B mixing CDF: quoi de neuf

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B mixing _at_CDF quoi de neuf
Donatella Lucchesi Infn University of Padova

• Several progress in the latest months and many
  more
• expected for the summer !
• Here new results for
• Bs yields
• Flavor tagging
• First attempt to perform a Bd mixing
  measurements
• News on proper time resolution and the PID from
  Alex

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Introduction what are we talking about
Dmd0.502 ps-1
Current limit Dmsgt14.5 ps-1 _at_95 C.L. ?
xsgt20.8 Bs oscillation 30 times faster than Bd
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Bs Yields Semileptonic Decays
G. Bauer, G. Gomez-Ceballos, I. Kravcenko, N.
Leonardo, C. Paus, J. Piedra, S. Rakitin, A.
Ruiz, I. Vila
First limit from these decays ?!
D-?K?
Only yields for the moment
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Bs Yields Fully Reconstructed Decays
A. Cerri, D. Lucchesi, S. Da Ronco, P.
Squillacioti, I. Furic, A. Belloni
Bs?Ds? Ds?jp j?kk
Bs?Dsp Ds ?ppp
Done !
Bs?Ds? Ds?kk k?kp
Bs?Ds?pp In progress
179 pb-1
Ntot 161 14
Bs?Ds? Ds?jp
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Bs Yields Fully Reconstructed Decays contd
124 pb-1
124 pb-1
Ntot 57 11
Ntot 57 11
Bs?Dsp Ds ?ppp
Bs?Dsp Ds ?ppp
NBs 17632
NB0 146 (from MC)
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B Tagging A quick Introduction
Same side Tagging
Opposite side tagging

• Flavor of the B at
• production time from
• particle charge produced
• close to the B
• fragmentation tracks
• B?B0?

Flavor of the B at production time from the
other B
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B Tagging CDF heavy flavor samples

• Trigger based on displaced tracks
• Lepton displaced track
• High statistics
• Lepton charge ? B flavor
• High background
• Two displaced tracks
• grant access to fully reconstructed B0 and B
• not so high statistics
• Trigger based on dimuons J/?
• J/?
• Low statistics
• Low background

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B Tagging CDF heavy flavor samples contd

• Background suppression
• QCD background removed by signed IP subtraction
• ( pp?uu , dd, ss events, displaced tracks from
  Ks/L
• and mismeasured track)
• Charm background removed by 2ltM(track-lepton)lt4
  GeV

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Soft Muon Tagging
M. Jones, J. Kroll, A. Wicklund, D. Usynin V.
Tiwari, G. Giurgiu, M. Paulini, J. Russ, B.
Wicklund

• Average between e and ? trigger data
• Dilution corrected from mixing and sequential
• ?eD2 for all sub samples

eNtagged/Ntotal D Nrs-Nws/NrsNws
Ptrel Pt of the ? respect to the track jet
associated with him
eD20.660 0.193 (stat)
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Jet Charge Tagging
Ilya Kravchenko

• Find track jet cone clustering
• Select best jets jet with secondary vertex
• or highest-Pt
• Calculate the jet charge

D depends on jet charge
Measured on e trigger data Dilution corrected
from mixing and sequential ?eD2 for all sub
samples
eD20.415 0.017 (stat)
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Same Side Tagging
G. Bauer, G. Gomez-Ceballos, I. Kravcenko, N.
Leonardo, C. Paus, J. Piedra, S. Rakitin, A.
Ruiz, I. Vila, G.J. Barker, M. Feindt, U Kerzel,
C. Lecci
Use the Run I algorithm

• Tracks close to the B meson with
• pT gt 350 MeV/c
• d0/s(d0) lt 3 (from PV)
• If multiple track candidates,
• select the one with minimum
• pTrel as tag

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Same Side Tagging contd
B? J/? K
B? D0?
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Same Side Tagging results
Final results combines the two decay channels
eD2 2.8 0.5 (stat)
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B0 mixing with SST
See Jonatan Piedra talk for details
B0? J/? K0
B0? D-?
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B0 mixing with SST results
Fitting function
?2 combined binned fit
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Conclusions
CDF is moving as fast as possible to measure
(or set a limit) the Bs mixing. Several
improvements already reached for the winter
Conferences Many other studies are in progress
to learn what we are doing and what we can reach
listen to the Alex talk