Bs and b Lifetimes and BRs at the Tevatron

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Bs and ?b Lifetimes and BRs at the Tevatron

• Satyajit Behari (For the CDF Collab.)
• Johns Hopkins Univ., Baltimore,USA

25th September 2006
Beauty 2006, University of Oxford, UK
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Contents

• Introduction
• Lifetime Measurements
• Motivation
• ?b lifetimes (?b ? J/? ?)
• Bs lifetimes
• Flavor specific
• t(Bs ? Ds l n)
• t(Bs ? Ds p, Ds p p p)
• ?GCP/GCP in tL(Bs ? K K-)
• ?GCP/G in BR(Bs ? Ds() Ds())
• Summary

• BR Measurements
• BR(Bs ? Ds() Ds())
• BR(Bs ? Ds1(2536) m n X)
• BR(Bs ? Ds Ds) / BR(Ds D)

Other talks

• BR(Bs ? m m) limits
• Talk by Cheng-Ju Lin
• ?G in Bs ? J/? ?
• Talk by Avdhesh Chandra

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The Tevatron
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CDF and DØ Detectors in Run 2

• Both detectors
• Silicon microvertex tracker
• Solenoid
• High rate trigger/DAQ
• Calorimeters and muons

L2 trigger on displaced vertices Excellent
tracking resolution Good low momentum PID
Good electron, muon ID and acceptance Excellent
tracking acceptance ? lt 2-3
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B Production at Tevatron
q
b
b
g
g
g
Flavor Creation (annihilation)
Flavor Creation (gluon fusion)
Flavor Excitation
Gluon Splitting

• Tevatron is a source of all B-hadron
• species, Bd, Bu, Bc, Bs and ?b
• sb 29.4 0.6 6.2 mb (? lt 1) (CDF)
• Huge cross-sections compared to the
• the B-factories but proportionally large
• backgrounds as well

• Since ?(bb) ltlt ?(pp) ? Events have to be
  selected with specific triggers
• Trigger requirements large bandwidth,
  background suppression, deadtimeless

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Triggers for B Physics

• Single-/Di-lepton (CDF/DØ)
• A high pT lepton or two leptons with lower pT
• J/? modes, masses, lifetimes, x-section
• Yields higher than Run I (low Pt threshold,
  increased acceptance)
• lepton displaced track - semileptonic sample
  (CDF)
• pT(e/?) gt 4 GeV/c, 120 ?m lt d0(Trk) lt 1mm,
  pT(Trk) gt 2 GeV/c
• Semileptonic decays, lifetimes, flavor tagging
• B Yields 3x Run I
• Two displaced vertex tracks - hadronic sample
  (CDF)
• pT(Trk) gt2 GeV/c, 120 ?m lt d0(Trk) lt 1mm, SpT
  gt 5.5 GeV/c

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Interests in B Hadron Lifetimes
C. Tarantino, hep-ph/0310241

• Test of non-spectator effects in decays of heavy
  hadrons which give rise to lifetime hierarchy
• t(B) t(B0) t(Bs0) gt t(?b) t(Bc)
• Heavy Quark Expansion includes these effects
  (expansion in 1/mb) and predicts lifetime ratios
• t(B)/t(B0) 1.00 0.05 x (fB/200 MeV)2
• t(Bs0)/t(B0) 1.00 0.01
• t(?b)/t(B0) 0.9
• The B,B0 lifetimes are precisely measured at
  B-factories. ?b and Bs0 ratios are unique to
  Tevatron.

THEORY (NLO)
EXPERIMENT
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Bs Lifetime Difference
Bs has a large branching fraction to CP
eigenstates Dominated by b ? ccs transition Bs ?
Ds()Ds()- (Bd b ?
ccd Cabibbo suppressed, 20x smaller)
SM prediction DGs/Gs GL-GH (9.3 4.6)
(Beneke et al)
hep-ph/0012222
-0.07 ( lt 0.29 at 95 CL)
World average DGs/Gs 0.070.09
(SLD, LEP, CDF I results t(Bs)t(Bd) constraint)

• Ways to measure
• Compare t(Bs ? CP even) to t(Bs ? CP mixed or CP
  odd)
• Angular analysis of Bs ? J/y f separates CP
  even and CP odd.
• See the talk by Avdhesh Chandra
• Indirect Measure Br (Bs ? Ds()Ds()-) , tL(Bs
  ? K K-)

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?b Lifetimes
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?b Lifetime in ?b ? J/? ?

• 1 fb-1 data
• 174 21 ?b events
• Extract lifetime by an unbinned maximum
  likelihood fit to mass and proper decay length.
• Major source of systematic is contamination from
  B0
• Using B0 ? J/? Ks0 lifetime

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?b Lifetime in ?b ? J/? ?

• 1 fb-1 data
• 538 38 ?b events
• Major sources of systematics are due to modeling
  of ct resolution and V0 pointing
• Using world average B0 ? J/? Ks0 lifetime

World best measurement!
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?b Lifetime Measurement vs Theory
t(?b)/t(B0)

• The world average on t(?b)/t(B0) measurements
  used to show 2s lower value than the NLO
  prediction so far.
• The new result sits above the prediction!
• Need more experimental inputs to conclude the
  issue.
• Looking forward to t(?b) in fully hadronic decay
  modes, e.g. ?b ? ?c p.

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Bs Lifetime Differences
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Bs Lifetime t(Bs ? Ds l n X)
Worlds best result!
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Bs Lifetime t(Bs ? Ds p, 3p)

• Fully reconstructed hadronic decays from
  displaced track trigger
• 360 pb-1 in CDF Run 2.
• Trigger bias is removed by a Monte Carlo
  approach.
• Mass and decay length fitted simultaneously to
  extract lifetime.
• Would be updated for 1 fb-1

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?GCP/GCP in tL(Bs ? K K-)

• Measure tL (95 CP even state)
• 360 pb-1 data from displaced track trigger
• Four hh- components are resolved by mass,
  kinematics and PID info.
• Bd lifetime is fixed to world average
• Dominant systematics from dE/dx based PID, MC pT
  input spectrum
• Extract ?GCP/GCP using flavor specific t(Bs0)
  from other measurements.

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?GCP/GCP in BR(Bs ? Ds() Ds())

• 1 fb-1 sample
• Ds ? fp, Ds ? fmn, (f ? K K-)
• Start with mDs sample (Ds ? fp), look for
  additional f (mDsf sample)
• Ratio of efficiencies estimated using simulated
  events.
• Directly fit Ds mass distribution to extract
  N(mDs). Unbinned likelihood to extract N(mfDs)
  (Lower statistics)
• N (mDs) 15225 ? 310
• N(mfDs) 19.3 ? 7.9

• Dominant sources of systematics
• BR(Bs ? mnDs())
• MC pT reweighting

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Tevatron ?GCP/GCP Summary

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Bs Branching Fractions
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Bs ? Ds1(2536) m n X

• cs quark in L1 state Provide test HQET
• A significant fraction of semileptonic decays
  
• Compare exclusive/inclusive decay rates
• Extract CKM matrix elements
• An additional channel for Bs mixing.
• Need to develop more understanding in the light
  of discoveries which dont agree with predictions
  DsJ(2317), DsJ(2460), DsJ(2632) SELEX and so
  on

• Bs ? Ds m n

D KS
p p
D0 p
K p
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Bs ? Ds1(2536) m n X(Contd..)
Comparison with theory
BR(Bs-gtDs1mnX) 0.86?0.16 ?0.13 ?0.09 () ISGW2
0.53, IQM 0.39, HQETQCD Sum rules
0.20
N 42.6 ? 8.6 5 s
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BR(Bs ? Ds Ds) / BR(B0 ? Ds D-)

5.8s Observation!
fs/fd BR(Bs ? DsDs ) / BR(B0 ? DsD) 0.43
0.11(Stat) 0.03(Syst) 0.10(BR) BR(Bs ? DsDs
) / BR(B0 ? DsD ) 1.67 0.41(Stat)
0.12(Syst) 0.24 (fs/fd) 0.39(BR)
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Summary

• With over 1 fb-1 accumulated data / experiment
  and much more to come, heavy flavor physics at
  Tevatron is entering a precision era.
• Using large Bs and ?b samples, unique to
  Tevatron, various theoretical predictions are put
  to stringent tests. Many world best measurements
  have been made.
• Lifetimes in fully hadronic ?b decays are
  underway. Other excited baryonic modes to follow.
• Check out more Tevatron B physics results
• CDF http//www-cdf.fnal.gov/physics/new/bottom/bo
  ttom.html
• DØ http//www-d0.fnal.gov/Run2Physics/WWW/resul
  ts/b.htm

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Backup-1 ?GCP/GCP in BR(Bs ? Ds() Ds())
Background processes