Spin Correlation In Tanti T Production From Panti P Collisions Atradical

The Standard Model predicts that the lifetime of the top quark is shorter than the typical time scale at which hadronization process occurs, and the spin information at its production is preserved. Spin correlation of the t[anti t] system from p[anti p] collisions at the Tevatron is analyzed using 6 events in the dilepton channels collected using the D0 detector. Spin correlation factor of[kappa]>[minus] 0.25 at 68% CL is obtained from the data.

The Standard Model predicts that the lifetime of the top quark is shorter than the typical time scale at which hadronization process occurs, and the spin information at its production is preserved. Spin correlation of the t{anti t} system from p{anti p} collisions at the Tevatron is analyzed using 6 events in the dilepton channels collected using the D0 detector. Spin correlation factor of?> - 0.25 at 68% CL is obtained from the data.

We present a measurement of the ratio of events with correlated t and {bar t} spins to the total number of t{bar t} events. This ratio f is evaluated using a matrix-element-based approach in events with a single lepton (electron or muon) and at least four jets. We analyze p{bar p} collisions data corresponding to an integrated luminosity of 5.3 fb−1 collected with the D0 detector at the Fermilab Tevatron collider operating at a center of mass energy √s = 1.96 TeV. Combining this result with a recent measurement of f in t{bar t} → W+b W−{bar b} → l+ [nu]b l− {bar {nu}}b final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in t{bar t} events with a significance of more than three standard deviations.

The consistency of the spin correlation strength in top quark pair production with the standard model (SM) prediction is tested in the muon+jets final state. The events are selected from pp collisions, collected by the CMS detector, at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb-1. We then compare the data with the expectation for the spin correlation predicted by the SM and with the expectation of no correlation. Furthermore, by using a template fit method, the fraction of events that show SM spin correlations is measured to be 0.72 ±0.08 (stat)+0.15 -0.13 (syst), representing the most precise measurement of this quantity in the lepton+jets final state to date.

The authors have studied J/[psi] production in p[anti p] collisions at[radical]s= 1.8 TeV with the D0 detector at Fermilab, using a[mu][sup+][mu][sup[minus]] data sample corresponding to an integrated luminosity of 13 pb[sup[minus]1]. They have measured the inclusive J/[psi] production cross section as a function of J/[psi] transverse momentum p[sub T]. For the kinematic range p[sub T]> 8 GeV/c and[vert-bar][eta][vert-bar]