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Abdallah, J.; Adzic, P.; Anashkin, E.; Andringa, S.; Anjos, N.; Ask, S.; Asman, B.; Baillon, P.; Barbier, R.; Bardin, D.; Berggren, M.; Besson, N.; Blom, M.; Bonesini, M.; Borisov, G.; Botner, O.; Bracko, M.; Brenner, R.; Brunet, J.M.; Camporesi, T.; Cavallo, F.; Chudoba, J.; Cieslik, K.; Collins, P.; Della Ricca, G.; De Boer, W.; De Clercq, C.; De Min, A.; de Paula, L.; Doroba, K.; Ekelof, T.; Fanourakis, G.; Ferrer, A.; Ferro, F.; Foeth, H.; Garcia, C.; Grosdidier, G.; Grzelak, K.; Jarlskog, G.; Johansson, E.K.; Jungermann, L.; Katsanevas, S.; Katsoufis, E.; King, B.T.; Kjaer, N.J.; Leder, G.; Leinonen, L.; Leitner, R.; Liko, D.; Malek, A.; Maltezos, S.; Marco, J.; Marin, J-C.; Matorras, F.; Mazzucato, F.; Mc Nulty, R.; Meroni, C.; Moenig, K.; Montenegro, J.; Morettini, P.; Muenich, K.; Mulders, M.; Myklebust, T.; Nawrocki, K.; Nikolenko, M.; Oblakowska-Mucha, A.; Onofre, A.; Oyanguren, A.; Palka, H.; Papadopoulou, Th.D.; Parodi, F.; Passon, O.; Piotto, E.; Polok, G.; Pozdniakov, V.; Pukhaeva, N.; Pullia, A.; Rehn, J.; Richard, F.; Romero, A.; Sadovsky, A.; Sander, C.; Siebel, M.; Stanitzki, M.; Szczekowski, M.; Tegenfeldt, F.; Timmermans, J.; Tkatchev, L.; Tobin, M.; Treille, D.; Valenti, G.; Van Dam, P.; van Remortel, N.; Van Vulpen, I.; Vegni, G.; Vilanova, D.; Vitale, L.; Washbrook, A.J.; Winter, M.; Zupan, M.
Physics letters. B, 2007, Letnik: 653, Številka: 2Journal Article
The quark model does not exclude states composed of more than three quarks, like pentaquark systems. Controversial evidence for such states has been published in the last years, in particular: for a strange pentaquark Θ ( 1540 ) + ; for a double-strange state, the Ξ ( 1862 ) − − , subsequently called Φ ( 1860 ) − − ; and for a charmed state, the Θ c ( 3100 ) 0 . If confirmed, a full pentaquark family might exist; such pentaquark states could be produced in e + e − annihilations near the Z energy. In this Letter a search for pentaquarks is described using the DELPHI detector at LEP, characterized by powerful particle identification sub-systems crucial in the separation of the signal from the background for these states. At 95% CL, upper limits are set on the production rates 〈 N 〉 of such particles and their charge-conjugate state per Z decay: 〈 N Θ + 〉 × Br ( Θ + → p K S 0 ) < 5.1 × 10 −4 , 〈 N Θ + + 〉 < 1.6 × 10 −3 , 〈 N Φ ( 1860 ) − − 〉 × Br ( Φ ( 1860 ) − − → Ξ − π − ) < 2.9 × 10 −4 , 〈 N Θ c ( 3100 ) 0 〉 × Br ( Θ c ( 3100 ) 0 → D ∗ + p ¯ ) < 8.8 × 10 −4 .
