Title: Physics of Heavy Flavour at
1Physics 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
2Tevatron
3CDF 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
4Triggers 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 )
5 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
6 Analysis results
7Search 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
8 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
9??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
10Fully 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
11M(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
12Bc?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
13Conclusions
- 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
14and perspectives
A lot of new data coming
- Many analysis are still statistically limited and
will see considerable improvements in sensitivity
15BACKUP
16Bc 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)
17Bc cut optimization
18Bc 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
19Bc track quality (Silicon)
- Compare hits/track in silicon of Bc and B
20Separation 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.
21Separation 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
22Separation 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.
23B 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
24B0 Mixing
B0 mixing measurements ? test the machinery for Bs
? md 0.502 0.007 ps-1
25??s
- Evaluate the percentage of long living state
after applying cut on decay length - Fit the time-integrated fraction