Image viewing and processing software in computed radiography manipulates image contrast in such a way that all relevant image features are rendered to an appropriate degree of visibility, and ...improves image quality using enhancement algorithms. The purpose of this study was to investigate procedures for the quality assessment of image processing software for computed radiography with the use of existing test objects and to assess the influence that processing introduces on physical image quality characteristics. Measurements of high-contrast resolution, low-contrast resolution, spatial resolution, greyscale (characteristic curve) and geometric distortion were performed ‘subjectively’ by three independent observers and ‘objectively’ by the use of criteria based on pixel intensity values. Results show quality assessment is possible without the need for human evaluators, using digital images. It was discovered that the processing software evaluated in this study was able to improve some aspects of image quality, without introducing geometric distortion.
A search for charginos with masses close to the mass of the lightest neutralino is reported, based on the data collected with the DELPHI detector at LEP from 1995 to 1997 at centre-of-mass energies ...between 130 and 183 GeV. The signature of a photon at high transverse momentum radiated from the initial state reduces the two-photon background to acceptable rates, thus making the mass differences between a few hundred MeV/c$^2$ and 3~GeV/c$^2$ detectable. In very nearly degenerate scenarios, the lifetime of the chargino can be large enough to produce either visible secondary vertices or decays outside the detector; therefore, quasi-stable heavy charged particles and displaced decay vertices were also searched for. No excess of events with respect to the Standard Model expectations was observed, and limits in the plane of chargino-neutralino mass difference versus chargino mass are given.
A new precise measurement of |V_{cb}| and of the branching ratio BR(\bar{B^0} -> D^{*+} \ell^- \bar{\nu_\ell}) has been performed using a sample of about 5000 semileptonic decays \bar{B^0} -> D^{*+} ...\ell^- \bar{\nu_\ell}, selected by the DELPHI detector at LEP I by tagging the soft pion from D^{*+} -> D^0 \pi^+. The results are: V_{cb}=(39.0 +/- 1.5 (stat.) ^{+2.5}_{-2.6} (syst. exp.) +/- 1.3 (syst. th.)) x 10^{-3} BR(\bar{B^0} -> D^{*+} \ell^- \bar{\nu_\ell})=(4.70 +/- 0.13 (stat.) ^{+0.36} _{-0.31} (syst. exp.))% The analytic dependences of the differential cross-section and of the Isgur Wise form factor as functions of the variable w = v_{B^0}.v_{D^*} have also been obtained by unfolding the experimental resolution.
The cross sections for the production of single charged and neutral intermediate vector bosons were measured using integrated luminosities of 52 pb–1 and 154 pb–1 collected by the experiment at ...centre-of-mass energies of 182.6 GeV and 188.6 GeV, respectively. The cross sections for the reactions were determined in limited kinematic regions. The results found are in agreement with the Standard Model predictions for these channels.
A measurement of the W mass and width has been performed by the DELPHI Collaboration using the data collected during 1998. The data sample has an integrated luminosity of 155 pb
−1 and an average ...centre-of-mass energy of 188.6 GeV. Results are obtained by applying the method of direct reconstruction of the mass of the W from its decay products in both the
W
+W
−
→
ℓ
ν
̄
ℓ
q
q
̄
′
and
W
+W
−
→
q
q
̄
′
q
̄
q′
channels. The W mass result for the 1998 data set is
M
W=80.387±0.087(stat)±0.034(syst)±0.017(LEP)±0.035(FSI) GeV/
c
2, where FSI represents the uncertainty due to final state interaction effects in the
q
q
̄
′
q
̄
q′
channel, and LEP represents that arising from the knowledge of the beam energy of the accelerator. Combining this result with those previously published by the DELPHI Collaboration gives the result
M
W=80.359±0.074(stat)±0.032(syst)±0.017(LEP)±0.033(FSI) GeV/
c
2. The combined value for the W width is
Γ
W=2.266±0.176(stat)±0.056(syst)±0.052(FSI) GeV/
c
2.
Searches for spontaneous $R$-parity violating signals at $\sqrt{s}=183$\,GeV and \mbox{$\sqrt{s}=189$\,GeV} have been performed using 1997 and 1998 DELPHI data, under the assumption of $R$-parity ...breaking in the third lepton family. The expected topology for the decay of a pair of charginos into two acoplanar taus plus missing energy was investigated and no evidence for a signal was found. The results were used to derive a limit on the chargino mass and to constrain the allowed domains of the MSSM parameter sp.
Searches for spontaneous
R-parity-violating signals at
s
=183
GeV and
s
=189
GeV have been performed using the 1997 and 1998 DELPHI data, under the assumption of
R-parity breaking in the third ...lepton family. The expected topology for the decay of a pair of charginos into two acoplanar taus plus missing energy was investigated and no evidence for a signal was found. The results were used to derive a limit on the chargino mass and to constrain the allowed domains of the MSSM parameter space.
A search for pair-production of neutralinos at a LEP centre-of-mass energy of 189 GeV gave no evidence for a signal. This limits the neutralino production cross-section and excludes regions in the ...parameter space of the Minimal Supersymmetric Standard Model (MSSM).
Searches for pair production of gauginos and squarks in
e
+
e
− collisions at a centre-of-mass energy of 189 GeV have been performed on data corresponding to an integrated luminosity of 158 pb
−1 ...collected by the DELPHI detector at LEP. The data were analyzed under the assumption of non-conservation of
R-parity through a single dominant
U
̄
D
̄
D
̄
coupling between squarks and quarks. Typical final states contain between 4 and 10 jets with or without additional leptons. No excess of data above Standard Model expectations was observed. The results were used to constrain domains of the MSSM parameter space and derive limits on the masses of supersymmetric particles. The following mass limits at 95% CL were obtained from these searches: neutralino mass:
m
χ
̃
0
1
⩾32
GeV; chargino mass:
m
χ
̃
+
1
⩾94
GeV; stop and sbottom mass (indirect decay) with
ΔM>5 GeV:
m
t
̃
1
⩾74
GeV for
Φ
mix=0 rad,
m
t
̃
1
⩾59
GeV for
Φ
mix=0.98 rad,
m
b
̃
1
⩾72
GeV for
Φ
mix=0 rad. The angle
φ
mix is the mixing angle between left and right handed quarks.
PDF
