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Elementary Particle Physics Experiment:
The ATLAS experiment at the LHC
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University of Massachusetts, Amherst
Graduate Research Orientation
1 Feb 2010
Feb 1, 2010
Experimental Particle Physics
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The UMass ATLAS Group
Faculty
– Ben Brau - LGRT 1032
– Carlo Dallapiccola - LGRT 1038
– Stephane Willocq - LGRT 1042
Postdoctoral Researchers
– Ed Moyse, Elisa Pueschel, Niels Van Eldik, Martin
Woudstra - CERN
Graduate Students
– Andrew Meade, Emily Thompson - CERN
– German Colon, Preema Pais, Tulin Verol - LGRT 1036
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Experimental Particle Physics
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What is Particle Physics About?
Experiments can address long standing puzzles / questions:
 What are the fundamental constituents of matter?
 What are the fundamental forces between elementary
particles?
 Can the forces of nature be unified? Including gravity?
 What is the origin of mass?
 What is the origin of the matter-antimatter asymmetry of the
Universe?
 What is dark matter?
 Are there extra dimensions?
Feb 1, 2010
Experimental Particle Physics
+ many more…
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How can we answer these
Fundamental Questions?
Particle Accelerators
– Reach very high collision energies to probe
extremely small distance scales (< 10-18 m)
– Research at the energy frontier (a few TeV) with the
ATLAS experiment at the Large Hadron Collider (LHC)
 10 x higher energy than previous colliders 
search for
Higgs boson (origin of mass?)
SuperSymmetric particles (dark matter candidate?)
New interactions (heavy gauge bosons, extra dimensions?)
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The Large Hadron Collider (LHC)
Proton-proton collider
circumference = 27 km
Energy = 7 TeV / beam
√s = 14 TeV
Lake Geneva

CERN Main Site

ATLAS
CMS
Stored energy / beam
= 350 MJ (!)
Bunch spacing = 25 ns
 40 MHz crossing rate
Design luminosity
= 1034 cm-2 s-1
Number of interactions
per crossing ~23
Collisions expected
in late 2009
Run for ~10-15 years
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The ATLAS Detector @ LHC
Muon Detectors
EM Calorimeter
Inner Tracker
Hadronic Calorimeter
Diameter
Barrel toroid length
End-cap end-wall chamber span
Overall weight
Feb 1, 2010
Experimental Particle Physics
25 m
26 m
46 m
7000 Tons
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▪
November 2005
February 2008
August 2006
Feb 1, 2010
Experimental Particle Physics
September
8 2006
ATLAS Data Event
Feb 1, 2010
Experimental Particle Physics
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UMass Work on ATLAS
Software development for Muon Spectrometer
–
Leading muon reconstruction effort
(SW co-coordinator, EM event data model leader)
–
Validation of detector description, performance improvements
Physics analysis = Search for new physics
–
Search for new heavy gauge bosons (new interactions)
–
Alternatives to Higgs mechanism (origin of mass)
–
Signs of extra (large) dimensions: micro black holes
–
Model-Independent: Hints of things we haven’t thought of yet
More information at http://people.umass.edu/eppex/
Feb 1, 2010
Experimental Particle Physics
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LHC Schedule
First Physics Run at 3.5 GeV on 3.5 GeV begins
now.
Run will continue through 2010 and 2011, with a
goal luminosity of 1 fb-1.
All splices will be repaired in a long (~year)
shutdown.
High-energy 7GeV on 7GeV will begin ~2013.
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Experimental Particle Physics
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