Two-particle correlations of /ΛΛ and /Λ¯Λ¯ pairs have been studied in multihadronic Z decays recorded with the ALEPH detector at LEP in the years from 1992 to 1995. The correlations were measured as a function of the four-momentum difference Q of the pair. A depletion of events is observed in the region /Q<2 GeV which could arise from the effects of Fermi-Dirac statistics. In addition the spin content of the /Λ pair system has been determined. For /2 GeV the fraction of pairs with spin one is consistent with the value of 0.75 expected for a statistical spin mixture, whilst for /Q<2 GeV this fraction is found to be lower. For /ΛΛ¯ pairs, where no Fermi-Dirac correlations are expected, the spin one fraction is measured to be consistent with 0.75 over the entire analysed Q range.
Fermi-Dirac correlations in lambda pairs in hadronic Z decays / R. Barate, D. Decamp, P. Ghez, C. Goy, J.P. Lees, F. Martin, E. Merle, M.N. Minard, B. Pietrzyk, R. Alemany, S. Bravo, M.P. Casado, M. Chmeissani, J.M. Crespo, E. Fernandez, M. Fernandez-Bosman, L. Garrido, E. Grauges, A. Juste, M. Martinez, G. Merino, R. Miquel, L.M. Mir, A. Pacheco, I. Riu, H. Ruiz, A. Colaleo, D. Creanza, M. de Palma, G. Iaselli, G. Maggi, M. Maggi, S. Nuzzo, A. Ranieri, G. Raso, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, A. Tricomi, G. Zito, X. Huang, J. Lin, Q. Ouyang, T. Wang, Y. Xie, R. Xu, S. Xue, J. Zhang, L. Zhang, W. Zhao, D. Abbaneo, G. Boix, O. Buchmuller, M. Cattaneo, F. Cerutti, V. Ciulli, G. Dissertori, H. Drevermann, R.W. Forty, M. Frank, T.C. Greening, A.W. Halley, J.B. Hansen, J. Harvey, P. Janot, B. Jost, I. Lehraus, O. Leroy, P. Mato, A. Minten, A. Moutoussi, F. Ranjard, G. Rolandi, D. Schlatter, M. Schmitt, O. Schneider, P. Spagnolo, W. Tejessy, F. Teubert, E. Tournefier, A.E. Wright, Z. Ajaltouni, F. Badaud, G. Chazelle, O. Deschamps, A. Falvard, C. Ferdi, P. Gay, C. Guicheney, P. Henrard, J. Jousset, B. Michel, S. Monteil, J.C. Montret, D. Pallin, P. Perret, F. Podlyski, J.D. Hansen, J.R. Hansen, P.H. Hansen, B.S. Nilsson, B. Rensch, A. Waananen, G. Daskalakis, A. Kyriakis, C. Markou, E. Simopoulou, I. Siotis, A. Vayaki, A. Blondel, G. Bonneaud, J.C. Brient, A. Rouge, M. Rumpf, M. Swynghedauw, M. Verderi, H. Videau, E. Focardi, G. Parrini, K. Zachariadou, M. Corden, C. Georgiopoulos, A. Antonelli, G. Bencivenni, G. Bologna, F. Bossi, P. Campana, G. Capon, V. Chiarella, P. Laurelli, G. Mannocchi, F. Murtas, G.P. Murtas, L. Passalacqua, M. Pepe-Altarelli, L. Curtis, J.G. Lynch, P. Negus, V. O'Shea, C. Raine, P. Teixeira-Dias, A.S. Thompson, R. Cavanaugh, S. Dhamotharan, C. Geweniger, P. Hanke, G. Hansper, V. Hepp, E.E. Kluge, A. Putzer, J. Sommer, K. Tittel, S. Werner, M. Wunsch, R. Beuselinck, D.M. Binnie, W. Cameron, P.J. Dornan, M. Girone, S. Goodsir, E.B. Martin, N. Marinelli, A. Sciaba, J.K. Sedgbeer, E. J. Thomson, M.D. Williams, V.M. Ghete, P. Girtler, E. Kneringer, D. Kuhn, G. Rudolph, C.K. Bowdery, P.G. Buck, A.J. Finch, F. Foster, G. Hughes, R.W.L. Jones, N.A. Robertson, M.I. Williams, I. Giehl, K. Jakobs, K. Kleinknecht, G. Quast, B. Renk, E. Rohne, H.G. Sander, H. Wachsmuth, C. Zeitnitz, J.J. Aubert, A. Bonissent, J. Carr, P. Coyle, P. Payre, D. Rousseau, M. Aleppo, M. Antonelli, F. Ragusa, V. Buescher, H. Dietl, G. Ganis, K. Huttmann, G. Lutjens, C. Mannert, W. Manner, H.G. Moser, S. Schael, R. Settles, H. Seywerd, H. Stenzel, W. Wiedenmann, G. Wolf, P. Azzurri, J. Boucrot, O. Callot, S. Chen, A. Cordier, M. Davier, L. Duflot, J.F. Grivaz, P. Heusse, A. Jacholkowska, F. Le Diberder, J. Lefrancois, A.M. Lutz, M.H. Schune, J.J. Veillet, I. Videau, D. Zerwas, G. Bagliesi, T. Boccali, C. Bozzi, G. Calderini, R. Dell'Orso, I. Ferrante, L. Foa, A. Giassi, A. Gregorio, F. Ligabue, P.S. Marrocchesi, A. Messineo, F. Palla, G. Rizzo, G. Sanguinetti, G. Sguazzoni, R. Tenchini, A. Venturi, P.G. Verdini, G.A. Blair, G. Cowan, M.G. Green, T. Medcalf, J.A. Strong, D.R. Botterill, R.W. Clifft, T.R. Edgecock, P.R. Norton, J.C. Thompson, I.R. Tomalin, B. Bloch-Devaux, P. Colas, S. Emery, W. Kozanecki, E. Lancon, M.C. Lemaire, E. Locci, P. Perez, J. Rander, J.F. Renardy, A. Roussarie, J.P. Schuller, J. Schwindling, A. Trabelsi, B. Vallage, S.N. Black, J.H. Dann, R.P. Johnson, H.Y. Kim, N. Konstantinidis, A.M. Litke, M.A. McNeil, G. Taylor, C.N. Booth, S. Cartwright, F. Combley, M. Lehto, L.F. Thompson, K. Affholderbach, Armin Boehrer, S. Brandt, C. Grupen, J. Hess, A. Misiejuk, G. Prange, U. Sieler, G. Giannini, B. Gobbo, J.E. Rothberg, S. Wasserbaech, S.R. Armstrong, P. Elmer, D.P.S. Ferguson, Y. Gao, S. Gonzalez, O.J. Hayes, H. Hu, S. Jin, J. Kile, P.A. McNamara, J. Nielsen, W. Orejudos, Y.B. Pan, Y. Saadi, I.J. Scott, J. Walsh, J.H. von Wimmersperg-Toeller, S.L. Wu, X. Wu, G. Zobernig. - In: PHYSICS LETTERS. SECTION B. - ISSN 0370-2693. - 475:3/4(2000), pp. 395-406.
Fermi-Dirac correlations in lambda pairs in hadronic Z decays
M. Aleppo;F. Ragusa;
2000
Abstract
Two-particle correlations of /ΛΛ and /Λ¯Λ¯ pairs have been studied in multihadronic Z decays recorded with the ALEPH detector at LEP in the years from 1992 to 1995. The correlations were measured as a function of the four-momentum difference Q of the pair. A depletion of events is observed in the region /Q<2 GeV which could arise from the effects of Fermi-Dirac statistics. In addition the spin content of the /Λ pair system has been determined. For /2 GeV the fraction of pairs with spin one is consistent with the value of 0.75 expected for a statistical spin mixture, whilst for /Q<2 GeV this fraction is found to be lower. For /ΛΛ¯ pairs, where no Fermi-Dirac correlations are expected, the spin one fraction is measured to be consistent with 0.75 over the entire analysed Q range.
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