Production of a Higgs pseudoscalar plus two jets in hadronic collisions

We consider the production of a Higgs pseudoscalar accompanied by two jets in hadronic collisions. We work in the limit that the top quark is much heavier than the Higgs pseudoscalar and use an effective Lagrangian for the interactions of gluons with the pseudoscalar. We compute the amplitudes involving: 1) four gluons and the pseudoscalar, 2) two quarks, two gluons and the pseudoscalar and 3) four quarks and the pseudoscalar. We find that the pseudoscalar amplitudes are nearly identical to those for the scalar case, the only differences being the overall size and the relative signs between terms. We present numerical cross sections for proton-proton collisions with center-of-mass energy 14 TeV.Comment: 12 pages, LaTeX, 4 Postscript figures, submitted to Phys. Rev.

Competing communities of users and developers of computer software: competition between open source software and commercial software

The open source movement is a group of volunteer programmers that has recently caused quite a stir in the software market. The volunteers of this group develop computer operating systems, programming languages, and other software. They work together in teams that communicate via the Internet. Their goal is to develop useful software that is available for free and that users can change at will. To enable users to change and improve the software, they distribute their software not only in compiled form (that a computer needs to actually run the software), but also in its source code (the lines of code that programmers write). This cooperation breaks through the usual barriers that separate corporate suppliers from their buyers. This may represent the first example where the Internet enables cooperation on a scale that changes market dynamics. This paper studies the interaction between the network dynamics of the open source movement and the dynamics of a commercial software supplier. It makes our first step in identifying conditions that support a successful development of open source software. We focus on one particular set of projects within the open source movement, namely the Linux computer operating system.management and organization theory ;

The upper limit of the e+e- partial width of X(3872)

The e+e- decay partial width of the recently observed state, X(3872), is estimated using the ISR data collected at the center of mass energy 4.03 GeV in e+e- annihilation experiment by BES at BEPC. It is found that the product of the e+e- partial width and X(3872) --> pi+ pi- J/psi decay branching fraction is less than 10 eV at 90 % confidence level if the J(PC) of X(3872) is 1(--). Together with the potential models and other information, we conclude that X(3872) is very unlikely to be a vector state.Comment: 5 pages, 1 figur

Multiloop String-Like Formulas for QED

Multiloop gauge-theory amplitudes written in the Feynman-parameter representation are poised to take advantage of two important developments of the last decade: the spinor-helicity technique and the superstring reorganization. The former has been considered in a previous article; the latter will be elaborated in this paper. We show here how to write multiloop string-like formulas in the Feynman-parameter representation for any process in QED, including those involving other non-electromagnetic interactions. The general connection between the Feynman-parameter approach and the superstring/first-quantized approach is discussed. In the special case of a one-loop multi-photon amplitude, these formulas reduce to the ones obtained by the superstring and the first quantized methods. The string-like formulas exhibits a simple gauge structure which makes the Ward-Takahashi identity apparent, and enables the integration-by-parts technique of Bern and Kosower to be applied, so that gauge-invariant parts can be extracted diagram-by-diagram with the seagull vertex neglected.Comment: 25 pages in Plain Tex, plus four figures in a postscript file; McGill/92-5

One Loop Multiphoton Helicity Amplitudes

We use the solutions to the recursion relations for double-off-shell fermion currents to compute helicity amplitudes for $n$-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 $n$-photon scattering, we find that unless $n=4$, 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

Multigluon Helicity Amplitudes Involving a Quark Loop

We apply the solution to the recursion relation for the double-off-shell quark current to the problem of computing one loop amplitudes with an arbitrary number of gluons. We are able to compute amplitudes for photon-gluon scattering, electron-positron annihilation to gluons, and gluon-gluon scattering via a quark loop in the case of like-helicity gluons. In addition, we present the result for the one-loop gluon-gluon scattering amplitude when one of the gluons has opposite helicity from the others.Comment: 31 pages (RevTeX) + 2 uuencoded figures (included), Fermilab-Pub-93/389-

Exact O(g^2 alpha_s) top decay width from general massive two-loop integrals

We calculate the b-dependent self-energy of the top quark at O(g^2 \alpha_s) by using a general massive two-loop algorithm proposed in a previous article. From this we derive by unitarity the O(\alpha_s) radiative corrections to the decay width of the top quark, where all effects associated with the $b$ quark mass are included without resorting to a mass expansion. Our results agree with the analytical results available for the O(\alpha_s) correction to the top quark width

Generalized Gluon Currents and Applications in QCD

We consider the process containing two quark lines and an arbitrary number of gluons in a spinor helicity framework. A current with two off-shell gluons appears in the amplitude. We first study this modified gluon current using recursion relations. The recursion relation for the modified gluon current is solved for the case of like-helicity gluons. We apply the modified gluon current to compute the amplitude for $q \bar q \rightarrow q \bar q gg \cdots g$ in the like-helicity gluon case.Comment: 80 pages, 2 figures (appended in pictex), CLNS 91/112

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)