Phi Decay Experiment(KEKPS E325) Home Page

We measure phi-meson decays in nuclear media, both in the mesonic and leptonic decay mode. By observing both decay modes simultaneously and by examining a possible change of the branching ratio , mass shift of K and phi in nuclear media will be studied. The phinomena can be interpreted as a consequence of the partial restoration of the chiral symmetry in nuclear media.

この実験は、原子核中での φ中間子の崩壊(K中間子対・電子対への崩壊比、 および invariant mass 分布)を測定して、核物質中での カイラル対称性の部分的回復に関する実験的検証をおこなうものである。

status:(2005 July)

We started the R&D of the experiment in 1994. The spectrometer was built in the EP1B primary beamline at KEK-PS in 1996-97. Physics run were performed 1997-2002, and spectrometer was decomposed in 2003 Apr.
First physics result shows the modification of rho/omega meson are publised as PRL86(2001)5019-5022.
Now we are in the last stage of the data analysis, using high statistics data taken in 2001/2002(6th/7th run). The result of rho/omega -> ee decay channel is reported in nucl-ex/0504016 and submitted. The result of phi -> ee channel will be presented at coming QM2005. The analysis for phi -> KK channel is also on going and will be presented in JPS 2005 HAWAII.

run history

First physics run (970515-0619).
(phi->KK only)
Second run (9805)
(phi->KK and phi->ee simultaneously)
Third run (9907)
4th run (000622-0707)
5th run (0012)
6th run (011114-1223)
7th (the last) run (0202)


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Last modified: Thu Jul 21 16:00:00 JST 2005