A deeply bound Ξ 14 N system detected in nuclear emulsion

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1 A deely bound Ξ 14 N system detected in nuclear emulsion Kazuma Nakazawa for the E07 () collaboration Phys. Det., Gifu Univ., JAPAN 30 th Nov., 1 / 15 Outline 1. Ξ-N interaction 2. Overall scanning method 3. The KISO event showing a deely-bound Ξ-N system 4. Summary

2 1.Ξ-N interaction Study of hadron-hadron interaction, In S=-2 sector, YY-mixing [ ΞN ΣΣ( H)] m(ξn) m() = (23~28) MeV <= m(σn) m(n) = 80 MeV Uniquely available source of information; H-dibaryon, double- hyernucleus, Ξ hyernucleus Baryon octet ΞN interaction, can be studied a Ξ-nucleus otential via Ξ hyernucleus and Ξ atoms However non conclusive measurement has been made, so far. 2 / BNL, KEK Any eak structures for Ξ-nuclear state were not observed. Attractive otential on 1 Ξ 2 Be was suggested to be 14 MeV. Two events (E176) 3D atomic or nuclear bound state? one event (E373) consistent with the Ξ - cature in 3D (coming soon) E03 & E07 X-ray measurement from Ξ atoms. E05 High reso. sectr. of Ξ hyernuclei. For the emulsion exeriment, it has been a key oint to develo fully automated and fast scanning system.

2. Develoment of OS CPU Overall-scanning Primary motivation; fast detection of α decay vertices of natural isotoes to calibrate range-energy relation.

3 2. Develoment of OS CPU Overall-scanning Primary motivation; fast detection of α decay vertices of natural isotoes to calibrate range-energy relation. 1 fast image cature Develoed system with CCD camera :Win2000 s4 :3.0 GHz 1.57GB RAM Camera :100Hz (CCD) Obj. lens:x 50 emulsion: 500μm area :0.1x0.08mm 2 # of image:~100/cycle Time :3sec/cycle [~ hard limit] 3 / 15

4 2. Develoment of Overall-scanning 2 fast image rocessing for event detection Until Aril. 2013, 8 M images by test oeration (1.46 cm 3 ) using E373 emulsion (55 liters) α decay VTX 4 / 15 Double- 3 vertices 2 vertices (single- cand.) NAGARA event was detected by this method

5 3. A new event by the, named 5 / 15 Emitted back-to-back direction Toology seems to be consistent with the ast events of twin hyernuclei (E176). Results of KEK-E176:S.Aoki et al., NP. A828 (2009)

A new event by the, named 6 / 15 E176 results; S.Aoki et al., NP.

robable] Coulomb assisted nuclear bound state. ==> VΞ- = 18 MeV Y.

7 MeV) for nuclear state Y. Akaishi, Nucl. Phys.

6 A new event by the, named 6 / 15 E176 results; S.Aoki et al., NP. A828 (2009) Ξ binding energy (MeV) in nucleus : 12 C [most robable] Coulomb assisted nuclear bound state. ==> VΞ- = 18 MeV Y. Yamamoto, Few-Body Syst. Sul. 9 (1995) 145 BΞ- = 3.75 MeV (Γ = 2.7 MeV) for nuclear state Y. Akaishi, Nucl. Phys. A 547 (1992) 217c BΞ (3D) = 0.13 MeV for 12 C not inconsistent!! (= 0.17 MeV for 14 N)

Range-Energy relation was calibrated in good accuracy Proton for Std. emulsion (Ilford G5 : 0 = 3.815 g/cm 3 ); ref.[1] W.H.Barkas, N.C. VIII (1958).

7 Range-Energy relation was calibrated in good accuracy Proton for Std. emulsion (Ilford G5 : 0 = g/cm 3 ); ref.[1] W.H.Barkas, N.C. VIII (1958) data fitted by olynomial exression under the Bethe-Bloch formula. Calc. Our 7 th order olynomial fitting to the ref.[1] Density of our emulsion; = / g/cm 3 by measurement of α rays with monochromatic K.E. from 212 Po and 228 Th. Consistent with = / g/cm 3 by measurement of its size and weight at the E373 beam exosure. 7 / 15 The density error of g/cm 3 gives rise inaccuracies, ΔR / R : 1.1% ΔE / E : 0.7% for roton to 12 C with their energy less than several tens MeV

Outline of the event 8 / 15 1) Ξ- hyeron can be roduced in the target (8 mm from to the Em.) 2) Auger electron make the cature oint clear. 3) MIPS track from the decay oint D.

8) Hummer track : 8 He, 8 Li or 8 B 8 Be*(2 + ). Vertices A & B B #4 A track range (µm) theta (deg.) hi (deg.) comments #1 8.0 ± 0.3 133.0 ± 3.0 13.2 ± 3.2 Single-hyernucleus #2 69.1 ± 0.5 40.4 ± 0.

8 Outline of the event 8 / 15 1) Ξ- hyeron can be roduced in the target (8 mm from to the Em.) 2) Auger electron make the cature oint clear. 3) MIPS track from the decay oint D. E373 setu 4) TK #4 went out of the emulsion stack. 5) Consistent with Ξ- cature reaction occurred on C, N or O. 6) The charge of #2 should be 2 or more. 7) The charge of #1 should be 5. 8) Hummer track : 8 He, 8 Li or 8 B 8 Be*(2 + ). Vertices A & B B #4 A track range (µm) theta (deg.) hi (deg.) comments #1 8.0 ± ± ± 3.2 Single-hyernucleus # ± ± ± ± 0.3 µm : B ~ C # ± ± ± 1.6 #4 > ± ± 1.3 Out of the emulsion stack #5 6.7 ± ± ± 4.3 α from 8 Be #6 5.8 ± ± ± 4.7 α from 8 Be # ± ± ± 1.5 # ± ± ± 1.3 #4

Vertex D Analysis of the event 9 / 15 0 5 10 (μm) Vertex B 0 5 10 (μm) B D #4 Mass of 8 Be

ossibility (#4) is nothing in comarison with Energy-loss (Grain density ~ x1.41[+/- 0.

9 Vertex D Analysis of the event 9 / (μm) Vertex B (μm) B D #4 Mass of 8 Be (2 + ) (MeV/c 2 ) Reconstructed mass (MeV/c 2 ) (a) ± (b) (Γ = 1.5 MeV) ± α at VTX. D Using measured data Under the momentum balance Possibility of mesonic decay of #1 π- ossibility (#4) is nothing in comarison with Energy-loss (Grain density ~ x1.41[+/- 0.08]) of π- in the NAGARA event. K.E. of #4 (34.8MeV, if it s a roton ) was too large to understand the decay mode with a π 0 meson at the decay oint of #1. at VTX. B

10 Vertex B n B #4 Possibility of 8 He or 8 B for TK #3 Vertex B Possible rocess at VTX. B The case of 8 B : denied under charge conservation Total A 17, total Z 7 (even for Ξ + 16 O) TK #2 must be non-mesonic Z( 2) TK #1 (Z 5) if TK #4 Z=1, TK #3(Z 4) 8 B 10 / 15 The case of 8 He : denied momentum imbalance at VTX.A Assuming 8 He (#3) / or d (#4) Li (#1), only the rocess is considered; Ξ O => 1 0 Li (#1) + 7 Be(#2), 1 0 Li => 8 He (#3) + (#4) + n Momentum imbalance ( / MeV/c) at oint A = Consistent with an association of a MIPS from VTX. D. Mc : Mass of a core nucleus + M() Mr : reconstructed minimum mass Mc Mr : B max. should be lus value. B #4 There is no bound hyerfragment for track #2

11 Vertex A Possible rocess at VTX. A 11 / 15 A Ξ + 14 N 1 0 Be + 5 He

12 Vertex A Possiblities of in-flight decay of hyernuclei (#1 and/or #2) n A B Ξ = M(Ξ + 14 N) E( 1 0 Be) E( 5 He) ΔK.E.( 1 0 Be + 5 He) Assuming B Ξ = 0.00 MeV, ΔK.E. = 4.43 MeV. Decay rates R were estimated : R ( 1 0 Be) = 0.6%, R ( 5 He) = 2.9% Thus, it is very unlikely for decays in flight on both nuclei. It is also unlikely for in-flight decay for one of them due to well balance of momenta. 1 0 Be and 5 He decayed after stoing. Ξ + 14 N 1 0 Be + 5 He, 1 0 Be 8 Li + + n, 8 Li 2α + e - (+ ν e ) ex. 5 He (#7) + d(#8) + 2n B Ξ = / MeV (by Mom. balance [#1 and #2]) Measurement error : 0.09 MeV Mass ( 1 0 Be, 5 He, Ξ ) error : 0.23 MeV 12 / 15

13 Energy (MeV) 5 10 B Ξ = / MeV (by Mom. balance for 1 0 Be and 5 He) Theoretical redictions 0 the event Ξ + 14 N 1 0 Be + 5 He uniquely identified!! 3.27 (1 + ) 3.07 (0 + ) 2.41 ( (22) 0.08 (21 - ) (4 - ) (3 - ) (1 - ) (0 - ) (3 - ) (2 - ) (2 - ) B = (ex.) B Ξ = 0 9 Be Be g.s. BΞ (MeV) 3.7σ err far from 3D level H&Y DJM 1.11± ±0.25 Err.(meas.)=±0.09 Err.(mass)=±0.23 Ξ 14 N system The first evidence of a Ξ -14 N system to be bound deely. submitted to PTEP 1.14 Yamaguchi, Yamamoto & Ueda PTP. 105 (2001) / 15 (σ err ~ 0.25 MeV) 3D 2 The aer well resented that the ast two event to be occurred in 2 nuclear bound state. 1s

14 14 / Summary 1. We have erformed exeriments to study S=-2 systems with the nuclear emulsion at KEK, however any conclusive information has not been obtained, so far. 2. To get reliable information about S=-2 systems, we are develoing fully automated and fast scanning system, Overall scanning for the emulsion. 3. During test oeration of the system, a clear evidence of a deely bound Ξ- 14 N system, Ξ + 14 N 1 0 Be + 5 He, has been detected and uniquely identified in the emulsion of 1.46 cm 3 volume among 55 liters. 4. The detected event, named KISO, resents a deely bound Ξ- 14 N system with Ξ binding energy of / MeV, which is no longer the atomic 3D state (0.17 MeV for Ξ- atom on 14 N). Even if the 1 0 Be nucleus was roduced in excited state, Ξ binding energy is far from 3D atomic state by more than 3.7 standard deviations. 5. It was understood that ΞN interaction will be attractive!! To understand A-deendence of int. and ΞN interaction more in detail, we will continue develoment of overall scanning method to be alied in the E07 exeriment, of which beam exosure can be carried out in Early 2016 (?).

15 New scanning system for the E07emulsion Present system 130 μm 110 μm with iezo stage Present New Obj. Lens 50 (NA. 0.9) 20 (NA. 0.35) Camera 100Hz XC_HR Hz HXC20 Pixel ixel ixel Area 130 mm 110 mm 1140 mm 200 mm Rate(Hz) μm 300 faster!! 5 sets 2 sets 15 / μm Images of all of the emulsion lates can be obtained in a few years.

Study of double-λ hypernuclei

Study of double-λ hypernuclei Study of double- hyernuclei Our goal Phys. Det., Gifu Univ. K.Nakazawa Status of exeriments Exeriment at J-PARC Summary---statistics Exerimental motivation Making a nuclear chart of double-hyernuclei =>