English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

The PHOTOS Monte Carlo is often used for simulation of QED effects in decayof intermediate particles and resonances. Momenta are generated in such a waythat samples of events cover the whole bremsstrahlung phase space. With thehelp of selection cuts, experimental acceptance can be then taken into account.The program is based on an exact multiphoton phase space. Crude matrix elementis obtained by iteration of a universal multidimensional kernel. It ensuresexact distribution in the soft photon region. Algorithm is compatible withexclusive exponentiation. To evaluate the program's precision, it is necessaryto control the kernel with the help of perturbative results. If available,kernel is constructed from the exact first order matrix element. This ensuresthat all terms necessary for non-leading logarithms are taken into account. Inthe present paper we will focus on the W -> l nu and gamma^* -> pi^+ pi^-decays. The Born level cross sections for both processes approach zero in somepoints of the phase space. A process dependent compensating weight isconstructed to incorporate the exact matrix element, but is recommended for usein tests only. In the hard photon region, where scalar QED is not expected tobe reliable, the compensating weight for gamma^* decay can be large. Withrespect to the total rate, the effect remains at the permille level. It isnonetheless of interest. The terms leading to the effect are analogous to someterms appearing in QCD. The present paper can be understood either as acontribution to discussion on how to match two collinear emission chainsresulting from charged sources in a way compatible with the exact and completephase space, exclusive exponentiation and the first order matrix element of QED(scalar QED), or as the practical study of predictions for acceleratorexperiments.

Matching NLO parton shower matrix element with exact phase space: case of W -> l nu (gamma) and gamma^* -> pi^+pi^-(gamma)