Neutrino oscillations: deriving the plane-wave approximation in the wave-packet approach

The plane-wave approximation is widely used in the practical calculations concerning neutrino oscillations. A simple derivation of this approximation starting from the neutrino wave-packet framework is presented.Comment: Presented at the 36th ITEP Winter School of Physics, session "Particle Physics", February 8-16, 2008, Otradnoe, Russi

Theoretical description of mixed film formation at the air/water interface : carboxylic acids–fatty amines

Thermodynamic parameters of mixed monolayer formation of aliphatic amines CnH2n+1NH2 and carboxylic acids CnH2n+1COOH (n = 6–16) are calculated using the quantum chemical semiempirical PM3 method. Four types of mixed dimers and tetramers amine–acid are considered. The total contribution of interactions between the hydrophilic parts of amine and acid into clusterization Gibbs energy is slightly lower than the corresponding interactions for individual surfactants. It suggests a synergetic interaction between the regarded amphiphilic compounds as proved by experimental data in the literature. Two types of competitive film formation are possible: mixed 2D film 1, where the molecules of the minor component are single distributed among the molecules of the prevailing second component (mixture of components on molecular level), and 2D film 2 with a domain structure comprised of pure component “islands” linked together. The dependence of the Gibbs energy of clusterization per monomer for 2D film 1 on the component mole fraction shows that the maximum synergetic effect is typical for the case that both surfactants have the same even number of carbon atoms in the hydrocarbon chain and form an equimolar mixture. Formation of 2D film 1 is more preferable than that of 2D film 2, if the difference of the hydrocarbon chain lengths is not larger than 5 methylene units. The limiting mole fraction of carboxylic acids in such mixed monolayers is 66.7%

Charmed penguin versus BAU

Since the Standard Model most probably cannot explain the large value of CP asymmetries recently observed in D-meson decays we propose the fourth quark-lepton generation explanation of it. As a byproduct weakly mixed leptons of the fourth generation make it possible to save the baryon number of the Universe from erasure by sphalerons. An impact of the 4th generation on BBN is briefly discussed.Comment: 13 pages, 3 figures, version to be published in JETP Letter

Once more on extra quark-lepton generations and precision measurements

Precision measurements of $Z$-boson parameters and $W$-boson and $t$-quark masses put strong constraints on non $SU(2)\times U(1)$ singlet New Physics. We demonstrate that one extra generation passes electroweak constraints even when all new particle masses are well above their direct mass bounds.Comment: Dedicated to L.B. Okun's 80th birthda

Modification of Coulomb law and energy levels of the hydrogen atom in a superstrong magnetic field

We obtain the following analytical formula which describes the dependence of the electric potential of a point-like charge on the distance away from it in the direction of an external magnetic field B: \Phi(z) = e/|z| [ 1- exp(-\sqrt{6m_e^2}|z|) + exp(-\sqrt{(2/\pi) e^3 B + 6m_e^2} |z|) ]. The deviation from Coulomb's law becomes essential for B > 3\pi B_{cr}/\alpha = 3 \pi m_e^2/e^3 \approx 6 10^{16} G. In such superstrong fields, electrons are ultra-relativistic except those which occupy the lowest Landau level (LLL) and which have the energy epsilon_0^2 = m_e^2 + p_z^2. The energy spectrum on which LLL splits in the presence of the atomic nucleus is found analytically. For B > 3 \pi B_{cr}/\alpha, it substantially differs from the one obtained without accounting for the modification of the atomic potential.Comment: version to be published in Physical Review D (incorrect "Keywords" in previous version have been cancelled

Dark matter from SU(4) model

The left-right symmetric Pati-Salam model of the unification of quarks and leptons is based on SU(4) and SU(2)xSU(2) groups. These groups are naturally extended to include the classification of families of quarks and leptons. We assume that the family group (the group which unites the families) is also the SU(4) group. The properties of the 4-th generation of fermions are the same as that of the ordinary-matter fermions in first three generations except for the family charge of the SU(4)_F group: F=(1/3,1/3,1/3,-1), where F=1/3 for fermions of ordinary matter and F=-1 for the 4-th generation. The difference in F does not allow the mixing between ordinary and fourth-generation fermions. Because of the conservation of the F charge, the creation of baryons and leptons in the process of electroweak baryogenesis must be accompanied by the creation of fermions of the 4-th generation. As a result the excess n_B of baryons over antibaryons leads to the excess n_{\nu 4}=N-\bar N=n_B of neutrinos over antineutrinos in the 4-th generation. This massive fourth-generation neutrino may form the non-baryonic dark matter. In principle their mass density n_{\nu 4}m_N in the Universe can give the main contribution to the dark matter, since the lower bound on neutrino mass m_N from the data on decay of the Z-bosons is m_N > m_Z/2. The straightforward prediction of this model leads to the amount of cold dark matter relative to baryons, which is an order of magnitude bigger than allowed by observations. This inconsistency may be avoided by non-conservation of the F-charge.Comment: 9 pages, 2 figures, version accepted in JETP Letters, corrected after referee reports, references are adde

Constraints on dark matter particles from theory, galaxy observations and N-body simulations

Mass bounds on dark matter (DM) candidates are obtained for particles decoupling in or out of equilibrium with {\bf arbitrary} isotropic and homogeneous distribution functions. A coarse grained Liouville invariant primordial phase space density $\mathcal D$ is introduced. Combining its value with recent photometric and kinematic data on dwarf spheroidal satellite galaxies in the Milky Way (dShps), the DM density today and $N$-body simulations, yields upper and lower bounds on the mass, primordial phase space densities and velocity dispersion of the DM candidates. The mass of the DM particles is bound in the few keV range. If chemical freeze out occurs before thermal decoupling, light bosonic particles can Bose-condense. Such Bose-Einstein {\it condensate} is studied as a dark matter candidate. Depending on the relation between the critical($T_c$)and decoupling($T_d$)temperatures, a BEC light relic could act as CDM but the decoupling scale must be {\it higher} than the electroweak scale. The condensate tightens the upper bound on the particle's mass. Non-equilibrium scenarios that describe particle production and partial thermalization, sterile neutrinos produced out of equilibrium and other DM models are analyzed in detail obtaining bounds on their mass, primordial phase space density and velocity dispersion. Light thermal relics with $m \sim \mathrm{few} \mathrm{keV}$ and sterile neutrinos lead to a primordial phase space density compatible with {\bf cored} dShps and disfavor cusped satellites. Light Bose condensed DM candidates yield phase space densities consistent with {\bf cores} and if $T_c\gg T_d$ also with cusps. Phase space density bounds from N-body simulations suggest a potential tension for WIMPS with $m \sim 100 \mathrm{GeV},T_d \sim 10 \mathrm{MeV}$.Comment: 27 pages 8 figures. Version to appear in Phys. Rev.

Atomic levels in superstrong magnetic fields and D=2 QED of massive electrons: screening

The photon polarization operator in superstrong magnetic fields induces the dynamical photon "mass" which leads to screening of Coulomb potential at small distances $z\ll 1/m$, $m$ is the mass of an electron. We demonstrate that this behaviour is qualitatively different from the case of D=2 QED, where the same formula for a polarization operator leads to screening at large distances as well. Because of screening the ground state energy of the hydrogen atom at the magnetic fields $B \gg m^2/e^3$ has the finite value $E_0 = -me^4/2 \ln^2(1/e^6)$.Comment: 12 pages, 2 figure