616 research outputs found
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
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
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
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.
Differential temperature stress measurement employing array sensor with local offset
The instrument has a focal plane array of infrared sensors of the integrating type such as a multiplexed device in which a charge is built up on a capacitor which is proportional to the total number of photons which that sensor is exposed to between read-out cycles. The infrared sensors of the array are manufactured as part of an overall array which is part of a micro-electronic device. The sensor achieves greater sensitivity by applying a local offset to the output of each sensor before it is converted into a digital word. The offset which is applied to each sensor will typically be the sensor's average value so that the digital signal which is periodically read from each sensor of the array corresponds to the portion of the signal which is varying in time. With proper synchronization between the cyclical loading of the test object and the frame rate of the infrared array the output of the A/D converted signal will correspond to the stress field induced temperature variations. A digital lock-in operation may be performed on the output of each sensor in the array. This results in a test instrument which can rapidly form a precise image of the thermoelastic stresses in an object
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