1 The BaBar EMC, and B J/ hh analysis Nick Barlow, Yaw Ming Chia January 2006

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The BaBar EMC, and BJ/ hh analysis

Nick Barlow, Yaw Ming Chia

January 2006

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Contents

• EMC stuff:• EMC calibrator proxies• Interactive Kanga

• Analysis stuff:• Data/MC comparisons• Background studies• Fit validation• Future plans

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EMC calibrator proxies (1)

• “Raw” energy of EMC clusters needs to be calibrated to correct for:• Radiation damage to crystals• shower leakage from the back of crystals or

gaps between them

• Calibrations are applied at read-time using constants stored in the “Conditions database”• Bit of code that gets the calibrator from the

database is called a “proxy”• Should keep a cached copy of the calibrator

until it is no longer valid.

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EMC calibrator proxies (2)

• In July, database experts found that an EMC proxy was accessing the database 3 times per event processed• Significant impact on processing time, particularly

when many jobs running in parallel• Found that this was due to using a single custom

EMC proxy to retrieve different types of cluster calibrator• “Old” pi0 calibration, “new” pi0 calibration, MC

calibration• Fixed by using different instance of standard

proxy template for each type of calibration• Speeds up the processing of all BaBar jobs by up to

10%

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Interactive Kanga (1)

• The (no-longer) new BaBar computing model (CM2) uses ROOT-based “Kanga” files as its event store

• Can run traditional jobs over these Kanga files to produce ntuples or rootuples, OR can access files directly from ROOT command line using “Interactive Kanga” (E. Charles)

• Kanga files contain detector-level objects (individual hits), reco-level objects (e.g. tracks, EMC clusters), analysis-level objects (“BtaCandidates”)

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Interactive Kanga (2)

• Accessing data interactively is NOT good for:• Combinatorics• Vertexing, kinematic fitting• Particle ID using “standard” selectors

• However, with a bit of foresight, can do this stuff in “skim” job (centrally run), and store composite BtaCandidates along with associated “UsrData” in Kanga files

• It is possible to navigate from BtaCandidates to associated “reco” objects..

• However, until recently, EMC reco objects had no useful accessor functions• Requires access to conditions database for calibration

constants

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Interactive Kanga (3)

• Added accessor functions to persistent EMC classes for every variable people might use:• Raw and calibrated energies, cluster centroid positions,

shower shape variables, cluster energy sums

• Potentially useful for physics analysis, but already very useful for EMC studies..• Studies that would previously take hours or days writing

code and running ntuple-making jobs, can be done in minutes or seconds from the ROOT command line.. e.g.

Track intersection bug Projectivity correction to theta

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BJ/+- analysis(with Yaw Ming Chia)

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Comparison of continuum MC and off-resonance data

Points = off-res data

Yellow=uds MC

Light blue = ccbar MC

Hint of a rho peak in data, not reproduced in MC??

M(pipi) DeltaE

•Not enough statistics in off-res data for meaningful comparison

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Comparison of generic MC and on-resonance data (1)

•Jpsi peaks look pretty clean

•Virtually no continuum background in Jpsi->ee

•Mass peak slightly shifted to the left in data

Points = on-res data

Yellow=uds MC

Light blue = ccbar MC

Dark blue = B+B- MC

Green = B0B0bar MC

Jpsi->mumu Jpsi->ee

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Comparison of generic MC and on-resonance data (2)

M(pipi), grand sideband of mES/DE plane

mES, upper DE sideband

mES, lower DE sideband

•MC shapes and normalisations agree reasonably well with data

•BBbar background much larger than continuum

Points = on-res data

Yellow=uds MC

Light blue = ccbar MC

Dark blue = B+B- MC

Green = B0B0bar MC

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Generic B0B0bar MC with and without Jpsi events

Black histos are all generic B0B0bar

Red histos have events containing Jpsi removed (at MC truth level)

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Fits to non-Jpsi background (generic MC)

•uds, ccbar, BBbar generic MC (with Jpsi events removed) scaled to data luminosity and added together

•DE cut is wider than in final analysis (to increase statistics)

•PDFs used here are those used in previous BaBar analysis (J. Boyd, J. Weatherall) – will be revisited..

•Looking at MC truth for events in this peak – seem to be from D0->K0pi+pi- decays where we miss the K0

•Could perhaps remove some of these by combining pi pi combination with Ks cands and applyind D veto

•No success so far..

Argus function

Wiebull function plus reversed Wiebull function, plus B-W at rho mass

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Inclusive Jpsi MC with and without signal events

Black histos are all inclusive Jpsi MC

Red histos have

B->JpsiPiPi,

B->JpsiKs,

B->JpsiRho0,

B->Jpsi f2 events removed (at MC truth level)

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Fits to Jpsi background (inclusive Jpsi MC)

•|DE|<40MeV cut seems to remove most JpsiK* events, but what if DE is shifted in data wrt MC?

From looking at MC truth, these are JpsiK* events with kaon mis-identified as a pion

• Consider using separate PDF for B->Jpsi K* (BF known to 5% accuracy)

Argus function plus Gaussian at B mass

Wiebull function

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Fit validation

• Generate “toy MC” events from PDFs used in fit, and perform fit, comparing input number to fitted number of events in each category

• Repeat for 1000 “experiments”, and plot the distribution of “pulls” i.e. (fitted # - input #)/(error on fitted #)

• Looks OK for toy MC • However, not so good when we instead randomly

sample events from full MC. • This shows that the PDFs do not describe the

distributions very well

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Angular analysis of BJ/0

• Necessary to distinguish CP-even and CP-odd components (prerequisite for CP violation measurements)

• Define angles in “transversity frame”:

• Have written code to calculate angles, next step is to convert these into transversity amplitudes and check on signal MC

B0

J/

0

l+

l-

+

-

tr

tr

xtr

ztr

ytr

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Future plans

• Next steps: • Investigate background PDFs and possible

vetoes on problematic peaking backgrounds• Continue toy and embedded MC tests to

validate fit• “unblind” and measure BF(BJ/ +-)

• Longer term• Measure Branching Fraction for BJ/ + and

set upper limits for BJ/ K+K- and BJ/ • Angular analysis for BJ/ 0

• Possibly leading on to time-dependent CP violation measurement (sin2eff)