The polarization of Λ baryons from Z decays is studied with the Aleph apparatus. Evidence of longitudinal polarization of s quarks from Z decay is observed for the first time. The measured longitudinal Λ polarization is PLΛ = −0.32 ± 0.07 for View the MathML source. This agrees with the prediction of −0.39 ± 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back ΛView the MathML source pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction.
Measurement of Λ polarization from Z decays / D. Buskulic;I. De Bonis;D. Decamp;P. Ghez;C. Goy;J.-P. Lees;A. Lucotte;M.-N. Minard;P. Odier;B. Pietrzyk;M. Chmeissani;J.M. Crespo;M. Delfino;I. Efthymiopoulos;E. Fernandez;M. Fernandez-Bosman;Ll. Garrido;A. Juste;M. Martinez;S. Orteu;A. Pacheco;C. Padilla;F. Palla;A. Pascual;J.A. Perlas;I. Riu;F. Sanchez;F. Teubert;A. Colaleo;D. Creanza;M. de Palma;A. Farilla;G. Gelao;M. Girone;G. Iaselli;G. Maggi;M. Maggi;N. Marinelli;S. Natali;S. Nuzzo;A. Ranieri;G. Raso;F. Romano;F. Ruggieri;G. Selvaggi;L. Silvestris;P. Tempesta;G. Zito;X. Huang;J. Lin;Q. Ouyang;T. Wang;Y. Xie;R. Xu;S. Xue;J. Zhang;L. Zhang;W. Zhao;R. Alemany;A.O. Bazarko;G. Bonvicini;M. Cattaneo;P. Comas;P. Coyle;H. Drevermann;R.W. Forty;M. Frank;R. Hagelberg;J. Harvey;R. Jacobsen;P. Janot;B. Jost;E. Kneringer;J. Knobloch;I. Lehraus;E.B. Martin;P. Mato;A. Minten;R. Miquel;Ll.M. Mir;L. Moneta;T. Oest;P. Palazzi;J.R. Pater;J.-F. Pusztaszeri;F. Ranjard;P. Rensing;L. Rolandi;D. Schlatter;M. Schmelling;O. Schneider;W. Tejessy;I.R. Tomalin;A. Venturi;H. Wachsmuth;A. Wagner;T. Wildish;W. Witzeling;J. Wotschack;Z. Ajlatouni;A. Barrès;C. Boyer;A. Falvard;P. Gay;C. Guicheney;P. Henrard;J. Jousset;B. Michel;S. Monteil;J-C. Montret;D. Pallin;P. Perret;F. Podlyski;J. Proriol;J.-M. Rossignol;T. Fearnley;J.B. Hansen;J.D. Hansen;J.R. Hansen;P.H. Hansen;B.S. Nilsson;A. Wäänänen;A. Kyriakis;C. Markou;E. Simopoulou;I. Siotis;A. Vayaki;K. Zachariadou;A. Blondel;G. Bonneaud;J.C. Brient;P. Bourdon;A. Rougé;M. Rumpf;R. Tanaka;A. Valassi;M. Verderi;H. Videau;D.J. Candlin;M.I. Parsons;E. Focardi;G. Parrini;M. Corden;C. Georgiopoulos;D.E. Jaffe;A. Antonelli;G. Bencivenni;G. Bologna;F. Bossi;P. Campana;G. Capon;D. Casper;V. Chiarella;G. Felici;P. Laurelli;G. Mannocchi;F. Murtas;G.P. Murtas;L. Passalacqua;M. Pepe-Altarelli;L. Curtis;S.J. Dorris;A.W. Halley;I.G. Knowles;J.G. Lynch;V. O'Shea;C. Raine;P. Reeves;J.M. Scarr;K. Smith;A.S. Thompson;F. Thomson;S. Thorn;R.M. Turnbull;U. Becker;C. Geweniger;G. Graefe;P. Hanke;G. Hansper;V. Hepp;E.E. Kluge;A. Putzer;B. Rensch;M. Schmidt;J. Sommer;H. Stenzel;K. Tittel;S. Werner;M. Wunsch;D. Abbaneo;R. Beuselinck;D.M. Binnie;W. Cameron;P.J. Dornan;P.J. Dornan;A. Moutoussi;J. Nash;J.K. Sedgbeer;A.M. Stacey;M.D. Williams;G. Dissertori;P. Girtler;D. Kuhn;G. Rudolph;C.K. Bowdery;T.J. Brodbeck;P. Colrain;G. Crawford;A.J. Finch;F. Foster;G. Hughes;T. Sloan;E.P. Whelan;M.I. Williams;A. Galla;A.M. Greene;K. Kleinknecht;G. Quast;B. Renk;E. Rohne;H.-G. Sander;P. van Gemmeren;C. Zeitnitz;J.J. Aubert;A.M. Bencheikh;C. Benchouk;A. Bonissent;G. Bujosa;D. Calvet;J. Carr;C. Diaconu;F. Etienne;N. Konstantinidis;D. Nicod;P. Payre;D. Rousseau;M. Talby;A. Sadouki;M. Thulasidas;K. Trabelsi;I. Abt;R. Assmann;C. Bauer;W. Blum;H. Dietl;F. Dydak;G. Ganis;C. Gotzhein;K. Jakobs;H. Kroha;G. Lütjens;G. Lutz;W. Männer;H.-G. Moser;R. Richter;A. Rosado-Schlosser;S. Schael;R. Settles;H. Seywerd;R.St. Denis;W. Wiedenmann;G. Wolf;J. Boucrot;O. Callot;A. Cordier;M. Davier;L. Duflot;J.-F. Grivaz;Ph. Heusse;M. Jacquet;D.W. Kim;F. Le Diberder;J. Lefrançois;A.-M. Lutz;I. Nikolic;H.J. Park;I.C. Park;M.-H. Schune;S. Simion;J.-J. Veillet;I. Videau;P. Azzurri;G. Bagliesi;G. Batignani;S. Bettarini;C. Bozzi;G. Calderini;M. Carpinelli;M.A. Ciocci;V. Ciulli;R. Dell'Orso;R. Fantechi;I. Ferrante;L. Foà;F. Forti;A. Giassi;M.A. Giorgi;A. Gregorio;F. Ligabue;A. Lusiani;P.S. Marrocchesi;A. Messineo;G. Rizzo;G. Sanguinetti;A. Sciabà;P. Spagnolo;J. Steinberger;R. Tenchini;G. Tonelli;C. Vannini;P.G. Verdini;J. Walsh;A.P. Betteridge;G.A. Blair;L.M. Bryant;F. Cerutti;J.T. Chambers;Y. Gao;M.G. Green;D.L. Johnson;T. Medcalf;P. Perrodo;J.A. Strong;J.H. von Wimmersperg-Toeller;D.R. Botterill;R.W. Clifft;T.R. Edgecock;S. Haywood;P. Maley;P.R. Norton;J.C. Thompson;A.E. Wright;B. Bloch-Devaux;P. Colas;S. Emery;W. Kozanecki;E. Lançon;M.C. Lemaire;E. Locci;B. Marx;P. Perez;J. Rander;J.-F. Renardy;A. Roussarie;J.-P. Schuller;J. Schwindling;A. Trabelsi;B. Vallage;R.P. Johnson;H.Y. Kim;A.M. Litke;M.A. McNeil;G. Taylor;A. Beddall;C.N. Booth;R. Boswell;C.A.J. Brew;S. Cartwright;F. Combley;A. Koksal;M. Letho;W.M. Newton;C. Rankin;J. Reeve;L.F. Thompson;A. Böhrer;S. Brandt;V. Büscher;G. Cowan;C. Grupen;G. Lutters;J. Minguet-Rodriguez;F. Rivera;P. Saraiva;L. Smolik;F. Stephan;M. Aleppo;M. Apollonio;L. Bosisio;R. Della Marina;G. Giannini;B. Gobbo;G. Musolino;F. Ragusa;J. Rothberg;S. Wasserbaech;S.R. Armstrong;L. Bellantoni;P. Elmer;Z. Feng;D.P.S. Ferguson;Y.S. Gao;S. González;J. Grahl;T.C. Greening;J.L. Harton;O.J. Hayes;H. Hu;P.A. McNamara;J.M. Nachtman;W. Orejudos;Y.B. Pan;Y. Saadi;M. Schmitt;I.J. Scott;V. Sharma;J.D. Turk;A.M. Walsh;Sau Lan Wu;X. Wu;J.M. Yamartino;M. Zheng;G. Zobernig. - In: PHYSICS LETTERS. SECTION B. - ISSN 0370-2693. - ELETTRONICO. - 374:(1996), pp. 319-330. [10.1016/0370-2693(96)00300-0]
Measurement of Λ polarization from Z decays
FOCARDI, ETTORE;CIULLI, VITALIANO;
1996
Abstract
The polarization of Λ baryons from Z decays is studied with the Aleph apparatus. Evidence of longitudinal polarization of s quarks from Z decay is observed for the first time. The measured longitudinal Λ polarization is PLΛ = −0.32 ± 0.07 for View the MathML source. This agrees with the prediction of −0.39 ± 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back ΛView the MathML source pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction.I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.