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Olivier Schneider
6th International Conference on B-physics at Hadron Machines
BEAUTY ’99Bled, Slovenia, June 21-25, 1999
Olivier.Schneider@cern.ch
Overview of the
LHCb experiment
LHCb collaboration
Finland: Espoo-Vantaa Inst. Tech.
France: Clermont-Ferrand, CPPM Marseille, LAL Orsay
Germany: Humboldt Univ. Berlin, Univ. Freiburg, Tech.
Univ. Dresden, Phys. Inst. Univ. Heidelberg,
IHEP Univ. Heidelberg, MPI Heidelberg,
Italy: Bologna, Cagliari , Ferrara, Genoa, Milan,
Univ. Rome I (La Sapienza) ,
Univ. Rome II (Tor Vergata)
Netherlands: Univ. Amsterdam, Free Univ. Amsterdam,
Univ. Utrecht, FOM
Poland: Cracow Inst. Nucl. Phys., Warsaw Univ.
Spain: Univ. Barcelona, Univ. Santiago de Compostela
Switzerland: Univ. Lausanne, CERN
UK: Univ. Cambridge, Univ. Edinburgh,
Univ. Glasgow, IC London, Univ. Liverpool,
Univ. Oxford
Brazil: UFRJ (Rio de Janeiro)
China: IHEP(Beijing), Univ. Sci. and Tech.(Hefei),
Nanjing Univ., Shandong Uni.
Russia: INR, ITEP, Lebedev Inst., IHEP,
PNPI (Gatchina)
Romania: Inst. of Atomic Phys. Bucharest
Ukraine: Inst. Phys. Tech. (Kharkov),
Inst. Nucl. Research (Kiev)
U.S.A.: Univ. Virginia, Northwestern Univ., Rice Univ.
O(500) participants from 49 institutes (11.6.99)
Why one more B-physics experiment
?
and then how ...
O. Schneider, Beauty 99 4
Introduction
Before 2005, various experiments will explore unitarity triangle:
well measured
with Bd J/ KS, (sin 2) < 0.05
no good/direct measurement
low statistics measurement with Bd ,theoretical uncertainty
Bd and Bs mixing measured
b u measured,hadronic uncertainty
Constraints on triangle will indicate:– consistency with SM within errors,– or inconsistency with SM (which will not be fully understood)
In any case:
Next generation experiments at LHC needed for full investigation of CP violation:– precision (high stat.) measurements on many Bd and Bs decay channels– aim for theoretically clean channels (not necessarily easiest experimentally)– overconstrain CKM matrix, including terms beyond O(3)
O. Schneider, Beauty 99 5
CKM matrix (in SM)
CP violation is due to ≠
i
iV(3)
VCKM V(3) + V
VudVusVub
VcdVcsVcb
VtdVtsVtb
iii
V
O. Schneider, Beauty 99 6
Unitarity triangles
O(10-2) in SM
O. Schneider, Beauty 99 7
Effect of new physics in Bd mixing
Within Standard ModelWithin Standard Model
Bd → J / KSdecay∝ Vcb* Vcs
arg Vcb* Vcs( ) =
Bd − Bbmixing∝ Vtb* Vtd( )
∝ −( )+ ⎡
⎣⎤⎦exp−i( )
extracted from md measurement
extracted from J/KS CP asymmetry
In presence of new physics in Bd mixingIn presence of new physics in Bd mixing
Bd − Bbmixing
∝ −( )+ +rnew
⎡⎣
⎤⎦exp−i +φnew( )( )
extracted from md measurement
extracted from J/KS CP asymmetry
O. Schneider, Beauty 99 8
Effect of new physics in Bd mixing (cont.)
triangle looks consistent with SM because
sides and J/K agree within experimental uncertainties
Possible scenario in 2005Possible scenario in 2005
need precise measurements of to realize that sides ≠ andhence discover new physics
1
−( )
+ + rnew from measuredmd
−( )
+ from SM
+
from SM
+ from
measuredb → u
0
+φnew from measuredCP asymmetry inJ / KS
sides
J/K
sides
O. Schneider, Beauty 99 9
Bd D*-n+, D*+n-
arg(mixing) =− +φnew( )
arg(Vcb* Vud ) =
arg(Vub* Vcd ) =
CP asymmetries in these decays allow to extract
new J/K and hence using already measured J/K
Similar story with Bs decaysSimilar story with Bs decays
snew from CP in Bs J
snew from CP in Bs Ds
K, Ds
K
clean extraction of (~ insensitive to new physics in Bs mixing)
O. Schneider, Beauty 99 10
Dedicated B physicsexperiment at LHC
Requirements for LHCb:
• reasonable acceptance for bothb-hadrons in event(needed for tagging)
• good proper time resolution (ability to resolve fast Bs oscillations)
• include hadronic final states of interest in trigger (e.g. Bd )
• ability to reduce background– good mass resolution– good particle identification
b b ≈μb b b ≈μbLHC’s advantage:
• large b production cross section• large luminosity
L > cm- s− L > cm- s−
possibility to study many Bs,d,u decayswith branching ratios as low as 10-7
O. Schneider, Beauty 99 11
LHCb acceptance
forward geometry with single-arm spectrometer OK
• beauty production predominantlyat low polar angle
• two b-hadrons close in
15 mrad < < 300 mrad
4.9 > > 1.9
bb acceptance similar to large central detector
O. Schneider, Beauty 99 12
Detector layout
open geometry easy access to all components
View in bending plane (horizontal)as proposed in 1998:
O. Schneider, Beauty 99 13
Layout in LHC cavern
• overall size of LHCb determined by existing experimental hall
• beam crossing point displaced by ~ 11 m (LHCb operates in collider mode)
Side view at interaction point 8:
O. Schneider, Beauty 99 14
Si detectors single-sided 150 μm thick r- and -strips active radius 1–6 cm analogue readout
Si detectors single-sided 150 μm thick r- and -strips active radius 1–6 cm analogue readout
Vertex detector
17 silicon stations (disks) installed in vacuum pipe
retractableby 3 cmduring
injection
(details from C. Parkes tomorrow)
towards spectrometer
40 μm resolution on interaction point
(along beam axis)
O. Schneider, Beauty 99 15
RICH detectors(details from A. Go on Thursday)
Pattern recognition on photo-detector planesPattern recognition on photo-detector planes
CF4 ringssmallC4F10
rings
largeaerogelrings
Aerogel C4F10 CF4threshold .6 /GeV c .6 /GeV c . /GeV c
K threshold . /GeV c 9. /GeV c .6 /GeV c
O. Schneider, Beauty 99 16
K/ separation
K– separation > 3 over full momentum range
1<p< 150 GeV/c
K– separation > 3 over full momentum range
1<p< 150 GeV/c
highest momentum pion from Bs Ds
highest momentum pion from Bd
kaon from b c s(tagging kaon)
O. Schneider, Beauty 99 17
Particle identification
… without using RICH information
… without using RICH information
… with RICH fast parametrization
… with RICH fast parametrization
.. with RICHfull simulation andpattern recognition
.. with RICHfull simulation andpattern recognition
84% efficiency96% purity
82% efficiency89% purity
Two-body background:Bs KK (BR=1.5 105)Bs K (BR=0.7 105) Bd K(BR=1.5 105)
Signal:Bd (BR=0.7 105)
mass in GeV/c2
Example: Bd analysis
O. Schneider, Beauty 99 18
Other systems
warm dipole magnet– 4 Tm bending power
inner tracking (40 cm x 60 cm)
– Micro Strip Gas Chambers +Gaseous Electron Multipliers (MSGC+GEM), or Micro Cathode Strip Chambers (MCSC)
– fall-back solution:Si
outer tracking– drift chambers with straw-tube geometry
Main trackerMain tracker
CalorimetersCalorimeters
pre-shower– single layer Pb + scintillators
ECAL (details from A. Jacholkowska tomorrow)
– shashlik type, 25 X0
HCAL– Fe + scintillating tiles, 5.6
Muon chambersMuon chambers
p /p =.% <p < GeV / c
mB→ ( ) =MeV /c
mDs → KK( ) = MeV/ c
– Resistive Plate Chambers (RPC) + Cathode Pad Chambers (CPC) for high rate regions
– 22 for calorimeters and muon system
O. Schneider, Beauty 99 19
Running luminosity
Aiming for single pp interactionsper bunch crossing
– radiation damage– detector occupancy– pattern recognition
LHCb chosen running luminosity
2 x 1032 cm2 s1
LHCb chosen running luminosity
2 x 1032 cm2 s1
Tune luminosity bydefocusing beams
Constant luminositythroughout LHCb’s
lifetime
5.61011 bb pairs per yearin single pp interactions
assuming inel ≈8 mb andb b ≈μb
30%
O. Schneider, Beauty 99 20
Level-0 trigger
40 MHzInput rate
1 MHzOutput rate
4.0 μs
Latency
Pile-up veto – 2 dedicated Si disks to reject multiple pp
interactions (i.e. primary vertexes)
– size of luminous region: z ~ 5 cm
pT or ET single track triggers– muon muon chambers ~ 20 %– electron ECAL ~ 10%– hadron ECAL+HCAL ~ 60%– photon ECAL– ...
O. Schneider, Beauty 99 21
Level-1 trigger
1 MHzInput rate
40 kHzOutput rate
512–2048 μs
Latency
(details from C. Parkes tomorrow)
Topological identification of secondary vertexes
– find tracks in silicon (only)– reconstruct primary vertex– form secondary vertexes with
large impact parameter tracks
O. Schneider, Beauty 99 22
Higher level triggers
• software only, full event buffer
• farms of commercial processors
Level-2: reconstruct large impact parameter tracks in Si and first tracking chambers, and use measured momenta to refine secondary vertex requirement
Level-3: reconstruct specific b-hadron decay modes (loose cuts)using all information, incl. RICH
10 ms
Latency
40 kHzInput rate
5 kHzOutput rate
5 kHzInput rateof which
25% b-events
200 HzOutput rate
written to tape(20 MBytes/s)
200 ms
Latency
O. Schneider, Beauty 99 23
Trigger stability
• trigger is flexible, robust, andwell balanced between levels
• operating point can be adjusted to running conditions without significant loss in physics
point maximizingoverall CP sensitivity
Example: Adjustment of L0 thresholdswith fixed total (μ+e+h) retention of 9%
Example: Adjustment of L0 thresholdswith fixed total (μ+e+h) retention of 9%
CP reach withBd
relative to its maximum
O. Schneider, Beauty 99 24
Trigger efficiencies
in %, for useful events, reconstructed and correctly tagged offline
L0 L1 L2 Totalμe h all
BdJ/(ee)KS + tag 17 63 17 72 42 81 24
BdJ/(μμ)KS + tag 87 6 16 88 50 81 36
BsDsK + tag 15 9 45 54 56 92 28
BdDK831
99
Bd + tag 14 8 70 76 48 83 30
“High pT” track firing L0 trigger can be: – track from B decay of interest
– track from other b-hadron useful for tagging
Tags considered (so far): – muon or electron from other b-hadron
b lepton– charged kaon from other b-hadron
b c s
Overall tag efficiency = 40% Overall mistag rate = 30%
Tags considered (so far): – muon or electron from other b-hadron
b lepton– charged kaon from other b-hadron
b c s
Overall tag efficiency = 40% Overall mistag rate = 30%
importance of hadron trigger
efficiency dominatedby kaon tag
importance of hadron trigger
O. Schneider, Beauty 99 25
DAQ architecture
Level-0 buffer: on-detector electronicsall data digitized after Level-0 yes
Level-1 buffer: off-detector electronicszero-suppressed data transferred to DAQ after Level-1 yes
event size: 100 kB
Read-out Network (RN)
RU RU
Control &
Monitoring
RU
2-4 GB/s
4 GB/s
20 MB/s
Variable latencyL2 ~10 ms
L3 ~200 msL
AN
Read-out units (RU)
Timing&
FastControl
Front-End Electronics
Si-VTX TRACK ECAL HCAL MUON RICH
LHCb detector
L0
L1
Level 0Trigger
Level 1Trigger
40 MHz
1 MHz
40 kHz
Fixed latency 4.0 μs
Variable latency 512-2048 μs
Datarates
40 TB/s
1 TB/s
Front-End Multiplexers (FEM)1 MHz
Front End Links
Trigger Level 2 & 3Event Filter
SFC SFC
CPU
CPU
CPU
CPU
Sub-Farm Controllers (SFC)
Storage
3 GB/s
O. Schneider, Beauty 99 26
Schedule
1998
1999
2000
2001
2002
2003
2004
2005
Inner Tracker
Vertex Detector
RICH, Calorimeters
Muon System
L0 & L1 Trigger, DAQ
Magnet
Computing
Outer Tracker
Technical Proposal
LHCb approved
LHC and LHCb readyfor many years of B physicsat “nominal LHCb luminosity”
TechnicalDesignReports
Magnet installation
Detector and DAQ installation
O. Schneider, Beauty 99 27
Bd D*-+, D*+-
• need large stat. (CP asymmetry very small)• efficient hadron trigger essential
Extraction of from 4 time-dependent decay rates, use from J/KS
to get
– reconstruct D* inclusively (using slow pion) ~ 270 k events / year with S/B ~ 7– add D*a1 channels ~ 320 k events / year
in degrees
in
deg
rees
1 year
5 years ~ 4o
• no strong phase difference assumed• no uncertainty on ratio of BRs assumed
O. Schneider, Beauty 99 28
Bd D0K*0
• visible BR’s 10–8 –10–7
• hadron trigger and K/ separation essential
K tags flavourof decaying Bd
→ K+ − → K− +
→ K+K−, + −
Extraction of from the measurements of 6 time-integrated rates
m 13 MeV/c2
~ 400 signal
events total
S/B ~ 1
~ 10o
in one year
only Bd → DK *
signal events
O. Schneider, Beauty 99 29
Bs oscillations
• good proper timeresolution t essential
t ~ 43 fs
Need to resolve ms oscillations to measure time-dependent CP asymmetry in Bs decays
damped like
exp −
ms t( )⎡
⎣⎤⎦
Bs Ds :
~ 34500 rec. and tagged events/year
> 5 measurement of ms up to 48 ps1 (xs = 75)
O. Schneider, Beauty 99 30
• counter part of Bd J/ KS
• CP asymmetry allows to extract the phase of Bs mixing, i.e. angle
Bs J/
• decay into spin-1 particles:J/ can be CP-odd or CP-even(depending on angular orbital momentum)
additional dilution on CP asymmetry
• need angular analysis to separate contributions
• good proper time resolution needed• good proper time resolution needed
can also be done in ATLAS/CMS with similar sensitivity
~ 0.01
in one year
depends ms and r=A(CP-odd)/A(CP-even)(will be extracted as well)
O. Schneider, Beauty 99 31
Bs Ds-K+, Ds
+K-
• hadron trigger• proper time resolution• mass resolution• K/ separation (RICH)
• hadron trigger• proper time resolution• mass resolution• K/ separation (RICH)
kill Bs Ds background
Essential features:
Extraction of from 4 time-dependent
decay rates, use from J/ to get
~ 2.5 k events / year with S/B > 10
~ 6–13o
in one yeardepends on , ms,and strong phase(will be extracted as well)
O. Schneider, Beauty 99 32
Conclusion
LHC offers unique opportunity to probe CKM sector in depth
To go beyond what other experiments can do, LHCb will rely on– efficient, robust, and
flexible triggering scheme
– high performanceparticle identification
– excellent mass and proper time resolutions
LHCb will operate at its full potential from the first day of LHC running and for many years
LHCb can study many different B decay modes and, with high precision and efficiency, including fully hadronic channels
Ability of measuring CKM elements accurately implies good sensitivity to physics beyond the Standard Model
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