Prof. Takashi Nakano, "RIBF Nuclear Physics Seminar", "New Theta+ result from LEPS

by Prof. Takashi Nakano (RCNP)

Friday 25 Jan 2013, 13:30 → 15:00 Asia/Tokyo

RIBF 2F　大会議室

TITLE: New Theta+ result from LEPS. ABSTRACT: New results of the penta-quark Theta+ study in the gamma d -> K+ K- p n reactions from LEPS will be presented. Firstly, in order to check the validity of the 5-sigma evidence that we obtained by analyzing the data taken in 2002-2003, the same analysis method was applied to the new data taken in 2006-2007. A strong narrow peak in the Fermi-motion corrected K- missing mass was not reproduced in the new data set. Then, we applied an exclusive analysis to the both data sets, where background processes due to gamma p reactions were identified by energy loss information in a plastic counter, which was placed just after the liquid-deuterium target. A clear signal enhancement was seen in the gamma n contributions, and a part of the inconsistency was tuned out to be due to fluctuations in the proton contribution of the previous data set. The signal enhancement was also confirmed by a Monte-Carlo based exclusive analysis.