135 research outputs found
Near-threshold Z-pair production in the semi-phenomenological model of unstable particles
Near-threshold production of neutral boson pairs is considered within the
framework of the model of unstable particles with smeared mass. The results of
calculations are in good agreement with LEP II data and Monte-Carlo
simulations.Comment: 7 pages, 2 figure
Nonperturbative and spin effects in the central exclusive production of tensor meson
We discuss central exclusive production (CEP) of the tensor
meson in proton-(anti)proton collisions at Tevatron, RHIC and LHC energies. The
amplitude for the process is derived within the -factorisation approach.
Differential and total cross sections are calculated for several unintegrated
gluon distributions (UGDFs). We compare exclusive production of all charmonium
states and . Equally good description
of the recent Tevatron data is achieved both with Martin-Ryskin
phenomenological UGDF and UGDF based on unified BFKL-DGLAP approach. Unlike for
Higgs production, the main contribution to the diffractive amplitude of heavy
quarkonia comes from nonperturbative region of gluon transverse momenta
Q_{\perp}<1\,\GeV. At 0, depending on UGDF we predict the
contribution of to the channel to be
comparable or larger than that of the one. This is partially due
to a significant contribution from lower polarization states for
and for meson. Corresponding
theoretical uncertainties are discussed.Comment: 18 pages, 12 figures, discrepancies with Durham group results
clarified, numerics corrected, basic conclusions unchanged, acknowledgements
adde
Finite-width effects in the near-threshold ZZZ and ZWW production at ILC
We calculate the cross-section of the near-threshold off-shell and
production at the International Linear Collider taking into account
their instability and the principal part of NLO corrections. The calculations
are performed in the framework of the model of unstable particles with smeared
mass-shell. We show that the contribution of the finite and widths
(their instability) is large in the Higgs resonance range and should be taken
into account in the Higgs boson searches at future colliders.Comment: 5 pages, 6 figure
Dispersive approach to the axial anomaly and nonrenormalization theorem
Anomalous triangle graphs for the divergence of the axial-vector current are
studied using the dispersive approach generalized for the case of higher orders
of perturbation theory. The validity of this procedure is proved up to two-loop
level. By direct calculation in the framework of dispersive approach we have
obtained that the two-loop AVV amplitude is equal to zero. According to the
Vainshtein's theorem the transversal part of the anomalous triangle is not
renormalized in the chiral limit. We generalize this theorem for tha case of
finite fermion mass in the triangle loop.Comment: 12 pages, version to appear in Physical Review
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