(1) Efficiency (2) Fitting function revised (3) Extraction of the signal (4) Conclusions
-
Upload
nolan-coffey -
Category
Documents
-
view
14 -
download
0
description
Transcript of (1) Efficiency (2) Fitting function revised (3) Extraction of the signal (4) Conclusions
(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”
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