CP Violation at LHCb

CP Violation at LHCb
Marcel
Merk
5‐th
Interna/onal
Symposium
on
Symmetries
in
Subatomic
Physics
(SSP2012)
June
18
‐
22,
Groningen
A
slide
of
History
• Charge
Parity
Viola/on
in
par/cle
physics
– 1964
(CCFT):
Discovered
in
neutral
Kaon
beam
“indirect
CP
viola/on”
• Also
called:
CPV
in
mixing
• Prob(K0K0)
≠
Prob
(K0K0)
|ε|=
(2.228
±
0.011
)
x
10‐3
(PDG)
– 1999
(NA48
&
KTeV):
Seen
in
Kaon
decays
“direct
CP
viola/on”
• Also
called:
CPV
in
decay
• Decay
rates
Γ(K0π+π‐)
≠
Γ(K0π+π‐)
Re(ε’/ε)
=
(1.65
±
0.26)
x
10‐3
(PDG)
– 2001
(Belle
&
Babar):
Observed
in
B
mesons
decays
“CP
viola/on
in
interference”
• Also
called:
mixing
induced
CPV
Sin2β
=
0.673
±
0.023
(PDG)
James
Watson
Cronin
Val
Logsdon
Fitch

Nobel
prize
1980
19‐6‐2012
Marcel
Merk
–
SSP2012
2
CP
Viola/on
in
the
Standard
Model
L = iψL γµ D µ ψL
Hideki
Yukawa
Peter
Higgs
Paul
Dirac
+
V (φ)
+
Yij
!
"
i
ψL φ
j
ψR
• The
Yukawa
flavour
couplings
Yij
make
the
theory
CP
viola/ng
if
they
are
complex.
• Aoer
Spontaneous
Symmetry
Breaking
the
Yukawa
terms
give
rise
to
quark
masses.
• Expressing
the
quark
flavour
eigenstates
in
mass
eigenstates
leads
to
CP
viola/ng
flavour
changing
charged
currents.
• The
origin
of
CP
viola/on
is
related
to
the
origin
of
mass
and
requires
the
existence
of
at
least
3
genera/ons
19‐6‐2012
Marcel
Merk
–
SSP2012
3
Interac/ons
between
Quarks
Cabibbo
described
“V‐A”
quark
interac/ons
with
flavour
changing
charged
currents:

quark
mixing
A = gweak Wµ+ J µ+
1
µ+
J = ψu (1 − γ 5 ) γ µ VCKM ψd
2
u,c,t
W
gweak
Nicola
Cabibbo
Makoto
Kobayashi
Toshihide
Maskawa
Kobayashi
and
Maskawa
predicted
in
1972
the
3rd
quark
genera/on
to
explain
CP‐Viola/on
within
the
Standard
Model

Nobel
Prize
2008
(shared
with
Nambu)
19‐6‐2012
Marcel
Merk
–
SSP2012
Jμ+
d,s,b
Par/cle
→An/par/cle
gweak→g*weak
9
Coupling
constants:
gweak
→
g
∙
VCKM
4
The
CKM
Matrix
VCKM

d
s
b
Vud
c
 Vcd
Vtd
t
u
19‐6‐2012
Vus
Vcs
Vts

Vub
Vcb 
Vtb
Marcel
Merk
–
SSP2012
5
The
CKM
Matrix
VCKM

d
s
b
Vud
c
 Vcd
Vtd
t
u
Vus
Vcs
Vts

Vub
Vcb 
Vtb
Wolfenstein
parametriza/on:
VCKM

1 2
λ
2

1−
λ
Aλ (ρ − iη)


−λ
1 − 12 λ2
Aλ2
Aλ3 (1 − ρ − iη) −Aλ2
1
19‐6‐2012
3
From
unitarity
(VCKM
V†CKM=1)
CKM
has
four
free
parameters:
3
real:
λ (≈0.22) , A
(≈ 1),
ρ
1
imaginary:
iη
Par/cle
→
An/par/cle:
Vij
→
Vij*
=>
1
CP
Viola/ng
phase
Marcel
Merk
–
SSP2012
6
The
CKM
Matrix
VCKM

d
s
b
Vud
c
 Vcd
Vtd
t
u
Vus
Vcs
Vts

Vub
Vcb 
Vtb
Wolfenstein
parametriza/on:
VCKM

−iγ
|Vud |
|Vus |
|Vub |e
 −|Vcd |
|Vcs |
|Vcb |
|Vtd |e−iβ −|Vts |eiβs |Vtb |
19‐6‐2012


Marcel
Merk
–
SSP2012
7
Observing
CP
Viola/on
in
B
decays
• CP
Viola/on
occurs
in
interference
of
two
quantum
amplitudes
that
have
a
different
CP
odd
(as
well
as
CP
even)
phase
– Use
the
phenomenon
of
B‐B
mixing:
– Interference
of
direct
decay
and
decay
via
mixing
leads
to
CP
viola/on.
Standard
Model:
• B0‐B0
phase
ϕd
=
arg(Vtd)
=
2β
• Bs‐Bs
phase
ϕs
=
arg(Vts)
=
2βs
19‐6‐2012
Marcel
Merk
–
SSP2012
8
Observing
CP
Viola/on
in
B
decays
• CP
Viola/on
occurs
in
interference
of
two
quantum
amplitudes
that
have
a
different
CP
odd
(as
well
as
CP
even)
phase
– Use
the
phenomenon
of
B‐B
mixing:
– Interference
of
direct
decay
and
decay
via
mixing
leads
to
CP
viola/on.
Standard
Model:
• B0‐B0
phase
ϕd
=
arg(Vtd)
=
2β
• Bs‐Bs
phase
ϕs
=
arg(Vts)
=
2βs
B0
eiϕd
fCP
B0
Bs
e iϕs B
s
19‐6‐2012
fCP

iγ
Vud
Vus Vub e
 Vcd
Vcs
Vcb
Vtd eiβ Vts eiβs Vtb
Marcel
Merk
–
SSP2012


9
Probing
new
physics
• Flavour
Physics:
indirect
search
for
new
par/cles
or
interac/ons
– Measure
CP
viola/on
in
many
B,
D
decay
modes
• All
observa/ons
should
be
consistent
with
a
single
CP
phase
– Measure
branching
rates
of
decays
that
are
suppressed
in
SM
• Look
for
interference
of
CKM
physics
with
New
Physics
– Expect
sensi/vity
for
new
physics
where
SM
amplitudes
are
suppressed:
loop
diagrams
– Measure
CP
phases
“with
tree
decays”
and
“with
loops”
“Penguin” diagram: ΔB=1
“Box” diagram: ΔB=2
b
s
19‐6‐2012
s
b
b
s
μ
μ
Marcel
Merk
–
SSP2012
10
Classifica/on
of
CP
Viola/on
Methods
@
LHCb
• Many
methods
have
been
developed
for
B
decays
• The
classifica/on
direct
and
indirect
is
no
longer
sufficient
– E.g.:
methods
with
intermediate
Charm
states
• We
use
also
experimental
classifica/ons
– “Time
dependent”
vs
“Time
independent”
methods
• Observe
CP
Viola/on
as
func/on
of
B‐decay
/me
vs
integrated
over
/me
– “Tagged”
vs
“Untagged”
methods
• Require
knowledge
of
b‐flavour
at
produc/on
or
not
• I
can’t
give
a
complete
overview
– Examples
of
several
prominent
ongoing
analyses
19‐6‐2012
Marcel
Merk
–
SSP2012
11
CP
Viola/on
Measurements
@
LHCb
• Time
Integrated
measurements:
– (1)
Direct
CP
Viola/on
in
charmless
decay
B(s)Kπ
• Interference
of
trees
with
penguins
– (2)
CP
Viola/on
in
charmed
B
decays:
B‐D0K‐
and
B‐D0π‐
• Measurement
of
“
γ with
trees”
using
ADS/GLW
method
• Time
dependent
measurements
(interference
of
mixing
and
decay):
– (3)
CP
viola/on
in
charmless
B(s)
decays
BsK+K‐
and
Bπ+π‐
• Measurement
of
“
γ
with
loops”
– (4)
CP
Viola/on
in
charmed
Bs
Decays
BsDsK
• Measurement
of
“γ
with
trees”
– (5)
CP
Viola/on
in
Bs
decays
to
CP
eigenstate
BsJ/ψ
ϕ
• Measurement
of
Bs
mixing
phase
Φs
(βs)
• A
charming
surprise:
CP
Viola/on
in
charm
– (6)
CP
Viola/on
in
two‐prong
hadronic
D0
decays
• Measurement
of
ΔACP,
difference
of
CP
viola/on
in
D0K+K‐
and
D0π+π‐
19‐6‐2012
Marcel
Merk
–
SSP2012
12
LHCb
@
LHC
19‐6‐2012
Marcel
Merk
–
SSP2012
13
Bs → D−s K+
Primary
vertex
B
Physics
@
LHCb
Bs
btag
~1
cm
Design:
• LHCb
event
rate:
~30
MHz
• 1
in
160
is
a
b‐b
event
• 1012
b‐b
events
per
year
19‐6‐2012
K+
Ds
K+
Kπ-
• Background
Suppression
• Flavour
tagging
• Decay
/me
measurement
• Vertex
and
momenta
reconstruc/on
• Par/cle
iden/fica/on (π,
К,
μ,
е,
γ)
• Trigger
Marcel
Merk
–
SSP2012
14
Vertex
Topology
Vertex
Locator
19‐6‐2012
Marcel
Merk
–
SSP2012
15
Momentum
and
Mass
Reconstruc/on
Trigger
Tracker
19‐6‐2012
Magnet
Marcel
Merk
–
SSP2012
Outer
Tracker
16
Par/cle
Iden/fica/on:
π,
K,
μ,
γ,
e
RICH
19‐6‐2012
Calorimeter
Marcel
Merk
–
SSP2012
Muon
17
23
sep
2010
19:49:24
Run
79646
Event
143858637
19‐6‐2012
Marcel
Merk
–
SSP2012
18
18
23
sep
2010
19:49:24
Run
79646
Event
143858637
19‐6‐2012
Marcel
Merk
–
SSP2012
19
19
LHCb
Running
2011
2012
1.1
†‐1
0.5
†‐1
(Expect
1.5
†‐1)
19‐6‐2012
Marcel
Merk
–
SSP2012
20
CP
Viola/on
Measurements
@
LHCb
• Time
Integrated
measurements:
– (1)
Direct
CP
Viola/on
in
charmless
decays
B(s)‐>Kπ.
– (2)
CP
Viola/on
in
charmed
decays
B‐D0K‐
and
B‐D0π‐
• Time
dependent
measurements
(interference
of
mixing
and
decay):
– (3)
CP
viola/on
in
charmless
B(s)
decays
BsKK
and
Bππ
– (4)
CP
Viola/on
in
charmed
Bs
decays
BsDs
K
– (5)
CP
Viola/on
in
Bs
decays
to
CP
eigenstate
BsJ/ψ φ
• CP
Viola/on
in
mixing
– (6)
A
charming
surprise
19‐6‐2012
Marcel
Merk
–
SSP2012
21
(1)
Direct
CP
Viola/on
with
B(s)
Kπ
γ
+
• Interference
of
trees
and
penguins
– New
physics
can
contribute
to
penguin
loop
• Sensi/ve
to
Vub
phase:
CKM
angle
γ
• Measure
the
untagged
CP
asymmetry
for
B0
and
Bs
decays:
!
"
! 0
NB→f − NB→f
+ −
B
→
K
π
"
ACP = !
B→f =
+ −
B
→
π
K
s
NB→f + NB→f
Araw = ACP + Adet + κ · Aprod
Instrumental
asymmetry
19‐6‐2012
(The
correc/on
factor
is
~1%,
measured
from
data)
Mixing
dilu/on
/mes
produc/on
asymmetry
Marcel
Merk
–
SSP2012
22
(1)
Direct
CP
Viola/on
with
B(s)
Kπ
Bs → π K
PRL
108.201601
ACP
=
0.27
±
0.08
±
0.02
First
3σ
evidence
for
CP
asymmetry
in
Bs
decays
19‐6‐2012
3000
LHCb
2500
(a)
2000
0.35
†‐1
1500
1000
B0 → K+ π-
500
05
400
350
300
250
200
150
100
50
0
5
3000
LHCb
2500
(b)
2000
1500
1000
LHCb
(c)
0.35
†‐1
Bs0 → K+ π-
5.2
5.4
5.6
5.8
+
K "! invariant mass (GeV/c2)
Marcel
Merk
–
SSP2012
400
350
300
250
200
150
100
50
0
5
0
B #K!
0
Bs#K!
0
B #!!
0
Bs#KK
B#3-body
Comb. bkg
B0 → K- π+
500
05
5.2
5.4
5.6
5.8
+
K "! invariant mass (GeV/c2)
Events / ( 0.02 GeV/c2 )
ACP
=
‐0.088
±
0.011
±
0.008
Most
precise
and
first
5σ
observa/on
of
CP
viola/on
in
a
hadronic
machine
Events / ( 0.02 GeV/c2 )
PRL
108.201601
Events / ( 0.02 GeV/c2 )
B0 → K π
Events / ( 0.02 GeV/c2 )
+
γ
5.2
5.4
5.6
5.8
"
K !+ invariant mass (GeV/c2)
LHCb
(d)
Bs0 → K- π+
5.2
5.4
5.6
5.8
"
K !+ invariant mass (GeV/c2)
23
CP
Viola/on
Measurements
@
LHCb
• Time
Integrated
measurements:
– (1)
Direct
CP
Viola/on
in
charmless
decays
B(s)‐>Kπ.
– (2)
CP
Viola/on
in
charmed
decays
B‐D0K‐
and
B‐D0π‐
• Time
dependent
measurements
(interference
of
mixing
and
decay):
– (3)
CP
viola/on
in
charmless
B(s)
decays
BsKK
and
Bππ
– (4)
CP
Viola/on
in
charmed
Bs
decays
BsDs
K
– (5)
CP
Viola/on
in
Bs
decays
to
CP
eigenstate
BsJ/ψ φ
• CP
Viola/on
in
mixing
– (6)
A
charming
surprise
19‐6‐2012
Marcel
Merk
–
SSP2012
24
(2)
The
GLW/ADS
method
with
BDK
and
BDπ
• Interfere
decays
bc
with
bu
to
final
states
common
to
D0
and
D0
0
A(B − → D K − )
A(B − → D0 K − )
19‐6‐2012
= rB eiδB e−iγ
color
suppression
Marcel
Merk
–
SSP2012
25
(2)
The
GLW/ADS
method
with
BDK
and
BDπ
• Interfere
decays
bc
with
bu
to
final
states
common
to
D0
and
D0
0
A(B − → D K − )
A(B − → D0 K − )
= rB eiδB e−iγ
color
suppression
GLW
method:
fD
is
a
CP
eigenstate
common
to
D0
and
D0:
fD=
K+K‐,
π+π‐,…
Measure:
B→D0K,
B
→
D0K,
B→
D1K
• Large
event
rate;
small
interference
Gronau,
London,
Wyler:
Phys.
Le?.
B
265,
172
(1991)
D0K–
B– r ei(δB −γ)
B
D0K–
Observables:
! −
"
! +
"
−
+
Γ B → fD K − Γ B → fD K
ACP + =
Γ (B − → fD K − ) + Γ (B + → fD K + )
! −
"
! +
"
−
+
Γ B → fD K + Γ B → fD K
RCP + =
Γ (B − → D0 K + )
19‐6‐2012
Marcel
Merk
–
SSP2012
fDK–
Unknown
phases:
Weak
phase
γ
Strong
phase
δB
26
(2)
The
GLW/ADS
method
with
BDK
and
BDπ
• Interfere
decays
bc
with
bu
to
final
states
common
to
D0
and
D0
0
A(B − → D K − )
A(B − → D0 K − )
= rB eiδB e−iγ
color
suppression
ADS
method:
Use
common
flavour
state
fD=(K+
π –)
Note:
decay
D0→K+π– is
double
Cabibbo
suppressed
• Lower
event
rate;
large
interference
Atwood,
Dunietz,
Soni:
Phys
Rev
Le?
78,
3257
(1997)
Phys
Rev
D
63,
036005
(2001)
D0K–
B– r ei(δB −γ)
B
D0K–
Observables:
! −
"
! +
"
−
+
Γ B → f D K − Γ B → fD K
!
"
AADS =
−
−
+
+
Γ (B → fD K ) + Γ B → fD K
! −
"
! +
"
−
+
Γ B → fD K + Γ B → fD K
"
RADS = ! −
−
Γ B → fD K + Γ (B + → fD K + )
19‐6‐2012
Marcel
Merk
–
SSP2012
rD eiδD
fDK–
Unknown
phases:
Weak
phase
γ
Strong
phase
δB
, δD
27
(2)
The
GLW/ADS
method
with
BDK
and
BDπ
Observe
ADS
mode
B‐[π‐K+]D
K‐
with
10
σ
significance
B‐[π‐K+]D
K‐
B+[π+K‐]D
K+
B‐[π‐K+]D
π‐
B+[π+K‐]D
π+
arXiv:1203:3662
LHCb:
1.0
P‐1
BDK
BDπ
BDK
shows
4.0
σ
evidence
of
CPV:
BDπ
shows
2.4σ
hint
of
possible
asym:
AADS(K)
=
‐0.52
+‐
0.15
+‐
0.02
RADS(K)
=
0.015
+‐
0.002
+‐
0.000
AADS(π)
=
0.14
+‐
0.06
+‐
0.01
RADS(π)
=
0.0041
+‐
0.0003
+‐
0.0001
19‐6‐2012
Marcel
Merk
–
SSP2012
28
CP
Viola/on
Measurements
@
LHCb
• Time
Integrated
measurements:
– (1)
Direct
CP
Viola/on
in
charmless
decays
B(s)‐>Kπ.
– (2)
CP
Viola/on
in
charmed
decays
B‐D0K‐
and
B‐D0π‐
• Time
dependent
measurements
(interference
of
mixing
and
decay):
– (3)
CP
viola/on
in
charmless
B(s)
decays
BsKK
and
Bππ
– (4)
CP
Viola/on
in
charmed
Bs
decays
BsDs
K
– (5)
CP
Viola/on
in
Bs
decays
to
CP
eigenstate
BsJ/ψ φ
• CP
Viola/on
in
mixing
– (6)
A
charming
surprise
19‐6‐2012
Marcel
Merk
–
SSP2012
29
Time
Dependent
CP
Viola/on
B
eiφd
Bs
fCP
eiφs
B
fCP
Bs
ΓB→f (t) − ΓB→f (t)
Adir cos (∆Mt) +Amix sin (∆Mt)
! ∆Γ "
! ∆Γ "
ACP (t) =
=
∆Γ
ΓB→f (t) + ΓB→f (t)
cosh 2 t −A sinh 2 t
!
"
dir 2
A
!
"
mix 2
+ A
!
"
∆Γ 2
+ A
=1
• Extrac/on
of
and
require
flavour
tagging:
Adir
Amix
knowing
the
flavour
of
the
B‐meson
at
produc/on
19‐6‐2012
Marcel
Merk
–
SSP2012
30
(3)
Charmless
B(s)
decays
Bπ+π‐
and
BsK+K‐
+
β(s)
+
γ
(Fleisher:
Phys.Le?.B459:306‐320,1999)
A
measurement
of
“γ
with
loops”
• Sensi/vity
to
new
physics
enters
via
the
penguin
loop
• Combined
analysis
of
BKK,
Bππ
with
BKπ
- Make
use
of
U‐spin
flavour
symmetry
to
extract
common
hadronic
factors
Amix
ππ ∼ 2β + 2γ
Amix
KK ∼ 2βs + 2γ
Adir
ππ ∼ 2γ
19‐6‐2012
Adir
KK ∼ 2γ
Marcel
Merk
–
SSP2012
31
1000
LHCb
Preliminary
800
s = 7 TeV
600
Bππ
400
Events / ( 8 MeV/c2 )
Events / ( 8 MeV/c2 )
(3)
Charmless
B(s)
decays
Bπ+π‐
and
BsK+K‐
1200
LHCb
Preliminary
1000
s = 7 TeV
800
BsKK
600
400
200
0
200
5.1
5.2
5.3
5.4
5.5
0.5
LHCb
Preliminary
0.4
0.3
0
5.6
5.7
5.8
m!! (GeV/c2)
5
Raw asymmetry
Raw asymmetry
5
s = 7 TeV
0.2
0.1
0.15
0.10
5.2
5.3
5.4
5.5
5.6
5.7
5.8
mKK (GeV/c2)
LHCb
Preliminary
s = 7 TeV
0.05
0
-0.1
-0.05
-0.2
5.1
0.20
0
-0.10
-0.3
-0.15
-0.4
-0.5
LHCb‐CONF‐2012‐007
1
2
3
4
5
6
7
8
-0.20
0
9
t [ps]
Adir
ππ = 0.11 ± 0.21(stat) ± 0.03(sys)
Amix
ππ = −0.56 ± 0.17(stat) ± 0.03(sys)
0.05
0.1
0.15
0.2
0.25
0.3
0.35
(t-t 0) modulo (2 " /!ms) [ps]
Adir
KK = 0.02 ± 0.18(stat) ± 0.04(sys)
Amix
KK = 0.17 ± 0.18(stat) ± 0.05(sys)
First
(preliminary)
evidence
of
mixing
induced
CP
viola/on
seen
at
hadron
collider
(3.2σ)
19‐6‐2012
Marcel
Merk
–
SSP2012
32
CP
Viola/on
Measurements
@
LHCb
• Time
Integrated
measurements:
– (1)
Direct
CP
Viola/on
in
charmless
decays
B(s)‐>Kπ.
– (2)
CP
Viola/on
in
charmed
decays
B‐D0K‐
and
B‐D0π‐
• Time
dependent
measurements
(interference
of
mixing
and
decay):
– (3)
CP
viola/on
in
charmless
B(s)
decays
BsKK
and
Bππ
– (4)
CP
Viola/on
in
charmed
Bs
decays
BsDs
K
– (5)
CP
Viola/on
in
Bs
decays
to
CP
eigenstate
BsJ/ψ φ
• CP
Viola/on
in
mixing
– (6)
A
charming
surprise
19‐6‐2012
Marcel
Merk
–
SSP2012
33
(4)
Charmed
Bs
decays:
BsDsK
Two
decay
amplitudes
to
the
same
final
state:
1) via
mixing
BsBsDs‐K+:
γ
βs
:
+
:
2) direct:
BsDs‐K+:
• Golden
mode
for
a
/me
dependent
measurement
of
“γ
with
trees”
- Hadronic
uncertain/es
small
• Sensi/vity
to
new
physics
enters
via
the
mixing
loop:
expected
to
be
small
• Combined
analysis
of
BDsK
with
BsDsπ:
- For
BsDsπ
only
decay
amplitude
2)
is
possible
(no
CP
viola/on)
- Use
BsDsπ
decay
as
a
calibra/on
process
for
B
mixing
19‐6‐2012
Marcel
Merk
–
SSP2012
34
(4)
Charmed
Bs
decays:
BsDsK
1000
800
LHCb‐CONF‐2011‐050
0.4
BsDsπ
LHCb
0.37
†‐1
400
200
5200
5400
LHCb preliminary
s=7TeV, 340 pb -1
OST+SSKT
0.2
-
B0s → Dsπ+
B0→ Dsπ+
*B0s→ Ds π+
0
Bs → Dsρ+
B0→ D π+
Combinatorial
600
0
Amix
Events / ( 7 MeV/c2)
arXiv:1204.1237
0
-0.2
5600
5800
- +
m(D sπ ) [MeV/c2]
-0.4
0
0.1
0.2
0.3
t modulo (2" / !ms) [ ps ]
Events / ( 14 MeV/c2)
arXiv:1204.1237
180
160
140
120
100
80
60
40
20
0
19‐6‐2012
BsDsK
LHCb
0.37
†‐1
B0s → D-sK +
B0→ DsK +
-
B0→ D K +
B0s → D-sπ+
0
(*)-
B0s → Ds K
(*)Λ0b→ Ds p
(*)+
(*)-
B0s → Ds ( π+, ρ+)
Combinatorial
5200
5400
5600
5800
m(D sK +) [MeV/c2]
• BsDsπ
LHCb‐CONF‐2011‐050
and
arXiv:1112.4311
- Flavour
tagging:
Opposite
side:
εD2
=
3.2
±
0.8
%
Same
side:
addi/onal
power
- Measurement
of
Bs
mixing:
Δms
=
17.63
±
0.11
±
0.02
ps‐1
arXiv:1204.1237
• BsDsK
- Branching
ra/o:
BR
=
(1.90
±
0.12
±
0.18)
x
10‐4
Marcel
Merk
–
SSP2012
35
CP
Viola/on
Measurements
@
LHCb
• Time
Integrated
measurements:
– (1)
Direct
CP
Viola/on
in
charmless
decays
B(s)‐>Kπ.
– (2)
CP
Viola/on
in
charmed
decays
B‐D0K‐
and
B‐D0π‐
• Time
dependent
measurements
(interference
of
mixing
and
decay):
– (3)
CP
viola/on
in
charmless
B(s)
decays
BsKK
and
Bππ
– (4)
CP
Viola/on
in
charmed
Bs
decays
BsDs
K
– (5)
CP
Viola/on
in
Bs
decays
to
CP
eigenstate
BsJ/ψ φ
• CP
Viola/on
in
mixing
– (6)
A
charming
surprise
19‐6‐2012
Marcel
Merk
–
SSP2012
36
(5)
Bs
decays
to
a
CP
eigenstate:
BsJ/ψϕ
Two
decay
amplitudes
to
the
same
CP
eigenstate
final
state.
1) via
mixing
BsBsJ/ψϕ:
:
βs
+
:
2) direct:
BsJ/ψϕ:
• Golden
mode
for
a
/me
dependent
measurement
of
“βs
via
mixing
diagram”
- Hadronic
uncertain/es
small
• High
sensi/vity
to
new
physics
that
enters
via
the
mixing
loop
• Bs
is
a
speudoscalar
(s=0)
while
J/ψ
and
ϕ
are
vector
par/cles
(s=1)
• Final
state
is
superposi/on
of
CP
even
(L=0
and
L=2)
CP
odd
(L=1)
• Requires
angular
analysis
to
disentangle
• Alterna/ve
analysis
in
pure
CP
odd
eigenstate
BsJ/ψ
f0(980)
19‐6‐2012
Marcel
Merk
–
SSP2012
37
2500
1600
LHCb Preliminary
data
bkg. component
θ
ψ
1200
BsJ/ψϕ
1500
LHCb Preliminary
1400
1†‐1
sig. component
2000
Events / 0.1
Events / 2 MeV
(5)
Bs
decays
to
a
CP
eigenstate:
BsJ/ψϕ
1000
800
600
1000
ϕ
400
200
5300
5350
5400
5450
Bs mass [MeV]
Events / 0.1
0
0
-1
1400
-0.5
0
0.5
1
cos !
Events / 0.31 rad
500
LHCb Preliminary
1400
1200
Events / 0.2 ps
1000
CP‐even
800
sig. component
LHCb Preliminary
1200
1000
data
cp-even sig. component
cp-odd sig. component
3
10
s-wave component
600
CP‐odd
400
200
0
-1
102
-0.5
0
LHCb‐CONF‐2012‐002
10
2
4
6
8
Decay time t [ps]
19‐6‐2012
800
600
bkg. component
complete pdf
LHCb Preliminary
400
200
0.5
1
0
-2
cos !
Preliminary:
ϕs
=
‐0.001
±
0.101
±
0.027
rad
ΔΓs
=
0.116
±
0.018
±
0.006
ps‐1
0
2
! [rad]
ϕs=2βs
Consistent
with
no
CP
viola/on
as
predicted
in
SM
Marcel
Merk
–
SSP2012
38
CP
Viola/on
Measurements
@
LHCb
• Time
Integrated
measurements:
– (1)
Direct
CP
Viola/on
in
charmless
decays
B(s)‐>Kπ.
– (2)
CP
Viola/on
in
charmed
decays
B‐D0K‐
and
B‐D0π‐
• Time
dependent
measurements
(interference
of
mixing
and
decay):
– (3)
CP
viola/on
in
charmless
B(s)
decays
BsKK
and
Bππ
– (4)
CP
Viola/on
in
charmed
Bs
decays
BsDs
K
– (5)
CP
Viola/on
in
Bs
decays
to
CP
eigenstate
BsJ/ψ φ
• CP
Viola/on
in
mixing
– (6)
A
charming
surprise
19‐6‐2012
Marcel
Merk
–
SSP2012
39
(6)
CP
Viola/on
in
mixing:
A
Charming
Surprise
• CP
Viola/on
in
charm:
– The
mixing
amplitude
is
small.
• Expect
no
significant
interference
between
mixing
and
decay
• Difference
DD
and
D‐>D
expected
to
be
very
small

O(10‐4)
– Direct
CP
viola/on
(in
decay)
• Expected
negligible
in
Cabibbo
favoured
modes
(“Trees”)
• In
Cabibbo
suppressed
mode
“plausible”
up
to
O(10‐3
‐
10‐4)
– Expecta/on:
observa/on
of
any
CP
asymmetry
in
charm
is
a
sign
of
New
Physics…
19‐6‐2012
Marcel
Merk
–
SSP2012
40
(6)
CP
Viola/on
in
mixing:
A
Charming
Surprise
• CP
asymmetry
from
charm
decays:
AfCP (t) =
ΓD→f (t) − ΓD→f (t)
ΓD→f (t) + ΓD→f (t)
• Measure
/me
integrated
CP
asymmetries
in
Dπ+π‐
and
DK+K‐
– Use
decays
D*±D
πs±
to
tag
the
flavour
of
the
D
(D
or
D)
using
the
charge
of
the
slow
pion
πs
M.Gersabeck
et.
al.,
J.Phys.
G39
(2012)
045005
AfCP
=
adir
CP (f )
+
!t"
τ
aind
CP
• Observed
asymmetry
includes
detector
effects
and
possible
produc/on
asymmetry
of
D*
Araw (f) = ACP (f) + AD (f) + AD (πs ) + AP (D∗+ )
• Cancel
these
to
first
order
by
measuring
difference
between
Dπ+π‐
and
DK+K:
∆ACP ≡ Araw (KK) − Araw (ππ) = ACP (KK)−ACP (ππ)
! dir
" ∆ #t$ ind
dir
= aCP (KK)−aCP (ππ) +
aCP
τ
• Contribu/on
from
possible
indirect
CP
viola/on
term
small
19‐6‐2012
Marcel
Merk
–
SSP2012
41
Signal
Yields
40000
!"
LHCb
D0K+K‐
20000
LHCb,
0.6
P‐1,
PRL
108,
111602
(2012)
80000
!"
LHCb
D*+

D0(K+K‐)π
60000
40000
!ACP (%)
60000
Entries / (0.1 MeV/c2)
Entries / (0.5 MeV/c2)
1.4
M
tagged
D0K+K‐
and
0.4M
tagged
D0π+π‐
1840
1860
1880
-
+
10000
D0π+π‐
5000
5
10
15
!m
Entries / (0.1 MeV/c2)
Entries / (0.5 MeV/c2)
#"
LHCb
LHCb
D*+

20000
(MeV/c2)
-2
-4
#"
-6
0
D0(π+π‐)π
15000
1840
1860
1880
1900
m(!-!+) (MeV/ c2)
10
15
20
ΔACP
=(‐0.82±0.21(stat)±0.11(sys)
)%
3.5
σ
devia/on
from
zero.
10000
0
0
5
Run block
5000
0
1820
LHCb
0
0
0
1900
m(K K ) (MeV/c2)
4
2
20000
0
1820
6
5
10
15
!m (MeV/c2)
• Value
is
larger
than
was
expected
from
SM
before
measurement
was
available
• PostdicKon:
general
agreement
that
we
cannot
yet
exclude
that
it
is
caused
by
hadronic
uncertain/es…
- Currently
hot
ac/vity
in
experiment
and
in
theory.
19‐6‐2012
Marcel
Merk
–
SSP2012
42
Summary
&
Conclusions
• CP
Viola/on:
– 1964
CP
Viola/on
with
K0
– 2001
CP
Viola/on
with
B0
– 2011
Evidence
for
CP
Viola/on
with
Bs
and
CP
Viola/on
with
D0
• LHCb
carrying
out
full
physics
program
– Collected
1.5
†‐1
by
now
– Backgrounds
well
under
control
– Expect
to
collect
5
†‐1
before
upgrade
• Time
dependent
and
/me
integrated
CP
observables
for
B
decays
– Towards
measurements
of
CKM
angle
“γ
with
trees”
– Towards
measurements
of
CKM
angle
“γ
with
loops”
– World
best
measurement
of
Bs
mixing
phase
ϕs
(consistent
with
SM
βs)
• CP
viola/on
in
charm
– Evidence
for
CP
viola/on
in
ΔACP.
– Hadronic
effects
to
be
clarified.
• LHCb
upgrade
in
2018
– Higher
luminosity:
expect
to
collect
50
†‐1
in
the
upgrade
– New
40
MHz
Trigger
• Extend
the
physics
program
19‐6‐2012
Marcel
Merk
–
SSP2012
43