24,257 research outputs found
e+e- --> e+e- pi0 pi0 at Daphne
The production of the sigma(500) meson in gamma gamma --> pi0 pi0 is studied.
In particular, the KLOE data collected during the DAPHNE run at sqrt(s)= 1 GeV
are appropriate to this purpose because of the strong reduction of Kaon
backgrounds.Comment: 13 pages, 9 figures, few comments adde
Isospin constraints from/on B->pipi
The Standard Model constraints on alpha which can be derived from the B->
pipi decays are revisited in some depth. As experimental inputs, the three
branching ratios, the two CP parameters Spipi and Cpipi and/or the value of
alpha as determined by the global CKM fit are used. The constraints discussed
here are model independent in the sense that they rely only on Isospin
symmetry, following the Gronau-London proposal. A new bound on B00 and the
function C00(B00) are introduced. The Grossman-Quinn bound is rediscussed. A
close form expression is given for alpha as a function of the measurements.
Various scenarii for the future of the isospin analysis are explored. To probe
the Standard Model the (B00,C00) plane is introduced.Comment: 25 pages, 8 figures, Submitted to Eur. Phys. J.
The statistical parton distributions: status and prospects
New experimental results on polarized structure functions, cross sections for
neutral and charge current reactions and () charge
current on isoscalar targets are compared with predictions using the
statistical parton distributions, which were previously determined. New data on
cross sections for Drell-Yan processes, single jet in collisions and
inclusive production in collisions are also compared with
predictions from this theoretical approach. The good agreement which we find
with all these tests against experiment, strenghtens our opinion on the
relevance of the role of quantum statistics for parton distributions. We will
also discuss the prospects of this physical framework.Comment: 34 pages, 23 figures, references and figures adde
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
Quaero@H1: An Interface to High-pT HERA Event Data
Distributions from high-pT HERA event data analyzed in a general search for
new physics at H1 have been incorporated into Quaero, an algorithm designed to
automate tests of specific hypotheses with high energy collider data. The use
of Quaero@H1 to search for leptoquarks, R-parity violating supersymmetry, and
excited quarks provides examples to develop intuition for the algorithm's
performance.Comment: Submitted to Eur. Phys. J.
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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