Transcript No Slide Title

XI th RENCONTRES DE BLOIS
FRONTIERS OF MATTER
Chateau de Blois, France
June 27 - July 3, 1999
A Next Generation B-physics CP Violation Experiment
The Expected Physics Performance
Paul Colrain (CERN)
History and Future
• August 1995
: Letter of Intent for a new collider mode b experiment
at the LHC to exploit the b physics potential
•
(30 institutes, 171 collaborators)
• February 1998 : Technical Proposal (42 institutes, 336 collaborators)
• September 1998 : Approval
• 2000 - 2002
: Technical Design Reports
• 2002 - 2004
: Production and Installation
• 2005 - ?
: Data Taking
From day 1 of LHC Operation for many years
The Collaboration
49 institutes
The Physics : What is the origin of CP Violation?
The CKM Unitarity Triangles in 2005 (~108 bb):
Vtd Vtb + Vcd Vcb + Vud Vub = 0
|Vub|
Bd , , D*

xs Bs  Ds 
BD*

•
•
•
•
•
Vtd Vud + Vts Vus + Vtb Vub = 0
xs
|Vub|
Bd  J/ Ks
BDK*,
BsDsK

 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
xs measured by CDF, D0 (if xs  40)
 not measured
•

|Vub| measured but with large hadronic error
No direct  measurement
The Physics (Continued)
CP Violation in 2005 :
Either
Standard Model is “Alive” !
Or
Standard Model is “Dead” !
1st Generation  and Mixing measurements and Kaon results are
Consistent (within error) with SM interpretation of CKM matrix
 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
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
- High pt hadron trigger
- High pt lepton trigger
- Secondary vertex trigger
• Good Mass Resolution
- Background Suppresion
• Particle Identification(e,,,K,p)
- Background Suppression (/K separation)
- Flavour Tagging (, e, K)
• Good Proper Time Resolution
- Background Suppresion
- CP Asymmetry in Bs
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
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
The RICH Detectors
Photodetectors
Pattern Recognition in RICH 1
• red dots are detected photo-electrons
black circles are reconstructed rings
RICH 1
RICH 2
upstream
downstream
1 < p < 70 GeV/c
20 < p < 150 GeV/c
Small circles C4F10
Large circles Aerogel
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  +- ()
The Detector (Continued)
Tracking System (11 stations)
• Inner tracker : Micro Strip Gas Chambers (MSGC) and
(40cm60cm)
Gaseous Electron Multipliers (GEM)
• Outer Tracker : Straw Tube Drift Chambers
• Magnet
: Warm Dipole, 4 Tm Field Integral
p/p = 0.3% for
5<p<200GeV/c
Calorimetry
• Pre-Shower : Single Pb layer and Scintillators
• ECAL
: “shashlik”, 25 X0
• HCAL
: Fe and Scintillating Tiles, 5.6 
(E)/E = 0.1/E  0.015
(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
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
0
1
2
3
Detectors
high pt muon (~20%)
Muon Chambers
high pt electron (~10%)
ECAL
high pt hadron (~60%)
ECAL+HCAL
high pt photon
ECAL
pile-up veto
2 Dedicated Si disks
identification of secondary
vertices
Vertex Detector
refined secondary vertices Vertex Detector +
(SW)
Tracker
reconstruction of specific
decay modes (SW)
All Detectors
25% b purity
Data rates
40 MHz  1 MHz
Latency
4.0 s
1 MHz  40 kHz 512-2048 s
40 kHz  5 kHz
10.0 ms
5 kHz  200 Hz
200.0 ms
The Trigger (Continued)
Trigger efficiencies (%, for reconstructed and tagged events) :
L0
L1
L2
Total
 e h all
BdJ/(ee)KS + tag 17 63 17 72
BdJ/()KS + tag 87
6 16 88
42
50
81
81
24
36
BsDsK + tag
15
56
92
28
BdDK

Bd + tag
14
9 45

54
31 
8 70
76
Lepton trigger

48

Trigger Efficiency
~30%

83
30
Hadron Trigger
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%
Direct Measurement of 
(K* tags the flavour of the parent Bd)
Visible BRs ~
10-8

Bd  D K * ,
DK * ,
DCP K *
Bd  D K * ,
D K * ,
DCP K *
 K  
 K  
hadron trigger
 K K  ,   
Bd  D0 K*0 events
-K separation
Performance (1 year) :
• No of events  350 (50) D0K*0 (D0K*0)
• S/B  1
()  10
m= 13 MeV/c2
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
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
10-5
Visible BR ~
Bs oscillations

Performance (1 year) :
bb
efficient trigger
good proper time resolution, t
()  0.6
 SM sensitivity in 1 year
LHCb CP Sensitivities in 1 year
Parameter

Channels
No of events
Bd + c.c.
6900
(2+ = +-) |P/T| = 0
|P/T|=0.200.02
Bd  D*
446000

BdJ/Ks
45000
-2
Bs DsK
24000

Bd  DK*
400

Bs  J/
44000
Bs oscillations
xs
Bs  Ds
120000
Rare Decays
Br
Bs  
No.
Bd  K * 
26000
(1 year)
2-5
??
9
0.6
6-13
10
0.6
upto 75
<210-9
bb and
trigger
LHCb feature
-K sep.
-K sep.
-K sep.
-K sep., t
-K sep.
t
t
t
photon trigger
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 !