1,522 research outputs found
BHAGEN-1PH: A Monte Carlo event generator for radiative Bhabha scattering
BHAGEN-1PH is a FORTRAN program providing fast Monte Carlo event generation
of the process , within electroweak theory, for
both unpolarized beams and also for the longitudinally polarized electron beam.
The program is designed for final leptons outside a small cone around the
initial leptons direction and has a new algorithm allowing also for a fast
generation of non collinear initial and final emission, as well as for
asymmetric and different angular cuts for final leptons.Comment: 23 pages, plain Tex, no figure
Simulation of the process within electroweak theory with longitudinally polarized initial electrons
We present simple analytic expressions for the distributions of the Bhabha
scattering process with emission of one hard photon, including weak boson
exchanges, and with longitudinal polarization of the initial electron. The
results from the Monte Carlo generator BHAGEN-1PH, based on these expressions,
are presented and compared, for the unpolarized case, with those existing in
literature.Comment: 9 pages, plain Tex, no figures, small change in Table
The Pseudothreshold Expansion of the 2-loop Sunrise Selfmass Master Amplitudes
The values at pseudothreshold of two loop sunrise master amplitudes with
arbitrary masses are obtained by solving a system of differential equations.
The expansion at pseudothreshold of the amplitudes is constructed and some
lowest terms are explicitly presented.Comment: 1+22 pages, Latex, no figures, changes in Eq.(41),(44),(47
The Threshold Expansion of the 2-loop Sunrise Selfmass Master Amplitudes
The threshold behavior of the master amplitudes for two loop sunrise
self-mass graph is studied by solving the system of differential equations,
which they satisfy. The expansion at the threshold of the master amplitudes is
obtained analytically for arbitrary masses.Comment: 1+18 pages, Latex, no figures, as in Journal reference with more
changes in Eq.(31),(42),(45
One Loop Multiphoton Helicity Amplitudes
We use the solutions to the recursion relations for double-off-shell fermion
currents to compute helicity amplitudes for -photon scattering and
electron-positron annihilation to photons in the massless limit of QED. The
form of these solutions is simple enough to allow {\it all}\ of the
integrations to be performed explicitly. For -photon scattering, we find
that unless , the amplitudes for the helicity configurations (+++...+) and
(-++...+) vanish to one-loop order.Comment: 27 pages + 4 uuencoded figures (included), Fermilab-Pub-93/327-T,
RevTe
Seroprevalence of bluetongue serotype 8 in cattle in the Netherlands in spring 2007, and its consequences
A cross-sectional study was carried out in spring 2007, at the end of the first bluetongue outbreak season, to determine the geographical spread of bluetongue virus serotype 8 (BTV-8) infection in cattle in the Netherlands and the consequences for some production parameters. Blood samples from cattle submitted to the laboratory of the Dutch Animal Health Service for other voluntary and obligatory health programmes were tested serologically for BTV-8. in total, 37,073 samples were tested and 659 (1.78 per cent) were seropositive. The samples came from 5436 herds, of which 45 per cent of herds had only one sample submitted from them. The prevalence was highest in the south of the country, where the outbreak had started, and decreased towards the north. in 340 herds more than 50 per cent of cattle were tested, of which 156 herds were located in infected compartments, and in 37 of these herds (10.9 per cent) at least one positive cow was detected. The average within-herd prevalence in the 37 herds was 39.3 per cent: 2.2 per cent in I I dairy herds, 68.4 per cent in 20 small-scale herds and 14 per cent in four suckler cow herds. The prevalence differed significantly between herd types but did not show a geographical trend. The average net return for milk production amounted to is an element of 2417/cow/year and it decreased significantly on average by is an element of 48/ cow/year in the bluetongue-infected dairy herds during the bluetongue period. on the small-scale farms, the incidence of mortality increased by 3.2 (95 per cent confidence interval [a] 1.2 to 9.1) times in the infected herds during the bluetongue period, but the voluntary culling rate decreased by a factor of 2.3 (95 per cent Cl 1.1 to 4.8)
Time and Organizational Learning: A Review and Agenda for Future Research
This paper examines the time dimensions of organizational learning. While several recent studies have addressed aspects of time in relation to organizational learning, the topic of time has received little attention in reviews of the field, and this promising domain of research is fragmented. The objective of this paper is to bring these dispersed conceptualizations and findings together and to provide a more solid conceptual foundation for the time dimensions of organizational learning as a new research avenue. Three sets of mechanisms are discerned: concerning time as duration; the timing of organizational learning; and the role of the past, present and future in organizational learning. Each of these perspectives offers unique insights, which when integrated can help map new directions for future research
Exact Results on e+ e- --> e+ e- + 2 Photons at SLC/LEP Energies
We use the spinor methods of the CALKUL collaboration, as realized by Xu,
Zhang and Chang, to calculate the differential cross section for e+ e- --> e+
e- + 2 photons for c.m.s. energies in the SLC/LEP regime. An explicit complete
formula for the respective cross section is obtained. The leading log
approximation is used to check the formula. Applications of the formula to high
precision luminosity calculations at SLC/LEP are discussed.Comment: 16 pages(LaTeX), UTHEP-92-0601 (contains corrected figures
Sideband cooling while preserving coherences in the nuclear spin state in group-II-like atoms
We propose a method for laser cooling group-II-like atoms without changing
the quantum state of their nuclear spins, thus preserving coherences that are
usually destroyed by optical pumping. As group-II-like atoms have a
closed-shell ground state, nuclear spin and electronic degrees of freedom are
decoupled, allowing for independent manipulation. The hyperfine interaction
that couples these degrees of freedom in excited states can be suppressed
through the application of external magnetic fields. Our protocol employs
resolved-sideband cooling on the forbidden clock transition, , with quenching via coupling to the rapidly decaying state,
deep in the Paschen-Back regime. This makes it possible to laser cool neutral
atomic qubits without destroying the quantum information stored in their
nuclear spins, as shown in two examples, Yb and Sr.Comment: 4 pages, 3 figures v4: minor changes in text, changes in the
references, published versio
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