122501083
The pomeron and the f-trajectory in the topological expansion
Abstract The topological expansion for planar and cylinder terms is re-examined using a multi-Regge approximation for the planar, many-particle amplitude. The phase structure of the reggeon-reggeon-particle vertex is shown to lead to distinct pomeron and f-trajectories in the imaginary part of the elastic two-body amplitude.
120889645
A topological approach to high-energy large transverse momentum interactions
We discuss the high pT strong interaction from a topological (1/Nf) expansion viewpoint. Topology of quark line graphs is used to classify the underlying process rather than constituent scattering, all constituents being implicitly confined. The distinction between “jets” and “background” is clarified in a very simple dynamical model. Although the model does not require quarks as dynamical entities, many of its features are in agreement with parton model predictions.
18829100
Data acquisition system for the MuLan muon lifetime experiment
Abstract We describe the data acquisition system for the MuLan muon lifetime experiment at Paul Scherrer Institute. The system was designed to record muon decays at rates up to 1 MHz and acquire data at rates up to 60 MB/s. The system employed a parallel network of dual-processor machines and repeating acquisition cycles of deadtime–free time segments in order to reach the design goals. The system incorporated a versatile scheme for control and diagnostics and a custom web interface for monitoring experimental conditions.
121004459
Muon lifetime measurements at PSI
The Fermi constant, GF, is most precisely determined by the muon lifetime, τμ. Calculations of the two‐loop terms in the extraction of GF from τμ in the late 1990’s and early 2000’s reduced the theoretical uncertainty on the extraction by two orders of magnitude and motivated a new generation of muon lifetime experiments. The FAST and MuLan experiments have the most ambitious precision goals, and take place at Paul Scherrer Institute (PSI). Both have released intermediate results, and have compatible final precision goals of 2 ppm and 1 ppm respectively. Their intermediate measurements have improved the world average muon lifetime to τμ = 2.197035 μs is (8 ppm), and new results at the precision goals are expected in 2010. Although the goals are similar, the experiments have different systematic uncertainties and provide an excellent cross‐check on each other.
118600385
Toward a sub-ppm measurement of the Fermi constant
The Fermi constant, G_F, describes the strength of the weak force and is determined most precisely from the mean life of the positive muon, tau_mu. Advances in theory have reduced the theoretical uncertainty on G_F as calculated from tau_mu to a few tenths of a part per million (ppm). The remaining uncertainty on G_F is entirely experimental, and is dominated by the uncertainty on tau_mu. The MuLan experiment is designed to measure the muon lifetime to part-per-million precision, a better-than twenty-fold improvement over the previous generation of experiments. In 2007, we reported an intermediate result, tau_mu=2.197013(24) microseconds (11 ppm), which is in excellent agreement with the previous world average. This mean life was measured using a pulsed surface muon beam stopped in a ferromagnetic target, surrounded by a symmetric scintillator detector array. Since this intermediate measurement, the detector was instrumented with waveform digitizers, the muon beam rate and beam extinction were increased, and two data sets were acquired on different targets, each containing over 10^12 muon decays. These data will lead to a new determination of G_F to better than a part per million.