Evidence for an exotic S= -2, Q= -2 baryon resonance in proton-proton collisions at the CERN SPS.
Results of resonance searches in the Xi(-)pi(-), Xi(-)pi(+), Xi;(+)pi(-), and Xi;(+)pi(+) invariant mass spectra in proton-proton collisions at sqrt[s]=17.2 GeV are presented. Evidence is shown for the existence of a narrow Xi(-)pi(-) baryon resonance with mass of 1.862+/-0.002 GeV/c(2) and width below the detector resolution of about 0.018 GeV/c(2). The significance is estimated to be above 4.2sigma. This state is a candidate for the hypothetical exotic Xi(--)(3/2) baryon with S=-2, I=3 / 2, and a quark content of (dsdsū). At the same mass, a peak is observed in the Xi(-)pi(+) spectrum which is a candidate for the Xi(0)(3/2) member of this isospin quartet with a quark content of (dsus[-]d). The corresponding antibaryon spectra also show enhancements at the same invariant mass.
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Fachbereich Physik der Universität, D-60486 Frankfurt, Germany.
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Baatar
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Barna
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Bartke
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Betev
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Białkowska
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Billmeier
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Blume
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Boimska
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Bracinik
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Bramm
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Brun
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Buncić
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Christakoglou
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Cramer
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Flierl
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Fodor
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Friese
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Gál
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Gaździcki
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Georgopoulos
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Hegyi
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Höhne
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Karev
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Kolesnikov
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Korus
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Kowalski
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van Leeuwen
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Lévai
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Litov
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Makariev
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Malakhov
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Markert
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Meurer
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Mitrovski
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Molnár
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Renfordt
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Trainor
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Vassiliou
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Vranić
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Wetzler
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Yoo
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Zimányi
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