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27/4/2006 UK SuperB Factory Workshop 1
The LHCb Perspective
Jim Libby – University of Oxford
27/4/2006 UK SuperB Factory Workshop 2
Outline� Physics goals of SuperB and LHCb (almost)
identical
� Indirect search for New Physics in heavy flavour decay
� In particular CP violating and rare B decays
� Is there a synergy with a Super B factory?
� Synergy to symbiosis
� LHCb detector and status
� LHCb core programme
� Comparison to SuperB
� An upgraded LHCb
� Conclusions
27/4/2006 UK SuperB Factory Workshop 3
Symbiosis-living together
� In symbiosis, at least one member of the pair
benefits from the relationship
� The other member may be:
� injured
� relatively unaffected
� may also benefit ( = mutualism)
27/4/2006 UK SuperB Factory Workshop 4
27/4/2006 UK SuperB Factory Workshop 5
Requirements for flavour physics at the LHC
� Triggering:
� 6 in 1000 inelastic pp collisions at 14 TeV contain a bb pair
� Average of 1 interaction/bunch crossing (40 MHz)
� Reduce event rate for mass storage at 2 kHz
� Also require standard B physics tools
� Vertexing
� Particle identification
� Good invariant mass resolution
� Neutral reconstruction
� Flavour tagging
� A large number of bb events!
27/4/2006 UK SuperB Factory Workshop 6
1
10
102
-2 0 2 4 6
eta of B-hadron
pT
of
B-h
adro
n
ATLAS/CMS
LHCb100 µb
230 µb
Pythia production cross section
Acceptance and luminosity� In the forward region at LHC the bb
production cross section is large
� All types of B hadron
� LHCb uses the forward direction
� 4.9 > η >1.9
� Both hadrons containing the b & b quarks are likely to be within the acceptance
� B hadrons are moving with considerable momentum ~100 GeV/c
� Design luminosity L=2×1032 cm-2s-1
� Maximises number of single interactions
� 1012 B hadrons in 107 sec = 1 LHC year
η
pt
27/4/2006 UK SuperB Factory Workshop 7
LHCb detectorMuon Detector
Tracking
stations
Trigger
Tracking
proton
beam
interaction
region
27/4/2006 UK SuperB Factory Workshop 8
LHCb cavern snapshotMuon shielding and
electronics tower
HCAL and
ECAL modules RICH 2
Magnet –
mapped
RICH 1 -
photo-detector
magnetic shielding
WILL BE READY FOR
2007 PILOT RUN
27/4/2006 UK SuperB Factory Workshop 9
LHCb trigger� First level hardware trigger
� High pt hadrons, leptons and photons
� Veto multiple interactions
� If event passes 1st level all sub-detector data readout at 1 MHz to Higher Level Trigger farm
� Adaptable software trigger
� Fast VELO tracking to identify high impact parameter tracks
� Match to high pt objects that fired first level
� 2 kHz output rate
� Inclusive D* (300 Hz) – PID calibration and charm physics
� Dimuon (600 Hz) – B→J/ψX with no impact parameter selection
� Inclusive b→µ (900 Hz) – data mining and calibrations
� Exclusive B decay (200 Hz) – physics channels
27/4/2006 UK SuperB Factory Workshop 10
Tracking and vertexing
� Proper time resolution στ ~ 40 fs�Bs →Dsh (h=π,K)�Bs → J/ψ φ
� Essential for time dependent Bs measurements
Bs→Dsπ
σ(mB) [MeV/c2]Channel
8Bs → J/ψ φ(mJ/ψ constrained)
16Bs → J/ψ φ
14Bs →Ds π
Bs → µµ 18
Bs→DsπAll performance results with PYTHIA+GEANT4
simulation unless otherwise stated
27/4/2006 UK SuperB Factory Workshop 11
2GeV/c
5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5
Co
un
ts
0
50
100
150
200
250
300
Invariant mass
-π +π → dB-π + K→
dB
- K+ K→ sB
- K+π → sB
- p K→ bΛ
-π p → bΛ
2MeV/c
5100 5150 5200 5250 5300 5350 5400 5450 5500
Co
un
ts
0
200
400
600
800
1000
1200
Invariant mass
-π +π → d
B-π +
K→ dB-
K+
K→ sB-
K+π → sB-
p K→ bΛ-π p → bΛ
Particle IDNo RICH
0 20 40 60 80 100 0
20
40
60
80
100
Momentum (GeV/c)
Eff
icie
ncy
(%
)
Κ → Κ
π → Κ
Kaon ID: ~88%
Pion mis-ID: 3%
� Low momentum – Kaon flavour tag (b→c→s)
� High momentum –Background rejection for exclusive B decay reconstruction
ππ
hypothesis
B→h+h-
27/4/2006 UK SuperB Factory Workshop 12
Flavour tagging
�Most powerful tag is opposite kaon
(from b→c→s)
� Combined εεεεD2 ~ 6.9% (Bs) or 4.8% (B0)
� Multivariate approach ~9% for Bs
Qvtx
BsB0
D
l-K–
K+PV
SV
2.1%Same side K±(Bs)
1.0%Jet/vertex charge
2.4%K±
0.4%e±
1.0%µ±
εD2 = ε(1–2w)2Tag
27/4/2006 UK SuperB Factory Workshop 13
LHCb Physics Programme Sampler
� Bs mixing phase and lifetime difference
� Bs→J/ψφ
� Several routes to γ
� Bs→ DsK – tree only
� Bd→ π+π- and Bs→ K+K- – tree and penguin
� B-→D0K- and B0→D0K*0 – tree and D0 mixing
� α with Bd→ ρπ
� Rare decays
� Bs→µ+µ-
� Bd→K *0 µ+µ-
� Bd→ K *0γ and Bs→ φγ
27/4/2006 UK SuperB Factory Workshop 14
� Bs analogue of Bd →J/ψKs measures the Bs mixing phase
� φs = –arg(Vts2) = –2λη2 ~ –0.04 in SM
� Large CP asymmetry would signal Physics Beyond SM
� J/ψφ is not a pure CP eigenstate� Admixture of 2 CP even and 1 CP odd amplitudes
� Need to fit angular distributions of decay final states as function of proper time
� Requires external ∆ms from Bs→Dsπ
� Exploits excellent proper time resolution
� 1 year predictions with ∆∆∆∆ms = 20 ps-1
� 125k events with B/S~0.5
� σσσσ(sin φφφφs)~0.031
� σσσσ(∆Γ∆Γ∆Γ∆Γs /ΓΓΓΓs)~ 0.011
� 3σ SM sensitivity to sin φs after 5 years
� Also add pure CP states Bs→J/ψη(‘)
φs and ∆Γs from Bs→J/ψφ
27/4/2006 UK SuperB Factory Workshop 15
γ from Bs → DsK
� 2 amplitudes (b→c and b→u) of same magnitude (~λ3) interfere via
Bs mixing
� insensitive to new physics
� large interference effects expected
� 2 time-dependent asymmetries
� Bs (Bs) → D-s K+ and Bs (Bs) → D+
s K-
� 5400 signal events/year with B/S<1
� PID and mass resolution reduce
contamination from Bs→ Dsπ ~ 10%
Bs→→→→DsK
Bs→→→→Dsππππ
s sb c
us
B s
0 { }D s
−
}K+
}K–
s sb u
cs
B s
0 {}D s
+
27/4/2006 UK SuperB Factory Workshop 16
−0.5
−0.25
0
0.25
0.5
Asy
m (
Ds −
K+)
t [ps]
Asy
m (
Ds +
K−)
−0.5
−0.25
0
0.25
0.5
0 0.5 1 1.5 2 2.5 3 3.5 4
DsK asymmetries (5 years, ∆∆∆∆ms =20 ps–1)
Ds–K+
Ds+K–
γ from Bs → DsK
� Fit 2 time-dependent asymmetries� phase of D−
s K+ = ∆ + (γ + φs)
� phase of D+s K− = ∆ −−−− (γ + φs)
� φs from Bs → J/ψφ to extract ∆and γ
� 1 year sensitivity: � Assuming ∆ms = 20 ps-1 and -
20°<∆<20°
� σ(γσ(γσ(γσ(γ)))) ~ 14°
� Statistically limited
� 8-fold ambiguities in γ can be resolved� If ∆Γs large enough, or
� B0→Dπ and U-spin symmetry
27/4/2006 UK SuperB Factory Workshop 17
γ from B0→π+π− and Bs→K+K−
� Large penguin contributions in both decays
� Sensitive to New Physics
� Measure time-dependent CP asymmetry for B0→π+π− and Bs →K+K−
� ACP(t) = Adir cos(∆mt) + Amixsin(∆mt)
� Adir and Amix depend on γ, mixing phases, and ratio of penguin-to-tree amplitudes (d eiθ)
� Exploit “U-spin” symmetry (d↔s)
� dππ = dKK and θππ = θKK
� Mixing phases from golden modes
� 4 measurements and 3 unknowns,
1 year yields and sensitivity:
� 26k B0000→π→π→π→π++++ππππ−−−− and 37k Bs→→→→K++++K−−−−,
� σ(γσ(γσ(γσ(γ) ∼ 5) ∼ 5) ∼ 5) ∼ 5°
γ (°)
d
Bs → K+K−
(95% CL)
B0 → π+π−
(95% CL)
Bd/s
Bd/s
π/K
π/K
π/K
π/K
R.Fleischer, Phys.Lett. B459, 306 (1999)
27/4/2006 UK SuperB Factory Workshop 18
� Dunietz variant of Gronau, London and Wyler method
� Exploits interference between two colour-suppressed diagrams
� Measure 6 decay rates: B0 →D0(Kπ,πK,KK)K*0 + CP conjugates
� Allows γ and other parameters to be extracted without flavour tagging or proper time determination
� 80 precision on γ with one year’s data
γ from B0 �D0K*0
d
b
ds uc
B0
}D 0
}K*0
}D0
d
b
ds cu
B0 }K*0
A1 = �A1
A2
�A2 = A2 e−2iγA3
A4
γ∆
γ
A1 = A(B0 → D0K*0): b→c transition, phase 0
A2 = A(B0 → D0K*0): b→u transition, phase ∆+γ
A3 = √2 A(B0 → DCPK*0) = A1+A2, because DCP=(D0+D0)/√2
= strong phase
27/4/2006 UK SuperB Factory Workshop 19
B± →DK±Similar to B0-two interfering tree processes
Now one diagram colour suppressed
• γ – b→u , b→c interference
• rB – the ratio in magnitude of two diagrams (0.1 – 0.2)
• δB – a CP conserving strong phase difference
Look for decays common to Do and Do to access
interference effects, which depend on 3 parameters:
1. Cabbibo favoured self-conjugate decays e.g. Ksππ, KsKK, KKππ
Preliminary Ksππ studies 6k events/year with B/S ~O(1)
2. Cabbibo favoured/doubly Cabbibo suppressed modes e.g. Kπ, KπππOne year γ sensitivity 50
Two types of D0 decay understudy:
−
u
bB
0D
u
c
−
Ku
s
−
u
b
B−
Ku
s
0D
c
u
27/4/2006 UK SuperB Factory Workshop 20
Angle α from Bd →π0π–π+ decays
�Dalitz plot analysis (Quinn Snyder method)
�Bd→π0π–π+ selection based on
multivariate analysis
�Use resolved and merged π0
�Expect 14k events per year B/S < 1
� Toy MC study:
� 11-parameter likelihood
fits performed in time-
dependent Dalitz space
� B/S = 0.8
(flat and resonant bkg)
ρ0π0
ρ–π+
ρ+π–
m2(π0π+)
m2(π
0π–
)
Combined discriminant variable
1 year σσσσ(αααα) ~10°
ααααgen=106°
27/4/2006 UK SuperB Factory Workshop 21
s = (mµµ)2 [GeV2]
AFB(s) for B0→→→→K*0µµµµµµµµ
Rare decays with leptonsBs→µ
+ µ-
� BR ~ 3.5 × 10–9 in SM, can be strongly enhanced in SUSY
� LHCb has prospect for significant measurement� ~30 events/year
� Full simulation: 10M incl. bb events + 10M b→µ, b→µ events (all rejected)
� Sensitivity to SM Bd→µ+ µ- which has SM
BR ~ 8×10-11
s(GeV^2)0 2 4 6 8 10 12 14 16 18 20
FB
A
-0.5
-0.4
-0.3
-0.2
-0.1
-0
0.1
0.2
0.3
0.4
Expt20
B0+B0bar FBA
Fit to FBAB→K*0µ+ µ-
� AFB very sensitive to new physics
� Expect 4.4k events in 1 year� B/S < 2.5
� In 5 years 13% sensitivity to s(AFB=0)
27/4/2006 UK SuperB Factory Workshop 22
B0→ K0* γ and Bs → φ γ� B→K0* γ expected direct
CP violation Acp<0.01
� 35k/year B/S>0.7
� B→φγ TDCPV zero in SM � Sensitive to same new
physics as TDCPV in B0→ K*0(K0
sπ) γ� Selection optimises proper
time resolution
� 9.49.49.49.4k/year B/S>2.5
� Sensitivity studies in progress
σσσσm~ 64 MeV/c2
B→ Kππππ γγγγ
Bs→ KK γγγγ
σσσσττττ~ 60 fs
mKπ[GeV]
τtrue-τrec [ps]
27/4/2006 UK SuperB Factory Workshop 23
…and much, much more
� Other CP measurements, for example
� sin 2β with B→J/ψK0S
� sin (2β+γ) with B→D*π
� α with B→ρ0 ρ0
� φ s with Bs → φ φ (gluonic penguin)
� Other rare decays e.g Bs → φ µµ� Other areas to be explored
� B baryons
� Bc physics – 14k/year in Bc → J/ψ π
� Charm physics (300 Hz of D*+→D0(h+h-)π+)
� Control samples for systematic uncertainties i.e. B+→J/ψK+
27/4/2006 UK SuperB Factory Workshop 24
-0.5 -0.4 -0.3 -0.2 -0.1 -0 0.1 0.2 0.3 0.4 0.5
|ub
|V
K)s
D→s
(Bγ KK)→
s(Bγ
)*
(DKγ
)π ρ(α isospin)ππ(α
βsin 2)ντ D→0BR(B
)ντ D→+BR(B
)νν+ K→+
BR(B
)µµ →s
BR(B
ll)*
K→(BFB
A10
C
ll)*
K→(BFB
A9
C
)γs
X→(BCP
A
)γs
X→BR(B)γ*0
S(K
)s
φsin()
0
S K
0π S(∆)
0
SK
0
SK
0
S S(K∆
)0
S’ Kη S(∆
)0
S K
- K
+ S(K∆
)0
S Kφ S(∆
Comparison to Super B
� This was shown by N.
Katayama at FCPC a
couple of weeks ago
� At first glance I’m
working on the wrong
experiment!
� But:
� LHCb ~2010
� SuperB ~2020
� Some missing LHCb info
SuperB (50 ab-1) LHCb (2 fb-1)
27/4/2006 UK SuperB Factory Workshop 25
-0.5 -0.4 -0.3 -0.2 -0.1 -0 0.1 0.2 0.3 0.4 0.5
|ub
|V
)γs
X→BR(B)ντ D→0BR(B
)ντ D→+BR(B
)νν+ K→+
BR(B
isospin)ππ(α)γ*0
S(K
)0
S K
0π S(∆)
0
SK
0
SK
0
S S(K∆
)0
S’ Kη S(∆
)0
S K
- K
+ S(K∆
)0
S Kφ S(∆
ll)*
K→(BFB
A10
C
ll)*
K→(BFB
A9
C
)γ)*/Ks
(X→(BCP
A)
*(DKγ
)π ρ(αβsin 2
K)s
D→s
(Bγ KK)→
s(Bγ
)µµ →s
BR(B
)s
φsin(
Comparison to Super B
� Added some
information on
several modes
� Scaled LHCb to
10 fb-1 luminosity
(~2014) and
reordered the
measurements
� Symbiosis!
Incl
usi
ve/ν
No I
PB
sC
om
mon
27/4/2006 UK SuperB Factory Workshop 26
Possible LHCb upgrades
� Simulation studies indicate we can run at 5×10-32cm-2s-1 and gain in statistics
� Particularly dimuons
Bo→→→→ππππ+ππππ-
BS→→→→φγφγφγφγBS→→→→J/ψφψφψφψφBS→→→→DSK-
� Vertex detector will be replaced because of radiation damage
� Very radiation hard technologies would allow detectors to be closer to the
beam
� Pixels could be used in 1st level of the trigger to improve selection of
hadronic modes-potentially allow running above 5×10-32cm-2s-1
� ECAL inner region replaced by PbWO4 to improve neutral
performance
Hadronic/photonic modessaturate allotted bandwidth
27/4/2006 UK SuperB Factory Workshop 27
Conclusions
� LHCb will be ready for data taking next year
� A large number of measurements will be made
during the lifetime of the experiment
� Largely complimentary to Super B programme
� Performance might be enhanced with upgrades to
vertexing, triggering and electromagnetic
calorimetry
27/4/2006 UK SuperB Factory Workshop 28
0 1 2 3 4 5 6 7 8 9 10-0.8
-0.6
-0.4
-0.2
0
0.2
ACP
Proper time (ps)
sin(2β) from B0→J/ψ KS� “gold-plated” decay channel at B-factories for measuring the Bd- Bd mixing phase
� needed for extracting γ from B → π π and Bs → K K, or from B → D*π
� in SM ~0, non-vanishing value O(0.01) could be a signal of Physics Beyond SMdir
CPA
ACP(t) (background subtracted)
LHCbOne of the first CP measurements at LHC:
� demonstrate CP analysis performance
� study tagging systematics
Expected sensitivity:
� LHCb: 240k signal events/year
� σstat(sin(2β)) ~ 0.02 (1year, 2fb-1) (�σ(β)∼0.6°)
Search for direct CP violating term…
27/4/2006 UK SuperB Factory Workshop 29
B- →D0(K+π-)K-
� Both D0 and D0 → K+π- :
Doubly Cabbibo suppressed Cabbibo favoured
� For these decays the reversed suppression of the D decays relative to the B decays results in much more equal amplitudes → big interference effects
� Counting experiment
� Interference depends on 5 parameters :
� From the B decays γ, rB and δB
� rDKπ – the ratio in magnitude of two D decay processes
� Well measured (PDG value 0.060)
� δDKπ – a CP conserving strong phase difference
B-→D0K- (colour
favoured) then :
B-→D0K- (colour
suppressed) then :
Atwood, Dunietz and Soni
u
cD
0
+
Ks
u
−
π
u
d
u
cD
0 +
Ku
s
−
π
u
d
27/4/2006 UK SuperB Factory Workshop 30
B- →D0(K+π-)K-
� Have 4 B±→D(Kπ)K± rates we can measure:
� Two rates are favoured (1) and (3)
� Two rates are suppressed (2) and (4)
– but suppressed rates have O(1) interference effects as rB ~ rD
� Taking the relative rates have more unknowns than equations –need information from other decays eg. D → Kπππ or the CP eigenstates KK, ππ (rD
KK=1, δDKK=0)
(1)
(2)
(3)
(4)
27/4/2006 UK SuperB Factory Workshop 31
ADS 1 year sensitivity studies� Event yields
� 60,000 favoured
� 2,000 suppressed
� B/S = 0.5 for both
� Fit robust over range of strong D decay strong phases
6.906.005.905.605
5.505.305.105.002
5.004.804.804.601
4.104.004.003.900
B/S
Kπππ
5210
B/S Kπ
1000 toy experiments-no background