Physics 222 UCSD/225b UCSB
Lecture 7
Mixing & CP violation (3 of 3)
Today, we focus on how to measure things, and what
the present knowledge is from the combination of
theory and experiment.
Take 2 sources as references:
David MacFarlane at SSI 2002
Soeren Prell at Lepton-Photon 2009
CKM Matrix Element Magnitudes
Vud
eν
n
e-
Vus
ν
K
π
p
eν
Vcd
D
π
Lepton Photon 2009
eν
Vcs
D
B
π
Vcb
Bd
K
Vtd
Bd
Vub
Vts
Bd Bs
eν
Vtb
Bs b
Expt. Status of the CKM Matrix (S.Prell)
eν
D
W
t
2
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Why does this matter?
Heavy Quark Symmetry predicts that the B -> D* transition
in B -> D* l nu has trivial form factor for the part of phase
space when the D* is at rest in the B restframe.
However, this also leads to minimal pT for the slow pion
in the D* -> D pi decay.
|Vcb| is theoretically most accurately extracted from
experimental data where it is experimentally most difficult.
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Luminosity accumulated by Belle reached 1000/fb
on November 29th 2009.
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





s




β from b →(cc) s decays
Theor. clean measurement of |S| = sin2β with B → J/ψ K0,
ψ(2S)KS, ηcKS, & χc1KS by BaBar and Belle
J/ψ K*,
S

0
.
6
7
2

0
.
0
2
3
W
A
C

0
.
0
0
4

0
.
0
1
9
W
A
BaBar, PRD 79,072009 (2009)
statistically limited
S

0
.
6
8
7

0
.
0
2
8

0
.
0
1
2
C

0
.
0
2
4

0
.
0
2
0

0
.
0
1
6
Lepton Photon 2009


(
2
1
.
1

0
.
9
)
Expt. Status of the CKM Matrix (S.Prell)
22
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Lepton-photon 2009
Dalitz analysis now clearly dominates the precision.
 
(
7
5
1
2
)
o
U
T
F
i
t
Basic idea:
b -> u transition with c-bar quark from virtual W
interferes with b -> c transition,
IFF one chooses a decay of the D meson that is common for
D and anti-D meson.
The resonance structure then provides the CP conserving
“phase analyzer” to measure gamma from the interference.


0

B
:
D

K
S
Poluektov
@ EPS’09



0

B
:
D

K
S
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Global CKM Fit
Other
AllCKM
constraints
angles
•
Consistency of angles
 89.0

4.4 o
-4.2
 21.10.9
o
 7512
o






1
8
5
1
3


o
•
Consistency of angles and sides
from global fit
– Overall good fit (CKMFitter:
global p-value 45%)
– ~2σ tension between sin2β
and εK / Vub
• correction to εK will make
it worse (Buras,

0
.
0
2
5
Guadagnoli, PRD78,
U
T
F
i
t
:
0
.
1
5
4

0
.
0
2
2
C
K
M
F
i
t
t
e
r
:
0
.
1
3
9
0
.
0
2
7
033005 (2008))

0
.
0
1
6

0
.
3
4
2

0
.
0
1
4

0
.
3
4
1
0
.
0
1
5


Lepton Photon 2009


Expt. Status of the CKM Matrix (S.Prell)
29
Future directions
• Ever more precise measurement of:
– sin2 from J/ Ks
–  from Dalitz analysis
• Measurements of processes that only occur at
2nd order weak interaction in standard model
– B -> s l+ l– B -> s nu nubar
• Measurements of helicity suppressed decays
– B to mu+mu-
• CP violation in the Bs system






s




βs from Bs → J/ψ Ф decays
D0 and CDF measure βs with angular dependent
fit to decay time distributions of Bs → J/ψ Ф
New physics
in BsBs mixing
CDF/PHYS/BOTTOM/CDFR/9787, DØ Note 5928-CONF
•
•
– Simultaneous fit for ΔΓs and βs
SM predicts βs very small (~0.02)
– sensitive to new physics in Bs mixing
Prospects
– D0 and CDF working on updates with 2x
samples
– LHCb sensitivity with 0.5 fb-1: σ(βs) = 0.02
Lepton Photon 2009
Expt. Status of the CKM Matrix (S.Prell)
31
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