn I, De Lentdecker G, Evard H, Favart L, Gianneios P, Jaramillo J, Khalilzadeh A, Khan FA, Lee K, Malara A, Paredes S, Shahzad MA, Thomas L, Vanden Bemden M, Vander Velde C, Vanlaer P, De Coen M, Dobur D, Gokbulut G, Hong Y, Knolle J, Lambrecht L, Marckx D, Mota Amarilo K, Skovpen K, Van Den Bossche N, van der Linden J, Wezenbeek L, Benecke A, Bethani A, Bruno G, Caputo C, De Favereau De Jeneret J, Delaere C, Donertas IS, Giammanco A, Guzel AO, Jain S, Lemaitre V, Lidrych J, Mastrapasqua P, Tran TT, Alves GA, 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Qin X, Sun X, Wang D, Yang H, Zhang L, Zhao Y, Zhou C, Yang S, You Z, Jaffel K, Lu N, Bauer G, Li B, Yi K, Zhang J, Chen Z, Li Y, Lin Z, Lu C, Xiao M, Avila C, Barbosa Trujillo DA, Cabrera A, Florez C, Fraga J, Reyes Vega JA, Ramirez F, Rendón C, Rodriguez M, Ruales Barbosa AA, Ruiz Alvarez JD, Giljanovic D, Godinovic N, Lelas D, Sculac A, Kovac M, Petkovic A, Sculac T, Bargassa P, Brigljevic V, Chitroda BK, Ferencek D, Jakovcic K, Starodumov A, Susa T, Attikis A, Christoforou K, Hadjiagapiou A, Leonidou C, Mousa J, Nicolaou C, Paizanos L, Ptochos F, Razis PA, Rykaczewski H, Saka H, Stepennov A, Finger M, Kveton A, Ayala E, Carrera Jarrin E, Abdelalim AA, Elgammal S, Ellithi Kamel A, Mahmoud MA, Mohammed Y, Ehataht K, Kadastik M, Lange T, Nandan S, Nielsen C, Pata J, Raidal M, Tani L, Veelken C, Kirschenmann H, Osterberg K, Voutilainen M, Bharthuar S, Bin Norjoharuddeen N, Brücken E, Garcia F, Inkaew P, Kallonen KTS, Lampén T, Lassila-Perini K, Lehti S, Lindén T, Myllymäki M, Rantanen MM, Siikonen H, Tuominiemi J, Luukka P, Petrow H, Besancon M, Couderc F, Dejardin M, Denegri D, Faure JL, Ferri F, Ganjour S, Gras P, Hamel de Monchenault G, Kumar M, Lohezic V, Malcles J, Orlandi F, Portales L, Rosowsky A, Sahin MÖ, Savoy-Navarro A, Simkina P, Titov M, Tornago M, Beaudette F, Boldrini G, Busson P, Cappati A, Charlot C, Chiusi M, Cuisset TD, Damas F, Davignon O, De Wit A, Ehle IT, Fontana Santos Alves BA, Ghosh S, Gilbert A, Granier de Cassagnac R, Hakimi A, Harikrishnan B, Kalipoliti L, Liu G, Nguyen M, Ochando C, Salerno R, Sauvan JB, Sirois Y, Urda Gómez L, Vernazza E, Zabi A, Zghiche A, Agram J-L, Andrea J, Apparu D, Bloch D, Brom J-M, Chabert EC, Collard C, Falke S, Goerlach U, Haeberle R, Le Bihan A-C, Meena M, Poncet O, Saha G, Sessini MA, Van Hove P, Vaucelle P, Di Florio A, Amram D, Beauceron S, Blancon B, Boudoul G, Chanon N, Contardo D, Depasse P, Dozen C, El Mamouni H, Fay J, Gascon S, Gouzevitch M, Greenberg C, Grenier G, Ille B, Jourd’huy E, Laktineh IB, 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Jeppe L, Kaech B, Kasemann M, Kleinwort C, Kogler R, Komm M, Krücker D, Lange W, Leyva Pernia D, Lipka K, Lohmann W, Lorkowski F, Mankel R, Melzer-Pellmann I-A, Mendizabal Morentin M, Meyer AB, Milella G, Moral Figueroa K, Mussgiller A, Nair LP, Niedziela J, Nürnberg A, Otarid Y, Park J, Ranken E, Raspereza A, Rastorguev D, Rübenach J, Rygaard L, Saggio A, Scham M, Schnake S, Schütze P, Schwanenberger C, Selivanova D, Sharko K, Shchedrolosiev M, Stafford D, Vazzoler F, Ventura Barroso A, Walsh R, Wang Q, Wichmann K, Wiens L, Wissing C, Yang Y, Zimermmane Castro Santos A, Albrecht A, Albrecht S, Antonello M, Bein S, Bollweg S, Bonanomi M, Connor P, El Morabit K, Fischer Y, Garutti E, Grohsjean A, Haller J, Hundhausen D, Jabusch HR, Kasieczka G, Keicher P, Klanner R, Korcari W, Kramer T. Observation of Λ Hyperon Local Polarization in p-Pb Collisions at sqrt[s_{NN}]=8.16  TeV. Phys Rev Lett. 2025 Sep 26;135(13):132301.

Published In

Phys Rev Lett

DOI

EISSN

1079-7114

Publication Date

September 26, 2025

Volume

135

Issue

13

Start / End Page

132301

Location

United States

Related Subject Headings

  • General Physics
  • 51 Physical sciences
  • 49 Mathematical sciences
  • 40 Engineering
  • 09 Engineering
  • 02 Physical Sciences
  • 01 Mathematical Sciences