Scalar mesons and d0-d2 at KLOE Claudio Gatti, Università di Roma La Sapienza - INFN For the KLOE collaboration DANE and KLOE Scalar mesons a0 and f0 Measurement of BR(00,0) Measurement of BR(KS+-/00) and 0-2 Conclusion QCD@WORK 2003 Conversano June 14-18 2003

DAFNE electron-positron collider

KLOE DC EmC Stereo geometry: 60-150 mrad Cell size: 2x2 3x3 cm2 Spatial resolution: EmC Lead scintillating-fiber calorimeter Thickness: 15 radiation lengths (x01.5cm) Granularity: 4.4x4.4 cm2 Trigger: based on DC and EmC signals.

Scalar mesons a0(980) I=1 f0(980) I=0 BR((f0 a0) )  10-5 qq model ma = mf ~ 980 MeV  SS disfavoured S q OZI rule Suppression of  decays into final states without strange quarks BR((f0 a0) )  10-5

Scalar mesons   qqqq model KK molecule K+ K- a0, f0 Diffuse system R2 fm, F2(R)<1 Compact system R<1 fm, F2(R)1 BR ~ 210-4F2(R) BR2 10-4 BR < 10-5 if Fa0=Ff0 and gakk=gfkk

 f0(980),a0(980) f000 a00 5 +- 5  gKK gSKK gSPP p  S  PP invariant mass spectrum fitted by folding the shape predicted by a model with experimental resolutions: Fitting function: Parameters: gSKK gSPP MS

 00 BR(00)= (1.090.03stat0.05syst)10-4 Signal  00 BKG e+e- 00 Selection: 5 prompt clusters. ETOT>800 MeV, PTOT< 200 MeV/c. Kinematic fit for E, P conservation and photon pairing. cut on pion mass |M-M|< 5. BKG rejection (M, cos, 2). L~16 pb-1 ~5 107  243861 events PL B537 (2002) BR(00)= (1.090.03stat0.05syst)10-4

 05,+-5 BR(0)= (8.50.5stat0.6syst)10-5 Signal  5 BKG e+e-0 00   00 60736 Signal  +-5 BKG e+e-0 +- 4 KSKL 19714 0  BR(0)= (8.50.5stat0.6syst)10-5 PL B536 (2002) BR(0)= (8.00.6stat0.5syst)10-5

Mass spectrum fit BR(f0)= (4.470.21)10-4 BR(a0)= (7.40.7)10-5 R=BR(f0)/ BR(a0)=6.1±0.6 g2(f0KK)/g2(a0KK)= 7.00.7

BR(KS+-())/ BR(KS00) and 0-2 In the limit of exact isospin symmetry, isospin phases and amplitudes can be extracted from K decays. 0-2=(56.7± 3.8 ) from BR in PDG 8 (Cirigliano et al. (2000)) Expected 0-2=(47.7±1.5) from G. Colangelo et al. (2001) ECUTOFF(MeV) 0-2-em In the presence of isospin breaking effect, like EM: 0-2  0-2-em em  3.2 (Cirigliano et al. (2000)) Data must be analyzed with the inclusion of radiative corrections.

BR(KS+-())/ BR(KS00): The tag KL crash KS+- KL crash (30%): Cluster on barrel Eclu>100 MeV 0.17 < * < 0.28 ( KL velocity from cluster position and time) Tag bias

KS00   90% KS+-   60% At least 3 neutral clusters. N. clusters % <2 2 3 4 >4 1.3 8.6 33.2 56.6 0.3 At least 3 neutral clusters. Almost inclusive, low sensitivity to accidental clusters and inefficiencies.   90% KS+- Low BKG 2 TRKs from IP extrapolated to the EmC: 120 MeV < pTRK < 300 MeV   60%

KS+-() MC  MC  Efficiency corrected for the presence of the radiated photon. The total correction is 0.3%. ppg New MC implemented without any cutoff on the photon energy. N(Eg >50 MeV)/NTOT = 2.6x10-3

BR(KS+-())/ BR(KS00) Y2000: ~17 pb-1 PL B538 (2002) 0 - 2 - em=(47.8±2.8) Comparing with G.Colangelo et al. em=(-0.1±3.2) still in agreement with Cirigliano et al.

Conclusion Perspectives With ~17 pb-1 of data collected during the year 2000 KLOE measured: The BRs for 00 0 identifying 2440 and 800 events respectively. The mass spectra have been measured and unfolded. The estimate of the f0 and a0 coupling constants was obtained by performing a (model dependent) fit to these spectra. The ratio of BRs KS+-/00 correcting for the efficiency of the radiated photon. This measurement allows an accurate determination of 0-2-em which now is in agreement with the expected value. Perspectives Higher statistics collected during the years 2001 and 2002 allows: 2-dimensional mass spectra studies (Dalitz plots) The study of +- decays Reduction of systematics for BRs KS+-/00 to 0.1%.

Isospin mixing Isospin mixing  (  45) =(472) 7.00.7 6.10.6

Fit results M(f0)= 973  1 MeV g2(f0KK)/4 = 2.790.12 GeV2 g(f0KK)/g(f0)=4.00 0.14 g() = 0.0600.008 M(a0)= 984.8 MeV (FIXED) g2(a0KK)/4 = 0.400.04 GeV2 g(a0)/g(a0KK)=1.35 0.09

2001-2002 data ’00 data ’01+’02 data KLOE preliminary: ’01 + ’02 data

 +- Preliminary 2001-2002 data ~ 600000 events f0  