Experimental Nuclear and Hadronic Physics Laboratry Department of Physics Kyoto University Search for Kaonic nuclei at SPring8LEPS GCOE Symposium 12 th 14 th Feb2013 Kyoto University ID: 1045433
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1. Atsushi Tokiyasu(for LEPS collaboration)Experimental Nuclear and Hadronic Physics Laboratry,Department of Physics, Kyoto UniversitySearch for Kaonic nuclei at SPring8/LEPSGCOE Symposium12th – 14th .Feb.2013 @ Kyoto University
2. strangeness in nuclei2013/2/13GCOE Symposium @ Kyoto University1 / 11ds us, SU(3) octet baryonSU(3) nonet mesonLK?Hyper nucleiShrinkage impurity effect.nuclear force in SU(3) Kaonic nucleinew form of the nucleiwhether exist or not?What happens in nuclei?udshyperonkaon
3. dependent on the models of KN interaction the calculation methods.Formation of Cold (T=0) and Dense (r > 2r0) nuclei.2013/2/13GCOE Symposium @ Kyoto University2 / 11K can be bound in the nuclei by strong interaction. K N interaction (I=0) is strongly attractive !X-ray shift of Kaonic HydrogenK- p scattering data 2-body: KN : L(1405) ?3-body: KNN : lightest nucleus. K-pp the strongest bound state in 3-body systemsTheoretical prediction (All theory support the existence)B.E. = 20-100 MeVG = 40- 110 MeV If G > B.E, it is difficult to observe experimentally. Ref: Particle Data GroupKaonic nuclei
4. Experiments2013/2/13GCOE Symposium @ Kyoto University3 / 11FINUDA @ DAFNE (2005)DISTO@ SATURNE(2010)stropped K- on (6Li, 7Li, 12C, 27Al and 51V)p p L p K+B.E. =B.E. =G =G =invariant mass (L + p)Missing mass (K+)MeVMeVMeVMeVM.Agnello, Nagae and Fujoka et al., PRL 94, 212303 (2005)T.Yamazaki et al., PRL 104, 132502 (2010)K-pp L p , S0 p, S+ n (non-mesonic decay) easy to identify experimentally S p p (mesonic decay)
5. Summary of the introductionK-pp is the lightest kaonic nuclei.Existence of K-pp is not established. Experimental search using different reactions are awaited!Forthcoming experiments3He(K-, n)X E15 @ J-PARC D(p+, K+)X E27 @ J-PARCg D K+ p- X LEPS @ SPring-82013/2/13GCOE Symposium @ Kyoto University4 / 11 Prof.Nagae’s talk
6. g D K+ p - X reaction2013/2/13GCOE Symposium @ Kyoto University5 / 11K+p-g“K” exchanged in t-chanel unique for g-induced reaction ( J = 1)polarization observables are available.K-pp is “soft” object. small momentum transfer detect K+ and p- at forward angleSearch for a bump structure in the missing mass spectrum Mx2 = (Eg + MD – EK- Ep)2 - (pg – pK - pp)2 independent of decay chanel.K, K*Y*pnpK-pY*(Eg, pg)(EK, pK)(Ep, pp)(MD,0)Y* door-way.
7. SPring-8 “Super Photon ring-8 GeV”2013/2/13GCOE Symposium @ Kyoto University6 / 11Data take:2002/2003, 2006/2007 7.6 x 1012 photons on LD2 targetSPring-8: 8 GeV electron storage-ringLEPS : hadron physics using g beamBack-word Compton ScatteringeeDetect withTagging counterEg=1.5 - 2.4 GeVexperimentalhatch 355nm laser8 GeVLEPSDEg=12 MeV
8. LEPS spectrometer2013/2/13GCOE Symposium @ Kyoto University7 / 11TOFDipole Magnet 0.7 [Tesla]TargetStart CounterDC2DC3DC1SVTXAC(n=1.03)SSD(SVTX)Drift Chamber(DC 1~3)positionStart Counter(SC)Time of flight wall(TOF)timeAerogel Cherencov counter(AC)Start Counter (SC)trigger g (1.5-2.4 GeV)p-K+
9. particle identification2013/2/13GCOE Symposium @ Kyoto University8 / 11K+p-Dp/p ~ 6 MeV/c @ 1 GeV/cTOF (Time of flight)m2 = p2(1/β2 - 1)line tracking + Runge-Kutta method.mass p = 938.3 MeVmass K+ = 493.7 MeVmass p- = 139.6 MeVc.f.pp+K-0
10. Missing Mass Spectrum2013/2/13GCOE Symposium @ Kyoto University9 / 11Error Bar : statistical uncertainty (~5%)Red Box : systematic uncertainty (~20%)Hatched : discrepancy between datasets (~12%)preliminaryNo bump structure was observed!upper limit of cross sectionLSnsearch region: Mass = 2.22 - 2.36 GeV/c2 B.E. = 150 - 10 MeVacceptance was corrected with Monte-Carlo simulationexpected signal
11. Upper Limits of differential cross section2013/2/13GCOE Symposium @ Kyoto University10 / 11preliminary-G= 20 MeV 0.05 - 0.25 mb-G = 60 MeV 0.15 - 0.6 mb-G =100 MeV 0.15 - 0.7 mba few % of typical hadron production cross section.g N L K p (~8 mb )g N S K p (~4 mb)B.E. 15 points (10-150 MeV)G 3 points upper limits of cross section were determined log likelihood ratio method
12. Conclusion and future prospectThe existence of Kaonic nuclei is not established.K-pp was searched for using g D K+ p - X reactionNo bump structures were found, and the upper limits of differential cross section were determined to be a few % of typical hadron production cross section.Future prospectdetect the decay products from K-pp. increase S/Nsearch for other charge states using gDK+ K-pn , gDK+p+ K-nn2013/2/13GCOE Symposium @ Kyoto University11 / 11
13. Collaborators2013/2/13GCOE Symposium @ Kyoto University12 / 15
14. Appendix2013/2/13GCOE Symposium @ Kyoto University13 / 15
15. AppendixMeritdeuteron small nuclear effect(FSI).additional p- emission reduce the momentum transfer.K can be exchanged.polarization observable is available.Demeritsmall cross section (~nbarn).many background sourcelimited information on hadron resonance.necessary to detect the decay product.2013/2/13GCOE Symposium @ Kyoto University14 / 15
16. Calculation of Upper Limits2013/2/13GCOE Symposium @ Kyoto University15 / 15preliminarypreliminaryUpper Limit was calculated with log Likelihood ratio methodBackground proces - g p K+ p- L - g p K+ p- S - g p K+ p- S(1385) - g p K+ p- S(1385)- - g p K+ p- p Lconstant offsetSignal Breit Wigner distribution-2DlnL = 3.841 upper limit (95% C.L.)Signal Yield
17. Theoretical calculation2013/2/13GCOE Symposium @ Kyoto University16 / 15Binding EnergyDecayWidthMethodYamazaki and Akaishi48 MeV61 MeVPhenomenologicalVariatioal MethodDote, Hyodo and Weise20±3 MeV40-70 MeVChiral SU(3)Variational MethodIkeda and Sato60 – 95 MeV45 - 80 MeVChiral SU(3)Fadeev CalculationShevchenko, Gal and Mares50 – 70 MeV90 – 110 MeVPhenomenologicalFadeev CalculationS. Wycech and A. M. Green56.5~78 MeV39~60 MeVUchino, Hyodo and Okadepend on L* NVariational MethodAll calculations predict that K-pp can exist!!However… B.E. = 20 – 100 MeV G = 40 – 110 MeV Depending on the K N interaction model and Calculation Method.
18. Background processes2013/2/13GCOE Symposium @ Kyoto University17 / 15preliminary15 quasi- free processes were considered for fitting.N Y K+ Y K+ p- Y* K+ p- Y K+ p- pThe main background (~20 %)n K+ L(1520) Sp Lpp g N K+ p- XMM(K+)MM(K+,p-)MM(K+)MM(K+,p-)c2/ndf ~ 1.3Yhyperon (L,S)Y* hyperon resonance (L(1405),S(1385)…)