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Ian Ross Rose-Hulman Institute of Technology Mentor: Dr. Richard Teuscher University of Toronto ATLAS Group. ATLAS Calorimetery: Cosmic Ray Commissioning. Overview. Cosmics in ATLAS Analysis: What to Look For and How to Find It Example Runs and Events Cosmics as a Background

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Presentation Transcript
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Ian RossRose-Hulman Institute of TechnologyMentor: Dr. Richard TeuscherUniversity of Toronto ATLAS Group

ATLAS Calorimetery:

Cosmic Ray Commissioning

overview
Overview
  • Cosmics in ATLAS
  • Analysis: What to Look For and How to Find It
    • Example Runs and Events
  • Cosmics as a Background
    • Spectrum of high energy hits and missing transverse energy
  • Travel
  • Acknowledgements

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

cosmics in atlas why
Cosmics in ATLAS: Why?
  • Analysis of cosmic ray events provides valuable information about the status of detector modules and triggering mechanisms
    • Identify and tag malfunctioning cells
    • Ensure proper calibration and function of reconstruction software
  • Determine frequency and impact of significant cosmic events as a background to beam collision events

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

cosmics in atlas a superficial explanation
Cosmics in ATLAS: A Superficial Explanation
  • Data collection: Detector is left on, typically overnight
  • Trigger: coincidence of high energy on both top and bottom of detector
  • At best, there are 12 Φmodules on top and 12 Φmodules on bottom that can be used as triggers.

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

what can happen case 1 minimum ionization
What Can Happen: Case 1 (Minimum Ionization)

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

what can happen case 2 hard brem
What Can Happen: Case 2 (Hard Brem)

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

what can happen case 3 air shower
What Can Happen: Case 3 (Air Shower)

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

analysis the basic process
Analysis - The Basic Process
  • Data is stored in raw format, then converted to more amiable ntuple (through Athena)
  • Distribution of energy across detector is examined to find and cut malfunctioning cells
  • Use ROOT to find and characterize high-energy events
  • Events are reconstructed for further examination (through Atlantis or other event displays)

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

example run 11000
Example: Run 11000
  • Plot displays how many times during the run a cell reported an energy of >400 MeV
  • Cells in lower left are malfunctioning: way too many high-energy events
    • LBC41 – Known problem cell that has since been fixed

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

picking out the cosmics
Picking out the Cosmics
  • Malfunctioning cells are removed, and a histogram holding every cell’s energy for every event is constructed.
  • Outlying events often indicate cosmic ray hits.
    • Mostly brem hits, but also fireworks (cosmic air showers)
  • Cosmics still exist lower at lower energies, but sometimes hide among noise and must be combed out.

(MeV)

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

ex hard brem event 776 from run 11000
Ex. Hard Brem – Event 776 from Run 11000

Cosmic ray strikes detector and slows down, radiating energy as it does so

Liquid Argon pulse

Bad cell

(LBC41)

Tile Calorimeter pulse

Bremsstrahlung hit

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

ex fireworks event 3481 from run 11000
Ex. Fireworks – Event 3481 from Run 11000

Air shower event

Cosmic ray collides with air particle, causing a cascade of energetic particles to shower over the detector

Much rarer than Brem hits.

773 GeV spread across entire active detector

Largest single hit was 73 GeV

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

pmt saturation event 1630 run 11000
PMT Saturation – Event 1630 Run 11000

Tile LBC41: known to be malfunctioning during the run

Enormous amount of energy in this cell!

PMTs are saturating!

LBC15 B5 TILE cell:

id = 5/1/-1/14/4/1/0/0

E Max = 2496.36 GeV

ET Max = 2263.30 GeV

ET Sum = 2477.43 GeV

η = -.4500 ± .1000

Φ = 81.6 ± 5.6°

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

saturation event
Saturation Event
  • Saturation occurs at 1023 ADC counts
  • Calibration fits pulse, de-weighting the saturated samples by assigning them with a very large error in the fit

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

pulse shape of neighbors indicates real physics hit
Pulse shape of neighbors indicates real physics hit

0.79 GeV

1.13 GeV

2496.36 GeV

2.87 GeV

0.43 GeV

0.58 GeV

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

more neighbor evidence
More Neighbor Evidence

The next cell (in Eta) also recorded a significant pulse for this event

LBC15 B6 TILE cell:

id = 5/1/-1/14/5/1/0/0

E Max = 246.78 GeV

ET Max = 213.64 GeV

ET Sum = 214.50 GeV

η = -.5500 ± .1000

Φ = 81.6 ± 5.6°

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

cosmics as a background
Cosmics as a Background
  • We would like to know how often high energy cosmics will appear as a background in ATLAS events of interest.
  • More specifically, we would like to know what kind of effects these cosmics may have on the transverse energy balance.
  • Sam Posen and I have constructed a spectrum to get an idea of how frequently cosmics could potentially disrupt ATLAS

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

why etransmiss
Why ETransMiss?
  • Barring any new physics, events in the LHC run should have balancing transverse energy and momentum.
    • Missing transverse energy can imply exotic new physics (like SUSY!)
  • Cosmic rays can disrupt this balance, potentially leading to ‘fake’ ETMiss signals.
  • Cataloging all significant cosmic events can give insight into this effect.

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

etransmiss making the catalog
ETransMiss – Making the Catalog

y

  • Every cell has an geometric address in standard ATLAS coordinates (Φ,η).
  • The energy of each cell is ‘projected’ into Ex(i), Ey(i).
  • Summing over all of the properly functioning cells yields a total Ex and Ey. The total missing transverse energy is:

θ

Φ

z

x

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

current spectrum
Current Spectrum

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

travel
Travel!

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group

acknowledgements
Acknowledgements
  • Richard Teuscher, Adam Gibson, Sam Posen, and the University of Toronto Group
  • Prof. Jean Krisch, Prof. Homer Neal, Dr. Steve Goldfarb, and Jeremy Herr
  • The NSF and University of Michigan

Questions?

Ian Ross - ATLAS Calorimeter: Cosmic Ray Commisioning University of Toronto Group