Results from the B factories Steve Playfer, University of Edinburgh Annual Theory Meeting Durham, December 19th 2005 • Rough guide to B-factories for theorists • How the CKM unitarity triangle was measured • The search for hints of new physics in B decays • What happens next? Apologies for omitting spectroscopy, τ decays, charm physics ... BaBar/Belle have published >300 papers in last 4 years 1
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Results from the B factories Steve Playfer, University of Edinburgh · 2008. 10. 22. · CP violation in B decays CP violation from mixing alone is small: jq pj 6= 1 equivalent to
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Results from the B factories
Steve Playfer, University of Edinburgh
Annual Theory Meeting Durham, December 19th 2005
• Rough guide to B-factories for theorists
• How the CKM unitarity triangle was measured
• The search for hints of new physics in B decays
• What happens next?
Apologies for omitting spectroscopy, τ decays, charm physics ...
BaBar/Belle have published >300 papers in last 4 years
1
KEK-B and PEP-II
8 GeV e− on 3.5 GeV e+
Peak Luminosity 1.6 × 1034
9 GeV e− on 3.1 GeV e+
Peak Luminosity 1.0 × 1034
2
The BaBar Detector
The Belle detector looks very similar!
3
Integrated Luminosities - December 2005
Belle 514fb−1
]-1
Inte
gra
ted
Lu
min
osi
ty [
fb
0
50
100
150
200
250
300
Delivered LuminosityRecorded Luminosity
Off Peak
BaBarRun 1-5
PEP II Delivered Luminosity: 316.59/fb
BaBar Recorded Luminosity: 303.97/fb
Off Peak Luminosity: 26.80/fb
BaBarRun 1-5
PEP II Delivered Luminosity: 316.59/fb
BaBar Recorded Luminosity: 303.97/fb
Off Peak Luminosity: 26.80/fb
12/08/2005 04:16
2000
2001
2002
2003
2004
2005
BaBar 317fb−1
Both experiments expect to accumulate 1ab−1 by 2008
4
CKM Sector - before and after
HFAG 2005
Many more measurements
from B decays:
Angles of triangle
α, β and γ are
measured as well
PDG 2000
Sides of triangle only:
ε from K0 system
Vtd from B0 mixing
Vub from b→ u`ν
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
excluded at CL > 0.95
α
∆md
εK
γ ∆ms & ∆md
|Vub/Vcb|
excluded at CL > 0.95
sin 2β
sol. w/ cos 2β < 0(excl. at CL > 0.95)
α
βγ
ρ
η
excl
uded
are
a ha
s C
L > 0.95 C K M
f i t t e rEPS 2005
5
Unitarity Triangle is overconstrained!
Constraints
on angles
α, sin 2β, γ ⇒
Constraints
on sides
|Vub
Vcb
|,∆md
⇐ ∆ms, εK
6
Why do we need asymmetric B-factories?
⇒ Coherent production of B0B0 and B+B− pairs at the Υ(4S)
⇒ Asymmetric energy boosts B mesons along beam axis
Makes time-dependent CP asymmetry measurements possible!
7
CP violation in B decays
• CP violation from mixing alone is small: | qp| 6= 1
equivalent to ε in K0 system
• Direct CP violation requires two different weak and strong
phases: | AA| 6= 1
equivalent to ε′ in K0 system
• Time dependent CP violation can occur via interference
between mixing and decay: Im(λ) = Im( qp
AA
) 6= 0
This is large in the B0 system!
8
Mixing of Neutral B mesons
Time-dependent
oscillations of
an initial Bd beam
Lifetime τd = 1.528 ± 0.009ps
|ψB0(t)|2 = g+(t)|B0 > − qpg−(t)|B0 >
|ψB0(t)|2 = g+(t)B0 > −pqg−(t)|B0 >
∆md = 0.506 ± 0.005/ps
g± = 12 (e−ωHt ± e−ωLt)
ωH,L = MH,L − i2ΓH,L
9
CP violation in mixing:
Decay rate difference:
CPT and CP violation:
|q/p| = 1.029 ± 0.013 ± 0.011
sgn(Re[λ])∆Γ/Γ = −0.008 ± 0.037 ± 0.018
(Re[λ]/|λ|) Re[z] = 0.014 ± 0.035 ± 0.034
Im[z] = 0.038 ± 0.029 ± 0.025
BaBar,
PRD 70,
012007 (2004)
10
Time Dependent CP violation
ACP (f) =Γ(B0 → f) − Γ(B0 → f)
Γ(B0 → f) + Γ(B0 → f)= S(f) sin∆mt−C(f) cos ∆mt
S =2Im[λ]
1 + |λ|2C =
1 − |λ|2
1 + |λ|2λ =
q
p
A
A
Unmixed
Mixed
arbi
trar
y sc
ale
a)
Unmixed
Mixed
b)
∆t (ps)
0
20
40
60
-5 0 5
0
20
40
60
-5 0 5
B0 tags
B− 0 tags
arbi
trar
y sc
ale
a)
B0 tags
B− 0 tags
b)
∆t (ps)
0
20
40
60
-5 0 5
0
20
40
60
-5 0 5
(a) perfect
(b) realistic
time resolution
For a single decay amplitude |λ| = 1, S =Im[λ], C=0
11
Belle: hep-ex/0507037
B0 → J/ψK0
0
100
200
300 q=+1q=−1
Ent
ries
/ 0.5
ps
-0.5
0
0.5
-7.5 -5 -2.5 0 2.5 5 7.5
-ξf∆t(ps)
Asy
mm
etry
sin 2β = 0.652 ± 0.039 ± 0.020
C = 0.010 ± 0.026 ± 0.036
BaBar PRL 94, 161803 (2005)
(Top: J/ψKS Bottom: J/ψKL)
-5 0 5
Evt
s. /
0.4
ps
200
-5 0 5
Evt
s. /
0.4
ps
200 tags0B
tags0 B
a)
-5 0 5
Raw
asy
m.
-0.5
0
0.5
-5 0 5
Raw
asy
m.
-0.5
0
0.5 b)
-5 0 5
Evt
s. /
0.4
ps
100
-5 0 5
Evt
s. /
0.4
ps
100 tags0B
tags0 B
c)
-5 0 5
Raw
asy
m.
-0.5
0
0.5
-5 0 5
Raw
asy
m.
-0.5
0
0.5 d)
sin 2β = 0.722 ± 0.040 ± 0.023
C = 0.051 ± 0.033 ± 0.014
12
0.0 50.0 100.0
PDG2004BABARBelle
CLEO
New Avg.
HFAG
JULY 15th 2005
Branching Ratio x 106
Charmless B Branching Fractions
CDF
η′K+η′K0
K+π+π−K0π+π−
a−1 π+K+π−π0
K∗0(1430)0π+
ηK+π−K+K−K+
ρ+ρ−ρ+ρ0
K+K−K0
ηK∗+ρ∓π±
K0π+K+π−
ηK∗0ηπ+π−
π+π−π+K∗+π−
ωρ+K+π0
ρ+π0
K+KSKS
K0π0
K∗0(1430)+π−
K∗+ρ0
K∗0ρ+K∗0π+
K+ρ−
φK∗0
φK∗+
ρ0π+φK+
K+f0(980)φK0
ηρ+
K∗0(1430)0π0
K∗+π0
ωπ+
ωK0
ωK+KSKSKS
π+π0K0ρ0
K+π+π−(NR)ηπ+
π+π− K+ρ0
K0f0(980)η′π+
φφK+ηK+
ρ0π0π0π0
K+K0
K0K0
0.0 10.0 20.0
13
Described by sum
of b→ u tree
bW- u
d}π
d u} π +
d
and b→ s(d) penguin
b
W-
dg
t
uu}}d
d+
π-
π
Beneke & Neubert
Nucl.Phys.B675:333-415,2003
Sensitivity to electroweak penguins: Buras et.al. hep-ph/0512059
0.0 12.5 25.0
HFAG
JULY 15th 2005
Branching Ratio x 106
B(B → Kπ, ππ, KK )
PDG2004
BABA R
Belle
CLEO
New Avg.
CDF
K0π+
K+π−
K+π0
K0π0
π+π0
π+π−
π0π0
K+K0
K+K−
K0K0
14
Direct CP violation in B → KπBelle PRL 93, 191802(2004)
ACP = −0.101 ± 0.025 ± 0.005
BaBar PRL 93, 131801 (2004)
)2
(GeV/cESm5.2 5.22 5.24 5.26 5.28 5.3
2
200
400 a)
)2
(GeV/cESm5.2 5.22 5.24 5.26 5.28 5.3
Asy
mm
etry
-0.1
0
0.1
)2
(GeV/cESm5.2 5.22 5.24 5.26 5.28 5.3
Eve
nts
/ 2.5
MeV
/cA
sym
met
ry
-0.1
0
0.1 b)
ACP = −0.133 ± 0.030 ± 0.009
15
+1.0
0.0
-1.0
CP Asymmetry in Charmless B Decays
HFAG
JULY 15th 2005
PDG2004
BABARBelle
CLEO
New Avg.
CDF
K+K
SK
K+K
−
K+
π+π−
π+
K+π−
π0
K+π
+π−
ρ+ρ
0
ρ+π
0
ρ0 π
+
K+ρ−
K∗+ρ
0
K∗0 ρ
+
K∗+π−
ωπ
+
ωK
+
φK
∗+
φK
+
φK
∗0
ηK∗0
ηρ+
ηπ+
ηK∗+
ηK+
η′ π
+
η′ K
+
π0 π
0
π+π
0
K+π
0
K0 π
+
K+π−
s``sγ
K∗ γ
Only ACP (B → K±π∓) is significant so far ...
16
α− αeff from isospin
analysis of B → ππ
Gronau & London (1990)
S(ππ) = sin(2αeff )
C(ππ) = −ACP ∝ sin δ
No penguins:
C = 0, α = αeff
Measurement BaBar Belle
BF (π+π−) × 10−6 5.5 ± 0.4 ± 0.3 4.4 ± 0.6 ± 0.3
BF (π+π0) × 10−6 5.8 ± 0.6 ± 0.4 5.0 ± 1.2 ± 0.5
BF (π0π0) × 10−6 1.2 ± 0.3 ± 0.1 2.3 ± 0.5 ± 0.3
S(π+π−) −0.30 ± 0.17 ± 0.03 −0.67 ± 0.16 ± 0.06
C(π+π−) −0.09 ± 0.15 ± 0.04 −0.56 ± 0.12 ± 0.06
C(π+π0) −0.01 ± 0.10 ± 0.02 +0.02 ± 0.08 ± 0.01
C(π0π0) +0.12 ± 0.56 ± 0.06 +0.44 ± 0.53 ± 0.17
17
α from isospin analysis of B → ρρ
There are some advantages to using ρρ:
• BF (ρ0ρ0) � BF (ρ+ρ−) so penguins are small
• B0 → ρ+ρ− is > 95% longitudinally polarized
Measurement BaBar Belle
BF (ρ+ρ−) × 10−6 23 ± 2 ± 2 29 ± 5 ± 4
BF (ρ+ρ0) × 10−6 23 ± 6 ± 6 32 ± 7 ± 6
BF (ρ0ρ0) × 10−6 < 1.1
S(ρ+ρ−) −0.33 ± 0.24 ± 0.11 +0.09 ± 0.42 ± 0.08
C(ρ+ρ−) −0.03 ± 0.18 ± 0.09 0.00 ± 0.30 ± 0.10
C(ρ+ρ0) −0.19 ± 0.23 ± 0.03 0.00 ± 0.22 ± 0.03
Eventually can measure S(ρ0ρ0) as well as C(ρ0ρ0)
18
Dalitz analysis of B → πρ
Do a time-dependent
analysis of the
π+π−π0 Dalitz plot
Snyder & Quinn (1993)
A3π = f+A+ + f−A
− + f0A0
where + − 0 is the ρ charge
Sensitivity is in
interference regions 0
5
10
15
20
25
30
0 5 10 15 20 25 30
s+ (GeV2/c4)
s –
(G
eV2 /c
4 )
0
1
2
3
4
5
22 23 24 25 26 27
Interference
√s0 = 1.5 GeV/c 2
√s+
= 1.
5 G
eV/c
2
√s– = 1.5 GeV/c2
|A3π(∆t)|2 ∝ |A3π|2 + |A3π|
2
±(|A3π|2 − |A3π|
2) cos(∆md∆t) ±2Im[A3πA3π] sin(∆md∆t)
19
Summary of α measurements
Combination of all
three modes gives
the best constraint:
α = (99+12−9 )◦
Agrees with CKM fit
using other measurements
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80 100 120 140 160 180
B → ππB → ρπB → ρρ
CombinedCKM fit
α (deg)
1 –
CL
WACK Mf i t t e r
LP 2005
20
Measuring γ with B → D(∗)K(∗)
All methods use interference between tree diagrams b→ u(sc) and
b→ c(su). The ratio of the diagrams rB depends on the method.
• GLW method: B− → DCPK− with DCP → fCP
Large rate but small interference because rB � 1
• ADS method: B− → D0K−, D0 → K+π− (DCS)
and B− → D0K−, D0 → K+π− (Cabibbo-favoured)
Interference is large but DCS rate is small
• Dalitz method: B− → D0K−, D0 → Ksπ+π−
Interference term comes from D0 Dalitz plot analysis