2,018,715 research outputs found
Radiative decays of quarkonium states, momentum operator expansion and nilpotent operators
We present the method of calculation of radiative decays of composite
quark-antiquark systems with different J^{PC}: (Q\bar Q)_{in} -> gamma (Q\bar
Q)_{out}. The method is relativistic invariant, it is based on the double
dispersion relation integrals over the masses of composite mesons, it can be
used for the high spin particles and provides us with the gauge invariant
transition amplitudes. We apply this method to the case when the photon is
emitted by a constituent in the intermediate state (additive quark model). We
perform the momentum operator expansion of the spin amplitudes for the decay
processes. The problem of nilpotent spin operators is discussed.Comment: 21 pages, 1 figur
Birational automorphisms of a three-dimensional double quadric with an elementary singularity
It is proved that the group of birational automorphisms of a
three-dimensional double quadric with a singular point arising from a double
point on the branch divisor is a semidirect product of the free group generated
by birational involutions of a special form and the group of regular
automorphisms. The proof is based on the method of `untwisting' maximal
singularities of linear systems.Comment: 18 page
Associative production of B_c and D mesons at LHC
It is shown that the study of correlations in the associative production of
B_c and D mesons at LHC allows to obtain the essential information about the
B_c production mechanism.Comment: 14 pages, 10 figures. Some misprints have been removed in the last
version. The reference to CTEQ pdf has been adde
Radiative decays of basic scalar, vector and tensor mesons and the determination of the P-wave q\bar q multiplet
We perform simultaneous calculations of the radiative decays of scalar mesons
f_0(980)-> \gamma\gamma, a_0(980)-> \gamma\gamma, vector meson \phi(1020)->
\gamma f_0(980), \gamma a_0(980), \gamma \pi^0, \gamma \eta, \gamma \eta' and
tensor mesons a_2(1320)-> \gamma\gamma, f_2(1270)-> \gamma\gamma, f_2(1525)->
\gamma\gamma assuming all these states to be dominantly the q\bar q ones. A
good description of the considered radiative decays is reached by using almost
the same radial wave functions for scalar and tensor mesons that supports the
idea for the f_0(980), a_0(980) and a_2(1320), f_2(1270), f_2(1525) to belong
to the same P -wave q\bar q multiplet.Comment: 28 pages, LaTeX, 9 PostScript figures, epsfig.st
Compatible Lie brackets related to elliptic curve
For the direct sum of several copies of sl_n, a family of Lie brackets
compatible with the initial one is constructed. The structure constants of
these brackets are expressed in terms of theta-functions associated with an
elliptic curve. The structure of Casimir elements for these brackets is
investigated. A generalization of this construction to the case of
vector-valued theta-functions is presented. The brackets define a
multi-hamiltonian structure for the elliptic sl_n-Gaudin model. A different
procedure for constructing compatible Lie brackets based on the argument shift
method for quadratic Poisson brackets is discussed.Comment: 18 pages, Late
Baryon-baryon and baryon-antibaryon interaction amplitudes in the spin--momentum operator expansion method
Partial wave scattering amplitudes in baryon-baryon and baryon-antibaryon
collisions and amplitudes for the production and decay of baryon resonances are
constructed in the framework of the spin-momentum operator expansion method.
The approach is relativistically invariant and it allows us to perform combined
analyses of different reactions imposing analyticity and unitarity directly.
The role of final state interactions (triangle and box diagrams) is discussed.Comment: 23 pages, 10 figure
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