scholarly journals Electroweak one-loop corrections to the process of fermion pair production in electron-positron annihilation

2019 ◽  
pp. 31-40
Author(s):  
Uladzimir U. Khasianevich ◽  
Tatiana V. Shishkina
Keyword(s):  
Radiation Energy ◽  
Phase Region ◽  
Polarization Asymmetry ◽  
Final State ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
Unpolarized Case ◽  
Loop Approximation ◽  
The One ◽  
Threshold Energies

Numerical results for the total cross section, polarization asymmetry, as well as forward-backward asymmetry are presented. Calculations were carried out for longitudinal polarization of the initial electron-positron beams, as well as for the unpolarized case in the one-loop approximation for the standard electroweak Glashow – Weinberg – Salam model without considering quark fields. As a renormalization scheme, we used a non-minimal on-shell scheme with simultaneous renorma lization of the fields. In addition to considering the radiation of soft photons, numerical analysis of hard bremsstrahlung was performed. Analysis of the effect of the cut-off parameters of the phase region of the three-particle final state was made, which are the acollinearity angle between the final leptons, the detecting threshold energies of the final particles, and the radiation energy of the soft photons. An algorithm for obtaining ultraviolet convergent expressions is described. The calculations were carried out in the formalism of the Passarino – Veltman functions in the light-lepton approximation.

Forward–backward asymmetry in electron–positron annihilation into pion or kaon pairs revisited

2020 ◽  
Vol 35 (25) ◽  
pp. 2050210
Author(s):  
Andrej B. Arbuzov ◽  
Tatiana V. Kopylova ◽  
Gulnazym A. Seilkhanova
Keyword(s):  
Positron Annihilation ◽  
Charge Asymmetry ◽  
Experimental Studies ◽  
Photon Exchange ◽  
Electron Positron Annihilation ◽  
Pseudoscalar Mesons ◽  
Electron Positron ◽  
Loop Approximation ◽  
The One ◽  
Exact Dependence

Forward–backward (charge) asymmetry in the processes of [Formula: see text] annihilation into a pair of charged pseudoscalar mesons is recalculated in the one-loop approximation. The exact dependence on the meson masses is taken into account. Results known in the literature are partially corrected. The bulk of the charge asymmetry appears due to double-photon exchange in [Formula: see text] channel. Experimental studies of the asymmetry can be used to verify the point-like approximation used in calculation of radiative corrections due to emission of photons by pions or kaons.

e+e- HADRON PRODUCTION CROSS SECTIONS AT BELLE

2014 ◽  
Vol 35 ◽  
pp. 1460407
Author(s):  
JASON D. CRNKOVIC ◽  
Keyword(s):  
Cross Sections ◽  
Solid Angle ◽  
Standard Model Prediction ◽  
Production Cross ◽  
General Purpose ◽  
Final State ◽  
Belle Detector ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
The Standard Model

A number of production cross sections for electron-positron annihilation to a hadronic final state have been measured using the Belle dataset, which is possible given the general purpose design of the Belle detector and its large solid-angle coverage. The cross section measurements predominantly fall above 3 GeV, which still leaves the opportunity for using the dataset to systematically measure cross sections below 3 GeV. These low-energy cross sections are important for improving the precision of the Standard Model prediction for the muon anomalous magnetic moment.

scholarly journals ELECTRON–POSITRON ANNIHILATION INTO DIRAC MAGNETIC MONOPOLE AND ANTIMONOPOLE: THE STRING AMBIGUITY AND THE DISCRETE SYMMETRIES

1998 ◽  
Vol 13 (28) ◽  
pp. 2295-2304 ◽  
Author(s):  
A. YU. IGNATIEV ◽  
G. C. JOSHI
Keyword(s):  
Field Theory ◽  
Positron Annihilation ◽  
Discrete Symmetries ◽  
Magnetic Monopole ◽  
Magnetic Monopoles ◽  
P Wave ◽  
Quantum Field ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
The One

We address the problem of string arbitrariness in the quantum field theory of Dirac magnetic monopoles. Different prescriptions are shown to yield different physical results. The constraints due to the discrete symmetries (C and P) are derived for the process of electron–positron annihilation into the monopole–antimonopole pair. In the case of the annihilation through the one-photon channel, the production of spin-0 monopoles is absolutely forbidden; spin-1/2 monopole and antimonopole should have the same helicities (or, equivalently, the monopole–antimonopole state should be p-wave 1P1).

scholarly journals Final-state radiation in electron-positron annihilation into a pion pair

2005 ◽  
Vol 40 (1) ◽  
pp. 41-54 ◽  
Author(s):  
S. Dubinsky ◽  
A. Korchin ◽  
N. Merenkov ◽  
G. Pancheri ◽  
O. Shekhovtsova
Keyword(s):  
Positron Annihilation ◽  
Pion Pair ◽  
Final State ◽  
Final State Radiation ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
State Radiation

scholarly journals Locally finite two-loop amplitudes for off-shell multi-photon production in electron-positron annihilation

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Charalampos Anastasiou ◽  
Rayan Haindl ◽  
George Sterman ◽  
Zhou Yang ◽  
Mao Zeng
Keyword(s):  
Gauge Theory ◽  
Positron Annihilation ◽  
Simple Manner ◽  
Locally Finite ◽  
Four Dimensions ◽  
Self Energy ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
Loop Amplitude ◽  
The One

Abstract We study the singularity structure of two-loop QED amplitudes for the production of multiple off-shell photons in massless electron-positron annihilation and develop counterterms that remove their infrared and ultraviolet divergences point by point in the loop integrand. The remainders of the subtraction are integrable in four dimensions and can be computed in the future with numerical integration. The counterterms capture the divergences of the amplitudes and factorize in terms of the Born amplitude and the finite remainder of the one-loop amplitude. They consist of simple one- and two-loop integrals with at most three external momenta and can be integrated analytically in a simple manner with established methods. We uncover novel aspects of fully local IR factorization, where vertex and self energy subdiagrams must be modified by new symmetrizations over loop momenta, in order to expose their tree-like tensor structures and hence factorization of IR singularities prior to loop integration. This work is a first step towards isolating locally the hard contributions of generic gauge theory amplitudes and rendering them integrable in exactly four dimensions with numerical methods.

AN IMPROVED ONE-LOOP ANALYSIS OF THE λϕ4 THEORY AT FINITE TEMPERATURE

1987 ◽  
Vol 02 (03) ◽  
pp. 713-728 ◽  
Author(s):  
SWEE-PING CHIA
Keyword(s):  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Zero Temperature ◽  
Coupling Constant ◽  
Loop Analysis ◽  
Temperature Dependent ◽  
Effective Coupling ◽  
Loop Approximation ◽  
The One ◽  
Dependent Mass

The λϕ4 theory with tachyonic mass is analyzed at T ≠ 0 using an improved one-loop approximation in which each of the bare propagators in the one-loop diagram is replaced by a dressed propagator to take into account the higher loop effects. The dressed propagator is characterized by a temperature-dependent mass which is determined by a self-consistent relation. Renomalization is found to be necessarily temperature-dependent. Real effective potential is obtained, giving rise to real effective mass and real coupling constant. For T < Tc, this is achieved by first shifting the ϕ field by its zero-temperature vacuum expectation value. The effective coupling constant is found to exhibit the striking behavior that it approaches a constant nonzero value as T → ∞.

THE NLO QCD CALCULATION OF SEA QUARK DISTRIBUTIONS IN THE CORGI APPROACH, BASED ON THE CONSTITUENT QUARK MODEL

2007 ◽  
Vol 22 (24) ◽  
pp. 4519-4535 ◽  
Author(s):  
A. MIRJALILI ◽  
K. KESHAVARZIAN
Keyword(s):  
Quark Model ◽  
Mellin Transform ◽  
Constituent Quark ◽  
Constituent Quark Model ◽  
Standard Approach ◽  
Unknown Parameters ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
Physical Scale ◽  
Good Agreement

Sea quark distributions in the NLO approximation, based on the phenomenological valon model or constituent quark model are analyzed. We use the parametrized inverse Mellin transform technique to perform a direct fit with available experimental data and obtain the unknown parameters of the distributions. We try to extend the calculation to the NLO approximation for the singlet and nonsinglet cases in DIS phenomena. We do also the same calculation for electron–positron annihilation. The resulting sea distributions are effectively independent of the process used. The approach of complete RG improvement (CORGI) is employed and the results are compared with the standard approach of perturbative QCD in the [Formula: see text] scheme with a physical scale. The comparisons with data are in good agreement. As is expected, the results in the CORGI approach indicate a better agreement to the data than the NLO calculation in the standard approach.

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