B Physics and CP Violation

1
B Physics and CP Violation
Particles and the Universe Lake Louise Winter
Institute 16-22 February 2003

• Bob Kowalewski
• University of Victoria

2

• In remembrance of
• Professor Nate Rodning
• U. of Alberta
• (1957 2002)

3
Plan for the lectures

• Lecture 1
• Why build B factories?
• Review of CKM
• B production and decay, experimentation
• Calculational tools OPE, HQE, HQET
• Vub and Vcb

• Lecture 2
• BB oscillations
• CP violation
• Rare decays

4
Disclaimers

• These lectures are pedagogical in nature as
  such, I will not necessarily
• present the very latest measurements
• carefully balance CLEO/Belle/Babar/CDF/LEP (my
  own work is on BaBar it will be obvious!)
• Due to time constraints, important topics will be
  omitted in particular,
• not much will be said about Bs physics
• prospects for B studies at hadron machines will
  not be covered

5
Suggested reading

• The following reviews can be consulted for more
  detailed presentations of the material covered in
  these lectures
• B Decays and the Heavy Quark Expansion, M.
  Neubert, hep-ph/9702375
• The Heavy Quark Expansion of QCD, A. Falk,
  hep-ph/9610363
• Flavour Dynamics CP Violation and Rare Decays,
  A. Buras, hep-ph/0101336
• CP Violation The CKM Matrix and New Physics, Y.
  Nir, hep-ph/0208080

6
B decays a window on the quark sector

• The only 3rd generation quark we can study in
  detail
• Investigate flavour-changing processes,
  oscillationsCKM matrix

Cabibbo angle
B lifetime, decay
CP Asymmetries (phase)
BdBd and BsBs oscillations
1
7
B decays QCD at the boundary

• Mix of large (mb) and small momentum (?QCD)
  scales a laboratory for testing our
  understanding of QCD
• Large variety of decay channels to study in
  detail leptonic, semileptonic, hadronic
• High density of states ? inclusive measurements
  (quark-hadron duality)
• Vibrant interplay between experiment and theory

D
B
p
p
8
CP violation a fundamental question

• But reallywhy spend 109 on B factories?
• Explore CP violation
• outside of K0 system
• via different mechanisms (direct, mixing,
  interference)
• in many different final states
• Test the CKM picture
• survey the unitarity triangle
• can all measurements be accommodated in this
  scheme?

Pep2 / BaBar
KEKB / Belle
9
Return on investment
PDG 1999

• B factories give us
• New physics? (high risk)
• Determination of unitarity triangle (balanced
  growth)
• Better understanding of heavy hadrons (old
  economy)

PDG 2002
10
CKM matrix

• Kobayashi and Maskawa noted that a 3rd generation
  results in an irreducible phase in mixing
  matrix
• Observed smallness of off-diagonal terms suggests
  a parameterization in powers of sin?C

3 x 3 unitary matrix. Only phase differences are
physical, ? 3 real angles and 1 imaginary phase
11
Wolfenstein parameterization

• Buras, Lautenbacher, Ostermaier, PRD 50
  (1994) 3433.
• shown here to O(?5) where ?sin?120.22
• Vus, Vcb and Vub have simple forms by definition
• Free parameters A, ? and ? are order unity
• Unitarity triangle of interest is
  VudVubVcdVcbVtdVtb0
• Note that Vts /Vcb 1 O(?2)

all terms O(?3)
12
A Unitarity Triangle
Choice of parameters
?
Rt
Ru
g
b
13
Surveying the unitarity triangle

• The sides of the triangle are measured in b?ul?
  and b?cl? transitions (Ru) and in Bd0-Bd0 and
  Bs0-Bs0 oscillations (Rt)
• CP asymmetries measure the angles
• Great progress on angles need sides too!

Rt
?
Ru
g
b
GET A BETTER PICTURE
14
B meson production

• Threshold production in ee- at Y(4S) has
  advantages
• cross-section 1.1nb, purity (bb / Siqiqi) 1/4
• simple initial state (BB in p-wave, no other
  particles,decay products overlap)
• easy to trigger, apply kinematic constraints
• Role of hadron machines
• cross-sections much higher (102)
• Bs are produced
• triggering harder, purity (b / Siqi) (few/103)

15
Y(4S) experiments

• ee- ? Y(4S) ? BB- or B0B0 roughly 50 each
• B nearly at rest (ß? 0.06) in 4S frame no
  flight info
• Asymmetric beam energies boost into lab (ß?)4S
  0.5

on peak
off peak (qu,d,s,c)
2mB
16
Requirements

• High luminosity (need 108 B or more) this means
  L1033-34/cm-2s-1, 30-100 fb-1/year
• Measure ?t tB1-tB2 (need to boost Y(4S) in lab,
  use silicon micro-vertex detectors to measure ?z)
• Fully reconstruct B decays with good efficiency
  and signal/noise (need good track and photon
  resolution, acceptance)
• Determine B flavour (need to separate l, p, K
  over full kinematic range)

17
PEP-II and KEK-B
18
B factories KEK-B and PEP-II
Belle BaBarLmax (1033/cm2/s) 8.3
4.6 best day (pb-1) 434 303 total
(fb-1) 106 96

• Both B factories are running well

Belle
19
B factory detectors

• Belle and BaBar are similar in performance some
  different choice made for Cherenkov, silicon
  detectors
• Slightly different boost, interaction region
  geometry

CsI (Tl)
BaBar
DIRC
e (3.1 GeV)
Belle
e- (9 GeV)
IFR
SVT
DCH
20

• So ee-?bb then what?

21
b quark decay
b quark decay
c e ?e b

• Charged-current Lagrangian in SM
• Since mbltlt MW, effective 4-fermion interaction
  is
• CKM suppressed ? long lifetime 1.5ps

3 for color
22
Tree-level decays
single hadronic current reliable theory
Hadronic 73

• Semileptonic 26

Theoretical preductions tend to have large
uncertainties
Vub, helicity suppressed
Colour-suppressed Charmonium!
23
Loop decays significant due to large mt ,
sensitive to new physics
?,Z
b?s(d)ll O(10-6)

• b?sg O(10-2)

b?s? O(10-4)
B0 ? B0 (B0?B0) / B0 0.18
24
B hadron decay

• QCD becomes non-perturbative at ?QCD 0.2 GeV,
  and isolated b quarks do not exist.
• How does QCD modify the weak decay of b quark?
• Bound b quark is virtual and has some Fermi
  momentum this was the basis of the parton
  (valence) model of B decay
• Parton model had some successes, but did not
  provide quantitative estimates of theoretical
  uncertainties.
• Modern approach use the operator product
  expansion to separate short- and long-distance
  physics

Xh ?e

e
B
25
Operator Product Expansion

• The heavy particle fields can be integrated out
  of the full Lagrangian to yield an effective
  theory with the same low-energy behaviour (e.g.
  V-A theory)
• The effective action is non-local locality is
  restored in an expansion (OPE) of local operators
  of increasing dimension ( 1/Mheavyn )
• The coefficients are modified by perturbative
  corrections to the short-distance physics
• An arbitrary scale µ separates short- and
  long-distance effects the physics cannot depend
  on it

26
OPE in B decays

• The scale µ separating short/long distance
  matters not ? except in finite order
  calculations ?
• typically use ?QCD ltlt µ mb ltlt MW aS(mb) 0.22
• Wilson coefficients Ci(µ) contain weak decay and
  hard-QCD processes
• The matrix elements in the sum are
  non-perturbative
• Renormalization group allows summation of terms
  involving large logs (ln MW/µ) ? improved Ci(µ)

27
Heavy Quarks in QCD

• There is no way to avoid non-perturbative effects
  in calculating B hadron decay widths
• Heavy Quarks have mQ gtgt ?QCD (or, equivalently,
  Compton wavelength ?Q ltlt 1/?QCD )
• Since ?Q ltlt 1/?QCD, soft gluons (p2 ?QCD)
  cannot probe the quantum numbers of a heavy
  quark
• ? Heavy Quark Symmetry

28
Heavy Quark Symmetry

• For mQ?8 the light degrees of freedom decouple
  from those of the heavy quark
• the light degrees of freedom are invariant under
  changes to the heavy quark mass, spin and flavour
  
• SQ and Jl are separately conserved.
• The heavy quark (atomic nucleus) acts as a static
  source of color (electric) charge. Magnetic
  (color) effects are relativistic and thus
  suppressed by 1/mQ
• HQ symmetry is not surprising - different
  isotopes of a given element have similar
  chemistry!

29
Heavy Quark symmetry group

• The heavy quark spin-flavour symmetry forms an
  SU(2Nh) symmetry group, where Nh is the number of
  heavy quark flavours.
• In the SM, t and b are heavy quarks c is
  borderline.
• No hadrons form with t quarks (they decay too
  rapidly) so in practice only b and c hadrons are
  of interest in applying heavy quark symmetry
• This symmetry group forms the basis of an
  effective theory of QCD Heavy Quark Effective
  Theory

30
Heavy Quark Effective Theory

• The heavy quark is almost on-shell pQmQvk,
  where k is the residual momentum, kµ ltlt mQ
• The velocity v is same for heavy quark and
  hadron
• The QCD Lagrangian
  for a heavy quark can be rewritten to emphasize
  HQ symmetry
• In Q rest frame, h(H) correspond to upper(lower)
  components of the Dirac spinor Q(x)

31
HQET Lagrangian

• The first term is all that remains for mQ?8 it
  is clearly invariant under HQ spin-flavour
  symmetry
• The terms proportional to 1/mQ are
• the kinetic energy operator OK for the residual
  motion of the heavy quark, and
• the interaction of the heavy quark spin with the
  color-magnetic field, (operator OG)
• The associated matrix elements are
  non-perturbative however, they are related to
  measurable quantities

32
Non-perturbative parameters

• The kinetic energy term is parameterized by
• ?1 ltBOKBgt/2mB
• The spin dependent term is parameterized by
• ?2 -ltBOGBgt/6mB
• The mass of a heavy meson is given by
• The parameter ? arises from the light quark
  degrees of freedom and is defined by ?
  limm?8(mH mQ)

33
Phenomenological consequences

• The spin-flavour symmetry relates b and c
  hadrons
• SU(3)Flavour breakingm(Bs) - m(Bd) ?s ?d
  O(1/mb) 903 MeVm(Ds) - m(Dd) ?s ?d
  O(1/mc) 991 MeV
• Vector-pseudoscalar splittings (? ?2 0.12
  GeV)m2(B) - m2(B) 4?2O(1/mb) 0.49 GeV2
  m2(D) - m2(D) 4?2O(1/mc) 0.55 GeV2
• baryon-meson splittingsm(?b) - m(B) - 3?2/2mB
  O(1/mb2) 3126 MeV m(?c) - m(D) - 3?2/2mD
  O(1/mc2) 3201 MeV

34
Exclusive semileptonic decays
D ?e

e
B

• HQET simplifies the description of B?Xce? decays
  and allows better determinations of Vcb
• Consider the (zero recoil) limit in which vcvb
  (i.e. when the leptons take away all the kinetic
  energy)
• If SU(2Nh) were exact, the light QCD degrees of
  freedom wouldnt know that anything happened
• For mQ?8 the form factor can depend only on
  wvbvc (the relativistic boost relating b and c
  frames)
• This universal function is known as the
  Isgur-Wise function, and satisfies ?(w 1) 1.

35
B?De? form factors

• The HQET matrix element for B?De? decays is
• The form factors hV are related in HQET
• ? must be measured predicted relations can be
  tested!

36
Determination of Vcb

• The zero-recoil point in B?D()e? is suppressed
  by phase space the rate vanishes at w1,
  requiring an extrapolation from wgt1 to w1.
• 
  includes radiative and HQ
  symmetry-breaking corrections, and

Lukes theorem
37
Current status of Vcb from B?De?

• Measurements of the rate at w1 are
  experimentally challenging due to
• limited statistics dG/dw(w1) 0
• softness of transition p from D?D
• extrapolation to w1
• Current status (PDG 2002)

5 error
38
Tests of HQET

• Predicted relations between form factors can be
  used to test HQET and explore symmetry-breaking
  terms
• The accuracy of tests at present is close to
  testing the lowest order symmetry-breaking
  corrections e.g. the ratio of form factors ? /?
  for B?De? / B?De? is

39
Exclusive charmlesssemileptonic decays
p ?e

e
B

• HQET is not helpful in analyzing B?Xue? decays in
  order to extract Vub
• The decays B0?pl-? and B??l-? have been observed
  (BF 210-4) large backgrounds from ee-?qq
  events
• Prospects for calculating the form factor in
  B?pl? decay on the Lattice are good current
  uncertainties are in the 15-20 range on Vub
• Not yet very constraining

40
Inclusive Decay Rates

• The inclusive decay widths of B hadrons into
  partially-specified final states (e.g.
  semileptonic) can be calculated using an OPE
  based on
• HQET - the effects on the b quark of being bound
  to light d.o.f. can be accounted for in a 1/mb
  expansion involving familiar non-perturbative
  matrix elements
• Parton-hadron duality the hypothesis that decay
  widths summed over many final states are
  insensitive to the properties of individual
  hadrons and can be calculated at the parton level.

41
Parton-Hadron Duality

• One distinguishes two cases
• Global duality the integration over a large
  range of invariant hadronic mass provides the
  smearing, as in ee-?hadrons and semileptonic HQ
  decays
• Local duality a stronger assumption the sum
  over multiple decay channels provides the
  smearing (e.g. b?s? vs. B?Xs?). No good near
  kinematic boundary.
• Global duality is on firmer ground, both
  theoretically and experimentally

42
Heavy Quark Expansion

• The decay rate into all states with quantum
  numbers f is
• Expanding this in aS and 1/mb leads towhere
  ?1 and ?2 are the HQET kinetic energy and
  chromomagnetic matrix elements.
• Note the absence of any 1/mb term!

free quark
43
Inclusive semileptonic decays
X ?e

e
B

• The HQE can be used for both b?u and b?c decays
• The dependence on mb5 must be dealt with in
  fact, an ambiguity of order ?QCD exists in
  defining mb. Care must be taken to correct all
  quantities to the same order in aS in the same
  scheme)
• The non-perturbative parameters ?1 and ?2 must be
  measured ?20.12 GeV from B-B splitting ?1
  from b?s?, moments in semileptonic decays,

44
The upsilon expansion1

• The mb appearing in the HQE is the pole mass it
  is infrared sensitive (changes at different
  orders in PT)
• Instead, one can expand both G(B?Xf) and mY(1S)
  in a perturbation series in aS(mb) and substitute
  mY(1S) for mb in G(B?Xf) this is the upsilon
  expansion
• There are subtleties in this the expansion must
  be done to different orders in aS(mb) in the two
  quantities
• The resulting series is well behaved and gives
• 1 Hoang, Ligeti and Manohar, hep-ph/9809423

4 error
45
Semileptonic B decay basics

• BF(B?Xl-?) 10.5
• G(b?cl-?) is about 60 times G(b?ul-?) (not
  shown)
• Leptons from the cascade b?c?l have similar rate
  but softer momentum spectrum, opposite charge

b?l-
b?l
46
Vcb from inclusive s.l. B decays

• GSL tBBFSL ? G(B?Xcl?) ? Vcb2
• Using (from PDG2002)t(B0) 154216 fs, t(B)
  167418 fs, BF(B?Xcl?) (10.380.32) along
  with the aforementioned theoretical relation,
• Vcb (40.40.5exp0.50.8th)10-3
• Compatible with Dl? result 3rd best CKM element

Knowledge of ?1, ?2
higher orders in mb, aS
47
Determination of Vub

• The same method (GSL) can be used to extract
  Vub.
• Additional theoretical uncertainties arise due to
  the restrictive phase space cuts needed to
  reject the dominant B?Xce? decays
• Traditional methods usesendpoint of lepton
  momentumspectrum acceptance 10leading to
  large extrapolationuncertainty

48
Better(?) methods for determining Vub

1. invariant mass q2 of l? pair (acceptance 20,
   requires neutrino reconstruction)

B0?Xul-?
B?Xul-?

1. mass mx recoiling against l? (acceptance 70,
   but requires full reconstruction of 1 B meson)

49
Shape function

• The Shape function, i.e. the distribution of the
  b quark mass within the B
• Some estimators (e.g., q2) are insensitive to it

accept
reject
reject
accept
50
Measuring non-perturbative parameters and testing
HQE

• mb and ?1 can be measured from
• E? distribution in b?s?
• moments (mX, sX, El, EWpW) in semileptonic
  decays
• Comparing values extractedfrom different
  measurementstests HQE
• This is currently an area ofsignificant activity

?1
mb/2??
51
Hadronic B decays

• More complicated than semileptonic or leptonic
  decays due to larger number of colored objects
• Many of the interesting decays are charmless ?
  HQET not applicable
• QCD factorization and other approaches can be
  used, but jury is still out on how well they
  agree with data
• No more will be said in these lectures

52
Surveying the unitarity triangle

• The sides of the triangle are measured in b?ul?
  and b?cl? transitions (Ru) and in Bd0-Bd0 and
  Bs0-Bs0 oscillations (Rt)
• CP asymmetries measure the angles
• Great progress on angles need sides too!

Rt
?
Ru
g
b
GET A BETTER PICTURE
53
END OF LECTURE 1
54
Plan for the lectures

• Lecture 1
• Why build B factories?
• Review of CKM
• B production and decay, experimentation
• Calculational tools OPE, HQE, HQET
• Vub and Vcb

• Lecture 2
• BB oscillations
• CP violation
• Rare decays

55
B0-B0 oscillations

• B mesons are produced in strong or EM
  interactions in states of definite flavour
• 2nd order ?b2 transition takes B0?B0 making
  decay eigenstates distinct from flavour
  eigenstates
• Neutral B mesons form 2-state system
• Mass eigenstates diagonalize effective Hamiltonian

56
Effective Hamiltonian for mixing

• Two Hermitian matrices M and G describe
  physics

M11M22 (CPT) G11 G22
Quark masses, QCDEM
Weak decay
?b2
intermediate state off-shell, on-shell
57
?m, ?G

• The time evolution of the B0B0 system
  satisfies
• The dispersive part of the matrix element
  corresponds to virtual intermediate states and
  contributes to ?m
• The absorptive part corresponds to real
  intermediate (flavour-neutral) states and gives
  rise to ?G

58
Bd oscillations

• For B0(bd), ?G/Gltlt1 only O(1) of possible
  decays are to flavour-neutral states (ccd or
  uud) dominant decays are to cud or cl?
• Consequently, most decay modes correlate with the
  b quark favour at decay time. Contrast with K0
  system
• Therefore most decay modes are not CP eigenstates
  (which are necessarily flavour-neutral)
• The large top quark mass breaks the GIM
  cancellation of this FCNC and enhances rate ?m/G
  large tB allows oscillations to compete with decay

59
Evidence for Bd oscillations
10.0
15.0
5.0
1
2
4
dileptons

• The fraction of like-sign dileptons vs. time
  (does not go from 0 to 1 due to mis-tagging)
• Y(4S) has JPC1- - so BB are in a P-wave. B1 and
  B2 are orthogonal linear combinations of B
  eigenstates
• ?m (0.4890.008) ps-1

20.7 fb-1
unmixed
mixed
1
Belledileptons29.4 fb-1
2
4
60
SM expectation for Bd oscillations

• The box diagram for ?b2 transitions contains
  both perturbative and non-perturbative elements
• OPE calculation gives
• Uncertainty in BBFB2 dominates (30)
• Hope for improvements using Lattice QCD

From ltB0 (V-A)2B0gt
universal fn of (mt/mW)2
pert. QCD
61
Experimental status of Bs oscillations

• In the BS system the CKM-favoured decay b?ccs
  leads to flavour-neutral (ccss) states, so ?G/G
  may be as large as 15 (but we still have ?Gltlt
  ?m)
• Note G(Bs) G(Bd) to O(1)
• ?m/G is much larger than for Bd, since
  Vts2/Vtd230
• Fast oscillations are hard to study (need superb
  spatial resolution one complete oscillation
  every ?50µm).
• Current limit (PDG2002) ?ms gt 13 ps-1 at 95
  c.l.
• ?md /?ms (Vtd/Vts)2 (corrections are
  O(15))

62
Unitarity triangle constraints from non-CP
violating quantities

• These measurements alone strongly favour a
  non-zero area for the triangle this implies CP
  violation in SM

63
(No Transcript)
64
CP violation

• CP violation is one of the requirements for
  producing a matter-dominated universe (Sakharov)
• Why isnt C violation alone enough (CYgt Ygt)?
• Chirality if YL behaves identically to YR then
  CP is a good symmetry. In this case the
  violation of C does not lead to a
  matterantimatter asymmetry.
• CP violation first observed in K0L decays to the
  (CP even) pp final state (1964)

65
CP violation in SM

• Mechanism for CP violation in SM Kobayashi and
  Maskawa mixing matrix with 1 irreducible phase
• CP violation is proportional to the area of any
  unitarity triangle, each of which has area J/2,
  whereJ Jarlskog invariant c12c23c213s12s23s13
  sind A2?6?
• Jmax is (6v3)-1 0.1 observed value is 410-5
  this is why we say CP violation in SM is small
• Massive neutrinos imply that the same mechanism
  for CP violation exists in lepton mixing (MNS)
  matrix
• Since it depends on a phase, the only observable
  effects come from interference between amplitudes

66
CP violation in flavour mixing

• This is the CP violation first observed in
  nature, namely the decay of KL to pp, which comes
  about because of a small CP-even component to the
  KL wavefunction
• Very small in B system because ?Gltlt?m
• This type of CP violation is responsible for the
  small asymmetry in the rates for KL?pe-?e and
  KL?p-e?e
• Non-perturbative QCD prevents precise predictions
  for this type of CP violation

67
CP Violation in Mixing

• Compare mixing for particle and antiparticle

off-shell
off-shell
on-shell
on-shell
CP-conserving phase
arbitrary phase
68
Direct CP violation
CP violation in decay amplitude
partial decay rate asymmetry
2 amplitudes A1 and A2
Weak phase difference
Strong phase difference
For neutral modes, direct CP violationcompetes
with other types of CP violation
Non-perturbative QCD prevents precise
predictions for this type of CP violation most
interesting modes are those with ACP0 in SM
From Gautier Hamel de Monchenault
69
CP violation in the interference between mixing
and decay
mixing
70
Calculating l

• Piece from mixing (q/p)

? pure phase

• Piece from decay

if just one direct decay amplitude to fCP
No dependence on d!
71
Calculating l for specific final states
assuming only tree-level decay
decay
B0 mixing
K0 mixing
72
Mother Nature has been kind!

• B0 decays to CP eigenstates that are dominated by
  a single decay amplitude allow a clean prediction
  for the CP asymmetrywhere ?CKM is related to
  the angles of the unitarity triangle (e.g. ?CKM
  ß for B?J/? KS)

73
Angle a not as simple

• The quark level transition b?uud gives access to
  sin(2a). In this case, however, tree and Penguin
  amplitudes can be comparable more complicated.
• Decay modes B0?pp, ?p,
• In practice, the coefficients of the time
  dependent CP asymmetry, Spp and Cpp (-App), are
  measured
• Additional measurements are needed to separately
  determine the tree and penguin amplitudes these
  involve all B?pp charge combinations or B??p with
  an analysis of the Dalitz plot.

74
Relation to unitarity triangle
(bd)?uudd
B0d oscillationsB0s oscillations
SemileptonicB?Xue?
(bd)?cusd(bd)?cudd
(bd)?ccsd, ccdd, ccss
75
Measuring CP violation in Bd decays

• CP violation in Bd decays can be studied at
  asymmetric ee- colliders (B factories) with
  vsmY(4S)
• Time integrated CP asymmetry vanishes
  measurement of ?t uses boost of CM along beam
  line and precise position measurements of charged
  tracks
• Reconstruction of CP eigenstates requires good
  momentum and energy resolution and acceptance
• Determination of flavour at decay time requires
  the non-CP tag B to be partially reconstructed

76
Overview of CP asymmetry measurement at B
factories
Exclusive B Meson Reconstruction
B-Flavor Tagging
77
Relation of mixing, CP asymmetries
dilution due to mis-tagging
Use the large statistics Bflav data sample
to determine the mis-tagging probabilities and
the parameters of the time-resolution function
78
Paying homage to Father Time
measure ?z lifetime convoluted with vertex
resolution derive ?t
Unmixed
z of fully reconstructed B is easy to measure z
of other B biased due to D flight length. ? Same
effects arise for CP and flavour eigenstates ?
Mixed
79
Impact of mistagging, Dt resolution
wProb. for wrong tag
No mistagging and perfect Dt
D1-2w0.5
Nomix
Mix
Dt
Dt
Raw asymmetry
Dt res 99 at 1 ps 1 at 8 ps
Dt
Dt
80
Flavour determination of tag B

• Use charge of decay products
• Lepton
• Kaon
• Soft pion
• Use topological variables
• e.g., to distinguish between primary, cascade
  lepton
• Use hierarchical tagging based on physics
  content
• Four tagging categories Lepton, Kaon, NN e
  70
• Effective Tagging Efficiency

81
B reconstruction

• B?J/?K0, J/??ll- is very clean can be used at
  hadron machines as well
• At ee- bfactorieskinematicconstraintsallow
  useof KL too!

Belle
BaBar
82
Results for sin2ß

• BaBar and Belle both see significant CP
  violation
• syserr ? as ?Ldt ?

BaBar
Belle
83
Hadronic Rare B Decays Towards sin(2a)

• B-gtpp would measure sin(2a)
• if it werent for Penguin pollution!

84
Hadronic Rare B Decays B?pp-, B?Kp-
B?pp-
DEEB - ECM/2
mES
Both modes peak at B mass need ?E and particle ID
B?Kp-
85
CP Asymmetry in B?pp
Hot topic!
Belle
BaBar
86
CP violation in Bs decays

• The Bs system is as good a place to study CP
  violation as Bd however, Bs production is
  suppressed
• Presence of spectator s quark ? different set of
  unitarity angles are accessible
• Rapid oscillation term (?ms30?md) makes time
  resolved experiments difficult
• Width difference ?G may be exploited instead
• Dedicated B experiments at hadron facilities
  (like LHC-B) will be needed to do this

87
Current status in ?-? space

• Measurements are consistent with SM
• CP asymmetries from B factories now dominate the
  determination of ?
• Improved precision needed on Vub and other
  angles (a,?)
• Bs oscillations too!

88
Rare decays

• Window on new physics look for modes highly
  suppressed in SM
• FCNC decays, forbidden at tree level b?s(d)?,
  b?s(d)ll-, b?s(d)??
• Leptonic decays B0?ll-, B?l?
• New physics can enhance rates, produce CP
  asymmetries, modify F/B asymmetries
• Ratio of b?d / b?s FCNC decays measures
  Vtd2/Vts2

89
b?s(d)?

• B?K? and b?s? (inclusive) both observed by CLEO
  in mid-90s first EW penguins in B decay
• BR consistent with SM limits H, SUSY
  BF(b?s?) (3.3 0.4 )10-4 (expt)
  (3.290.33)10-4 (theory)
  BF(B?K?) (4.1 0.3 )10-5 (expt)
• non-strange modes (e.g. B???) not yet observed
  limits 10-5 and improving
• Photon spectrum also used to probe shape function

90
b?s(d)ll (or ??)

• Replace l?? to get graphs for b?s??
• Presence of W, Z give sensitivity to new physics
  that does not couple to ?
• New heavy particles at EW scale (from SUSY, etc.)
  can give significant rate changes w.r.t. SM
  prediction

91
B?Xsll

• B?K()ll observed by Belle and BaBar
• No surprises yet,sensitivity is stillimproving

veto J/? region
92
b?s??

• Cleanest rare B decay sensitive to all
  generations (important, since b?stt- cant be
  measured)
• BF quoted are sum over all ? species
• SM predictions
• BF(B ? Xs??) lt 6.410-4 at 90 c.l. (ALEPH)
• BF(B?K??) lt 2.410-4 at 90 c.l. (CLEO)
• lt 9.410-5 at 90
  c.l. (BaBar prelim)

93
B Physics broad and deep

• CP violation in B decays is large and will be
  observed in many modes
• Precision studies of B decays and oscillations
  provide the dominant source of information on 3
  of the 4 CKM parameters
• Rare B decays offer a good window on new physics
  due to large mt and Vtb
• B hadrons are a laboratory for studying QCD at
  large and small scales. A large range of
  measurements can be made to test our
  calculations. Modern techniques allow a
  quantitative estimate of theoretical errors

94
A glimpse of things to come?

• B physics and neutrino experiments have produced
  the most significant discoveries since the
  LEP/SLC program
• The same two fields will probe deeper into
  flavour mixing and CP violation
• CKM physics is becoming high precision physics