Status of the measurement of

the main KL

branching ratios

M. Antonelli, M. Dreucci, E. De Lucia,C. Gatti, M. Moulson, T. Spadaro

CP meeting 02-2003

Tag bias

Main bias is expected from trigger

require trigger from ks pions:

clusters connected to fired trigger sector no other cluster in “ks sectors” (avoid overlaps)

no splitted pion tracks (T2CL asso. quality) + ks direction far from beam line (cos()>0.9)

Ks selection: Rt<10cm ;|z|<20 cm |m-mK|<5 MeV; |p*-p*K|<10 MeV

63%

39%

25%

20%

Tag bias: MC results

Relative KS +- efficiency for various KL process

KL eKL

KL +-0

KL 000

KL All

out FVCrash included

63% standard

39% Ks trigger

25% + overlaps

20% + tracks q. Ks dir.

KLtag

in FV

+/- 1%

Tracking + Vertex efficiency

Double tag method ( from KL analysis)

KS

Conditional efficiency N2/N1 from data

Tag definition: sliding cuts on DIST and SWLEN

x

dist

swlen

Rt (cm) Rt (cm)

swlen (cm)dist (cm)

Data-MC comparison (2002 data)

DATA MC

1.06 in 2000 P*(MeV)

mc

dt

Rt(cm)

Data-MC comparison (2002 data)

DATA MC

mc

dt

Rt(cm)

Vertex efficiency (2002 data)

DATA MC

mc

dt

Signal counting: Kinematics

Several variables tried: Pmiss-Emiss with mass hypothesis() giving min |Pmi.-Emi.|

Fit to expected MC distributions 3 parameters

DATA MC

KL +-

Fixed to expectedcontribution

norm1.5

Pmiss-Emiss (MeV)

KL e

KL

KL +-0

Signals separation

Correlation matrix: ke3 k3 3 1. -0.1 -0.02 1. -0.03 1.

Signal counting: Kinematics

DATA MC

Pmiss-Emiss (MeV)

Preliminary results:

<> track+vertex 0.508 0.485 0.338

KL e KL KL +-0

Total number of tag: 11707500 (L~ 78pb-1) run# 25***

Fit Results: 581245 396713 129445 errors* 2963 2521 1420

Branching 0.3840.002 0.2710.002 0.1320.002 PDG 0.3880.003 0.2720.002 0.1260.002(s=1.7)

<> FV 0.255

C=i/tot (tag) 0.995 1.01 0.992

C (1-C)/2

*Dominated by MC statistcs (~6.5 pb-1)

ConclusionsO order result ready: almost unbiased KL tag tracking efficiency ~ agreement with MC shapes not that bad results in agreement with PDG To do list:

Include KL30 (sum Branching ratios to 1 up to 10-3) Checks on KLtag bias: compare data MC agreement for different KL tags* compare with KS-> 20

Track + Vertex : use new vertex routine some mc-dt disagreement for resolutions (probably fine with new MC ) Increase MC statistic (statistical error, tag bias studies, tracking eff. Studies…..)* Agreement at <1%(MC stat.) level (from morning studies)