The ATLAS experiment The ATLAS Detector Physics at the LHC Luminosity determination Hasko Stenzel.

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


An Aerial View of Point-1


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


Central Solenoid

2T field with a stored energy of 38 MJ

Integrated design within the barrel LAr cryostat

Magnet System


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


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


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).


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


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


SCT

TRT Insertion of the SCT into barrel TRT

Three completed Pixel disks(one end-cap) with 6.6 M channels


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


Barrel

Endcap

Forward


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


‘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


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 online

follow online what happens at http://atlas.web.cern.ch/Atlas


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


Physics processes at the LHC

221

22

212

,1 ,,ˆ,, sijji

ji

xxxfxfdxxd

PDFs partonic cross section


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


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)


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!


Higgs production


SM Higgs cross section


Higgs Decays


Higgs-> γγ


Higgs-> ZZ -> 4l


Higgs-> WW -> 2l2ν


VBF H->ττ


Higgs discovery potential


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!


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


Luminosity from elastic scattering


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


Roman Pot location


The scintillating fibre tracker


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)


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


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*


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!


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


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


experimental systematic uncertainties

Currently being evaluated

beam divergence detector resolution acceptance alignment beam optics background

ΔL/L ≈ 2.8-3.2 %


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

The ATLAS experiment The ATLAS Detector Physics at the LHC Luminosity determination Hasko Stenzel.

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Transcript of The ATLAS experiment The ATLAS Detector Physics at the LHC Luminosity determination Hasko Stenzel.