Ke2 and Kmu2 Mengkai Shieh Northwestern University.

Ke2 and Kmu2Ke2 and Kmu2

Mengkai ShiehMengkai Shieh

Northwestern UniversityNorthwestern University

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Physics MotivationPhysics Motivation

Measure Br Ratio of Ke2 more preciselyMeasure Br Ratio of Ke2 more precisely Test Lepton UniversalityTest Lepton Universality

)0017.06343(.

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eK

K

Ke

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Data SampleData Sample

Eventually, full run based on Ke2 and Eventually, full run based on Ke2 and Kmu2 triggersKmu2 triggers

Today, only Monte Carlo and data Today, only Monte Carlo and data based on minimum bias run (only Q1 based on minimum bias run (only Q1 trigger) so no trigger issues.trigger) so no trigger issues.

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Initial CutsInitial Cuts

1 track1 track 1 cluster1 cluster e/p > 0.9e/p > 0.9 HAC Energy < 10 GeVHAC Energy < 10 GeV LKR Energy > 2 GeVLKR Energy > 2 GeV 2 GeV< track p < 80 GeV2 GeV< track p < 80 GeV Track and cluster correspondTrack and cluster correspond Fiducial cuts 12cm < r < 110cmFiducial cuts 12cm < r < 110cm 5 sigma timing cut5 sigma timing cut

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Tuning of CutsTuning of Cuts

Look at Monte Carlo resultsLook at Monte Carlo results Maximize signal eventsMaximize signal events Minimize backgroundMinimize background

• K->pi0evK->pi0ev (Br 5%)(Br 5%)• K->pipi0K->pipi0 (Br 21%)(Br 21%)

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Monte Carlo ResultsMonte Carlo Results

Ke2 (signal), Br: 1.55 X 10-5Ke2 (signal), Br: 1.55 X 10-5 Ke3 (background), Br: 0.05Ke3 (background), Br: 0.05 Kpipi0 (background), Br: 0.21Kpipi0 (background), Br: 0.21 Kmu2 (normalization)Kmu2 (normalization)

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Ke2, Ke3 MC VertexKe2, Ke3 MC Vertex

Ke2 acceptance relatively flat, Ke3 drops sharply.Ke2 acceptance relatively flat, Ke3 drops sharply. Can use vertex to make a good cut.Can use vertex to make a good cut.

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Ke2, Ke3 MC pKe2, Ke3 MC pTT

Can cut for pt > 0.2Can cut for pt > 0.2

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Ke2, Ke3 MC MKe2, Ke3 MC Mfakefake

Mfake calculated with electron massMfake calculated with electron mass Can cut for Mfake > 0.45, Mfake < 0.525Can cut for Mfake > 0.45, Mfake < 0.525

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Ke2, Ke3 MC pKe2, Ke3 MC pee

Can cut on electron pCan cut on electron p Ke3 gone for p > 52 GeVKe3 gone for p > 52 GeV

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

2-Dimensional Cuts2-Dimensional Cuts

Look at 2-Dim acceptance plots to Look at 2-Dim acceptance plots to determine cuts for maximizing signal determine cuts for maximizing signal events while effectively cutting out events while effectively cutting out the background.the background.

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

AccAccvertvert vs Acc vs Accptpt

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

AccAccvertvert vs Acc vs AccMfakeMfake

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Kpipi0 MC pKpipi0 MC pTT

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Kpipi0 MC MKpipi0 MC Mfakefake

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Kpipi0 MC pKpipi0 MC ppipi

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

DataData

TuningTuning• Minimum bias runsMinimum bias runs

25 Aug 2003. Vus run25 Aug 2003. Vus run -------------------------------------------------- Runs 15746, 15747.Runs 15746, 15747. Intensity 1/8, trigger Q1/4.Intensity 1/8, trigger Q1/4. Total of 1860 bursts.Total of 1860 bursts.

Future Ke2, Kmu2 triggersFuture Ke2, Kmu2 triggers

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Extra CutsExtra Cuts

(vertex>2000||(vertex>2000||pt>.2)&&mfake>0.45&&mfake<0.52pt>.2)&&mfake>0.45&&mfake<0.525&&pt<.255&&pt<.25

Acc for Ke2 = .511Acc for Ke2 = .511 Acc for Ke3 = 0Acc for Ke3 = 0

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

DataData

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

DataData

Pisa 17-9-03Pisa 17-9-03 M. Shieh, Northwestern UniversityM. Shieh, Northwestern University

Data/ConclusionData/Conclusion

flux and trigger efficiency cancelflux and trigger efficiency cancel We get NWe get Nee and and from the data and acceptances from the Monte Carlo. from the data and acceptances from the Monte Carlo. Left and right sides are not equal, therefore, we still have background that Left and right sides are not equal, therefore, we still have background that

we need to eliminate.we need to eliminate. If we use the more rigid cuts instead of the looser box cut for vertex and pt If we use the more rigid cuts instead of the looser box cut for vertex and pt

(vertex>2000 && pt>.2), we get the following values: N_e=10, (vertex>2000 && pt>.2), we get the following values: N_e=10, acc_e=.296, and above equation becomes:acc_e=.296, and above equation becomes:

right side=.96x10^-5, left side=1.7x10^-5right side=.96x10^-5, left side=1.7x10^-5

May need to investigate pipi0 more to make a better selection.May need to investigate pipi0 more to make a better selection.

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