1. Status report on   f0  00
with data
S. Giovannella, S. Miscetti
Effect of new generator ee  0  00g on 2000 data
Surveying old analysis on the whole 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, May 2003

2. 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!

3. 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

4. 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)

5.  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!

6. 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 = ± 376
s = (0.505 0.002stat) nb
In agreement with 2000 data
Excellent Data–MC
agreement

7. 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 = ± 317
BR = (0.963  0.005stat)10–4
~ 10% lower than 2000

8. 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
data
2000 data
M00 (MeV)

9. 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

10. 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

11. 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

12. 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

13. 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

14. Expected Dalitz-plot shapes for not p0p0 backgrounds

15. 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

16. 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 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