Position Resolution in the CMS ECAL Nicolas Osman

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Position Resolution in the CMS ECAL Nicolas Osman 16 th of August 2006 1/10

Position Resolution in the CMS ECAL Nicolas Osman 16 th of August 2006 1/10

Calorimetry in the CMS Muons Electrons & Photons (09. 30 am) Hadrons 2/10

Calorimetry in the CMS Muons Electrons & Photons (09. 30 am) Hadrons 2/10

Calorimeter Design A calorimeter consists of alternating layers of absorbing and scintillating material. Some

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. 3/10

Starting with Crystals… www. bbc. co. uk The CMS ECAL uses Pb. WO 4

Starting with Crystals… www. bbc. co. uk The CMS ECAL uses Pb. WO 4 crystals: they are transparent and very dense. The crystals come from Russia and China. www. eno. org 4/10

Electromagnetic Shower ~ 80% of energy deposited in one crystal 5/10

Electromagnetic Shower ~ 80% of energy deposited in one crystal 5/10

Finding the Origin of the Shower We can take a weighted average to find

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 6/10

The Slide with Formulae (Discard negative weights) 7/10

The Slide with Formulae (Discard negative weights) 7/10

Some Results 8/10

Some Results 8/10

Why do we want to do this? ? z P? = Pg 1 +

Why do we want to do this? ? z P? = Pg 1 + Pg 2 P? 2 = Pg 12 + Pg 22 + 2 Pg 1. Pg 2 M? 2 = 2 Eg 1 Eg 2 _ 2|pg 1||pg 2|cosz M? 2 = 2 Eg 1 Eg 2 (1_ cosz) If M? = 91 Gev, it’s a Z 0; if M? = 145 Ge. V… 9/10

Where Next? The resolution is currently ~ 2 mm: can this be improved? Could

Where Next? The resolution is currently ~ 2 mm: 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. 10/10

The Eleventh Slide “…a Heap of Jewels, unstrung and unpolisht; yet so dazling in

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 11/10

Acknowledgements I would like to thank my supervisor, Dr. Renaud Bruneliere, and the rest

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! 12/10