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KLOE results on light mesons properties

ICHEP08, Philadelphia 30/07/2008. KLOE results on light mesons properties. Cesare Bini Sapienza Universita’ and INFN Roma on behalf of the KLOE collaboration. Outline: Overview of the KLOE experiment at DAFNE Results on scalar mesons Results on h – h ’ physics Measurement of f  wp 0

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KLOE results on light mesons properties

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  1. ICHEP08, Philadelphia 30/07/2008 KLOE results on light mesons properties Cesare Bini Sapienza Universita’ and INFN Roma on behalf of the KLOE collaboration Outline: Overview of the KLOE experiment at DAFNE Results on scalar mesons Results on h – h’ physics Measurement of fwp0 Hadronic cross-section update Conclusions and outlook

  2. 1. Overview of the KLOE experiment at DANE DAFNE @ Frascati Laboratories • e+e-collider with 2 separate rings: s ~ Mf= 1019.4 MeV • During KLOE run the luminosity has reached the maximum value of 1.5×1032 cm-2s-1 in 2005 DAFNE STATUS:  March 2006: end of KLOE data taking 2500 pb-1 on-peak 8 × 109f decays 200 pb-1 off-peak (energy scan+1 GeV run); • DAFNE upgrade: test in progress; • New KLOE run starting from mid-2009.

  3. The KLOE detector: A large drift chamber A hermetic calorimeter A solenoidal superconducting coil Drift Chamber (He-IsoBut. 2m × 3m) E.M. Calorimeter (lead-scintillating fibres) Magnetic field (SuperConducting Coil) = 0.52 T (solenoid) The KLOE physics program: Kaon physics: CP and CPT violation, CKM unitarity, rare decays, ChPT tests Hadron physics: lowest mass pseudoscalar, scalar and vector mesons Hadronic cross-section below 1 GeV: hadronic corrections to g-2

  4. 2. Results on scalar mesons. The lowest mass scalars: f0(980), a0(980), f0(600)[s] are accessible through radiative decays in pairs of pseudoscalars Final states: f  p+p-g f0(980), (500) f  p0p0g f0(980), (500) f  hp0g a0(980) f  KKg f0(980), a0(980) BRs < 10-4 Motivations: 1. f  |ss> scalar quark composition of f0(980), a0(980) 2. Search for evidence of   nature of scalar mesons (4q vs. 2q) Mass (GeV/c2) f(1020) 1 a0(980) f0(980) k(800) s(500) 0 I=0 I=1/2 I=1 : Phys.Lett.B634 (2006) 148; : Phys.Lett.B537 (2002) 21; Eur. Phys.J. C49 (2006) 433; h : Phys.Lett.B536 (2002) 164.

  5. KLOE observed the decay  f0(980) in and 00 channels: •  Large unreducible backgrounds, small signals • Fits of the mass spectra  extraction of signal rate and shape (parametrizations of signal and bck are required) Dalitz plot f0(980) massspectrum Comments: 1.The Kaon-Loop model (N.Achasov et al.) describes the mass spectra; 2.The f0(980) is strongly coupled to the s quark: gf0KK > gf0p+p- 3.The scalar amplitude has a large low mass tail (m<600 MeV) that can beinterpreted as due to the (600).

  6. NS () (+0) • Recently KLOE has reported a high statistics study of the decay •  h0   a0(980) • Small unreducible background (a0(980) dominated) • Combined fit of M(h0) spectra in case of hgg and hp+p-p0 Results: (1) Branching ratio (errors reduced factor ~3) (2) Combined fit: KL = Kaon-Loop fit (Achasov, Gubin, PRD63(2001)094007) NS = No-Structure fit (Isidori et al., JHEP 0605:049,(2006) ) Rh = BR(hgg)/BR(hp+p-p0) free in the fit (PDG value = 1.73 ± 0.04) • data • fit (including efficiency and smearing)

  7. (+–0) () Br(0) • Comparison with predictions. • Branching Ratios vs several models: qq: Achasov-Ivanchenko NPB315(1989) Close et al., NPB389(1993) 4q: Achasov-Ivanchenko NPB315(1989) KK molec.: Close et al., NPB389(1993) Achasov et al., PRD56(1997) KK molec.-2: Kalashnikova et al., EPJA24(2005) Palomar et al., NPA729(2003): UPT Escribano, PRD74(2006): Linear  model (2) Coupling Ratios compared to simple SU(3) predictions:  qqqq == 4quark model  qq1 == 2quark (f0 = ss, a0 = nn)  qq2 == 2quark (f0 = nn, a0 = nn) Br(00++–) No simple conclusion:  f0(980) has a large ss component  a0(980) has a small or null ss component

  8. Recently has been suggested to include “instantons” to describe light scalar mesons decays [‘t Hooft,Isidori,Maiani,Polosa,Riquer, arXiv0801.2288] =cf +ci Adding the instanton term an improved agreement is found between the 4q-model and the measured couplings Prospects in this field: Improve theoretical tools for fitting spectra; Search of  KK: soon KLOE result (sensitivity 10-8)  and .

  9. 3. Results on h - h‘physics. • KLOE contributes to h – h‘ physics through the radiative decays • f hg BR = 1.2 × 10-2 • f  h’g BR = 6.2 × 10-5 • List of measurements performed and/or in progress: • Precision measurement of the  mass • (JHEP 12 (2007)073) • (2) Improved measurement of the  - ’ mixing (Phys.Lett.B541(2002) 145) – (Phys.Lett.B648(2007)267) • (3) Dynamics of +p-p0 and 30decays • (JHEP 0805 (2008)006) • (4) Dynamics of +p-g decay • (5) Measurement of B.R.(-e+e-) • (6) Measurement of B.R.(ee-e+e-) • (7) Observation of 0gg

  10. Dynamics of the 3 decay '3decay isospin violation in strong interactions: mu md ms  a test of low energy effective theories of QCD KLOE has studied with high statistics the dynamics of both channels:   Dalitz plot analysis: 1.34 106 events   ”slope” analysis: 0.65 106 events   Dalitz plot: - large statistics - negligible background  2dim – fit with the parametrization

  11. Results a=-1.090  0.005 +0.008-0.019 b= 0.124  0.006  0.010 d= 0.057  0.006 +0.007-0.016 f= 0.14  0.01  0.02 Comments: 1. odd terms in X compatible with 0; 2. quadratic term in X (d) unambiguosly  0; 3. cubic term in Y (f) needed to get an acceptable fit; 4. the b=a2/2(current algebra rule) is violated.  Analysis of the asymmetries KLOE results: x 5 statistics respect to best previous experiment All asymmetries are compatible with 0 up to the 10-3 level: No C-violation in h-decays observed.

  12. Fit results of the   ”slope” 1dim fit of the z distribution with 1 parameter: a. • Alternative fit of   +- including pp rescattering (following G.D’Ambrosio et al.,Phys.Rev.D50 (1994)5767) Only 4 free parameters  estimate of h  3p0 dynamics

  13. 4. Measurement of f wp0 OZI and G-parity violating process, large background from e+e- r/r’  wp0 Method: measurement of the cross-section s(e+e- wp0) vs. Ec.m.: • Data at 1000 < Ec.m. < 1030 MeV •  p+p-p0 and w  p0ganalyzed • simultaneous fit, extraction of • Re(Z) and Im(Z) where Z is the ratio (b)/(a) Results: (1) from the fitted value of Z BR(f wp0)=(4.4 ± 0.6) ×10-5 (2) From the ratio between the two channels G(w  p0g)/G(w p+p-p0 )=0.0897 ± 0.0016 and finally, using unitarity: BR(w p+p-p0)= (90.24 ± 0.19)% BR(w  p0g ) = ( 8.09 ± 0.14)%

  14. 5. Hadronic cross-section measurement update KLOE has measured the cross-section s(e+e- p+p-)for0.35 < q2 < 0.95 GeV2 using the ISR method (Phys.Lett.B606(2005)12) Crucial ingredient for am = (g-2)/2 “theoretical” evaluation. + - s‘ s New measurement on an independent sample (2 x stat.) and with improved analysis strategy:  the new result for am confirms the previous one: am(OLD) (0.35 < q2 < 0.95 GeV2) = (388.7 ± 0.8stat± 3.5sys± 3.3th) × 10-10 am(NEW) (0.35 < q2 < 0.95 GeV2) = (388.2 ± 0.6stat± 3.3sys± 2.0th) × 10-10 Substancial agreement with BINP results, e+e- vs. t discrepancy is still there For g-2 Theo – Exp = -3.4 s is “confirmed”. (J.P.Miller et al., Rept.Prog.Phys.70:795,2007)

  15. 6. Conclusions and Outlook DAFNE is testing now a new scheme to increase luminosity The first results are extremely encouraging, work still in progress KLOE phase-2 willstart in 2009. A program in 3 steps: 1. ~ 5 fb-1 with present detector + “validation” of the new DAFNE scheme on KLOE; 2. detector upgrade: new inner tracker,  tagger(s), new small angle calorimeter(s); 3. KLOE2 Run: the goal is to reach a statistics of 40  50 fb-1 in 3  4 years. KLOE2 Physics Program (see EoI, http://www.lnf.infn.it/lnfadmin/direzione/roadmap/LoIKLOE.pdf) (1) - Flavour Physics: CKM Unitarity test, Lepton Universality, Search for signals of New Physics, Tests with KS-KL QM-correlated pairs (2) - Low-energy QCD Measurements in the Kaon sector, h and h’ physics, the low mass scalar mesons, gg physics.

  16. Backup slides

  17. List of the  decays: branching ratios and number of events “on tape” B.R. Nev KLOE (2.5 fb-1) K+K- 0.49 3.7  109 K0K0KSKL 0.33 2.5  109  0.15 1.1  109 1.3  10-2 9.7  107 1.2  10-3 9.0  106 ’6.2  10-5 4.6  105 (f0(980), )3  10-4 2.5  106  (a0(980))7  10-5 4.6  105 KK(f0(980), a0(980))?? Initial State Radiation e+e-

  18. Search for the decay  KSKS In K0K0 the K0K0 pair is: in a J=0 state  = [|KSKS>-|KLKL>]/2; in a I=0,1 isospin state a0 and f0 contribute; Very small allowed phase space: 2MK < MKK < Msmall B.R. Predictions on B.R.: from 10-13(no scalar contribution) up to 10-7 • We have used the decay chain: •  KSKS  ()()  4 tracks+1 photon (Emax=24 MeV) • Overall efficiency = 20.6% • Very small bckg (ISR KSKL) Result (preliminary): (Ldt = 1.4 fb-1) 1 event found; 0 expected background; BR( KSKS)<1.810-8 90% CL

  19. Rare decay:PT and VDM predictions  BR  3  10-4 2 measurements: CMD-2 (4 events) and WASA@CELSIUS (16 events) Non conventional CP violation (non CKM)  plane asymmetry [D.N.Gao MPLA17(2002)] Measurement of B.R.(+─e+e─)  • KLOE preliminary result on a • reduced data sample: 622 pb-1 • M(+─e+e─) distribution: • fit with signal + background (MC) •  733  62 events (global efficiency = 11.7 %) • BR(+─e+e─)=(2.4  0.2  0.4)  10-4 • In progress: • Bckg reduction (h  p+p-g with g conversion) • Full KLOE statistics

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