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Production and Properties of Heavy Flavour at CDF
Sinéad Farrington
On behalf of the CDF collaboration
ICHEP 2012, Melbourne
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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
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FragmentationCDF Public Note 10704
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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
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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
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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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Compare to Pythia/Herwig• Pt distribution for early fragmentation kaons
better agreement than later steps
Opposite sign
Same sign
Ds D+
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Upsilon Spin AlignmentPhys. Rev. Lett. 108, 151802 (2012)
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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
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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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Results
• First measurement of Y(3S) parameters• None of the 3 states shows evidence of polarisation– Frame invariance crosschecks performed
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Compare with Theory
• Y(1S) parameter: a=lqRecent calculations:Significant feed-down from cb states:
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Bc Lifetime
CDF Public Note 10533
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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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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
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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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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
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Reference Frames
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Crosscheck
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Crosscheck
• Frame invariant quantity: