3,927 research outputs found

### Masses and widths of the rho(770)

Isospin violation in the $\rho(770)$ mass and width is considered within the
$S$ matrix approach using combined fits to the $e^+e^- \to\pi^+\pi^-$ and
$\tau^- \to \nu_{\tau}\pi^-\pi^0$ data performed by the ALEPH collaboration. We
show that the pole position following from the parameters obtained from the
ALEPH fits are not sensitive to the details of the parametrization. In this
context, we have found that the pole mass difference and the pole width
difference between the charged and neutral $\rho$ are consistent with zero. We
show that a one loop calculation including vector, axial vector and
pseudo-scalar mesons can satisfactorily describe the observed isospin breaking.
We also give an estimate for the mass difference between the neutral and
charged states of the $a_1(1260)$.Comment: 8 pages, 1 figur

### On Scale Invariance and Anomalies in Quantum Mechanics

We re-consider the quantum mechanics of scale invariant potentials in two
dimensions. The breaking of scale invariance by quantum effects is analyzed by
the explicit evaluation of the phase shift and the self-adjoint extension
method. We argue that the breaking of scale invariance reported in the
literature for the $\delta$(r) potential, is an example of explicit and not an
anomaly or quantum mechanical symmetry breaking.Comment: 15 pp in latex, no figure

### Tests of flavor symmetry in J/psi decays

We use SU(3) flavor symmetry to analyze the $PP', VP$ and baryon-antibaryon
decays of $J/\psi$. Both, the SU(3)-invariant and -violating contributions are
considered. Particular attention is paid to the interference of the
electromagnetic and strong amplitudes.Comment: 8 pages, latex. Talk given at CAM-94 Physics Meetin

### Pion Scattering Revisited

Chiral Ward identities lead to consistent accounting for the sigma's width in
the linear sigma model's Feynman rules. Reanalysis of pion scattering data at
threshold imply a mass for the sigma of 600+ 200 - 100 MeV.Comment: latex; VIII EMPC (Oaxaca, Nov 98) Proceeding

### Effective SU(2)_L x U(1) theory and the Higgs boson mass

We assume the stability of vacuum under radiative corrections in the context
of the standard electroweak theory. We find that this theory behaves as a good
effective model already at cut off energy scales as low as 0.7 TeV. This
stability criterion allows to predict m_H= 318 +- 13 GeV for the Higgs boson
mass.Comment: Latex, 5 pages, 1 Postscript figure include

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