status of the lhcb experiment
DESCRIPTION
Status of the LHCb Experiment. Introduction & physics motivations Status of the detector construction Topics on physics potentials Conclusions. 高原宁 清华大学高能物理研究中心. 高能物理学会第七界学术年会 2006 年 10 月 29 日 桂林. LHCb is a dedicated B physics experiment at the LHC. P T of B-hadron. 100 μ b. - PowerPoint PPT PresentationTRANSCRIPT
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Status of the LHCb Experiment
高原宁
清华大学高能物理研究中心
• Introduction & physics motivations
• Status of the detector construction
• Topics on physics potentials
• Conclusions
高能物理学会第七界学术年会 2006 年 10 月 29 日 桂林
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LHCb is a dedicated B physics experiment at the LHC
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123212
bb
scm102@year /bb 10~
500~)14TeV(L
b
Forward spectrometer (running in pp collider mode)
Great potential for B physics!
Pythia
100μb
230μb
η of B-hadron
PT o
f B
-ha
dro
n
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Physics motivations
• The Standard model CP violation is described by the single complex phase in the CKM matrix, two unitarity triangles relevant to B physics at LHCb stat.
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Current SM fit of the Unitarity Triangles (including CDF result on ms)
= 94.6° ± 4.6° = 23.9° ± 1.0° = 61.3° ± 4.5°s= 2.1° ± 0.2°
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— high statistics Bd and Bs samples are essential— robust and efficient trigger, even for non-leptonic decays— good decay vertex resolution; good tracking; good particle identification
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• Many final states need to be reconstructed …
HIGH STATISTICS
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News from the experiment
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r- and measuring sensors rather than x,y fast and easy impact parameters for use in the trigger
VErtex LOcator “VELO”
21 stations
(pile-up vetodetector)
RF fo
il
beam
-spo
t z=5.
3cm-measuring sensor r-measuring sensor
-sensor:•radial strips (inner and outer)
•2048 strips•stereo angle(-20, +10)
•37–98 µm pitchr-sensor:•concentric strips
•2048 strips•4 sectors (45)•40-103 m pitchharsh radiation environment:
n-n sensors: keep good resolution if undepleted sensor cooling to -5°C with CO2 cooling system
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•good impact parameters detectors as close as 8mm to LHC beam
sensors placed in secondary vacuum
(10-9 mbar) separated from beam-
vacuum just by an 300m Al “RF-foil”•move sensors out during filling (3cm) •re-positioning accuracy: <10m
Vertex Locator Mechanics
RF-foils
vacuum vessel installed and surveyed (0.2mm accuracy)
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VELO Modules Production and Commissioning Test
real life detector modules
real “LHCb visualisation tool”
Testbeam: Alignment and Commissioning challenge using (almost) final HARD and LHCb SOFTware
successfully operated:
•important experience for commissioning online/offline software
•lots of test-beam data to be analysed now
9 out of 42 final detector modules are ready awaiting “burn-in”
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Expected VELO Performance
IP= 14m + 35 m/pT core
z = 44 m
corex = y = 8 m
impact parameter
use all tracks that include VELO: bb vertex resolution:_
average B flightpath = ~1cm !!
average:40mdominated by material before 1st measurement
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Other Tracking Detectors
TT-stationsilicon strips:
•PT info for the trigger
Outer Tracker:straw tubes
Inner Tracker:silicon strips•1.3% of the station surface
•20% of accepted tracks
magnet:
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TT-Station •4 layers: (2 with ±5º stereo angle)
•silicon strips: 143k channels, 7.9m2
•up to 39cm readout strips
•inner sectors connected via Kapton interconnect cables
•operation at ~5°C, liquid C6F14
cooling
~ 60% of modules finished
lower hybrid upper hybrid
Station assembly for testing in the lab
Good quality modules with low leakage currents
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Inner Tracker •silicon strips: 129k channels, 4.3m2
•336 modules
•11 and 22cm long modules/strips
•4 individual boxes per station
•4 layers per station:(2 stereo layers)
•operation at ~5°C, liquid C6F14 cooling
~ 60% of modules produced and tested
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Inner Tracker Installation
First Inner Tracker box has been assembled and partially tested
•support frames have been brought to the pit
•will be cabled soon
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Outer Tracker
pitch 5.25 mm
5mm cells Tracke-e-
e-
Straw tube tracker:
•ArC02 drift gas
•resolution: 200m
•4 layers / station
•2 stereo layers ±5º
Module production finished December 2005 !
HV > 1520 V
–ε 98%
–σ 200 µm
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Outer Tracker Installation
Support bridge… … installed …with modules
•1/4 of the stations are already equipped with modules
•now: testing, cabling, survey
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• selection of specific B-decay channels for CP measurements
• without particle ID, the bkg-dilutes/overwhelms the signal
RICH – Particle ID
Bs DsBs Ds
K
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2 RICH Detectors with 3 Cherenkov Radiators
RICH1: • 5cm silica aerogel (2-10GeV/c)
• 85cm C4F10 gas (<50GeV/c)
• spherical (CF) and planar (glass) mirrors
RICH2:
•170cm CF4 gas (<100GeV/c)
•spherical and planar glass mirrors
before and behind the magnet
c(
mra
d)
Expected photons detected• Aerogel 7• C4F10 30• CF4 23
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RICH – Photon DetectorHybrid Photon Detectors (HPDs):•photo tubes with silicon pixel chip
•2.5x2.5mm2 resolution for single photons
•low noise excellent single photon detection efficiency (200nm–600nm)
•85% detection efficiency (after photon conversion ~25%)
about 50% of HPDs are produced and tested
only 3% failures
number of pixel hits/event
datasimulation
10GeV pions, 1.1m N2
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RICH Installation
RICH2 cabling ongoing
RICH1 magnetic shield, gas enclosure and seal to VELO
RICH2: installed end 2005
56 spherical mirrors aligned to σθ~ 50 μrad
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Calorimeter System SPD/PS/ECAL/HCAL
they all use similar cost efficient technology: scintillating tiles in between lead/steel absorbers read out via wavelength shifting fibres
SPD: scintillating pads/tiles distinguish e± and PS: PreShower after 2.5cm of lead identifies electromagnetic
particlesECAL: shashlik type measure energy of electromagnetic
shower HCAL: iron interleaved with scintillating tiles energy of
hadrons
SPD-scintillating pad
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ECAL/HCAL Performance
E
E
E (0.83 0.02)%
((145 13) MeV)/E
(9.40.2)%
Ebeam GeV
E
E
Ebeam GeV
ECAL HCAL
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Calorimeter Installation
ECAL in place since June 2005
•Activity now focuses on cabling / commissioning using calibration LEDs
HCAL in place since Sept. 2005SPD/PS modules have been installed this summer
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Muon
Multi-Wire-Proportional-Chambers (MWPC) & GEMs (at center at 1st station) 4ns time resolution use in the trigger (20% PT resolution)
•muon filters are in place
•1380 MWP-Chambers production completed
•24 GEM production is ongoing
MWPCs Triple GEMsMWPC supportmuon filter
testbeam:anode efficiency
Eff
icie
ncy
[%
]
HV (kV)
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Two Trigger Levels:
e,
,K
• L0: hardware trigger
10MHz (interaction rate) 1MHz• calorimeter: (SPD multiplicity, # ET clusters)
• muon: (two high pT muons)
• pile-up system (indentify multiple interactions)
• L0 Decision Unit • Latency: 4s
• HLT: software trigger 1MHz2kHz• all sub-detectors readings• L0 confirmation • dedicated physics channel triggers depending on type of
L0 trigger• trigger on impact parameters
Many different custom electronics, all close to final production
Trigger commissioning will start 2007
L0 efficiencies: for channels withmuons: ~90%leptons: ~70%hadrons: ~50%
HLT efficiencies: .. no final numbers: still in transitions from former L1+HLT scheme (it was 50-80%)
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Online
EventFilterFarm
Readout Network
Front-end Electronics
TFCSystem
StorageSystem
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC~1800computer nodes
FE FE FE FE FEFE
SwitchSwitchSwitch Switch
VELO TT IT OT RICH CALO MUON L0
1 M
Hz
2 k
Hz
Full detector info available for HLT
LHCb common readout board (TELL1)
commercial network switch
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Magnet
•Magnet has long been installed
∫ Bdl : 4 Tm, warm coils4.2MWatt, 15 tons
fully operational
•magnetic field map to precision: 3x10-4 ,
•symmetry w.r.t. polarity: B/<B> ~ 3x10-4
stray B stray field between VELO and TT
fast PT info in Trigger
- calculationo measurement
VELO TT Magnet
z [cm]
By
[T]
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Beam Pipe
support wires
•25mrad Be section + Velo exit window
•1st and 2nd 10 mrad Be section
•stainless steel section
All beam-pipe pieces are at hand, 1st section installed and sealed to the VELO vessel
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Selected topics on physics potentials1. Measurement of the angle from Bs Ds
K+
• CP asymmetry arises from interference between two tree diagrams via Bs mixing: Bs Ds
+K and Bs DsK+
• Measures extract
is determined using Bs J/ decay, (sin 2) ~ 0.06 for one year)
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• Background from Bs Ds is suppressed using PID information from RICH1 & RICH2 remaining contamination ~ 10%
• Reconstruct using Ds KK
5400 signal events/year
• The strong phase difference of the two diagrams can be resolved by fit two time-dependent asymmetries: Phase of Ds
+Kasymmetry is (Phase ofDs
Kasymmetry is (can extract bothand(
() ~ 14 in one yearAsymmetries for
5 years of simulated data
Theoretically clean; insensitive to new physics
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Selected topics on physics potentials2. Measurement of the angle from B0 +– , Bs K+ K–
• bu processes with possible large b d(s) penguin contributions
• Measure time-dependent CP asymmetries for B0 and Bs
ACP(t) = Adir cos(m t) + Amix sin(m t)
extract four asymmetries
Adir(B0 ) = f1(d, , ) dei = ratio of penguin and tree Amix(B0 ) = f2(d, , ) amplitudes in B0 Adir(Bs ) = f3(d’, ’, ) d’ei’ = ratio of penguin and tree Amix(Bs ) = f4(d’, ’, ) amplitudes in Bs
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• Assume U-spin flavour symmetry (under interchange of d and s quarks)d = d’ and = ’ [R. Fleischer, PLB 459 (1999) 306]
• Taking and from other channels can solve for
blue bands from Bs KK
(95% CL)red bands from B
(95% CL)ellipses are 68% and 95% CL regions (input = 65)
d- plot
“fake” solution
Theoretical uncertainty from U-spin assumption (can be tested);Sensitive to new physics in the penguin loops
() ~ 5 in one year
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Selected topics on physics potentials3. Measurement of the angle from B0 D0K*0 , D0K*0 –
mixing DD00
• CP asymmetry arises from interference between two tree diagrams via D0-mixing
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systemf genstate oCP-even ei0000
CP
*0CP
0
*000
*000
DD :2/)DD(D
K)KK(DB (3)
K)πK(DB (2)
K)πK(DB (1)
• Measure six rates ( following 3 + CP-conjugates )
can be extracted from triangles [Gronau and Wyler, PLB 265 (1991) 172, Dunietz, PLB 270(1991) 75]
• 3.4K, 0.5K and 0.6K events respectively for one year data taking
() ~ 7-8 in one year
No theoretical uncertainties; sensitive to new physics in DCP
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Selected topics on physics potentials4. Charm physics at LHCb –
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Selected topics on physics potentials5. Bc Studies at Tsinghua –
BcGen (BcVGPY) is now LHCb standardPhysics + Manual > LHCb note
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Bc mass & lifetime
Refinements due to Trigger change > LHCb note soon
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Selected topics on physics potentialOutlook
• A possible scenario after the LHCb measurement of new physics?
• Many other interesting topics not covered by this talk
TDR, LHCb notes, …
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Conclusions
• LHCb is dedicated to the study of B physics, with a devoted trigger,excellent vertex and momentum resolution, and particle identification
• Construction of the experiment is progressing wellIt will be ready for first LHC collisions in 2007
(TELL1s from Tsinghua group are delivered to the experiment)
• LHCb will give unprecedented statistics for B decays, including access to the Bs meson, unavailable to the B factories
• Our Beauty is also Charming
• Physics preparations for Bc physics from Tsinghua group is well underway.