The laser calibration system of the new g-2 experiment at fermilab
In this activity, aimed to provide a laser calibration system for the new g-2 experiment at Fermilab, INO researchers are associated with the Laboratori Nazionali di Frascati (LNF) section of the Istituto Nazionale di Fisica Nucleare (INFN) and part of the italian “g-2” collaboration. The actual components of this collaboration are listed below:
A. Anastasi<sup>1,3</sup>, D. Babusci<sup>1</sup>, A. Basti<sup>12</sup>, F. Bedeschi<sup>12</sup>, G. Cantatore<sup>4,7</sup>, D. Cauz<sup>4,9</sup>,
S. Dabagov<sup>1</sup>, G. Di Sciascio<sup>6</sup>, R. Di Stefano<sup>5,10</sup>, C. Ferrari<sup>1,2</sup>,
A. Fioretti<sup>1,2</sup>, C. Gabbanini<sup>1,2</sup>, D. Hampai<sup>1</sup>, M. Iacovacci<sup>5,8</sup>,
M. Karuza<sup>4,11</sup>, F. Marignetti<sup>5,10</sup>, S. Mastroianni<sup>8</sup>, D. Moricciani<sup>6</sup>,
G. Pauletta<sup>4,9</sup>, L. Santi<sup>4,9</sup>,G. Venanzoni<sup>1</sup>
<sup>1</sup>Laboratori Nazionali Frascati dell’ INFN, Via E. Fermi 40, 00044 Frascati, Italy
<sup>2</sup>Istituto Nazionale di Ottica del C.N.R., UOS Pisa, via Moruzzi 1, 56124, Pisa, Italy
<sup>3</sup>Dipartimento di Fisica e di Scienze della Terra, Universita di Messina, Messina, Italy
<sup>4</sup>INFN, Sezione di Trieste e G.C. di Udine, Italy
<sup>5</sup>INFN, Sezione di Napoli, Italy
<sup>6</sup>INFN, Sezione di Roma Tor Vergata, Roma, Italy
<sup>7</sup>Università di Trieste, Trieste, Italy
<sup>8</sup>Università di Napoli, Napoli, Italy
<sup>9</sup>Università di Udine, Udine, Italy
<sup>10</sup>Università di Cassino, Cassino, Italy
<sup>11</sup>University of Rijeka, Rijeka, Croatia
<sup>12</sup>INFN, Sezione di Pisa, Italy
The muon anomaly a=(g-2)/2 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 search for new physics. Since the first precision measurement of a from the E821 experiment at Brookhaven National Laboratory (BNL) in 2001, there has been a discrepancy between its experimental value and the SM prediction. This discrepancy has been slowly growing to more than 3 standard deviations due to impressive theoretical and experimental achievements, and its now dominated by the uncertainty in the theoretical calculation.
A new experiment, E989  at Fermilab, to measure the muon g-2 to a precision of 1.6×10-10 (0.14 ppm), is expected to start data taking in 2017. To achieve a statistical uncertainty of 0.1 ppm, the total data set must contain more than 1.8×10<sup>11</sup> detected positrons with energy greater than 1.8 GeV. The systematical uncertainty will be reduced to 0.1 ppm thanks to: (i) a higher proton rate but with less protons per bunch than at BNL; (ii) 900m pion decay line (BNL: 80m); (iii) less pion flash at muon ring injection; (iiii)improved detectors against signal pileup, new electronics and better shimming to reduce B-field variations.
The new experiment will require upgrades of detectors, electronics and data acquisition equipment to handle the much higher data volumes and slightly higher instantaneous rates. In particular, it will require a continuous monitoring and state-of-art calibration of the detectors, whose response may vary on both the short timescale of a single fill, and on the long one of an entire run. This will be attained by sending trains of calibrated laser pulses simultaneously on all the detectors.