Tensor charges of light baryons in the Infinite Momentum Frame

We have used the Chiral-Quark Soliton Model formulated in the Infinite Momentum Frame to investigate the octet, decuplet and antidecuplet tensor charges up to the 5Q level. Using flavor SU(3) symmetry we have obtained for the proton $\delta u=1.172$ and $\delta d=-0.315$ in fair agreement previous model estimations. The 5Q allowed us to estimate also the strange contribution to the proton tensor charge $\delta s=-0.011$. All those values have been obtained at the model scale Q^2=0.36 GeV^2.Comment: 16 pages, 5 figure

Influence of Meson's Widths on Yukawa-like Potentials and Lattice Correlation Functions

Euclidean point-to-point propagators or wall-to-wall correlators related to exchange by an unstable particle(sigma,rho,omega-mesons) are modified by presence of particle width. In particular, the usual method of deriving particle masses from logarithmic derivatives need to be modified. Similarly Yukawa-like potentials of nuclear physics due to exchange of those mesons are significantly modified since the coupling to the decay products is strong. For example, the large distance asymptotic changes, exp(-M_{min} r), where M_{min} is the sum of the decay product masses (2 m_{\pi}, 2 m_{e}, 2 m_{\nu}). In the area M_{min}r<1the potential has a long-range tail 1/r^3. Similar effects appear due to the virtual decays in the elecroweak sector of the Standard model. The $Z-\gamma$ mixing via electron loop gives the parity violation potential with the range $1/2 m_{e}$, i.e. the range of the weak interaction increases $10^{5}$ times

Multi-fermion states for heavy fermions bound via Higgs exchange

A possibility to produce bound states of several heavy fermions, which are bound together due to the Higgs exchange, is examined. It is shown that for 12 fermions, 6 fermions and 6 antifermions, occupying the lowest S_{1/2} shell this bound state cannot exist if the fermion mass is below the critical value, which depends on the Higgs mass and is found to be restricted to 320 < m_{cr} < 410 Gev/c^2 for the Higgs mass in the interval 100 < m_{H}< 200 Gev/c^2. This estimate is derived in the relativistic mean field approximation. The corrections are estimated to be not able to reduce significantly the critical value for the fermion mass. Consequently there exist no bound state for 12 top quarks, and the only feasible hope to observe a bag of 12 fermions experimentally should rely on possible existence of heavy fermions of the next, fourth generations.Comment: 4 pages, 3 figure

Neutrino scattering on atomic electrons in searches for neutrino magnetic moment

The scattering of a neutrino on atomic electrons is considered in the situation where the energy transferred to the electrons is comparable to the characteristic atomic energies, as relevant to the current experimental search for neutrino magnetic moment. The process is contributed by the standard electroweak interaction as well as by the possible neutrino magnetic moment. Quantum mechanical sum rules are derived for the inclusive cross section at a fixed energy deposited in the atomic system, and it is shown that the differential over the energy transfer cross section is given, modulo very small corrections, by the same expression as for free electrons, once all possible final states of the electronic system are taken into account. Thus the atomic effects effectively cancel in the inclusive process.Comment: 7 pages. A clarifying illustrative example adde

Electronic structure and optical properties of quantum confined lead-salt nanowires

In the framework of four-band envelope-function formalism, developed earlier for spherical semiconductor nanocrystals, we study the electronic structure and optical properties of quantum-confined lead-salt (PbSe and PbS) nanowires (NWs) with a strong coupling between the conduction and the valence bands. We derive spatial quantization equations, and calculate numerically energy levels of spatially quantized states of a transverse electron motion in the plane perpendicular to the NW axis, and electronic subbands developed due to a free longitudinal motion along the NW axis. Using explicit expressions for eigenfunctions of the electronic states, we also derive analytical expressions for matrix elements of optical transitions and study selection rules for interband absorption. Next we study a two-particle problem with a conventional long-range Coulomb interaction and an interparticle coupling via medium polarization. The obtained results show that due to a large magnitude of the high-frequency dielectric permittivity of PbSe material, and hence, a high dielectric NW/vacuum contrast, the effective coupling via medium polarization significantly exceeds the effective direct Coulomb coupling at all interparticle separations along the NW axis. Furthermore, the strong coupling via medium polarization results in a bound state of the longitudinal motion of the lowest-energy electron-hole pair (a longitudinal exciton), while fast transverse motions of charge carriers remain independent of each other.Comment: Some misprints and mistakes are correcte

Electroexcitation of the Roper resonance in the relativistic quark models

The amplitudes of the transition gamma* N -> P11(1440) are calculated within light-front relativistic quark model assuming that the P11(1440) is the first radial excitation of the 3q ground state. The results are presented along with the predictions obtained in other relativistic quark models. In comparison with the previous calculations, we have extended the range of Q^2 up to 4.5 GeV^2 to cover the kinematic interval of the forthcoming experimental data. Using approach based on PCAC, we have checked the relative sign between quark model predictions for the N and P11(1440) contributions to the pion electroproduction found in previous investigations.Comment: 5 pages, 1 figure, accepted by PR

Handling the Handbag Diagram in Compton Scattering on the Proton

Poincare invariance, gauge invariance, conservation of parity and time reversal invariance are respected in an impulse approximation evaluation of the handbag diagram. Proton wave functions, previously constrained by comparison with measured form factors, that incorporate the influence of quark transverse and orbital angular momentum (and the corresponding violation of proton helicity conservation) are used. Computed cross sections are found to be in reasonably good agreement with early measurements. The helicity correlation between the incident photon and outgoing proton, $K_{LL}$, is both large and positive at back angles. For photon laboratory energies of $\le$ 6 GeV, we find that $K_{LL}\ne A_{LL}$, $D_{LL}\ne1$, and that the polarization $P$ can be large.Comment: 9 pages, 6 figures. Replacement fixes some typos, improves references and figures. An error in Fig. 6 was corrected and related comments in the text change

Dissipationless electron transport in photon-dressed nanostructures

It is shown that the electron coupling to photons in field-dressed nanostructures can result in the ground electron-photon state with a nonzero electric current. Since the current is associated with the ground state, it flows without the Joule heating of the nanostructure and is nondissipative. Such a dissipationless electron transport can be realized in strongly coupled electron-photon systems with the broken time-reversal symmetry - particularly, in quantum rings and chiral nanostructures dressed by circularly polarized photons.Comment: 4 pages; 1 figure; published versio

Radiation Emission by Extreme Relativistic Electrons and Pair Production by Hard Photons in a Strong Plasma Wakefield

Radiation spectrum of extreme relativistic electrons and a probability of electron-positron pair production by energetic photons in a strong plasma wakefield are derived in the framework of a semiclassical approach. It is shown that that the radiation losses of the relativistic electron in the plasma wakefield scale as $\propto \epsilon ^{2 / 3}$ in the quantum limit when the energy of the radiated photon becomes close to the electron energy, $\epsilon$. The quantum effects will play a key role in future plasma-based accelerators operating at ultrahigh energy of the electrons.Comment: 10 pages, 2 figure

Transverse target spin asymmetry in inclusive DIS with two-photon exchange

We study the transverse target spin dependence of the cross section for inclusive electron-nucleon scattering with unpolarized beam. Such dependence is absent in the one-photon exchange approximation (Christ-Lee theorem) and arises only in higher orders of the QED expansion, from the interference of one-photon and absorptive two-photon exchange amplitudes as well as from real photon emission (bremsstrahlung). We demonstrate that the transverse spin-dependent two-photon exchange cross section is free of QED infrared and collinear divergences. We argue that in DIS kinematics the transverse spin dependence should be governed by a "parton-like" mechanism in which the two-photon exchange couples mainly to a single quark. We calculate the normal spin asymmetry in an approximation where the dominant contribution arises from quark helicity flip due to interactions with non-perturbative vacuum fields (constituent quark picture) and is proportional to the quark transversity distribution in the nucleon. Such helicity-flip processes are not significantly Sudakov-suppressed if the infrared scale for gluon emission in the photon-quark subprocess is of the order of the chiral symmetry breaking scale, mu_chiral^2 >> Lambda_QCD^2. We estimate the asymmetry in the kinematics of the planned Jefferson Lab Hall A experiment to be of the order 10^{-4}, with different sign for proton and neutron. We also comment on the spin dependence in the limit of soft high-energy scattering.Comment: 22 pages, 14 figures; uses revtex