Z. Was

Global positioning of spin GPS scheme for half-spin massive spinors

Abstract. We present a simple and flexible method of keeping track of the complex phases and spin quantisation axes for half-spin initial- and final-state Weyl spinors in scattering amplitudes of Standard Model high energy physics processes. Both cases of massless and massive spinors are discussed. The method is demonstrated and checked numerically for spin correlations in

Electric charge screening effect in single-W production with the KoralW Monte Carlo

\tau \bar\tau

Library of SM and anomalous W W gamma couplings for the e+ e- ---> f anti-f n gamma Monte Carlo programs

production and decay. Its application is in our work of combining effects due to multiple photon emission (exponentiation) and spin, embodied in the Monte Carlo event generators for production and decay of unstable fermions such as the

CP violation in B0_d --> tau+ tau- decays

\tau

CP violation in B0(d) ---> tau+ tau- decays

lepton, t-quark and hypothetical new heavy particles. In particular, the recurrent problem of combining, for such unstable fermions, one authors calculation of production and another authors calculation of decay, in the presence or absence of multiple photon effects, is there given a practical solution, both for Weyl spinor methods and for the traditional Jacob-Wick helicity methods. Moreover, for massive fermions we give a simple representation of the amplitude for

TauSpinner program for studies on spin effect in tau production at the LHC

n(\gamma)

Bremsstrahlung simulation in K → πl ± ν l ( γ ) decays

emission ideally suited for numerical evaluation. No other method is known to us which for arbitrary n has been realized numerically for unstable, massive fermions. Our paper can contribute also, to the discussion on design principles of the phenomenology work for the future accelerators such as LHC or NLC.

Higher-order QED corrections to \(e^ + e^ - \to v\bar v\gamma \) at LEP2

Abstract. Any Monte Carlo event generator in which only initial state radiation (ISR) is implemented, or ISR is simulated independently of the final state radiation (FSR), may feature too many photons with large transverse momenta, which deform the topology of events and result in too strong an overall energy loss due to ISR. This overproduction of ISR photons happens in the presence of the final state particle close to the beam particle of the same electric charge. It is often said that the lack of the electric charge screening effect between ISR and FSR is responsible for the above pathology in ISR. We present an elegant approximate method of curing the above problem, without actually reinstalling FSR. The method provides theoretical predictions of modest precision:

Higher-order QED corrections to e + e − → ν¯νγ at LEP2

\leq 2\%

Erratum to ``Library of SM and anomalous WWgamma couplings for the ee-->ff¯ngamma Monte Carlo programs'' [Comput. Phys. Commun. 124 (2000) 238]

. It is, however, sufficient for the current 1W data analysis at the LEP2 collider. Contrary to alternative methods implemented in other MC programs, our method works for the ISR multiphotons with finite