# The Energy Calibration System of the muon g-2 experiment at Fermilab.

Sorbara M. per la Collaborazione g-2

Comunicazione
I - Fisica nucleare e subnucleare
Aula 32B-1 - Venerdì 21 h 10:15 - 12:00
The muon anomaly, a$\mu$, is a low-energy observable, which can be both measured and computed to high precision, therefore it provides an important test of the Standard Model (SM) and it is a sensitive probe for new physics. The muon anomaly has been measured to 0.54 parts per million by the E821 experiment at the Brookhaven National Laboratory. This result shows a 3 to 4 standard-deviation difference with respect to the SM prediction. A new muon g-2 experiment, E989, is under commissioning at Fermilab, aiming to improve the experimental error by a factor of four to clarify the origin of this difference. The experiment will run with a positive muon beam. The decay positrons will be detected by 24 electromagnetic calorimeters placed on the inner radius of a magnetic storage ring. They accurately measure the arrival time and energy of the positron which curl to the inside of the ring following muon decay. Each calorimeter consists of 54 lead fluoride (PbF2) crystals in a 6 high by 9 wide array. I will present the calorimeter system and energy calibration as obtained by lost muons in the storage ring.