Spectroscopic study of Λ(1405) via the in-flight (K -,n) reaction on deuteron.

Transcription

1 Spectroscopic study of Λ(1405) via the in-flight (K -,n) reaction on deuteron. SHUN Enomoto RCNP, Osaka Univ. For J-PARC E31 collaboration Oct. 4, 2012

2 J-PARC E31 Collaboration S. Ajimura1, G. Beer2, H. Bhang3, M.Bragadireanu8,P. Buehler4, L. Busso5,6, M. Cargnelli4, S. Choi3, C. Curceanu8, S. Enomoto1, D. Faso5, H. Fujioka13, Y. Fujiwara12, T. Fukuda11, C. Guaraldo8, T. Hashimoto12,R. Hayano12, T. Hiraiwa 13, M. Iio9,K. Inoue1, N. Ishibashi17, T. Ishikawa12, S. Ishimoto14, T. Ishiwatari4, K. Itahashi9, M. Iwai14, M. Iwasaki9,10,S. Kawasaki1, P. Kienle15, H. Kou10,J. Marton4, Y. Matsuda12, Y. Mizoi 10, O. Morra5, T. Nagae13, H. Noumi 1, H. Ohnishi9, S. Okada8, H. Outa9, Y. Sada13, A. Sakaguchi17, F. Sakuma9, M. Sato12, M. Sekimoto14,H. Shi12,K. Shirotori1, D. Sirghi8, F. Sirghi8, S. Suzuki14, T. Suzuki12, H. Tatsuno12, M. Tokuda10, D. Tomono9, A. Toyoda14, K. Tsukada18, E. Widmann4, T. Yamazaki9,12, K. Yoshida17, H. Yim3, B. Wünschek4, J. Zmeskal4 1. Research Center for Nuclear Physics, Osaka University, Japan 2. University of Victoria, Canada, 3. Seoul National University, South Korea 4. Stefan Meyer Institut fur subatomare Physik, Austria, 5. INFN Sezione di Torino, Italy, 6.Universita di Torino, Italy 8. Laboratori Nazionali di Frascati dell INFN, Italy 9. RIKEN, Japan, 10. Tokyo Institute of Technology, Japan 11. Osaka Electro-Communication University, Japan, 12. University of Tokyo, Japan 13. Kyoto University, Japan, 14. High Energy Accelerator Research Organization (KEK), Japan 15. Technische Universitat Munchen, Germany, 16. INAF-IFSI, Sezione di Torino, Italy 17. Osaka University, Japan 18. Tohoku University, Japan 2

3 Contents 1:Introduction Λ(1405) The(K -,n) reaction on deuteron. 2:J-PARC E31 experiment Status Future plan & schedule 3:Summary 3

4 Is Λ(1405) KbarN bound state? 1406MeV/c 2 [one pole?] Deeply bound KbarN state. Y. Akaishi & T. Yamazaki, Phys. Rev. C65, (2002). Y. Akaishi & T. Yamazaki, Phys. Lett. B535, 70 (2002) 1420MeV/c 2 [two pole?] Chiral Unitary Model predicted. I=1 I=0 Λ(1520),3/2 - KN(1432) *(1385),3/2 + Λ(1405),1/2- -27MeV (1192),1/2 + Λ(1116),1/2 + D.Jido, J. A. Oller, E Oset, A. Ramos, U.-G. Meissner, NPA725(2003)181 Recently Experiment data pp pk + π 0 Σ 0, πσ MM spec., Zychor et al, PLB660(08)167 γp K + πσ, πσ MM spec., M. Niiyama et al, PRC78(08) γp K + πσ, πσ IM spec., K. Moriya et al, PTPS186(10)234 Direct KbarN scattering to form Λ(1405) below KbarN threshold must be investigated. 4

5 the (K -,n) reaction on deuteron. KbarN -> πσ scattering below KbarN threshold d(k -,n) reaction. π D 2 Y* P n K t n K- d(k-,n) may enhance the S-wave scattering at Θ n = 0 degree. 5

6 J-PARC E31 Experiments d(k-,n) missing mass Spin-Isospin in the final state Target(D) Decay Particle Detector (CDS) n ~1.3GeV/c 3 He(K -,n) Kpp reaction J-PARC E15 Neutron Counter (TOF) ΔT~150ps K - 1.0GeV/c Λ(1405) 15m Purely I=0 Λ(1405) and BG(NR/ *) S-wave, I=0 Λ*(1405) π 0 0,π - +,π + - S-wave, I=1 non-resonant(nr) P-wave, I=1 *(1385) π 0 Λ,π - +,π MeV/c 2? 1420MeV/c 2? S-wave Σ*(1385)? I=0,1 P-wave I=1 Λ*(1405) Non-resonant I=1 Y*(mass) KN :1432MeV 6 6

7 Expected missing mass spectra in d(k -,n) Counts * π - Σ + decay mode Counts * 70 π 0 Σ 0 decay mode Counts * 3500 π + Σ - decay mode Bubble chamber exp. data 0 K-p πσ(1660), Λ(1405)π+ MM[MeV/c 2 ] π+σ-,π-σ MeV/c 2 MM R. J. Hemingway, Nucl. Phys. B 253, 742 (1985) ( P + P P ) n 500 Calculated 0 d(k-,n) πσ By Chiral Unitary Model MM[MeV/c 2 ] D. Jido et al, EPJA42( 09)257 d 1420MeV/c 2 Simulated with Exp. Data [1] / Chiral Unitary Model [2]. X = D. Jido, A. Oller, E. Oset, A. Ramos, and G. Meissner, Nuclear Physics A 725, , 2003 D. jido, E. Oset and T. Sekihara, Eur. Phys. J A42(2009) 257 [1]R. J. Hemingway, Nucl. Phys. B 253, 742 (1985) [2]D. jido, E. Oset and T. Sekihara, Eur. Phys. J A42(2009) 257 K 2 MM[MeV/c 2 ] 7

8 J-PARC K1.8BR beam line[jun. 2012] beam dump liquid 3 He-target system CDS beam sweeping magnet neutron counter & TOFstop/proton counter 3 He(K -,n) reaction Sada, Search for Kpp, [parallel-vi] CDS[E15] Cylindrical Detector Hodoscope (CDH) Cylindrical Drift Chamber (CDC) beam line spectrometer K - 3He n 8

9 Experimental Setup for J-PARC E31 Almost the same as J-PARC E15 setup. add to only 3 item Liq. D 2 target / BPC / BPD liquid D 2 -target System CDS+ BPD+BPC BPC/BPD To identify backward emitted proton in Λ(1405) π 0 Σ 0. π 0- Σ + 0 / final π + Σ - state final state Λ(1405) 0 π 0± Λγπ π (n 0 π (p ± ) π - )γ π 0 π+ p K - BPC BPD CDH CDC D 2 π- n 9

10 Backward Proton Detector (BPD & BPC) BPD (Backward Proton Detector) ü 70 plastic scintillators ü MPPC ü σ(tof T0-BPD ) = 160ps Measure a ToF. Determine momentum. de [MeV] de[mev] Response BPD seg24 de for vs BPD-T0 π/p beams π 1GeV/c BPD-T0 TOF [ns] π ectbpd24t0_pi Entries 1759 Mean x Mean y RMS x RMS y Proton ToF [ns] BPD BPC (Backward Proton Chamber) ü wire drift chamber ü planer type, 8 layers Track a proton trajectory Determine a decay vertex. Y plane[cm] Target image Request CDH hit X plane[cm] BPC 10

11 Plan & Schedule J-PARC E31 Proposed beam Time Request: 120shifts, with 27kw primary proton ~19200[Λ(1405) π + Σ - ],~4800[Λ(1405) π - Σ + ],~350[Λ(1405) π 0 Σ 0 ] Pilot run(plan) Wish to have a short term run before summer When 1week*20kW.. Confirm that the d(k-,n) reaction really enhances an S- wave KbarN scattering to form Λ(1405). Collect 2400π + Σ - (>old Bubble Chamber Exp.), 600π - Σ + (new) can provide new data in a short time!! Full scale run Collect π 0 Σ 0 mode spring~ (after J-PARC long shutdown). 11

12 Summary We propose to study Λ(1405) hyperon resonance via the d(k-,n) reaction. KbarN πσ scattering below KbarN threshold how Λ(1405) is dynamically formed from initial KbarN state. E31 is ready to run!! (E15setup), D 2 target, BPC and BPD are ready We wish to start data acquisition before summer We are sure to provide new data on Λ(1405) π - Σ + and π - Σ + in a short time, and Λ(1405) π 0 Σ 0 finally. Moltes gracies! 12

13 BACK UP 13

14 LEPS: γp K + Σπ M. Niiyama et al., PRC78, (2008) E γ = GeV ENTRIES/ 10 MeV/c 2. COSY-ANKE: pp pk + Λ*( π 0 Σ 0 ) I. Zychor et al. PLB660, 167( ±23 ev. p K =673~834 MeV/c K-d -> π + Σ - n(bubble C.) 1420 MeV/c 2 CLAS: γp K + Σπ K. Moriya et al., PTP Suppl.186, 234(2010) 14 O. Braun et al., NPB129, 1(1977)

15 Liq. D2 target 4K G-M refrigerator to liquefy Easy to control temperature w/ H. E. Heat Exchanger heater Demonstration to liquefy Hydrogen. Temp. can be controlled around 20K. H2 D2 BP 20.3K 23.8K MP 14.0K 18.7K 15

16 Identifying π - π + final state Λ(1405), ( Σ(1385) ) π - Σ + π - n π + Λ(1405), ( Σ(1385) ) π + Σ - π + n π - 16

17 Simple the reaction mechanism. ->d(k -,n)π + Σ - at P K- =800MeV/c K- D KN n D(K-,n)X(1400) P_KN P KN ( Lab) ~ 250MeV / c, PKN ( CM) ~ 160MeV / c 10deg 4deg L r p = < 1, r ~ 1fm, c ~ 200MeV fm 0deg Enhancement of Λ* production at θn=0 BackGround from Σ* will be reduced S-wave KbarN scattering is dominant at θ n =0 degree. 17

18 ID & Efficiency for Λ*->π 0 Σ 0 Λ(1405) 0 π 0 Λγπ 0 (p π - )γ π 0 NR/ (1385) Λπ 0 pπ - π 0 MM ) 2 2 Y = ( PY ) = ( PK + Pd Pn Pp P π P:fourth momentum Σ*->Λπ 0 Λ*->π 0 Σ 0 2 Λ*- > 0 π 0 Γ(Λ*)/Γ(Σ*)~1 Proton Detector Resolution(σ) 1 2 MM 2 (MeV/c 2 ) Σ*->Λπ 0 contaminatio n Λπ 0 (contamination)=(λπ [2])/(Λπ) 18

19 J-PARC E31 Experiment Spectroscopic study of Hyperon Resonances below KbarN threthold via the (K -,n) reaction on Deuteron. K - 1.0GeV/c MM Target(D) X = ( P + P P ) n K d Decay Particle Detector (CDS) Λ(1405) 2 n ~1.3GeV/c 15m To measure Λ* mass spectra by Missing Mass. σ MM ~9MeV/c 2 at P K- = 1.0GeV/c To Identify Λ* decay mode by CDS J-PARC E15@J-PARC K1.8BR Neutron counter (TOF) ΔT~150ps Σ - π +,Σ + π - I=0 Λ* I=1 NR I=1 Σ* Σ 0 π 0 I=0 Λ* Λπ 0 NR or Σ* 19

20 E31 experiment Intensity Secondary beam 30GeV-27kW(6s) K-:1.0GeV.c Beam intensity(ib) 2.0*10^5per pulse 6s spill interval Cross section(dσ/dω) Solid angle(δω) Decay mode efficiency(ε M ) 220µb/sr sr Λ(1405) π+ - π+π-n Λ(1405) π- + π-π+n Λ(1405) π0 0 π0π-p Λ(1405) π+ - π+π-n Λ(1405) π- + π-π+n Λ(1405) π0 0 π0π-p Target 4.1*10^23 Liquid deuteron(8cm) Yield(120shift) ~19200 ~4800 ~350 Λ(1405) π+π-n Λ(1405) π-π+n Λ(1405) π0π-p Y dσ dω = Ib nt ΔΩ ε R ε M ε A R:reconstruction(0.24)A:analysis(0.9) 20