30 research outputs found
Ground-state energy of pionic hydrogen to one loop
We investigate the ground-state energy of the pi- p atom (pionic hydrogen) in
the framework of QCD+QED. In particular, we evaluate the strong energy-level
shift. We perform the calculation at next-to-leading order in the low-energy
expansion in the framework of the relevant effective field theory. The result
provides a relation between the strong energy shift and the pion-nucleon S-wave
scattering lengths - evaluated in pure QCD - at next-to-leading order in
isospin breaking and in the low-energy expansion. We compare our result with
available model calculations.Comment: Version accepted for publication in Eur. Phys. J. C; Eq. (B8)
corrected, comment after Eq. (B11) changed, additional minor changes in the
text; preprint number adde
Can one see the number of colors in eta, eta-prime --> pi^+ pi^- gamma?
We investigate the decays eta, eta-prime --> pi^+ pi^- gamma up to
next-to-leading order in the framework of the combined 1/N_c and chiral
expansions. Counter terms of unnatural parity at next-to-leading order with
unknown couplings are important to acommodate the results both to the
experimental decay width and the photon spectrum. The presence of these
coefficients does not allow for a determination of the number of colors from
these decays.Comment: 8 pages, 2 figure
Hadronic potentials from effective field theories
We construct the potentials that describe the spectrum and decay of electromagnetic bound states of hadrons, and are consistent with ChPT. These potentials satisfy the matching condition which enables one to express the parameters of the potential through the threshold scattering amplitudes calculated in ChPT. We further analyze the ambiguity in the choice of the short-range hadronic potentials, which satisfy this matching condition
Perturbative framework for the pi(+)pi(-) atom
The perturbative framework is developed for the calculation of the pi(+)pi(-)
atom characteristics on the basis of the field-theoretical Bethe-Salpeter
approach. A closed expression for the first-order correction to the pi(+)pi(-)
atom lifetime has been obtained.Comment: 8 pages, LaTeX-fil
Black Holes at Future Colliders and Beyond: a Topical Review
One of the most dramatic consequences of low-scale (~1 TeV) quantum gravity
in models with large or warped extra dimension(s) is copious production of mini
black holes at future colliders and in ultra-high-energy cosmic ray collisions.
Hawking radiation of these black holes is expected to be constrained mainly to
our three-dimensional world and results in rich phenomenology. In this topical
review we discuss the current status of astrophysical observations of black
holes and selected aspects of mini black hole phenomenology, such as production
at colliders and in cosmic rays, black hole decay properties, Hawking radiation
as a sensitive probe of the dimensionality of extra space, as well as an
exciting possibility of finding new physics in the decays of black holes.Comment: 31 pages, 10 figures To appear in the Journal of Physics
(Pi+Pi-) Atom in Chiral Perturbation Theory
Hadronic (Pi+Pi-) atom is studied in the relativistic perturbative approach
based on the Bethe-Salpeter equation. The general expression for the atom
lifetime is derived. Lowest-order corrections to the relativistic Deser-type
formula for the atom lifetime are evaluated within the Chiral Perturbation
Theory.Comment: 36 pages, LaTeX-file (revtex.sty
Hadronic potentials from effective field theories
We construct hadronic potentials that describe the spectrum and decays of electromagnetic bound states of hadrons, and are consistent with Chiral Perturbation Theory. This procedure enables one to clarify the status of the calculations-based on potential models-of the electromagnetic corrections to the observables of hadronic atoms and to the strong scattering amplitudes at low energy