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

LHCb is a dedicated B physics experiment at the LHC

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

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.

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°

— 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

• Many final states need to be reconstructed …

HIGH STATISTICS

News from the experiment

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

•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)

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”

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

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:

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

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

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

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

Outer Tracker Installation

Support bridge… … installed …with modules

•1/4 of the stations are already equipped with modules

•now: testing, cabling, survey

• 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

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

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

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

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

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

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

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)

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%)

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

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]

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

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)

• 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

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

• 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

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

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

Selected topics on physics potentials4. Charm physics at LHCb –

Selected topics on physics potentials5. Bc Studies at Tsinghua –

BcGen (BcVGPY) is now LHCb standardPhysics + Manual > LHCb note

Bc mass & lifetime

Refinements due to Trigger change > LHCb note soon

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, …

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.