Physics of Heavy Flavour at

1
Physics of Heavy Flavour at

• Stefano Torre
• Universita degli Studi di Siena INFN Pisa
• for the CDF Collaboration

• Outline
• Tevatron _at_ Fermilab
• Detector trigger description
• Selected topics
• BR ACP in 2-body charmless decays
• Bs??? B? ??K?
• ??s
• Lb measurements
• Precise measurement of mass of Bc
• Conclusions

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Tevatron
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CDF detector _at_Tevatron

• solenoid 1.4 T
• TRACKING system
• SILICON TRACKER
• up to ?2
• SVX Fast r-? readout
• for trigger
• DRIFT CHAMBER
• 96 layers in ?lt1
• ? particle ID with dE/dx
• r-? readout for trigger
• TIME OF FLIGHT?particle ID

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Triggers and data samples
New for run II
Canonical

• Displaced trk
• lepton (e, ?)
• IP(trk) gt 120?m
• Pt(lepton) gt 4 GeV/c
• Semileptonic modes
• Hadronic Moments
• High statistics lifetimes
• Bd, Bs mixing

• 2-Track Trig.
• Pt(trk) gt 2 GeV/c
• IP(trk) gt 100 ?m
• Fully reconstructed hadronic modes
• Bd,s 2-body charmless decays
• Bs??? B? ??K?
• Lb ? Lc?, ?b ? ph
• ACP in 2-body D decays
• Bd, Bs mixing lifetimes

• Di-Muon (J/?)
• Pt(?) gt 1.5 GeV/c
• J/? modes down to low Pt(J/?) ( 0 GeV)
• ??s in fully rec. decays
• Bc ?J/y ?
• Masses, lifetimes of Bd, Bs, Lb
• Quarkonia
• X(3872 )
• Rare decays (BS(d)? mm D0? mm )

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2 body charmless B decays

• First evidence of CP violation in the Bd?K?- _at_B
  factories
• Several modes _at_CDF Bd???-, Bs?KK-, Bs?K-?,
• BR ACP can be predicted w/ hadronic unknowns
• Several decays to eliminate unknowns
• Under surveillance (only _at_CDF) Bs?KK-
• Measure ??s and ? (via Bs?KK-/Bd???-)

Bd?K?- Bs?KK- Bd???- Bs?K-?
unbinned Max-Likelihood fit on mass kin.dE/dx
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Analysis results
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Search for Lb?pK and pp decays
Prediction1 Br(Lb? pK)(1.4-1.9)10-6 Br(Lb?
pp)(0.8-1.2)10-6 compare to Br(B0?Kp)
1810-6 Large CP asymmetries O(10) expected in
b-baryons
Previous best limit from ALEPH BR(?b ?pK) lt
50x10-6 _at_ 90 BR(?b ?p?) lt 50x10-6 _at_ 90
Assign to both tracks the p mass to maximize
separation from the Bhh
1 Mohanta, Phys. Rev. D63074001,2001
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Bs??? B? ??K?
Bs ???
8 evts

• b?sss decays in Bs mesons
• Extract information on ? and ?
• Direct CP small ? test SM
• _at_CDF fully reconstructed hadronic decays

First evidence of Bs ???
BR(Bs???) (1.4 stat. 0.2syst.
0.5BR)x10-5
B? ??K? Unbinned likelihood fit to disentangle
signal and background
BR(B? ??K?) (7.6 1.3stat. 0.6syst.)x10-6
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??s

• Bs?J/?? Pseudoscalar ? Vector Vector
• Three different linear amplitudes ? relative
  orbital angular momentum
• Bs,L? CP even ? Long lifetime (L0,2)
• Bs,H? CP odd ? Short lifetime (L1)
• Simultaneous fit of lifetime and amplitudes
• Use B0 ?J/?K0 for X-check
• CDF finds large value for the lifetime difference

1
Accepted by P.R.L
1 hep-ph/0311130
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Fully hadronic Lb decay

• Lb?Lcp
• Test for theoretical models of b-baryon weak
  decays
• Understanding of QCD
• First BR measurement

B0 ? D-p
0.82 0.08stat. 0.11 syst. 0.22BR
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M(Bc) in Bc?J/??

• Bc
• Bc?J/?l? observed _at_CDF 1 and D02
• Large experimental uncertainty on M
• Validation of theoretical models (Lattice QCD and
  potential models)
• Fully reconstructed decay?Better mass resolution
• Blind search analysis
• Search region defined from previous mass meas.
• 6.4 2? 5.6 to 7.2 GeV/c2
• Use B?J/?K to estimate effect
• on signal (same topology)

1 CDF Collaboration in PRL 81 n.12 (1998) 2
ICHEP 2004
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Bc?J/?? - Results
Theory predictions 1
Signal 18.9?5.7 evt. Bkg 10.0?1.4 evt.

• M(Bc) (6287.0 4.8stat. 1.1syst.)MeV/c2
• Precision on M(Bc) improved by a factor 100
• Main syst. from Bkg shape given by low statistics
  
• Good agreement with theory

1 hep-lat/0411027
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Conclusions

• CDF has many interesting results
• Two body charmless B-decays
• Unique measurement of Bs BRs
• Promising sensitivity to ACP
• First observation of Bs ? ??
• B? ? ?K? promising measurement of ACP and BR
• Large ??s in Bs?J/??
• Lb
• Fully reconstructed hadronic decays
• Search for rare decays
• Best measurement of Bc mass in agreement with
  theory
• But this is just a part of the beginning

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and perspectives
A lot of new data coming

• Many analysis are still statistically limited and
  will see considerable improvements in sensitivity

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BACKUP
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Bc cut optimization

• Analysis cut optimization based on
• total number of events in search region assume
  signal negligible
• Monte Carlo events MC for signal
• Monte Carlo used for optimizing cuts, estimating
  sensitivity, relative to B

S number of signal events from MC B average
number of background events (data) from whole
region in a window 2-sM wide (60.4 MeV/c2).
Maximize
Balanced score-function for limit and discovery
(hep-physics/0308063)
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Bc cut optimization
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Bc reference channel

• B ?J/y K
• Used for
• checking data/MC
• estimating expected significance

• R ratio of production fractions
• Expected estimated signal from 4 to 30 events

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Bc track quality (Silicon)

• Compare hits/track in silicon of Bc and B

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Separation of individual modes

• The 4 major expected modes overlap to form a
  single unresolved bump
• Approach use Masskinematicstrack PID in an
  unbinned Max-Likelihood fit ? extract the
  fraction of each component.

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Separation from Kinematics
Mass (pp hypothesis) vs signed momentum imbalance
a1p1/p2 x q1. discriminates amongst signals
and between flavors for self-tagging decays. All
4 possible mass assignments (strongly correlated)
depend on them ? (a, Mpp) carry all relevant
information.
Mpp
Bd?pp-
Bd ? Kp-
Bd ? K-p
a
a
a
Mpp
Bs ? Kp-
Bs ? K-p
Bs ? KK-
a
a
a
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Separation from PID (dE/dx)

• K/? separation 1.4? _at_PTgt2 GeV/c
• Use time-dependent calibrations on CDFs huge
  D? D0? sample.
• This PID performance implies statistical
  separation of K-pi with resolution 60 of a
  perfect PID.
• Control of systematics Residual gain/baseline
  fluctuations cause correlated fluctuations of
  tracks in same event. They have been measured and
  explicitly included in the fit.

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B Mixing

• Measure the b flavour as function of time?Need to
  know the initial flavour
• Same Side Tag (SST) track from fragmentation of
  the b
• Opposite Side Tag (OST) informations from
  partially reconstructed B
• Soft Muon (SMT) / Soft Electron (SET) / Jet
  Charge (JQT)
• Tagger effectiveness ?D2
• ? efficiency
• D (2P-1) where Pcorrect answer probability

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B0 Mixing
B0 mixing measurements ? test the machinery for Bs
? md 0.502 0.007 ps-1
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??s

• Evaluate the percentage of long living state
  after applying cut on decay length
• Fit the time-integrated fraction