5,683 research outputs found
Strong linear polarization of V4332 Sgr: a dusty disc geometry
The eruption of V4332 Sgr was observed in 1994. During the outburst, the
object became extremely red, so it is considered as belonging to luminous red
transients of the V838 Mon type. It has recently been suggested that the
central object in V4332 Sgr is now hidden in a dusty disc and that the
photospheric spectrum of this object observed in the optical results from
scattering the central star radiation on dust grains in the disc. One expects
significant polarization of the spectrum in this case. We investigate this
prediction. We present and analyse polarimetric observations of V4332 Sgr in
the V and R photometric bands done with the NOT telescope. The optical light of
V4332 Sgr is linearly polarized with a degree of ~26% in the V band and ~11% in
R. Discussion of the observed polarization leads us to conclude that the
photospheric spectrum observed in V4332 Sgr is probably produced by dust
scattering not only in the disc but also in the outflow from the object seen in
the emission features.Comment: accepted in Astronomy & Astrophysics as a research not
New Solutions for Scalar-Isoscalar pi-pi Phase Shifts
The scalar-isoscalar pi-pi phase shifts are calculated in the pi-pi energy
range from 600 MeV to 1600 MeV. We use results of the CERN-Cracow-Munich
collaboration for the reaction pi^- p --> pi^+ pi^- n on a transversely
polarized target at 17.2 GeV/c pi^- momentum. Energy-independent separation of
the S-wave pseudoscalar amplitude (pi exchange) from the pseudovector amplitude
(a_1 exchange) is carried out. Below the KK threshold we find two solutions for
the pi-pi phase shifts, for which the phases increase slower with the effective
pi-pi mass than the P-wave phases ("flat" solutions) and two solutions for
which the phases increase faster than the P-wave phases ("steep" solutions).
Above 1420 MeV both sets of phase shifts increase with energy faster than in
the experiment on an unpolarized target. This fact can be related to a presence
of the scalar resonance f_0(1500).Comment: 5 pages, 2 figures. Talk given at 7th International Conference on
Hadron Spectroscopy (Hadron 97), Upton, NY, 25-30 Aug 199
Roy's equations and the pion-pion experimental data
Roy's equations are used to check if the scalar-isoscalar pion-pion
scattering amplitudes fitted to experimental data fulfill crossing symmetry
conditions. It is shown that the amplitudes describing the ``down-flat'' phase
shift solution satisfy crossing symmetry below 1 GeV while the amplitudes
fitted to the "up-flat'' data do not. In this way the long standing "up-down"
ambiguity in the phenomenological determination of the scalar-isoscalar
pion-pion amplitudes has been resolved confirming the independent result of the
recent joint analysis of the pi+pi- and pi0pi0 data.Comment: 6 pages, 2 figures, talk given at Tenth International Conference on
Hadron Spectroscopy (Hadron'03), Aschaffenburg, Germany, August 31 -
September 6 200
Peculiarities in multichannel interaction amplitudes for meson-meson scattering and scalar meson spectroscopy
Interactions in coupled channels pipi, KKbar and an effective 2pi2pi in
scalar-isoscalar wave have been analysed. Influence of interchannel couplings
on analytical structure of multichannel interaction amplitudes has been
studied. Interplay of S-matrix zeroes and poles and their relation with
parameters of scalar resonances has been investigated.Comment: presented by R. Kaminski at the Meson 2000 Conference, Cracow,
Poland, May 19-23, 2000; 5 pages including 2 figures, to appear in Acta
Physica Polonica
Analysis of New Results For Scalar-Isoscalar pi-pi Phase Shifts
The scalar -- isoscalar pi-pi phase shifts are analysed using a separable
potential model of three coupled channels (pipi, KK and an effective 2pi2pi
system). Model parameters are fitted to two sets of solutions obtained in a
recent analysis of the CERN-Cracow-Munich measurements of the pi^- p --> pi^+
pi^- n reaction on a polarized target. A relatively narrow (90 -- 180 MeV)
scalar resonance f_0(1400-1460) is found, together with a wide f_0(500) (Gamma
= 500 MeV) and the narrow f_0(980) state.Comment: 4 pages, 3 figures. Talk given at 7th International Conference on
Hadron Spectroscopy (Hadron 97), Upton, NY, 25-30 Aug 199
pi-pi scattering amplitudes constrained by Roy's equations
The scalar-isoscalar, scalar-isotensor and vector-isovector pi-pi amplitudes
have been fitted simultaneously to experimental data and to to Roy's equations.
Resulting pi-pi phase shifts up to 1600 MeV and near threshold observables have
been analyzed. Only the amplitudes fitted to the "down-flat" set of phase
shifts in scalar-isoscalar wave fulfill crossing symmetry conditions and can be
regarded as physical.Comment: 4 pages, talk presented at 12th International QCD Conference (QCD05)
4-9th July 2005 Montpellier (France), to appear in Nucl. Phys. B (Proc.
Suppl.
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