Ingen lysbildetittel

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Large Hadron Collider og ATLAS _at_ CERN
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Part 1 LHC and LHC startup
Accelerator was proposed during the
eighties Project approved in 1994.
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Some parameters

• 9600 magnets, out of which 1232 are large dipole
  magnets
• Dipole current 11850 A
• Magnetic field 8,33T
• Proton energy 7 TeV
• 120 Tonnes of Helium used to cool a mass of
  30000 tonnes.

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more parameters

• Vacuum tube pressure10-13 atm
• Vacuum also serves as heat insulation, so in
  total there is 9000 cubic meters of vacuum.

Price 4.6 GCHF 25GNOK (Only the construction)
(how much per physicist per year?)
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What happened on Sept 10th?
It took an hour for the beam to make a full
turn
Thats just 27 km/h????.
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tertiary collimators 140 m
BPTX 175 m
ATLAS was ready for first beam
Two LHC start-up scenarios

• Muon system (MDT, RPC, TGC) on at reduced HV
• LAr (-FCAL HV), Tile on
• TRT on, SCT reduced HV, Pixel off
• BCM, LUCID, MinBias Scint. (MBTS), Beam pickups
  (BPTX)
• L1 trigger processor, DAQ up and running, HLT
  available (but used for streaming only)

• Open all collimators, go around as far as beam
  goes, correct as needed
• Little activity expected except for accidents
• Go step-by-step, stopping beam on collimators,
  re-align with centre, open collimator, keep going
• Splash event from collimators for each beam shot

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Black holes in LHC?

• Black holes could, in principle, be arbitrarily
  small. However, according to standard General
  Relativity, there is no chance to prodce black
  holes at the LHC, since conventional
  gravitational forces between fundamental
  particles are too weak.
• There is no established quantum theory for
  gravitation (certainly needed for small ones).
• Some quantum gravity proposals (involving more
  than 3 spacial dimensions) make speculative
  predictions on production of black holes in
  proton.proton collisions at LHC
• But in these models they are always unstable,
  both because of Hawking radiation, and because
  they always can decay back into the particles
  that produced them.
• (Im of course brainwashed by the Cern/LHC Safety
  Assesment Group, Ellis,Guidice,Mangano,Tkachev,Wie
  demann, CERN-PH-TH/2008-136)

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Cosmic rays

• have produced high energy proton-proton
  collisions for billions of years.
• We are still here.

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LHC ENERGY
From Ellis et al Review of the Safety of LHC
Collisions CERN-PH-TH/2008-136
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LHC
Preparing for this talk last Friday I looked at
some plots monitoring the magnet temperatures. I
found
This
..and this
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Geneva, 20 September 2008. During commissioning
(without beam) of the final LHC sector (sector
34) at high current for operation at 5 TeV, an
incident occurred at mid-day on Friday 19
September resulting in a large helium leak into
the tunnel. Preliminary investigations indicate
that the most likely cause of the problem was a
faulty electrical connection between two magnets,
which probably melted at high current leading to
mechanical failure. CERN s strict safety
regulations ensured that at no time was there any
risk to people. A full investigation is underway,
but it is already clear that the sector will have
to be warmed up for repairs to take place. This
implies a minimum of two months down time for LHC
operation. For the same fault, not uncommon in a
normally conducting machine, the repair time
would be a matter of days. Further details will
be made available as soon as they are known.
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ATLAS in Bergen

• Silicon detectors and detector modules for the
  track reconstruction system.
• Simulation studies of the physics potential.
• Development work for the detector control systems
  and online monitoring.
• The daily running of the experiment
• Study the data

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ATLAS
SCT
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The SemiConductor Tracker (SCT)
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Some numbers(Atlas in Bergen)

• 10 master students already completed
  ATLAS-related theses
• 3 completed PhDs
• 4 active doctoral students
• 5 active master students
• 2 postdocs (Burgess, Sandaker)
• 3 professors (Eigen,Lipniacka,Stugu)
• ATLAS was about 50 of the experimental groups
  activities Now it is about 80 (Theory research
  of Per Osland not included in above figures)

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Detector control system (DCS) and online
monitoring
The development of monitoring tools represents a
large amount of work!
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The running of ATLAS

One shift pr. day (on average) must be taken by a
Bergen person.
Data quality shifts Good for students!
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SCT, ROS and ID global monitoring shifters
Heidi supervises Katarina and Ole (from Oslo)
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Many Bergen people are involved in the
development of monotoring tasks. Everybody will
take shifts during ATLAS operation

• Developers Heidi Sandaker, Arshak Tonyan, Alex
  Kastanas...
• Bergen shifts are organised by Therese Sjursen.
  She and two new master students are currently at
  Cern for shifts ( Keep detector alive and study
  cosmic rays)

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What do the ATLAS events look like?
Quark jets in reality
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H ?ZZ?µµee
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Event with Supersymmetric Particles Six jets of
particles, Two muons with momenta in the
transverse direction of 74 and 84 GeV. They are
visible in the side view going to the left, but
not in the end view (because the exited the
detector in the forward direction). They have
opposite signs. Missing energy in the direction
transverse to the beam of 283 GeV. (Dark
matter???)
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Except for a few scenarios, the identification of
Higgses and/or Supersymmetry or other new physics
will be a painstaking process.

• Events from new physics are likely to be rare.
• Missing energy signals requires careful
  calibration and proper accounting for escaping
  standard particles like neutrinos.
• Must focus on abundant and known processes in the
  beginning.
• B-mesons (quark-antiquark pairs where one of the
  quarks is a b-quark)
• Z,W bosons
• top quarks
• Results from such studies will also give new
  insights that can be published. (In particular
  about strange B-mesons and the top quark)

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Physics activities (present and planned for the
near future)

• B-physics with muons.
• In particular Bs mesons
• adds to the wealth of data collected by BaBaR on
  ordinary B-mesons, vital to understand
  CP-violation.
• Physics involving the tau lepton
• Identification procedures (more difficult than
  muons and electrons, but a number of interesting
  signatures involve the tau lepton.
• Z?t t ( Light Higgses also decay to two taus)
• W?t? (SUSY also often have taus and missing
  energy)
• Top quark decays (these always involve W mesons
  and b-quarks (i.e. B-mesons). top quark decays
  also will produce the Standard Model physics
  signals with the highest energies

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Verification of track fitting procedures by
reconstructing mass of the J/psi
t
Maren Ugland, Master thesis, (main study was to
reconstruct Bs mesons)
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SUSY signals with taus(Simulation study by
Therese Sjursen)
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Conclusion

• After a very promising start of the LHC, we are
  now set back a few months due to a quench.
• Winter shutdown Beams back in 2009.
• Bergen takes an active part in the running of
  ATLAS, and will do so also in the future.
• Aim is to contribute very actively to studies
  related to muon and tau identification, with
  physics goals within B-physics and searches for
  supersymmetric events and higgs particles
  decaying to these particles.
• first thing find and understand standard
  processes such as
• J/psi -gt µ µ
• B-decays
• Z -gt µ µ , t t
• top quak decays