23,550 research outputs found
Search for X(3872) in gamma gamma Fusion and ISR at CLEO
We report on a search for the X(3872) state using 15.1 fb^{-1} of e+ e-
annihilation data taken with the CLEO III detector in the sqrt{s} = 9.46-11.30
GeV region. Separate searches for the production of X(3872) in untagged gamma
gamma fusion and e+ e- annihilation following initial state radiation are made
by taking advantage of the unique correlation of J/psi -> l+ l- in X(3872)
decay into J/psi pi+ pi-. No signals are observed in either case, and 90%
confidence upper limits are established as (2J+1)Gamma_{gammagamma}(X(3872))B(X
-> J/psi pi+ pi-) J/psi pi+ pi-) < 8.3
eV.Comment: 4 pages, 2 figures, to appear in the proceedings of the 1st Meeting
of the APS Topical Group on Hadronic Physics, Fermilab, Oct. 24-26, 200
Nucleon form factors, B-meson factories and the radiative return
The feasibility of a measurement of the electric and magnetic nucleon form
factors at -meson factories through the radiative return is studied. Angular
distributions allow a separation of the contributions from the two form
factors. The distributions are presented for the laboratory and the hadronic
rest frame, and the advantages of different coordinate systems are
investigated. It is demonstrated that values up to 8 or even 9 GeV
are within reach. The Monte Carlo event generator PHOKHARA is extended to
nucleon final states, and results are presented which include Next-to-Leading
Order radiative corrections from initial-state radiation. The impact of angular
cuts on rates and distributions is investigated and the relative importance of
radiative corrections is analysed.Comment: 9 pages, 11 figures. Final version to appear in Eur. Phys. J.
Quark mass dependence of pseudoscalar masses and decay constants on a lattice
Our previous calculations of the sea- and valence-quark mass dependence of
the pseudoscalar meson masses and decay constants is repeated on a 16^3x32
lattice which allows for a better determination of the quantities in question.
The conclusions are similar as before on the 16^4 lattice [1].
The two light dynamical quark flavours we simulate have masses in the range
1/4 m_s < m_{u,d} < 2/3 m_s.
The sea quark mass dependence of f_pi and m_pi^2/m_q is well described by the
next-to-leading order (NLO) Chiral Perturbation Theory (ChPT) formulas and
clearly shows the presence of chiral logarithms.
The valence quark mass dependence requires the presence of NNLO contributions
in Partially Quenched ChPT (PQChPT) -- in addition to the NLO terms.
The O(a) lattice artifacts in these quantities turn out to be small.Comment: 17 pages, 5 figure
Quark mass dependence of masses and decay constants of the pseudo-Goldstone bosons in QCD
The dependence of the pseudoscalar meson masses and decay constants on sea
and valence quark masses is compared to next-to-leading order (NLO) Chiral
Perturbation Theory (ChPT). The numerical simulations with two light dynamical
quark flavors are performed with the Wilson-quark lattice action at gauge
coupling beta=5.1 and hopping parameters kappa=0.176, 0.1765, 0.177 on a 16^4
lattice. O(a) lattice artifacts are taken into account by applying chiral
perturbation theory for the Wilson lattice action. The values of the relevant
combinations of Gasser-Leutwyler constants L_4, L_5, L_6 and L_8 are estimated.Comment: 21 pages, 4 figures; discussion of the sea quark mass dependence
changed, references adde
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