1. FRONTIERS OF MATTER XI th RENCONTRES DE BLOIS
Chateau de Blois, France
June 27 - July 3, 1999
A Next Generation B-physics CP Violation Experiment
The Expected Physics Performance
Paul Colrain (CERN)

2. History and Future
August : Letter of Intent for a new collider mode b experiment
at the LHC to exploit the b physics potential
(30 institutes, 171 collaborators)
February : Technical Proposal (42 institutes, 336 collaborators)
September : Approval
: Technical Design Reports
: Production and Installation
? : Data Taking
From day 1 of LHC Operation for many years

3. The Collaboration
49 institutes

4. The Physics : What is the origin of CP Violation?
The CKM Unitarity Triangles in 2005 (~108 bb):
Vtd Vtb + Vcd Vcb + Vud Vub = 0
Vtd Vud + Vts Vus + Vtb Vub = 0
Bd , , D* 
|Vub|
xs Bs  Ds  xs
|Vub|
BD*
BDK*, BsDsK
Bd  J/ Ks  
 Bs  J/ 
sin2 measured to  0.05 by BaBar, Belle, HERA-B, CDF, D0
sin2 measured by BaBar, Belle (+CDF, D0 ?) with low statistics and
and potentially serious theoretical uncertainties
sin(2+) measured by BaBar and Belle
 not measured
No direct  measurement
xs measured by CDF, D0 (if xs  40)  |Vub| measured but with large hadronic error

5. The Physics (Continued)
CP Violation in 2005 :
Either Standard Model is “Alive” !
1st Generation  and Mixing measurements and Kaon results are Consistent (within error) with SM interpretation of CKM matrix
Or Standard Model is “Dead” !
 and Mixing measurements and Kaon results are Inconsistent with SM
 New Physics !
Either Way What is the Origin of CP Violation ?
CKM matrix must be Over-Constrained :
With Higher Statistics measure the same parameters (, , 2+) using the same channels
Cross-check the same parameters using New Channels (BR  10-7)
Measure New Parameters (, )
Study the Bs Sector
 Next Generation CP Violation Experiment at LHC

6. The Physics (Continued)
LHC provides High statistics,
L  2  1032 cm-2s-1, bb  500 b
 Nbb  1012/year
and All species of B hadrons, including Bs
LHCb is designed specifically to exploit this b physics potential :
Efficient Trigger
Particle Identification(e,,,K,p)
- High pt hadron trigger
- High pt lepton trigger
- Secondary vertex trigger
- Background Suppression (/K separation)
- Flavour Tagging (, e, K)
Good Mass Resolution
Good Proper Time Resolution
- Background Suppresion
- Background Suppresion
- CP Asymmetry in Bs

7. The Detector Single Arm Spectrometer : 15 mrad <  < 300 mrad
Beam-pipe,
radiation
Cost v Statistics
b and b produced predominantly at low 
 good acceptance (~40%) for both b and b
Essential for tagging
Forward geometry
 low threshold on trigger pt cuts
 efficient trigger

8. The Vertex Detector 17 Silicon Strip (r,) Detectors
inside the Beam Pipe
at 1cm from the beam
during physics
Retractable by 3cm during injection
Provides excellent vertex and proper
time resolution :
Primary Vertex resolution = 40 m (along beam axis)
Proper time resolution = 40 fs

9. The RICH Detectors RICH 1 RICH 2 Pattern Recognition in RICH 1
Photodetectors
Pattern Recognition in RICH 1
red dots are detected photo-electrons
black circles are reconstructed rings
RICH RICH 2
upstream downstream
1 < p < 70 GeV/c
20 < p < 150 GeV/c
Small circles C4F10
Large circles Aerogel

10. Particle Identification with RICH
-K separation > 3 for 1 < p < 150 GeV/c
Suppression of same topology backgrounds
Flavour tagging (b  c  K)
Example : B  +- ()

11. The Detector (Continued)
Tracking System (11 stations)
Inner tracker : Micro Strip Gas Chambers (MSGC) and
(40cm60cm)
p/p = 0.3% for
Gaseous Electron Multipliers (GEM)
Outer Tracker : Straw Tube Drift Chambers
5<p<200GeV/c
Magnet : Warm Dipole, 4 Tm Field Integral
Calorimetry
Pre-Shower : Single Pb layer and Scintillators
ECAL : “shashlik”, 25 X0
(E)/E = 0.1/E  0.015
HCAL : Fe and Scintillating Tiles, 5.6 
(E)/E = 0.8/E  0.05
Muon System
Cathode Pad Chambers (CPC) in high rate regions and either
Resistive Plate Chambers (RPC) or
Wire Pad/Strip Chambers (WPC) in low rate regions
Calorimetry and Muon System = 22

12. The Trigger
Challenge : incl/bb  160, input rate = 40 MHz, output rate = 200 Hz
Efficient : High pt leptons and hadrons at L0
Flexible : Multilevel with different ingredients
Robust : Evenly spread data reduction at each level
Level Description Detectors Data rates Latency
high pt muon (~20%) Muon Chambers
high pt electron (~10%) ECAL
high pt hadron (~60%) ECAL+HCAL
high pt photon ECAL
pile-up veto Dedicated Si disks MHz  1 MHz s
identification of secondary
vertices Vertex Detector MHz  40 kHz s
refined secondary vertices Vertex Detector +
(SW) Tracker kHz  5 kHz ms
reconstruction of specific
decay modes (SW) All Detectors kHz  200 Hz ms
25% b purity

13. The Trigger (Continued)
Trigger efficiencies (%, for reconstructed and tagged events) :
L L L2 Total
 e h all
BdJ/(ee)KS + tag
BdJ/()KS + tag
BsDsK + tag
BdDK      
Bd + tag
Lepton trigger Hadron Trigger
Trigger Efficiency
~30%
The Flavour Tag
Uses the decay products from the accompanying b-hadron
b  e or  and b  c  K (Jet Charge Tag not yet studied)
Overall efficiency(K-tag dominant) = 40%, mistag rate = 30%

14. Direct Measurement of 
Extract  from the relative rates of :
(K* tags the flavour of the parent Bd)
Bd  D0 K*0 events
hadron trigger
-K separation
Visible BRs ~ 
Performance (1 year) :
m= 13 MeV/c2
No of events  350 (50) D0K*0 (D0K*0)
S/B  1
()  10

15. Measurement of -2
Extract -2 from the 4 BsDsK time-dependent decay rates
Indirect measurement of  ( from BsJ/)
Visible BR ~ 10-6
BsDs background 
Bs oscillations
Hadron trigger
-K separation
good proper time resolution t
Performance (1 year) :
No of events  2500
S/B  10
(-2)  6-13
Precision depends on , xs and strong
Negligible theory error(no penguins)    1/Nyears

16. Measurement of 
Extract  from time-dependant CP Asymmetry in Bs  J/ 
 Counterpart of BdJ/ Ks
 In SM  ~ 10-2  good place to look for new physics
J/  is a mixture of CP-even and CP-odd states
 dilution of CP Asymmetry
 need angular analysis to separate contributions
bb
efficient trigger
good proper time resolution, t
Visible BR ~ 10-5
Bs oscillations 
Performance (1 year) :
()  0.6
 SM sensitivity in 1 year

17. LHCb CP Sensitivities in 1 year
bb and trigger
LHCb CP Sensitivities in 1 year
Parameter Channels No of events (1 year) LHCb feature
 Bd + c.c
(2+ = +-) |P/T| = -5 -K sep.
|P/T|=0.20 ?? -K sep.
Bd  D*  -K sep.
 BdJ/Ks 
-2 Bs DsK -13 -K sep., t
 Bd  DK*  -K sep.
 Bs  J/  t
Bs oscillations
xs Bs  Ds upto t
Rare Decays
Br Bs   <2 t
No Bd  K*  photon trigger

18. Summary LHCb is a 2nd Generation CP Violation Experiment :
 Massive Statistics
 ~1012 bb events per year (Bd, Bs, b baryons,...)
 trigger efficient in all modes (hadron trigger)
 Particle Identification
 negligible background systematics in CP measurements
 efficient flavour tag (Kaon)
 Excellent proper time resolution (t ~ 40 fs)
 Precision measurements in Bs system
LHCb offers a unique opportunity to improve our understanding of the origin of CP Violation either within the framework of the SM or Beyond !