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J-PARC E15 実験の今後の展望

J-PARC E15 実験の今後の展望. 平岩聡彦 京都大学 On behalf of the J-PARC E15 collaboration. Outline. Introduction experiment & theory of K - pp J-PARC E15 experiment method setup background Possibility of E15 exp. @ 30kW Summary & outlook. Introduction. Low-energy KN interaction.

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J-PARC E15 実験の今後の展望

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  1. J-PARC E15実験の今後の展望 平岩聡彦 京都大学 On behalf of the J-PARC E15 collaboration

  2. Outline • Introduction • experiment & theory of K-pp • J-PARC E15 experiment • method • setup • background • Possibility of E15 exp. @ 30kW • Summary & outlook ストレンジネス研究会2010

  3. Introduction ストレンジネス研究会2010

  4. Low-energy KN interaction • K-nucleon interaction • Low energy Kp scattering • Kaonic hydrogen level shift (KEK-PS E228) • Kaonic nuclei • Kaon bound states with a few nucleons • Extract the information about KN interaction below KN threshold M.Iwasaki et al. , PRL 78, 3067(1997) Attractive (I=0) How strong? ストレンジネス研究会2010

  5. Experimental results on K-pp • FINUDA • Invariant mass of back-to-back Lp pairs in K- absorptions • B = 115±6(stat)±4(syst)MeVG = 67±14(stat)±3(syst) MeV • DISTO • pp  K+X+, X+ pL • B = 105±2(stat)±5(syst)MeVG = 118±8(stat)±10(syst )MeV T.Yamazaki et al. , PRL 104, 132502 (2010) ストレンジネス研究会2010 M.Agnello et al. , PRL 94, 212303 (2005)

  6. Theoretical study on K-pp • K-pp bound states should exist! • A deep state or shallow state? • Decay width is sufficiently narrow? ストレンジネス研究会2010

  7. Formation spectra : in-flight 3He(K-,n) K- + 3He  “K-pp” + n @ PK=1GeV/c, q=0º YA potential quasi-free Signal can be clearly seen! bound K- conversion K- escape Integrated production cross section amounts to 3.5 mb/sr. ストレンジネス研究会2010 T.Koike and T.Harada. , PLB652 (2007) 262

  8. Search for K-pp bound states at J-PARC • E15 experiment via in-flight (K-, n) reaction on 3He. • E27 experiment via d(p+, K+) reaction. ストレンジネス研究会2010

  9. J-PARC E15 collaboration ストレンジネス研究会2010

  10. neutron K-pp cluster Formation Decay Mode to decay charged particles p L p- p J-PARC E15 experiment Experimental search for K-pp bound states usingin-flight (K-, n) reaction on 3He 3He K- 1 GeV/c Missing mass Spectroscopyvia neutron We can observe both the “Formation” and “Decay” of K-pp bound state Invariant mass reconstruction ストレンジネス研究会2010

  11. Experimental Setup J-PARC K1.8BR Invariant mass resolution for K-pp (B.E. 100 MeV) s ~ 13 MeV/c2 (sCDC=200mm, B=0.7T) Neutron counter Beam sweep magnet Cylindrical Detector System Neutron 1.0 GeV/c K- TOF length 15m Beamline Spectrometer Missing mass resolusion for K-pp (B.E. 100 MeV ) s ~ 9.2 MeV/c2 (Pn~1.3GeV/c, sTOF=150ps) ストレンジネス研究会2010

  12. Identification of Lpn final state by CDS & NC • Possible background- S0pn final state + g missing- QF-L + p missing- QF-S, SL conv. + p missing Other processes can be clearly separated!! ストレンジネス研究会2010

  13. Background?? : two nucleon absorption 2NA + LN rescattering / SL conversion looks like a “signal” ?? (2NA itself is not a problem.) 12C(K-,n)@ 1GeV/c De Broglie wave length @ 1 GeV/c ~ 1.2 fm NN distance in 3He ~ 2.25 fm Proc. Jpn. Academy,Series B83 (2007) 144. 12C(K-,p) These probabilities are expected to be very small ... Anyway, let’s see how they look like! 2NA is very small ストレンジネス研究会2010 T. Kishimoto et al., Prog.Theor.Phys. 118(2007)181.

  14. Signal(DISTO) vs Background(2NA+SL conv.) 2NA and S-L conversion 2NA and S-L conversion (B.E.=100MeV G=100MeV) ストレンジネス研究会2010

  15. Signal(DISTO) vs Background(2NA+rescattering) 2NA and s-wave scattering 2NA and s-wave scattering ストレンジネス研究会2010

  16. Possibility of the E15 experiment with 30kW PS operation ストレンジネス研究会2010

  17. Yield estimation (1week run @30kW) • Yield = NKaon x t x (ds/dW)q=0º x R x r x A x e x e • Nkaon : kaons per spill (@30kW)  300k /spill • t : target  0.08 [g/cm3] / 3 [g/mol] x 6.02x1023 [mol-1] x 9.3 [cm] ~ 1.4 x 1023 [cm-2] • (ds/dW)q=0º: differential cross section @ q=0º  3 [mb/sr] • R : Kpp decay branch (Lp)  0.5 • r : branching ratio (L  p-p)  0.63 • A : acceptance (NC + CDS)  5.3 [msr] • e : NC efficiency  0.3 • e : overall efficiency (trigger, detector, ana etc...)  0.7 PLB 652 (2007) 262. PRC80 (2009) 055208 4.5 x103 signals can be collected in 1 week run with 30kW operation. ストレンジネス研究会2010

  18. Missing mass of 3He(K-, n) Lp/S0pdecay branches stand on same mass! 4,500 signals (Lp) + 4,500 signals (S0p) ~ Total 9,000 signals ( [Lp] : [S0p] = 0.5 : 0.5 ) ストレンジネス研究会2010

  19. Improvement of statistics Statistical improvement can be achieved by “one proton missing”. • Missing proton resolution: 28  0.3 MeV/c2 (s) • Acceptance (NC+CDS) • 3body phase space  0.079% (all detected)  0.12% (one proton missing) • K-pp (B=100MeV, G=100MeV)  0.042%(all detected)  0.098% (one proton missing) x2 Lpn final state still can be identified! ストレンジネス研究会2010

  20. Summary & outlook • J-PARC E15 experiment • search for a K-pp bound state using in-flight (K- n) reaction on 3He • measure the missing mass in (K-, n) reaction and the invariant mass via the decay of K-pp, simultaneously. • E15 experiment @ 30kW operation • Enough statistics for the first physics data can be collected within a week if the cross section is ~ 3 mb/sr. (2% of the requested beam time) • We wish to start E15 exp. as soon as possible . (after E17) ストレンジネス研究会2010

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