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Stopped K beam at J-PARC

Nov. 4, 2005 Korea J-PARC seminar. Stopped K beam at J-PARC. - A branch option of K1.1 -. Designed by J.Doornbos Optics design of a K0.8 branch Performance Pion contamination Comments on K1.1. LoI’s with stopped K beam. LoI-04 Study of the Rare Decay K ＋ →  ＋  with

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Stopped K beam at J-PARC

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  1. Nov. 4, 2005 Korea J-PARC seminar Stopped K beam at J-PARC - A branch option of K1.1 - Designed by J.Doornbos Optics design of a K0.8 branch Performance Pion contamination Comments on K1.1

  2. LoI’s with stopped K beam LoI-04 Study of the Rare Decay K＋→＋with Stopped Kaon Beam at J-PARC LoI-05Measurement of the K0L→ Branching Ratio LoI-16 Study the Kaon Decay Physics at JHF LoI-19 Search for T-violation in K＋decays LoI-20 Precise Measurement of the K＋→0e＋(Ke3) Branching Ratio

  3. Possibility of a stopped beam in Phase 1 K0 Line（KL beam） E391a detector K0.8 Line（stopped K±) as a branch of K1.1 Use of K1.1 by lowering beam momentum

  4. Phase-2 Hall K0.8 Use of T2 • Hall size =60m (W) x 100 m (L) • More than 2 target stations

  5. Can we use K1.1?

  6. A branch option of K1.1designed by J.Doornbos • A branch of K1.1 at B3 • Common use of the upstream part up to MS1 • Macroscopic time sharing with K1.1 • Effective use of IFY • Single-stage DCS • Moderate beam intensity -> • Feasibility to start the T-violation experiment • with minor upgrades of the Toroidal Detector

  7. Layout of the K0.8 branch

  8. Design principle • Effective use of wedge focus to make HFOC • Suppression of slit-scattered pions at HFOC • Cloud pion source definition by IFY

  9. Replacement of B3

  10. Beam optics First order beam envelop @ 0.8 GeV/c x’= 43 mr y’= 9 mr x = 3.5 mm y = 2.0 mm Dp/p = 0 Length = 19.06 m

  11. Momentum dispersion R16(FF) = 0 R26(FF) ≠0

  12. Beamline elements

  13. IFY profile ZGOUBI calculation Source size Dx = 2 mm Dy = 2 mm

  14. MS1 profile DCS = 550 kV/10cm Pion kick = 2.2 mr ZGOUBI calculation

  15. HFOC profile ZGOUBI calculation

  16. Final focus ZGOUBI calculation • R16 = 0 • cf. R16≠0 • @ K5 • → source of • systematic errors • R26 ≠0 • less problematic • longer target

  17. Dp/p momentum acceptance

  18. Angle acceptance

  19. Pion contamination Higher order aberration Slit scattering Cloud pions from Ks (ct =2.7 cm) simulation by ZGOUBI Aberration: y = R33y0 + R34f + A1fq + A2fq2 + B1fd + B2fd2 + ・・ A1, B1 = 0 by adjusting the sextupoles S1 and S2 A2, B2 were minimized by optimizing the octupole O1

  20. Rejection of slit-scattered pions x-profile at HFOC Slit scattering simulation with REVMOC IFY and MS1 with 30 cm thickness tapered (20 mr at both ends)

  21. Rejection of cloud pions Accepted y region at the production target Pion source of x = -2 ~ +2 cm y = -1 ~ +3 cm was assumed. ( c.f. ct = 2.7 cm) IFY = 5 mm MS1 = 4 mm HFOC = 1.6 cm HFOC is effective !

  22. Kaon yield andp/K ratio

  23. Cloud pion contamination

  24. Summary of the K0.8 beam • Acc = 6 msr % Dp/p • c.f. Acc (K1.1) ~ 4 msr % Dp/p • Acc (LESB3) ~ 50 msr % Dp/p • IK+ ~ ( 1~ a few) × 106/s • p+/K+ < 0.5 assuming sp/sK = 500 • Beam spot : dx ~ dy ~ 1 cm << @K5

  25. Further studies • Realistic source distribution in T1 • rotating target angle • cloud pion source • Effects of proton beam halo • p/K ratio optimization

  26. Comments on the K1.1 optics Sector type B4 with HFOC effective suppression of p+

  27. p/K separation at MS1

  28. MS2 profile

  29. Final focus of the new design

  30. Rejection of cloud pion by HFOC

  31. Conclusion • The C-type branch of K1.1 for stopped beam is feasible • The intermediate vertical focus IFY plays an important role. • The installation of an IFY slit is very necessary. • A switching mechanism has to be considered for B3+Q7. • We will propose this option of the low momentum • separate K-line together with the experiment proposal • There is no concrete plan yet for funding.

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