lhcb physics programme
DESCRIPTION
CERN Theory Institute: Flavour as a window to New Physics at the LHC: May 5 –June 13, 2008. LHCb Physics Programme. Marcel Merk For the LHCb Collaboration May 26, 2008. Contents: The LHCb Experiment Physics Programme: CP Violation Rare Decays. LHCb @ LHC. b. b. b. b. - PowerPoint PPT PresentationTRANSCRIPT
LHCb Physics Programme
Marcel MerkFor the LHCb Collaboration
May 26, 2008
Contents:• The LHCb Experiment• Physics Programme:
• CP Violation• Rare Decays
CERN Theory Institute: Flavour as a window to New Physics at the LHC: May 5 –June 13, 2008
LHCb @ LHC
A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays
CMSCMS ALICEALICE
ATLASATLASLHCbLHCb CERNCERN
√s = 14 TeVLHCb: L=2-5 x 1032 cm-2 s-1
bb = 500 binel / bb = 160=> 1 “year” = 2 fb-1
b
bb
b
The LHCb Detector
31-3-2008 3
VELO
Muon det Calo’s RICH-2 MagnetOT RICH-1
VELO
Muon det Calo’s RICH-2 MagnetOT+IT RICH-1
Installation of major structures is complete
4
A walk through the LHCb spectrometer…
B-Vertex Measurement
31-3-2008 5
Vertex Locator (Velo)Silicon strip detector with ~ 5 m hit resolution 30 m IP resolution
Vertexing:• Impact parameter trigger• Decay distance (time) measurement
Ds
BsK
K
K
d
47 m 144 m
440 mPrimary vertex
Decay time resolution = 40 fs
) ~40 fs
Example: Bs → Ds K
6
Momentum and Mass measurement
Momentum meas.: Mass resolution for background suppression
7
Momentum and Mass measurement
Momentum meas.: Mass resolution for background suppression
bt
Bs K
K
K
Ds
Primary vertex
Bs→ Ds KBs →Ds
Mass resolution ~14 MeV
8
Particle Identification
RICH2: 100 m3 CF4 n=1.0005
RICH: K/ identification using Cherenkov light emission angle
RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014
9
Particle Identification
RICH2: 100 m3 CF4 n=1.0005
RICH: K/ identification; eg. distinguish Ds and DsK events.
RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014
Cerenkov light emission angle
bt
Bs K
K
,K
Ds
Primary vertex
KK : 97.29 ± 0.06%K : 5.15 ± 0.02%
Bs → Ds K
10
LHCb calorimeters
e
h
Calorimeter system : • Identify electrons, hadrons, neutrals• Level 0 trigger: high ET electron and hadron
bt
Bs K
K
K
Ds
Primary vertex
11
LHCb muon detection
Muon system: • Level 0 trigger: High Pt muons• Flavour tagging: D2 = (1-2w)2 6% btag
Bs K
K
K
Ds
Primary vertex
12
LHCb trigger
HLT rate
Event type Physics
200 Hz Exclusive B candidates
B (core program)
600 Hz High mass di-muons
J/, bJ/X (unbiased)
300 Hz D* candidates Charm (mixing & CPV)
900 Hz Inclusive b (e.g. b)
B (data mining)
HLT: high IP, high pT tracks [software] then full reconstruction of event
40 MHz
1 MHz
2 kHz
L0: high pT (, e, , h) [hardware, 4 s]
Storage (event size ~ 50 kB)
DetectorL0, HLT and L0×HLT efficiency
Note: decay time dependent efficiency: eg. Bs → Ds K
Proper time [ps]
Effici
ency
bt
BsKK
K
Ds
Primary vertex
12
13
Measuring time dependent decays
bt
Bs K
K
Ds
Primary vertex
Measurement of Bs oscillations:
Bs->Ds– (2 fb-1)Experimental Situation:
• Ideal measurement (no dilutions)
14
Measuring time dependent decays
bt
Bs K
K
Ds
Primary vertex
Bs->Ds– (2 fb-1)
Measurement of Bs oscillations:
Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilution
15
Measuring time dependent decays
bt
Bs K
K
Ds
Primary vertex
Bs->Ds– (2 fb-1)
Measurement of Bs oscillations:
Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilution+ Realistic decay time resolution
16
Measuring time dependent decays
bt
Bs K
K
Ds
Primary vertex
Bs->Ds– (2 fb-1)
Measurement of Bs oscillations:
Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging+ Realistic decay time resolution+ Background events
17
Measuring time dependent decays
bt
Bs K
K
Ds
Primary vertex
Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilution+ Realistic decay time resolution+ Background events+ Trigger and selection acceptance
Two equally important aims for the experiment:• Limit the dilutions: good resolution, tagging etc.• Precise knowledge of dilutions
Bs->Ds– (2 fb-1)
Measurement of Bs oscillations:
18
Expected Performance: GEANT MC simulation
Used to optimise the experiment and to test physics sensitivities
Simulation software:• Pythia+EvtGen• GEANT simulation• Detector response
Reconstruction software:• Event Reconstruction• Decay Selection• Trigger/Tagging• Physics Fitting
Physics Programme
LHCb is a heavy flavour precision experiment searching for new physics
in CP-Violation and Rare Decays
• CP Violation• Rare Decays
19
CP Violation – LHCb Program
*cd cbV V
*ud ubV V
*td tbV V
*
cs cbV V*
us ubV V*
ts tbV V s
* *
*
*
*
*
*
*
arg ; arg
arg ; arg
tb cd cb
ud tb
ud tb
td
ub td
ub ts
cd cb s cbs
c
V V VV
V VV V
V V
V
V
V V V
V
s mixing phase (SM): 2 ssB d mixing phase (SM): 2 dB
Bd triangle
Bs triangle
2 3
2 2
3 2
1 / 2
1 / 2
1
CKM
i
i d si
eA
eA A e
V A
CP Program: Is CKM fully consistent for trees, boxes and penguins?1. measurements from trees2.measurement from penguins3. s from the box: “Bs mixing phase”4. s in penguins
b q1
d, sq2W−
g
d (s)
q
q
W −
b u,c,t
b
q
u, c, tu, c, t
q
bqBqB W+ W−
V*ib Viq
Viq V*ib 20
1.a +sfrom trees: Bs→DsK
2
2
1 cos 2 sin sin
1 cosh 2 sins2 2
c ho
/ s
s
s
ss
mt mt
t tB BD K
A
• Time dependent CP violation in interference of bc and bu decays:
Bs
Bs
sD K sie
sie ie
Bs
Bs
sD K sie
sie ie
Time
21
Bs/Bs →Ds–K+ (10 fb-1)
10 fb-1 data:Bs→ Ds
-
Bs→ Ds-K+
ms = 20)
• Since same topology BsDsK, Bs Ds combine samples to fit ms, s and Wtag together with CP phase s.
Channel Yield (2 fb-1)
B/S (90% C.L.)
BsDsK 6.2 k [0.08-0.4]
BsDs 140 k [0.08-0.3]
• Use lifetime difference s to resolve some ambiguities (2 remain).
Bs→DsK
s) = 9o–12o
Decay Time →22
B →Dand Bs→DsK
Channel Yield (2 fb-1) B/S
BsD*(K ) 206 k <0.3
B->D 210 k 0.3
B D(*) measures in similar way as BsDsK• More statistics, but smaller asymmetry• No lifetime difference: 8 –fold ambiguity for solutions
Invoking U-spin symmetry (d↔s) can resolve these ambiguities in a combined analysis of DsK and D(*)pi (Fleisher)
Can make an unambiguousextraction, depending onThe value of strong phases: < 10o (in 2 fb-1)
U-s
pin
brea
king
23
LHCb-2005-036
1.b from trees: B→DK
GLW method:fD is a CP eigenstate common to D0 and D0: fD= K+K-, +-,…Measure: B→D0K, B → D0K, B→ D1K• Large event rate; small interference • Measurement rB difficult
0
0
( )
( )Bi i
BA B D K
A B D Kr e e
B–
D0K–
D0K–
fDK–
bc favoured
bu suppressed
Decay time independent analysis
Cabibbo supp.
Cabibbo allowed.
• Interfere decays bc with bu to final states common to D0 and D0
colorsuppression
BiBr e
DiDr e
ADS method:Use common flavour state fD=(K+ –
Note: decay D0→K+– is double Cabibbo suppressed• Lower event rate; large interference
24
B→D(*)K(*)
GLW: D KK (2 rates) ;
ADS: D K ( 4 rates) ;
Channel Yield (2 fb-1) B/S
B → D(hh) K 7.8 k 1.8
B → D(K) K , Favoured 56 k 0.6
B → D(K) K , Suppressed 0.71k 2
B → D(K3) K, Favoured 62k 0.7
B → D(K3) K, Suppressed 0.8k 2() = 5o to 13o
depending on strong phases.
Also under study:B± → DK± with D → Ks 12
B± → DK± with D → KK 1
B0 → DK*0 with D → KK, K12
B± → D*K± with D → KK, K(high background)
Normalization is arbitrary:7 observables for 5 unknows:, rB, B, D
, D3
Overall: expect precision of() = 5o with 2 fb-1 of data
2
22
22 3 33
1 2 cos
2 cos
3 2 cos
B B B
B B B D
D
D DD
B D B BD DD
B K K K
B K K r r
B K K r
r
r r r
r r
r
ADS: D (4 rates) ;
Dalitz analyses
()
See talk of Angelo Carbone
25
2. from loops: B(s)→hh• Interfere b u tree diagram with penguins:
cos sin
cosh sinh2 2
CPf
dir mixf
f
fmt mtA
A At
t tA
1 2
3 4
, ,sin ; , ,sin
', ',sin ; ', ',sin
mix dir
KK KKdir mix
d
s
A Af d f d
f d f dA A
• Strong parameters d (d’), (’) are strength and phase of penguins to tree. Weak U-spin assumption : d=d’+-20% , , ’ independent• Assume mixing phases known
Channel Yield (2 fb-1)
B/S
B 36k 0.5
BsKK 36k 0.15
BsK+K-
BG
(1
See talk of Angelo Carbone
2 fb-1
ms=20
Time26
ACP(t) N B 0 J /KS N B0 J /KS N B 0 J /KS N B0 J /KS
(sin2 ) ~ 0.02
3. The Bd and Bs Mixing Phase
0 : ( ) sin sinCP f ddB A t m t sin sin: ( )
cosh cos sinh2
f ss CP
s sf
s
s
m tB A t
t t
s
Time dependent CP violation in interference between mixing and decay
“Yesterday’s sensation is today’s calibration and tomorrow’s background” – Val Telegdi
B
B
fCPdie
“Golden mode”
Bs
Bs
fCPsie
Channel Yield (2 fb-1)
B/S
BdJ/Ks 216 k 0.8
27
Bs mixing phase
Decay Yield (2 fb-1)
s)
J 8.5 k 0.109
J/ 3 k 0.142
J/’ 2.2 k 0.154
J/’ 4.2 k 0.08
c 3 k 0.108
Ds+ Ds
- 4k 0.133
All CP eig - 0.046
J/ 130 k 0.023
All - 0.021
sin sin( )
cosh cos sinh2
sCP
s
f
sf
s
s
m tA t
t t
s
1. Pure CP eigenstates Low yield, high background2. Admixture of CP eigenstates: Bs→J/ “Golden mode”: Large yield, nice signature However PS->VV requires angular analysis to disentagle =+1 (CP-even) ,-1 (CP-odd)
28
Full 3D Angular analysiscos cos
cos
Study possible systematics of LHCb acceptance and reconstruction on distributions.29
Bs→ J/
time
mass
signalbackg
sum
cos tr
cos
tr
(M)= 14 MeV
)= 35 fs
• Simultaneous likelihood analysis in time, mass, full 3d-angular distribution
• Include mass sidebands to model the time spectrum and angular distribution of the background
• Model the resolution
s)=0.02
See talk of Olivier Leroy
30
4. s from Penguins• Compare observed phases in tree decays with those in penguins
Channel Yield (2 fb-1) B/S Weak phase precision
B Ks 920 0.3 < B/S < 1.1 (sin(deff) 0.23
Bs 3.1 k < 0.8 (seff ) = 0.11
• Bs requires time dependent CP asymmetry (PSVV angular analysis a la J/ )
: 2 2effs
mix decays s sB 0 2: 2eff mix dec
say
d sB K
31
See talk of Olivier Leroy
Physics Programme
LHCb is a heavy flavour precision Experiment searching for new physics
in CP-Violation and Rare Decays
• CP Violation• Rare Decays
32
Rare Decays – LHCb Program
2F
eff CK ii
iM CG
H V O i=1,2: treesi=3-6,8: g penguini=7: penguini=9,10: EW penguin
Study processes that are suppressed at tree level to look for NP affecting observables: Branching Ratio’s, decay time asymmetries, angular asymmetries, polarizations, …
Weak B-decays described by effective Hamiltonian:
New physics shows up via new operators Oi or modification of Wilson coefficients Ci compared to SM.
LHCb Program: Look for deviations of the SM picture in the decays:1.b sl+l- ; Afb(BK*) , B+→K+ll (RK), Bs→ 2.b s ; Acp(t) Bs B→K*,b→γ, b→ *γ,B →0, B→γ3.Bq l+l- ; BR (Bs ) 4.LFV Bq l l‘ (not reported here) 33
1. B0→K*0µ+µ-
• Contributions from electroweak penguins• Angular distribution is sensitive to NP
2 F BFB
F B
N NA s m
N N
m2
[GeV2]
AFB(m2μμ) theory illustration
0.38 20 0.35SM: s 4.39 GeV
Observable: Forward-Backward Asymmetry in l
Zero crossing point (so) well predicted:
3 angles:l, ,K
A FB
34hep-ph:0106067v2
B0→K*0µ+µ-
Channel Yield (2 fb-1) BG (2 fb-1)
Bs→K*+ – 7200+-2200 (BR) 1770+-310
Event Selection:
Systematic study: • Selection should not distort m2
• s0 point to first order not affected
•AFB(s), fast MC, 2 fb–1
s = (m)2 [GeV2]
2 fb-1
A fb(s
)
Removeresonances
s0
See talk Mitesh Patel
(s0) = 0.5 GeV2
35
2. Bs→• Probes the exclusive b →s radiative penguin Measure time dependent CP asymmetry:
cos sin
cosh sinh2 2
ds s
Cir m
Px
s
i
s
B B mt mtA t
B
A
B At
At
Channel Yield (2 fb-1)
B/S
Bs→ 11k <0.55
Statistical precision after 2 fb-1 (1 year)(Adir ) = 0.11 ,(Amix ) = 0.11(requires tagging) (A) = 0.22 (no tagging required)
In SM b→s is predominatly (O(ms/mb)) left handedObserved CP violation depends on the polarization
See talk Mitesh Patel
Event selection:
b (L) + (ms/mb) (R)
Adir 0, Amix sin2 sin2 , A cos 2 cos tan = |b→s R| / | b→s L| , cos 1
SM:
Measures fraction “wrong” polarization36
3. Bs → • Bs is helicity suppressed SM Branching Ratio: (3.35 ± 0.32) x 10 -9
• Sensitive to NP with S or P coupling
Channel SM Yield (2 fb-1)
Background
Bs 30 83
Event Selection:Main Backgrounds: Suppressed by:b, b Mass & Vertex resol.B hh Particle Identification
With 2 fb-1 (1 “year”):• Observe BR: 6 x 10-9 with 5 • Assuming SM BR: 3observation
37
See talk Mitesh Patel
hep-ph/0604057v5
Physics Programme
LHCb is a heavy flavour precision Experiment searching for new physics
in CP-Violation and Rare Decays
• CP Violation• Rare Decays+ “Other” Physics
38
“Other” Physics
See the following talks for an overview:
Raluca Muresan:• Charm Physics: Mixing and CP Violation
Michael Schmelling:• Non CP Violation Physics:
– B production, multiparticle production, deep inelastic scattering, …
39
ConclusionsLHCb is a heavy flavour precision experiment searching
for New Physics in CP Violation and Rare Decays
A program to do this has been developed and the methods, including calibrations and systematic studies, are being worked out..
CP Violation: 2 fb-1 (1 year)*• from trees: 5o - 10o
• from penguins: 10o
• Bs mixing phase: 0.023• s
eff from penguins: 0.11
Rare Decays: 2 fb-1 (1 year)* • BsK* s0 : 0.5 GeV2
• Bs Adir , Amix : 0.11 A : 0.22• Bs BR.: 6 x 10-9 at 5
We appreciate the collaboration with the theory community to continue developing new strategies.
We are excitingly looking forward to the data from the LHC.
* Expect uncertainty to scale statistically to 10 fb-1. Beyond: see Jim Libby’s talk on Upgrade 40
Backup
LHCb Detector
MUON
RICH-2 PID
RICH-1 PID
Tracking (momentum)
vertexing
HCAL
ECAL
31-3-2008 43
Display of LHCb simulated event
Flavour Tagging
Performance of flavour tagging: Efficiency Wrong tag w Tagging power
Bd ~50%
Bs ~50% 33% ~6%
Tagging power:
22 1 2D w
Full table of selections
Nominal year = 1012 bb pairs produced (107 s at L=21032 cm2s1 with bb=500 b)Yields include factor 2 from CP-conjugated decaysBranching ratios from PDG or SM predictions
BsDsK 5 years data
BsDs-K+ BsDs+K-
BsbDs-K+ BsbDs+K-
Angle in Summary