Flying B’s
… and what they teach us
William T. Ford
University of Colorado
21 April 2006
Physics accessed via tB
 Some history of B lifetime measurements
 Impact on the CKM matrix
 Time evolution of B0 decay, B0-B0 mixing

measurements
CP violation



Precision b (sin2b)
a, present and prospective
g, present and prospective
 Sensitivity to new physics




Global constraints
SUSY
Overlapping angle measurements: b from bqqs
Charged Higgs
 Ideas for next generation collider
2
SLAC and PEP
 PEP: 29 GeV

(1980-~1986)
PEP-II: 10.58
GeV (1999-)
MAC
Mark II
BaBar
3
First B lifetime measurements
MAC
JADE (1982) <1.4 ps
(MAC (1982) 1.4  1.0 ps)
MAC (1983) 1.8  0.6  0.4 ps
MKII (1983) 1.20+0.45-0.36  0.3 ps
 High acceptance, low bias (low resolution)
 Excellent muon acceptance
 10-layer drift chamber


Differential sense wire pairs (no R-L ambiguity)
R(min, max) = (12, 45) cm
4
MAC Collaboration
5
Early 80’s B physics
 ’s discovered, 1977
 |Vub/Vcb| < 0.15
 Exclusive decays
CLEO
Pelectron (GeV/c)
Pelectron (GeV/c)
Sliverman, LepPho81
Stone, LepPho83 (PRL 50, 881 (1983))
6
Finding B’s without reconstructing them
 Thrust axis for e+e-bb approximates the b(b) momentum



direction
Massive B  high-pT lepton
Signal is b  Xmn, b  Xen
BG from b  c cascades, decay and punch-through
MAC muons
(b )c  m,
, K  m, fake m
bm
PRL 50, 2054 (1983)
7
Lepton impact parameter





Extrapolate lepton track to POCA to beam center
Beam size 400x100 mm
Measurement error on d = 500-1000 mm
d/tb from b decay ~ 100 mm/ps
Measurement depends on sqrt(N)
8
tb from lepton impact parameter




fb(m) = 0.72(8), fb(e) = 0.63(7)
a = 0.45 (vs 0.15 for c)
dc 20 mm, dbg  25 mm
From resolution-weighted ave.:
m
e
tb = 1.8  0.6  0.4 ps
9
Mark II tb measurement
 Large main drift chamber
 Vertex drift chamber
 Lepton selection:


b: pT > 1 GeV, p> 2 GeV
(purity 808%)
c: pT < 1 GeV, p> 3 GeV
104 evts
b  Xln
208 evts
c  Xln
 From fit to IP distributions
with tb free, tc constrained to
WA:
control
hadrons  Xl
tb = 1.20+0.45-0.36  0.3 ps
10
Impact on the CKM matrix
Quark flavor transmutations
t
Flavor-changing neutral currents (FCNC) occur only indirectly via loops.
M. Kobayashi, T. Maskawa, Prog. Theor. Phys. 49, 652 (1973)
12
CKM circa 1983
tb  surprisingly restricted range for third column/row couplings
S. Stone, LepPho83
s3~s2, d g
13
Hierarchical expansion of CKM
(1983)
phases
magnitudes
d
s
d
b
u
u
c
c
t
t
s
b
14
Inclusive B hadron lifetime, 2002
15
Modern B meson, baryon lifetimes
2002 summary
2005 world averages:
16
Vub/Vcb from semileptonic B decays
 Lepton endpoint in inclusive

BXln
Trade off theoretical,
experimental uncertainties.
BaBar
Method of Leibovich,
Low, and Rothstein –
weight method-less
shape function
dependent
mX cut
17
Time evolution of B0 decay, B0-B0 mixing
measurements
B0 weak eigenstates and time evolution
 M(B) = 5.28 GeV



many decay channels open
most not CP eigenstates
 G2  G1  G
19
First B0-B0 mixing measurements
 Time-integrated ratio of like/opposite sign lepton pairs
 With mixture of Bd, Bs, cmeas = fd cd + fs cs
x =Dm/G
r =G(B  B  X)/
G(B  X)
c=r/(1+r)
ARGUS: one fullyreconstructed sameflavor event
W. Schmidt-Parzefall, LepPho87
20
BaBar detector
1.5T
solenoid
DIRC (PID)
144 quartz bars
11000 PMs
e- (9GeV)
Instrumented Flux Return
Iron / Resistive Plate
Chambers or Limited
Streamer Tubes (muon /
neutral hadrons)
EMC
6580 CsI(Tl) crystals
e+ (3.1GeV)
Drift Chamber
40 layers
Silicon Vertex Tracker
5 layers, double sided
strips
21
B meson pairs from boosted (4S)
0
tag
B
e
-
e+
K+
(4S)
e+
B
B
t=0
0
flav final
0
flav
D+
Dt
K+
+
m-
n
states measure mixing, calibrate tagging
22
Flavor Oscillations
mixed
asymmetry mixed/unmixed
unmixed
unmixed
maximum mixing
½ period ~ 6 ps
~ 4 B-meson lifetimes
Current Dmd
measureents
 Time-dependent

results from LEP and
asymmetric B
factories
WA:
Dmd = 0.507  0.005ps -1
24
A/s(A) = 3.5;
probability of
fluctuation
~0.5%
G. Gomez-Ceballos, FPCP06
25
The Unitarity Triangle
V is a complex unitary matrix:
determined by 4 real parameters
• sine of Cabibbo angle
  0.22
• b  c transition
(in units of 2)
A  0.83
• 2 coordinates
of the apex of the
Unitarity Triangle
~24o
Unitarity
Triangle
~62o
UT determination from sides, CPV in K0S
 Vub, Vcb from

semileptonic B
decays
Vtd from B0-B0 mixing
 Theory errors
cancel in Dmd/Dms
27
CP violation
29
Decay to a CP eigenstate
0
tag
B
e-
t=0
e+
K+
(4S)
e
-
+
0
CP
B
K S0
Dt
J/
+
mm+
CP eigenstate
30
31
B0-B0 mixing factor in CPV
32
33
Tagging and Dt resolution
tagging
vertex errors
efficiency
~ 97%
~1.5 ps
σ(Δz)
[cm]
Δt resolution function
B0 tag
B0 tag
shape from
signal MC,
parameters
from data
effective efficiency 30%
measured on data
(Δtmeas-Δttrue)/σ(Δt)
34
w,Dw =mistag rate, B-B difference
resolution
35
A Precision Measurement
PRL 94, 161803 (2005), (hep-ex/0408127)
36
History of sin2b measurements
Present
WA
Present
CKM fit
BABAR 0.722±0.040±0.023
Belle 0.652±0.039±0.020
37
Measurement of a: CPV in charmless modes
Interference of suppressed
b  u tree decay with mixing

( , )
G(b  u n )
CPV in B 0 
 ,  , ,
a = 2
g = 3
(0, 0)
W
B -B
mixing
b = 1
t B and G( b  c n )
3rd component:
sizable Penguin
diagram
0
b
B0
d
b
d
b
d
B0
(1, 0) 
d
u
B d
0
0
u
W
u ,c ,t g
d
W
t
t
W
b
d

u
u +
d
38
-
+
B0
Taming the Penguins: Isospin Analysis
Gronau and London, Phys. Rev. Lett. 65, 3381 (1990)
 The decays B +-,+0,00 are related by SU(2)


(similarly for )
Isospin relations between amplitudes A+-, A+0, A00
 Central observation is that  states can have I = 2 or
0, but gluonic penguins only contribute to I = 0 (DI =
½ rule)

+0 is pure I = 2, so only tree amplitude  |A+0| = |A-0|
 = 2(aeff - a )

Need to measure:
C+-, C00, A00, A+0
An effective isospin
00
analysis
requires
A
~ 00
and A very large,
or very small!
39
Measuring a in B → 
Best mode for a:
~100% longitudinally polarized
• quasi-two-body approx Ok
• no → ignore interference
2
• null search for 00
d N
 f L cos 2 1 cos 2  2 + 14 (1 - f L ) sin 2 1 sin 2  2
d cos1d cos 2
while 00 is of order 30% of +00 is smaller than 4% of +- (90%CL)
With reasonable theoretical
assumptions this mode
provides
the present best
constraints on a
BABAR, PRL 94,
131801 (2005)
a=100°13°
79°< a <123° @ 90% CL
PRL 95, 041805 (2005) 40
Summary of constraints on a
BABAR only
Mirror
solutions
disfavored
From combined
 ,  ,  results:
+10
a = 103 -9 


o
CKM indirect constraint
o
+
13
fit: a = 98 -19


A good example of new
analysis ideas emerging
with data in hand
41
Projections for a measurement
With a 1 ab-1 sample:
o Will improve errors on S and C from B  
o Should observe B  00
o Confirm that “mirror solution” in B   is disfavored
by Dalitz analysis in B  π
Projection
2 ab -1
3 scenarios
for 00 BF
o Expected
value
o +1s
o -1s
42

Measurement of g
( , )
 Given by the phase
a = 2
g = 3
(0, 0)
b = 1
difference between
Vub and Vcb
(1, 0) 
u
  look for interference between
bc and b  u
 B DK, D*K, DK*, with
 D, D  common final state:
 D(*)CP (GLW)
 D, D K+- (ADS)
 D, D Ks Dalitz (GGSW)
b
W
B u
-
B
W-
u
s
c
u
b
-
-
K (*) -
D (*)0
u (*)0
cD
s (*) K
u
43
Dalitz plot analysis for gamma
Idea: Increase B decay interference through D decay Dalitz plot
Method first shown by Belle
From combined
analysis:
o
+23

g = 51 -18


B +  D (*)0  KS0 + -  K +
Indirect constraint:
o
+7 

g = 57 -13


Needs good Dalitz model:
CLEOc
44
Projections for g measurement
(deg)
Error on
g
Example of impact of
value for rB on the
error on g, using the
Dalitz
method in BABAR
Error as a function of
integrated luminosity for rB=0.1
• GGSZ
• GGSZ + GLW
• GGSZ + GLW + ADS
rB = 0.1
BABAR
2008
BABAR+
Belle
2008
projected systematic error
Error as a function of rB
Luminosity
(ab-1)
45
Summary of CP violation in B0(B0)
2008: ~2%
2008: 10o
a
sin2b
g
2008: 5-10o
cos2b
46
Angle measurements only
Comparable UT precision from
CPV in B decays alone
47
Summary of Unitarity Triangle constraints
Overconstrained.
Search for New
Physics as
correction to CKM
48
Sensitivity to new physics
Search for New Physics with Heavy Flavor
How much room does the UT now allow for (any) new physics?
( DMBd ) = CBd ( DMBd
)
SM
UT team: L. Silvestrini, LP05
ACP (J / KS0 ) = sin 2 ( b + Bd
)
SM solution
CBd=1 & Bd=0
Non –SM solution now
excluded by Semileptonic
asymmetry (Asl)
from BaBar & D0
•New sources of CP violation in bd & sd are strongly constrained.
•The bs transitions are much less constrained- possible probes:
•Gluonic penguins bsg :: rates, direct CPV, “the sin2bpenguin” test
• Bs mixing: Dms, DGs,
•EW radiative bsg ::rates, direct CPV, photon polarization.
•EW radiative bsll :: rates, direct CPV, AFB(q2), polarization effects,..
50
SUSY effective couplings
 superCKM basis: diagonal in flavors and quark masses
 But off-diagonal squark masses  induced FCNC terms
(“mass insertion” approximation):
B Factory
LHC
Squark mass matrix (d sector)
Take
~ 350 GeV
51
SUSY in bs decays
 bs (23) couplings in time-
(d )
d
bs hk
e.g.,
(d )
d
23 RL
dependence S, C parameters:
DS = S – sin2b
bsqq
52
CP Violation in “s-Penguin” Modes
Reference mode: Tree dominance
b
0
B
c
c
s
d
W-
d
J/
0
K
s
d
d
s
t,c,u
K0
Penguin dominance
W-
b
B
s
g
g
u, d
internal penguin
s
s
s
u, d

b
B
K
u, d
t,c,u
s
s
W-

K
u, d
flavor-singlet penguin
53
T-D Analyses in ’Ks and KsKsKs
804±40 signal events
take advantage
of the small
beam size
in the
transverse plane
88±10 signal events
54
55
sin2b consistency measurements bqqs
 Naïve ave. of s-



penguin modes 2.4s
below precision value
from b  ccs modes
No evidence here yet
for direct CPV
New physics may
affect different modes
in different ways
Use the pattern of
deviations to go
beyond the naïve
average
56
Deviations from Standard Model
Projected errors as a function of time
Significance of deviation
from Standard Model expectation
K*g
as a function of luminosity
f 0K S
(assuming fluctuations around
0
KSπ
present central values)
 KS
’KS
BABAR+Belle
in 2008
KKKS
0.40
Error on sine amplitude
0.35
0.30
0.25
0.20
0.15
0.05
Theory
errors
Jul-09
Jan-09
Jul-08
Jan-08
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
0.00
Number of
standard deviations
0.10
integrated luminosity (/fb)
Discriminating Among NP Models
SM
Wilson coefficients:
Six NP scenarios
Exploit the pattern of deviations DS in the
various modes to discriminate among different
models
Buchalla, Hiller, Nir, Raz
(hep-ph/0503151)
Three NP models, six scenarios:
• NP only in the Z0-penguin coupling
• NP in chromo-magnetic operator
S
Exclusion vs luminosity
• NP in Kaluza-Klein gluon excitations
FCNC: b → s g
The transition b  s γ
has been heavily studied by
CLEO
then by BABAR and Belle
in a variety of ways
• fully inclusive
• exclusive (B → K*g)
• semi-inclusive
So far all measurements are
consistent with SM predictions
(typical errors: 10%)
photon energy
(semi-inclusive analysis)
expect improvements
towards 5% error
by 2008
this mainly constrains “LR” mass insertions
59
Search for B+t+nt
~10-4 in SM
B decay constant
Helicity suppressed
(much more for e,m)
e+
BB-X
 For B Xnknown EB, mB, small pB

 small error for missing mass (mn=0)
(4S)
B+
nt
ne
nt
B+t+nt, t+e+nent
 Reconstruct one B (Btag) in semileptonic or hadronic
b  c mode
 Select candidates for 6 tau decay modes (81% of Gtot)
 Any unassigned calorimeter energy (Eextra) comes
mostly from combinatorial background
60
B+t+nt (BaBar, preliminary)
enn
mnn
n
232 106 B pairs
Data
Background MC
Signal MC
mislep
n
a1 n
BtagD*ln
Find 150 evts/130.9
expected bkg
BF(B+t+nt) =
(1.28+1.15-1.08)10-4
(<2.8 10-4, 90% CL)
Combine with previous Btag  hadronic,
BF(B+t+nt) = (1.28+0.95-0.90)10-4 (<2.6 10-4, 90% CL)
fB < 0.34 GeV, 90% CL, (lattice prediction is fB=0.200.03 GeV)
61
B+t+nt (Belle, preliminary, FPCP06)
447 106 B pairs
BtagD(*)[,,a1,Ds(*)] 680k tags, 55% pure.
5 t decay modes
Find 21.2+6.7-57 net signal events
from fit to a sample of 54 events.
+ o.18
-4
BF( B +  t + n t ) = 1.06 +-00..34

10
28- 0.16
4.2s significance
+ 0.020
f B = 0.176+-00..028
023- 0.018 GeV
Hep-ex/0604018
62
B+t+nt
Or given CKM, constrain SUSY
parameters
Β( B  tn )  2.6 10-4 @ 90%C.L.
-4
-4
1.8 10 +0.18
@ 90%C.L.
= 1.06+0.34
10
-0.28
-0.16
Β( B  tn ) / DM Bd constrains Vub
2
V td
2
tanb = ratio of VEVs in 2 Higgs
doublet model
63
Novel ideas for e+e- super-B factory @ 1036 – J. Seeman
P. Raimondi
Requirements:
1) Asymmetric energies
(4.5x6.2) (4x7) (3.5x8) (3 x 9)
2) Small energy spread at the IP (<10 MeV)
3) Low power consumption: ~100 MW
4) Control beam-beam blowup to avoid long
1.5 GeV Linac
2 GeV Linac
1.5 GeV Linac
damping times
Damping Rings
2 GeV
At least 4 different schemes are
being considered
Workable parameter set contains:
- ILC damping ring,
- ILC bunch compressor,
- ILC Final Focus
e- Gun
e+ Gun
Linac
Linac
Several workshop has been dedicated to the design and more
on the way
64
Conclusions
 The B lifetime revealed a striking hierarchy of quark



weak couplings
Because time evolution is measurable we have
established the incorporation of CPV into the theory
of universal weak interaction
Heavy flavor decays provide a window
complementary to the energy frontier in the detection
and characterization of new physics
Large improvements can be anticipated in these
measurements
65
Backup slides
67
68
MAC event display
 An e+e-qq event with a muon
69
MAC tracking event display
 10-layer drift chamber
 Differential sense wire pairs
(no R-L ambiguity)
 R(min, max) = (12, 45) cm
70
Bs Mixing -Dms
b
Vtb W
t
d(s)
Vtb
2
GF2 mW2 S (mt2 / mW2 )
2
*
Dmq =
mBq f Bq BBq VtqVtb
2
6
b
t
Vtd W Vtd(s)
d(s)
Dms mBs f BBs
=
Dmd mBd f BBd Vtd
2
Bs
2
Bd
Vts
2
2
=
Vts
mBs 2

mBd
Vtd
A key element of the CKM test, as well as searches for New Physics
Up until a few weeks ago limits: Δms> 14.4 ps-1
SM prediction from UT fits: Δms = 18.3 + 6.5 -1.5 ps-1
Interpretation power dominated by accuracy of LQCD
input:
With Dmd / Dms SM value &  = 1.21  0.04  0.05
= |Vts|/|Vtd| at ~5 % theoretical uncertainty,
With Dmd = 0.509  0.004 ps-1 @ ~1%
& fBd2 BBd = (228  30  10 MeV)2 from LQCD
|Vtd| only at 15% accuracy- all theory limited
71
2
2
Measuring Dms::News from TEVATRON
D0: Reconstructs BsD(*)sln& tags its initial
flavor using the other Bmwith eD2 ~ 2.4%
3.8% (5% ) probability for
Dms = 
& 15% probability for Dms=19 ps-1
72
Measuring Dms: CDF
See J. Pierda
With opposite side tagging
eD2  1.5 % & st ~87-200 fs
Now have added same side tagging with eD2 = 4.0+0.9-1.2 %
Can not use Bd to evaluate and validate performance.
Other approaches used
For a total of eD2  5.5%
73
An MSSM analysis of b->s observables- ( L. Silvestrini- LP2005) -
74
75
SUSY in bd, bs decays
B0-B0 mixing
(d )
d
bs hk
e.g.,
(d )
d
23 RL
 Mixing effect would appear in

the generic NP analysis
bs (23) couplings in timedependence S, C parameters:
DS = S – sin2b
bsqq
76
Mixing and b bounds on SUSY ( (d13d )LL )
Constraints from
 Dmd
 sin2b
 sin2b&cos2b
 All
B physics is sensitive
to small SUSY
contribution: (d13d )LL  1
Ciuchini et al., hep-ph/0512141
77
Two examples of constraints
on the parameter space
for specific NP models
Limits on m(H+) in the MSSM
from Br( B  tn )
H+
90% Upper Limit on
BR( B  t n )
B  t n : Sensitivity to NP Models
B  tn
Luminosity (fb-1)
Limits on the m(H+)-tanb
plane
in 2HDM (of type II)
from Br( B  tn )
and Br( b  s g )
78
A vision for the longer-term future?
Strong physics case
for a 1036 facility
Raimondi, Seeman
Transport
E+ source
Positrons
Make up DE
Gun
Electrons 3 GeV
IP
3 GeV
5 GeV
1 GeV
DR
Dump
o Significant technical overlap with ILC (damping rings, acceleration
sections, final focus, …)
o Appears to be possible to reach 1036 with substantially smaller
backgrounds, allowing (re-)use of existing detectors
79