MONTE CARLO EVENT GENERATORS

Revised September 2013 by P. Nason （INFN, Milan） and P.Z. Skands （CERN） General-purpose Monte Carlo （GPMC） generators like HERWIG [1], HERWIG＋＋ [2], PYTHIA 6 [3], PYTHIA 8 [4], and SHERPA [5], provide fully exclusive simulations of high-energy collisions. They play an essential role in QCD modeling （in particular for aspects beyond fixed-order perturbative QCD）, in data analysis,

MONTE CARLO NEUTRINO EVENT GENERATORS

Written September 2013 by H. Gallagher （Tufts U.） and Y. Hayato （Tokyo U.） Monte Carlo neutrino generators are programs or libraries which simulate neutrino interactions with electrons, nucleons and nuclei. In this capacity their usual task is to take an input neutrino and nucleus and produce a set of 4-vectors for particles emerging from the interaction, which are then input to full detector simulations.

News on PHOTOS Monte Carlo:γ~*→π^+π^-(γ) and K~±→π^+π^-e~±ν(γ)

PHOTOS Monte Carlo is widely used for simulating QED effects in decay of intermediate particles and resonances. It can be easily connected to other main process generators. In this paper we consider decaying processes γ＊→π^＋π^-（γ） and K^±→π^＋π^-e^±υ（γ） in the framework of Scalar QED. These two processes are interesting not only for the technical aspect of PHOTOS Monte Carlo, but also for precision measurement of αED（Mz）, g--2, as well as ππ scattering lengths.

Probing top-quark operators with precision electroweak measurements

In the standard model effective field theory,operators involving the top quark are generally difficult to probe and can generate sizable loop contributions to electroweak precision observables measured by past and future lepton colliders.Could the high precision of electroweak measurements compensate for loop suppression and provide competitive reaches on these operators?Would the inclusion of these contributions introduce too many additional parameters for a meaningful global electroweak analysis to be performed?In this paper,we perform a detailed phenomenological study to address these two important questions.Focusing on eight dimension-6 operators that generate anomalous couplings between electroweak gauge bosons and third-generation quarks,we calculate their one loop contributions to e^(+)e^(-)→ff processes,both on and off the Z-pole,and the e^(+)e^(-)→WW process.A global analysis is performed with these eight operators and those that contribute to the above processes at tree level using measurements at the LEP,SLC,and several low energy experiments.We find that although current electroweak precision measurements are sensitive to the one-loop effects of top-quark operators,it is difficult to separate them from the operators that contribute at tree level,making a global analysis rather challenging.Under further assumptions(for instance,new physics contributes to only third generation quark operators and the S and T parameters),competitive reaches may be obtained in a global fit.Another important finding of our study is that the two operators that generate the dipole interactions of the bottom quark have a significant impact on the Z-pole measurements and should not be omitted.We also discuss the implications of the recently reported W-boson mass measurement at the CDF for our results.Finally,we estimate the reaches of future lepton colliders in probing top-quark operators with precision electroweak measurements.

Strong and electromagnetic J/ψ and ψ(2S) decays into pion and kaon pairs

We discuss interference effects important for the form factors extraction in the vicinity of J/ψ and ψ（2S） resonances in combination with resonance parameters determination. The implementation to the Monte Carlo event generator PHOKHARA of the J/ψ and ψ（2S） contributions to the muon, pion and kaon pairs production associated with a photon at next-to-leading order is also described.