Study of Neutron-Rich  Hypernuclei Tomokazu FUKUDA Osaka Electro-Communication University 2013/09/091EFB 22

2 Ordinary Nuclei Non Charge-Exchange Single CX Double CX Isospin=3/2 or 2 Isospin=0 or 1/2 KEK-E521 J-PARC E10 Expand the Hypernuclear Chart Hyperfragments by Emulsion Exp.

ΛN-ΣN Mixing in Λ Hypernuclei 2013/09/09EFB 223 if core isospin=0  A( I =0) if core isospin  0  A( I  0) OK! NN NNNN NNNN NNNN 290MeV 77MeV S=0 S= -1 ordinarynuclei hypernuclei Important in neutron-rich Λ-hypernuclei (large isospin)  A * ( I  0) Small wave function overlap B.F. Gibson et al. PRC 6 (1998) 433c.

2013/09/09EFB 224 large isospin  N-  N mixing effect –  N-  N mixing effect  － N interaction is not yet known study of – study of  － hypernuclei is also important Quasi-particle EoS in neutron star

2013/09/09EFB 225 KEK-PS-E521 P. K. Saha, et al., PRL94(2005) Li +  2.5 MeV FWHM g.s. Cross sections 11.3±1.9 nb/sr - p  =1.20 GeV/c ～ 1/ ±0.6  b/sr (1.2 GeV/c) - p  =1.05 GeV/c 5.8±2.2 nb/sr  spectrum by DCX (  -,K + ) reaction at 1.2GeV/c First production of neutron-rich  hypernuclei 11.3±1.9 nb/sr

2013/09/09EFB 226 Two-step process : Doorway Theoretical Analysis by T. Harada One-step process : via  - doorways caused by  N-  N coupling

7 Two-step process : Phys.At.Nucl.66(2003)1651 arXiv:nucl-th/ v1 -- The momentum dependence of the cross section is different from that of the data. Exp.data. Two-step Pioneer theoretical works by Tretyakova and Lanskoy.

8  spectrum by DCX (  -,K + ) reaction at 1.2GeV/c 10 B is fixed. P  - =0.57 % Harada, Umeya, Hirabayashi, PRC79(2009) Spreading potential dep. -W=-W= (p  ) (s  ) 9 Li +L The calculated spectrum with -W  = MeV can reproduce the shape of the data in the continuum region, and these values of -W  are consistent with the analysis of  - QF production by the (  -, K + ) reactions. Results (1) Two-step mechanism

EFB % ss pp 0.57 % 0.68 % 0.47 % 0.30 % Coupling  -  potential dep. is fixed. 10 B Harada, Umeya, Hirabayashi, PRC79(2009) With the order of V X = MeV (P  - ~ 0.5 %), the calculated spectra can fairly reproduce the data. Results (2)  spectrum by DCX (  -,K + ) reaction at 1.2GeV/c Not take into account a fine structure

2013/09/09EFB ΛH6ΛH

6 Λ H FINUDA 2013/09/09EFB Li(stopped K -,π + ) reaction 6 Li(stopped K -,π + ) reaction Measured formation and weak decay in coincidence Measured formation and weak decay in coincidence cut on T(π + )+T(π - ) cut on T(π + )+T(π - ) 3 events of candidates 3 events of candidates 11 M. Agnello et al., FINUDA Collaboration, PRL 108 (2012)

Theoretical approach 2013/09/09EFB 2212 Hiyama E.Hiyama et al., NPA 908(2013)29. R.H.Dalitz et al., Nuovo Ciment 30(1963)489. Y. Akaishi et al., PRL 84(2000) E. Hiyama -4-body calculation of tnnΛ -R. H. Dalitz -ΛN interaction -Y. Akaishi -Coherent ΛNN interaction Dalitz Akaishi

J-PARC E10 Experiment Dec – Jan /09/0913EFB 22

Experimental Setup SDC3 SDC4 SFT AC LC TOF BFT BH2 SSD BC3 BC4 SDC2 BH1 GC π-π- K+K+ J-PARC K1.8 Beam Line 2013/09/0914EFB 22 K1.8 Beamline K1.8 Beamline 1.2GeV/c π - Beam 1.2GeV/c π - Beam Δp/p ~3.3x10 -4 Δp/p ~3.3x10 -4 Momentum is calculated by the Momentum is calculated by the Transfer Matrix Transfer Matrix BFT(x)-BC3,4(x,y,x’,y’) BFT(x)-BC3,4(x,y,x’,y’) SKS Spectrometer SKS Spectrometer Central Momentum 0.9GeV/c Central Momentum 0.9GeV/c Δp/p~1.0x10 -3 Δp/p~1.0x10 -3 Momentum is calculated Momentum is calculated by Runge-Kutta method by Runge-Kutta method SFT,SDC2(x,y,x’,y’)-SDC3,4(x,y,x’,y’) SFT,SDC2(x,y,x’,y’)-SDC3,4(x,y,x’,y’) Scattered Kaon identified TOFxLCxAC in Scattered Kaon identified TOFxLCxAC in online trigger online trigger SKS

Yield estimation in E10 proposal 15 ParametersValues Pion beam momentum Pion beam intensity Total number of pions (6 s acc. cycle) Target thickness ( 6 Li) DCX cross section (assumed) SKS acceptance Spectrometer efficiency (due to K decay) Analysis efficiency 1.2 GeV/c 10M/spill 3x10 12 pions 3.5 g/cm 2 10 nb/sr 100 msr 0.5 Estimated 6 Λ H yield in 3 weeks /09/09EFB 22

Run conditions of E10 Production run Production run -1.2GeV/c 6 Li(π -,K + ) 6 Λ H run -11.5days(10,12Mpions/spill) -1.2GeV/c 6 Li(π -,K + ) 6 Λ H run -11.5days(10,12Mpions/spill) Integrated pion beam reached to 1.65x10 12 pions Integrated pion beam reached to 1.65x10 12 pions Calibration run Calibration run -1.37GeV/c p(π -,K + )Σ - run - 4hours(10Mpions/spill) -1.37GeV/c p(π -,K + )Σ - run - 4hours(10Mpions/spill) +1.37GeV/c p(π +,K + )Σ + run - 1hour (3.5Mpions/spill) +1.37GeV/c p(π +,K + )Σ + run - 1hour (3.5Mpions/spill) +1.2GeV/c 12 C(π +,K + ) 12 Λ C run - 1day (3.5Mpions/spill) +1.2GeV/c 12 C(π +,K + ) 12 Λ C run - 1day (3.5Mpions/spill) Beam through run Beam through run +1.2,+1.0,+0.9,+0.8GeV/c (w/ and w/o target) +1.2,+1.0,+0.9,+0.8GeV/c (w/ and w/o target) 2013/09/0916EFB 22 reactionMomentumIntensity (pions/spill) time Production Run -> Total number of pions : 1.65x Li(π -,K + ) 6 Λ H1.2GeV/c x days Calibration Run – To confirm the performance of SKS system, and to calibrate the absolute missing mass value with two magnet polarity settings p(π -,K + )Σ GeV/c1.0x10 7 4hours p(π +,K + )Σ GeV/c3.5x10 6 1hours 12 C(π +,K + ) 12 Λ C+1.2GeV/c3.5x10 6 1day Beam Through Run – To measure the energy loss in the target and to see the consistency between beam line magnet and SKS +1.2,+1.0,+0.9, +0.8GeV/c 2hour

Particle ID 2013/09/0917EFB 22 πKP Mass Square accepted M 2 (t,p,L)=p 2 (1-β 2 )/β 2 = p 2 (c 2 t 2 /L 2 -1) t: flight time vertex to TOF p:scatterd particle momentum L: flight path vertex to TOF Mass square is calculated by time, momentum and path Selected Kaon Mass [0.2<m 2 <0.3]

Calibration Runs Results of analysis Results of analysis +1.20GeV/c 12 C(π +,K + ) 12 Λ C +1.20GeV/c 12 C(π +,K + ) 12 Λ C GeV/c p(π -,K + )Σ GeV/c p(π -,K + )Σ GeV/c p(π +,K + )Σ GeV/c p(π +,K + )Σ + Preliminary g.s.(s Λ ) 12 C(π +,K + ) 12 Λ C ΔB Λ :2.8MeV/c 2 (FWHM) Ex(p Λ ) p(π +,K + ) Σ + ΔM:2.6MeV/c 2 (FWHM) Preliminary Measure: MeV PDG: MeV Yield : ~2000 events Preliminary p(π -,K + ) Σ - ΔM:2.5MeV/c 2 (FWHM) Measure: MeV PDG: MeV Yield : ~6000events 2013/09/0918EFB 22 Yield (g.s): ~600events

Cross Section of 12 Λ C #1:-10.74MeV KEK-E369 : 12 C(π +,K + ) 12 Λ C at +1.05GeV/c #1+#2 -B Λ (GeV) #1 #2 Cross section and binding energy are roughly consistent with previous experiments (E369,E521) Our Data : 12 C(π +,K + ) 12 Λ C at +1.2GeV/c 2013/09/09EFB 2219

Preliminary Σ- continuum Λ- continuum Missing Mass 2013/09/09EFB 2220 t+2n+Λ 4 Λ H+2n = MeV t+2n+Λ = MeV 5H+Λ = MeV d+3n+Λ = MeV p+4n+Λ = MeV We could measure not only Λ-continuum region but also Σ-continuum region. Background level is about 0.5event/MeV, corresponding to 0.1nb/sr/MeV. FINUDA Preliminary

Summary KEK-PS E521 ( 10  Li) –  mixing probability ~ 0.5 % 6  H – J-PARC E10 experiment measured missing mass spectra from the bound region to Λ-continuum state and also Σ-continuum state. – Around the t+2n+Λ threshold, there is no peak structure with 10nb/sr. 2013/09/09EFB 2221 Production cross section of 6 Λ H may be smaller than what we expected (10nb/sr) or 6 Λ H may not exist.