1,090 research outputs found
Generalized companion matrix for approximate GCD
We study a variant of the univariate approximate GCD problem, where the
coefficients of one polynomial f(x)are known exactly, whereas the coefficients
of the second polynomial g(x)may be perturbed. Our approach relies on the
properties of the matrix which describes the operator of multiplication by gin
the quotient ring C[x]=(f). In particular, the structure of the null space of
the multiplication matrix contains all the essential information about GCD(f;
g). Moreover, the multiplication matrix exhibits a displacement structure that
allows us to design a fast algorithm for approximate GCD computation with
quadratic complexity w.r.t. polynomial degrees.Comment: Submitted to MEGA 201
Kpi form factors and final state interactions in D+ --> K- pi+ pi+ decays
We present a model for the decay D+ --> K- pi+ pi+. The weak interaction part
of this reaction is described using the effective weak Hamiltonian in the
factorisation approach. Hadronic final state interactions are taken into
account through the Kpi scalar and vector form factors fulfilling analyticity,
unitarity and chiral symmetry constraints. The model has only two free
parameters that are fixed from experimental branching ratios. We show that the
modulus and phase of the S wave thus obtained agree nicely with experiment up
to 1.55 GeV. We perform Monte Carlo simulations to compare the predicted Dalitz
plot with experimental analyses. Allowing for a global phase difference between
the S and P waves of -65 degrees, the Dalitz plot of the D+ --> K- pi+ pi+
decay, the Kpi invariant mass spectra and the total branching ratio due to
S-wave interactions are well reproduced.Comment: 24 pages, 4 figures, REVTeX style. A discussion on the isospin 2
component has been included. Two references added. Published in Phys. Rev.
Constraining the Kpi vector form factor by tau---> K pi nu_tau and K_l3 decay data
A subtracted dispersive representation of the vector form factor,
, is used to fit the Belle spectrum of \tauKpi decays
incorporating constraints from results on decays. Through the use of
three subtractions, the slope and curvature of are obtained
directly from the data yielding
and . The phase-space integrals
relevant for analyses are calculated. Additionally, from the pole
position on the second Riemann sheet the mass and width of the
are found to be MeV and
MeV. Finally, we study the -wave
isospin-1/2 phase-shift and its threshold parameters.Comment: Talk presented at 15th International QCD Conference, Montpellier,
France. Submitted to Nuc. Phys. (Proc. Suppl.), 4 pages, 1 figur
Anomalous dimensions of four-quark operators and renormalon structure of mesonic two-point correlators
In this work, we calculate leading-order anomalous dimension matrices for
dimension-6 four-quark operators which appear in the operator product expansion
of flavour non-diagonal and diagonal vector and axial-vector two-point
correlation functions. The infrared renormalon structure corresponding to
four-quark operators is reviewed and it is investigated how the eigenvalues of
the anomalous dimension matrices influence the singular behaviour of the
infrared renormalon pole. It is found that compared to the large-
approximation where at most quadratic poles are present, in full QCD at
the most singular pole is more than cubic with an exponent .Comment: 19 pages, 1 figure; version to appear in JHE
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