119235210
Template overlap method for massive jets
We introduce a new class of infrared safe jet observables, which we refer to as template overlaps, designed to filter targeted highly boosted particle decays from QCD jets and other background. Template overlaps are functional measures that quantify how well the energy flow of a physical jet matches the flow of a boosted partonic decay. Any region of the partonic phase space for the boosted decays defines a template. We will refer to the maximum functional overlap found this way as the template overlap. To illustrate the method, we test lowest-order templates designed to distinguish highly-boosted top and Higgs decays from backgrounds produced by event generators. For the functional overlap, we find good results with a simple construction based on a Gaussian in energy differences within angular regions surrounding the template partons. Although different event generators give different averages for our template overlaps, we find in each case excellent rejection power, especially when combined with cuts based on jet shapes. The template overlaps are capable of systematic improvement by including higher order corrections in the template phase space.
119263250
Structure of fat jets at the Tevatron and beyond
The presence of new sources of massive boosted particles associated with processes probing the electroweak scale is a logical possibility that forms a solid window towards physics beyond the standard model. Such objects when decaying into hadronic final states can easily blend with the cornucopia of jets interpolated from essentially massless fundamental QCD states. We review jet observables and algorithms that can contribute to the identification of highly boosted heavy jets and the possible searches that can make use of such substructure information. We also review previous studies by CDF of boosted massive jets and measurement of jet shape observables.
15504737
Threshold resummation for the top quark charge asymmetry
We study the QCD charge asymmetry in tt production at the Tevatron. We investigate the role of higher orders in perturbation theory by considering the resummation of potentially large logarithmic corrections that arise near partonic threshold. This requires us to employ the rapidity-dependent anomalous dimension matrices that describe color mixing due to soft-gluon emission in both quark- and gluon-initiated processes. The charge asymmetry appears directly in the resummed cross section at next-to-leading logarithm (NLL), and we find that the first-order expansion of the NLL-resummed charge asymmetry reproduces the known fixed-order result for the asymmetry well. Beyond its lowest order, the asymmetric component of the cross section is enhanced by the same leading-logarithmic threshold corrections as the total cross section. As a result, the charge asymmetry is robust with respect to the higher-order perturbative corrections generated by threshold resummation. We observe that the asymmetry increases with pair mass and with scattering angle.
121194842
Neutrino diffusion and mass ejection in protoneutron stars
We discuss the mass ejection mechanism induced by diffusion of neutrino during the early stage of the protoneutron star cooling. A dynamical calculation is employed in order to determine the amount of matter ejected and the remnant compact object mass. An equation of state considering hadronic and quark phases for the stellar dense matter was used to solve the whole time evolution of the system during the cooling phase. The initial neutrino population was obtained by considering beta equilibrium in the dense stellar matter with confined neutrinos, in the very early period of the deleptonic stage of the nascent pulsar. For specified initial configurations of the protoneutron star, we solve numerically the set of equations of motion together with neutrino diffusion through the dense stellar medium.