Limits for the central production of Theta+ and Xi(--)pentaquarks in 920-GeV pA collisions.
We have searched for Theta+(1540) and Xi(--)(1862) pentaquark candidates in proton-induced reactions on C, Ti, and W targets at midrapidity and square root of s = 41.6 GeV. In 2 x 10(8) inelastic events we find no evidence for narrow (sigma approximately 5 MeV) signals in the Theta+ --> pK0(S) and Xi(--) --> Xi- pi- channels; our 95% C.L. upper limits (UL) for the inclusive production cross section times branching fraction B dsigma/dy/(y approximately 0) are (4-16) mub/N for a Theta+ mass between 1521 and 1555 MeV, and 2.5 mub/N for the Xi(--). The UL of the yield ratio of Theta+/Lambda(1520) < (3-12)% is significantly lower than model predictions. Our UL of B Xi(--)/Xi(1530)0 < 4% is at variance with the results that have provided the first evidence for the Xi(--).
Abt
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Max-Planck-Institut für Physik, Werner-Heisenberg-Institut, D-80805 Munich, Germany.
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Eisele
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Fabbri
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Faccioli
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Funcke
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Krauss
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Lanyov
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Lewendel
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Lomonosov
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Matchikhilian
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Medin
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Nowak
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Núñez Pardo de Vera
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Ouchrif
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Peralta
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Piccinini
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Pleier
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Poli
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Popov
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Pugatch
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Pylypchenko
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Pyrlik
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Reeves
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Rick
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Rostovtseva
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Rybnikov
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Sánchez
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Schmelling
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Schmidt
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Schwenninger
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Stanovnik
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Tikhomirov
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van Eldik
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Wahlberg
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Walter
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Wegener
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