Search

QED radiative corrections to elastic electron-proton scattering at low energies are discussed. Corrections to the electron line and effects due to vacuum polarization are computed. Higher order effects are estimated for the conditions of the experiment on the electric and magnetic proton form factors by A1 Collaboration. Calculations are performed within the next-to-leading approximation. Inclusion of the higher order effects can affect the value of the proton charge radius extracted from the experimental data., Comment: 6 pages, 3 figures

Radiatively induced symmetry breaking is considered for a toy model with one scalar and one fermion field unified in a superfield. It is shown that the classical quartic self-interaction of the superfield possesses a quantum infrared singularity. Application of the Coleman-Weinberg mechanism for effective potential leads to the appearance of condensates and masses for both scalar and fermion components. That induces a spontaneous breaking of the initial classical symmetries: the supersymmetry and the conformal one. The energy scales for the scalar and fermion condensates appear to be of the same order, while the renormalization scale is many orders of magnitude higher. A possibility to relate the considered toy model to conformal symmetry breaking in the Standard Model is discussed., Comment: Improved final version with new references and misprints corrected, 9 pages , no figures

New model is suggested, where the Casimir mechanism is the source of masses and conformal symmetry breaking at the Planck epoch in the beginning of the Universe. The mechanism is the Casimir energy and associated condensate, which are resulted from the vacuum postulate and normal ordering of the conformal invariant Hamiltonian with respect to the quantum elementary field operators. It is shown that the Casimir top-quark condensate specifies the value of the Higgs particle mass without involving the Higgs tachyon mass, which is put equal to zero. The Casimir mechanism yields another value of the coupling constant for the self-interaction of scalar field than the standard model does., Comment: 5 pages, no figures, to be published in proceedings of the XXII International Baldin Seminar on High Energy Physics Problems "Relativistic Nuclear Physics and Quantum Chromodynamics", Dubna, Russina, September 15-20, 2014

A mechanism of radiatively induced breaking of the conformal symmetry in the Standard Model is suggested. The system of one scalar (Higgs) and one fermion (top-quark) fields with Yukawa and $\phi^4$ interactions is considered. The infrared instability of the Coleman-Weinberg effective potential for this system leads to the appearance of a finite renormalization scale and thus to breaking of the conformal symmetry. Finite condensates of both scalar and spinor fields appear. It is shown that the top quark condensate can supersede the tachyon mass of the Higgs field. The Higgs boson is treated as an elementary scalar and the standard mechanism of electroweak symmetry breaking remains unchanged. The difference from the Standard Model appears in the value of the Higgs boson self-coupling constant., Comment: 6 pages, Based on the talk presented by A.B. Arbuzov at QUARKS-2014, Suzdal, Russia, 2-8 June, 2014

The problem of the description of two interacting particles is considered. It is shown that it can be reduced to the description of one particle in an external static potential even in a relativistic case. The method is based on the Maupertuis least action principle. The proposed method is verified for known problems in two-particle problems in classical mechanics, as well as in non-relativistic and relativistic quantum mechanics., Comment: 9 pages

Interaction of charged leptons with photons is considered for the case when one of the lepton legs is off the mass shell. The effect due to off-mass-shell shift in the anomalous magnetic moment is computed within one-loop approximation. Possible contributions of this effect in the muon $g-2$ measurements are discussed., Comment: 5 pages

Process of electron-positron annihilation into $\eta(\eta')2\pi$ is described within the extended NJL model in the energy range up to about 2 GeV. Contributions of intermediate vector mesons $\rho(770)$ and $\rho(1450)$ are taken into account. Results for the $\eta2\pi$ channel are found to be in a reasonable agreement with experimental data. Predictions for production of $\eta' 2\pi$ are given. The corresponding estimations for decays $\tau\to\eta(\eta')2\pi\nu$ are given in Appendix., Comment: Estimations for decays $\tau\to\eta(\eta')2\pi\nu$ widths are added

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., Comment: 1+28 pages, 20 figures

A mechanism of spontaneous conformal symmetry breaking based on field condensates in the Standard Model of strong and electroweak interactions is suggested. It is shown that an existence of the top quark condensate can supersede the tachyon mass term in the Higgs potential in the standard mechanism of electroweak symmetry breaking. Considering the ratio of a field condensate to the corresponding mass power (depending on quantum statistics) for various fields as a conformal invariant, we obtain the Higgs boson mass to be about $130\pm 15$ GeV., Comment: 4 pages, updated version submitted to Phys. Rev. D

The decay width $\tau\to\pi\omega\nu$ in the framework of the extended NJL model is calculated. The contributions of the intermediate vector mesons $\rho(770)$ and $\rho'(1450)$ are taken into account. The computed partial width and the spectral function of the decay $\tau\to\pi\omega\nu$ are in satisfactory agreement with experimental data., Comment: 5 pages

The Sommerfeld-Gamow-Sakharov factor is considered for the general case of arbitrary masses and energies. It is shown that the scalar triangular one-loop diagram gives the Coulomb singularity in radiative corrections at the threshold. The singular part of the correction is factorized at the complete Born cross section regardless of its partial wave decomposition. Different approaches to generalize the factor are discussed., Comment: 9 pages, 4 figures; references and discussion are extended

The Hamiltonian approach to the General Relativity is formulated as a joint nonlinear realization of conformal and affine symmetries by means of the Dirac scalar dilaton and the Maurer-Cartan forms. The dominance of the Casimir vacuum energy of physical fields provides a good description of the type Ia supernova luminosity distance--redshift relation. Introducing the uncertainty principle at the Planck's epoch within our model, we obtain the hierarchy of the Universe energy scales, which is supported by the observational data. We found that the invariance of the Maurer-Cartan forms with respect to the general coordinate transformation yields a single-component strong gravitational waves. The Hamiltonian dynamics of the model describes the effect of an intensive vacuum creation of gravitons and the minimal coupling scalar (Higgs) bosons in the Early Universe., Comment: 37 pages, version submitted to Gen. Rel. Grav

Electromagnetic interactions of the ground and first radial excited states of $\eta$ and $\eta'$ 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 $\eta$ and $\eta'$ meson are found to be in a satisfactory agreement with the experiment. Predictions for the two-photon decay widths of $\eta(1295)$ and $\eta(1475)$ are given. The probabilities of eta meson production by two-photon mechanism in $e^+e^-$ collisions and of their photoproduction on electrons are calculated., Comment: 4 pages, discussion of results is extended

The processes of electron-positron annihilation into $\pi^0\gamma$ and into $\pi'(1300)\gamma$ are considered within the NJL model. Intermediate vector mesons $\rho^0$, $\omega$, $\rho'(1450)$, and $\omega'(1420)$ 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 $\pi^0\gamma$ production are in agreement with experimental data received in the energy region 600 -- 1020 MeV., Comment: 4 pages, 5 figures

The process of electron-positron annihilation into a pair of $\pi^0$ and $\omega$ mesons is considered in the framework of the SU(2)$\times$SU(2) Nambu--Jona-Lasinio model. Contributions of intermediate photons, $\rho(770)$ and $\rho'(1450)$ 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 $\rho'(1450)$ state. The contribution due to single photon and $\rho(770)$ exchange is in agreement with the vector meson dominance model. Numerical results are compared with experimental data., Comment: A mistake is corrected, results are updated; 5 pages

Radiative decays $\pi^0({\pi^0}')\to\gamma+\gamma$, ${\pi^0}'\to\rho^0(\omega)+\gamma$, ${\rho^0}'(\omega')\to\pi^0+\gamma$, and ${\rho^0}'(\omega')\to{\pi^0}'+\gamma$ 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 $\pi^0\to\gamma+\gamma$ and $\rho^0(\omega)\to\pi^0+\gamma$ 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., Comment: 6 pages, submitted to Phys. Lett. B

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., Comment: 9 pages, 1 figure, submitted to PLB

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., Comment: 6 pages, reported at HADRON STRUCTURE '07 International Conference, Modra-Harmonia, Slovakia, Sept. 3-7, 2007

The mechanism of particle mass generation in the Standard Model is discussed. It is shown that non-zero vacuum expectation value of a scalar field together with the proper symmetry of the Lagrangian allow a certain class of scalar field potentials providing generation of gauge boson and fermion masses and keeping the electroweak sector of the model unchanged. Applying the minimality principle and certain additional conditions one can reduce the number of free parameters in the model. Possible phenomenological consequences in the scalar sector for different choices of the potential are discussed., Comment: 7 pages, JHEP3.cls, no figures

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., Comment: version to appear in Yadernaya Fizika

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., Comment: 7 pages, 1 figure

The contribution of the sub-process $\gamma q \to q' l_1\bar{l}_2$ 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., Comment: 11 pages, 8 figures

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., Comment: 8 pages

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 $<\phi>$. 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 $\textsf{V}_{\rm Higgs}(<\phi>)=0$. 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., Comment: Extended version with a brief description of cosmological model; updated discussion of our prediction for the Higgs boson mass

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., Comment: 22 pages, electronic version of JINR preprint

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., Comment: 12 pages, 10 Figures, elsart.cls

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., Comment: 60 pages, latex, 3 tables

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., Comment: LaTeX, 23 pages with 18 figures

Radiative corrections to neutrino deep inelastic scattering are revisited. One-loop electroweak corrections are re-calculated within the automatic SANC system. Terms with mass singularities are treated including higher order leading logarithmic corrections. Scheme dependence of corrections due to weak interactions is investigated. The results are implemented into the data analysis of the NOMAD experiment. The present theoretical accuracy in description of the process is discussed., Comment: 19 pages, two figures are added, discussion of theoretical uncertainties is extended

One-loop QED corrections to the differential width of radiative muon decay are considered. Results can be used to analyze high statistics data of modern and future experiments., Comment: 16 pp, 3 PostScript figures

A method to determine the running of alpha from a measurement of small-angle Bhabha scattering is proposed and worked out. The method is suited to high statistics experiments at e+e- colliders, which are equipped with luminometers in the appropriate angular region. A new simulation code predicting small-angle Bhabha scattering is also presented, Comment: 15 pages, 3 Postscript figures

The lowest order radiative correction to the differential cross-section of process of muon pair production with emission of hard photon at high energy electron-positron annihilation are calculated. Taking into account the emission of additional soft and hard photon the cross-section can be put in the form of Drell-Yan process in leading logarithmical approximation. Applying the crossing transformation we obtain the cross section of radiative electron-muon high-energy scattering process. Virtual and soft photon emission contributions of non-leading form are tabulated for several typical kinematical points. The limit of small invariant mass of muon pair is in agreement with our previous analysis., Comment: 9 pages, 2 figures

The process of the muon (pion) pair production with small invariant mass in the electron--positron high--energy annihilation, accompanied by emission of hard photon at large angles, is considered. We find that the Drell--Yan picture for differential cross section is valid in the charge--even experimental set--up. Radiative corrections both for electron block and for final state block are taken into account., Comment: 14 pages, 2 figures

The updated results of the precise measurements of the processes e+e-->rho->pi+pi-, e+e-->omega->pi+pi-pi0 and e+e-->phi->KLKS performed by the CMD-2 collaboration are presented. The update appeared necessary due an overestimate of the integrated luminosity in previous analyses., Comment: 8 pages, 1 figure

An analytical approach to convolution of functions, which appear in perturbative calculations, is discussed. An extended list of integrals is presented., Comment: 13 pages

Process of muon (pion) pair production with small invariant mass in the electron-positron high-energy annihilation, accompanied by emission of hard photon at large angles, is considered. We find that the Dell-Yan picture for differential cross section is valid in the charge-even experimental set-up. Radiative corrections both for electron block and for final state block are taken into account., Comment: 13 pages, 1 figure

Radiative corrections to the muon decay spectrum due to soft and virtual electron--positron pairs are calculated., Comment: 10pp, 2 PS figs, details of calculations are added