Session D2 - Searches for New Physics and New Windows on Nuclear Structure.
INVITED session, Saturday afternoon, May 01
Plaza D, Adam's Mark Hotel
TWIST, the TRIUMF Weak Interaction Symmetry Test, has taken data in the first simultaneous precision measurement of the muon decay parameters \rho, \delta, and P_\mu\xi. The ultimate goal of the experiment is to determine each of these parameters to a few parts in 10^4. With this precision TWIST will confront several proposed extensions to the Standard Model. For example, TWIST will be sensitive to right-handed W bosons with masses up to 800 GeV without needing to make assumptions about the form of the right-handed CKM matrix.
The TWIST spectrometer is made up of 44 drift chambers and 12 proportional chambers mounted in a 2 T solenoidal magnetic field. The chambers are divided symmetrically by a stopping target in the center of the spectrometer where highly polarized positive muons are stopped. The confining field results in a large angular and energy acceptance for the decay positrons that are tracked through the wire chambers. Decay rates of several kHz allow for the collection and analysis of very large data samples making TWIST a systematics-dominated experiment. Data are being analyzed at present that are expected to provide intermediate results for \rho and \delta to ~10^-3.
The TWIST experiment will be described, and the current state of the data analysis will be discussed.