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Tesi etd-09172012-093301

Thesis type
Tesi di laurea magistrale
Study of Requirements and performances of the electromagnetic calorimeter for the Mu2e experiment at FermiLab
Corso di studi
relatore Dott. Miscetti, Stefano
relatore Prof. Cervelli, Franco
Parole chiave
  • calorimetry
  • Mu2e
  • EMC
Data inizio appello
Riassunto analitico
The aim of the Mu2e experiment is to measure the ratio between the rate of the neutrinoless, coherent conversion of muons into electrons in the field of a nucleus, and the rate of ordinary muon capture on the nucleus:
Rμe = μ− +A(Z,N)→e− +A(Z,N) . (1) μ− +A(Z,N)→νμ +A(Z−1,N)
The muon conversion represents a powerful process to search for charged lepton flavor violation (CLFV). Thus far no CLFV interaction has been observed expe- rimentally; the current best experimental limit on muon-to-electron conversion is from the SINDRUM II experiment, using a gold target: Rμe < 6.1 × 10−13 @ 90% C.L. .
Mu2e Experiment will collect ∼ 5.76 × 10−17 stopped muons in three years of runs so to reach a sensitivity of ∼ 10−17 (four order of magnitude better than SINDRUM II). The experiment set-up consists of three main magnets: 1) a Pro- duction Solenoid, where a 8 GeV proton beam impact on a Tungstate target to produce π−, 2) a Transport Solenoid, where the μ−’s, resulting from the π− decays,

are filtered, 3) a Detector Solenoid (DS), where μ−’s are stopped in an Al targets. Possible electrons resulting from a muon conversion are identified by two different detectors operating inside the DS field. The detectors are: a Straw Tubes Tracker, measuring the electron momentum, and a LYSO Crystal Calorimeter, expected to measure its energy.
If an orbiting μ− converts, a 105 MeV electron is produced: therefore the conversion signature is an isolated electron with the energy of a muon. For this reason the tracker is required to have high momentum resolution (≈ 150 keV). The calorimeter is needed to help the rejection of different backgrounds and also to check the reliability of the electron track reconstruction. For these puposes the calorimeter must have an excellent energy resolution at 100 MeV (less than 3%), a good spatial resolution on the track impact point (≈ 1 cm), and 1 nsec time resolution.
This thesis is devoted to verify that the proposed crystal calorimeter is capable to fulfill all these requirements. This check is done by means of Monte Carlo si- mulations within the Mu2e framework and using recent experimental results from studies on the LYSO crystals. Finally a calculation of the Mu2e sensitivity is also shown for a “calorimeter stand alone” configuration, i.e. without any information from the tracker.