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Overview of LHCb
XXXXth Rencontres de Moriond QCD AND HIGH ENERGY
HADRONIC INTERACTIONS Spectroscopy
On behalf of the LHCb Experiment
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Overview of LHCb
Contents - Physics Motivations - LHC
environment - LHCb expected performance
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Physics Motivations
CKM fit (ICHEP 2004)
- BABAR, BELLE, Tevatron and kaon experiments
have tested and will test CKM picture of CP
violation (no clear hint
of NP for the moment)
- NP could still be hidden in box and loop
diagrams
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Physics Motivations
LHCb will study all types of B mesons !
B0s system
B0d system
B0 -gt rr,pp,rp (s(a)100)
B0s -gt J/yf,ff
B0 -gt J/y Ks, J/yp0,fKs (s(b)0.70)
B0s -gt DsK, KK
B0 -gt DK, D? (s(g)100-200)
(Expected sensitivities of B factories in 2007)
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LHC environment

• LHC pp collisions at ?s 14 TeV (40 MHz)
• bb pairs are mostly produced at small angles
  wrt beam pipe
  --gt forward spectrometer
• L 2.1033 - 1034 cm-2s-1
• to avoid high number of interaction / bunch
  crossings L 2 .1032 cm-2s-1 for LHCb
• --gt simpler events and less radiation damage
  for the detectors
• sinelastic ? 80 mb and sbb ? 0.5 mb
• --gt need an efficient trigger
• but Nbb (1 year in 4p) 1012
• with B / B0d / B0s / b-baryon
• (4 4 1 1 )

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Trigger

• multi-level trigger
• - Level 0 (40 MHz --gt 1 MHz)
• reject complicated events
• high pT e, g, p0,m, or hadrons
• - Level 1 (1 MHz --gt 40 KHz)
• large IP and pT tracks
• - HLT (40 KHz --gt 200 Hz)
• access to complete events
• offline selection
• 1.8 KHz to get systematics from data
• high dimuon mass --gt tracking
• inclusive b (b?m) --gt trigger data
  mining
• D --gt PID

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LHCb detector requirements
K-
few mm
B0s
K
p
p
Primary vertex

• Efficient particle identification
• - p/K separation (1--gt100 GeV) --gt RICH (for
  B0(s) --gt hh, flavour tagging, )
• - electron and muon ID --gt CALO MUON (for
  B0(s) --gt J/y X, flavour tagging, )
• Good decay time resolution ( 40 fs)
• - vertex detector (for B0s --gt Dsp, B0s --gt J/y
  f, ...)
• The best mass resolution and efficient tracking
• - tracker and magnet

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LHCb experiment
Single arm forward spectrometer
250/300 mrad v / h
Acceptance
10 mrad
pp collision
side view
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Vertex Locator
Vertex and tracking detector - silicon discs
- 8 mm from beam axis - 21 stations
(retractable)
Interaction region
stations
PV position resolution 8 mm (x,y) and
44 mm (z) IP precision 40 mm
Vacuumvessel
1 m
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Bs oscillation frequency Dms
LEP SLD -gt ?msgt 14.4 ps-1 Important physics
subject of CDFD0 Needed for the observation of
CP asymmetries with Bs decays Use Bs ?Ds???
(80k evts/year expected) If ?ms 20 ps?1 ?(?ms)
0.011 ps?1 Can observe 5? oscillation signal if
?ms lt 68 ps?1 (well beyond SM prediction)
Propertime resolution
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RICH
B0s --gt KK
B0s --gt KK
2 RICHs and 3 Cherenkov radiators to cover the
full momentum range
good p/K separation for 2ltplt100 GeV
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Calorimeter System
With Bremsstrahlung recovery
SPD/PS (2X0) ECAL (25X0) lead/scintillator HCAL
(5.7l) iron/scintillator Readout every 25
ns (L0 trigger) Identification electrons,
hadrons and p0 ECAL sE/E 10 / ?E ? 1 HCAL
sE/E 80 / ?E ? 10 ?e e? e? 94 and?e p ?
e? 0.7 for tracks in ECAL acceptance
(? 60 MeV/c²)
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Muon System
(? 10 MeV/c²)
5 stations with 1380 MWPCs Projective
geometry Each station subdivided into four regions
?em? m ? 93 ?ep ? m ? 1.0 for tracks in
Muon detector acceptance
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Many Physics Topics at LHCb

• - Measurement of a angle
• B -gt rp (12k evts/year) s(a) lt 100 (1 year)
• - Measurement of b angle
• B -gt J/yKs (240k evts/year) s(b) 0.70 (1
  year)
• - Measurement of g angle
• with Bs-gtDsK, B-gtpp and Bs-gtKK, B-gtDK decay
• - Measurement of Bs mixing angle c
• with Bs-gtJ/yf decay
• - New physics in b -gt s penguin process
• B -gt Kg , B -gt fKs , Bs -gt ff, fg
• D physics
• Mixing, CPV
• - Rare decays
• Bs -gt mm, B -gt K mm
• - Bc physics, b baryons
• lifetimes, masses, branching ratios

I will give more details hereafter
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B0s Mixing Phase (c)
- needed for some g measurements - use Bs-gtJ/yf
(120k evts/year expected)
Angular analysis to separate CP even and CP odd
s(sin 2c)0.06 and s(DGs/Gs)0.02 (with Dms
20 ps-1)
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Measurements of angle g possible scenario

• 1. Bs-gtDsK
• (s(g)?14-150)

2. B-gtpp, Bs-gtKK (s(g)?4-60)
3. B-gtDK (s(g)?7-80)
g not affected by new physics in loop diagrams
g affected by possible new physics in penguin
Determine the CKM parameters A, r, h independent
of new physics
Extract the contribution of new physics to the
oscillations and penguins
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Conclusion

• LHC offers great opportunity for B physics
• LHCb is dedicated to b Physics with
• Efficient trigger for b physics
• Excellent vertex and momentum resolution
• Excellent particle identification
• Access to all b-hadron species
• Promising potential for studying New Physics
• Construction of the experiment is on the way

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Back Up Slides
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CKM fit (ICHEP 2004)
Adding ? and ? measurements
Adding ? measurements
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RICH PID performance
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Bs -gt DsK diagrams
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B0d(s) -gt hh diagrams
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B0d-gt DK diagrams