First Results of ATLAS at the LHC -- The rediscovery of the Standard Model--
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Transcript of First Results of ATLAS at the LHC -- The rediscovery of the Standard Model--
Marcel Vreeswijk (Nikhef/UvA-IoP)
First Results of ATLAS at the LHC
--The rediscovery of the Standard Model--
Contents:• Intro: The Standard Model
Elementairy particles.
• Status LHC and ATLAS
• Physics results 2010
The Standard Model
So, what have we been doing in 2010?
Measuring ‘backgrounds’!
Higgs mechanisme to generate mass!Higgs boson mass > 114 GeV
Ultimate goal:
detect the Higgs particle
(not yet;need more data!)
Marcel Vreeswijk (Nikhef/UvA-IoP)
CERN site
LHCP+P at 7TeV27km60 ton He at 2K 4 big experiments this talk: ATLAS
First year of running. (7TeV)high quality data 2010: ~35pb-1
In 2011: run at 7TeV or higher? >>10-fold luminosity?
The LUMINOSITY represents the delivered number of proton collisions
In addition: Pb+Pb collisions (not in this talk)
atlas
Large Hadron Collider (LHC)
Marcel Vreeswijk (Nikhef/UvA-IoP)
LHC physics reach
• Production Cross-section of top quarks and W, Z bosons are measurable with 2010 data!
• Top, W,Z signals are important:1.Standard candles for calibration2.Background to new physics & Higgs
searches
1000
1
1 M
5 T
# events in 2010
HiggsTop quarksW,Z bosons
Proton-Proton
In r
each
in 2
010
Higgs W, Z
W, ZPromising final states:H W+W- 2 leptons + EtMissH ZZ 4 leptonsAlso H 2 photons
7TeV in 2010
jargon: lepton=electron or muon
N = L . N = # collisionsL = Luminosity = cross-section
Marcel Vreeswijk (Nikhef/UvA-IoP)
Inner detector(charged particle tracks)
Calorimeter(energy all particles, but muons) Muon ‘Chambers’
ATLAS
p
Data rec. 93.5%#working channels >99%
Marcel Vreeswijk (Nikhef/UvA-IoP)
Performance Inner Tracker
1 m
Inner Tracker
Ks
Kaon discovery: 1947
Pixel detector (80M channels)Silicon strips (6M channels)TRT (350k channels)Operational for 97.5%
Momentum measurement in magnetic field of 2TResolution σ(pT)/pT = 0.05%pT 1% ⊕
Marcel Vreeswijk (Nikhef/UvA-IoP)
Performance Calorimeterelectromagnetic: Liquid Argon sampling calorimeter.Resolution ~10%/sqrt(E)Granularity: eta x phi=0.025 x 0.025
since 1950
Rediscovery of the 0 8m
Marcel Vreeswijk (Nikhef/UvA-IoP)
Di-jet physics
Marcel Vreeswijk (Nikhef/UvA-IoP)
Di-jet invariant mass
• New energy domain.
• Highest Pt jet: 1.12 TeV
• Highest mass: 3.7 TeV
• Searches for new physics ongoing
ATLAS published 3 papers on jet measurements
p p
jet
jet
Marcel Vreeswijk (Nikhef/UvA-IoP)
Performance Muons
Physics signals show up!
Muon system:1200 Muon chamber350k drift tubes(air core toroidal field 0.5T)
Designed for TeV muons (not yet)
Z boson ‘rediscovered’Originally: 1983 at CERNMass: 91.19 GeV
Marcel Vreeswijk (Nikhef/UvA-IoP)
Muon resonancesATLAS 2010
? mass
Pub
lishe
d20
10
Z cross-section in new energy domain=7TeV
1960
1963
1977
1974
1983
Marcel Vreeswijk (Nikhef/UvA-IoP)
MissingTransverse energy
W boson ‘rediscovered’Originally: 1983 at CERNMass: 80.4 GeV
Marcel Vreeswijk (Nikhef/UvA-IoP)
W boson production
W decays to muon + (unseen) neutrino. Missing transverse energy.
W
q
q’g
Transverse W mass:
Marcel Vreeswijk (Nikhef/UvA-IoP)
Top pair (ttbar) production• complicated events:1. Many jets with 2 b-jets (can
be ‘tagged’)2. Electron or Muon3. EtMiss Standard candle New physics may show up p pt
t ttbar has two measurable decays modes:single-leptondi-lepton(mode is set by W decay)
ttbarsingle-lepton
DatumBasic prper.Europ. Topds!Last heaviest known particleLast before new
Marcel Vreeswijk (Nikhef/UvA-IoP)
di-leptonic ttbar2 b-tagged jets
Marcel Vreeswijk (Nikhef/UvA-IoP)
ttbarMore info on poster by Ido & Hegoi N. from Nikhef
Van Tera naar 100evts selectieSpeld hooi
Marcel Vreeswijk (Nikhef/UvA-IoP)
ttbar: theory & experiment
Marcel Vreeswijk (Nikhef/UvA-IoP)
Higgs in 2011 ?
We have measured the ‘backgrounds’, now we are ready for the signal !
Conclusion
The LHC and the ATLAS detector have demonstrated to be ready for the Standard Model Higgs or new physics
See next talk by Paul de Jong!
Marcel Vreeswijk (Nikhef/UvA-IoP)
BACKUP
4222V
“We know everything about the
Higgs boson except its mass”
Λ (GeV)
Hig
gs m
ass (
GeV
)
Triviality
Vacuum stability
Limits on mh from theory
Limits on mh from exper.
Marcel Vreeswijk (Nikhef/UvA-IoP)
W boson cross section
Marcel Vreeswijk (Nikhef/UvA-IoP)
Photon production (QCD compton)• photons of hundreds of GeVs !
• (Xray 0.0001 GeV)
Marcel Vreeswijk (Nikhef/UvA-IoP)
Marcel Vreeswijk (Nikhef/UvA-IoP)
Marcel Vreeswijk (Nikhef/UvA-IoP)
The Standard Model
Ultimate goal: detect the Higgs particle (not yet…need more data!)
So, what have we been doing in 2010? Measuring ‘backgrounds’!
+ Higgs boson to generate mass!
Promising decay modesH 2 photonsH W+W- 2 leptons + EtMissH ZZ 4 leptonsand much more….
Marcel Vreeswijk (Nikhef/UvA-IoP)
The Standard Model
• Production Cross-section of top quarks and W, Z bosons are measurable with 2010 data!
• Top, W,Z signals are important:1. Standard candles for calibration2. Background to new physics & Higgs
searches
1000
1
1 M
5 T
# events in 2010
HiggsTop quarksW,Z bosons
Proton-Proton
In r
each
in 2
010
Note: a proton=many quarks+gluons
Higgs W, Z
W, ZPromising final states:H W+W- 2 leptons + EtMissH ZZ 4 leptonsAlso H 2 photons
7TeV in 2010
jargon: lepton=electron or muon
Marcel Vreeswijk (Nikhef/UvA-IoP)
CERN site
LHCP+P at 7TeV27km60 ton He at 2K 4 big experiments this talk: ATLAS
First year of running. (7TeV)high quality data 2010: ~35pb-1This year (2011): run at 7TeV or higher? >>10-fold luminosity?
The LUMINOSITY represents the delivered number of proton collisions
3.2T botsingen655k hi Pb=Pb
Marcel Vreeswijk (Nikhef/UvA-IoP)
Z boson production Do we understand Z production and its backgrounds? First measurement ever at 7 TeV.
Ook in e+e-DiagrammenLin schaal?
DatumZ massa2Gev wordt 90GeV