J-PARC E07 Ξ - Junya Yoshida (Advanced Science Research Center, JAEA) On behalf of J-PARC E07 Collaboration K + K - X -

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1 J-PARC E07 Systematic study of double strangeness nuclei with Hybrid emulsion method LL hypernucleus K - 1.8GeV/c Target SSD X - K + nλ p p Λ n X hypernucleus n p p Ξ - n Ge detector X-ray X-ray from X - atom Ξ - Ag or Br Emulsion Sheets Junya Yoshida (Advanced Science Research Center, JAEA) On behalf of J-PARC E07 Collaboration 1

2 Concept: More than 10 times statistics of KEK-PS E373, 10k X - stop events KEK-PS E373 Emulsion gel 0.8 tons 2.1 tons Purity of K- beam 25% ~85% X - stop yield ~650 10k LL hypernuclei 7 ~10 2 J-PARC E07 (in proposal) about 15 times of E373 Physics motivations Subjects: double strangeness system s-shell LL hypernuclei: ΛΛ4 H, ΛΛ5 He, and ΛΛ5 H spectroscopy of LL hypernuclei (A = 6 ~17) X hypernuclei ( 13 X B, 15 X C, and 17 X N) X-ray from X-atoms (X - +Ag, or X - +Br) LL hypernuclei in excited state Physics: baryon-baryon interaction LL S-wave interaction LL P-wave interaction XN interaction LL-XN coupling Production, structure, and decay of double strangeness system 2

3 Experimental apparatus of E07 J-PARC Hadron hall K1.8 beamline TOF wall Diamond target Ge detector array (Hyperball-X) SSD KURAMA Magnet - Emulsion module Emulsion mover 3

4 Beam exposure May-Jun KURAMA Commissioning : 5.0 days Physics : 4.9 days 4/15-4/19, 2017 (44kW) Emulsion exposure : 50 h calibration : 19 h 5/25-6/29, 2017 ( kW) Emulsion exposure : 23.4 days calibration : 8.5 h Jul. 1 st 2017, Run end counting room Year Beam power [kw] K - intensity [/spill] K - purity Time [h/mod.] Integrated K - [/mod.] DAQ Eff k 81% G 83% k 83% G 84% k 82% G 89% k 270k 50% - 82% G 1.0G 89-92% 14 Emulsion modules Totally, 100G Kaons were exposed for 118 emulsion modules 4

5 Photographic processing: completed in Feb Beam Exposure Photographic proc. Analysis completed! 1 st physics run 18 modules 2 nd physics run 100 modules 5

6 mom[gev/c] X - selection from the (K-, K+) reaction by off-line analysis K - target X - SSD Emulsion sheets SSD2 K+ momentum Scattered particles for selection Vertex residual High de No hit Missing momentum vector vs X - track K + Charge*mass[GeV/c 2 ] Criteria for Xi track selection Criteria X - stop prediction/mod. 1 10k ~440 High S/N & stop ratio 2 2k ~850 Realistic selection 3 1k 6.2k All X - stop 4 negligible 16k All combination by simulation for 118 modules 1 st priority 6

7 Hunting X - stop event * Disassembling * Photographic developing volume for readout emulsion module ~(+-200mm) 2 0.4mm Thin-type ~(+-10mm) 2 ~440 predictions of X - tracks 1.0mm Thick-type p-bar tracks for SSD-emulsion alignment 1.0mm Thick-type Beam direction 7

8 Scanning machine for pl01, scanning time: 2~3hours Y Z X Tracks in X-Y space (1mm) 2 with SSD->pl01 protons Position accuracy: reasonable upper layer track s: 53mm s: 64mm Angular accuracy: reasonable lower layer s: 26mrad s: 23mrad 8

9 X- tracking in thick-type sheet M.K.Soe et al., NIM-A 848 (2017) Objective lens Emulsion sheet (thick-type) 500 micron emulsion layer tracking * Tracking with image processing 40 micron base 500 micron emulsion layer track image sensor stage Objective lens(x50) Optical microscope system Tracking software 9

10 Observation of endpoint Case1. X - ->Lp - decay Case2. no visible fragment Case3. with hyperfragment p - X - X - X - -> detail analysis Estimation by simulation 75% X - 25% p B.G. 29% stop in module 50% in-flight decay <- case1 21% through and decay captured by C, N, O Ag, Br H a few % of followed track with hyperfragment <- case3 with nuclear fragment <- case2 no visible fragment 10

11 So far, 30% of the total emulsion sheets has been scanned. Current statistics is more than twice comparable to E373 KEK-PS E373 E07 (current) X - stop with nuclear fragment Double + twin ? 8 double Lambda events 6 twin events + 2 more candidates? Found on Found on

12 MINO event 10mm Mod#069 pl07 ID : #4 LL#1 X - #3 n L np pl n #6 L#2 X - + X -> LL #1 + #3 + #4 LL#1 -> L #2+ #5 + #6 L#2 -> #7 + #8 + #9 #5 Found by Kasagi (Gifu Univ.) #8 #7 #9 Via our analysis, L#2 is L5 He The decay of LL #1 is non-mesonic decay (#6 is not p - ) The change of LL #1 is at least +4 LL #1 is LL Be and X is 16 O For all combination, conservation laws geometrical consistency kinematic consistency, etc. within 3s of measurement error Possible interpretations B ΛΛ -B Ξ- B ΛΛ -B Ξ- [MeV] X O -> 10 LL Be + 4 He + t ~15 ~1 X O -> 11 LL Be + 4 He + d ~19 ~2 X O -> 12 LL Be* + 4 He + p ~13+ E ex ~-3 + E ex This result will be submitted to PTEP in this week. LL 11 Be is most probable judging from the c 2 of the kinematic fit 12

13 IBUKI event Mod#047 pl10 ID : n Ξ- np p n #2( 5 L He) Found by A. N. L. Nyaw (Gifu Univ.) #9 #7 #8 (p - ) X - #1( L 10 Be) X N -> 15 X C X 15 C -> 10 L Be + L5 He L 5 He -> #7 + #8 + #9 L 10 Be -> #3 + #4 + #5 + #6 Via our analysis, (X O, 14 N or 12 C) -> 2 single L hypernuclei + neutrons Only L 10 Be + L5 He was accepted at the 1 st vertex #8 is p - The decay of #1 and #2 are consistent with that of L 10 Be and L5 He #4 #5 #3 #6 For all combination, conservation laws geometrical consistency kinematic consistency, etc. within 3s of measurement error Possible interpretation B Ξ- [MeV] X N -> X 15 C -> L 10 Be + L5 He ~1 To be submitted The same decay process to KISO event 13

14 First measurement of X-ray from X-atoms Ξ - V Ag or Br X-ray Ag(n=8, l=7) (n=7,l=6) Ξ - r Ge detector Hyperball-X Br(316 +? kev) ~10 counts Ag(370 +? kev) ~10 counts 511 kev Z(n,l) E (kev) Shift (kev) Width (kev) Ag(8,7) (7,6) Case Case Br(7,6) (6,5) Case Case Case 1: assuming potential shape to be the same as the nuclear density (tr potential ) Case 2: Nijmegen D model correcting to produce the potential depth of ~ 14 MeV. In current analysis, 900 σ stop event (15 % of total ) were observed in emulsion sheets. The detail will be introduced in M. Fujita s poster 14

15 summary J-PARC E07 is the most complex emulsion experiment so far to investigate double hypernuclei with Hybrid emulsion method. Beam exposure and photographic processing has been completed successfully. Event hunting is ongoing. Current statistics of E07 is more than twice that of E events of 3-vertex topology are found, so far. Several events are identified. These events will be published in the near future. We will continue the event hunting. Main search work will finished in about 1 year. 15