[show abstract][hide abstract] ABSTRACT: We present a simple formalism for the evolution of timelike jets in which
tree-level matrix element corrections can be systematically incorporated, up to
arbitrary parton multiplicities and over all of phase space, in a way that
exponentiates the matching corrections. The scheme is cast as a shower Markov
chain which generates one single unweighted event sample, that can be passed to
standard hadronization models. Remaining perturbative uncertainties are
estimated by providing several alternative weight sets for the same events, at
a relatively modest additional overhead. As an explicit example, we consider Z
-> q qbar evolution with unpolarized, massless quarks and include several
formally subleading improvements as well as matching to tree-level matrix
elements through alpha_s^4. The resulting algorithm is implemented in the
publicly available VINCIA plugin to the PYTHIA 8 event generator.
[show abstract][hide abstract] ABSTRACT: We present a simple formalism for parton-shower Markov chains. As a first step towards more complete “uncertainty bands,” we incorporate a comprehensive exploration of the ambiguities inherent in such calculations. To reduce this uncertainty, we then introduce a matching formalism which allows a generated event sample to simultaneously reproduce any infrared-safe distribution calculated at leading or next-to-leading order in perturbation theory, up to subleading corrections. To enable a more universal definition of perturbative calculations, we also propose a more general definition of the hadronization cutoff. Finally, we present an implementation of some of these ideas for final-state gluon showers, in a code dubbed Vincia.
Physical review D: Particles and fields 07/2008; 78(1).
[show abstract][hide abstract] ABSTRACT: This report summarizes the activity on comparisons of existings tools for the standard model and on issues in jet physics by the SMHC working group during and subsequent to the Workshop "Physics at TeV Colliders", Les Houches, France, 11-29 June, 2007.
[show abstract][hide abstract] ABSTRACT: In order to establish supersymmetry (SUSY) at future colliders, the identity of gauge couplings and the corresponding Yukawa
couplings between gauginos, sfermions and fermions needs to be verified. A first phenomenological study for determining the
Yukawa coupling of the SUSY-QCD sector is presented here, using a method which combines information from LHC and ILC.
[show abstract][hide abstract] ABSTRACT: In order to establish supersymmetry at future colliders, it is not sufficient to discover new particles, but the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions needs to be verified. In detailed studies it was found that the SUSY-Yukawa couplings of the electroweak sector can be studied with great precision at the ILC, but a similar analysis for the Yukawa coupling of the SUSY-QCD sector proves to be far more challenging. Here a first phenomenological study for determining this coupling is presented, using a method which combines information from LHC and ILC.