anne dabrowski northwestern university na48/2 semileptonics meeting 22 nd february 2005 update kmu3...

Anne DabrowskiNorthwestern University

NA48/2 Semileptonics Meeting22nd February 2005

Update Kmu3 Branching Ratio measurement

A. Dabrowski, February 22 2005

Test 2 Particle ID2 Particle ID muon strategies:

1) Muon Veto as Muon ID • Check muon veto status 1 or 2• Timing association of 2ns for track between muon

veto and hodoscope time

2) LKR and HAC as Muon ID● Use the mip signal in calorimeters:● LKR < 1.5 GeV and HAC < 5 GeV for the cluster

associated to the tracks..

Requirement for signal and normalisation:

● 1 track and 1 pi0● Kinematic cuts using LKR and DCH

Strategy: Measure Kmu3 Br normalised to pipi0


● Compact 7.2 & Database pass 5 Min bias 2003 (15745,15746 and 15747)

– Alignment– E-baseline correction– Bad burst– Alphas and betas– Projectivity and Blue Field

● MC Sample:– Ginsberg correction– DCH resolution correction to MC

– Energy scale correction to MC (not in presented Dec 2004 numbers)

Data Sample


Simple selection wanted....Common for Kmu3 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 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– Pi0 mass cuts at 3 sigma and depends on pi0 energy– Projectivity correction– Energy scale


Difference between Kmu3 and Pipi0 selection

● Kaon Mass (assuming pi) <0.475 or >0.515

GeV

● Mom (10, 40) GeV

● PT track (0.0, 0.2) GeV

● Nu mass (-0.01, 0.01) GeV2

● Dist between track & gammas > 10 cm

● Energy pi0 < 40 GeV

● COM pi0 < 0.24 GeV

● COM Track < 0.23 GeV

● Mass of mu pi0 < 0.445 GeV

● Particle ID for muons (2 methods used)Particle ID for muons (2 methods used)

● Kaon Mass (0.475,0.515) GeV

● Mom (10, 50) GeV

● PT track < 0.215

● Nu mass (-0.0025, 0.001) GeV2

● Distance between track & gammas > 35 cm

● PT pi0 < 0.220

● E/P < 0.95

● Use muon rejection only when the Use muon rejection only when the muon veto in used in the Kmu3 muon veto in used in the Kmu3 analysis. analysis.


Summary of particle ID used:


Method 1 Method 2Pipi0 E/P <

0.95! MUV

Pipi0 E/P < 0.95

Kmu3 MUV Kmu3

(Lkr < 1.5 GeV )& (HAC < 5.0 GeV)

Main Effort since December: Understanding backgroundUnderstanding background

Method 1 Method 2

Pipi0(E/P<0.95)!MUV

Kmu3Ke3Pipi0dk▪

Pipi0(E/P<0.95)

*Kmu3Ke3

Kmu3MUV

Pipi0dk▪Pipi0pi0dk ▪Pipi0Pipi0pi0

Kmu3(LKr<1.5)GeV & (HAC < 5.GeV)

Pipi0dk ▪Pipi0pi0dk ▪*Pipi0*Pipi0pi0pipi0g

*backgrounds considered in December 2004 meeting

▪dk refers to events where the pion has decayed into a muon

Backgrounds are separated into when the pion does or does not decay because the particle ID efficiencies for muons and pions are treated separately.

Pion ID efficiency E/P < 0.95 (common to both analysis

methods)


• Pion ID efficiency calculated using pipi0 sample from min bias run.

• Kinematic cuts (as in my selection)– Muon veto requirement

to reject muons– But have a tighter Kaon

mass cut for this sample (0.485, 0.505 GeV).

• Event Timing and Fiducial cuts as in Kmu3 Br analysis

Muon ID efficiency E/P < 0.95 (common to both analysis methods when subtracting muon

background in pipi0)


• Muon EOP ID efficiency calculated using Kμ2 sample from min bias run; – Use only kinematics to

select muons• Kinematic cuts Momentum

(10,40)– Min PT of 0.15 GeV– Banana PT vs P cut (Luca)– Mass ν2 (-0.02;0.01) GeV2


• Efficiency between 0.99997 and 1.0

Muon ID using the Muon Veto

• Muon ID efficiency calculated using Kμ2 sample from min bias run; – check status 1 or 2 and 2 ns

between hod time and muon veto time

• Kinematic cuts Momentum (10,40)– Min PT of 0.15 GeV– Banana PT vs P cut (Luca)– Mass ν2 (-0.02;0.01) GeV2


• Efficiency between 0.997 and 0.998

Method 1:Method 1:


Correction Factor due to pion not

decaying in MC after LKR

• IN MC 6.4m decay volume, particle decay not simulated (LKr to MUV)

• Apply a correction to MC acceptance of pipi0, momentum dependent

• Inefficiency of 0.2% for MUV-ID taken into account

Method 1:Method 1:


The efficiency of pion decay in pipi0 in data and MC (max z is zlkr in MC)

Probability of a pion NOT decaying between LKr and MUV

Muon Veto ID

Acceptance of signal and normalisation

channel Raw Acceptance from MC

Acceptance * particle ID

Final acceptance(including correction factor due to decay between lkr and muon veto)

kmu3 0.1052±0.0002 0.1047±0.0002(muon veto ID)

0.1047±0.0002No correction needed

Pipi0 0.1541±0.0001(when the pion has not decayed)

0.1531±0.0001(E/P < 0.95)(excluding μ rejection efficiency)

0.1521±0.0001Correction due to MC decay bin by bin

Integrated value including μ -ID inefficiency overall correction 6.5‰

Method 1:Method 1:


Normalization

Signal

Sources of Background to kmu3+

Source ofBackground

Particle ID used

RAW MC acceptance no particle ID

Acceptance*particle ID

Acceptance*Particle ID*correction

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

Pipi0dk(when pion

decays before the lkr)

Muon veto ID

(2.05+-0.05)x10-4 (2.04+-0.05)x10-4 No correction needed

(1.26±0.04)x10-2

Pipi0(when pion

decays after the lkr)

Muon veto ID

(2.84+-0.05)x10-4 (2.83+-0.05)x10-4 (2.2+-0.1)x10-6

(multiply accepted events by the probability of pion decay after lkr)

(1.35+0.04)x10-4

Pipi0pi0dk(when the pion

decays before the lkr)

Muon veto ID

(2.22+-0.07)x10-4 (2.21+-0.07)x10-4 No correction needed

(1.11±0.05)x10-3

Pipi0pi0(when pion

decays after the lkr)

Muon veto ID

(3.56+-0.03)x10-3 (3.56+-0.03)x10-3 (2.52+-0.07)x10-5

(multiply accepted events by the probability of pion decay after lkr)

(1.26+-0.04)x10-4

Method 1:Method 1:


Sources of Background to pipi0+Source ofBackground

Particle ID used

Raw Acceptance

Acc*Particle ID Need for a correction to MC decay?


Pipi0dk (decay before the lkr)

E/P < 0.95!MUV

(2.11+0.01)x10-3 (1.6+-0.1)x10-5 no (1.07+-0.08)x10-4

kmu3 E/P < 0.95!MUV

(3.27+0.04)x10-3 (1.3+-0.2)x10-6 no (1.3+-0.1)x10-5

ke3 E/P < 0.95!MUV

(2.33±0.03)x10-3 (6.7±0.4)x10-5 no (1.01±0.06)x10-4

Pipi0 (decay after lkr)

E/P < 0.95!MUV

0.1541±0.0001 (4.38+-0.05)x10-4

* Yes (2.32+-0.04)x10-6

(1.52+-0.03)x10-5

Method 1:Method 1:


*takes into account the decay probability for pions between the Lkr and MUV from DATA

Muon ID signals using the LKR and HAC

• Cuts chosen– LKR < 1.5 GeV and

HAC < 5 GeV• Muon sample using Kμ2

events from min bias run.

• Kinematic cuts– Momentum (10,40)– Banana PT vs P cut– Mass ν2 (-0.02;0.01) GeV2

– Muon Veto requested• Event Timing and Fiducial

cuts as in Kmu3 Br analysis

Method 2:Method 2:


Muon ID efficiency using the LKR and HACMethod 2:Method 2:

• Muon ID requirement:– LKR (cluster<1.5

GeV) and HAC (cluster<5.0 GeV)

– Muon ID is energy dependent with max ~0.987

– Analysis done bin by bin in momentum


Recall Method 1 eff at 0.998

Pion mis-identification as muons

using the LKR and HAC

• Pions can be to mis-identified as muons

– Need a pion mis-identification probability, and background subtraction.

• Sample used for calculating the mis-identification probability– Pions from my standard pipi0

selection, with the muon Veto requirement.

– Plus a tighter Kaon mass cut for this sample (0.485, 0.505 GeV).

– Event Timing and Fiducial cuts as in Kmu3 Br analysis

Method 2:Method 2:


Signal

LKR & HAC muon ID

Acceptance of signal and normalisation

channel Acceptance from MC

Acceptance * particle ID

Final acceptance(including correction factor due to decay between lkr and hac)

kmu3 0.1052±0.0002 0.1019±0.0002(lkr & hac muon ID)

0.1019±0.0002No correction factor needed

Pipi0 0.1562±0.0001No μ -ID

0.1553±0.0001(E/P < 0.95)

0.1553±0.0001No correction factor needed

Method 2:Method 2:


Normalization

Sources of Background to kmu3+Source of Background

Particle ID used Raw MC acceptance

MC acceptance* particle ID

MC Acc* particle ID * decay factor


Pipi0dk(pion decays

before the lkr)

Muon ID (lkr hac) (2.05±0.05)x10-4 (1.97±0.04)x10-4 No factor needed (1.24±0.03)x10-2

Pipi0 (pion decays

after the lkr)

Muon ID (lkr hac) (2.84±0.05)x10-4 (2.75±0.05)x10-4 Yes, multiply by probability of decay

(8.0±0.1)x10-7

(5.1± 0.1.)x10-5

Pipi0 (pion doesn’t

decay)

MuonID (lkr hac)(mis ID-prob pion as muon)

(2.84±0.05)x10-4 (2.5±0.1) x10-5 Yes, suppress by probability of not decaying

(2.5±0.1) x10-5

(1.6±0.5)x10-3

Pipi0pi0dk(pion decays

before the lr)

Muon ID (lkr hac)

(2.22±0.07)x10-4 (2.15±0.07)x10-4 No factor needed (1.11±0.05)x10-3

Pipi0pi0(pion doesn’t

decay)

MuonID (mis ID-prob pion as muon)

(3.57±0.03)x10-3 (2.51 ±0.03)x10-4 Yes, suppress by probability of not decaying

(2.51 ±0.03)x10-4

(1.30±0.04)x10-3

Pipi0gdk(pion hast

decayed before lkr)

MuonID(lkr hac)

(2.44± 0.05)x10-3 (2.35± 0.05)x10-3 No factor needed (1.94±0.01)x10-4

Method 2:Method 2:

Sources of Background to pipi0+

Source of Background

Particle ID

used

Raw MC Acceptance

Raw Mc acceptance* particle ID


kmu3 E/P < 0.95

(3.27 +-0.04)x10-3

(3.27+-0.04) x10-3

(3.26+-0.08)x10-3

ke3 E/P < 0.95

(2.34 +-0.03)x10-3

(6.7+-0.4)x10-5

(9.9 +-0.6)x10-5

Method 2:Method 2:


Muon Veto

LKR HAC

LKR HAC

Muon Veto

Comparison between methods K+# after

Background subtracted

#withoutBackgroun

d subtracte

d

Raw # Events Data

Raw Acc MC

Acc*Particle ID

(muon veto or E/P <

0.95)

Acc * Particle ID * MC decay correction

if necessary

Backgrounds(Accbk*Br_bk)/

(AccS*BR_signal)

pipi0 3209,398 3209,815 488,334 0.1542±0.0001

0.1532±0.0001

0.1522±0.0001 Ke3 (1.01±0.06)x10-5Pipi0dk (1.07+-0.07)x10-4Kmu3 (1.3+-0.1)x10-5Pipi0 dk after lkr (1.52+-

0.03)x10-5

pipi0 3193,700 3204,410 497,464 0.1562 ±0.0001

0.1553±0.0001

0.1553±0.0001 Kmu3 (3.26+-0.08)x10-3Ke3 (9.9 +-0.6)x10-5

Kmu3

526,373 533,757 55,905 0.1052±0.0002

0.1047±0.0002

0.1047±0.0002 Pipi0dk (1.26±0.04)x10-2Pipi0pi0dk (1.11±0.05)x10-3

Kmu3

527,958 536,110 54,623 0.1052±0.0002

0.1018 ± 0.0002

0.1019 ± 0.0002

Pipi0dk (1.24+-0.03)x10-2Pipi0 (pion doesn’t decay) (1.6+-0.5)x10-3Pipi0pi0dk (1.11+-0.05)x10-3Pipi0pi0 (pion doesn’t decay)

(1.30+-0.04)x10-3Pipi0gdk (1.94+-0.01)x10-04

● Important steps have been taken to understand background.

● Since particle decays are not simulated in the last 6.4 m of the MC, the acceptances need to be corrected by the relevant particle decay probability

● When taking into account the particle ID efficiencies, acceptances, and background subtraction, I calculated the number of kmu3 and pipi0 events in both methods.

● Their current level of agreement is at the 3‰ for kmu3 and the 0.5 ‰ for pipi0 for the two methods. There is still some background still to be accounted for.

● Since particle ID eff are momentum dependent, next step is to extract the BR as a function of momentum.

Conclusion

Probability of pion NOT decaying between the LKR and the HAC

Method 2:Method 2:


anne dabrowski northwestern university na48/2 semileptonics meeting 22 nd february 2005 update kmu3...

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