Related papers: Exclusive two-photon annihilation at large energy …
Using the close relationship between the low--energy constants of chiral perturbation theory and the chiral invariant interactions of the vector meson resonances with the pseudoscalar mesons, we investigate the process $\rho^0 \ra \pi^+…
Preliminary results on the study of e+e- --> phi(1020) --> pi0 pi0 gamma, eta pi0 gamma processes from SND experiment at VEPP-2M collider in Novosibirsk are presented. Branching ratios of rare radiative phi --> pi0 pi0 gamma and phi --> pi0…
We perform a QCD analysis of the exclusive production of two mesons in gamma^* gamma collisions in the kinematical domain of large photon virtuality Q and small hadronic invariant mass W. This reaction is dominated by a scale invariant…
The amplitude for Higgs boson decay into two photons in a homogeneous and time-independent magnetic field is investigated by proper-time regularization in a gauge invariant manner and is found to be singular at large field values. The…
We present a theoretical study of the $\gamma\gamma \to \pi\eta$ process from the threshold up to 1.4 GeV in the $\pi\eta$ invariant mass. For the s-wave $a_0(980)$ resonance state we adopt a dispersive formalism using a coupled-channel…
In Ref.~\cite{Guo:2021rre}, we proposed to replace the final dark matter (DM) particle in the semi-annihilation mode $\rm DM+DM\to antiDM+Higgs~boson$ with its $Z_{N\geq 3}$ companion, thus reducing DM number density without DM-nucleon…
We briefly review our works on ultraperipheral heavy ion collisions. We discuss both $\gamma \gamma$ and rescattering of hadronic photon fluctuation induced by one nucleus in the collision partner. Production of one and two leptonic and…
Due to coherence, there are strong electromagnetic fields of short duration in very peripheral collisions. They give rise to photon-photon and photon-nucleus collisions with a high flux up to an invariant mass region hitherto unexplored…
The $\gamma$ ray emission originating from in-flight annihilation (IA) of positrons is a powerful observable for constraining high-energy positron production from exotic sources. By comparing diffuse $\gamma$ ray observations of INTEGRAL,…
The propagation of high energy (HE, $E_\gamma>100$ MeV) and very high-energy gamma-rays (VHE, $E_\gamma>100$ GeV) in the extra-galactic photon field leads to pair-production and consequently energy- and distance-dependent attenuation of the…
If the present dark matter in the Universe annihilates into Standard Model particles, it must contribute to the gamma ray fluxes detected on the Earth. The magnitude of such contribution depends on the particular dark matter candidate, but…
Within the quark model a generalization is proposed of the commonly used annihilation potential to describe antiproton-proton annihilation into two mesons, the so-called $^3P_0$ and $^3S_1$ mechanisms. This generalized potential treats the…
Hadrons containing at least one heavy quark (charm or bottom) frequently have small enough natural widths that decay modes involving a single photon have detectable branching fractions. Photons of typical energy greater than 100 MeV have…
We present the results of a new calculation for the photodisintegration of ultra-high energy cosmic ray nuclei on soft photon targets. We include all the relevant photodisintegraton processes i.e giant dipole resonance, quasi-deuteron,…
The new data on $\rho,\omega,\phi$ radiative decays into $\pi^0\gamma,\eta\gamma,\eta'\gamma$ from SND experiment at VEPP-2M $e^+e^-$ collider are presented.
We admit that the vacuum is not empty but is filled with continuously appearing and disappearing virtual fermion pairs. We show that if we simply model the propagation of the photon in vacuum as a series of transient captures within the…
The exclusive decay modes $B \to K \gamma\gamma$ and $B_s \to \eta (\eta') \gamma\gamma$ are shown to have significant branching ratios of approximately $0.5\times 10^{-7}$. This first calculation of these modes employs a model based on a…
Order alpha^2 contribution to the orthopositronium decay rate due to one-photon virtual annihilation is found to be delta Gamma = (alpha/pi)^2 (pi^2 ln(alpha) - 0.8622(9))Gamma_LO.
Using the most general model independent form of the effective Hamiltonian the rare decay B_s->nu nu gamma is studied. The sensitivity of the photon energy distribution and branching ratio to new Wilson coefficients are investigated.
The process of photon splitting $\gamma \to \gamma \gamma$ in a strong magnetic field is investigated both below and above the pair creation threshold. Contrary to the statement by Baier et al., the ``allowed'' channel $\alw$ is shown not…