1. The Atlas Tile Calorimeter Muon Studies at 90° Presented at CERN by Michael Borysow for the University of Michigan REU Program 14/08/03

2. Outline Tile Calorimeter Description What is Calorimetry? Specifics to the Atlas Tile Calorimeter My Analysis Muons at 90 Degrees Discoveries Conclusions

3. Atlas Overview Four Major Components Inner Tracker Calorimeter – Electromagnetic Calorimeter – Hadronic Muon Spectrometer Magnet System

5. What is Calorimetry? Calorimetry refers to the detection of particles through total absorption in a block of matter. Calorimetry is a destructive method. The only exceptions being muons. Muons can penetrate substantial amounts of mass represented by the calorimeter, thus they become ID’d as muons. True Calorimeters measure the total energy of a particle and are made of a single substance, such as Germanium or NaI crystal. The Atlas Tile Calorimeter is a Sampling Calorimeter.

6. Sampling Calorimeters Sampling Calorimeters are made of more than one substance Active Medium Generates light or charge that forms the basis of the calorimeter signal Passive Medium Absorbs energy In Sampling Calorimeters, only a small fraction of the energy is deposited in the active medium. The advantage of a Sampling Calorimeter is that it is much cheaper and smaller. The goal is still to stop the particle, and the passive medium can help do this much more quickly.

7. Benefits of a Calorimeter Calorimeters, with tracking data, allow for effective identification of particles. Can measure the energy of neutral particles, whereas a magnetic spectrometer cannot. Fast Response time; Can be used as a trigger for other detector components.

8. The Tile Calorimeter Made of 64x4 submodules Two Long Barrels Two Extended Barrels Each submodule is composed of alternating tiles of polystyrene and steel separated into 11 tile rows. Polystyrene is the active medium, while steel is the passive medium.

9. Extended Barrels Long Barrels

12. The Tile Calorimeter Polystyrene acts as a scintillating material. Through various processes, molecules and atoms will become excited, and then emit light when they drop to the ground state. The scintillation light is picked up by wavelength shifting fibers (WSF) and carried to Photo Multiplier Tubes (PMTs). The PMTs then produce an electronic signal, which is digitized and sent to the Data Acquisition Systems.

14. Cell Layout Each cell can be read out individually in two channels. Each cell has WSFs which on either side. These fibers carry the light to the PMT. WSFs are used, because the light emitted by the scintillation process is ~100 nm. The PMTs are most sensitive around ~550nm.

15. Studies at 90° Studies at 90 degrees are used to check tile row uniformity. Muons are made use of for the reason that they deposit the roughly the same energy in each cell (per Tile) as they pass through the detector. Thus, muons are useful for detecting bad equipment.

17. Tile Row Uniformity

18. Channel Uniformity per Row

19. Channel Summary

20. Distribution of Channel Response

21. Geometry Problems? Currently investigating possibility of misalignment of the test setup.

22. Acknowledgements Jean Krisch, Homer Neal, and Tom Dershem My Adviser, Richard Teuscher The Argonne Boys University of Michigan National Science Foundation Ford Motor Company