Status report on   f0  00 with 2001-2002 data S. Giovannella, S. Miscetti Effect of new generator ee  0  00g on 2000 data Surveying old analysis on the whole 2001-2002 data set: LVLAB = 447 pb–1 Normalization studies • Survey of luminosity • Survey of visible cross-section f   • Dependence of cross-sections on  s A starting road vs a Dalitz plot analysis 3rd KPW – Capri, 23-26 May 2003

Effect of the new ee  0 generator on 2000 data ( I ) generator now in GEANFI (P. Gauzzi)... not yet tried Old data set of 16 pb–1 No changes on data cuts Just weighting MC with new dN/dE shape [analytical description from Nucl. Phys. B 569 (2000), together with G. Isidori and L. Ingrosso] The discrepancy shown in PLB paper and in the supporting documentation (KN 178) disappeared!

Effect of the new ee  0 generator on 2000 data ( II ) Weighted ee  0 All other angular and mass distributions are in very good agreement s = (0.496 0.009stat) nb Consistent with the PLB value in within the conservative syst. error assigned: sPLB = (0.46  0.01  0.03) nb Old ee  0

Effect of the new ee  0 generator on 2000 data (III) The effect on dBR/dMpp is really small Total effect on BR is  1% BR = (1.07  0.03stat)10–4 Consistent with the PLB value BRPLB = (1.09  0.03  0.05)10–4 PLB New generator M00 (MeV)

 Old analysis on the whole 2001-2002 data set ( I ) Looking first at ee  0  00g w p0 g  qg TL The agreement is even better than in 2000!

Old analysis on the whole 2001-2002 data set ( II ) ee  0  00g 2002 scan data not used Runs with bad trigger conditions not yet removed Nwp = 108357 ± 376 s = (0.505 0.002stat) nb In agreement with 2000 data Excellent Data–MC agreement

Old analysis on the whole 2001-2002 data set ( III ) f  00g 2002 scan data not used Runs with bad trigger conditions not yet removed Minor distortions with respect to the published f0 shape Angular distributions OK Nppg = 60527 ± 317 BR = (0.963  0.005stat)10–4 ~ 10% lower than 2000

Comparing dN/dM Normalizing the new data set to the old luminosity, the 10% decrease of the BR is uniformly distributed along the spectrum Possible explanations for the discrepancy are: a problem on luminosity a loss of events a normalization problem 2001+2002 data 2000 data M00 (MeV)

Luminosity check To check the Luminosity we made the following: Use VLAB of the DATAREC version used when streaming (which can be different from the DST one) Plot N(f  7 )/L as a function of run number We found runs with: L = 0 |N7g-Nexp| / Nexp > 10 Around 3 pb-1 to be taken out from the sample N(f  7 )/L vs Run # 2001 2002

Dependence on s : (f    7 ) 1. The data set has been binned in groups of 100 keV vs s 2. The x-sec of f   as a function of s is reported 3. Only the bins with L > 500 nb-1 are shown 4. Same analysis efficiency for all s values  The s dependence follows nicely the theory  The peak x-sec is 3% lower than in 2000 data A first check on ECL streaming suggests a comparable loss due to out of time charged particles Visible x-section 20 % s in 2000 data

Dependence on s : (ee  0  00g) 1. Same analysis efficiency for all s values 2. Background subtraction not performed The process is clearly NOT RESONANT! Interference with f processes as shown from SND data [Nucl.Phys.B 569,2000] not visible, but this can be due to the residual background contamination Visible x-section (nb) s (MeV) s in 2000 data

Dependence on s : (f  00g) Visible x-section 1. Same analysis efficiency for all s values 2. Background subtraction not performed... We just select the Mpp> 700 MeV region, where the background contamination is smaller The process is clearly RESONANT! Shape follows roughly the theoretical x-section (nb) 5 % s (MeV) s in 2000 data

Looking forward to a Dalitz plot analysis The large statistics allows also to fit the Dalitz plot. In order to do this we should improve the photon pairing and have ana process independent 1. Only one kinematic fit with 4-momentum and ToF constraints 2. Same pairing for all processes, using only p0 masses (function of Egmin) 3. All events with p0p0g final state selected

Expected Dalitz-plot shapes for not p0p0 backgrounds

Expected Dalitz-plot shapes for p0p0 final states We intend to fit to the Dalitz plot taking into account any possible interference scheme between f  00, f  r0  00 and ee  0  00

Conclusions and outlook A large and clean data sample is available The new ee  0  00 simulation clarifies the doubts remaining at the end of 2000 analysis Different s behaviour of the visible x-sec for f  00, ee  0  00 and the normalization process f  h is observed. This suggests to: • perform analysis in bins of s • extract the BR (and the dBR/dMpp) fitting vs s Fit to the Dalitz plot will test any eventual interference scheme at low masses between VMD and S mediated processes