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a 0 (980) – f 0 (980) Mixing

a 0 (980) – f 0 (980) Mixing. Vera Kleber. Institut für Kernphysik Forschungszentrum Jülich. Physikalisches Institut Universität Bonn. Outline. Introduction Properties of a 0 (980)/f 0 (980) Experiments with a 0 (980)/f 0 (980) a 0 (980)-f 0 (980) Mixing Program at COSY Outlook.

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a 0 (980) – f 0 (980) Mixing

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  1. a0(980) – f0(980) Mixing Vera Kleber Institut für Kernphysik Forschungszentrum Jülich Physikalisches Institut Universität Bonn

  2. Outline Introduction Properties of a0(980)/f0(980) Experiments with a0(980)/f0(980) a0(980)-f0(980) Mixing Program at COSY Outlook

  3. Nonet of pseudo scalar mesons JP=0- S K0 K+ 1 h p- p0 p+ -1 h 1 I -1 K- K0 The Pseudo Scalar Resonances

  4. f0(500) (““) k(800) f0(980) a0(980) f0(1370) K0*(1430) a0(1450) f0(1500) f0(1710) Nonet of light scalar mesons JP=0+ S K0*(?) K0+*(?) 1 a0-(?) a00(?) f0(?) a0+(?) f0(?) -1 1 I -1 K0-*(?) K0*(?) The Light Scalar Resonances Possible candidates PDG, S. Eidelman et al., Phys. Lett. B 592, 1 (2004)

  5. a0(980)/f0(980) Nature What is their nature? qq state or 4 quark state or KK molecule A.V. Anisovich et al., Eur. Phys. J A 12 (2001) 103 D. Morgan, M.R. Pennington, Phys. Rev. D 48 (1993) 1185 N.N. Achasov et al., hep-ph/0201299 R.J. Jaffe, Phys. Rev. D 15 (1977) 267 J.A. Oller, E. Oset, Nucl. Phys. A 620, (1997), 438 G. Janssen et al., Phys. Rev. D 52 (1995) 2690 J. Weinstein, N. Isgur, Phys. Rev. D 41 (1990), 2236

  6. The a0(980) Resonance a0(980) IG(JPC) 1-0++ Mass 984.7 ± 1.2 [MeV] Width 50 – 100 [MeV] Decays dominantph seenKK seengg PDG, S. Eidelman et al., Phys. Lett. B 592, 1 (2004)

  7. The f0(980) Resonance f0(980) IG(JPC) 0+0++ Mass 980 ± 10 [MeV] Width 40 – 100 [MeV] Decays dominantpp seenKK seengg PDG, S. Eidelman et al., Phys. Lett. B 592, 1 (2004)

  8. The a0(980) and f0(980)Resonance ds √(G0Gph)Mr 2 = C dM Mr2-M2-iMr(Gph+GKK) Gph = gphq below threshold: GKK = igKK√(MK2 – (M/2)2) above threshold: GKK =gKK√((M/2)2 - MK2) E. Bratkovskaya et al., J. Phys. G 28 (2002) 2423

  9. Experiments: Inclusive pp→ d X+ Data LBL p p → d X+ pp = 3.8, 4.5, 6.3 GeV/c M.A. Abolins et al., PRL 25 (1970) 469

  10. Experiments: Radiative f-Decays KLOE @ DAfNE e+e- → f → p0p0g 75 f→ (f0(980) + s) g f→ f0(980) g 50 dBR/dm x 108 (MeV-1) f→sg Interf. 25 0 400 600 800 1000 m(pp) (MeV) A. Aloisio et al., Phys. Lett. B 537 (2002) 21

  11. Experiments: f1(1285) Decays L3 @ LEP e+e-→ e+e-gg → e+e-f1(1285) → e+e-hp+p- → e+e-ggp+p- f1(1285) a0(980) BW-Fit M= 98546 G= 50134 L3 Collaboration, Phys. Lett. B 526 (2002) 269

  12. Experiments: pp annihilation Crystal Barrel @ LEAR pp→ KLK+/-p-/+ Flatté m= 9823 G= 928 g1= 324 15 g2/g1= 1.01 K*(892) 2 KLK+/- 600 a0(1320) a0(980) a0(1450) 1.5 400 m2(K+p-/K-p+) / GeV2 entries / 0.0186 GeV2/c2 a0(980) 1 200 0.5 a0(1320) a0(1450) theoretical Dalitz Plot (from best fit of PWA) 0 1.4 0.5 1 1.5 2 1 1.2 1.6 m2(KLp+/KLp-) / GeV2 m2(KLK+/KLK-) / GeV2 A. Abele et al., Phys. Rev. D 57 (1998) 3860

  13. Experiments: J/Ψ Decays BES @ BEPC e+e-→J/Ψ→ f p+p- e+e-→J/Ψ→ f K+K- Flatté m= 96586 g1= 1651015 g2/g1= 4.21 0.25 0.21 f‘2(1525) f0(980) f2(1270)/ f0(1370) f0(980) M. Ablikim et al., hep-ex/0411001

  14. a0(980) f0(980) gh=gph2/8pm2 R=gKK2/gph2 gp=gpp2/8pm2 R=gKK2/gpp2 V. Baru et al., nucl-th/0410099 V. Baru et al., nucl-th/0410099 a0(980)/f0(980) Nature What is their nature? qq state or 4 quark state or KK molecule Which observable to measure at COSY? → a0(980)- f0(980) mixing amplitude

  15. a0(980)-f0(980) Mixing • idea similar to dd  ap0 experiment @IUCF • search for a reaction forbidden due to isospin conservation: dd  aa00(980) ( p0h) • allowed due to isospin conservation: dd  af0(980) ( pp) • a0(980)-f0(980) mixing: dd  af0(980) aa00(980) a p0h

  16. a0(980)-f0(980) Mixing • pilot measurement at ANKE: our estimate: s(dd  a f0(980)  a K+K–)~ 400 pb • strength of a0(980)-f0(980) mixing unknown • isospin violating reaction at WASA: our estimate: s(dd  a a00(980)) ~ (50 ... 200) pb Close & Kirk: mixing intensity = 8±3% but critizised by Achasov & Kiselev, Oller

  17. p0 h p0 h a0 a a ~ ≈ a0 1 1 f0 << p0 p0 h t -mNma0/f0 d d d d 1 ~ ma0/f0Ga0/f0 p0 a a h  mN Propagation p0 ( ) ) ( ≈ ≈ 20 CSB Ga0/f0 Production d d d d Details: C.Hanhart, nucl-th/0306073 dd  p0 vs. dd   (p0h) propagation of a0/f0 production CSB in or p0/h

  18. a0(980)- f0(980) Mixing-Amplitude Isospin violation reaction: dd → af0→ aa0→ ap0h ds/dm~ |L(m)|2 * |A|2 mph • ~ i gf0KKga0KK √s(pK –pK) → kaonic contribution mK02 – mK+2 md – mu L ~ √( ) = √( ) K+ K0 f0 a0 f0 a0 mK02 + mK+2 (md + mu)/2+ ms - L = + others K– K0 • additional measurement: • dd →aK+K- N.N. Achasov et al., Phys. Lett. B 88, 367 (1979)

  19. ~ 30 km ~ 50 km Aachen Köln ~ 70 km Bonn Forschungszentrum Jülich

  20. COSY Jülich Meson Production pp → pp X m(X) < 1.1 GeV/c2 pp → d X dd →aX

  21. COSY Jülich Isospin I(I3) 1(½,½) → 1(½,½,0) 1(½,½) → 1(0,1) 0(0,0) → 0(0,0) Meson Production pp → pp X m(X) < 1.1 GeV/c2 pp → d X dd →aX

  22. a0(980) Production near Threshold pp → da0+(980) →dK+K0 → dp+h Tp = 2.65 GeV QKK = 48 MeV Tp = 2.83 GeV QKK = 105 MeV ANKE

  23. Identification of pp  dp+h P. Fedorets et al., accepted by Yad. Fiz. (Phys. At. Nucl.)

  24. Ratio 10-1 ANKE Tp = 2.65 GeV Q = 48 MeV 10-2 0 0.1 0.2 0.3 Q [GeV] Branching Ratio a0+ → (K+K0) / (π+η) model dependent BR = (2.9 ± 0.8stat ± 0.9sys) % BR = (23 ± 5) % • Abele et al., • Phys. Rev. D 57, • 3860 (1998) P. Fedorets et al., accepted by Yad. Fiz. (Phys. At. Nucl.)

  25. Identification of pp  dK+K0

  26. Fit: [(KK)Pd]S+ [(KK)Sd]P stot(pp → dK+K0) = (38 ± 2stat± 14sys) nb Differential Distributions for pp  dK+K0 T =2.65 GeV (Q =48 MeV) →83% a+0 channel V.Kleber et al., Phys. Rev. Lett. 17, 172304

  27. pp  dK+K0 at Higher Energy T =2.83 GeV (Q =105 MeV) preliminary ndf2 = 2.5 black: best fit (in acc.) green: initial distrib. red: KK s-wave contrib. blue: KK p-wave distrib. →85% a+0 channel cos (pK+)

  28. Outlook dd  a K+K- @ ANKE • reaction serves as isospin I=0 filter • isospin conservation: f0 Planned measurements: dd →a π0η @ WASA • forbidden if isospin is • conserved • mixing f0n a0 Goals: • Goals: • cross section (dσ/dm) • dσ/dm (dd → απ0η ) • dσ/dm (dd →αK+K-) • → |mixing amplitude|2

  29. … What You Should Have Learned … Introduction Properties Experiments a0-f0 Mixing Program at COSY Outlook } → internal structure unknown → from mass distributions: 2 out of 3 unknowns (M and g22/g12 ) } → contains information on internal structure → another reaction to study CSB

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