The ATLAS experiment The ATLAS Detector Physics at the LHC Luminosity determination
description
Transcript of The ATLAS experiment The ATLAS Detector Physics at the LHC Luminosity determination
The ATLAS experiment
• The ATLAS Detector• Physics at the LHC• Luminosity determination
Hasko Stenzel
ATLAS H.Stenzel, January 2007 2
• pp s = 14 TeV Ldesign = 1034 cm-2 s-1 (after 2009) Linitial few x 1033 cm-2 s-1 (until 2009)
• Heavy ions (e.g. Pb-Pb at s ~ 1000 TeV)
TOTEM
ALICE : ion-ion,p-ion
ALICE : ion-ion,p-ion
ATLAS and CMS :general purpose
ATLAS and CMS :general purpose
27 km LEP ring 1232 superconducting dipoles B=8.3 T
TOTEM (integrated with CMS):pp, cross-section, diffractive physics
TOTEM (integrated with CMS):pp, cross-section, diffractive physics
LHCb : pp, B-physics, CP-violationLHCb : pp, B-physics, CP-violation
The LHC
ATLAS H.Stenzel, January 2007 3
An Aerial View of Point-1
ATLAS H.Stenzel, January 2007 4
The ATLAS Detector
GeV
10%( , ) 0.3%
/E eE E
GeV
60mrad
/E
GeV
4 ns
/t E
GeV
50%( ) 3%
/E
E E
GeV
50%( jet) 2%
/E
E E
Calorimetry:
GeV(Inner Det) (0.03 / 1.2)%TT
pp
Tracking:
GeV(IDet+ ) (0.009 / 1.4)%TT
pp
Length : ~45 m Radius : ~12 m Weight : ~ 7000 tonsElectronic channels : ~ 108
~ 3000 km of cables
• Tracking (||<2.5, B=2T) : -- Si pixels and strips -- Transition Radiation Detector (e/ separation)• Calorimetry (||<5) : -- EM : Pb-LAr with Accordion shape -- HAD: Fe/scintillator (central), Cu/W-LAr (fwd)• Muon Spectrometer (||<2.7) : air-core toroids with muon chambers
ATLAS H.Stenzel, January 2007 5
Central Solenoid
2T field with a stored energy of 38 MJ
Integrated design within the barrel LAr cryostat
Magnet System
ATLAS H.Stenzel, January 2007 6
Magnet System
Toroid
Barrel Toroid parameters25.3 m length 20.1 m outer diameter 8 coils1.08 GJ stored energy370 tons cold mass830 tons weight4 T on superconductor56 km Al/NbTi/Cu conductor20.5 kA nominal current4.7 K working point
End-Cap Toroid parameters5.0 m axial length 10.7 m outer diameter 2x8 coils2x0.25 GJ stored energy2x160 tons cold mass2x240 tons weight4 T on superconductor2x13 km Al/NbTi/Cu conductor20.5 kA nominal current4.7 K working point
ATLAS H.Stenzel, January 2007 7
Inner Detector
The Inner Detector (ID) is organized Into four
sub-systems:
Pixels (0.8 108 channels)
Silicon Tracker (SCT)(6 106 channels)
Transition Radiation Tracker (TRT)(4 105 channels)
Common ID items
ATLAS H.Stenzel, January 2007 8
PIXELS
The system consists of three barrels at average radii of ~ 5 cm, 9 cm, and 12 cm (1456 modules) and three disks on each side, between radii of 9 and 15 cm (288 modules).
ATLAS H.Stenzel, January 2007 9
SILICON TRACKER (SCT)
The SCT system is designed to provide eight precision measurements per track
It is constructed using 4088 silicon micro-strip modules arranged as 4 barrels in the central region and 2 x 9 annular wheels in the forward region
The SCT covers a pseudo-rapidity-range < 2.5
ATLAS H.Stenzel, January 2007 10
TRANSITION RADIATION TRACKER (TRT)
Straw tracker50,000 in barrel320,000 in endcaps
Gas MixtureXe,CO2,O2
(70%,27%,3%)Barrel radial coverage
56cm -107 cm Endcap radial coverage
64cm – 103 cmDrift time measurements & Transition Radiation detectionAverage of 36 points on a track
ATLAS H.Stenzel, January 2007 11
SCT
TRT Insertion of the SCT into barrel TRT
Three completed Pixel disks(one end-cap) with 6.6 M channels
ATLAS H.Stenzel, January 2007 12
LAr and Tile Calorimeters
Tile barrel Tile extended barrel
LAr forward calorimeter (FCAL)
LAr hadronic end-cap (HEC)
LAr EM end-cap (EMEC)
LAr EM barrel
ATLAS H.Stenzel, January 2007 13
Barrel
Endcap
Forward
ATLAS H.Stenzel, January 2007 14
Muon Spectrometer Instrumentation
Precision chambers:- MDTs in the barrel and end-caps- CSCs at large rapidity for the innermost end-cap stationsTrigger chambers:- RPCs in the barrel- TGCs in the end-caps
The Muon Spectrometer is instrumented with precision chambers and fast trigger chambers
A crucial component to reach the required accuracy is the sophisticated alignment measurement and monitoring system
ATLAS H.Stenzel, January 2007 15
‘Big Wheel’ end-cap muon MDT sector assembled in Hall 180
‘Big Wheel’ end-cap muon TGC sector assembled in Hall 180
End-cap muon chambersector preparations
Altogether 72 TGC and 32 MDT ‘Big-Wheel’ sectors have to be assembled
ATLAS H.Stenzel, January 2007 16
The large-scale system test facility for alignment, mechanical, and many other systemaspects, with sample series chamber station in the SPS H8 beam
Shown in this picture is the end-cap set-up, it is preceded in the beam line by a barrel sector
ATLAS H.Stenzel, January 2007 17
ATLAS online
follow online what happens at http://atlas.web.cern.ch/Atlas
ATLAS H.Stenzel, January 2007 18
H ZZ 4
“Gold-plated” channel for Higgs discovery at LHC
Simulation of a H ee event in ATLAS
Signal expected in ATLASafter 1 year of LHC operation
Physics example
ATLAS H.Stenzel, January 2007 19
Physics processes at the LHC
221
22
212
,1 ,,ˆ,, sijji
ji
xxxfxfdxxd
PDFs partonic cross section
ATLAS H.Stenzel, January 2007 20
Physics with ATLAS
Search for the Standard Model Higgs boson over ~ 115 < mH < 1000 GeV
Search for physics beyond the SM (Supersymmetry, q/ compositeness, leptoquarks, W’/Z’, heavy q/, Extra-dimensions, mini-black holes,….) in the TeV-range
Precision measurements : -- W mass -- top mass, couplings and decay properties -- Higgs mass, couplings, spin (if Higgs found) -- B-physics (complementing LHCb): CP violation, rare decays, B0 oscillations -- QCD jet cross-section and s
-- W/Z cross sections (+jets)
Extensions of the physics program -- heavy ion running, phase transition to q/g plasma -- diffraction & forward physics
ATLAS H.Stenzel, January 2007 21
Physics of the first years
Expected event rates at production in ATLAS at L = 1033 cm-2 s-1
Process Events/s Events for 10 fb-1 Total statistics collected at previous machines by ‘07
W e 15 108 104 LEP / 107 Tevatron
Z ee 1.5 107 107 LEP
1 107 104 Tevatron
106 1012 – 1013 109 Belle/BaBar ?
gg~~
tt
bb
H m=130 GeV 0.02 105 ?
m= 1 TeV 0.001 104 ---
Black holes 0.0001 103 ---m > 3 TeV (MD=3 TeV, n=4)
ATLAS H.Stenzel, January 2007 22
Higgs Physics
Search for the Higgs Boson, study of the electroweak SU(2)xU(1) symmetry breaking
-- discovery of the Higgs boson & mass determination-- measurement of the Higgs couplings to verify the mass generation mechanism-- determination of the Higgs parameters (width, spin, parity, Charge (MSSM),...)
coupling to fermions ~ mf /v
coupling to Bosons ~ mv2
/vNeed to measure both H-> ff and H-> VV channels!
ATLAS H.Stenzel, January 2007 23
Higgs production
ATLAS H.Stenzel, January 2007 24
SM Higgs cross section
ATLAS H.Stenzel, January 2007 25
Higgs Decays
ATLAS H.Stenzel, January 2007 26
Higgs-> γγ
ATLAS H.Stenzel, January 2007 27
Higgs-> ZZ -> 4l
ATLAS H.Stenzel, January 2007 28
Higgs-> WW -> 2l2ν
ATLAS H.Stenzel, January 2007 29
VBF H->ττ
ATLAS H.Stenzel, January 2007 30
Higgs discovery potential
ATLAS H.Stenzel, January 2007 31
Higgs couplings
Relative precision on the measurement of HBR for various channels, as function of mH, at Ldt = 300 fb–1. The dominant uncertainty is from Luminosity: 10% (open symbols), 5% (solid symbols).
(ATLAS-TDR-15, May 1999)
Large uncertainty contribution from Luminosity!
ATLAS H.Stenzel, January 2007 32
Methods of Luminosity measurements
Absolute luminosity ● from the parameters of the LHC machine● rate of ppZ0/ W± l+ l- / lν
● rate of ppγγμ+ μ-
● Optical theorem: forward elastic+ total inelastic rate, extrapolation t0 (but limited |η| coverage in ATLAS)
● cross-check with ZDC in heavy ion runs● from elastic scattering in the Coulomb region● combinations of all above
Relative luminosity● LUCID Cerenkov monitor, large dynamic range, excellent linearity
ATLAS aims for 2-3% accuracy in L
ATLAS H.Stenzel, January 2007 33
Luminosity from elastic scattering
ATLAS H.Stenzel, January 2007 34
Roman Pots for ATLAS
RP
IP
240m 240m
RPRP RP
RP RP RP RP
PMT baseplate
optical connectors
scintillating fibre detectors glued on ceramic supports
10 U/V planesoverlap&trigger
Roman Pot
MAPMTsFE electronics
& shield
Roman Pot Unit
ATLAS H.Stenzel, January 2007 35
Roman Pot location
ATLAS H.Stenzel, January 2007 36
The scintillating fibre tracker
ATLAS H.Stenzel, January 2007 37
detector prototypes for testbeam 2006
10 x 2 x 16 resolution studies
2 x 2 x 64 construction studies
2 x 2 x 30 overlaps
Fabrication of prototypes at CERN with support from Lisbon (LIP) for fibre machining, aluminum coating, QC testbeam mechanicsand from Giessen for gluing of fibres optical connectors Plan to produce a full-scale prototype in 2007
(1/8 of the full set-up)
ATLAS H.Stenzel, January 2007 38
Simulation of the LHC set-up
elastic generatorPYTHIA6.4
with coulomb- and ρ-termSD+DD non-elastic
background, no DPE
beam propertiesat IP1
size of the beam spot σx,y
beam divergence σ’x,y
momentum dispersion
beam transportMadX
tracking IP1RP high β* optics V6.5
including apertures
ALFA simulationtrack reconstruction
t-spectrumluminosity determinationlater: GEANT4 simulation
ATLAS H.Stenzel, January 2007 39
Simulation of elastic scattering
2
,
2
,
2
2222*
yeffxeff
yx
L
y
L
xp
ppt
t reconstruction:
hit pattern for 10 M elastic events simulated with PYTHIA + MADX for the beam transport
2
sin
effL
special optics parallel-to-point focusing high β*
ATLAS H.Stenzel, January 2007 40
acceptance
Global acceptance = 67%at yd=1.5 mm, including losses in the LHC aperture.Require tracks 2(R)+2(L) RP’s.
distance of closest approach to the beam
radGeVTOT
EMa
t
Nf
Cf
5.324106
8
|||| :Region Coulomb
Detectors have to be operated as close as possible to the beam in order to reach the coulombregion!
-t=6·10-4 GeV2
decoupling of L and σTOT
only via EM amplitude!
ATLAS H.Stenzel, January 2007 41
t-resolution
The t-resolution is dominated by the divergence of the incoming beams.
σ’=0.23 µrad
ideal case
real world
2*231
ˆ pppt
ATLAS H.Stenzel, January 2007 42
L from a fit to the t-spectrum
2
222/
2
22
2
16
14
c
e
t
e
t
cL
FFLdt
dN
tBtot
tBtot
NC
input fit errorcorrelation
L 8.10 1026 8.151 1026 1.77 %
σtot 101.5 mb 101.14 mb 0.9% -99%
B 18 Gev-2 17.93 Gev-20.3%
57%
ρ 0.15 0.143 4.3% 89%
Simulating 10 M events,running 100 hrsfit range 0.00055-0.055
large stat.correlation between L and other parameters
ATLAS H.Stenzel, January 2007 43
experimental systematic uncertainties
Currently being evaluated
beam divergence detector resolution acceptance alignment beam optics background
ΔL/L ≈ 2.8-3.2 %
ATLAS H.Stenzel, January 2007 44
conclusion
● LHC start up in 2007
● ATLAS detector on track
● running at low luminosity 1033cm -2s-1 and in 2008
● switch to design luminosity 1034cm -2s-1 after 2009
● luminosity calibration from elastic scattering in 2009 ?
● LHC start up in 2007
● ATLAS detector on track
● running at low luminosity 1033cm -2s-1 and in 2008
● switch to design luminosity 1034cm -2s-1 after 2009
● luminosity calibration from elastic scattering in 2009 ?
GeV 900s
TeV 14s