Status of the Measurement of the f meson parameters
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Transcript of Status of the Measurement of the f meson parameters
Status of the Measurement
of the meson parameters
M. Dreucci for fitter WG
KLOE General meeting 19-12-2002
M. Antonelli, C. Bini, F. Bossi, P. Branchini, M.
Dreucci,
C. Gatti, S. Giovannella, S. Miscetti, M. Palutan,
L. Passalacqua, B. Sciascia, T. Spadaro
• theoretical cross sections
• data samples and MC simulation
• measurement of DANE parameters
• status of cross section measurements
• status of lineshape fits
• measurement of leptonic widths
• conclusions
Introduction
;Γm)m(s
Γmσ(s)σ 2
φ2φ
22φ
2φ
2φ0
XφeeXφee
2φ
0Xφee m
X))B(φeeB(φ12πσ
• Born cross section:
Peak cross section
+ corrections (phase space + contributions from )
parameters: mass, total width, peak cross sections
Main decays modes
K+K– 49.2%KLKS 33.7% 15.5% 1.3%
the measurement of the partial widths requires the knowledge of e+e- width (no direct measurement available)
leptonic modes
e+e– 3.0 x 10-3
+– 2.9 x 10-3
Cross sections
Born cross sections (b)
K+K–
KLKS
W(MeV)
Born cross sectionsincluding contributionsfrom exchange*
Up to 10% effects parameters can be fixed to PDGvalues with no loss ofaccuracy in measuringthe parameters
*[ N.N. Achasov et. al. Yad. Fiz. 54, 1097 (1991)]
Cross sections 2
Initial state radiation correction
Standard method:
Radiator
• Radiator from Nicrosini et al. 2nd DAFNE handbook
• numerical integration with VEGAS
• Kuraev-Fadin radiator used for comparison (no differences)
• other integration codes used: REMT + home developed one
sth
Data samples and MC simulationdata sample
MC simulation
2001 scan: 0.5 pb-1 W[1015:1025] 11 points ~50 nb-1
each2002: 2 high statistics (7+8 pb-1) energy points @ m/2 + ~ 7 pb-1 at peak
(s) + H(s,s’) + beam energy spread+ radiation from both beams
KL
KS
Careful treatment ofISR effects in the generator radiative
returnsto meson
KS-KL invariant mass (MeV/c2)
W=1025 MeV
e+e- invariant mass (MeV/c2)
Measurement of DANE parameters
Luminosity: from large angle bhabha at % level
corrected for bhabha(W)
center-of-mass energy beam energy spread
absolute calibration @ ~2x10-4
linearity @ ~ 10-5
using redondat W measurement in KS->+- KL crash events
Status of cross section measurements
K+K– selection
All analyses well advanced: refinements in progress expected accuracies at % level for each channel
Use event symmetry K->0 double tag method
Double tagsingle tag
Track momentum in Kaon rest frame (MeV)
selectionKLKS
Based on KL crash algorithm
absolute KL crashefficiency from KS->00 KL side not biasedPolar angle distribution notaltered
selection
Selection based on kinematics
Missing massfrom measuredmomenta + W
M0 from
cos (angle) in0 rest frame
Preliminary measurements
(nb)
W(MeV)
1017 1019.5 1022
K+K– 801± 30 1710 ± 32
855 ± 26
KLKS 423 ± 10 956 ± 21 476 ± 11
270 ± 7 368 ± 9 160 ± 4
20.9 ± 0.5
40.2 ± 1.0
17.7 ± 0.4
Preliminary lineshape fits
Results of 4 independent fits
0
(nb)
M1019(MeV)
(MeV)
K+K– 2363±51 0.46±0.07
4.15±0.10
KLKS1350±33 0.50±0.0
64.05±0.1
2
538 ± 16 0.22±0.05
4.6 ±0.2
58±2 0.40±0.05
4.10±0.13
Direct term in set to 0
BeS overestimated? (default 575 KeV)
Status of lineshape fits 2
Good agrement in M , values for K+K–, KLKS , problems in fitting ( add direct terms)But efficiency vs effective W’/W cut not evaluated
W’(MeV)
Radiative return to
Status of lineshape fits 3
Combined fit: not included fit with in + direct term tried….
0 SND
(nb)
0
(nb)
M1019(MeV)
(MeV)
K+K– 1968±20 2360±35
0.46±0.02
4.13±0.01
KLKS1454 ±12
1350±18
53 ±2 57±1
Contribution to e+e- e+e- process
Measurement of ee
Necessary for themesurement of partial width 2
φ2φ
Xee0Xφee m
12πσ
Check of Xφ measurement invisible
Sensitivity to new physics? Light + strong coupling objects ( Axions, g ) ~
e+e- e+e- forward backward asymmetry
• AFB :
enhanced sensitivity to ee with respect to ee
AFB
W (MeV)
Some experimental advantages:•Luminosity not needed•Partial cancellations (eff, bkg, syst.)
sensitivity to ee
Preliminary results: full data sample
AFB relative accuracy at 8x10-
5
ee at ~2.3%
Still to do: more MC Systematics
W (MeV)
AF
Bee = 1.30 0.03 keV
Expected accuracy
on measurement
~ 1.5%
Perspective for the measurement of
Check consistency with ee (just QED)
Combine the two measurements
W (MeV)
(nb)
Conclusions
The status of the analyses of the lineshapein different chennels is well advanced: First preliminary results for all channels
M and in agreement within channels but for seems to be too small (investigate on BeS) charged kaon cross section ~18% higher wrt SND ee at 2.3% value in agreement with PDG( came soon )
We have just started…..