Evidence for a narrow baryonic state decaying to K0Sp and K0Sp¯ in deep inelastic scattering at HERA
Abstract
A resonance search has been made in the K0Sp and K0Sp¯ invariant-mass spectrum measured with the ZEUS detector at HERA using an integrated luminosity of 121 pb-1. The search was performed in the central rapidity region of inclusive deep inelastic scattering at an ep centre-of-mass energy of 300-318 GeV for exchanged photon virtuality, Q2, above 1 GeV2. Recent results from fixed-target experiments give evidence for a narrow baryon resonance decaying to K+n and K0Sp, interpreted as a pentaquark. The results presented here support the existence of such state, with a mass of 1521.5±1.5(stat.)+2.8-1.7(syst.) MeV and a Gaussian width consistent with the experimental resolution of 2 MeV. The signal is visible at high Q2 and, for Q2>20 GeV2, contains 221±48 events. The probability of a similar signal anywhere in the range 1500-1560 MeV arising from fluctuations of the background is below 6×10-5.
- Publication:
-
Physics Letters B
- Pub Date:
- July 2004
- DOI:
- 10.1016/j.physletb.2004.04.024
- arXiv:
- arXiv:hep-ex/0403051
- Bibcode:
- 2004PhLB..591....7C
- Keywords:
-
- High Energy Physics - Experiment
- E-Print:
- 4 eps figures, 15 pages, 1 table, accepted by Physics Letters B