measurement of the branching ratio of the k + decay update e. de lucia, r. versaci

Measurement of the

branching ratio of

the K+ decay

UpdateE. De Lucia, R. Versaci

Home works (Hausaufgabe)

1.FILFO correction 2.T3 FILTER correction 3.Efficiency checks 4.Time stability 5.Trigger with not overlapping sectors

Home works (Hausaufgabe)

1.FILFO correction 2.T3 FILTER correction 3.Efficiency checks 4.Time stability 5.Trigger with not overlapping sectors

BR (K+ ) = 0.6357 ± 0.0009 (stat.)

BR (K+ ) = 0.6366 ± 0.0009 (stat.) Trig over

Trig no over

WORK IN PROGRESS

WORK IN PROGRESS

OLD SLIDESOLD SLIDES

T3FILTER correction (trig no over)Using the whole DATA sample:

13

13

6464

FLAGTTAGTAG

FLAGTSIGSIG

TAG

SIG

xNNxNN

NN

BR(K()) BR x CT3

CT3 = 0.9994 0.0003

BRT3FILTER negligible O(10-6)

T3FILTER correction (trig over)Using the whole DATA sample:

13

13

6464

FLAGTTAGTAG

FLAGTSIGSIG

TAG

SIG

xNNxNN

NN

BR(K()) BR x CT3

CT3 = 0.9995 0.0003

BRT3FILTER negligible O(10-6)

FILFO correction

SIGTAG

TAGFILFOC

11

iFILFO

iAFILFO

iAFILFO

i NNN

CFILFO = 1.00006 0.00032 (DATA)CFILFO = 0.99967 0.00015 (MC)

Using the same set of runs for DATA and MC :

In agreement within the errorsIn agreement within the errors

BRFILFO = 3x10-4BR(K()) BR x CFILFO

Efficiency evaluationOn the sample selected using ECAL we look for a signal event

( i.e. K+ reconstructed in the DC FV)using the same event selection used for the signal sample

KTAG

K

NK

NtagKTAG

=

NK

Ntag

Efficiency checks (I)Remember memo #3x10Remember memo #3x1022

The systematic uncertainties on the efficiency are:

1) Low energy cut (LEC)

BR = 5 x 10-4

(from 10 to 40 MeV)

2) High energy cut (HEC)

BR = 2 x 10-4

(from 70 to 90 MeV)

standard cuts: LEC = 20 MeV HEC = 80 MeV pollution of the EMC sample 1.2%

p*(MeV/c)

Calorimeter sampleCalorimeter sample only true KTrue K

Efficiency checks (II): pollution/compensation

p*(MeV/c)

LEC = 40 MeV HEC = 90 MeV

76% generated True K()pollution 3 %

Calorimeter sampleCalorimeter sample only true KTrue K

LEC = 10 MeV HEC = 90 MeV

25% generatedTrue K()pollution 0.7 %

Efficiency checks (III)Changing the cuts for the selection of the EMC sample we observe the following maximal variations:

DATA efficiency 0 0.3074 (2) 0.3169 (3) 0 3%

Pollution in EMC sample 0.7 % 3 %

Correction (CORR) 0.98008 1.0085 CORR 3%

For each EMC sample:1. evaluate the MC corrections CORR 2. apply CORR to the efficiency 0 measured on EMC DATA sample = 0 x CORR

Then the initial 0 3% becomes O(10-4) BR 5 x 10-4

Changing EMC sample :Changing EMC sample :Pollution and compensation have different Pollution and compensation have different behavioursbehaviours !!!!!!!!

Efficiency checks (IV): Double ratio MC/Data

The double ratio stability is related to our sensitivity to changes The double ratio stability is related to our sensitivity to changes of the pollution/compensation effectsof the pollution/compensation effects

DATA(set2)DATA(set1)

MC(set2)MC(set1)

N.B.set1 and set2 appliedon independent DATA samples

set1 : LEC = 20 MeV HEC = 80 MeV


2 = 90.33/85A0 = 1.007 0.008

Efficiency checks (IV): Double ratio MC/Data

The double ratio stability is related to our sensitivity to changes The double ratio stability is related to our sensitivity to changes of the pollution/compensation effectsof the pollution/compensation effects

DATA(set2)DATA(set1)

MC(set2)MC(set1)

N.B.set1 and set2 appliedon independent DATA samples



2 = 85.43/85A0 = 0.9011 0.007

Checking various distributionsfor the kaonfor the kaon

tof (ns)

KINE

Calorimeter sampleTrue K

Checking various distributionsfor the kaonfor the kaon

pK (MeV/c)pK (MeV/c)

KINEREC


Checking various distributionsfor the decay vtxfor the decay vtx

Rxyz (cm)Rxy (cm)

KINE

KINE

Kaon interacting withthe inner DC wall

Kaon interacting withthe inner DC wall


Checking various distributionsfor the secondaryfor the secondary

pLAB(MeV/c)

KINE

pLAB(MeV/c)

KINEREC

Kaon stopped in the inner DC wall,Decay at rest then Plab = 236 MeV



Checking various distributions

for the secondaryfor the secondary

pLAB(MeV/c)

MC-Data comparison

DATAMC



cos

RECKINE

cos



pT(MeV/c)

L(cm)

REC

REC


The “missed” time stability plot

BR K+ = 0.6366 0.0009 (stat.) 0.0012 (syst.)

PDG fit = 0.6343

Chiang = 0.6324

Results

Vus = 0.2223 (25)

Results

BR K+ = 0.6366 0.0009 (stat.) 0.0012 (syst.)

fK /f =1.210±0.014(MILC Coll. hep-lat/0407028)

Following the method from Marcianohep-ph/0406324 :

Vud=0.9740±0.0005 (superallowed -decays)

measurement of the branching ratio of the k + decay update e. de lucia, r. versaci

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