A search for the Theta(+) in the reaction gamma d -> pK(-)K(+)n was completed using the CLAS detector at Jefferson Lab. A study of the same reaction, published earlier, reported the observation of a narrow Theta(+) resonance. The present experiment, with more than 30 times the integrated luminosity of our earlier measurement, does not show any evidence for a narrow pentaquark resonance. The angle-integrated upper limit on Theta(+) production in the mass range of 1.52-1.56 GeV/c(2) for the gamma d -> pK(-)Theta(+) reaction is 0.3 nb (95% C.L.). This upper limit depends on assumptions made for the mass and angular distribution of Theta(+) production. Using Lambda(1520) production as an empirical measure of rescattering in the deuteron, the cross section upper limit for the elementary gamma n -> K-Theta(+) reaction is estimated to be a factor of 10 higher, i.e., similar to 3 nb (95% C.L.).
SEARCH FOR THE THETA+ PENTAQUARK IN THE REACTION Y D ---> P K- K+ N
RICCO, GIOVANNI;TAIUTI, MAURO GINO;
2006-01-01
Abstract
A search for the Theta(+) in the reaction gamma d -> pK(-)K(+)n was completed using the CLAS detector at Jefferson Lab. A study of the same reaction, published earlier, reported the observation of a narrow Theta(+) resonance. The present experiment, with more than 30 times the integrated luminosity of our earlier measurement, does not show any evidence for a narrow pentaquark resonance. The angle-integrated upper limit on Theta(+) production in the mass range of 1.52-1.56 GeV/c(2) for the gamma d -> pK(-)Theta(+) reaction is 0.3 nb (95% C.L.). This upper limit depends on assumptions made for the mass and angular distribution of Theta(+) production. Using Lambda(1520) production as an empirical measure of rescattering in the deuteron, the cross section upper limit for the elementary gamma n -> K-Theta(+) reaction is estimated to be a factor of 10 higher, i.e., similar to 3 nb (95% C.L.).
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