Mini- Review(Belle

1
Mini- Review(Belle BaBar) By Antonio
Limosani JSPS Fellow (KEK-IPNS JAPAN)
XLth Rencontres de Moriond ELECTROWEAK
INTERACTIONS AND UNIFIED THEORIES
2
Motivation

• Fundamental parameter in SM
• CKM mixing matrix element
• Unitarity Triangle Sidelength

Directly test the mechanism for CP Violation in SM
3
semileptonic
hadronic
leptonic
T H EO R Y

• Complicated but
• manageable
• Formalisms
• exist

• Very complicated
• require factorisation

• Cleanest mode
• Need B decay
• constant fB

• Feasible
• e.g. B?Ds?
• measurements
• exist

• Extremely rare,
• not yet seen
• e,? helicity
• suppressed
• ? is challenging

• Many channels.
• Not rare.

EX P T
P R 0 S P E CT

• Need a revolution in
• calc. hadronic matrix
• elements

It is happening now

• Super B factory?
• LHCb?

But no ginntonic!
4
The B-factories
Luminosity KEK-B PEP-II
Peak gt15x1033 /cm2/s gt9x1033 /cm2/s
Total Integrated 364/fb 254/fb
1/fb ? 1.1M B-meson pairs
5
The Detectors
CsI(Tl) crystals

• Large solid angle coverage
• is crucial92

DIRC
e- (9GeV)
Drift Chamber
1.5T solenoid
Silicon Vertex Tracker
Instrumented Flux Return

• Excellent particle-ID
• e,?,?,?,K,p

6

• Use B?Xul?
• Measurements Types Inclusive(Xu?) and
  Exclusive(Xu)
• Experimentally challenging task
• background is large because
• Tight selection criteria results
• limited phase space
• extra theoretical uncertainties

7
Inclusive method

• Cuts to avoid B? Xc l ?
• Measure
• Extrapolate
• Calculate Vub

Shape function
Quark level
8
b-quark Shape Function

• What is it?
• b-quark Fermi motion
• inside the B-meson
• How do we get it?
• Universal at leading order for all b-quark
  to light-quark transitions.
• Use photon energy spectrum
• in B? Xs? decays

9
Lepton endpoint

• Well established method
• Endpoint region
• Suppress continuum background
• exploit topology differences
• Estimate non B background using
• off resonance data
• Estimate B?Xc l ? background
• use MC tuned to data

Equal normalisation
spherical
Jet-like
Off data
10
First Evidence of non-zero

• CLEO at ?(4S)
• November 1989
• Data 0.2/fb
• 30 Uncertainty

Phys.Rev.Lett.6416-20,1990
11
BaBar Results 82/fb
Data (continuum sub)
MC for BB background
Preliminary
Widest momentum region yet!
12
Other endpoint results
Belle 28/fb (2003)
CLEO 9/fb (2002)
Signal Region
Preliminary
Phys.Rev.Lett.88231803,2002
BaBar 80/fb
Preliminary
13
BaBar Results 80/fb
Preliminary
14
Full B reconstruction tag- Belle BABAR
Tag side Fully reconstruct the B via

• Signal side
• N(KSK)0
• Veto ?slow from D (BaBar only)
• Plepgt 1 GeV/c

• Event level
• ?Q0
• N(leptons)1, no extra ?
• -0.5 lt M2misslt 1.0 GeV2 (Belle)
• M2misslt 0.5 GeV2 (BaBar)
• pmiss within acceptance
• kinematic fit (BaBar only)
• Signal region (BLL Phys.Rev.D64113004,2001)
• Measure

15
BaBar result 82/fb
Data 82/fb 1000 B modes 110K B0 190K
B Purity 10-50 MB-tag, Plgt1 GeV/c
MB-tag
Preliminary
16
Belle result 140/fb
Data 140/fb 180 B modes 150K B0 250K
B Purity 50 MB-tag, Plgt1 GeV/c
MB-tag
Preliminary
17
Results
Preliminary
OPE HFAG 2004 Summer
Unfolded Mx spectrum from BaBar
Points - unfolded spectra Lines - Prediction
using Belle SF parameters In principle, can get
SF parameters directly
18
HFAG Vub inclusive averages

• ?2/n.d.f6.7/7
• (CL46.5)
• Vub(4.70?0.44)?10-3
• Do we see discrepancies between different
• kinematic regions
• Sub-leading effects?
• Weak annihilation
• effects?
• Quark-hadron duality violations?

19
Exclusive method

• Many measurements in the past, which all relied
  on neutrino reconstruction in untagged samples
• large detector related systematic uncertainty
• Tagged samples herald a new era!
• Loose cuts, good signal to background
• Clean topology (small detector systematic)
• Yet lacking lots of statistics
• To get Vub, use Form Factor(s) predictions from
• Lattice QCD
• Light Cone Sum Rules
• Quark models
• which describe hadronisation effects.
• Discriminate against models using a precise
  measurement of the
• differential branching ratios

CLEO 9/fb
20
BaBar (fully reconstructed B) 82/fb

• Data 82/fb
• Same cuts as inclusive analysis
• focus of exclusive mass regions ?,?,?,?
• Imposing Isospin relations

Preliminary
Preliminary
21
Belle - semileptonic tag method
Kinematics of double semileptonic
decay Reconstruction of all particles except
neutrinos Determine B direction up to a
two-fold ambiguity
22
Belle (semileptonic tag) 140/fb - Fits
23
Belle (semileptonic tag) 140/fb - q2
Preliminary
Use unquenched lattice QCD to extract Vub
Preliminary
24
Headlines

• Broken the 10 error barrier on Vub
• (30 in 1989!)
• Much more data to analyse
• Tagged samples will play a more significant role
• Our inclusive measurements challenge theorists
• to predict with greater precision
• Lattice QCD calculations are coming to the fore
• results of unquenched calculations now available

25
(No Transcript)
26
Measurement types at ?(4S) resonance
Full tags
Signal to Background
Partial tags
Luminosity
Untagged
Experimental Efficiency
27
Backup
28
Backup2
29
W

• Quark level
• Simple
• Real world
• Complicated

Vub
b
u

30
Backup3
31
(No Transcript)