4,803 research outputs found
A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates
Supermassive black hole binaries (SMBHBs) at sub-parsec separations should be
common in galactic nuclei, as a result of frequent galaxy mergers.
Hydrodynamical simulations of circumbinary discs predict strong periodic
modulation of the mass accretion rate on time-scales comparable to the orbital
period of the binary. As a result, SMBHBs may be recognized by the periodic
modulation of their brightness. We conducted a statistical search for periodic
variability in a sample of 35,383 spectroscopically confirmed quasars in the
photometric database of the Palomar Transient Factory (PTF). We analysed
Lomb-Scargle periodograms and assessed the significance of our findings by
modeling each individual quasar's variability as a damped random walk (DRW). We
identified 50 quasars with significant periodicity beyond the DRW model,
typically with short periods of a few hundred days. We find 33 of these to
remain significant after a re-analysis of their periodograms including
additional optical data from the intermediate-PTF and the Catalina Real-Time
Transient Survey (CRTS). Assuming that the observed periods correspond to the
redshifted orbital periods of SMBHBs, we conclude that our findings are
consistent with a population of unequal-mass SMBHBs, with a typical mass ratio
as low as q = M2/M1 ~ 0.01.Comment: MNRAS (accepted), new section 4.
Tvorba f0-mezona procesom e +e − → ϕf
Enigmatic nature of f0(980) meson can be tested in C–τ factory with total energy in e +e − center of mass 3 < √ s < 4 GeV. This facility has the advantage compared with ϕ–factory with √ s = 1.02 GeV where f0(980) properties can be investigated in the process e +e − → γf0(980). The reason of that is strong phase volume suppression ∼ ω 3 of the cross section in the experiments at ϕ–factories. Our approach is based on the analysis of the lowest order loop Feynman diagrams with the strange constituent quark or charged kaon as virtual loop particles. The relative values of the contributions of quark loop and kaon loop are discussed. The differential cross section as well as the estimation of the total one are illustrated numerically.Zagonetna priroda mezona f0(980) može se istraživati u tvornicama C–τ s ukupnom energijom e +e − u sustavu središta mase 3 < √ s < 4 GeV. Takav pogon ima prednost prema tvornicama ϕ–mezona sa √ s = 1.02 GeV u kojima se može istraživati proces e +e − → γf0(980). Uzrok je snažno potisnuće udarnog presjeka faktorom ∼ ω 3 zbog faznog prostora u mjerenjima u tvornicama ϕ. Naš se pristup zasniva na analizi Feynmanovih diagrama petlja najnižeg reda uzimajući strani sastavni kvark ili nabijeni kaon kao virtualne čestice u petlji
Bremsstrahlung photon polarization for , and high energy collisions
The polarization of bremsstrahlung photon in the processes , and is calculated for peripheral
kinematics, in the high energy limit where the cross section does not decrease
with the incident energy. When the initial electron is
unpolarized(longitudinally polarized) the final photon can be linearly
(circularly) polarized. The Stokes parameters of the photon polarization are
calculated as a function of the kinematical variables of process: the energy of
recoil particle, the energy fraction of scattered electron, and the polar and
azimuthal angles of photon. Numerical results are given in form of tables, for
typical values of the relevant kinematic variables.Comment: 9 pages, 3 figure
Electroweak Hadronic Contributions to the muon g-2
We reanalyze the two-loop electroweak hadronic contributions to the muon g-2
that may be enhanced by large logarithms. The present evaluation is improved
over those already existing in the literature by the implementation of the
current algebra Ward identities and the inclusion of the correct short-distance
QCD behaviour of the relevant hadronic Green's function.Comment: 29 pages, 6 figures, LaTeX. Typos fixe
Contributions of semi-hadronic states to amm of muon, in frames of Nambu-Jona-Lasinio model
We calculate the contribution of semi-hadronic states with pseudoscalar
and scalar ((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 and as a
hadrons in frames of Nambu-Jona-Lasinio model. The contribution of
state is in agreement with results obtained in previous
theoretical considerations as well as with experimental data
, besides we estimate
We
discass as well the LbL mechanism with Comment: 6 pages, 2 figure
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