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Flavour Physics with LHCb“When Beauty Decays and Symmetries Break”
Seminar RuG
March 31, 2008
Marcel MerkNikhef and VU
31-3-2008
Contents:• CP violation with the CKM matrix• Bs meson and “new physics”• B-physics with the LHCb detector
LHCb
ATLAS
CMSALICE
CERN
3
LHC: Search for physics beyond Standard Model
31-3-2008
• Atlas/CMS: direct observation of new particles• LHCb: observation of new particles in quantum loops
LHCb is aiming at search for new physics
in CP violation and Rare Decays
Focus of this talk
Atlas CMS LHCb
4
Flavour physics with 3 generations of fermions
31-3-2008
u
d
c
s
t
b
I II III
e tm
ne nm nt
quar
ksle
pton
s
~0
1777106
~0 ~0
0.511
120 4300
1763001200
~7
~3
LEP 1
2 neutrino’s3 neutrino’s4 neutrino’s
measurements
Beam energy (GeV)
Cros
s se
ction
Note: In the Standard Model 3 generations of Dirac particles is the minimum requirement to create a matter - antimatter asymmetry.
5
Quark flavour interactions
31-3-2008
• Charged current interaction with quarks:
5
2
, ,
1 1
;
I Iu d
k
Id
w
I
u
eaA J
J
d
u c
W
t s
g
b
• Quark mass eigenstates are not identical to interaction eigenstates:
†. . . . . .
. . . .
. . . . . .
;, ,M Mu u d du d
d
u c t s
b
M M
• In terms of the mass eigenstates the weak interaction changes from:
51 12II
u dJ
u, c, t
d, s, b
Wgweak
J
6
Quark flavour interactions
31-3-2008
• Charged current interaction with quarks:
5
2
, ,
1 1
;
I Iu d
k
Id
w
I
u
eaA J
J
d
u c
W
t s
g
b
• Quark mass eigenstates are not identical to interaction eigenstates:
†. . . . . .
. . . .
. . . . . .
;, ,M Mu u d du d
d
u c t s
b
M M
• In terms of the mass eigenstates the weak interaction changes to:
51 12 CKM du VJ Cabibbo Kobayashi Maskawa quark mixing matrix
†CKM u dV M M
u, c, t
d, s, b
Wgweak
J
7
The CKM Matrix VCKM
31-3-2008
ud us ub
cd cs cb
td ts tb
V V V
V V V
V V V
8
The CKM Matrix VCKM
31-3-2008
ud us ub
cd cs cb
td ts tb
V V V
V V V
V V V
d
b
dc
Vcb
Typical B-meson decay diagram:
The B-meson has a relatively long lifetime of 1.5 ps
Related to mass hierarchy?
9
The CKM Matrix VCKM
31-3-2008
ud us ub
cd cs cb
td ts tb
V V V
V V V
V V V
From unitarity (VCKM V†CKM=1) :
CKM has four free parameters: 3 real: l (0.22) , A ( 1), r 1 imaginary: ih
2 3
2 2
3 2
11
21
12
1 1
A
A
A A
i
i
Particle → Antiparticle: Vij → Vij*
=> 1 CP Violating phase!
Wolfenstein parametrization: VCKM
10
The CKM Matrix VCKM
31-3-2008
ud us ub
cd cs cb
td ts tb
V V V
V V V
V V V
From unitarity (VCKM V†CKM=1) :
CKM has four free parameters: 3 real: l (0.22) , A ( 1), r 1 imaginary: ih
2 3
2 2
3 2
11
21
12
1 1
A
A
A A
i
i
Particle → Antiparticle: Vij → Vij*
=> 1 CP Violating phase!
Wolfenstein parametrization: VCKM
ie
ie
11
Unitarity Triangle: VCKM V†CKM = 1
31-3-2008
ud us ub
cd cs cb
td ts tb
V V V
V V V
V V V
0*** tbtdcbcdubud VVVVVV
0*** tbubtsustdud VVVVVV
12
Unitarity Triangle: VCKM V†CKM = 1
31-3-2008
ud us ub
cd cs cb
td ts tb
V V V
V V V
V V V
0*** tbtdcbcdubud VVVVVV
0*** tbubtsustdud VVVVVV
,21, 2
*
*
cbcd
ubud
VV
VV
*
*
cbcd
tbtd
VV
VV
01
Im
Re
Unitarity triangle:Individual CP violating phases in CKM are not observableThe combinations a,b,g are
Amount of CP violation is proportional to surface of the triangle
*
*
cbcd
tbub
VV
VV
*
*
cbcd
tdud
VV
VV
0
+
Re** / cbcdtsus VVVV
: Bd mixing phase: Bs mixing phase: weak decay phase
2
2
,
*
*
DB
KDB
DKDKB
d
ss
d
..... ,/0 JBs
,21, 2
*
*
cbcd
ubud
VV
VV
*
*
cbcd
tbtd
VV
VV
01
Im
ReIm
..... ,/ 00SKJB
,.....,,0 B
Precise determinationof parameters throughstudy of B-decays.
Precise determinationof parameters throughstudy of B-decays.
Unitarity Triangle and B-physics
14
Benchmark Example: Bs→Ds K
31-3-2008
iud us ub
cd cs cbi
td ts tb
V V V e
V V V
V e V V
15
Benchmark Example: Bs→Ds K
31-3-2008
iud us ub
cd cs cbi
td ts tb
V V V e
V V V
V e V V
• But how can we observe a CP asymmetry?
s s
s s
i
i
B D K Ae
B D K Ae
• Decay probabilities are equal? No CP asymmetry??
Make use of the fact that B mesons “mix”…..
• Decay amplitudes: particles:
2 2Prob Probi i
ss s sB D K Ae B D K Ae
antiparticles:
16Sept 28-29, 2005
B meson Mixing Diagrams
22 *
22 *
* *
:
:
, :
t tb td
c cb cd
c t tb td cb cd
t t m V V
c c m V V
c t c t m mV V V V
2 6
2 6
6
t
c
c t
m
m
m m
Dominated by top quark mass:
2
12
0.00002 psGeV
tB
mm
c
22 2 2 2 2
02( / ) | |
6 d d d
Fd w B t W B td B B
Gm m S m m m V B f
d b
b d
W
u,c,t
u,c,tWBd Bd
A neutral B-meson can oscillate into an anti B-meson before decaying:
17Sept 28-29, 2005
B0B0 Mixing: ARGUS, 1987
0 * * 01 1 1 1 1 1
0
1 1
0 * * 02 2 2 2 2
02 2 2 ,
B D D D
D K
B D D D
D K
,
,
First sign of a really large mtop!
Produce a bb bound state, (4S),in e+e- collisions:
e+e- (4S) B0B0
and then observe:
~17% of B0 and B0 mesons oscillate before they decay Dm ~ 0.5/ps, tB ~ 1.5 ps
Integrated luminosity 1983-87: 103 pb-1
18
Bd vs Bs mixing
31-3-2008
d b
b d
W
t
t
WBd Bd
The top quark and its interactions can be studied without producing it directly!
s s
b d
W
t
t
WBs Bs
Bd → Bd
Bd → Bd
Bd mixingBs mixing
Bs → Bs
Bs → Bs
Bs mixing
19
The CP violating decay: Bs→Ds K
31-3-2008
Due to mixing possibility the decay Bs→Ds K can occur in two quantum amplitudes:
a1. Directly:
a2. Via mixing:
Coupling constant with CP odd phase g
How do the phase differences between the amplitudes lead to an observable CP violation effect…?
In addition, mixing and gluon interactions add a non-CP violating phase “d” between a1 and a2
20Sept 28-29, 2005
Observing CP violation
|A||A| Only if both g and d are not 0
BDs+ K−BDs
− K+
A=a1+a2A=a1+a2
d d+g
-g
a1 a1
a2
a2
AA
Compare the |amplitude| of the B decay versus that of anti-B decay;g is the CP odd phase , d is a CP even phase
Note for completeness: since the CP even phase depends on the mixingthe CP violation effect becomes decay time dependent
21
Double slit experiment with quantum waves
31-3-2008
Bs
Ds-
K+
LHCb is a completely analogous interference experiment using B-mesons…
Nikhef-evaluation 226-sept-2007
sB D K “slit A”:
A Quantum Interference B-experiment
pp at LHCb:100 kHz bb
Decay timeBs
Ds-
K+
“slit B”: sB B D K
Measure decay time
Nikhef-evaluation 236-sept-2007
CP Violation: matter – antimatter asymmetry
s s sB B D K
s sB D K
Bs
Ds-
K+
s sB D K
An interference pattern:
Decay time
Decay time
s sB D K
Nikhef-evaluation 246-sept-2007
s s sB B D K
s sB D K
Bs
Ds+
K-
s s sB B D K
s sB D K
Bs
Ds-
K+
Matter
Antimatter
CP-mirror:
Difference between curves is proportional
to the phase g
Decay time
Decay time
s s
s sB
B D
D
K
K
Decay time
An interference pattern:
CP Violation: matter – antimatter asymmetryCP Violation: matter – antimatter asymmetrys sB D K
Observation of CP Violation is a consequence of quantum interference!!
Nikhef-evaluation 256-sept-2007
Searching for new virtual particles
Standard Model
Bs
J/y
f
Standard Model
Decay time
/sB J
Nikhef-evaluation 266-sept-2007
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Searching for new virtual particles
Standard Model
New Physics
Bs
J/y
f
Decay time
/sB J Tiny weak phase in couplings!
Possible weak phase in couplings!
?
Nikhef-evaluation 276-sept-2007
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Searching for new virtual particles
Standard Model
New Physics
Mission:To search for new particles and interactions that affect theobserved matter-antimatter asymmetry in Nature, by makingprecision measurements of B-meson decays.
B->J/yfB->J/yf
Bs
J/y
f
/
/
s
sB
J
J
B
Search for a CP asymmetry:
Decay time
/sB J
?
2831-3-2008
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
+
First sign of New Physics in Bs mixing?N sSM Pi i iAe Be Ce
SM box has (to a good approx.) no weak phase: fSM = 0
S.M. N.P. ?
2931-3-2008
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
Bs
g!
b
b
s
s t
t
Bs
W W
Bs
Bs
b
s
s
b
x
x
b!
b!
s!
s!g!
Bs→ Bs→ DsπBs→ Bs→ J/ψφ
b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0b W s
t
K*
K*
b s
μ
μ
μ
μ
xs!b!
g!
B0→K*μ μ
d
dB0
B0 tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
tW
Bs
Bsb
b
s
s
μ
μ
μ
μ
x
s!
b!
g!
Bs→μ μ
SM:
NewPhysics:
ΔB=2 ΔB=1 ΔB=1
+
First sign of New Physics in Bs mixing?N sSM Pi i iAe Be Ce
SM box has (to a good approx.) no weak phase: fSM = 0
If fS ≠ 0 then new physics outside the CKM is present…
S.M. N.P.
UTfit collab.; March 5, 2008Combining recent results of
CDF, D0 on
with Babar, Belle results:
March 5,2008
/sB J
?
3.7 s deviationFrom 0
The LHCb experiment
LHCb
ATLAS
CMSALICE
qb
qb
LHCb experiment:700 physicists50 institutes 15 countries
31
LHCb experiment in the cavern
31-3-2008
Shielding wall(against radiation)
Electronics + CPU farm
Offset interaction point (to make best use of existing cavern)
Detectors can be moved away from beam-line for access
32
b-b detection in LHCb
31-3-2008
LHCb event rate: 40 MHz1 in 160 is a b-bbar event 1012 b-bbar events per year
Background SupressionFlavour taggingDecay time measurement
• vertices and momenta reconstruction • effective particle identification (π, К, μ, е, γ)• triggers
33
GEANT MC simulation
Used to optimise the experiment and to test measurement sensitivities
34
A walk through the LHCb detector
p p
~ 200 mrad~ 300 mrad (horizontal)
10 mrad
Inner acceptance ~15 mrad (10 mrad conical beryllium beampipe)
35
LHCb Tracking: vertex region
31-3-2008
Vertex locator around the interaction regionSilicon strip detector with ~ 30 mm impact-parameter resolution
36
Pile-Up Stations
Interaction Regions=5.3 cm
LHCb tracking: vertex region
y
x
y
x
37
LHCb tracking: momentum measurement
0.15 Tm
By[T]Bfield: B dl = 4 Tm
Tracking: Mass resolution for background suppression in eg. DsK
38
LHCb tracking: momentum measurement
All tracking stations have four layers:0,-5,+5,0 degree stereo angles.
Silicon: ~1.41.2 m2
Straw tubes~65 m2
39
~1.41.2 m2
Red = Measurements (hits)Blue = Reconstructed tracks
Eff = 94% (p > 10 GeV)
• Typical Momentum resolution dp/p ~ 0.4%• Typical Impact Parameter resolution sIP ~ 40 mm
LHCb tracking: momentum measurement
40
LHCb Hadron Identification: RICH
3 radiators to coverfull momentum range: Aerogel C4F10
CF4
RICH2: 100 m3 CF4 n=1.0005
RICH: K/p separation e.g. to distinguish Dsp and DsK events.
RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014
Cerenkov light emission angle
41
LHCb calorimeters
e
h
Calorimeter system : • Identify electrons, hadrons, neutrals• Level 0 trigger: high electron and hadron Et (e.g. Ds K events)
42
LHCb muon detection
m
Muon system:• Identify muons • Level0 trigger: High Pt muons
43
View of LHCb in Cavern
31-3-2008
VELO
Muon det Calo’s RICH-2 MagnetOT RICH-1
VELO
Muon det Calo’s RICH-2 MagnetOT RICH-1
It’s full!Installation of major structures is essentially complete
44
Hope to soon see the first events from…
31-3-2008
4531-3-2008
Display of LHCb simulated event
46
Prepare Bs→DsK Reconstruction…
• Trigger : – ET Calorimeters, Vertex topology
• Flavour Tag: – Lepton-ID, Kaon-ID
• Background suppression: – Mass resolution, K/ p ID
• Decay time: – Decay distance measurement– Momentum measurement
Ds
BsK
K
,K
d
p47 mm 144 mm
440 mmInvariant Mass
47
… to see time dependent CP violation signal!
31-3-2008
5 years data:Bs→ Ds
-p+
Bs→ Ds-K+
The amplitude of these “wiggles“ are proportional to the imaginary part of the CKM phase gamma!
iud us ub
cd cs cbi
td ts tb
V V V e
V V V
V e V V
Decay time (ps) →
48
Conclusion: after 5 years of LHCb…
31-3-2008
To make this plot only Standard Model physics is assumed.
CKM Unitarity Triangle in 2007:Expected errors after 5 years (10 fb-1) of LHCb:
49
Conclusion and Outlook LHCb
31-3-2008
• CP Violation• Measure the Bs mixing phase (Bs→J/y f )• Measure the CKM angle gamma via tree method (Bs → DsK)• Measure the CKM angle gamma via penguin loops (B(s) → h+h - )
• Rare Decays• Measure Branching Ratio Bs → m+ m -
• Measure angular distribution B0 → K* m+ m - • Measure radiative penguins decays: b → s g (B → Xs g )
• Other Flavour Physics• Angle beta, B-oscillations, lifetimes, D-physics, Higgs,…?
The collaboration has organised analysis groups and identified “hot topics”:
• Atlas and CMS look for new physics via direct production of particles• LHCb tries to study it via the (possibly complex) couplings in B decay loop diagrams
50
Summary of Signal Efficiencies
31-3-2008
51
Thank you for the attention.
31-3-2008
5231-3-2008
5331-3-2008
5431-3-2008
55
Research Questions
• Is flavour physics fully described by the CKM mechanism• Is CP violation in CKM sufficient to describe baryogenesis • Many models beyond the SM include a rich flavour physics
structure• Are the penguin, box and tree diagrams governed by the same
physics?• Search for CP violation where SM predicts none• Measure Branching Ratio for processes which are forbidden in SM
• For the hypothesis that neutrinos are not massless the lepton system has a similar flavour strcture VCKM → VPMNS
31-3-2008
56
Bd meson vs Bs meson
31-3-2008
1m
x
1
mx
These B bbar oscillations allow for a beautiful CP experiment
57
Result of track findingTypical event display:
Red = measurements (hits)Blue = all reconstructed tracks
Efficiency vs p : Ghost rate vs pT :
Eff = 94% (p > 10 GeV)
Ghost rate = 3%(for pT > 0.5 GeV)
VELO
TT
T1 T2T3On average:
26 long tracks11 upstream tracks4 downstream tracks5 T tracks26 VELO tracks
2050 hits assigned to a long track: 98.7% correctly assigned
Ghosts:Negligible effect onb decay reconstruction
58
Experimental Resolution
dp/p = 0.35% – 0.55%
p spectrum B tracks
sIP= 14m + 35 m/pT
1/pT spectrum B tracks
Momentum resolution Impact parameter resolution
59
Particle IDRICH 1 RICH 2
e (K->K) = 88%
e (p->K) = 3%
Example:Bs->Dsh
K
Bs
K
,K
DsPrim vtx
60
Event in the Simulation
31-3-2008
61
Zoom in on the Velo detector
31-3-2008
Physics challenges of the LHC (III) 62Roger Forty
4. Expected results
• Example of an early physics measurement that is expected from LHCb:Measurement of Bs–Bs oscillationsUse channel Bs Ds
-p+
• Plot made for one year of data 80,000 selected eventsfor Dms = 20 ps-1 (SM preferred)Proper time distribution for eventsproduced as Bs (rather than Bs)
• Need to take care of flavourtagging, proper-time resolution,background rejection andacceptance correction
• Can measure frequency accurately cf recent result Dms = 17.8 ± 0.1 ps-1 [CDF] Next step: measure the phase of the oscillation, using Bs J/y f decays (Bs counterpart of B0 J/y KS), cleanly predicted in the SM: fs = -0.04
Physics challenges of the LHC (III) 63Roger Forty
Penguin decays
• These are another category of decays involving loop diagramsNew particles might appear in those loops
• Some indication from the B factory experiments that their results for penguindecays do not agree with expectations might be a hint of new physics?
• LHCb should reach a precision of ± 0.04on the asymmetry of Bs ff
ExperimentTheory
Physics challenges of the LHC (III) 64Roger Forty
Rare decays• Profit from the enormous statistics
to search for very rare decays such as Bs m+m-
Branching ratio ~ 3 10-9 in the Standard Model
• BR can be strongly enhanced in SUSY[G. Kane et al, hep-ph/0310042]
• LHCb can reach the SM predictionin a few years
Integrated Luminosity (fb-1)
BR
(x1
0-9) 5
3
SM prediction
SUSY models LHCb
b q1
d, s
q2W−
qB
Topologies in B decays
g
d (s)
q
q
W −
b u,c,t
b
q
u,c,t
u, c, t
q
bqBqB W+ W−
V*ib Viq
Viq V*ib
Trees
Penguins
Boxes
mbγ
L+mqγ
R
b q
W–
u, c, t
Z, γ
d (s)
l+
l−
W −
b u, c, t
Search for NP comparing observables measured in tree and loop topologies
(tree+box) in B J/ Ks
(tree) in many channels(tree+box) in Bs J/
(peng+tree) in B,, (peng+box) in B Ks
(peng+box) in Bs
New heavy particles, which may contribute to d- and s- penguins,could lead to some phase shifts in all three angles:
(NP) = (peng+tree) - (tree)
(NP) = (BKs) - (BJ/Ks) ≠ 0 (NP) = (Bs) - (BsJ/)
B → K* μμ
?A very important property isforward-backward asymmetry..
..and position of its zero, which is robust in SM:
)(
2
09
70 sC
Cs
eff
eff
AFB(s), fast MC, 2 fb–1
s = (m)2 [GeV2]
