1 / 31

Study of Kaon-pion interaction

Study of Kaon-pion interaction. T. Kishimoto Osaka University. Contents.  + as a K  N bound state X as a K  bound state Experiment to search for X (KEK-PS E548) Scalar meson and meson-meson interaction Experiment to study strange scalar meson.  + : Another explanation.

chana
Télécharger la présentation

Study of Kaon-pion interaction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Study of Kaon-pion interaction T. Kishimoto Osaka University

  2. Contents • + as a KN bound state • X as a K bound state • Experiment to search for X (KEK-PS E548) • Scalar meson and meson-meson interaction • Experiment to study strange scalar meson

  3. +: Another explanation • Consistent theoretical (quark) model • yet to be worked out • KN bound state • arXiv:hep-ex/0312003 (T.K and T.Sato and others) • Mass ~1540 MeV • M(KN) ~1570 MeV (30 MeV bound) • 10 MeV/particle (usual) • Spin parity ½+ (original prediction) • K  N system (s-wave) ½+ • This conjecture explains all Q+ properties particularly • Narrow width • Seen in Low Q, unseen in High Q

  4. Could + be a KN bound state • Known two Body interaction • N: weakly attractive • KN: weakly repulsive • K weakly attractive • K int. may have ambiguity • So strong to make K bound state No bound state X (new scaler particle)

  5. Width of + in KN conjecture • In order  to decay • KN ! KN ( has to be absorbed in N) • N (s-wave) !N (p-wave) • K-N (s-wave) ! K-N (p-wave) • KN have to interact simultaneously • Width ~ (strong) (R(int)/R())6 • R(int): Radius of Interaction • R(): Radius of 

  6. How to Decay N p p K p N p s s K R(int) R() Decay (R(int)/R())6 N K p

  7. Radius of + (and X) Asymptotic wave function () EB=30 MeV 15 MeV r~ 2 fm r~ 3 fm Extended object Seen only in Low momentum transfer reaction

  8. Width of + in KN conjecture • Width ~ (strong) (R(int)/R())6 • (strong) ~ a few 100 MeV • R(int) ~ 1 fm Radius of Interaction • R() ~ 3 fm Radius of  • () ~ 300 x (1/3)6 ~ 0.3 MeV • Consistent with observation • Production of Q+ → low q2 reaction

  9. New hypothetical particle X: K bound state • K interaction may be strong enough to make a bound state: New particle X • 0- + 0- → 0+ scalar particle • Binding energy less than 30 MeV • If deeper than 30 MeV Q+ decays into N and X • Probably a few MeV bound • Very extended object

  10. X (Why missed) • Lowest order decay modeX ! K • No strong decay MX< MK + Mp • No X→K  decay • (0+ → 0- + 1- L non cons. ) • No X→K e+e- • (vec. curr. vs axial charge (0+→ 0-) • No such decay mode is listed in PDG • No experimental searches ever made (Probably) • If it exists. • Hard to believe but possibility is there.

  11. Experiment to search for X • extended object→Low q2 reaction • r(X)~4fm: q2~ 50 MeV/c • Lowest q2 reaction • p(K-+ , X-+)p • @PK~1 GeV/c • q ~ 50 MeV/c • X ! K

  12. How to measure(KEK-PS-E548) • p(K-+ , X-+)p, X! K  • Measure Kaon momentum in coincidence with  rays • BG process: p(K-+ , K -+0), 0 ! • X particle gives highest PK • Measure invariant mass of K and two ‘s • Dedicated detector system • Study of K final state interaction

  13. Cross section PK~1.05 GeV/c Inelastic : ~5 mb ( production) (X) ~ (K) x f f: low relative momentum phase space Reaction mechanism b/sr order (1/1000) KEK-PS E548

  14. K+ momentum (MeV/c) K+p → X+p K+ scattering angle (cos q) K+ momentum (MeV/c) K+p → K+p0p K+ scattering angle (cos q) K+ momentum (PK=1 GeV/c) Max 950 MeV/c Signal Background Max 830 MeV/c

  15. Experimental condition(E548) • K+ beam from K2 beam line at KEK-PS • PK=1.2 GeV/c • 50k for 3x1012ppp • Target: 20cm thick H2O and 20 cm thick CH2 • Trigger • (K+, K+) x NaI(>5 MeV) • Rate ~ 500 ev/spill • NaI • Target region: 5x5 top and bottom • 10.5 cm from the beam center • Forward counter: 3x4 top and bottom • 13cm from the beam center • Data taking went well (2 days in this April)

  16. Spectrometer E548 Study of kaonic nuclei by (K-, p) reaction Search for X particle by (K+, K+ gg) reaction

  17. Current setup of E548 NaI 5x5 KURAMA NaI 3x4 FAC γ 20cm VZH BAC 2 LC BS BAC 1 K+ Target(water) BQC K+Beam 1.2GeV/c 10.5cm γ CV

  18. K+ momentum Tagged by 2γ PK=1.2 GeV/c K+ momentum X particle production 2 γ backward K+ momentum π0 production

  19. Typical cross section • p0 production cross section ~ 5 mb • ~10-3 of p0 • 1 MeV bound X (r~ 10 fm) • ~10-2 of p0 • 5 MeV bound X (r~ 4 fm) K+ X+ p0 p p

  20. X particle implies • K bound system X explains + properties • X might have been missed experimentally • If found, it means we found a new scalar particle (like k, strange partner of σ) • It is not only a solution of + but opens new world. • If not found, we still want to look for K final state interaction

  21. Study of meson-meson interaction at SPring8/LEPS • Recent observation of s meson. • How to produce scalar mesons • Beijin exp. to produce s by J/Y factory • Selection of spin parity • This may be true for other searches Dirac exp.

  22. J/Ψ(1-)ω(1-)π+π-(0+) π+ π- π0 • (a)|M π+ π- π0 –Mω|<40MeV/c2 ω (1－) • (b) π+ π- against ω f2(1270) (2+)peak • (c) ωπ invariant mass b1(1235) (1+)peak • (d) Dalitz plot

  23. Method II : several parameterization of the sigma pole are used 0++ 2++ b1(1235) background

  24. Study of K p interaction at SPring8/LEPS • X particle (X+), X0, X0, X－ • X+: mK++mp0=628.62MeV, mK0+mp+=637.24MeV • X0: mK++mp-= mK-+mp+= 633.21MeV • Isospin state or charge state • Threshold region ? X 4.59 4.03 K+-+p0 K-++p+- K0+p+-

  25. Spin parity relation 1－ 1/2+ 3/2－ 0+ K* 1－ 1/2+ 1/2+ 1－

  26. Study of strange scalar meson at SPring8/LEPS • X or k production • Photon energy

  27. Kp parameters Nucl.Phys.B133:490,1978

  28. Missing mass spectrum K* L(1116) gated k L(1520) gated attractive but no X k X L(1520) gated with X (looks repulsive)

  29. Resolution • Missing mass • Eg dependence 2GeV beam, mX~0.63 GeV L(1520): mp~0.94, EL~2.07, pL~1.4 DmX~0.4Eg L(1116): mp~0.94, EL~1.69, pL~1.27 DmX~0.8Eg

  30. Resolution • EL dependence L(1520): mp~0.94, EL~2.07, pL~1.4 DmX~ -2.5EL L(1116): mp~0.94, EL~1.69, pL~1.27 DmX~ -2.1EL p K－ L(1520) X Kp

  31. Experiment • Hydrogen target • Charged particle detector • Gamma detector Already available at LEPS, though configuration is not straightforward

More Related