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Position Resolution in the CMS ECAL

This presentation discusses the design and functionality of the CMS ECAL (Electromagnetic Calorimeter), focusing on muons, electrons, and photons. It explores the use of PbWO4 crystals from Russia and China, the concept of electromagnetic showers, and the calculation of shower positions. The presentation concludes with suggestions for further improvements and testing with ECAL test beam data.

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Position Resolution in the CMS ECAL

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  1. Position Resolution in the CMS ECAL Nicolas Osman 16th of August 2006

  2. Calorimetry in the CMS Muons Electrons & Photons (09.30 am) Hadrons

  3. Calorimeter Design A calorimeter consists of alternating layers of absorbing and scintillating material. Some (very dense) crystals act both as a scintillator and an absorber.

  4. www.bbc.co.uk Starting with Crystals… The CMS ECAL uses PbWO4 crystals: they are transparent and very dense. The crystals come from Russia and China. www.eno.org

  5. Electromagnetic Shower ~ 80% of energy deposited in one crystal

  6. Finding the Origin of the Shower We can take a weighted average to find the position of the centre of the shower; the weights are determined by the energy

  7. The Slide with Formulae (Discard negative weights)

  8. Some Results

  9. z ? Why do we want to do this? P? = Pg1 + Pg2 P?2 = Pg12 + Pg22 + 2Pg1.Pg2 M?2 = 2Eg1Eg2 _ 2|pg1||pg2|cosz M?2 = 2Eg1Eg2 (1_ cosz) If M? = 91 Gev, it’s a Z0; if M? = 145 GeV…

  10. Where Next? The resolution is currently ~ 2mm: can this be improved? Could a comparison with a generated Energy Distribution give better results? Finally, this method has to be tested with ECAL test beam data.

  11. The Eleventh Slide “…a Heap of Jewels, unstrung and unpolisht; yet so dazling in their Disorder, that I soon perceiv'd I had seiz'd a Treasure.” – Nahum Tate

  12. Acknowledgements I would like to thank my supervisor, Dr. Renaud Bruneliere, and the rest of the CMA group. Many thanks to the Summer Student team for this opportunity to come to CERN. Thank you all for turning up and listening!

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