Related papers: Production Cross-sections for Unstable Particles
Unstable particles cannot be treated as asymptotic external states in $S$-matrix theory and when they occur as resonant states cannot be described by finite-order perturbation theory. The known facts concerning unstable particles are…
It is shown how to construct exactly gauge-invariant S-matrix elements for processes involving unstable gauge particles such as the $W$ and $Z^0$ bosons. The results are applied to derive a physically meaningful expression for the…
We address the problem that the cross section for the collisions of unstable particles diverges, if calculated by standard methods. This problem is considered for beams much smaller than the decay length of the unstable particle, much…
We consider pair production and decay of fundamental unstable particles in the framework of a modified perturbation theory (MPT), which treats resonant contributions of unstable particles in the sense of distributions. The cross-sections…
We illustrate the use of effective theory methods to describe resonant unstable particles. We outline the necessary ingredients to describe $W$-pair production close to threshold in $e^-e^+$ collisions.
In this work, we study the analytic properties of S-matrix for unstable particles, which is defined as the residues on the unphysical sheets where unstable poles reside. We demonstrate that anomalous thresholds associated with UV physics…
We consider pair production and decay of fundamental unstable particles in the framework of a modified perturbation theory (MPT), which treats resonant contributions of unstable particles in the sense of distributions. The cross-section of…
Unstable particles are notorious in perturbative quantum field theory for producing singular propagators in scattering amplitudes that require regularization by the finite width. In this review I discuss the construction of an effective…
We present a general formalism for the calculation of finite-width contributions to the differential production cross sections of unstable particles at hadron colliders. In this formalism, which employs an effective-theory description of…
We are exploring a generic strongly-interacting Electroweak Symmetry Breaking Sector (EWSBS) with the low-energy effectie field theory for the four experimentally known particles ($W_L^\pm$, $Z_L$, $h$) and its dispersion-relation based…
Quantum field model of unstable particles with random mass is suggested to describe the finite-width effects in decay rate. Within the framework of this model we derive the convolution formula for a width of the channels with unstable…
The top quark pair production and decay are considered in the framework of the smeared-mass unstable particles model. The results for total and differential cross sections in vicinity of $t\bar{t}$ threshold are in good agreement with the…
There exists the possibility that the cross-section for the nonperturbative production of many, ${\cal O}(\alpha_W^{-1} \simeq 30 )$, weak gauge bosons may be as large as ${\cal O}(100\ {\rm pb}\ -\ 10\ \mu$b$)$ above a parton-parton…
Near-threshold production of charged boson pairs is considered within the framework of the model of unstable particles with smeared mass. The results of calculations are in good agreement with LEP II data and Monte-Carlo simulations.…
We explore physics of unstable particles when mother particle mass is around the sum of its daughter particle masses. In this case, the conventional wave function renormalization factor is ill-defined. We propose a simple resolution of the…
We report measurements of the charge-separated $W^{+(-)} \to e^{+(-)} + \nu_e(\bar{\nu}_e)$ and $Z/\gamma^* \to e^+e^-$ production cross sections at mid-rapidity in proton-proton collisions at $\sqrt{s}$ = 500 GeV. These results are based…
We examine capabilities of the modified perturbation theory (MPT) for description of the processes with productions and decays of fundamental unstable particles. We calculate total cross-section for $e^{+} e^{-} \to \gamma,Z \to W^{+} W^{-}…
Near-threshold production of boson pairs is considered within the framework of the model of unstable particles with smeared mass. We describe the principal aspects of the model and consider the strategy of calculations including the…
In this talk, I review the effective theory approach to unstable particle production and present results of a calculation of the process e- e+ ->mu- nubar_mu u dbar X near the W-pair production threshold up to next-to-leading order in…
Perturbative calculations with unstable particles require the inclusion of their finite decay widths. A convenient, universal scheme for this purpose is the complex-mass scheme. It fully respects gauge-invariance, is straight-forward to…