Search

The objective of the CERN RD50 Collaboration is the development of radiation hard semiconductor detectors for very high luminosity colliders, particularly to face the requirements of a possible upgrade scenario of the LHC.This document reports the status of research and main results obtained after the sixth year of activity of the collaboration.

The Fermilab muon g-2 experiment aims to measure the anomalous magnetic dipole moment of the muon, aμ , to a precision of 140 ppb. The current value of aμ was measured at the Brookhaven g − 2 experiment, whose final result was published in 2006 with an uncertainty of 0.54 ppm [1]. The deviated from the Standard Model (SM) prediction by up to 3.6 σ, causing international intrigue that motivated the repetition of the experiment with increased statistics. The experiment’s storage ring (SR) magnet was transported to Fermilab in 2013 to make use of its high-intensity muon beam. This will facilitate a 21-fold increase in statistics that will contribute most of the improved precision in the aμ measurement. In addition, improvements to the experimental hardware are intended to reduce the systematic uncertainty. A major improvement is a new straw tracking detector system, which will measure the beam profile continuously throughout the experiment, in order to mitigate sources of systematic error associated with the beam position and motion. The straw trackers will also be used to perform a muon electric dipole moment (EDM) search. The current world’s best limit on the muon EDM was placed by the Brookhaven g − 2 experiment [2]. The signal for a muon EDM in the g − 2 experiment can be directly measured with the straw tracking detectors, so the upgraded tracking system is expected to enable a reduction in the current limit by a factor of 100. This thesis will describe the design and construction of the straw tracking detectors that took place at the University of Liverpool. The development and optimisation of a track extrapolation algorithm for propagating the track parameters of the decay positrons back to the muon decay position will be presented. The use of this algorithm in measuring the beam profile during the commissioning phase of the experiment will be discussed, and finally, the development of a muon EDM simulation and a preliminary sensitivity study using the track extrapolation algorithm will be presented. [1] Muon g − 2 Collaboration, G. W. Bennett et al., Final report of the E821 muon anomalous magnetic moment measurement at BNL, Phys. Rev. D 73 (2006) 072003. [2] Muon g-2 Collaboration, G. W. Bennett et al., Improved limit on the muon electric dipole moment, Phys. Rev. D 80 (2009) 052008.

The anomalous magnetic moments of leptons have been a long standing test of the standard model of particle physics as they can be both measured experimentally and predicted theoretically with high precision. In particular the anomalous magnetic moment of the muon, aμ, has been favoured due to its sensitivity to new physics effects. Currently the world’s best measurement of aμ was made at Brookhaven National Laboratory (BNL) in 2001 which resulted in a 3σ deviation between the experimental measurement and theoretical prediction. Since this measurement a number of improvements have been made to the theoretical prediction giving a deviation between theoretical prediction and measured value of over 3.5σ. A new experimental effort has been set up at Fermi National Laboratory (FNAL) in order to measure aμ with a factor of four reduction in the experimental uncertainties. If these aims are met and the central measurement value stays the same a discrepancy will be discovered providing strong evidence for new physics effects. The FNAL experiment uses the same experimental method as BNL which centres around measuring the precession of the μ+ spin after circling an extremely precise magnetic storage ring. To reduce the experimental uncertainties in the new experiment straw tracking detectors have been constructed and installed into the Fermilab muon g-2 storage ring. These detectors measure the stored muon beam profile throughout each fill and enable key independent cross checks of the calorimeter detector systems. This body of work presents the design, construction, testing, installation and commissioning of the straw tracking detectors as well as the ability to match the straw tracker tracks and calorimeter clusters with a focus on measuring the calorimeter pileup rate.