Status of K - pp search experiments

Transcription

1 The 9th China-Japan Sympo. (JCNP15), Nov.7-1, 15 Status of K - pp search experiments Tomofumi NAGAE Kyoto University

2 Contents Introduction to K - pp Recent measurements LEPS/SPring-8 HADES J-PARC E15/ fwd n J-PARC E7 Discussion Summary

3 K - pp KN : attraction in Isospin= Kaonic hydrogen X-ray ; SIDDHARTA M. Bazzi et al., NPA 881 (1) Low-energy scattering measurements + Branching ratios at threshold Λ(145) below the K - p threshold J " =1/ - ; Moriya et al., Phys. Rev. Lett. 11 (14) 84. Antikaon-Nucleon Molecule from Lattice QCD ; J.M.M. Hall et al., Phys. Rev. Lett. 114 (15) 13. Possible existence of K - pp : Y=1, I=1/, J " = -

4 Past Experiments on K - pp First evidence of K - pp with 6 Li+ 7 Li+ 1 C by FINUDA B=115+6/-5+3/-4 MeV Γ= 67+14/-11+/-3 MeV ) counts/(1mev/c M. Agnello et al., PRL94, (5) 133 -B K [MeV] - pp arbitrary unit DISTO data: p+p K - pp (pλ)+ K + at.85 GeV M=67±3±5 MeV/c Γ= 118±8±1 MeV p-λ invariant mass [GeV/c ] T. Yamazaki et al., PRL 14 (1) 135. P. Kienle et al., Eur. Phys. J. A 48 (1) 183. Deviation UNC/SIM (arb. scale) (a) large-angle proton: high-p T(p) M = 67 () - B (K pp) [MeV] Γ = 118 (8) M(Σ+π+p) = 67 M(Λ*+p) = 345 M(K+p+p) = Missing Mass M(K) [MeV/c ] (b) small-angle proton: low-p (p)

5 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~ MeV Phenomenological (Energy independent) Deep~4-7 MeV Dote,Hyodo, Weise Akaishi, Yamazaki Barnea, Gal, Liverts Ikeda, Sato Ikeda, Kamano,Sato Schevchenko,Gal, Mares Revai, Schevchenko Maeda, Akaishi, Yamazaki B (MeV) Γ(MeV) Method Variational Variational Variational Faddeev- AGS Faddeev- AGS Faddeev- AGS Faddeev- AGS Faddeev- Yakubovsky Interaction s Chiral Phenom. Chiral Chiral Chiral Phenom. Chiral Phenom. FSI effects? (V.K. Magas et al.), Λ*N bound state (T. Uchino et al.)

6 Comparison between Theory and Exps. Binding energy Shallow case: B~ MeV Deep case: B~4-7 MeV Observations: B>1 MeV Width agreement: Γ~3-1 MeV By Y. Ichikawa

7 Recent measurements LEPS/SPring-8 A.O. Tokiyasu et al., Phys. Lett. B 78 (14) d(γ, K + " - ) reaction (E γ = GeV) Inclusive missing-mass σ m ~1 MeV Background K + Λ(15), K + " - "Y Upper limits:.-.36 GeV/c < &b for Γ=1 MeV, 9.9-6% of K"Y productions

8 HADES G. Agakishiev et al., Phys. Lett. B 74 (15) p+p K + GeV Bonn-Gatchina Partial Wave Analysis well reproduces the data pk + Λp K - pp production upper limit ~4 &b for Γ=7 MeV (.-.37 GeV/c ) Λ(145) production ~1&b

9 PTEP 15, 61D1 T.H J-PARC E15 T. Hashimoto et al., PTEP (15) 61D1. 3 He(K -,n) 1 GeV/c CDS σ/dω/dm A d )) (µb/sr/(mev/c Binding Energy [GeV]..1 Data BG Σ-decay BG neutral BG cell BG accidental M(K+p+p) Counts/1 MeV/c Semi-inclusive missing-mass σ m :5-15 MeV Arbitrary unit All K n K K n p Ksn - K N Λ π (π)(π) - K N Σ π (π)(π) K * N Y π,nkπ(π), K - EP 15, 61D1 K - pp production upper limit 1-7 &b/sr for Γ=1 MeV (~5% of QF K - n elastic) Binding Energy [GeV] (top) and the simulation (bottom). In the experimental.3 spectrum,. the.1 backgroundyields are sta each other, where BG -decay indicates ± -reconstructed events only. In the simulation spectrum T.Hashimotoetal. 35 from each reaction are sorted by 18 reaction products. )) (µb/sr/(mev/c σ/dω/dm A CDS d He(K, n)x missing mass (GeV/c ) Fig. 4. Comparison of the 3 He(K, n)x semi-inclusive missing-mass spectrum between exp.6-.9 GeV/c )) (µb/sr/(mev/c /dω/dm A CDS Downloaded from M(Λ+p).3 M(Λ+p) Data M(Σ+N) BG Σ-decay BG neutral BG cell BG accidental M(Λ+N+π) M(Λ+N+π) 15.5 Data BG Σ-decay He(K, n)x missing mass (GeV/c ) 1 BG neutral M(Σ+N). M(Σ+N+π) M(Σ+N+π) M(Λ(145)+p) M(Λ(145)+p) Binding Energy [GeV] Counts/1 MeV/c 5 Counts/1 MeV/c

10 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 ; >1~1 single-step reaction

11 J-PARC E7 d(" +, K + ) GeV/c Y. Ichikawa et al., PTEP (14) 11D3. Y. Ichikawa et al., PTEP (15) 1D1. Missing mass Yamazaki & Akaishi, Phys. Rev. C 76 (7) 451.

12 Experimental Setup SKS K1.8 beam line spectrometer 1.69 GeV/c " + LC TOF BVH SDC3 SDC4 K + SDC SDC1 Target BC4 BC3 BH p/p~x1-3 SKS spectrometer LAC RCA! + Q13 Q GeV/c K + D4 p/p~x1-3 (~1 msr Target : liquid deuterium(1.99 g/cm ) 3 m K1.8 Beam line Q11 Q1 BC BC1 BH1 GC

13 Expected Inclusive Spectrum dσσ /dω /dm o -16 o (Lab) d(" +, K + ) dσ /dω o -16 o (Lab) [µ b/sr/mev] QFΛ Λ Σ + QFΣ Old Bubble Chamber Data + deuteron Fermi motion K-pp QFY*+πYN Σ Σ* Λ* Missing Mass[GeV/c ]

14 p(π +,K + )Σ + GeV/c Σ + and Σ + (1385) : Σ + mass & width are consistent with PDG m FWHM =.8±.1 MeV/c Σ(1385) + d /d Lab [µb/sr] )] /d /dm o -16 o (Lab) [µb/sr/(4mev/c 7 data total + + p (1385) + + p K + + p K + K Σ + present data old data d Scattering Angle Lab [deg] Missing Mass [GeV/c ]

15 Measured d(π +,K + )X spectrum (a) (b) ΣN-ΛN GeV Mass shift for Y* by ~3 MeV K-pp

16 Range counter for Proton tagging Range Counter Arrays (RCA) 5 layers( cm) of Plastic scinti deg. (L+R) (a) 5 cm p+ (K1.8) 5 cm TOF β p K + (SKS).5 1/ b (b) p p PID

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

18 Coincidence Study Proton mom. >5 MeV/c Inclusive QFΛ, QFΣ, QFY*s are suppressed as expected!! What s left? Proton Coincidence

19 One-proton coincidence Coincidence Probability(MM) = One-proton coincidence(mm)/inclusive(mm) Enhancement near the ΣN threshold (.13 GeV/c ) Broad bump at ~.8 GeV/c

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

21 Mass-acceptance for each decay mode Λp Σ p Yπp

22 K - pp-like Structure Mass : Width : Binding Energy (stat.)+1 3 (syst.) MeV/c (stat.)+66 (syst.) MeV Σ p mode (stat.) +3 1 (syst.) MeV Relativistic Breit-Wigner

23 Λp/Σ p Branching Fraction ΣN cusp + ΣN ΛN conversion Preliminary p p = (stat)+.6.4 (syst) d d K pp! p =3. ±.3(stat) (syst)µb/sr d d (145) = 36.9 µb/sr d d K pp! p/ p/ d d (145) (7/8)%

24 Remarks Λ(145) production seems to be necessary, (OK for DISTO, HADES, J-PARC E7; for FINUDA,? for E15) but, not enough! Need to understand the Λ*(E)p K - pp dynamics sensitivity of the measurements 7% of Λ(145) in E7 < 4% in HADES

25 Discussion on K - pp Binding Energy is large (~1 MeV), and the width is broad. Not inconsistent with FINUDA, DISTO Theoretical calcs. are difficult to reproduce the large binding. [MeV] pp - Γ K A. Dote, T.Hyodo, W.Weise N.V.Shevchenko, A.Gal, J.Mares T.Yamazaki, Y.Akaishi Y.Ikeda, T.Sato N.Barnea, A.Gal, E.Z.Liverts S.Wycech, A.M.Green Y.Ikeda, H.Kamano, T.Sato This data DISTO FINUDA [MeV] B - K pp OBELIX

26 Other possibilities Dibaryon as "Λ -"ΣN bound states Y=1, I=3/, J " = + ; Λp (I=1/) decay is prohibited. Λ(145)N bound state I=1/, J " = - ; not so large binding A lower "ΣN pole of K- pp a broad resonance near the "ΣN threshold Enhanced KN interaction due to Partial restoration of Chiral symmetry; H. Garcilazo, A. Gal, NPA 897 (13) T. Uchino et al., NPA868 (11) 53. A. Dote, T. Inoue, T. Myo, PTEP (15) 43D. S. Maeda, Y. Akaishi, T. Yamazaki, Proc. Jpn. Acad., B 89 (13)

27 Summary K - pp -like structure is observed in the d(" +,K + pp)x reaction at 1.69 GeV/c in the Σ p invariant mass, for the first time. Binding Energy Width Branching Fraction (stat.)+3 (syst.) MeV 1 45 (stat.)+66 (syst.) MeV 78 p p = (stat)+.6.4 (syst) First evidence of Y=1, B=, S=-1 bound system No B=, S=-1 hypernuclei; Λ: B=3, 3 ΛH, Σ: B=4, 4 ΣHe How about B=, S=-??, ΛΛ-H dibaryon, ΞN