We propose an experiment (Mu3e) to search for the lepton flavour violating decay mu+ -> e+e-e+. We aim for an ultimate sensitivity of one in 10^16 mu-decays, four orders of magnitude better than previous searches. This sensitivity is made possible by
exploiting modern silicon pixel detectors providing high spatial resolution and hodoscopes using scintillating fibres and tiles providing precise timing information at high particle rates.
Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physi
cs uncertainties. We aimed to perform the beam polarization measurement to an accuracy of $Delta P_{beam}/P_{beam} < 5%$. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features textit{proton-proton} elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power $A_N$ of this process has allowed us to achieve $Delta P_{beam}/P_{beam} =4.2%$ in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of $A_N$ in the CNI region (four-momentum transfer squared $0.001 < -t < 0.032 ~ ({rm GeV}/c)^2$) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.
Precise measurements of the single spin asymmetry, $A_N$ and the double spin asymmetry, $A_{NN}$, in proton-proton (textit{pp}) elastic scattering in the region of four-momentum transfer squared $0.001 < -t < 0.032 ({rm GeV}/c)^2$ have been performed
using a polarized atomic hydrogen gas jet target and the RHIC polarized proton beam at 24 GeV/$c$ and 100 GeV/$c$. The polarized gaseous proton target allowed us to achieve the measurement of $A_{NN}$ in the CNI region for the first time. Our results of $A_N$ and $A_{NN}$ provide significant constraints to determine the magnitude of poorly known hadronic single and double spin-flip amplitudes at this energy.
