Observation of Ξ hypernucleus, 12 Ξ Be, via the 12 C( K - , K + ) reaction at 1.8 GeV/ c S. Kanatsuki for the J-PARC E05 Collaboration NSMAT2016 2016/11/21 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 1
2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 1 Observation of Ξ hypernucleus, 12 Ξ Be, via the 12 C( K - , K + ) reaction at 1.8 GeV/ c • Introduction – BNL-E885 and KISO event • J-PARC E05 experiment – plan – pilot run in 2015 • analysis status • discussion • Summary
Introduction 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 2
BNL-E885 mass resolution 14 MeV (FWHM) (suggestion) Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki P. Khaustov et al., PRC 61 (2000) 054603 Bound region 2016/11/21 ‒ no clear peak dσ/dΩ ( -20 < E < 0 MeV) Ξ Be at 1.8 GeV/c 12 C( K - , K + ) 12 3 • • – θ<14°: 67 events, 42±5 nb/sr – θ<8°: 42 events, 89±14 nb/sr • ‒ shape analysis à V Ξ ～ -14 MeV ? ü evidence of existence of Ξ - bound state ü V Ξ ～ -14 MeV (B Ξ = ～4.5 MeV) ? ü V Ξ = -20 MeV is less favored
“KISO” event 2016/11/21 K. Nakazawa et al., PTEP (2015) 3, 033D02 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki reported in the 22th J-PARC PAC 4 • Ξ- 14 N system found in KEK-E373 – Ξ ー + 14 N → 10 Λ Be+ 5 Λ He – B Ξ = 1.03±0.18 or 3.87±0.21 MeV ±Γ/2 ü deeply bound state ü Ξ hypernuclei do exist ü stimulates systematic study
J-PARC E05 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 5
J-PARC E05 Collaboration Seoul National University J.K, Ahn, W. Jung, S. H. Kim E. Botta, A. Feliciello, S. Marcello JINR P. Evtoukhovitch, Z. Tsamalaidze, Osaka University, RCNP T. Gogami, K. Shirotori J.Y Lee, T. Moon K. Aoki, T. Takahashi, M. Ukai, T. O. Yamamoto Gifu University S. Kinbara Kitasato University T. Hasegawa 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 2015/11/19 J-PARC K1.8 counting room Korea University Torino University 6 K. Kobayashi, S.H. Hayakawa, T. Hayakawa, R. Honda, Y. Nakada, M. Nakagawa, A. Sakaguchi Kyoto University H. Ekawa, S. Kanatsuki, T. Nagae, T. Nanamura, M. Naruki Y. Akazawa, M. Fujita, K. Miwa, Y. Sasaki, H. Tamura JAEA S. Hasegawa, K. Hosomi, Y. Ichikawa, K. Imai, H. Sako, S. Sato, H. Sugimura, K. Tanida Tohoku University Osaka University KEK • – • – • – • – • – • – • – • – • – • – • – • –
J-PARC E05 experiment magnet construction completed in 2015 High-resolution run with S-2S dΩ 60 msr dp/p～6×10 -4 [S-2S spectrometer] at K1.8BL already working dp/p<1×10 -3 [Beam spectrometer] Missing-mass spectroscopy of Ξ- Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 2016/11/21 to be installed in 2018?? 7 observe peaks of the bound state hypernucleus via the 12 C( K - , K + ) 12 deduce the information of ΞN potential with new K + spectrometer, “S-2S” developed for KK reaction spectroscopy High-resolution measurement Ξ Be much improved mass resolution: ＜2 MeV D1 Scat. K + � • ~1.4 GeV/c • WC WC AC SDC3,4 TOF Tracker3,4 AC • Q2 TOF D1 Q2 Q1 Q1 1 m SDC1 Tracker1,2 BAC SDC1,2 BH2 Target • Target BC4 BC3 • Q13 Target • Q12 • 0 3 m Beam K −� 1.8 GeV/c D4 Q11 BH1 Q10 BFT MS2 Q9
dΩ 60 msr beam: 6×10 5 K - /spill, K/π ~0.8 (39kW) High-resolution measurement with new K + spectrometer, “S-2S” developed for KK reaction spectroscopy to be installed in 2018?? Pilot measurement: 2015 autumn at K1.8BL already working much improved mass resolution: ＜2 MeV by using the SKS spectrometer dp/p<1×10 -3 purpose [Beam spectrometer] resolution in wide range 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki deduce the information of ΞN potential magnet construction completed in 2015 observe peaks of the bound state dp/p～3×10 -3 Ξ Be hypernucleus via the 12 C( K - , K + ) 12 Missing-mass spectroscopy of Ξ- J-PARC E05 experiment dp/p～6×10 -4 [S-2S spectrometer] 7 Pilot run in 2015 Oct. 26 ‒ Nov. 19 dΩ 110 msr [SKS spectrometer] LC AC TOF SDC4 SDC3 Scat. K + � • SKS ~1.4 GeV/c • • SDC2 SDC1 SDC1 BAC BAC BH2 BH2 • Target Target BC4 BC4 BC3 BC3 • Q13 Q13 Target: CH 2 9.54g/cm 2 � • Q12 Q12 Carbon 9.36g/cm 2 • 0 0 3 m 3 m Beam K −� 1.8 GeV/c D4 D4 • • Q11 Q11 BH1 BH1 • Q10 Q10 BFT BFT – optimization of beam momentum MS2 – hypernuclear spectrum with medium Q9
Analysis 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 8
9 ( K - , K + ) selection Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki π ＋ p π ー 2016/11/21 LC AC TOF SDC4 SDC3 Mass square SKS Mass square SKS SKS w/ dY cut K ＋ 3 10 SDC2 SKS 2 10 SDC1 BAC Scat. K + BH2 10 Target BC4 BC3 1 Q13 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 K ー beam 2 Mass sqr. [GeV ] Q12 Beam TOF 0 3 m Beam K ー D4 Spectrometer Q11 BH1 Q10 BFT
arbitrarily to fit the past data. Ξ - production Present data are normalized 10 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 2016/11/21 working well • Missing mass - - + + Missing mass p(K Missing mass p(K , K , K ) at 1.8 GeV/c ) at 1.8 GeV/c Counts /0.5 MeV 60 b/sr) 500 Present data µ J.P.Berge et al. (1966) 50 ( ° 400 G.Burgen et al. (1968) <18 � 40 P.M.Dauber et al. (1969) > � Eyeball fit (C.B.Dover et al.) 300 /d 30 � <d θ lab ＜ 18° 200 � 20 100 10 0 0 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 1.3 1.3051.311.3151.321.3251.331.3351.341.3451.35 lab p (GeV/c) Missing Mass (GeV) - K ü detectors and analysis ü energy calibration ü ΔM ~5.4 MeV
region 11 Bound Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 2016/11/21 Energy spectrum - - 12 12 + + Binding energy Binding energy C(K C(K , K , K ) (Carbon) ) (Carbon) (Counts /2 MeV) 700 600 Δ M ～ 6 MeV FWHM (estimated) 500 QF- Ξ : 60k events θ < 30 deg 400 300 200 100 0 50 0 50 100 150 200 250 300 350 400 � -B.E. (MeV) B.E. = M( 11 B) + M( Ξ − ) − M( 12 Ξ Be)
region Energy spectrum Bound 11 region Bound 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki - - 12 12 + + Binding energy Binding energy C(K C(K , K , K ) (Carbon) ) (Carbon) (Counts /2 MeV) 700 - - 12 12 + + Binding energy Binding energy C(K C(K , K , K ) (Carbon) ) (Carbon) 600 Δ M ～ 7 MeV FWHM (estimated) (Counts /2 MeV) 220 500 QF- Ξ : 60k events 200 θ < 30 deg 180 400 160 300 140 120 200 100 100 80 60 0 40 50 0 50 100 150 200 250 300 350 400 � -B.E. (MeV) 20 0 B.E. = M( 11 B) + M( Ξ − ) − M( 12 Ξ Be) 80 60 40 20 0 20 40 � � � � -B.E. (MeV)
ΛΛ Be 12 12 Background level 1.1 Counts/bin (average in -180 ～ -80 [MeV]) Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 2016/11/21 Background - - 12 12 + + Binding energy Binding energy C(K C(K , K , K ) (Carbon + CH2) ) (Carbon + CH2) Counts /2 MeV 22 Background level : 1.08 Counts /2 MeV 20 #Event (20>B.E.> 0 MeV) : 55 Counts 18 16 14 12 10 8 6 4 2 0 180 160 140 120 100 80 60 40 20 0 20 � � � � � � � � � -B.E. [MeV]
13 Bound region 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki Energy spectrum Background level 1.1 Counts/bin (average in -180 ～ -80 [MeV]) in 20＞-E＞0 MeV, 39 events - - 12 12 + + Binding energy Binding energy C(K C(K , K , K ) (Carbon + CH2) ) (Carbon + CH2) Counts /2 MeV 22 20 18 16 ü significant excess 14 12 10 8 6 4 2 0 80 70 60 50 40 30 20 10 0 10 20 � � � � � � � � -B.E. [MeV]
Comparison with BNL-E885 2016/11/21 14 (θ＜14° ) Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki Comparizon of BNL and J-PARC Comparizon of BNL and J-PARC Counts [/2 MeV] 35 BNL E885 (x0.58) 30 J-PARC E05 25 20 15 10 5 0 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 -B.E. [MeV] ü spectrum shapes are consistent
Summary 2016/11/21 Neutron Star Matter (NSMAT2016) Tohoku Univ. / S. Kanatsuki 15 • Ξ-hypernucleus – exists, but binding energy is not determined yet – baryon-baryon interaction and strange nuclear matter • J-PARC E05 pilot measurement – first experiment on S=-2 physics at J-PARC – analysis status • significant excess in the bound region • suggestion – two bound states – deeper potential depth >14 MeV (suggested in BNL-E885) – prospect • cross section estimation • angular distribution of elementary/QF process
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