AION/Magis

Abstract:

Following Freivogel et al we consider inflation in a predictive (or 'friendly') region of the landscape of string vacua, as modeled by Arkani-Hamed, Dimopoulos and Kachru. In such a region the dimensionful coefficients of super-renormalizable operators unprotected by symmetries, such as the vacuum energy and scalar mass-squareds are freely scanned over, and the objects of study are anthropically or 'environmentally' conditioned probability distributions for observables. In this context we study the statistical predictions of (inverted) hybrid inflation models, where the properties of the inflaton are probabilistically distributed. We derive the resulting distributions of observables, including the deviation from flatness |1-Ω|, the spectral index of scalar cosmological perturbations ns (and its scale dependence dns/dlog k), and the ratio of tensor to scalar perturbations r. The environmental bound on the curvature implies a solution to the η-problem of inflation with the predicted distribution of (1-n s) indicating values close to current observations. We find a relatively low probability (< 3%) of 'just-so' inflation with measurable deviations from flatness. Intermediate scales of inflation are preferred in these models. © SISSA 2006.

Abstract:

We describe a measurement of the top quark mass from events produced in pp̄ collisions at a center-of-mass energy of 1.96 TeV, using the Collider Detector at Fermilab. We identify tt̄ candidates where both W bosons from the top quarks decay into leptons (eν, μν, or τν) from a data sample of 360pb-1. The top quark mass is reconstructed in each event separately by three different methods, which draw upon simulated distributions of the neutrino pseudorapidity, tt̄ longitudinal momentum, or neutrino azimuthal angle in order to extract probability distributions for the top quark mass. For each method, representative mass distributions, or templates, are constructed from simulated samples of signal and background events, and parametrized to form continuous probability density functions. A likelihood fit incorporating these parametrized templates is then performed on the data sample masses in order to derive a final top quark mass. Combining the three template methods, taking into account correlations in their statistical and systematic uncertainties, results in a top quark mass measurement of 170.1±6.0(stat.)±4.1(syst.) GeV/c2. © 2006 The American Physical Society.

Abstract:

We measure the branching fraction of the top quark to longitudinally and right-handed polarized W bosons, F0 and F+, using approximately 200pb-1 of p̄p collisions collected by the CDF II detector. We analyze two quantities sensitive to the W helicity: the invariant mass of the charged lepton and the bottom-quark jet in the decay t→Wb→ νb (where =e or μ), and the transverse momentum of the charged lepton. Constrained fits yield F0=0.74-0.34+0.22, and F+<0.27 at the 95% confidence level. These measurements are consistent with the standard model predictions. © 2006 The American Physical Society.

Abstract:

We report the first observation of Bs0→ψ(2S) decay in pp̄ collisions at s= 1.96 TeV using 360 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron. We observe 20.2±5.0 and 12.3±4.1 Bs0→ψ(2S) candidates, in ψ(2S)→μ+μ- and ψ(2S)→J/ψπ+π- decay modes, respectively. We present a measurement of the relative branching fraction B(Bs0→ψ(2S) /B(Bs0→J/ψ)=0.52±0.13(stat)±0.04(syst)±0.06(BR) using the ψ(2S)→μ+μ- decay mode. © 2006 The American Physical Society.