Download - Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0 π - π + π 0, D 0 K - K + π 0 Relative to D 0 K - π + π 0 Giampiero Mancinelli,

Transcript
Page 1: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 1

Branching Ratio Measurements of DecaysBranching Ratio Measurements of Decays

DD00ππ--ππ++ππ00, , DD00KK--KK++ππ00 Relative toRelative to DD00KK--ππ++ππ00

Giampiero Mancinelli, Brian T. Meadows, Kalanand Mishra, Michael D. Sokoloff University of Cincinnati

We present measurements of the relative branching ratios from a sample of 232 fb-1 data. We find that

D0π-π+π0 ____________

D0K-π+π0D0K-K+π0 ____________

D0K-π+π0

= (1.064 0.006 0.015) 10-1

= (2.38 0.03 0.06) 10-2

These can be compared to PDG current world average (8.40 3.11) 10-2 for the first ratio and (0.95 0.26) 10-2 for the second.

Page 2: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 2

Track SelectionTrack Selection• Kaon & pion tracks

GoodTracksLoose, ≥ 20 DCH hits ≥ 6 total SVT hits, ≥ 2 SVT r-phi (z)

hits with at least 1 hit on inner layers

• 0 Reconstruction Photon Energy > 100 MeV

0 Energy > 350 MeV 115 MeV/c2 < M < 150 MeV/c2

• We search for decays of type D*+D0s

+

D0-+0, D0K-K+0, D0K-+0 0 • Integrated Luminosity ~ 232 fb -1

• For Bkg studies & cut optimization: ccbar Continuum ~ 138 fb -1

• For detection efficiency: signal MC 1.4M K-K+0, 4.5M -+0, 4.5M K-+0

Data SampleData Sample

• PID : LH Tight for both π and K

h- and h+ tracks are fit to a vertex Mass of 0 candidate is constrained

to m0 at h-h+ vertex 1.70 < m( h-h+0 ) < 2.0 GeV/c2

PCM ( D0 ) > 2.77 GeV/c

DD00hh--hh++00 Reconstruction Reconstruction D* Reconstruction D*+ candidate is made by fitting the D0 and

s+ to a vertex constrained in x and y to the

measured beam-spot for the run. |mD* - m D0 - 145.5| < 0.6 MeV/c2

Chose a single best candidate with smallest vtx 2 for the whole decay chain.

Summary of Event SelectionSummary of Event Selection

Page 3: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 3

Background Sources: Monte Carlo StudyBackground Sources: Monte Carlo Study

GeV/c2GeV/c2

GeV/c2 GeV/c2

--++00

KK--KK++00

Zoomed inZoomed in

Zoomed inZoomed in

Page 4: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 4

K-+0 reflection in -+0 (top) and K-K+0 (bottom) samples. I get the shape of the reflection from Monte Carlo (left) and the number of reflection events from data (right).

π-π+π0

Reflection StudyReflection Study

Monte Carlo: Shape

data: number

Monte Carlo: Shape

data: number

K-K+π0

Page 5: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 5

signal yield from datasignal yield from data

--++00 KK--KK++00KK--++00

• Signal fit with sum of 3 Gaussians

• Linear background

• K- +0 reflection peak in the sidebands of -+0 and K-K+0

Page 6: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 6

PID-corrected Reconstruction Efficiency on DPPID-corrected Reconstruction Efficiency on DP m2(K-π0) m2(π+π0) m2(K-π+)

m2(π-π0) m2(π+π0) m2(π-π+)

--++00

m2(K-π0) m2(K+π0) m2(K-K+)

KK--KK++00

KK--++00

Page 7: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 7

• Since the reconstruction efficiency is not uniform across phase space, each event is weighted according to its efficiency ( weight = 1/ efficiency ).

• As, in some parts of phase space, the bin-by-bin and fitted (with a 3rd order polynomial) efficiencies differ slightly, we use the bin-by-bin efficiency for analysis and the fitted efficiency for cross check.

• The average weight of reconstructed signal events in signal region is obtained after doing a background subtraction from sideband.

• The number of observed signal events was obtained directly from fitting the mass plots.• The total number of signal events produced in the experiment is product of average signal

weight and number of observed signal events for each mode.

Sproduced = S . < w >

• The ratio of branching ratios is obtained as the ratio of number of events produced for respective modes in the experiment. The statistical and systematic errors associated with the measurement are determined.

Calculation of ratio of BRsCalculation of ratio of BRs

Page 8: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 8

Compares well !

Comparison of background in Data and Monte Carlo sidebandsComparison of background in Data and Monte Carlo sidebands

2D pull pull Sideband

1.93 < mπ-π+π0

< 1.99 GeV/c2

Sideband

1.75 < mK-K+π0

< 1.80 GeV/c22D pullpull

--++00

KK--KK++00

Page 9: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 9

Comparison of background in signal region and in sideband of MCComparison of background in signal region and in sideband of MC

2D pull pullSideband

1.93 < mπ-π+π0

< 1.99 GeV/c2

Compares well !

2D pullpull

Sideband

1.75 < mK-K+π0

< 1.80 GeV/c2

--++00

KK--KK++00

Page 10: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 10

Efficiency-corrected Dalitz plotEfficiency-corrected Dalitz plot

m2(K-π0) m2(π+π0) m2(K-π+)~ 0.5 % bkg

m2(π-π0) m2(π+π0)m2(π-π+)~ 2 % bkg

m2(K-π0) m2(K+π0)m2(K-K+)~ 5 % bkg

--++00

KK--++00

KK--KK++00

Page 11: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 11

data generic ccbarCLEO model

Why we believe we are correcting the Dalitz plots Correctly ?Why we believe we are correcting the Dalitz plots Correctly ?

m2(K-π+)m2(K-π0) m2(K-π0)

m2(K-π+)m2(π+π0)m2(π+π0)

KK--ππ++00

KK--ππ++00

Page 12: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 12

Why we believe we are correcting the Dalitz plots Correctly ?Why we believe we are correcting the Dalitz plots Correctly ?

m2(π+π0)m2(K-π0) m2(K-π+)

2D pull pull

Comparison of Kππ0 data DP ( bkg 0.5%) with CLEO-model generated MC DP ( bkg 0.9%)

Page 13: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 13

Consistency Checks

• Separate analysis in different D0 lab momentum ranges.

• Separate analysis by charge ( i.e., separately for D*+ and D*- events ).

• Analysis using Monte Carlo as Data.

Systematic Errors

• error from Monte Carlo statistics

• cut variation systematics ( m cut )

• error from estimation of background events in signal region

• effect of background pdf modeling on signal yield

• PID systematics

• Tracking efficiency systematics

Study of SystematicsStudy of Systematics

Page 14: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 14

Consistency Check : Results for Disjoint SamplesConsistency Check : Results for Disjoint Samples

SP6 SP6 Generic Generic ccbar ccbar

DataData

We repeated exactly the same analysis procedure to obtain ratio of BRs for D0 and D0bar events separately and in five different lab momentum bins. All results are consistent within errors.

Full data sample: 0.12470.0004Generated : 0.1249

Full data sample: 0.01510.0002Generated : 0.0150

Result for MC treated as Data Result for disjoint Data samples

Page 15: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 15

Consistency Check : <w> and Yield for Disjoint Data SamplesConsistency Check : <w> and Yield for Disjoint Data Samples

KK--++00 --++00 KK--KK++00

< w >< w >

YieldYield

Page 16: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 16

Systematic Studies : Monte Carlo StatisticsSystematic Studies : Monte Carlo Statistics

D0 decay mode Average Weight MC Stat. Error

Kπ0 10.7471 0.0182πππ0 9.4308 0.0198

Kπ0 12.6101 0.0530

Effect of Background PDF model on Signal Yield:Effect of Background PDF model on Signal Yield:

We performed the mass plot fits with different background models ( linear, polynomial, and exponential shapes ) and different starting points for the fit. We observed up to 0.4 % variation in K-π+π0 signal yield, up to 0.8 % in case of π-π+π0 and up to 1.5 % in case of K-K+π0 .

Page 17: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 17

Systematic Studies : Systematic Studies : m Variationm Variation

m cut = m cut = 0.4 MeV0.4 MeV

m cut = m cut = 0.6 MeV0.6 MeV

m cut = m cut = 0.8 MeV0.8 MeV

B(πππ0 )/ B(Kπ0)

0.1065

0.0006

0.1064

0.0006

0.1061

0.0006

B(KKπ0 )/ B(Kπ0)

0.0236

0.0004

0.0238

0.0003

0.0238

0.0003

Based on this study, we assign a systematic error of 0.28 % in B(π-π+π0) / B(K-π+π0) and 0.84 % in B(K-K+π0) / B(K-π+π0) due to m cut.

We repeat the analysis with different m cuts. Any variation in the results is a systematic error.

Page 18: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 18

Systematic Studies : Background SubtractionSystematic Studies : Background Subtraction

KK--++00 Truth-Truth-matchedmatched

Non Non truth-truth-matchedmatched

Truth-Truth-matchedmatched

Truth-Truth-matchedmatched

Non Non truth-truth-matchedmatched

Non Non truth-truth-matchedmatched

--++00

KK--KK++00

Comparison of mass plots of truth-matched and non truth-matched events

Page 19: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 19

Systematic Studies : Background SubtractionSystematic Studies : Background Subtraction

KK--++00

--++00

KK--KK++00

Comparison of DPs of truth-matched and non truth-matched events

By repeating the analysis on generic ccbar events and doing the background subtraction of ‘true’ background events in the signal region, we find a systematic error of 0.6 % for B(π-π+π0 )/B(K-π+π0)And 0.9 % forB(K-K+π0) /B(K-π+π0).

2D pull

2D pull

2D pull

pull

pull

pull

Page 20: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 20

Systematic Studies : PID Systematics Systematic Studies : PID Systematics ( ( datadata ) )

Page 21: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 21

Systematic Studies : PID Systematics Systematic Studies : PID Systematics ( ( MCMC ) )

Page 22: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 22

Systematic Studies : PID Systematics Systematic Studies : PID Systematics ( ( datadata / / MCMC ) )

With this new PID correction factor, we find a systematic error in the average weight of 0.31 % for K-π+π0, 0.58 % for π-π+π0 and 0.84 % for K-K+π0 modes. We conservatively assign a PID systematics of 0.8% to B(π-π+π0)/B(K-π+π0) and 1.0% to B(K-K+π0)/B(K-π+π0).

Page 23: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 23

Systematic Studies : Tracking EfficiencySystematic Studies : Tracking EfficiencyThere are two types of issues related to tracking efficiency corrections and systematics:

1.) How well does our Monte Carlo mimic the real data with respect to hits-per-plane efficiency and resolution in DCH and SVT ?

2.) As tracks traverse the detector, they can interact, scattering either elastically or inelastically. The Monte Carlo has cross-sections built into it. How much this cross-section differs from the one in real data ?

The correction for the first effect is same for both Kaons and Pions ( as studied by Tracking AWG ) and cancel out in the ratio of BRs. The correction for the second effect is also same for Kaons and Pions, but the uncertainty in this correction is slightly different for the two particles. Based on the studies done by ISR people ( Solodov, et. Al., BAD 855 and BAD831), we conservatively assign a tracking efficiency systematics of 0.7 % for each of the two ratio of BRs.

Page 24: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 24

BAD 1469 ‘almost’ ready for AWG review. Hopefully, I will upload it by early next week. Get review done and write conference note for ICHEP. Prepare a journal draft for publication in PRD.

D0 decay mode Our Current Results(%)

B(πππ0 )/B(Kπ0) 10.64 0.06 0.15

B(Kπ0 )/B(Kπ0) 2.38 0.03 0.06

PDG Results(%)

8.40 3.11

0.95 0.26

The present results are preliminary.

Results and StatusResults and Status

Page 25: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 25

Backup SlidesBackup Slides

Page 26: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 26

Results for Disjoint Samples -1Results for Disjoint Samples -1

Page 27: Kalanand Mishra April 27, 2006 1 Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 Giampiero Mancinelli,

Kalanand Mishra April 27, 2006 27

Results for Disjoint Samples -2Results for Disjoint Samples -2