This work aims at developing a generic virtual source model (VSM) preserving all existing correlations between variables stored in a Monte Carlo pre-computed phase space (PS) file, for dose ...calculation and high-resolution portal image prediction. The reference PS file was calculated using the PENELOPE code, after the flattening filter (FF) of an Elekta Synergy 6 MV photon beam. Each particle was represented in a mobile coordinate system by its radial position (rs) in the PS plane, its energy (E), and its polar and azimuthal angles ( d and θd), describing the particle deviation compared to its initial direction after bremsstrahlung, and the deviation orientation. Three sub-sources were created by sorting out particles according to their last interaction location (target, primary collimator or FF). For each sub-source, 4D correlated-histograms were built by storing E, rs, d and θd values. Five different adaptive binning schemes were studied to construct 4D histograms of the VSMs, to ensure histogram efficient handling as well as an accurate reproduction of E, rs, d and θd distribution details. The five resulting VSMs were then implemented in PENELOPE. Their accuracy was first assessed in the PS plane, by comparing E, rs, d and θd distributions with those obtained from the reference PS file. Second, dose distributions computed in water, using the VSMs and the reference PS file located below the FF, and also after collimation in both water and heterogeneous phantom, were compared using a 1.5%-0 mm and a 2%-0 mm global gamma index, respectively. Finally, portal images were calculated without and with phantoms in the beam. The model was then evaluated using a 1%-0 mm global gamma index. Performance of a mono-source VSM was also investigated and led, as with the multi-source model, to excellent results when combined with an adaptive binning scheme.
Abstract The purpose is to evaluate canal transportation of a new heat-treated NiTi system, the Endostar E3 Azure operated in continuous rotation or reciprocation. 40 resin blocks were divided into ...two groups. The first was shaped in continuous rotation while the second in reciprocation. A preoperative and two postoperative images were taken, one after the use of the 20/06 and one after the 25/06. The images were superimposed to determine canal transportation. Time required for canal shaping was recorded. One-sample and student t tests, repeated-measure analyses of variance, univariate analyses and Bonferroni multiple comparisons tests were used for statistical analysis. The significance level was set at p<0.05. There was no significant difference between continuous and reciprocating motion with the 20/06 and 25/06, respectively, at 1mm (p=0.761, p=0.559), 2mm (p=0.584, p=0.810) and 3mm (p=0.651, p=0.070). The reciprocating motion showed significantly less canal transportation at 5mm (p=0.049, p<0.001) and 7mm (p<0.001, p<0.001) for the 20/06 and 25/0.6. Continuous rotation was more time-consuming than reciprocation (p<0.001). The Endostar E3 Azure in reciprocation respected the original canal curvature better than in continuous rotation at all levels, and required less time to prepare artificial curved canals. Endodontists should know the shaping abilities of novel heat-treated NiTi files, regarding canal transportation and its relation with the instruments' motion and apical diameter enlargement.
We present a measurement of the ratio of events with correlated t and t spins to the total number of tt events. This ratio f is evaluated using a matrix-element-based approach in 729 tt candidate ...events with a single lepton ℓ (electron or muon) and at least four jets. The analyzed pp collisions data correspond to an integrated luminosity of 5.3 fb-1 and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy \(\sqrt{s}=1.96\) TeV. Combining this result with a recent measurement of f in dileptonic final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in tt events with a significance of more than 3 standard deviations.
We present searches for the anomalous γWW and ZWW trilinear gauge boson couplings from WW and WZ production using lepton plus dijet final states and a combination with results from Wγ, WW, and WZ ...production with leptonic final states. The analyzed data correspond to up to 8.6fb -1 of integrated luminosity collected by the D0 detector in pp- collisions at s=1.96TeV. We set the most stringent limits at a hadron collider to date assuming two different relations between the anomalous coupling parameters δκ γ, λ, and δg1Z for a cutoff energy scale Λ=2TeV. The combined 68% C.L. limits are -0.057&lt;δκ γ&lt;0.154, -0.015&lt;λ&lt;0.028, and -0.008&lt;δg1Z&lt;0.054 for the LEP parameterization, and -0.007&lt;δκ&lt;0.081 and -0.017&lt;λ&lt;0.028 for the equal couplings parameterization. We also present the most stringent limits of the W boson magnetic dipole and electric quadrupole moments.
We use higher-order quantum chromodynamics calculations to extract the mass of the top quark from the t (t) over bar cross section measured in the lepton + jets channel in p (p) over bar collisions ...at root s = 1.96 TeV using 5.3 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. The extracted top quark pole mass and (MS) over bar mass are compared to the current Tevatron average top quark mass obtained from direct measurements.
We present measurements of the differential cross section dσ/dpTγ for the associated production of a c-quark jet and an isolated photon with rapidity |yγ|<1.0 and transverse momentum 30<pTγ<300 GeV. ...The c-quark jets are required to have |yjet|<1.5 and pTjet>15 GeV. The ratio of differential cross sections for γ+c to γ+b production as a function of pTγ is also presented. The results are based on data corresponding to an integrated luminosity of 8.7 fb−1 recorded with the D0 detector at the Fermilab Tevatron pp¯ Collider at s=1.96 TeV. The obtained results are compared to next-to-leading order perturbative QCD calculations using various parton distribution functions, to predictions based on the kT-factorization approach, and to predictions from the sherpa and pythia Monte Carlo event generators.
We present a measurement of the a production cross section sigma((u) over bar) in p (p) over bar collisions at root s = 1.96 TeV using 5.4 fb(-1) of integrated luminosity collected with the D0 ...detector. We consider final states with at least two jets and two leptons (ee, e mu, mu mu), and events with one jet for the e mu final state as well. The measured cross section is sigma((u) over bar) = 7.36(-0.79)(+0.90)(stat + syst) pb. This result combined with the cross section measurement in the lepton + jets final state yields sigma((u) over bar) = 7.56(-0.56)(+0.63)(stat + syst) pb, which agrees with the standard model expectation. The relative precision of 8% of this measurement is comparable to the precision of the latest theoretical calculations. (C) 2011 Elsevier B.V. All rights reserved.
Using 7.3 fb(-1) of p (p) over bar collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable phi(eta)*, which probes the same physical effects as ...the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the phi(eta)* distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.
We measure the correlation between the spin of the top quark and the spin of the anti-top quark in t (t) over bar -> W(+)bW(-)(b) over bar -> l(+)vbl(-) (v) over bar(b) over bar final states ...produced in p (p) over bar collisions at a center of mass energy root s = 1.96 TeV, where l is an electron or muon. The data correspond to an integrated luminosity of 5.4 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider. The correlation is extracted from the angles of the two leptons in the t and (t) over bar rest frames, yielding a correlation strength C = 0.10(-0.45)(+0.45). in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.
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