Status of K - pp search Tomofumi NAGAE experiments Kyoto - PowerPoint PPT Presentation

The 9th China-Japan Sympo. (JCNP2015), Nov.7-12, 2015 Status of K - pp search Tomofumi NAGAE experiments Kyoto University

Contents ❖ Introduction to “K - pp” ❖ Recent measurements ❖ LEPS/SPring-8 ❖ HADES ❖ J-PARC E15/ fwd “n” ❖ J-PARC E27 ❖ Discussion ❖ Summary

K - pp ❖ KN : attraction in Isospin=0 ❖ Kaonic hydrogen X-ray ; SIDDHARTA 
 M. Bazzi et al., NPA 881 (2012) 88-97. ❖ Low-energy scattering measurements + Branching ratios at threshold - p threshold ❖ Λ (1405) below the K π =1/2 - ; Moriya et al., Phys. Rev. Lett. 112 (2014) 082004. ❖ J ❖ Antikaon-Nucleon Molecule from Lattice QCD 
 ; J.M.M. Hall et al., Phys. Rev. Lett. 114 (2015) 132002. - pp” : Y=1, I=1/2, J π =0 - ❖ Possible existence of “ K

Past Experiments on K - pp ❖ First evidence of K - pp with 6 Li+ 7 Li+ 12 C 
 M. Agnello et al., PRL94, (2005) 212303 by FINUDA - B [MeV] - K pp -250 -250 -200 -200 -150 -150 -100 -100 -50 -50 0 0 30 -150 -100 -50 B=115+6/-5+3/-4 MeV 0 arbitrary unit 25 Γ = 67+14/-11+2/-3 MeV ) 2 counts/(10MeV/ c 20 15 2.2 2.25 2.3 2.35 2.4 10 5 0 2.1 2.1 2.15 2.15 2.2 2.2 2.25 2.25 2.3 2.3 2.35 2.35 2.4 2.4 2.45 2.45 2.5 2.5 2 p- invariant mass [GeV/ c ] Λ - B (K pp) [MeV] 200 100 0 (a) large-angle proton: high- P (p) ❖ DISTO data: p+p → K - pp (p Λ )+ K + at 2.85 GeV T 2.5 M = 2267 (2) M (K+p+p) = 2370 Deviation UNC/SIM (arb. scale) ❖ M=2267±3±5 MeV/c 2 2.0 1.5 ❖ Γ = 118±8±10 MeV Γ = 118 (8) 1.0 M ( Σ + π +p) = 2267 M ( Λ *+p) = 2345 0.5 T. Yamazaki et al., PRL 104 (2010) 132502. P . Kienle et al., Eur. Phys. J. A 48 (2012) 183. 0 2150 2200 2250 2300 2350 2400 2450 2 Missing Mass ∆ M (K) [MeV/ c ]

Theoretical calculations on K - pp ❖ Methods : Variational vs. Faddeev 
 → Almost same results by using the same interaction model ❖ KN Interaction Models : 
 Chiral SU(3)-based (Energy dependent) → Shallow~20 MeV 
 Phenomenological (Energy independent) → Deep~40-70 MeV Maeda, Dote,Hyodo, Akaishi, Barnea, Gal, Ikeda, Schevchenko Revai, Ikeda, Sato Akaishi, Weise Yamazaki Liverts Kamano,Sato ,Gal, Mares Schevchenko Yamazaki B (MeV) 17-23 48 16 60-95 9-16 50-70 32 51.5 Γ (MeV) 40-70 61 41 45-80 34-46 90-110 49 61 Faddeev- Faddeev- Faddeev- Faddeev- Faddeev- Method Variational Variational Variational AGS AGS AGS AGS Yakubovsky Interaction Chiral Phenom. Chiral Chiral Chiral Phenom. Chiral Phenom. s FSI effects ? (V.K. Magas et al.), Λ *N bound state (T. Uchino et al.)

Comparison between Theory and Exps. ❖ Binding energy ❖ Shallow case: B~20 MeV ❖ Deep case: B~40-70 MeV ❖ Observations: B>100 MeV ❖ Width ❖ agreement: Γ ~30-100 MeV By Y. Ichikawa

Recent measurements ❖ LEPS/SPring-8 A.O. Tokiyasu et al., Phys. Lett. B 728 (2014) 616-621. ❖ d( γ , K + π - ) reaction (E γ =1.5-2.4 GeV) ❖ Inclusive missing-mass 
 σ m ~10 MeV ❖ Background 
 K + Λ (1520), K + π - π Y ❖ Upper limits:2.22-2.36 GeV/c 2 
 < 1.1-2.9 μ b for Γ =100 MeV, 
 9.9-26% of K π Y productions

⇅ 
 ❖ HADES G. Agakishiev et al., Phys. Lett. B 742 (2015) 242-248. ❖ p+p → K + p Λ @3.5 GeV ❖ Bonn-Gatchina Partial Wave Analysis 
 Λ p pK + well reproduces the data ❖ K - pp production upper 
 limit ~4 μ b for Γ =70 MeV 
 (2.22-2.37 GeV/c 2 ) 
 Λ (1405) production ~10 μ b

Binding Energy [GeV] 0.3 0.2 0.1 0 2 10 × ❖ J-PARC E15 160 30 M(K+p+p) Data 140 CDS 2 25 Co u nts/10 MeV/c BG )) 120 -decay Σ A 2 BG b /sr/(MeV/c 20 × ne u tral 100 T. Hashimoto et al., PTEP (2015) 061D01. BG /dM cell 80 BG 15 accidental Ω 3 He(K - ,n) reaction @ 1 GeV/c 60 /d ❖ 10 σ 40 µ 2 d ( 5 20 0 0 ❖ Semi-inclusive missing-mass 
 All - - K n → K n Ar b itrary u nit - 0 K p → K n s σ m :5-15 MeV - K N → Λ π ( π )( π ) - K N → Σ π ( π )( π ) * - K N → Y π ,NK π ( π ), ∆ K ❖ K - pp production upper limit 
 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 – 3 2 He( K , n ) X missing mass (GeV/c ) 100-270 μ b/sr for Γ =100 MeV 
 Binding Energy [GeV] 0.3 0.2 0.1 0 20 350 (~5% of QF K - n elastic) 18 )) 16 2 300 b /sr/(MeV/c (1405)+p) ) ) 14 π π +N+ +N+ +N) +p) 250 2 2.06-2.29 GeV/ c 2 Co u nts/10 MeV/c Λ Λ Λ Σ Σ 12 M( M( M( M( M( µ ( 200 CDS 10 A 8 × 150 /dM Data 6 BG Ω Σ -decay 100 /d BG ne u tral σ 4 2 BG d cell BG 50 accidental 2 0 0 2 2.05 2.1 2.15 2.2 2.25 2.3 2.35 – 3 2 He( K , n ) X missing mass (GeV/c )

Lessons ❖ It looks hard to observe the K - pp signal in inclusive measurements. (LEPS, J-PARC E15 fwd “n”) ❖ Small and Broad signature ; ~1 
 two-step reaction (two nucleons be involved) ❖ Large and Widely distributed QF background ; >10~100 
 single-step reaction

J-PARC E27 Y. Ichikawa et al., PTEP (2014) 101D03. ❖ d( π + , K + ) reaction @1.69 GeV/ c Y. Ichikawa et al., PTEP (2015) 021D01. Missing mass Yamazaki & Akaishi, Phys. Rev. C 76 (2007) 045201.

Experimental Setup SKS ❖ K1.8 beam line spectrometer BVH 2 SDC3 K + C 1 D C SDC4 t S D e TOF S g r ❖ 1.69 GeV/c π + a 2 H T 4 LC B C 3 C B B ❖ ∆ p/p~2x10 -3 Q13 Q12 A π + C ❖ SKS spectrometer R LAC D4 ❖ 0.8-1.3 GeV/c K + ❖ ∆ p/p~2x10 -3 0 3 m ❖ ∆Ω ~100 msr Q11 Q10 K1.8 Beam line BC2 ❖ Target : liquid deuterium(1.99 g/cm 2 ) BC1 BH1 GC

Expected Inclusive Spectrum d( π + , K + ) 2 2 d d /d /d /dM /dM σ σ Ω Ω o o o o 2 2 -16 -16 (Lab) (Lab) b/sr/2MeV] 12 QF Σ Old Bubble Chamber Data 
 10 + µ deuteron Fermi motion [ (Lab) QF Λ 8 o -16 Σ + o 2 Ω 6 /d σ d K-pp 4 Λ QFY*+ π YN Σ 0 Σ * Λ * 2 0 2.05 2.1 2.15 2.2 2.25 2.3 2.35 2.4 2.45 2.5 2 Missing Mass[GeV/c ]

p( π + ,K + ) Σ + / Σ * @1.69 GeV/ c Σ + ❖ Σ + and Σ + (1385) : 
 mass & width are consistent 
 with PDG Σ(1385) + ❖ ∆ m FWHM =2.8±0.1 MeV/ c 2 800 7 Σ + )] data present data 2 b/sr/(4MeV/c 700 total 6 + + + p (1385) K 600 � � � old data 5 b/sr] + + p K � � � � 500 + µ + 4 p K µ � � � � [ [ Lab 400 (Lab) � 3 o -16 /d 300 o � 2 /dM d 2 200 � /d 1 100 � 2 d 0 0 2 4 6 8 10 12 14 16 1.25 1.3 1.35 1.4 1.45 Scattering Angle [deg] � 2 Missing Mass [GeV/c ] Lab

Measured d( π + ,K + )X spectrum (a) Σ N- Λ N Cusp @2.13 GeV Mass shift for Y* by ~30 MeV K-pp

Range counter for Proton tagging ❖ Range Counter Arrays (RCA) ❖ 5 layers(1+2+2+5+2 cm) of Plastic scinti. ❖ 39-122 deg. (L+R) ❖ 50 cm TOF → β p (a) ( b ) 22 p K + (SKS) 2.5 20 18 16 2 14 p b 12 1/ 1.5 10 8 6 1 4 2 0.5 0 0 100 200 300 400 500 600 700 p + ( K 1.8) 0 50 cm PID

Proton Tagging Simulation ❖ Background: QF Y/Y* productions → Forward protons ❖ Signal: K - pp decays → protons in RCA

Coincidence Study Inclusive ❖ Proton mom. >250 MeV/c ❖ QF Λ , QF Σ , QFY*s are 
 suppressed as expected !! ❖ What’s left ? Proton Coincidence

One-proton coincidence ❖ Coincidence Probability(MM) 
 = One-proton coincidence(MM)/Inclusive(MM) ❖ Enhancement near 
 the Σ N threshold 
 (2.13 GeV/c 2 ) ❖ Broad bump at 
 ~2.28 GeV/c 2

20 Two-proton coin. & Decay mode ① ② ③ ❖ Two-protons in the final state : K - pp → Λ p, Σ 0 p, Y π p 
 pp π , pp πγ , pp ππ ( γ ) ❖ d( π + ,K + pp)X ＋ Data ① ② ③ Σ 0 p Λp ー X = π (FS: Λp) ー X = πγ (FS: Σ 0 p) Λp Σ 0 p Yπp ー X = 2π(γ) (FS: Yπp) Λp Yπp ー Sum Σ 0 p Kinematically almost-complete measurement !

Mass-acceptance for each decay mode Λp � Σ 0 p � Yπp �

K - pp -like Structure ❖ Mass : 2275 +17 − 18 (stat . ) +21 − 30 (syst . ) MeV /c 2 Relativistic Breit-Wigner ❖ Width : 162 +87 − 45 (stat . ) +66 − 78 (syst . ) MeV ❖ Binding Energy − 78 of 95 + 18 − 17 (stat.) + 30 − 21 (syst.) MeV 0 Σ 0 p mode

Λ p/ Σ 0 p Branching Fraction Σ N cusp + 
 Σ N → Λ N conversion Preliminary Γ Λ p d σ = 0 . 92 +0 . 16 − 0 . 14 ( stat ) +0 . 60 − 0 . 42 ( syst ) d Ω K − pp → Σ 0 p = 3 . 0 ± 0 . 3(stat) +0 . 7 − 1 . 1 (syst) µ b / sr Γ Σ 0 p d Ω K − pp → Λ p/ Σ 0 p / d σ d σ d σ d Ω Λ (1405) ≈ (7 / 8)% d Ω Λ (1405) = 36 . 9 µ b / sr

Remarks ❖ Λ (1405) production seems to be necessary, ❖ (OK for DISTO, HADES, J-PARC E27; △ for FINUDA, ? for E15) ❖ but, not enough ! ❖ Need to understand the Λ *(E)p → K - pp dynamics ❖ → sensitivity of the measurements 
 7% of Λ (1405) in E27 ⇔ < 40% in HADES

Discussion on “ K - pp ” ❖ Binding Energy is large (~100 MeV), and the width is broad. ❖ Not inconsistent with 
 250 FINUDA, DISTO 200 [MeV] This data 150 ❖ Theoretical calcs. are 
 DISTO pp N.V.Shevchenko, A.Gal, J.Mares 100 difficult to reproduce 
 - K Γ A. Dote, T.Hyodo, W.Weise Y.Ikeda, T.Sato T.Yamazaki, Y.Akaishi the large binding. 50 FINUDA N.Barnea, A.Gal, E.Z.Liverts OBELIX S.Wycech, A.M.Green Y.Ikeda, H.Kamano, T.Sato 0 0 20 40 60 80 100 120 140 B [MeV] - K pp