A. Dabrowski, June 08 2005 Ratio(ke3/pipi0) 1 Final Results Γ(Ke3)/ Γ(pipi0) Anne Dabrowski...

A. Dabrowski, June 08 2005

1

Ratio(ke3/pipi0)

Final Results

Γ(Ke3)/ Γ(pipi0)

Anne DabrowskiNorthwestern University

NA48/2 Collaboration Meeting08 June 2005

A. Dabrowski, June 08 2005Ratio(ke3/pipi0)

Outline

● Data & MC samples

● DATA / MC of final selection

● Particle ID efficiency

● Background

● Trigger Efficiency

● Correction to acceptance for ke3γ events outside dalitz plot in data

● Γ(Ke3)/ Γ(pipi0) result

– K+ / K-● Error analysis

– Statistical contributions– Systematic Errors, stability under variation of selection cuts, and

form factor (λ+)● Final result

– Consistent with ICHEP – but reduced systematic error● Conclusion


Data: ● Compact 7.2 & Database (database-2005-02-11) pass 5 Min bias 2003 (runs 15745,15746 and 15747)

– Bad burst

● Check: DCH,MBX,HODC,LKR,MUV,PMB and MNP33Current ne 0)● Reject 31 bursts for which momentum = 10.0 GeV ● Total number of bursts after bad burst rejection: 2244

– Alphas and betas

– Projectivity and Blue Field (Alan algorithm to remove phi dependence)

● Note: Result from August 2004 (ICHEP), used Compact 7.1 (no baseline energy correction)

MC Sample:– Ginsberg correction

– Constants from PDG 2004 ( λ + = 0.02780)

– Pi0 decays according to its branching ratio

– CMC005 corrections including corrections of May 9th 2005

– Result based on sample size of 10 M pipi0 and 8 M ke3

– Pipi0 mc has 0.438% pipi0g (IB) included in it at generation level

● Note Result from August 2004 (ICHEP) used cmc003 (improved DCH resolution in cmc005 among other changes) based on 2 M pipi0 and 2 M ke3. Dalitz and non dalitz decays were generated separately, pipi0 and pipi0g generated separately and ( PDG 2002 λ + = 0.02760) was used as input to MC

Data and MC samples


Common Selection for Ke3 and pipi0

● Track Section (no extra tracks allowed):

– 1 track after excluding Ghost-tracks

– Hodoscope time window (-17. 20. ns)

– Track quality > 0.8 CDA < 2.5 , Beta, alpha corrections from database

– x,y vertex (-1.8,1.8) cm , z charge vertex (-500,8000) cm

– Blue Field correction applied

● Pi0 Selection (extra gammas allowed for both)

– Energy of gamma (3, 65) GeV

– Separation between gammas > 10 cm

– Time difference between gammas (-5., 5.) ns

– Energy scale

– Projectivity correction

– Calculate neutral vertex for each pair of gammas, and choose gammas based on best difference between charge and neutral vertex

● Use this neutral vertex in the blue field routine to correct the slopes of the track (reason: phi dependence studies of Alan)

● August 2004 (ICHEP) result used the “charge” vertex reconstruction, and cut on pi0 mass as function of energy


Difference between Ke3Ke3 and pipi0pipi0 Selections

• Kaon Mass < 0.4772 or > 0.5102 (3 sigma from the mean)

• Momentum (5, 35) GeV

• PT track (0.01, 0.2) GeV

• Nu mass (-0.012, 0.012) GeV2

• Dist between track & gammas > 10 cm

• COM Track < 0.22 GeV

• COM pi0 < 0.27 GeV

• Mass (eπ0 ) < 0.425 GeV

• Particle ID for electrons:Particle ID for electrons:

• EOP > 0.95EOP > 0.95

• Kaon Mass (0.4772,0.5102) GeV

• Momentum (10, 50) GeV

• PT track < 0.215 GeV

• Nu mass (-0.0025, 0.001) GeV2

• Distance between track & gammas > 35 cm

• PT pi0 < 0.220 GeV

• E/P < 0.95


Pipi0 E/P < 0.95

Allow muons

Ke3 E/P > 0.95

Reject muons

Summary of particle ID used:


Ke3 Data / MC Momentum track

Once the momentum dependent E/P particle ID efficiency is taken into account distribution OK


Ke3 Data / MC Energy Pi0

Good energy calibration LKr


Ke3 Data / MC PT of pi0

sensitive to backgrounds and neutral reconstruction

seems OK


Ke3 Data / MC PT of track

sensitive to backgrounds seems OK


Ke3 Data/MC COM energy pi0

sensitive to backgrounds seems OK


Ke3 Data/MC COM energy track

sensitive to radiative corrections, Ginsberg implementation of radiative corrections OK!


Electron ID and Pion ID

• Selected electrons from tight ke3 selection and pions from tight pipi0 selection

• Used same data sample, and timing and fiducial cuts as in analysis

E/P > 0.95

for electronsGlobal efficiency (97.37 ± 0.09) %

E/P < 0.95

for pions Global efficiency (99.522 ± 0.001) %


Background contributions

Channel Background contributions

Pipi0(E/P<0.95)

Kmu3 (0.280±0.0058) % ▪Ke3 (0.0100±0.0015) %

Ke3

(E/P>0.95)

Reject muons

Pipi0 (0.0043 ± 0.0002) % Pipi0pi0 (0.0070 ±0.0003) %

Recall: electrons rejected by E/P in pipi0

pions rejected by E/P in Ke3

muons rejected in Ke3 only

Muons allowed

•Kmu3 background can be made negligable if we want to reject muons … see kmu3 talk.


Summary of acceptance and background

•Kmu3 background can be made negligable if we want to reject muons … see kmu3 talk.

Raw # Events Data

Raw Acc MC Acc*

Particle ID (E/P > 0.95 or E/P < 0.95)

Backgrounds

(Accbk*Br_bk)/

(AccS*BR_signal)%

Ke3 K+ 57,905 0.0751 ± 0.0001 0.0731 ± 0.0002 Pipi0 (when pion doesn’t decay) (0.0076 ± 0.0003)

Pipi0pi0 (when pion doesn’t decay) (0.0089 ± 0.0004)

ke3 K- 31,860 0.0747 ± 0.0001 0.0728 ± 0.0001 Pipi0 (when pion doesn’t decay) (0.0079 ± 0.0004 )

Pipi0pi0 (when pion doesn’t decay) (0.0095 ± 0.0005 )

Pipi0 K+ 473,616 0.1470 ± 0.0001 0.1463 ± 0.0001 Kmu3 (0.2803 ± 0.0058 )

Ke3 (0.0097 ± 0.0038)

Pipi0 K- 262,752 0.1467 ± 0.0001 0.1460 ± 0.0001 Kmu3 (0.2800 ± 0.0058)

Ke3 (0.0089 ± 0.0023)


Sources of background to ke3 K+/K-

Source ofBackground

Particle ID used

RAW MC acceptance no particle ID (%)

Acceptance* particle ID(%)

Background(Accbk*Br_bk)/(AccS*BR_signal) (%)

Pipi0+(note when pion

doesn’t decay)

E/P > 0.95

Muon veto

0.026810 ± 0.000518

0.000129 ± 0.000005

0.0076 ± 0.0003

Pipi0-(note when pion

doesn’t decay)

E/P > 0.95

Muon veto

0.025640 ± 0.000506

0.000132 ± 0.000007

0.0079 ± 0.0004

Pipi0pi0+(note when pion

doesn’t decay)

E/P > 0.95

Muon veto

0.3845 ± 0.0025 0.0018 ± 0.0001 0.0089 ± 0.0004

Pipi0pi0-(note when pion

doesn’t decay)

E/P > 0.95

Muon veto

0.3844 ± 0.0027 0.0019 ± 0.0001 0.0095 ± 0.0005


Sources of background pipi0 K+/K-

Source ofBackground

Particle ID used

Raw Acceptance

(%)

Acc*Particle ID (%)

Background(Accbk*Br_bk)/(AccS*BR_signal) (%)

Kmu3+ E/P < 0.95 0.2650 ± 0.0018 0.2650 ± 0.0018 0.2803 ± 0.0058

kmu3- E/P < 0.95 0.2641 ± 0.0018 0.2641 ± 0.0018 0.2800 ± 0.0058

Ke3+ E/P < 0.95 0.1947 ± 0.0016 0.0061 ± 0.0024 0.0097 ± 0.0038

Ke3- E/P < 0.95 0.1898 ± 0.0015 0.0056 ± 0.0014 0.0089 ± 0.0023


Calculating Γ(Ke3)/ Γ(pipi0)

)3(_)1()()3(__)3(

)(_)1()3()(__)(

)3(0

0)

0(

00

keeffTrigNKeeffIDPartKeAcc

effTrigKeNeffIDPartAcc

keback

back

data

data

We have all the ingredients for calculating the ratio …

Other corrections needed:

1. Trigger Efficiency

2. Correction to radiative decays

Pipi0γ mixed with pipi0 at generation level i.e. no further correction needed, correctly described by acceptance

Ke3γ Ginsberg correction, events only generated inside dalitz

plane. Need to correct acceptance for Ke3γ events in data lie outside dalitz plane


• Main Trigger Q1/4 • Min bias trigger for

trigger efficiency calculation Trackloose/100

channel K+ K-

pipi0 0.9987 ± 0.0002 0.9990 ± 0.0002

Ke3 0.9987 ± 0.0005 0.9983 ± 0.0008

kmu3 0.9986 ± 0.0006 0.9988 ± 0.0007

Trigger Efficiency K+/K-


• Events are only generated (and corrected for radiative events) inside the dalitz plane in ke3 MC. Hence we need to correct for the acceptance of ke3(γ) for events in the data which lie outside of the dalitz plane.

• Look at data events in v.s. out of dalitz plot• K+

– events selected out:152– Events selected in: 57550– Correction to Ke3+ acceptance:

1.0026±0.0002• K-

– Events selected out: 63– Events selected in: 31683– Correction to Ke3- acceptance:

1.0020±0.0004

• Assume that in the data, all events outside of the dalitz plot are ke3(γ) candidates, have not corrected this ratio yet for possible sources of background – but this is assumed small

Ke3γ events outside dalitz plane

Correction Ke3g K+/K-Ke3(γ) events inside dalitz plane


Ratio result Main Error contributions

Signal Normalization Systematics(MC,particle ID, background

subtraction, ke3g correction and trigger)

K+

Γ(Ke3)/Γ(pipi0)

0.24462 ± 0.00119

0.00102 0.00036 0.00049

Recall (~0.0011 in August 2004)

K-

Γ(Ke3)/Γ(pipi0)

0.24354 ± 0.00155

0.00136 0.00048 0.00057

• The error in the Br includes:– Statistical (signal and normalization)– Systematic

• Trigger efficiency• MC statistics (10 M pipi0 and 8 M ke3 of each charge)• Errors in particle ID efficiency (particle ID error bin by bin and propagated)• Errors due to background subtraction (including particle ID)

• No additional systematic errors due to kinematic cuts or form factor changes have been included YETYET in this table

Result Γ(Ke3)/ Γ(pipi0) K+/K-

Recall PDG 2004:

Br(Ke3) = 0.0487± 0.0006

Br(pipi0) = 0.2113 ± 0.0014

Fit Ratio(ke3/pipi0) = 0.230±0.004


Details of error contributions to Γ(Ke3)/ Γ(pipi0) K+/K-

Ratio of Γ(Ke3)/ Γ(pipi0) K+ K-

0.24462 ± 0.00118

0.24354 ± 0.00155

Statistics from signal (number of Ke3 events data) 0.00102 0.00136

Statistics from normalization (number of pipi0 events data) 0.00036 0.00048

Background subtraction 0.000017 0.000015

Trigger efficiency in pipi0 events 0.00005 0.00005

Trigger efficiency in ke3 events 0.00012 0.00020

Acceptance * Particle ID ke3 0.00042 0.00048

Acceptance * Particle ID pipi0 0.00020 0.00021

Error due to Ke3g correction for acceptance outside dalitz plot 0.00005 0.00010

Number of ke3 events data 57,905 31,860

Number of pipi0 events data 473,616 262,752


Summary of results:

Ratio result Main Error contributions

Signal Norm Systematics(MC,particle ID, background subtraction, ke3g

correction and trigger)

Ke3/pipi0 K+ 0.24462 ± 0.00119

0.00102 0.00036 0.00049

Ke3/pipi0 K- 0.24354 ± 0.00155

0.00136 0.00048 0.00057

(combined result) 0.24422 ± 0.00087 (stat) ± 0.00038 (sys)


Do we have any addition effects?


Χ2/ndf 12.25 / 11

Check Ratio of Ke3/ pipi0 as a function of momentum

K+ K-

Χ2/ndf 9.155 / 11

The ratio is stable as a function of momentum

(plotted in momentum region where ke3 and pipi0 events overlap)


Ke3 Data / MC Vertex

problem at high vertex, seems to be feature for K+ and K-

What is the source? Does it affect our result? …


Beam Tuning

DATA/MC for vertex in August was fine at high vertex (cmc003, and my beam tuning for special run)

Now use default cmc005, and beam tuning only done for assymetry runs (hypercompact)…

High vertex problem is an effect of insufficient beam tuning for our run.

But Does it affect our result? NO

Recall August 2004


Effects due to choice of vertex cut?

Analysis fuducial volume

(-500 , 8000) cm

K+ K-

Check I

(-1000 , 7000) cm

Result of fit doesn’t depend on fiducial region result insensitive to vertex



Analysis fuducial volume

(-500 , 8000) cm

K+ K-

Check II

(0 , 8000) cm





Cut varied Ratio result

Statistical Error

Systematic Error

Difference ratio ± correlated error

K+ Nominal (-500, 8000 cm)

0.24462 0.00108 0.00049

K- Nominal (-500, 8000 cm)

0.24354 0.00144 0.00057

( 0, 8000 cm) K+ 0.24438 0.00108 0.00049 -0.00024 ± 0.00017

( 0, 8000 cm) K- 0.24355 0.00146 0.00076 +0.00002 ± 0.00023

(-1000,8000 cm) K+ 0.24466 0.00108 0.00048 +0.00003 ± 0.00015

(-1000,8000 cm) K- 0.24366 0.00143 0.00057 +0.00012 ± 0.00020

(-500,7000 cm) K+ 0.24526 0.00112 0.00050 +0.00064 ± 0.00033

(-500,7000 cm) K- 0.24350 0.00150 0.00058 -0.00004 ± 0.00044

Error Assigned No effect no error


Cut varied Ratio Statistical Error

Systematic Error (MC,particle ID, background subtraction, ke3g correction and trigger)

Difference ratio ± correlated error

Default K+ (min g 3 Gev)

0.24462 0.00108 0.00049

( min g 5 GeV) 0.24502 0.00118 0.00051 +0.00040 ± 0.00056

Error Assigned K+ No effect no error assigned

Default K-(min g 3 GeV)

0.24354 0.00144 0.00057

( min g 5 GeV) 0.24277 0.00158 0.00059 -0.00077 ± 0.00076

Error Assigned K- No effect no error assigned

Energy γ 2

Energy γ 1

Low neutral energy scaleRecall, in August checks shift in ratio 0.00095 due to final calibration missing in compact 7.1


Varying the form factor λ+ K+/K-

Form factor model

Ratio result (K+)

± 0.00108(stat) for all K+ numbers

Difference Ratio result (K-)

± 0.00144 (stat) for all K- numbers

Difference

0.0278 K +

(PDG 2004: 0.0278±0.0070

)

0.24462 ± 0.00049 (sys from MC)

0.24354 ± 0.00057 (sys from MC)

0.0271 K+

(PDG 2004 –1 σ)

0.24590 ± 0.00058 (sys from MC)

+0.00127 0.24351 ± 0.00065 (sys from MC)

-0.00002

0.0285 K+

(PDG 2004 +1 σ)

0.24511 ± 0.00058 (sys from MC)

+0.00049 0.24318 ± 0.00065 (sys from MC)

-0.00036

Systematic to be added ± 0.00062

This procedure was done with uncorrelated montecarlo.

Based on the statistics, one cannot draw a conclusion. Error assigned the error due to the average MC statistics ± 0.00062

In future, I will redo by using the default MC, and re-weightingre-weighting each events based on the ratio of the form factors.

± 0.00062 should be a conservative estimate for now, until I re-do


Momentum No systematic effect seen

Vertex Cut No systematic effect seen

Min Energy Cut No systematic effect seen

Parameterization of form factor ± 0.00062

Additional Systematic Error ± 0.00062

Total Error systematic error K+ ± 0.00072

Total Error systematic error K- ± 0.00079

Summary Systematic checks


Details of error contributions Γ(Ke3) / Γ(pipi0)

Ratio of Γ(Ke3) / Γ(pipi0) K+ K-

0.24462 ± 0.00134

0.24354 ±0.00164

Statistics from signal (number of Ke3 events data) 0.00102 0.00136

Statistics from normalization (number of pipi0 events data) 0.00036 0.00048

Total Statistical Error 0.00118 0.00144

Background subtraction 0.000017 0.000015

Trigger efficiency in pipi0 events 0.00005 0.00005

Trigger efficiency in ke3 events 0.00012 0.00020

Acceptance * Particle ID ke3 0.00042 0.00048

Acceptance * Particle ID pipi0 0.00020 0.00021

Error due to Ke3g correction for acceptance outside dalitz plot 0.00005 0.00010

Total systematic error (excluding Lambda) 0.00049 0.00057

Error due to Lambda 0.00062 0.00062


Summary of results

K+ Γ(Ke3)/ Γ(pipi0) = 0.2446 ± 0.0010 (signal) ± 0.0004 (norm) ± 0.0005 (sys) ± 0.0006 (form factor)

K- Γ(ke3)/ Γ(pipi0) = 0.2435 ± 0.0014 (signal) ± 0.0005 (norm) ± 0.0006 (sys) ± 0.0006 (form factor)

K± Γ(ke3)/ Γ(pipi0) = 0.2442 ± 0.0009 (stat) ± 0.0004 (sys) ± 0.0006 (form factor)

Result dominated by statistics not systematics!Recall ICHEP:

Γ(ke3)/ Γ(pipi0) = 0.2433 +-0.0009 (stat) +-0.0028 (sys)

We are completely consistent!

A. Dabrowski, June 08 2005 Ratio(ke3/pipi0) 1 Final Results Γ(Ke3)/ Γ(pipi0) Anne Dabrowski...

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