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Status of E391a experiment for the rare decay

Status of E391a experiment for the rare decay. October 3, 2005 @ ICFP 2005 Takao INAGAKI 　（ KEK) for the E391a collaboration. Theoretically it is very pure and clean, but it is a very rare decay. Possible Scenario.

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Status of E391a experiment for the rare decay

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  1. Status of E391a experiment for the rare decay October 3, 2005 @ ICFP 2005 Takao INAGAKI　（KEK) for the E391a collaboration

  2. Theoretically it is very pure and clean, but it is a very rare decay

  3. Possible Scenario Recently confirmed that the theoretical uncertainty is also very small in most of calculations of new physics. hep-ph/050517

  4. Experimentally very challenging • Small branching fraction  Any tiny effects are possible sources of background • Weak kinematical constraint (all neutrals, three-body decay with invisible neutrinos, etc)  Not easy to separate the signal from background This is the reason why the present limit stays at 5.9X10-7 (KTeV, 2000) and why E391a is the first dedicated experiment in spite of a theoretically dream channel.

  5. Strategy: step-by-step approach E391a at KEK 12 GeV PS O(10-10) An experiment at JPARC 50 GeV PS O(10-14)

  6. Collaboration and status of E391a • E391a collaboration • 11 institutes, ~50 members from 5 countries Univ. of Chicago, JINR, KEK. Kyoto Univ., NDA, National Taiwan Univ., Osaka Univ., Pusan National Univ., RCNP, Saga Univ., Yamagata Univ. • Status of experiment • First data taking was carried out from Feb/2004 to July/2004 • Second data taking (Run-II) was carried out from Feb/2005 to April/2005 ●The third data taking (Run-III) is scheduled in Nov/2005

  7. 0.25 GeV/c 0.13 GeV/c

  8. Three important tools

  9. Additional discussion about detection inefficiency, which causes photon veto miss ・The inefficiency strongly depends on gamma energy. It is large at low energy 　　　　　　　　　　　　↓ Hiｇｈ PT selection ・The inefficiency strongly depends on the detection threshold 　　　　　　　　　　　　　↓ Low detection threshold Concern：how we can lower it under high rate environment. Understand the detector response at low energy deposit.

  10. Final plot Using 10% sample of Run-1

  11. What we have learned

  12. BackgroundBy understanding the sources of side-band events

  13. Halo neutron Kpi2: negligibly small Core neutron

  14. Back splash It is clearly observed for the main barrel having both-end readout. Time difference (position) Mean time

  15. Introduction of J-PARC our next playground

  16. Configuration of the accelerators • Neutron • Muon

  17. Layout K0 line is included in the construction plan

  18. Construction Schedule

  19. Summary • is one of the pure and clean channels in the field of quark flavor physics. It provides a critical and unambiguous check of the Standard Model. • 2. E391a, which is the first dedicated experiment, has started at KEK 12-GeV PS successfully. • 3. Using 10 % sample of Run I, we obtained a new limit of 2.9×10-7 (90%cl). • 4. We are learning many things, background sources, the rate of extremely low energy deposit etc. They must be quite important for a future extension. • 5. J-PARC, which is expected to be our next play-ground, is now being constructed steadily. We are preparing a proposal.

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