149 research outputs found
Two-photon form factors of the pi0, eta and eta-prime mesons in the chiral theory with resonances
We have developed a phenomenological approach which describes very well the
pi0, eta and eta-prime meson production in the two-photon interactions. The
simultaneous description of the pi0, eta and eta-prime meson two-photon form
factors is consistent with data in the space-like region. The obtained form
factors are implemented in the event generator EKHARA and the simulated cross
sections are presented. Uncertainties in the measured form factors coming from
the model dependence in Monte Carlo simulations are studied. The model
predictions for the form factor slopes at the origin are given and the high-Q2
limit is also discussed.Comment: 11 pages, 7 figures, 3 tables; two-column revtex4 styl
Mini-Proceedings of the 15th meeting of the Working Group on Rad. Corrections and MC Generators for Low Energies
The mini-proceedings of the 15th Meeting of the "Working Group on Rad.
Corrections and MC Generators for Low Energies" held in Mainz on April 11,
2014, are presented. These meetings, started in 2006, have as aim to bring
together experimentalists and theorists working in the fields of meson
transition form factors, hadronic contributions to and the
effective fine structure constant, and development of Monte Carlo generators
and Radiative Corrections for precision e+e- and tau physics.Comment: 21 pages, 7 contributions. Editors: S. E. Mueller and G. Venanzon
BOKASUN: a fast and precise numerical program to calculate the Master Integrals of the two-loop sunrise diagrams
We present the program BOKASUN for fast and precise evaluation of the Master
Integrals of the two-loop self-mass sunrise diagram for arbitrary values of the
internal masses and the external four-momentum. We use a combination of two
methods: a Bernoulli accelerated series expansion and a Runge-Kutta numerical
solution of a system of linear differential equations
NLO QED Corrections to Hard-Bremsstrahlung Emission in Bhabha Scattering
In this paper we present a numerical implementation of the one-loop QED
corrections to the hard-bremsstrahlung process e- e+ \to e- e+ gamma. These
corrections can be included in the Monte Carlo event generators employed for
simulating Bhabha scattering events at low-energy high-luminosity
electron-positron colliders. The calculation is performed by employing the
reduction method developed by Ossola, Papadopoulos and Pittau. Our results are
implemented in a modular code for the numerical evaluation of the scattering
amplitudes for any given phase-space point. In a similar way, we also evaluate
the one-loop QED corrections to e- e+ \to mu- mu+ gamma, which represents an
interesting application of the method in the presence of two different mass
scales in the loops.Comment: 8 pages, 5 figures, v2 minor changes: comments and references added,
matches PLB versio
NNLO massive corrections to Bhabha scattering and theoretical precision of BabaYaga@NLO
We provide an exact calculation of next-to-next-to-leading order (NNLO)
massive corrections to Bhabha scattering in QED, relevant for precision
luminosity monitoring at meson factories. Using realistic reference event
selections, exact numerical results for leptonic and hadronic corrections are
given and compared with the corresponding approximate predictions of the event
generator BabaYaga@NLO. It is shown that the NNLO massive corrections are
necessary for luminosity measurements with per mille precision. At the same
time they are found to be well accounted for in the generator at an accuracy
level below the one per mille. An update of the total theoretical precision of
BabaYaga@NLO is presented and possible directions for a further error reduction
are sketched.Comment: 5 pages, 3 tables, contrib. to proceedings of International Workshop
on e+e- collisions: from Phi to Psi, PHIPSI11, BINP, Novosibirsk, Russia,
September 19-22, 201
Constraining the Hadronic Contributions to the Muon Anomalous Magnetic Moment
The mini-proceedings of the Workshop on "Constraining the hadronic
contributions to the muon anomalous magnetic moment" which included the "13th
meeting of the Radio MonteCarLow WG" and the "Satellite meeting R-Measurements
at BES-III" held in Trento from April 10th to 12th, 2013, are presented. This
collaboration meeting aims to bring together the experimental e+e- collider
communities from BaBar, Belle, BESIII, CMD2, KLOE, and SND, with theorists
working in the fields of meson transitions form factors, hadronic contributions
to (g-2)_\mu and effective fine structure constant, and development of Monte
Carlo generator and Radiative Corrections for precision e+e- and tau physics.Comment: 45 pages, 17 contributions. Editors: P. Masjuan and G. Venanzon
Event Generators for Bhabha Scattering
The results obtained by the "Event Generators for Bhabha Scattering" working
group during the CERN Workshop "Physics at LEP2" (1994/1995) are presented.Comment: 70 pages, PostScript file. To appear in the Report of the Workshop on
Physics at LEP2, G. Altarelli T. Sjostrand and F. Zwirner ed
High energy parton-parton amplitudes from lattice QCD and the stochastic vacuum model
Making use of the gluon gauge-invariant two-point correlation function,
recently determined by numerical simulation on the lattice in the quenched
approximation and the stochastic vacuum model, we calculate the elementary
(parton-parton) amplitudes in both impact-parameter and momentum transfer
spaces. The results are compared with those obtained from the Kr\"{a}mer and
Dosch ansatz for the correlators. Our main conclusion is that the divergences
in the correlations functions suggested by the lattice calculations do not
affect substantially the elementary amplitudes. Phenomenological and
semiempirical information presently available on elementary amplitudes is also
referred to and is critically discussed in connection with some theoretical
issues.Comment: Text with 11 pages in LaTeX (twocolumn form), 10 figures in
PostScript (psfig.tex used). Replaced with changes, Fig.1 modified, two
references added, some points clarified, various typos corrected. Version to
appear in Phys. Rev.
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