0000000000953403
AUTHOR
Germán Vicente Rodrigo García
Radiative return at NLO and the measurement of the hadronic cross-section
The measurement of the hadronic cross-section in e+e− annihilation at high luminosity factories using the radiative return method is motivated and discussed. A Monte Carlo generator which simulates the radiative process e+e−→γ+hadrons at the next-to-leading order accuracy is presented. The analysis is then extended to the description of events with hard photons radiated at very small angle.
Oriented event shapes at (NLL)-L-3 + O(alpha(2)(S))
We analyze oriented event-shapes in the context of Soft-Collinear Effective Theory (SCET) and in fixed-order perturbation theory. Oriented event-shapes are distributions of event-shape variables which are differential on the angle theta(T) that the thrust axis forms with the electron-positron beam. We show that at any order in perturbation theory and for any event shape, only two angular structures can appear: F-0 = 3/8 (1+cos(2) theta(T)) and F-1 = (1 ¿ 3 cos(2) theta(T)). When integrating over theta(T) to recover the more familiar event-shape distributions, only F-0 survives. The validity of our proof goes beyond perturbation theory, and hence only these two structures are present at the …
PHOKHARA, the radiative return and the (g-2)(mu) puzzle
The radiative return has proven to be a competitive method for the precise measurement of the hadronic cross section, detailed studies of hadronic interactions, and even discoveries of new resonances. The most recent and future devolopments of the Monte Carlo event generator PHOKHARA are highlighted, and the impact of the radiative return measurements on the (g−2)μ puzzle is discussed.
Perspectives from the radiative return at meson factories
The measurement of the pion form factor and, more generally, of the cross section for electron-positron annihilation into hadrons through the radiative return has become an important task for high luminosity colliders such as the Phi- or B-meson factories. This quantity is crucial for predictions of the hadronic contributions to the anomalous magnetic moment of the muon, and to the running of the electromagnetic coupling. But the radiative return opens the possibility of many other physical applications. The physics potential of this method at high luminosity meson factories is discussed, the last upgraded version of the event generator PHOKHARA is presented, and future developments are hig…
Do the quark masses run? Extracting (m)over-bar(b)(m(Z)) from CERN LEP data
We present the first results of next-to-leading order QCD corrections to three jet heavy quark production at LEP including mass effects. Among other applications, this calculation can be used to extract the bottom quark mass from LEP data, and therefore to test the running of masses as predicted by QCD.
Heavy colored resonances in t(t)over-bar + jet at the LHC
The LHC is the perfect environment for the study of new physics in the top quark sector. We study the possibility of detecting signals of heavy color-octet vector resonances, through the charge asymmetry, in t (t) over bar + jet events. Besides contributions with the t (t) over bar pair in a color-singlet state, the asymmetry gets also contributions which are proportional to the color factor f(abc)(2). This process is particularly interesting for extra-dimensional models, where the inclusive charge asymmetry generated by Kaluza-Klein excitations of the gluon vanishes at the tree level. We find that the statistical significance for the measurement of such an asymmetry is sizable for differen…
Proton stability, dark matter and light color octet scalars in adjoint SU(5) unification
The unification of gauge interactions in the context of Adjoint SU(5) and its phenomenological consequences are investigated. We show the allowed mass spectrum of the theory which is compatible with proton decay, and discuss the possibility to have a cold dark matter candidate. Due to the upper bounds on the proton decay partial lifetimes, tau (p --> K^+ nubar) pi^+ nubar) < 3.0 10^{35} years, the theory could be tested at future proton decay experiments. The theory predicts also light scalar color octets which could be produced at the Large Hadron Collider.
NLO QED corrections to ISR in e+ e- annihilation and the measurement of σ(e+ e- \to hadrons) using tagged photons
The leptonic tensor for the process e+e−→γ+γ∗, which describes the next-to-leading order virtual and soft QED corrections to initial state radiation in e+e− annihilation with emission of an extra virtual photon decaying into hadrons, is calculated. A Monte Carlo generator for the reaction e+e−→γ+π+π− has been set up which includes these corrections. It thus describes configurations where the invariant mass of the hadrons plus photon is very close to s√. Predictions for cms energies of 1 to 10 GeV, corresponding to the energies of DAPHNE and B-meson factories, are presented. The possibility for an accurate measurement using tagged photons of σ(e+e−→hadrons), which plays an important role in …
Boosted objects and jet substructure at the LHC
This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure. We discuss the potential of first-principle QCD calculations to yield a precise description of the substructure of jets and study the accuracy of state-of-the-art Monte Carlo tools. Limitations of the experiments' ability to resolve substructure are evaluated, with a focus on the impact of additional (pile-up) proton proton collisions on jet substructure performance in future LHC operating scenarios. A final section summarizes the lessons learnt from jet substructure analyses in searches for new physics in the production of boosted top quarks.