1 A. T. Goshaw Duke University

HEP101 - 1 March 29, 2010

The ATLAS Experiment and the CERN Large Hadron Collider

HEP 101 Plan

•  March 29: Introduction and basic HEP terminology •  March 30: Special LHC event: first high-energy p+p

collisions. Live video broadcasts in physics lobby and in this room. •  April 5: relativistic mechanics and applications to HEP •  ?? : particle detectors •  ?? : analysis tools used in HEP research •  ??

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Some web sites

•  CERN LHC home page: http://lhc.web.cern.ch/lhc/ •  The ATLAS home page: http://atlas.web.cern.ch/Atlas/Collaboration/ •  ATLAS event displays: http://atlas.web.cern.ch/Atlas/public/

EVTDISPLAY/events.html

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Orientation: CERN CERN = the Conseil Europeen pour la Recherche Nuclearie or

now know as The European Organization for Nuclear Research

  Located on the border between Switzerland and France

  Currently the largest HEP Laboratory in the world, employing ~ 2500 scientists and staff plus ~ 8000

visiting scientists.

  Founded in 1954 as one of Europe’s first joint scientific efforts.

  There are 20 CERN member states plus broad participation from 580 Universities and Institutes throughout the world

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Geneva Airport

LHC 27 km ring (previously used for LEP e+e- collider)

CERN main site

French-Swiss border

Orientation: CERN

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Orientation: the Large Hadron Collider    The 27 kilometer LHC ring consists of 1232 dipole (bending) 392 quadrupole (focusing) magnets.

   The protons travel in a pipe with a vacuum better than outer space.

dipoles of 15 m length

   After accelerating the protons with RF electric fields to an energy of 7 TeV, the counter-rotating beams are focused to collide at a pp center of mass energy of 14 TeV.

   The superconducting dipoles provide 8.3 T magnetic fields and operate at 1.9 K (-271 oC) using super-fluid helium.

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2008

Orientation: the Large Hadron Collider

   100 years ago Kamerlingh Onnes first liquefied helium in Leiden (60 ml in 1 hour).

   The superconducting magnets in the LHC require vast amounts of liquid nitrogen and helium. An enormous engineering challenge.

1908

   In the LHC today, 32000 liters of helium are liquefied per hour by eight huge cryogenic plants.

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Orientation: the Large Hadron Collider

Comparison to previous accelerators

ability to create massive particles

ability to produce

rare particles

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The LHC experiments

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ATLAS Detector

45 m

24 m

7000 T

The results of a simulated pp collision in the ATLAS detector (transverse view, the beams are perpendicular to the screen)

A Toroidal LHC ApparatuS

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Building a ship in a bottle

Today

ATLAS

is built

Cavern 92m underground

55m long 32m wide 35m high

February 2004

A video tour of a collision

•  You can load a movie from: http://pdgusers.lbl.gov/~pequenao/

EventDisplay/

•  ATLAS blogs and twitter are available at: http://www.atlas.ch/blog/ http://twitter.com/ATLASexperiment

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Now to the HEP101 questions for today’s discussion

1. How many fundamental forces have been observed?

2. How many elementary particles?

3. What are: fermions, bosons, hadrons, baryons, mesons, leptons, quarks and WIMPS?

4. What fundamental constants are needed to specify the Structure of relativistic mechanics and quantum mechanics?

5. What are the fundamental conservation laws of Nature?

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Higgs Boson(s)?

   One major reason for building the Large Hadron Collider and detectors such as ATLAS is to explore the origin of electroweak symmetry breaking.

   Electroweak symmetry breaking is the generic term given to mechanisms that give mass to particles in theories where the exact symmetry applies to mass-less particles.

   One such mechanism was first proposed by Peter Higgs. He postulated the existence of a field that couples to particles and, through this interaction, generates particle masses.

Higgs Bosons

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Recent astrophysical measurements indicate that the Universe is made of:   5% of known matter   25 % of “Dark Matter” no known particle can explain it.   70% of “Dark Energy”

Supersymmetry (a particle physics theory) predicts new (heavy) elementary particles, not yet observed. Among them the neutralino, our present best candidate for the Universe Dark Matter (its predicted features are in agreement with astrophysics observations and cosmological predictions). It is expected to be light enough to be produced abundantly at the LHC !

Today we understand only 5% of the composition of the Universe

The LHC may produce WIMPS

End HEP 101 - 1

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6. What is the Standard Model? What forces does it describe? Are all its basic components observed?

7. Why are high energy accelerators needed to test the Standard Model and other elementary particle theories?

This will lead naturally into the lecture on the basics of Relativistic Mechanics, and its use in dealing with the Creation of particles in high energy LHC pp collisions.

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