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。


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.
High statistics run were performed in 2001/2002(6th/7th run).
The result of rho/omega -> ee decay channel is published in PRL96(2006)092301.
The cross section of omega/phi in the ee decay channel is published in PRC74(2006)025201.
The result of phi -> ee channel is published in PRL98(2007)042501.
The result of phi -> KK channel is published in PRL98(2007)152302.

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: Fri Jul 16 22:03:32 2010