24 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
omega --> pi0 gamma* and phi --> pi0 gamma* Transition form factors in dispersion theory
We calculate the omega --> pi0 gamma* and phi --> pi0 gamma* electromagnetic
transition form factors based on dispersion theory, relying solely on a
previous dispersive analysis of the corresponding three-pion decays and the
pion vector form factor. We compare our findings to recent measurements of the
omega --> pi0 mu+ mu- decay spectrum by the NA60 collaboration, and strongly
encourage experimental investigation of the Okubo-Zweig-Iizuka-forbidden phi
--> pi0 l+ l- decays in order to understand the strong deviations from
vector-meson dominance found in these transition form factors.Comment: 11 pages, 8 figures; references updated, version published in Phys.
Rev.
Radiative decays with scalar mesons a0(980) and f0(980) in Resonance Chiral Theory
The phi(1020) radiative decays form a good playground for study of the
low-lying a0(980) and f0(980) scalar mesons. The complicated interplay of kaon
loop mechanism, isoscalar meson mixing and momentum dependence of the effective
couplings manifests itself in the invariant mass distributions in the phi(1020)
-> pi0 pi0 gamma and pi eta gamma spectra. These distributions are fitted in
framework of Resonance Chiral Theory.Comment: 5 pages, 3 figures; presented at International Workshop on e+e-
collisions from Phi to Psi, Laboratori Nazionali di Frascati, Italy, 7-10
April 200
e+e- annihilation to (pi0 pi0 gamma) and (pi0 eta gamma) as a source of information on scalar and vector mesons
We present a general framework for the model-independent decomposition of the
fully differential cross section of the reactions e+e- -> gamma* -> (pi0 pi0
gamma) and e+e- -> gamma* -> (pi0 eta gamma), which can provide important
information on the properties of scalar mesons: f0(600), f0(980) and a0(980).
For the model-dependent ingredients in the differential cross section, an
approach is developed, which relies on Resonance Chiral Theory with vector and
scalar mesons. Numerical results are compared to data. The framework is
convenient for development of a Monte Carlo generator and can also be applied
to the reaction e+e- -> gamma* -> (pi+ pi- gamma).Comment: 15 pages, 12 Figures, 4 Tables; LaTeX svjour style; update to the
version accepted for publication in the European Physical Journal
Radiative decays with light scalar mesons and singlet-octet mixing in ChPT
We study different types of radiative decays involving f0(980) and a0(980)
mesons within a unified ChPT-based approach at one-loop level. Light scalar
resonances which are seen in pi pi, pi eta, K K-bar channels of phi(1020)
radiative decays and in J/psi decays are responsible for key questions of
low-energy dynamics in the strong interaction sector, and decays phi(1020) ->
gamma a0(980), phi(1020) -> gamma f0(980), a0(980) -> gamma gamma, f0(980) ->
gamma gamma are of interest for current experimental programs in Juelich,
Frascati and Novosibirsk. From theoretical point of view it is important to
verify whether light scalar mesons are members of some flavor octet or nonet.
We find a value of mixing angle dictated by consistency with experiment and
coupling structures of ChPT Lagrangian. Decay widths f0(980)/a0(980) -> gamma
rho(770)/omega(782), which are not studied experimentally yet, are predicted.
We also obtain several relations between widths, which hold independently of
coupling constants and represent a fingerprint of the model.Comment: 18 pages, 8 figures; misprints in text and tables corrected,
discussion extended, references added; version accepted for publication in
Eur.Phys.J.
MesonNet 2013 International Workshop. Mini-proceedings
The mini-proceedings of the MesonNet 2013 International Workshop held in
Prague from June 17th to 19th, 2013, are presented. MesonNet is a research
network within EU HadronPhysics3 project (1/2012 -- 12/2014). The web page of
the conference, which contains all talks, can be found at
http://ipnp.mff.cuni.cz/mesonnet13Comment: 106 pages, 53 contributions. Mini-proceedings of the MesonNet 2013
International Workshop. Editors: K. Kampf, A. Kupsc, and P. Masjua
Measurement of sigma(e+ e- -> pi+ pi-) from threshold to 0.85 GeV^2 using Initial State Radiation with the KLOE detector
We have measured the cross section of the radiative process e+e- ->
pi+pi-gamma with the KLOE detector at the Frascati phi-factory DAPHNE, from
events taken at a CM energy W=1 GeV. Initial state radiation allows us to
obtain the cross section for e+e- -> pi+pi-, the pion form factor |F_pi|^2 and
the dipion contribution to the muon magnetic moment anomaly, Delta a_mu^{pipi}
= (478.5+-2.0_{stat}+-5.0_{syst}+-4.5_{th}) x 10^{-10} in the range 0.1 <
M_{pipi}^2 < 0.85 GeV^2, where the theoretical error includes a SU(3) ChPT
estimate of the uncertainty on photon radiation from the final pions. The
discrepancy between the Standard Model evaluation of a_mu and the value
measured by the Muon g-2 collaboration at BNL is confirmed.Comment: 17 pages, 11 figures, revised treatment of FSR uncertainty, version
to appear on Physics Letters
On the possibility to measure the (pi0 to gamma gamma) decay width and the (gamma* gamma to pi0) transition form factor with the KLOE-2 experiment
A possibility of KLOE-2 experiment to measure the width Gamma(pi0 to gamma
gamma) and the (pi0 gamma gamma*) form factor F(Q^2) at low invariant masses of
the virtual photon in the space-like region is considered. This measurement is
an important test of the strong interaction dynamics at low energies. The
feasibility is estimated on the basis of a Monte-Carlo simulation. The expected
accuracy for Gamma(pi0 to gamma gamma) is at a per cent level, which is better
than the current experimental world average and theory. The form factor will be
measured for the first time at Q^2 less or equal 0.1 GeV^2 in the space-like
region. The impact of these measurements on the accuracy of the pion-exchange
contribution to the hadronic light-by-light scattering part of the anomalous
magnetic moment of the muon is also discussed.Comment: 2-column style; matches the revision accepted by EPJ
Physics with the KLOE-2 experiment at the upgraded DANE
Investigation at a --factory can shed light on several debated issues
in particle physics. We discuss: i) recent theoretical development and
experimental progress in kaon physics relevant for the Standard Model tests in
the flavor sector, ii) the sensitivity we can reach in probing CPT and Quantum
Mechanics from time evolution of entangled kaon states, iii) the interest for
improving on the present measurements of non-leptonic and radiative decays of
kaons and eta/eta mesons, iv) the contribution to understand the
nature of light scalar mesons, and v) the opportunity to search for narrow
di-lepton resonances suggested by recent models proposing a hidden dark-matter
sector. We also report on the physics in the continuum with the
measurements of (multi)hadronic cross sections and the study of gamma gamma
processes.Comment: 60 pages, 41 figures; added affiliation for one of the authors; added
reference to section