(1) Efficiency(2) Fitting function revised(3) Extraction of the signal(4) Conclusions

C.Bini , S.Ventura

Search for f0(980) in final states with the photonat large angle

Roma1 13/11/2003

The data sample: sample Lumin. (pb-1)

#events Rate

(nb)

2001 115 221178 1.923

2002 234 454412 1.942

total 349 675590 1.936

Events with: 2 tracks from I.R. 1 photon at > 45o

M() spectrum f0 signal

Red = 2001 dataBlue = 2002 dataNormalized to luminosity

FILFO efficiency:

from afilfo stream7 pb-1 2001 data (19057-21889)dependence on mach. bck to check

Cosmic Veto efficiency:

from 2001 and 2002 full datasamples (compatible)

M() (MeV)

Pion identification efficiency

Method: Control sample of ; Kinematic selection only;

Evaluate: Prob( track calorimeter

AND likelihood pion ) as function of pt and

comparison + vs -

Data sample: ~2 pb-1 from 2001 sample ~2 pb-1 from 2002 sample

Comparison with MC: differences up to ~5% (MC has lower efficiency)

40<<50 50<<60

60<<70 70<<90

Total efficiency:

MC stream ppphvlag (ISR+FSR) Sample size ~~ data sample size

All selection chain apart from: Filfo Vetocos TCA+Likelihood (taken from data)

Corrections from: tracking efficiency photon efficiency

(M) polynomial parametrisation

photon requirement

Vetocos effect

acceptance loss

Fitting function

ISR + FSR + f0 + interf(f0,FSR).

Background (ISR and FSR): Achasov et al. parametrisation + corrections based on EVA MC due to the “collinear radiation”

The function depends on: M( ), ( ), M( ), ( ), M( ’ ), ( ’ ) ,

ISR

FSR

1

)'(1

)(1)(BW

BWBW

FF

Comparison function vs Geanfi: ok ( if same parameters )

Signal Shape: Found a “bug” [extra 1/] in the interf. Term now Achasov curves are well reproduced analysis curves also reproduced

Data vs. expected background:

Absolute comparison of data spectrumwith the expected background

Background parameters from: Aleph 1997 CMD-2 2001 KLOE (s.a.) 2001

No additional parameter

The accuracy on is too poor to allow an absolute subtraction

A fit is needed including somebackground parameters as freeparameters

(or take parameters from smallangle analysis)

CMD-2 Aleph

Fit with interf. + 2 =765 / 483 d.o.f. Fit with no interf. 2 =688 / 483 d.o.f.

The fit7 free parameters:BCK: M( ), ( ), , signal: g2

f0KK/4, R , M(f0)3 interference schemes: +, no, -

Fit with interf. - 2 =780 / 483 d.o.f.

Int + No Int Int -

M() (MeV) 774.8 776.0 777.5

() (MeV) 144.2 145.7 150.0

(x10-2) 0.187 0.182 0.166

-0.085 -0.089 -0.102

g2f0KK/4 0.63 1.52 1.39

R 6.36 7.39 2.53

M(f0) 994.7 980.7 937.6

2 / 483 765 688 780

2 / 138 (only f0 region)

248 213 252

Fit results

Best fit = No int:better 2

better parameters(PDG M(f0)=980 10)

Comparison between subtracted spectra

The shape of the subtracted spectrum is ~ independent on the

background parameters

Why the 2 are too large ?

Plot of the residuals for the best fit (No Int)

A residual “oscillation” can be due to:efficiencybackground parametrization

The effect is “small” ~ 1%

Solid = f0 spectrumDashed = f0 spectrum (KLOE published)Dotted = f0 spectrum x 2

Comparison of KLOE results on and

At “first view” the 2 analyses give not consistent results:

(1) Same line-shape expected but: narrow peak very broad tail different parameters;

(2) BR is ~ 50% than expected;

Fit(A) no

Fit(B)

Fit no int

g2f0KK/4

(GeV2)

1.29 0.14

2.79 0.12

1.5 0.2

R 3.22 0.29

4.00 0.14

7.4 0.5

M(f0)

(MeV)

962 4 973 1 980 1

BR (x10-4) 1.11 0.06

1.49 0.07

0.97 0.04

Comparison of parameters: preliminary estimates

Fit-no

Fit -

Upper limit on

P and CP violating decay:CP(in)=- ; CP(out)=+Standard Model prediction BR ~ 10-27 10-24

(Shabalin DPH 1995)

No peak found at mass

Rough estimate of an upper limit:

L = 350 pb-1 x BR() = 40000 pb (total) = 30% x 60%

BR < 2. x 10-5

PDG: < 3.3 x 10-4 (CMD-2)

Expected signal shape:Centered at 547.3Width = 1.5 MeV

Conclusions

We have “refined” our efficiency evaluation found and fixed few “bugs” in the fitting function

The fit now works quite well and indicates: best fit for no interference a narrow f0 peak [ (f0 +-) = 47 MeV ] a large value of R (>7) [ f0 strongly coupled to kaons] BR = 1x10-4

Significant “unconsistency” with analysis

To do still: some more checks on efficiency; refinements of the fit (understand residual plot); estimate of uncertainties (dominated by the subtraction of the background)

A Memo is “almost ready”

solid: f0 with NO intdashed: f0 if – intdotted: f0 if + int

CMD_2CMD_2 has studied the charged channel f has studied the charged channel f00

With a sample of 9.24 pbWith a sample of 9.24 pb-1-1 at the at the pick pick

dd/dE/dE spectrum spectrum

Cross-section versus E.c.mCross-section versus E.c.m