arXiv subjects

A. B. Arbuzov

Publications and source records attributed to A. B. Arbuzov.

At least 55 records · Page 3Linked to original sources

arXiv2012

QED Bremsstrahlung in decays of electroweak bosons

Isolated lepton momenta, in particular their directions are the most precisely measured quantities in pp collisions at LHC. This offers opportunities for multitude of precision measurements. It is of practical importance to verify if precision measurements with lep- tons in the final state require all theoretical effects evaluated simultaneously or if QED bremsstrahlung in the final state can be separated without unwanted precision loss. Results for final state bremsstrahlung in the decays of narrow resonances are obtained from the Feynman rules of QED in an unambiguous way and can be controlled with a very high precision. Also for resonances of non-negligible width, if calculations are appropriately performed, such separation from the remaining electroweak effects can be expected. Our paper is devoted to validation that final state QED bremsstrahlung can indeed be separated from the rest of QCD and electroweak effects, in the production and decay of Z and W bosons, and to estimation of the resulting systematic error. The quantitative discussion is based on Monte Carlo programs PHOTOS and SANC, as well as on KKMC which is used for benchmark results. We show, that for a large classes of W and Z boson observables as used at LHC, theoretical error on photonic bremsstrahlung is 0.1 or 0.2%, depending on the program options used. An overall theoretical error on QED final state radiation, i.e. taking into account missing corrections due to pair emission and interference with initial state radiation is estimated respectively at 0.2% or 0.3% again depending on the program option used.

hep-ph↗

arXiv2012

The decay $τ\to πων$ in the extended NJL model

The decay width $τ\toπων$ in the framework of the extended NJL model is calculated. The contributions of the intermediate vector mesons $ρ(770)$ and $ρ'(1450)$ are taken into account. The computed partial width and the spectral function of the decay $τ\toπων$ are in satisfactory agreement with experimental data.

hep-ph↗

arXiv2011

Two-photon decays and photoproduction on electrons of $η(550)$, $η'(958)$, $η(1295)$, and $η(1475)$ mesons

Electromagnetic interactions of the ground and first radial excited states of $η$ and $η'$ mesons in the framework of the extended $U(3)\times U(3)$ NJL model are considered. The radial excitations are described with the help of polynomial form factor of the second order over the inner quark momentum. The solution of the $U_A(1)$ problem by means of 't Hooft interaction is taken into account. For diagonalization of the free Lagrangian the $4\times4$ mixing matrix is used. Two-photon decay widths of the ground $η$ and $η'$ meson are found to be in a satisfactory agreement with the experiment. Predictions for the two-photon decay widths of $η(1295)$ and $η(1475)$ are given. The probabilities of eta meson production by two-photon mechanism in $e^+e^-$ collisions and of their photoproduction on electrons are calculated.

hep-ph↗

arXiv2011

Processes $e^+e^-\toπ^0({π^0}')γ$ in the NJL model

The processes of electron-positron annihilation into $π^0γ$ and into $π'(1300)γ$ are considered within the NJL model. Intermediate vector mesons $ρ^0$, $ω$, $ρ'(1450)$, and $ω'(1420)$ are taken into account. The latter two mesons are treated as the first radial excited states. They are incorporated into the NJL model by means of a polynomial form factor. Numerical predictions for the cross sections of these processes are received for the center-of-mass energies below 2 GeV. Our results for the $π^0γ$ production are in agreement with experimental data received in the energy region 600 -- 1020 MeV.

hep-ph↗

arXiv2011

Production of $ωπ^0$ pair in electron-positron annihilation

The process of electron-positron annihilation into a pair of $π^0$ and $ω$ mesons is considered in the framework of the SU(2)$\times$SU(2) Nambu--Jona-Lasinio model. Contributions of intermediate photons, $ρ(770)$ and $ρ'(1450)$ vector mesons are taken into account. It is shown that the bulk of the cross section at energies below 2 GeV is provided by the process with intermediate $ρ'(1450)$ state. The contribution due to single photon and $ρ(770)$ exchange is in agreement with the vector meson dominance model. Numerical results are compared with experimental data.

hep-ph↗

arXiv2010

Radiative decays of radially excited mesons ${π^0}'$, ${ρ^0}'$, $ω'$ in NJL model

Radiative decays $π^0({π^0}')\toγ+γ$, ${π^0}'\toρ^0(ω)+γ$, ${ρ^0}'(ω')\toπ^0+γ$, and ${ρ^0}'(ω')\to{π^0}'+γ$ are considered in the framework of the non-local SU(2)$\times$SU(2) NJL model. Radially excited mesons are described with the help of polynomial form factor $f({k^\bot}^2)$, where $k^\bot$ is the quark momentum transverse to the external meson momentum. In spite of mixing of the ground and excited meson states in this model, the decay widths of $π^0\toγ+γ$ and $ρ^0(ω)\toπ^0+γ$ are found to be in good agreement with experimental data as in the standard local NJL model. Our predictions for decay widths of radially excited mesons can be verified in future experiments.

hep-ph↗

arXiv2010

Conformal Hamiltonian Dynamics of General Relativity

The General Relativity formulated with the aid of the spin connection coefficients is considered in the finite space geometry of similarity with the Dirac scalar dilaton. We show that the redshift evolution of the General Relativity describes the vacuum creation of the matter in the empty Universe at the electroweak epoch and the dilaton vacuum energy plays a role of the dark energy.

gr-qc↗

arXiv2009

Is it possible to estimate the Higgs Mass from the CMB Power Spectrum?

General Relativity and Standard Model are considered as a theory of dynamical scale symmetry with definite initial data compatible with the accepted Higgs mechanism. In this theory the Early Universe behaves like a factory of electroweak bosons and Higgs scalars, and it gives a possibility to identify three peaks in the Cosmic Microwave Background power spectrum with the contributions of photonic decays and annihilation processes of primordial Higgs, W, and Z bosons in agreement with the QED coupling constant, Weinberg's angle, and Higgs' particle mass of about 118 GeV.

hep-ph↗

arXiv2008

Generating Functional for Bound States in QED

The manifestly Lorentz covariant formulation of quantum electrodynamics disregards Coulomb instantaneous interaction and its consequence - instantaneous bound states (IBS's). In this article we consider the way of construction the IBS generating functional using the operator generalization of the initial data in the Dirac Hamiltonian approach to QED.

hep-th↗

arXiv2008

Higgs Particle Mass in Cosmology

A version of the Standard Model is considered, where the electroweak symmetry breaking is provided by cosmological initial data given for the zeroth Fourier harmonic of the Higgs field $<ϕ>$. The initial data symmetry breaking mechanism removes the Higgs field contribution to the vacuum energy density, possible creation of monopoles, and tachion behavior at high energies, if one imposes an ``inertial'' condition on the Higgs potential $\textsf{V}_{\rm Higgs}(<ϕ>)=0$. The requirement of zero radiative corrections to this {\em inertial} condition coincides with the limiting point of the vacuum stability in the Standard Model. The latter together with the direct experimental limit gives the prediction for the mass of the Higgs boson to be in the range $114 < m_h \lsim 134$ GeV.

hep-ph↗

arXiv2007

Radiative Corrections to High Energy Lepton Bremsstrahlung on Heavy Nuclei

One-loop radiative corrections to the leptonic tensor in high energy bremsstrahlung on heavy nuclei are calculated. Virtual and real photon radiation is taken into account. Double bremsstrahlung is simulated by means of Monte Carlo. Numerical results are presented for the case of muon bremsstrahlung in conditions of the COMPASS experiment at CERN.

hep-ph↗

arXiv2007

Inverse bremsstrahlung contributions to Drell-Yan like processes

The contribution of the sub-process $γq \to q' l_1\bar{l}_2$ in hadron-hadron interactions is considered. It is a part of one-loop electroweak radiative corrections for the Drell-Yan production of lepton pairs at hadron colliders. It is shown that this contribution should be taken into account aiming at the 1% accuracy of the Drell-Yan process theoretical description. Both the neutral and charged current cases are evaluated. Numerical results are presented for typical conditions of LHC experiments.

hep-ph↗

arXiv2007

QED collinear radiation factors in the next-to-leading logarithmic approximation

The effect of the collinear photon radiation by charged particles is considered in the second order of the perturbation theory. Double and single photon radiation is evaluated. The corresponding radiation factors are obtained. The QED renormalization group approach is exploited in the next-to-leading order. The results are suited to perform a systematic treatment of the second order next-to-leading logarithmic radiative corrections to various processes either analytically or numerically.

hep-ph↗

arXiv2007

Table of integrals. Asymptotical expressions for non--collinear kinematics

We present a set of Feynman integrals appearing in calculations of different QED processes to the one-loop accuracy. We consider scalar, vector, and tensor integrals with two, three, four and five denominators. The cases of equal and different fermion masses are considered. Results obtained are valid in the region where all kinematical invariants are large compared to the masses squared. Mass corrections for some scalar integrals in the case of different fermion masses are also given.

hep-ph↗

arXiv2006

Next-to-leading order corrections to Bhabha scattering in renormalization group approach (I). Soft and virtual photonic contributions

Soft and virtual loop photonic contributions to the second order next-to-leading QED radiative corrections to Bhabha scattering are calculated with help of the renormalization group approach. The results are in agreement with earlier calculations, where other methods were used. Scale dependence and the present theoretical accuracy of Bhabha cross section description are discussed.

hep-ph↗

arXiv2005

ZFITTER: a semi-analytical program for fermion pair production in e+e- annihilation, from version 6.21 to version 6.42

ZFITTER is a Fortran program for the calculation of fermion pair production and radiative corrections at high energy e+e- colliders; it is also suitable for other applications where electroweak radiative corrections appear. ZFITTER is based on a semi-analytical approach to the calculation of radiative corrections in the Standard Model. We present a summary of new features of the ZFITTER program version 6.42 compared to version 6.21. The most important additions are: (i) some higher-order QED corrections to fermion pair production, (ii) electroweak one-loop corrections to atomic parity violation, (iii) electroweak one-loop corrections to nu-e nu-e-bar production, (iv) electroweak two-loop corrections to the W boson mass and the effective weak mixing angle.

hep-ph↗

arXiv2005

Higher order pair corrections to electron-positron annihilation

Radiative corrections due to pair production in process of electron-positron annihilation are considered. The main attention is paid to the corrections of the third order. Simultaneous emission of photons and pairs is taken into account. The leading log approximation and convolution procedure are used. Exponentiation is discussed. Theoretical uncertainty in description of higher order secondary pairs is estimated.

hep-ph↗

arXiv2005

Monte-Carlo generator for e+e- annihilation into lepton and hadron pairs with precise radiative corrections

Recently, various cross sections of e+e- annihilation into hadrons were accurately measured in the energy range from 0.37 to 1.39 GeV with the CMD-2 detector at the VEPP-2M collider. In the pi+pi- channel a systematic uncertainty of 0.6% has been achieved. A Monte-Carlo Generator Photon Jets (MCGPJ) was developed to simulate events of the Bhabha scattering as well as production of two charged pions, kaons and muons. Based on the formalism of Structure Functions, the leading logarithmic contributions related to the emission of photon jets in the collinear region are incorporated into the MC generator. Radiative corrections (RC) in the first order of alpha are accounted for exactly. The theoretical precision of the cross sections with RC is estimated to be better than 0.2%. Numerous tests of the program as well as comparison with other MC generators and CMD-2 experimental data are presented.

hep-ph↗