Future Colliders

Abstract:

A critical review is given of the current status of cosmological nucleosynthesis. In the framework of the Standard Model with 3 types of relativistic neutrinos, the baryon-to-photon ratio, $\eta$, corresponding to the inferred primordial abundances of deuterium and helium-4 is consistent with the independent determination of $\eta$ from observations of anisotropies in the cosmic microwave background. However the primordial abundance of lithium-7 inferred from observations is significantly below its expected value. Taking systematic uncertainties in the abundance estimates into account, there is overall concordance in the range $\eta = (5.7-6.7)\times 10^{-10}$ at 95% CL (corresponding to a cosmological baryon density $\Omega_B h^2 = 0.021 - 0.025$). The D and He-4 abundances, when combined with the CMB determination of $\eta$, provide the bound $N_\nu=3.28 \pm 0.28$ on the effective number of neutrino species. Other constraints on new physics are discussed briefly.

Abstract:

The inclusive cross section for top-quark pair production measured by the CMS experiment in proton-proton collisions at a center-of-mass energy of 7 TeV is compared to the QCD prediction at next-to-next-to-leading order with various parton distribution functions to determine the top-quark pole mass, m t pole , or the strong coupling constant, α S . With the parton distribution function set NNPDF2.3, a pole mass of 176. 7 +3.8 -3.4 GeV is obtained when constraining α S at the scale of the Z boson mass, m Z , to the current world average. Alternatively, by constraining m t pole to the latest average from direct mass measurements, a value of α S (m Z ) = 0. 1151 +0.0033 -0.0032 is extracted. This is the first determination of α S using events from top-quark production. © 2013 The Authors. Published by Elsevier B.V.