Evidence for collectivity in pp collisions at the LHC

V. Khachatryan , M. Besançon (1) , F. Couderc (1) , M. Dejardin (1) , D. Denegri (1) , B. Fabbro (1) , J.L. Faure (1) , C. Favaro (1) , F. Ferri (1) , S. Ganjour (1) , S. Ghosh , A. Givernaud (1) , P. Gras (1) , G. Hamel De Monchenault (1) , P. Jarry (1) , I. Kucher (1) , E. Locci (1) , M. Machet (1) , J. Malcles (1) , J. Rander (1) , A. Rosowsky (1) , M. Titov (1) , A. Zghiche (1) , A. Abdulsalam (2) , I. Antropov (2) , S. Baffioni (2) , F. Beaudette (2) , P. Busson (2) , L. Cadamuro (2) , E. Chapon (2) , C. Charlot (2) , O. Davignon (2) , R. Granier De Cassagnac (2) , M. Jo (2) , S. Lisniak (2) , P. Mine (2) , M. Nguyen (2) , C. Ochando (2) , G. Ortona (2) , P. Paganini (2) , P. Pigard (2) , S. Regnard (2) , R. Salerno (2) , Y. Sirois (2) , T. Strebler (2) , Y. Yilmaz (2) , A. Zabi (2) , J.-L. Agram (3) , J. Andrea (3) , A. Aubin (3) , D. Bloch (3) , J.-M. Brom (3) , M. Buttignol (3) , E.C. Chabert (3) , N. Chanon (3) , C. Collard (3) , E. Conte (3) , X. Coubez (3) , J.-C. Fontaine (3) , D. Gele (3) , U. Goerlach (3) , A.-C. Le Bihan (3) , K. Skovpen (3) , P. Van Hove (3) , S. Gadrat (4) , S. Beauceron (5) , C. Bernet (5) , G. Boudoul (5) , E. Bouvier (5) , C.A. Carrillo Montoya (5) , R. Chierici (5) , D. Contardo (5) , B. Courbon (5) , P. Depasse (5) , H. El Mamouni (5) , J. Fan (5) , J. Fay (5) , S. Gascon (5) , M. Gouzevitch (5) , G. Grenier (5) , B. Ille (5) , Fabienne Lagarde (5) , I.B. Laktineh (5) , M. Lethuillier (5) , L. Mirabito (5) , A.L. Pequegnot (5) , S. Perries (5) , A. Popov (5) , D. Sabes (5) , V. Sordini (5) , M. Vander Donckt (5) , P. Verdier (5) , S. Viret (5)

1 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
2 LLR - Laboratoire Leprince-Ringuet
3 IPHC - Institut Pluridisciplinaire Hubert Curien
4 CC-IN2P3 - Centre de Calcul de l'IN2P3
5 IPNL - Institut de Physique Nucléaire de Lyon

Measurements of two- and multi-particle angular correlations in pp collisions at sqrt(s) = 5, 7, and 13 TeV are presented as a function of charged-particle multiplicity. The data, corresponding to integrated luminosities of 1.0 inverse picobarns (5 TeV), 6.2 inverse picobarns (7 TeV), and 0.7 inverse picobarns (13 TeV), were collected using the CMS detector at the LHC. The second-order (v[2]) and third-order (v[3]) azimuthal anisotropy harmonics of unidentified charged particles, as well as v[2] of K0 short and Lambda/anti-Lambda particles, are extracted from long-range two-particle correlations as functions of particle multiplicity and transverse momentum. For high-multiplicity pp events, a mass ordering is observed for the v[2] values of charged hadrons (mostly pions), K0 short, and Lambda/anti-Lambda, with lighter particle species exhibiting a stronger azimuthal anisotropy signal below pt~2 GeV/c. For 13 TeV data, the v[2] signals are also extracted from four- and six-particle correlations for the first time in pp collisions, with comparable magnitude to those from two-particle correlations. These observations are similar to those seen in pPb and PbPb collisions, and support the interpretation of a collective origin for the observed long-range correlations in high-multiplicity pp collisions.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique des Hautes Energies - Expérience [hep-ex]

V. Khachatryan, M. Besançon, F. Couderc, M. Dejardin, D. Denegri, et al.. Evidence for collectivity in pp collisions at the LHC. Physics Letters B, 2017, 765, pp.193-220. ⟨10.1016/j.physletb.2016.12.009⟩. ⟨in2p3-01334567⟩