Physics of Heavy Flavour at - PowerPoint PPT Presentation

1 / 25
About This Presentation
Title:

Physics of Heavy Flavour at

Description:

Vertex. B. 2 body charmless B decays. unbinned. Max-Likelihood fit on mass kin. dE/dx. Bd ... B = average number of background events (data) from whole region ... – PowerPoint PPT presentation

Number of Views:27
Avg rating:3.0/5.0
Slides: 26
Provided by: stefan61
Category:
Tags: flavour | heavy | physics

less

Transcript and Presenter's Notes

Title: 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

2
Tevatron
3
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

4
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 )

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
7
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
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
10
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
11
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
12
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
13
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

14
and perspectives
A lot of new data coming
  • Many analysis are still statistically limited and
    will see considerable improvements in sensitivity

15
BACKUP
16
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)
17
Bc cut optimization
18
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

19
Bc track quality (Silicon)
  • Compare hits/track in silicon of Bc and B

20
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.

21
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
22
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.


23
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

24
B0 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
Write a Comment
User Comments (0)
About PowerShow.com