scholarly journals MODIFIED PERTURBATION THEORY FOR ANGULAR DISTRIBUTION IN W-PAIR PRODUCTION

2012 ◽  
Vol 27 (32) ◽  
pp. 1250195
Author(s):  
M. L. NEKRASOV
Keyword(s):  
Perturbation Theory ◽  
Angular Distribution ◽  
Pair Production ◽  
Production Angle ◽  
Exact Results ◽  
Unstable Particles

We examine the capabilities of the modified perturbation theory (MPT) for description of W-pair production and decay in e+ e- annihilation. In a model with Dyson-resummed propagators of unstable particles, we calculate even and odd contributions to the distribution in the cosine of the W- production angle relative to the e- beam. On comparing the results of calculations in the NNLO approximation of MPT with the exact results in the model, a coincidence of outcomes at the ILC energies is detected at the per-mille level.

scholarly journals W-PAIR PRODUCTION IN MODIFIED PERTURBATION THEORY

2011 ◽  
Vol 26 (24) ◽  
pp. 1807-1816 ◽  
Author(s):  
M. L. NEKRASOV
Keyword(s):  
Perturbation Theory ◽  
Total Cross Section ◽  
Pair Production ◽  
Cross Section ◽  
Unstable Particles ◽  
Better Than

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- → γ, Z → W+W- → 4f in a model with the Dyson-resummed and with the MPT-expanded up to the NNLO Breit–Wigner factors, and compare the outcomes. At the ILC energies a coincidence of the outcomes is detected with precision better than one per-mille.

scholarly journals PAIR PRODUCTION OF FUNDAMENTAL UNSTABLE PARTICLES IN MODIFIED PERTURBATION THEORY IN NNLO

2011 ◽  
Vol 26 (03) ◽  
pp. 223-234 ◽  
Author(s):  
M. L. NEKRASOV
Keyword(s):  
Exact Solution ◽  
Perturbation Theory ◽  
Pair Production ◽  
Cross Section ◽  
Massless Particles ◽  
Unstable Particles ◽  
The Cross

We consider pair production and decay of fundamental unstable particles in the framework of a modified perturbation theory (MPT) treating resonant contributions in the sense of distributions. The cross-section of the process is calculated within the NNLO of the MPT in a model that admits exact solution. Universal massless-particles contributions are taken into consideration. A comparison of the outcomes with the exact solution demonstrates excellent convergence of the MPT series at the energies near and above the maximum of the cross-section.

scholarly journals MODIFIED PERTURBATION THEORY FOR PAIR PRODUCTION AND DECAY OF FUNDAMENTAL UNSTABLE PARTICLES

2009 ◽  
Vol 24 (32) ◽  
pp. 6071-6103 ◽  
Author(s):  
M. L. NEKRASOV
Keyword(s):  
Perturbation Theory ◽  
Asymptotic Expansion ◽  
Pair Production ◽  
Asymptotic Property ◽  
Cross Section ◽  
Arbitrary Order ◽  
Threshold Region ◽  
Coupling Constant ◽  
Unstable Particles ◽  
Kinematic Singularities

We construct an asymptotic expansion in powers of the coupling constant directly of the cross-section for pair production and decay of fundamental unstable particles. The resonant and kinematic singularities arising in the expansion we treat in the sense of distributions. This mode allows us to transform formally divergent integrals into absolutely convergent ones with keeping the asymptotic property of the expansion. The appropriate procedure is elaborated up to an arbitrary order of the expansion. The peculiarity of application of the procedure in the threshold region is analyzed. The scheme of the calculations within the NNLO approximation is explicitly discussed.

scholarly journals Spurious poles in the scattering of electric and magnetic charges

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
John Terning ◽  
Christopher B. Verhaaren
Keyword(s):  
Perturbation Theory ◽  
Scattering Amplitudes ◽  
Pair Production ◽  
Magnetic Particles ◽  
Single Photon ◽  
Low Energy ◽  
Magnetic Interactions ◽  
Parity Conservation ◽  
Non Local ◽  
The Way

Abstract Theories with both electric and magnetic charges (“mutually non-local” theories) have several major obstacles to calculating scattering amplitudes. Even when the interaction arises through the kinetic mixing of two, otherwise independent, U(1)’s, so that all low-energy interactions are perturbative, difficulties remain: using a self-dual, local formalism leads to spurious poles at any finite order in perturbation theory. Correct calculations must show how the spurious poles cancel in observable scattering amplitudes. Consistency requires that one type of charge is confined as a result of one of the U(1)’s being broken. Here we show how the constraints of confinement and parity conservation on observable processes manages to cancel the spurious poles in scattering and pair production amplitudes, paving the way for systematic studies of the experimental signatures of “dark” electric-magnetic processes. Along the way we demonstrate some novel effects in electric-magnetic interactions, including that the amplitude for single photon production of magnetic particles by electric particles vanishes.

scholarly journals Lepton pair production in heavy-ion collisions in perturbation theory

2002 ◽  
Vol 66 (4) ◽  
Author(s):  
E. Bartoš ◽  
S. R. Gevorkyan ◽  
E. A. Kuraev ◽  
N. N. Nikolaev
Keyword(s):  
Perturbation Theory ◽  
Pair Production ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Lepton Pair ◽  
Lepton Pair Production ◽  
Ion Collisions

scholarly journals MASS SHELL SMEARING EFFECTS IN TOP PAIR PRODUCTION

2012 ◽  
Vol 27 (13) ◽  
pp. 1250072 ◽  
Author(s):  
V. I. KUKSA ◽  
R. S. PASECHNIK ◽  
D. E. VLASENKO
Keyword(s):  
Pair Production ◽  
Cross Sections ◽  
Top Quark ◽  
Preliminary Analysis ◽  
Mass Shell ◽  
Threshold Region ◽  
Suggested Approach ◽  
Unstable Particles ◽  
Higher Order Corrections ◽  
Good Agreement

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 [Formula: see text] threshold are in good agreement with the previous ones in the literature. The strategy of calculations of the higher order corrections in the framework of the model is discussed. Suggested approach significantly simplifies calculations compared to the standard perturbative one and can serve as a convenient tool for fast and precise preliminary analysis of processes involving intermediate timelike top quark exchanges in the near-threshold region.

scholarly journals TOP QUARK PAIR PRODUCTION AND DECAY INCLUDING SPIN EFFECTS AT HADRON COLLIDERS: PREDICTIONS AT NLO QCD

2003 ◽  
Vol 18 (08) ◽  
pp. 1357-1364 ◽  
Author(s):  
W. BERNREUTHER ◽  
A. BRANDENBURG ◽  
Z. G. SI ◽  
P. UWER
Keyword(s):  
Angular Distribution ◽  
Pair Production ◽  
Top Quark ◽  
Leading Order ◽  
Hadron Colliders ◽  
Tevatron Collider ◽  
Spin Effects ◽  
Quark Flavor ◽  
Future Data ◽  
Hadronic Production

Top quark-antiquark [Formula: see text] pairs will be produced copiously at the Tevatron collider and in huge numbers at the LHC. This will make possible detailed investigations of the properties and interactions of this quark flavor. The analysis and interpretation of future data requires precise predictions of the hadronic production of [Formula: see text] pairs and of their subsequent decays. In this talk the reactions [Formula: see text], [Formula: see text] are considered and results are presented of our calculation6 of the dilepton angular distribution at next-to-leading order QCD, keeping the full dependence on the spins of the intermediate [Formula: see text] state. The angular distribution is determined for different choices of reference axes that can be identified with the t and [Formula: see text] spin axes. While the QCD corrections to the leading-order distribution turn out to be small in the case of the LHC, we find them to be sizeable in the case of the Tevatron and find, moreover, the angular distribution to be sensitive to the parton content of the proton.

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