KbarNN bound state search at J-PARC F. Sakuma, RIKEN on behalf of the J-PARC E15 collaboration MENU2016, July 25-30, 2016, Kyoto

Meson properties change What are Kaonic Nuclei? Bound states of nucleus and anti-kaon Predicted as a consequence of attractive KbarN interaction in I=0 Meson properties change in nuclear media? 1 2 3 Y.Akaishi & T.Yamazaki, PLB535, 70(2002). Will provide new insight on KbarN interaction in media

KbarN interaction - A good probe for low-energy QCD S.Ohnish et al.,PRC93(2016) 025207 KbarN Calculation on KbarN amplitude in I = 0 ? M. Bazzi et al., (SIDDHARTA Coll.), Phys. Lett. B704(2011)113 ＫＮ pS 𝐼= 1 2 , 𝐽 𝑃 = 0 − expected to be produced as a L(1405)p doorway

Pioneering Experiments on KbarNN B.E. = 103MeV G = 118MeV B.E. = 115MeV G = 67MeV “K-pp”Lp? Exp/Sim FINUDA@DAFNE DISTO@SATURNE PRL94(2005)212303 PRL104(2010)132502 6Li+7Li+12C(stopped K-, Lp) p + p  (L + p) + K+ @ 2.85GeV 2NA followed by FSI? PRC74(2006)025206 PRC82(2010)034608 etc. ppp(N*)p(LK+)? PRC92(2015)044002 vs. K.Suzuki, HYP2015 talk

Theoretical Calculations on KbarNN KbarN int. Chiral SU(3) (energy dependent) Phenomenological (energy independent) Method Variational Faddeev Barnea, Gal, Liverts Dote, Hyodo, Weise Ikeda, Kamano, Sato Yamazaki, Akaishi Wyceck, Green Shevchenko, Gal, Mares Ikeda, Sato B (MeV) 16 17-23 9-16 48 40-80 50-70 60-95 G (MeV) 41 40-70 34-46 61 40-85 90-110 45-80 KbarN interaction model: Chiral SU(3) [energy dependent] Phenomenological [energy independent] Calculation method: Almost the same results = depending on KbarN interaction  B.E. ~ 20 MeV  B.E. ~ 40-70 MeV Dote, Tue. A-1

Comparison between Calcs. and Exps. Binding energy Chiral: B.E. ~ 20MeV Phenomenological: B.E. ~ 40-70MeV Experiments (if KbarNN): B.E. ~ 100MeV Width almost agreement in G~40-100MeV Theor.: mesonic decay Exp.: non-mesonic decay Phenomenological Chiral

Recent Measurement at LEPS A.O. Tokiyasu et al., Phys. Lett. B 728 (2014) 616. Inclusive d(g, K+p-)X Eg = 1.5-2.4 GeV cosqlabK+/p- > 0.95 sMM ~ 10 MeV BG: gNK+p-L/S/L(1520) NO peak structure U.L.: 0.17-2.9 mb (= 1.5-26% CS of gdK+p-Y) M[K+p+p]  LEPS2 (4p measurement)

Recent Measurement at HADES Kpp th G. Agakishiev et al., Phys. Lett. B 742 (2015) 242 Exclusive pppLK+ E = 3.5 GeV Bonn–Gatchina PWA Well reproduces the data with N* resonances pppN*pLK+ NO peak structure U.L.: 0.7-4.2 mb (= 2-12% CS of pppK+L) L(1405) production = 9.2 mb  s(X=KbarNN)/s(L*) < ~50% PRC87(2013)025201 vs. DISTO: s(X) > s(L(1405)) @ 2.85GeV  Combined analysis with COSY-TOF/DISTO/HOPI/HADES (pppK+L)

Brief Summary --- What We Have Learned? --- Theoretical approach to KbarNN Largely depends on KbarN interaction below the KbarN threshold Need feedback from L(1405)/”K-pp” experiments Experimental approach to KbarNN Still controversial… Have to hunt small/broad signal from large/widely distributed QF-BG Exclusive measurement is crucial Other production channels are needed: p + A, in-flightK- + A

KbarNN Searches at J-PARC E27 d(p+,K+)X @K1.8 E15 3He(K-,n)X @K1.8BR Komatsu, Tue. A-5 Takahashi, Fri. D-3 Kawasaki, Fri. E-1 M.Naruki

J-PARC E27 Experiment d(p+, K+) reaction @ 1.69 GeV/c “K-pp” is expected to be produced as a L(1405) doorway ~1%? Yamazaki & Akaishi, Phys. Rev. C 76 (2007) 045201.

E27: Publications inclusive d(p+,K+)X Performed in 2012 Y. Ichikawa et al., PTEP (2014) 101D03. Y. Ichikawa et al., PTEP (2015) 021D01. exclusive d(p+,K+)Yp

K+ π+ E27: Experimental Setup K1.8 beam line spectrometer SKS spectrometer K1.8 beam line spectrometer 1.69 GeV/c p+ Dp/p ~ 2x10-3 SKS spectrometer 0.8-1.3 GeV/c K+ DW ~ 100 msr Target : liquid deuterium (1.99 g/cm2) K+ π+ K1.8 beam line spectrometer pπ = 1.69 GeV/c Y.Ichikawa

“K-pp” signal is hidden by QF!? E27: Inclusive d(p+,K+)X Y. Ichikawa et al., PTEP (2014) 101D03. expected spectrum “K-pp” signal is hidden by QF!? + data - expected SN-LN cusp Y* mass shift? Ichikawa, Tue. A-1 Tokiyasu, Fri. E-1 T.Nagae

K+ π+ E27: Experimental Setup K1.8 beam line spectrometer SKS spectrometer K1.8 beam line spectrometer 1.69 GeV/c p+ Dp/p ~ 2x10-3 SKS spectrometer 0.8-1.3 GeV/c K+ DW ~ 100 msr Target : liquid deuterium (1.99 g/cm2) K+ π+ Range Counter Arrays Range Counter Arrays (RCA) 5 layers of Plastic scinti. 39-122 deg. (L+R) 50 cm TOF Y.Ichikawa

E27: Two-Proton Coincidence pp > 250 MeV/c QFs are suppressed SN-LN cusp is clearly seen @ 2.13 GeV/c2 Broad enhancement is observed @ 2.28 GeV/c2 Y. Ichikawa et al., PTEP (2015) 021D01. < 2p coincidence spectrum > < 2p coincidence probability > = Y.Ichikawa, PhD-thesis. Kyoto-U (2015) < Inclusive spectrum > SN-LN cusp Broad bump Y.Ichikawa

E27: Decay Mode Separation ① ② ③ Y. Ichikawa et al., PTEP (2015) 021D01. Decay mode can be separated with MM[d(p+,K+pp)X] two-protons in final state: K+Lp, K+S0p, K+Ypp ① ② ③

E27: “K-pp”-like Structure Y. Ichikawa et al., PTEP (2015) 021D01. Detector Acceptance “K-pp”-like structure in S0p decay mode: Mass Binding energy Width Relativistic Breit-Wigner M(p+S+N) M(K+p+p) S0p T.Nagae

E27: “K-pp”-like Structure Y. Ichikawa et al., PTEP (2015) 021D01. Decay branch: S0p Lp ds2/dW/dM2-14 deg.(Lab) [mb/sr/(15MeV/c2)] preliminary M(K+p+p) M(p+S+N) Theor. Cal. on Y*NYN : GLp/GS0p = 1.2 Sekihara, Jido, Kanda-En’yo PRC79(2009)062201(R). ds/dW“K-pp”S0p: Y.Ichikawa, PhD-thesis. Kyoto-U (2015) p(p-,K0)L(1405) @ 1.69GeV/c: ds/dWL(1405)=36.9mb/sr BNL, NPB56(1973)15 = (ds/dW”K-pp”Yp) / (ds/dWL(1405)) ~ 7-8%  large prob. of L(1405)p“K-pp” c.f., large prob. in DISTO, but < 50% in HADES T.Nagae

J-PARC E15 Experiment --- KbarNN via 3He(K-,n) ---

J-PARC E15 Experiment 3He(in-flight K-,n) reaction @ 1.0 GeV/c 2NA processes and Y decays can be discriminated kinematically ① semi-inclusive (K-,n) ② exclusive (K-,Lp)nmissing

Only 4days data-taking in 2013 E15: Publications E151st experiment: Only 4days data-taking in 2013 inclusive 3He(K-,n)X exclusive 3He(K-,Lp)n T. Hashimoto et al., PTEP (2015) 061D01. Y. Sada et al., PTEP (2016) 051D01.

Experimental Setup 15m

Semi-Inclusive 3He(K-,n)X DATA sub-threshold excess (Y* and/or KbarNN?) Quasi Elastic K- + 3He  K- + n + ps + ps ds/dWq=0deg ~ 6mb/sr Charge-Exchange K- + 3He  K0 + n + ds ds/dWq=0deg ~ 11mb/sr MC T. Hashimoto et al., PTEP (2015) 061D01.

Semi-Inclusive 3He(K-,n)X NO bump structure FINUDA/DISTO/ E27 T. Hashimoto et al., PTEP (2015) 061D01.

Exclusive 3He(K-,Lp)n Y.Sada et al., PTEP (2016) 051D01.

Inclusive 3He(K-,Lp)X Y. Sada et al., PTEP (2016) 051D01. S0pn YNNpp Lpn Lpns (2NA) x20 Lpn S0pn YNNpp YNNp YNNppp YNNp YNNppp Global fit both in Lp invariant- and missing-mass s ~ 10 MeV/c2 w/ simulated spectra Neutron was identified by kinematics 3He(K-, Lp)nmissing c.f. 3NA(Lpn): # of Lpn events: ~200 S0pn contamination: ~20%

Exclusive 3He(K-,Lp)n A bump structure exists near the K-pp threshold Prefers Smaller momentum transfer to Lp (0.8<cosqCMn) S=-1 dibaryon? L*N? KbarNN? … Y. Sada et al., PTEP (2016) 051D01.

Assuming a Breit-Wigner c2-test with pole & 3NA(Ypn) – S-wave Breit-Wigner pole – w/ Gaussian form-factor Y. Sada et al., PTEP (2016) 051D01.

Assuming a Breit-Wigner Y. Sada et al., PTEP (2016) 051D01. phase space Breit-Wigner form factor B.E = 15+6-8 (stat.) ± 12(syst.) MeV/c2 = 110+19-17(stat.) ± 27(syst.) MeV/c2 Q = 400+60-40 MeV/c

A Theoretical Interpretation Sekihara, Oset, Ramos, arXiv:1607.02058 Chiral unitary approach Sekihara, Tue. A-1 quasi-elastic kaon scattering Uncorrelated L(1405)p state KbarNN bound-state B=16MeV G=72 MeV Opt.A (Watson) Opt.A (Watson) M[K+p+p] M[K+p+p]

E15-2nd Experiment --- completed in Dec. 2015 --- What is the structure observed in E151st data? E15-2nd Experiment --- completed in Dec. 2015 --- E15-1st in 2013 E15-2nd in 2015 data-taking 4 days 3 weeks (K-,n) ~7 times more data (K-,Lp) ~30 times more data* * dedicated trigger was introduced for (K-,Lp)

preliminary Inclusive 3He(K-,Lp)X E152nd E151st ~0.2k ~6.0k miss. gn (S0p) preliminary M[K+p+p] miss. n (Lp) ~6.0k

preliminary Exclusive 3He(K-,Lp)n E152nd E151st E152nd Two structures are seen around M[K+p+p]!? preliminary M[p+S+N] M[K+p+p]

3He(K-,Lp)n: Angular Dependence M[K+p+p] 0 < cosqn< 0.75 0.75 < cosqn M[K+p+p] preliminary Sekihara, Oset, Ramos, arXiv:1607.02058

More detailed analysis will be shown in - angular dependence, decay mode, etc. Yamaga, Tue. A-1 Summary

Present Status of KbarNN Exp. CANDIDATES Upper limit LEPS/HADES B.E ~ 15 MeV E151st B.E. ~ 100 MeV FINUDA/DISTO/E27 Theor. calculations. Difficult to reproduce deeply bound state w/ normal KbarN int. Key measurements L(1405) production  L*N doorway pSN decay channel  new info. of KbarNN Phenomenological Chiral KbarNN or NOT?  Other Possibilities Y*N dibaryon? / pYN pion-assisted dibaryon? / Double-pole KbarNN? / Partial restoration of Chiral symmetry? Dote, Tue. A-1

KbarNN searches @ J-PARC E27: d(p+,K+)Yp @ 1.69 GeV/c “K-pp”-like structure was found in S0p B ~ 100 MeV/c2 G ~ 160 MeV/c2 G(Lp)/G(S0p) ~ 1 E15: 3He(K-,Lp)n @ 1.0 GeV/c Structure around the threshold was fond in Lp B ~ 15 MeV/c2 G ~ 110 MeV/c2 Q ~ 400 MeV/c Y. Ichikawa et al., PTEP (2014) 101D03. Y. Ichikawa et al., PTEP (2015) 021D01. large prob. of L(1405)p“K-pp” T. Hashimoto et al., PTEP (2015) 061D01. Y. Sada et al., PTEP (2016) 051D01. E151st results E152nd results Two structures !? Yamaga, Tue. A-1 Further theoretical inputs are welcome!

Thank You! J-PARC E15 Collaboration

Spares

E27: One-Proton Coincidence pp > 250 MeV/c QFs are suppressed SN-LN cusp is clearly seen @ 2.13 GeV/c2 Broad enhancement is observed @ 2.28 GeV/c2 Y. Ichikawa et al., PTEP (2015) 021D01. < 1p coincidence spectrum > < 1p coincidence probability > = < Inclusive spectrum > SN-LN cusp Broad bump

Experimental Setup Beamline spectrometer Target System 1.0 GeV/c K- Dp/p: 0.2% Target System ~0.5l Liquid 3He @ 1.4K r = 0.081 g/cm3 Cylindrical Detector System Acceptance: 54<q<126 deg. 59% of 4p Dpt/pt: 5.3% pt + 0.5%/b Neutron Counter Acceptance: 20 msr Dp/p for 1.2GeV/c n: 0.7%

Subthreshold Excess? K-pK0+nfw K-dY*+nfw K-3HeY*N+nfw preliminary M(K-) K-pK0+nfw K-dY*+nfw K-3HeY*N+nfw p(K-,n)X well describes the spectrum preliminary M(K-+p) Y* production are seen as excess d(K-,n)X The main goal of E31 Fermi motion M(K-+p+p) Y* production (and/or exotic production) are seen as excess 3He(K-,n)X Fermi motion Exclusive analysis is crucial!

A Theoretical Interpretation Sekihara, Oset, Ramos, arXiv:1607.02058 Chiral unitary approach Sekihara, Tue. A-1 KbarNN state Sekihara, Oset, Ramos, arXiv:1607.02058 A: Watson app. B: Faddeev app. B=16MeV, G=72 MeV quasi-elastic kaon scattering M[K+p+p] KbarNN bound-state picture reproduces the data  The data CANNOT be explained with uncorrelated L(1405)p

E15 1st vs 2nd Y. Sada et al., PTEP (2016) 051D01. E15-2nd

Exclusive 3He(K-,Lp)n The events widely distribute in the phase space Contribution from 2NA processes seem to be small Event concentration is seen at TCMn/QCM~0.4

Exclusive 3He(K-,Lp)n E151st E152nd preliminary

KbarNN or NOT? --- Other Possibilities A structure near KbarNN threshold L(1405)N bound state loosely-bound system, I=1/2, Jp=0- various decay modes, LN/SN/pSN pLN-pSN dibaryon structure near pSN threshold I=3/2, Jp=2+  no Lp decay (I=1/2)? Double-pole KbarNN loosely-bound KbarNN, & broad resonance near the pSN threshold  pSN decay Partial restoration of Chiral symmetry enhancement of the KbarN interaction in dense nuclei T. Uchino et al., NPA868(2011)53. A structure near pSN threshold H. Garcilazo, A. Gal, NPA897(2013)167. A. Dote, T. Inoue, T. Myo, PTEP (2015) 043D02. S. Maeda, Y. Akaishi, T. Yamazaki, Proc. Jpn. Acad., B89(2013)418.

Smaller momentum transfer is preferred Exclusive 3He(K-,Lp)n Small cos(qn) M[K+p+p] preliminary sliced Large cos(qn) Sekihara, Oset, Ramos, arXiv:1607.02058 Smaller momentum transfer is preferred

3He(K-,Lp)n: Decay Channel M[K+p+p] preliminary Lp S0p sliced Lp S0p Lp~S0p S0p pYN S0p~pYN G(Lp) > G(S0p) !?