Searcharxiv⌕ Search

arXiv subjects

E. A. Kuraev

Publications and source records attributed to E. A. Kuraev.

At least 55 records · Page 3Linked to original sources

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↗

Radiative proton-antiproton annihilation to a lepton pair

The annihilation of proton and antiproton to electron-positron pair, including radiative corrections due to the emission of virtual and real photons is considered. The results are generalized to leading and next-to leading approximations. The relevant distributions are derived and numerical applications are given in the kinematical range accessible to the PANDA experiment at the FAIR facility.

hep-ph↗

Radiative corrections to the spectra of heavy particles annihilation into leptons: Dark matter implementation

We calculate the radiative corrections to the annihilation of the Dark Matter particles into leptons. Lepton masses are taken into account. As the Dark Matter particles are considered both Dirac and Majorana fermions. We sum up all the leading logarithms contributions where it is possible. We show that in the Dirac fermion case the resulting cross-section is consistent with the renormalization group prediction: the cross-section have the Drell-Yan form. Whereas, in the Majorana fermions case we have two essentially different limits of the resulting cross-section and quantitively the answer strongly depends on a spectrum of the masses entering the problem.

hep-ph↗

Contributions of semi-hadronic states $Pγ;Sγ, π^+π^-γ$ to amm of muon, in frames of Nambu-Jona-Lasinio model

We calculate the contribution of semi-hadronic states with pseudoscalar $P=π^0, η$ and scalar ($σ$(550))meson accompanied with real photon as an intermediate state of a heavy photon to the anomalous magnetic moment of muon. We consider the intermediate states with $π_0$ and $σ$ as a hadrons in frames of Nambu-Jona-Lasinio model. The contribution of $π_0γ$ state is in agreement with results obtained in previous theoretical considerations as well as with experimental data $a_μ^{π_0γ}\approx 4.5 \times 10^{-10}$, besides we estimate $a_μ^{ηγ}=0.7 \times 10^{-10}, a_μ^{σγ} \sim 1.5 \times 10^{-11}, a_μ^{π^+π^-γ} \sim 3.2 \times 10^{-10}.$ We discass as well the LbL mechanism with $a_μ^{lbl}=10.5 \cdot 10^{-10}.$

hep-ph↗

Charge-odd correlation of lepton and pion pair production in electron-proton scattering

Charge-odd correlation of the charged pair components produced at electron-proton scattering can measure three current correlation averaged by proton state. In general these type correlation can be described by 14 structure functions. We restrict here by consideration of inclusive distributions of a pair components, which is the light-cone projection of the relevant hadronic tensor. Besides we consider the point-like approximation for proton and pion. Numerical estimations show that charge-odd effects can be measured in exclusive ep -> 2 pi X experiments.

hep-ph↗

Quest for precision in hadronic cross sections at low energy: Monte Carlo tools vs. experimental data

We present the achievements of the last years of the experimental and theoretical groups working on hadronic cross section measurements at the low energy e+e- colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on tau decays. We sketch the prospects in these fields for the years to come. We emphasise the status and the precision of the Monte Carlo generators used to analyse the hadronic cross section measurements obtained as well with energy scans as with radiative return, to determine luminosities and tau decays. The radiative corrections fully or approximately implemented in the various codes and the contribution of the vacuum polarisation are discussed.

hep-ph↗

Bremsstrahlung and pair production processes at low energies, multi-differential cross section and polarization phenomena

Radiative electron-proton scattering is studied in peripheral kinematics, where the scattered electron and photon move close to the direction of the initial electron. Even in the case of unpolarized initial electron the photon may have a definite polarization. The differential cross sections with longitudinally or transversal polarized initial electron are calculated. The same phenomena are considered for the production of an electron-positron pair by the photon, where the final positron (electron) can be also polarized. Differential distributions for the case of polarized initial photon are given. Both cases of unscreened and completely screened atomic targets are considered.

hep-ph↗

Radiative corrections in $K_{e4}$ decay

The final state interaction of pions in the decay $K^\pm\to π^+π^-e^\pmν$ allows to obtain the value of the isospin and angular momentum zero pion-pion scattering length $a_0^0$. To extract this quantity from experimental data the radiative corrections (RC) have to be taken into account. Basing on the lowest order results and the factorization hypothesis, we get the expressions for RC in the leading and next-to leading logarithmical approximation. It is shown that the decay width dependence on the lepton mass $m_e$ through the parameter $σ=\fracα{2π}\br{\ln\frac{M^2}{m_e^2}-1}$ has a standard form of the Drell-Yan process and is proportional to the Sommerfeld-Sakharov factor. The numerical estimations are presented.

hep-ph↗

Scalar meson production in proton-proton and proton-antiproton collisions

Taking into account the exchange forces between protons of scalar, pseudoscalar, vector and axial vector type the cross sections of neutral and charged scalar mesons $a_0(980)$, $a_+(980)$, $f_0(980)$, $σ(600)$ production are calculated. The estimation for the facilities of moderately high energies such as PANDA and NICA are presented. Similar analysis is given for processes of charged and neutral Higgs boson production at high energy proton-proton colliders such as Tevatron, RHIC and LHC. The possible signal of neutral Higgs boson decay into two oppositely charged leptons of different kinds is discussed. Numerical estimations for parameters of modern colliders are given.

hep-ph↗

Measuring the deviation from the Rutherford formula

Modern experiments with heavy ion-leptons collisions open the possibility to measure the deviation of cross section of small angles electron(positron)-ion elastic scattering from the Rutherford formula due to multiple virtual photons exchange. The charge asymmetry and the polarization of the scattered leptons are calculated and numerical predictions are given. A generalization to elastic proton-nucleus scattering is discussed.

hep-ph↗

Two-photon mechanism of production of scalar mesons at colliders

The cross sections of the scalar meson $f_0(980)$, $a_0(980)$ and $σ(600)$ production in collision of electron and positron beams were calculated. The two-photon decays of the scalar mesons, obtained in the framework of the Nambu-Jona-Lasinio model, were used. The quark and meson loops were taken into account.

hep-ph↗

Radiative decays of scalar mesons σ(600), f_0(980) and a_0(980) in the local Nambu-Jona-Lasinio model

The two-photon decay widths of scalar mesons σ(600), f_0(980) and a_0(980) as well a_0 -> ρ(ω)γand f_0 -> ρ(ω)γare calculated in the framework of the local Nambu-Jona-Lasinio model. The contributions of the quark loops (Hartree-Fock approximation) and the meson loops (next 1/Nc -approximation where Nc is the number of colors) are taken into account. These contributions, as we show, are the values of the same order of magnitude. For the f_0 decay the K-loop contribution turns out to play the dominant role. The results for two-gamma decays are in satisfactory agreement with modern experimental data. The predictions for a_0 -> ρ(ω)γand f_0 -> ρ(ω)γwidths are given.

hep-ph↗

2γ-decays of scalar mesons (σ(600), f_0(980) and a_0(980)) in the Nambu-Jona-Lasinio model

The two-photon decay widths of scalar mesons σ(600), f_0(980) and a_0(980) are calculated in framework of the local Nambu-Jona-Lasinio model. The contributions of the quark loops (Hartree-Fock approximation) and the meson loops (next 1/N_c-approximation where N_c is the number of colors) are taken into account. These contributions, as we show, are the values of the same order of magnitude. For the f_0 decay the K-loop contribution turns out to play the dominant role. The results are in satisfactory agreement with modern experimental data.

hep-ph↗

Possible Method for Measuring the Proton Form Factors in Processes with and without Proton Spin Flip

The ratio of the squares of the electric and magnetic proton form factors is shown to be proportional to the ratio of the cross sections for the elastic scattering of an unpolarized electron on a partially polarized proton with and without proton spin flip. The initial proton at rest should be polarized along the direction of the motion of the final proton. Similar results are valid for both radiative $ep$ scattering and the photoproduction of pairs on a proton in the Bethe--Heitler kinematics. When the initial proton is fully polarized in the direction of the motion of the final proton, the cross section for the $ep \to ep$ process, as well as for the $ep \to ep γ$ and $γp \to e \bar e p$ processes, without (with) proton spin flip is expressed only in terms of the square of the electric (magnetic) proton form factor. Such an experiment on the measurement of the cross sections without and with proton spin flip would make it possible to acquire new independent data on the behavior of $G_E^2(Q^2)$ and $G_M^2(Q^2)$, which are necessary for resolving the contradictions appearing after the experiment of the JLab collaboration on the measurement of the proton form factors with the method of polarization transfer from the initial electron to the final proton.

hep-ph↗

Radiative decays of scalar mesons $f_0(980)$ and $a_0(980)$ into $ρ(ω) γ$ in the local Nambu-Jona-Lasinio model

In the framework of the local Nambu-Jona-Lasinio model the radiative decay widths of the scalar mesons $f_0(980)$ and $a_0(980)$ into $ργ$ and $ωγ$ are calculated. The contributions of the quark loops and the meson loops are taken into account. For the radiative decays of the scalar meson $f_0(980)$ the contribution of the meson loops plays the dominant role. On the other side for the radiative decays of the scalar meson $a_0(980)$ the main contribution is given by the quark loops.

hep-ph↗