227 research outputs found
The radiative return at phi- and B-factories: FSR for muon pair production at next-to-leading order
Muon pair production through the radiative return is of importance for a
measurement of the hadronic production cross section in two ways: it provides
an independent calibration and it may give rise to an important background for
a measurement of the pion form factor. With this motivation the Monte Carlo
event generator PHOKHARA is extended to include next-to-leading order radiative
corrections to the reaction . Furthermore, virtual
ISR corrections to FSR from pions are introduced, which extends the
applicability of the generator into a new kinematical regime. Finally, the
effect of photon vacuum polarization is introduced into this new version of the
generator.Comment: 11 pages, 15 figure
Four-pion production in tau decays and e+e- annihilation: an update
An improved description of four-pion production in electron-positron
annihilation and in tau lepton decays is presented. The model amplitude is
fitted to recent data from BaBar which cover a wide energy range and which were
obtained exploiting the radiative return. Predicting tau decay distributions
from e+e- data and comparing these predictions with ALEPH and CLEO results, the
validity of isospin symmetry is confirmed within the present experimental
errors. A good description of two- and three-pion sub-distributions is
obtained. Special emphasis is put on the predictions for omega pi (->
pi+pi-pi0) in e+e- annihilation and in tau decay. The model amplitude is
implemented in the Monte Carlo generator PHOKHARA.Comment: a few typos correcte
Electron-positron annihilation into three pions and the radiative return
The Monte Carlo event generator PHOKHARA, which simulates hadron and muon production at electron-positron colliders through radiative return, has been extended to final states with three pions. A model for the form factor based on generalized vector dominance has been employed, which is consistent with presently available experimental observations
Radiative return : A progress on FSR tests
To improve the accuracy of the e+e ! + Radiative Return Method, one has to control the theoretical uncertainty of the final-state photon emission. It is of particular importance at DAPHNE for the analysis,
where cuts are relaxed to cover the threshold region. By means of Monte Carlo generator PHOKHARA we compare several final-state radiation models and present results, relevant for a meson factory running at
s = 1 GeV
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
High dose chemotherapy combined with transplantation of haematopoietic progenitor cells in the treatment of resistant and recurrent Hodgkin's disease
The radiative return at phi- and B-factories: FSR at next-to-leading order
The measurement of the pion form factor and, more generally, of the cross
section for electron--positron annihilation into hadrons through the radiative
return has become an important task for high luminosity colliders such as the
- or -meson factories. For detailed understanding and analysis of this
reaction, the construction of a Monte Carlo program, PHOKHARA, has been
undertaken. Version 2.0 was based on a next-to-leading order (NLO) treatment of
the corrections from initial-state radiation (ISR). In the present paper a
further extension of PHOKHARA (version 3.0) is described, which incorporates
NLO corrections to final-state radiation (FSR). The impact of combined ISR and
FSR on various distributions is investigated and methods are presented, which
will allow the extraction of the form factor, and even give access to inclusive
photon emission due to FSR. The dependence of the results on the model for FSR
is discussed and the impact of this contribution on the anomalous magnetic
moment of the muon is evaluated.Comment: 15 pages, 17 figures. Final version to appear in Eur. Phys. J.
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