Sinad M' Farrington

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Bs Mixing and Lifetime Difference at CDF

• Sinéad M. Farrington
• for the CDF collaboration
• ICHEP July 2008
• Philadelphia

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This talk

• Bs Physics at CDF
• Bs mixing
• Bs lifetime difference
• See related talks at this conference
• CP Violation in Bs decays at CDF, Diego Tonelli
  (Thursday)
• Measurements of B hadron lifetimes, Satyajit
  Behari (Friday)
• Heavy Flavour theory, Tobias Hurth (Monday)

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The Tevatron
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Fermilab, Chicago
Currently the worlds highest energy collider

• Hadron collisions produce a wide spectrum of b
  hadrons
• Bs has not been copiously produced at the B
  factories
• Tevatron (LHC) are ideal places in which to study
  this system

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Bs Physics
0
Bound states
Matter?antimatter
NEW PHYSICS?
Vts
occurs via
W
W-
Vts
0
0

• The mass eigenstates (H and L) are superpositions
  of Bs and Bs
• System characterised by 5 parameters
• masses mH, mL lifetimes GH, GL (G1/t),
  phase bs
• Dms measured very precisely

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Dms Measurement
1 fb-1
Phys. Rev. Lett. 97, 242003 (2006)
(5.4s significance)
?ms 17.770.10(stat)0.07(syst) ps-1

• Extracted parameters dominated
  by theoretical errors

Vts / Vtd 0.2060 0.0007 (exp) 0.0081 (theo)
-0.0060
CDF now focuses on DGGH-GL, bs (Tonelli), G
(GHGL)/2 (Behari)
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Bs Physics
0

• DG so far measured imprecisely
• Extra test of Standard Model new physics can
  still enter through the phase
• Want to test the relation

?G ?GSMx cos 2bs
JHEP06 (2007) 072
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Measuring DG

• Assume no CP violation Bs L CP even, Bs H CP
  odd
• 1) Measure DG and Gs directly resolve the CP
  eigenstates by angular
• analysis (e.g. Bs ? J/y f)
• 2) CP specific proportion of CP even/odd is
  known
• Fit a single exponential (e.g. Bs? KK- )

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Direct measurement Bs?J/y f
2.8 fb-1

• Perform simultaneous mass, lifetime, angular fit

• Pseudo scalar?2 vectors S,D wave (CP even)
• and P wave (CP odd)
• Angular distributions give information on CP
  
• composition

J/y rest frame
f rest frame
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Bs?J/y f Results

• Simultaneous fit to mass, lifetime, angular
  parameters
• Assume no CP violation

c?s 459 12 (stat) 3 (sys) ?m ?? 0.02
0.05 (stat) 0.01 (sys) ps-1 A0 0.508
0.024 (stat) 0.008 (sys) A// 0.241 0.019
(stat) 0.007 (sys)
Published 1.7fb-1 analysis Phys. Rev. Lett. 100,
121803 (2008)
Predicted DG 0.096 0.039ps-1 (arxiv
0802.0977)
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Bs?J/y f Results

• Analysis with flavour tagging shown earlier this
  session (Tonelli)
• Allowing for CP violation and tagging induces
  bias
• Cannot obtain DG and bs independently
• Quote a confidence region
• Problem inherent to the
• fitter with low statistics

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CP specific Bs ? Ds Ds
0.36 fb-1

• Assume no CP violation Bs L CP even, Bs H CP
  odd
• b ?ccs decay (e.g. Bs ? Ds Ds) is pure CP even
• Thus a lifetime measurement of Bs ? Ds Ds would
  measure GL
• Branching ratio is related to DG/G
• (neglect small CP odd component)

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CP specific Bs ? Ds Ds

• BR (Bs ? Ds Ds ) measured relative to B0 ?Ds D-
• Three Ds decay modes reconstructed in each case

Phys. Rev. Lett. 100, 021803 (2008)
Bs ? Ds Ds
Signal mode yield 23
Control mode yield 395
95 C.L.
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Compare with prediction DG/G0.147 0.060
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CP specific Bs? KK
0.36 fb-1

• Lifetime measurement interesting since 100 CP
  even
• B?hh decays can be resolved at CDF
• Displaced track trigger
• Good mass resolution

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CP specific Bs? KK
Lifetime fit
t(Bs? KK-)1.530.18(stat) 0.02(sys) ps Use
HFAG flavour specific t1.4540.040 ps
(Working on update with t stat error 0.06-0.09ps
in gt2fb-1)
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Conclusions

• Accurate measurement of Dms
• Several ways of measuring DG have been deployed
• In the presence of new physics, these may not
  agree with one another
• Increased precision in Tevatron analyses may
  reveal hints of new physics

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?ms 17.770.10(stat)0.07(syst) ps-1
Vts / Vtd 0.2060 0.0007 (exp) 0.0081 (theo)
-0.0060
(95 C.L.)
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