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

Initial state radiation correction

• up to 30% correction

W (MeV)

KLKS

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

selection Very clear signatures agreement within different channels

->30,

->

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:

(nb)

W(MeV)

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

Status of lineshape fits: K+K-

(nb)

W(MeV)

Status of lineshape fits: KSKL

(nb)

W(MeV)

Status of lineshape fits 4:

(nb)

W(MeV)

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…..