Status and Expected Performance of the LHCb Experiment

1
Status and Expected Performance of the LHCb
Experiment

• Pascal PERRET
• Laboratoire de Physique Corpusculaire
  Clermont-Ferrand
• Université Blaise Pascal CNRS/IN2P3
• France
• On behalf of the LHCb Collaboration

6th International Conference on Hyperons, Charm
and Beauty Hadrons Chicago 3rd July 2004
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OUTLINE

• Introduction Physics motivation
• LHC
• The LHCb experiment
• Status of the experiment
• Trigger
• Physics prospects
• Measurement of angle g
• Summary and conclusions

3
Physics motivation of LHCb

• SM predicts large CP violating asymmetries for
  B mesons, in many (often rare!) decays
• ?LHCb dedicated b physics precision experiment
  of 2nd generation to study CP violation and rare
  b-decays
• Much higher statistics
• Access to all b-hadron species
• Bd, Bu, Bs, Bc, ?b ,
• Overconstrain the unitarity triangles
  (consistency checks)
• Search for New Physics beyond the SM

Unitarity Triangles
Bd0 ? p p- Bd0 ? r p
BS0 ? DS p
a
Bd


VudVub
VtdVtb
g
b

VcdVcb
a
Bs

VtdVud

VtbVub
bc
New particles may show up in loop diagrams,
overconstrain will allow to disentangle SM
components from the new-physics ones
g-c

VtsVus
c
b
b
t
BS0 ? J/y f
NP?
High statistics is mandatory
d
d
t
4
Advantage of LHC

• LHC startup in spring 2007
• pp collisions at vs 14 TeV, f40 MHz, multiple
  pp interactions/bx
• Clear objective is to get to 1033 cm-2 s-1 during
  2007 operation
• Increase luminosity to 1034 cm-2 s-1 in the next
  few years
• ?total 100 mb, ?visible 65 mb, ?bb 500 µb,
  ?bb/ ?visible 0.8
• Forward production of bb, correlated
• LHCb
• Single arm spectrometer
• 12 mrad lt?lt 300 mrad (1,9lt?lt4,9)
• ltLgtLHCb 2 x1032 cm-2 s-1 (tunable
• controlled beam focus at LHCb IP)
• Efficient trigger and clean events

100mb
230mb
_
? 1012 bb events per year (107 s) with
nominal LHCb luminosity at LHC start-up
5
LHC
Geneva
CERN
6
LHC
Dipolesgt 300/1200 delivered
TI8 - MBIT
Short Straight Sections
Transfer line installed (2.6 km) 1st beam October
TI8 - MBIBV
QRL
7
LHCb Requirements

• Efficient trigger for many B decay topologies
• Leptonic final state ? Muon system, ECAL
  Preshower
• Hadronic final state?HCAL
• High pt-particles with large impact
  parameter?VELO,TT
• Efficient particle identification
• p/K separation (1ltplt100GeV) ? RICH
• Good decay time resolution
• ? VELO
• Good mass resolution
• ? Tracker and Magnet

HIGH STATISTICS
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LHCb detector
Construction well progressing
20 m
Forward spectrometer (running in pp collider mode)
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LHCb status Vertex Locator
Vertex AND Tracking detector

• 21 stations, retractable during injection
• sensitive area starts at only 8 mm from beam
  axis
• r/f sensors (single sided, 45º r-sectors)
• pitch ranges from 35 µm to 102 µm
• 200 µm thin silicon
• 180k readout channels

2 halves in a Roman-pot
sensors
1m
PV resolution 8µm (x,y) and 44µm (z) IP
precision 40µm
VELO mechanics
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LHCb status Tracking system

• Tracking system and dipole magnet to measure
  angles and momenta

• dp/p 0.37 ,
• mass resolution 14 MeV (for Bs ? DsK)
• tracking efficiency 94 (for pgt10 GeV)

?
Magnetic field regularly reversed to reduce
experimental systematics
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Magnet

• Warm Al conductor
• 4 Tm integrated field
• Weight 1500 tons
• 4.2 MW

• Assembly of yoke completed
• Moving magnet into final position (July 04)
• Field map measurements (2004-2005)

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Tracking chambers (TT, IT, OT)
320 µm thick sensors 410 µm thick sensors
Inner Tracker

• 3 stations with 4 layers each
• 198 µm readout pitch
• 130k readout ch.
• 1.3 of sensitive area ? 20 of all tracks

beam pipe
1.2x.4 m2
T1 to T3
OT
Outer Tracker
Trigger Tracker

• 3 stations with
• 4 double layers
• 5mm straw tubes
• 50k readout ch.

IT

• Level-1 trigger
• KS, low-p tracks

TT

• 22 layers
• 410 µm silicon
• 198 µm r/o pitch
• 144k readout ch.

6x5 m2
1.4x1.2 m2
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Tracking chambers (TT, IT, OT)
OT
Outer Tracker

• 3 stations with
• 4 double layers
• 5mm straw tubes
• 50k readout ch.

Production started
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RICH

• Two RICH detectors for charged hadron
  identification

Aerogel and C4F10
RICH-1 25-300 mrad
RICH-2 15-120 mrad
CF4
Bs ?KK-
p13
?
e(K?K)88 e(p?K)3
p84 e79
Provide gt 3 s pK separation for 3 lt p lt 80 GeV
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RICH
RICH2 super structure ready
Exit/entrance windows ready
80 mm
Photon detector Hybrid Photodiodes (1024 pixels-
LHCb development) ordered RICH 1 168 HPD RICH2
262 HPD
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Calorimeter SPD,PS,ECAL,HCAL

• Identification electrons, hadrons and neutrals
  (?,p0) Readout every 25 ns (L0 trigger)

• SPD,PS (2.5X0), ECAL(25X0) 5962 channels
  (Pb/scintillator)
• HCAL(5.6?) 1468 channels (Iron/scintillator)

e
2 resolved clusters
h
?sm(p0???) 10 MeV/c2
?
Conversion
?(2 merged clusters 15 MeV/c2)

• ECAL ?E/E 8.3/?E ? 1.5
• HCAL ?E/E 75/?E ? 10

?(e?e) 95, ?(??e) 0.7
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SPD - PS
200 64APMT

• PS/SPD modules 25 completed
• Assembly SuperModules start September

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ECAL - HCAL

• HCAL modules 60 completed Installation start
  December
• ECAL modules 100 completed Installation start
  November (shashlyk type)

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Muon System
Muon identification, also used in first level of
trigger

• 1380 MWPC chambers
• Chambers in M2-M5 4 layers
• in M1 2 layers
• x and y projectivity
• to Interaction Point
• 435 m2
• 26 k readout channels
• hadron absorber thickness of 20 ?

m
?
µ id. efficiency 94 for pion misidentification
rate lt1
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Muon System
Foam Panel Production
Automated wiring machine

• Production started
• 5 sites
• 5 ready

Final chamber assembly
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Trigger
µ pT gt1.1 GeV e ET gt2.8 GeV g ET gt2.6 GeV h
ET gt3.6 GeV

• sbb 500 mb, lt 1 of inelastic cross-section
• Use multi-level trigger to select interesting
  events ? high pT electrons, muons or hadrons
  ? vertex structure and pT of tracks ? full
  reconstruction

HCAL trigger dominates
200 Hz to tape
? ? ?
L0 L1 HLT
MUON trigger dominates
3060efficiency
ECAL trigger dominates
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Trigger
40 MHz
L0 synchronized hardware trigger
Calorimeter Muon Pile-up
Level-0 pT of m, e, h, g
4 µs
1 MHz
Vertex Trigger Tracker Level-0 objects
Level-1 Impact parameter pT 20
1 ms 1 800 CPU
asynchronous SW trigger
40 kHz
HLT Final state Reconstruction
Full detector Information
commercial hardware flexible (L1?HLT) scalable ?
easy upgrade
200 Hz output
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Simulation

• MC Pythia 6.2 tuned on CDF and UA5 data, QQ,
  GEANT3
• Multiple pp interactions and spill-over effects
  included

• Complete description of material from TDRs
• Individual detector responses tuned on test beam
  results

• Complete pattern recognition in reconstruction
• without using MC true information

VELO
Magnet
TT
RICH1

• 2003 67M events produced
• 10M inclusive bb events (4 mn of data taking!)
• Used for expected physics performance quoted here
• 2004 180M events simulation and analysis in a
  distributed way (Grid)
• Started in May (already 50M events produced),
  3000 jobs/day
• Pythia, EvtGen, GEANT4

T1 T2 T3
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Efficiencies, event yields and Bbb/S ratios
Nominal year 1012 bb pairs produced (107 s at
L2?1032 cm?2s?1 with ?bb500 ?b) Yields include
factor 2 from CP-conjugated decays Branching
ratios from PDG or SM predictions
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b from B0 ? J/? Ks

• The gold plated channel at B-factories
• Precision measurement of this parameter is very
  important

sin 2b
?37 ?tag45 ?eff3 B/S0.8
0 in SM

• LHC(b) will bring a lot of statistics to this
  channel, which can be used to look into higher
  order effects, and fit Adir

In one year with 240k events s (sin 2b )
0.02
Background-subtracted B??J/?(??)KS CP asymmetry
after one year
Comparing with other channels may indicate NP in
penguin diagrams
Similar sensitivity ATLAS/CMS
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?ms from Bs?Ds-(KK?)?
?30 ?tag55 ?eff9 B/S0.3

• If NP is present

• Fully reconstructed decay
• Excellent momentum resolution, decay length
  resolution 200 µm
• Proper time resolution 40fs

Expected unmixed Bs ?Ds??? sample in one year of
data taking (fast MC)
In one year with 80k events can observe gt5?
oscillation signal if ?ms lt 68 ps?1 well beyond
SM prediction (14.8-26 ps?1)
Once a BsBs oscillation signal is seen, the
frequency is precisely determined ?(?ms ) 0.01
ps-1
ATLAS/CMS ?ms lt 30 ps?1
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c from Bs ? J/y f

• Bs counterpart of the golden mode B0 ? J/y KS
• measures the phase of Bs mixing

• Is not CP eigenstate (VV decay). Angular analysis
  needed to separate CP-even and CP-odd
  contributions (from transversity angle
  distribution) needs fit to angular distributions
  of decay final states as a function of
  proper-time (good proper-time resolution is
  essential)

• In SM expected asymmetry ? sin 2c very small
  0.04? sensitive probe for new physics
• Reconstruct J/y ? mm- or ee-, f ? KK-

In one year with 120k events s (sin 2c)
0.06 , s( DGs/ Gs) 0.02
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? from B?????? and Bs?K?K?

• In both decays large b ?d(s) penguin
  contributions to b ?u
• Measure time-dependent CP asymmetries in B??????
  and Bs?K?K? decays
• ACP(t)Adir cos(?m t) Amix sin(?m t)
• Exploit U-spin flavour symmetry for P/T ratio
  Fleischer
• Use measure of c from B0 ? J/y f and b from B0 ?
  J/? Ks
• 4 measurements (CP asymmetries) and 3 unknowns
  (?, d and ?) ? can solve for ?
• Good p/K identification

37 k Bbb/S0.3
26 k Bbb/Slt0.7
B??????
Bs?K?K?
In one year s (g) 4-6 deg
U-spin symmetry assumed sensitive to new physics
in penguins
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? from B?? D?K? and B?? D?K?

• B?? DCPK? interference between 2 tree diagrams
• Application of Gronau-Wyler method Dunietz

v2 A2
v2 A2
A3
2?
A3
???
A1 A1

• Measure 6 decay rates (following three
  CP-conjugates)

• No proper time measurement or tagging required
• assumes DCP (D? D? )/?2

In one year s (g) 7-8 deg
?65o, ?0
sensitive to new phase in DCP state
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? from Bs ? Ds? K

• Interference between 2 tree diagrams (again) via
  Bs mixing
• Measure ?-2c from time-dependent rates
  Bs?Ds? K? (b ? c) and Bs?Ds?K? (b ? u) (
  CP conjugates)
• Use 2c from Bs ? J/y f
• Mistag extracted from Bs ?Ds??? sample

5.4 k B/Slt1
Bs ? Ds p is background for Ds KBranching ratio
12 ? higher
In one year s (g) 14-15 deg
The two Bs-Bs asymmetries after 5 years of data
No theoretical uncertainty insensitive to new
physics in B mixing
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Interest in over-constraining the CKM UT
New physics in angle ? measurement ?
1. Bs ? DsK
2. B ? ??, Bs ? KK
3. B ? DK
? not affected by new physics
? affected by possible new physics in penguin
? affected by possible new physics in D-D mixing
Extract the contribution of new physics to the
oscillations and penguins
Determine the CKM parameters A,?,? independent of
new physics
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Other physics at LHCb

• New physics in b ? s penguin processes
• B0 ? Kg, B0 ? f KS ,Bs ? ff, KK, fg,
• Bs0 ? J/y h, Bs0 ? J/y h, ,
• Direct CP violation B?u ? K? r(v), ...
• Rare decays
• Bs ? mm- ,B0d ? K0mm- (cf talk from S. Viret)
• Bc physics
• Lifetime, mass, branching fractions
• g measurements from Bc ? D Ds difficult!
• b baryons

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Conclusion

• LHCb is dedicated to the study of b physics
• a devoted trigger
• excellent vertex and momentum resolution
• excellent particle identification
• Access to all b-hadron species Bu, Bd, Bs, Bc ,
  Lb
• LHCb detector will be ready for data taking in
  2007 at LHC start-up
• Construction of the experiment is progressing
  well
• installation of detectors starts this year
• Already in year one, LHCb will have competitive
  measurements on b, g, c, Dms and other parameters

LHCb offers an excellent opportunity to spot New
Physics signals beyond the Standard Model very
soon at LHC
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Are Penguins New Physics Guards?
NP
NP