Transcript
Page 1: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF

Sinéad Farrington

On behalf of the CDF collaboration

ICHEP 2012, Melbourne

Page 2: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 2

Heavy Flavour Production and Decays

• Fragmentation – Kaons in association with D mesons

• Upsilon decay– Spin alignment

• Bc Lifetime– Fully reconstructed decay

Page 3: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 3

FragmentationCDF Public Note 10704

Page 4: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 4

Fragmentation• Quark fragmentation described by

phenomenological models– Study charged particle production

around heavy quarks• Kaons near Ds (260k) and D+ (140k) both

decaying to fp• Bs flavour tagging used similar techniques• D used for fragmentation studies

– No known resonance decay to Ds K– Charged D’s do not mix– Select prompt D’s to minimise contamination

from B’s

360 pb-1

Page 5: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 5

Probing Fragmentation

• Charge correlation between D and K – For Ds

• Opposite sign => early in fragmentation chain • Same sign => later in

fragmentation chain– For D+ • Random charge correlation

Page 6: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 6

Method• Take maximum pt tracks in DR=0.7 cone around D candidate– Measure kaon fraction with

likelihood fit– Particle ID: time of flight, dE/dx

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Production and Properties of Heavy Flavour at CDF, Sinead Farrington 7

Compare to Pythia/Herwig• Pt distribution for early fragmentation kaons

better agreement than later steps

Opposite sign

Same sign

Ds D+

Page 8: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 8

Upsilon Spin AlignmentPhys. Rev. Lett. 108, 151802 (2012)

Page 9: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 9

Upsilon Spin-alignment

• Discrepancies among experimental results

• Distribution described by:

– Previous measurements: lq only• Not invariant under change in reference system• Bias could be introduced if acceptance not uniform in j

– This measurement: full 3D measurement

PRL 102,151802 (2009)

6.7 fb-1

Page 10: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 10

Upsilons

• 550k Y(1S), 150k Y(2S), 76k Y(3S) decaying to mm• Background dominated by bb decays to muons– Constrain background by

scaling background in displaced (b-enriched) sample by extrapolation from sidebands

– Obtain geometric acceptance from MC

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Production and Properties of Heavy Flavour at CDF, Sinead Farrington 11

Results

• First measurement of Y(3S) parameters• None of the 3 states shows evidence of polarisation– Frame invariance crosschecks performed

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Production and Properties of Heavy Flavour at CDF, Sinead Farrington 12

Compare with Theory

• Y(1S) parameter: a=lqRecent calculations:Significant feed-down from cb states:

Page 13: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 13

Bc Lifetime

CDF Public Note 10533

Page 14: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 14

Bc J/y p+

• Bc was discovered at CDF– Short lifetime: b or c can decay or annihilate– Previous lifetime measurements only on partially reconstructed decays

• Fully reconstructed decay• Background parameters from sidebands

CDF Run II Preliminary

6.7 fb-1

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Production and Properties of Heavy Flavour at CDF, Sinead Farrington 15

Method

• B+J/y K+ used as a control sample

• Validate– ct Efficiency

• biased by cut requiring small pointing angle between decay vector and B momentum vector

– Background model– Fitter

CDF Run II Preliminary

CDF Run II Preliminary

CDF Run II Preliminary

Page 16: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 16

Results

• Fit:– Signal • Mass: Gaussian• Decay time: exponential

convoluted with resolution– Background • Mass: linear• Decay time: 3 exponential

Crosscheck:

CDF Run II Preliminary

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Production and Properties of Heavy Flavour at CDF, Sinead Farrington 17

Summary

• Fresh knowledge of fragmentation from our early dataset– Later stages of fragmentation chain not well

reproduced by MC• Upsilon polarisation measurement– No significant polarisations

• Bc lifetime measurement– First fully reconstructed decay measurement– Different systematics from previous measurements but

in good agreement

Page 18: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 18

Reference Frames

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Production and Properties of Heavy Flavour at CDF, Sinead Farrington 19

Crosscheck

Page 20: Production and Properties of Heavy  Flavour  at CDF

Production and Properties of Heavy Flavour at CDF, Sinead Farrington 20

Crosscheck

• Frame invariant quantity:


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