PROTON INDUCED DRELL-YAN DIMUON PRODUCTION AT 800 GeV

title: Measurement of Drell-Yan cross sections and flavor asymmetry in the nucleon sea
abstract: Measurements of Drell-Yan cross sections from the bombardment of liquid deuterium and hydrogen with an 800 GeV proton beam are reported. The relative cross section (σpd/2σpp) directly probes the ratio of anti-down (d) to anti-up (ū) quarks in the nucleon sea, while absolute measurement of the deuterium cross section constrain d+ū. Results are compared with previous experiments and next-to-leading order calculations based on current sets of parton distribution functions.

title: DEVELOPMENT OF RADIO FREQUENCY GUNS AT NSRRC
abstract: Technologies for rf gun-based high brightness injector are being developed at NSRRC. An X-band photo-cathode rf gun has been constructed and operated successfully for coherent electromagnetic radiation research at U.C. Davis. Recent measurement of a 1.5-2 MeV beam from this gun with bunch charge at 25 pC showed that it has a normalized emittance at 1.65 mm-mrad. As a successive project, a 100 MeV electron beam injector system with a thermionic rf gun and a photo-cathode rf gun that share the same 2998 MHz rf linac is being designed as the pre-injector of the TPS (Taiwan Photon Source) booster as well as beam injector for novel light source research. For evaluation purposes, a prototype thermionic rf gun system is now under construction at NSRRC with the existing 2856 MHz high power microwave system as the driver source.

title: Unnatural parity resonances in the positron-excited hydrogen system
abstract: We present an investigation of resonances with unnatural parities in positron scattering by excited hydrogen. The momentum space coupled channels optical potential method has been used. Positronium formation channels have been included via a complex equivalent local potential. States with angular momenta L = 1 to L = 2 and parity (−1)L+1 are calculated.

title: Characterization and Tuning of A Microwave Gun Cavity
abstract: A microwave electron gun system is being constructed to evaluate the feasibility of using such system as the electron source for the linac pre-injector in storage ring synchrotron radiation sources and for novel linac-based light source R&D at NSRRC. A 2856 MHz SSRL-type microwave gun cavity has been fabricated in house for this purpose. Properties of the cavity resonant modes have been characterized as a function of side-coupled cell plunger position. Special tuning plunger design for this cell allows re-adjustment of field ratio even after brazing. Field amplitude ratio of the cavity full cell to half cell has now been tuned to 2:1. That is the optimized ratio for low energy bunch compression by an alpha magnet.

title: GENERATION OF ULTRA-SHORT ELECTRON BUNCHES FOR LIGHT SOURCE RESEARCH
abstract: An S-band thermionic 1.5-cell rf gun injector system is being built at NSRRC for Taiwan Photon Source (TPS) booster. At optimized field ratio, an electron beam with linear energy chirp can be generated by the rf gun. The beam is then compressed by an alpha magnet such that ultra-short electron bunches at femto-second bunch length can be obtained. Particle dynamics has been studied for an rf gun with nose cone at the cathode, simulation results show that 74 pC bunches at about 97 fs is achievable. Some of the critical components such as the rf gun and alpha magnet have been fabricated and being tested in house. Experiments for intense coherent THz radiations and tunable femto-second X-ray from ultra-short bunches are being proposed as future applications.

title: False vacuum decay in generalized extended inflation
abstract: We study false-vacuum decay in context of generalized extended inflationary theories, and compute the bubble nucleation rates for these theories in the limit of G N → 0. We find that the time dependence of the nucleation rate can be exponentially strong through the time dependence of the Jordan—Brans—Dicke field. This can have a pronounced effect on whether extended inflation can be successfully implemented.

title: Fast detection and automatic parameter estimation of a gravitational wave signal with a novel method
abstract: The detection of gravitational wave usually requires to match the measurement data with a large number of templates, which is computationally very expensive. Compressed sensing methods allow one to match the data with a small number of templates and interpolate the rest. However, the interpolation process is still computationally expensive. In this article, we designed a novel method that only requires to match the data with a few templates, yet without needing any interpolation process. The algorithm worked well for signals with relatively high SNRs. It also showed promise for low SNRs signals.

title: Hadron Production in Au + Au Collisions at 4 A GeV from AGS-E866

title: Effects of correlation between merging steps on the global halo formation
abstract: The excursion set theory of halo formation is modified by adopting the fractional Brownian motion, to account for possible correlation between merging steps. We worked out analytically the conditional mass function, halo merging rate and formation time distribution in the spherical collapse model. We also developed an approximation for the ellipsoidal collapse model and applied it to the calculation of the conditional mass function and the halo formation time distribution. For models in which the steps are positively correlated, the halo merger rate is enhanced when the accreted mass is less than similar to 25M*, while for the negatively correlated case this rate is reduced. Compared with the standard model in which the steps are uncorrelated, the models with positively correlated steps produce more aged population in small mass haloes and more younger population in large mass haloes, while for the models with negatively correlated steps the opposite is true. An examination of simulation results shows that a weakly positive correlation between successive merging steps appears to fit best. We have also found a systematic effect in the measured mass function due to the finite volume of simulations. In future work, this will be included in the halo model to accurately predict the three-point correlation function estimated from simulations.

title: Neutral hadron production at LEP with the L3 detector