212 research outputs found
Top Quark Production at Hadron Colliders: an Overview
The study of the properties of the top quark is one of the main goals of the
Large Hadron Collider (LHC) physics program. The experimental precision
expected at the LHC requires the calculation of several top-quark related
observables beyond leading order in the strong coupling constant. In this work
we briefly review the status of the theoretical predictions for the top-quark
production processes at hadron colliders. Special attention is devoted to
recent progress in the calculation of next-to-next-to-leading-order corrections
to the top-quark pair production cross section.Comment: Submitted to the proceedings of "The 2009 Europhysics Conference on
High Energy Physics", July 16 - 22, 2009, Krakow, Poland. References adde
Two-Loop QED Heavy-Flavor Contribution to Bhabha Scattering
We briefly review the status of the calculation of next-to-next-to-leading
order corrections to large angle Bhabha scattering in pure QED. In particular,
we focus on the analytic calculation of the two-loop virtual corrections
involving a heavy-flavor fermion loop, which was recently completed. We
conclude by assessing the numerical impact of these corrections on the Bhabha
scattering cross section at colliders operating at a center of mass energy of 1
GeV and at the future ILC.Comment: 6 pages, 2 figures. Contribution to the Proceedings of the 9th DESY
workshop on "Loops and Legs in Quantum Field Theory", Sondershausen, April
2008. References adde
Search for fermiophobic Higgs bosons in final states with photons at LEP 2
Higgs boson production with subsequent decay to photons was searched for in
the data collected by the DELPHI detector at centre-of-mass energies between
183 GeV and 209 GeV, corresponding to a total integrated luminosity of nearly
650 pb^{-1}. No evidence for a signal was found, and limits were set on h0Z0
and h0A0 production with h0 decay to photons. These results were used to
exclude regions in the parameter space of fermiophobic scenarios of Two Higgs
Doublet Models.Comment: 24 pages, 6 figures, Accepted by Eur. Phys. J.
Topics in Electroweak Physics
We briefly discuss five topics in Precision Electroweak Physics: i) the
recently proposed Effective Scheme of Renormalization, ii) evidence for
electroweak bosonic corrections derived from the radiative correction
Delta_r_eff, iii) an approach to estimate the scale of new physics in a
hypothetical Higgs-less scenario, iv) simple and accurate formulae for s^2_eff,
M_W, Gamma_l, and their physical applications, v) a recent proposal concerning
the field renormalization constant for unstable particles.Comment: 5 pages, talk presented at the International Symposium Radcor 2002,
September 8-13, Kloster Banz, German
Two-Loop Corrections to Top-Antitop Production at Hadron Colliders
The status of the theoretical predictions for the top-anti top production in
hadronic collisions is shortly reviewed, paying a articular attention to the
analytic calculation of the two-loop QCD corrections to the parton-level matrix
elements.Comment: Talk presented at the 35th International Conference of High Energy
Physics - ICHEP2010, July 22-28, 2010, Paris Franc
The electroweak form factor \hat{\kappa}(q^2) and the running of \sin^2 \hat{\theta}_W
Gauge independent form factors \rho^(e; e) and \hat{\kappa}^(e; e)(q^2) for
Moller scattering at s << m_W^2 are derived. It is pointed out that
\hat{\kappa}^(e; e) is very different from its counterparts in other processes.
The relation between the effective parameter \hat{\kappa}^(e; e)(q^2,\mu)
\sin^2 \hat{\theta}_W(\mu) and \sin^2 \theta_eff is derived in a
scale-independent manner. A gauge and process-independent running parameter
\sin^2 \hat{\theta}_W (q^2), based on the pinch-technique self-energy a_{\gamma
Z} (q^2), is discussed for all q^2 values. At q^2=0 it absorbs very accurately
the Czarnecki-Marciano calculation of the Moller scattering asymmetry at low s
values, and at q^2 = m^2_Z it is rather close to \sin^2 \theta_eff. The q^2
dependence of \sin^2 \hat{\theta}_W (q^2) is displayed in the space and
time-like domains.Comment: A new paragraph has been inserted at the beginning of the discussion
in Section
Top-quark production at hadron colliders
The current theoretical predictions for the observables related to the
top-quark pair and the single-top productions at hadron colliders are briefly
reviewed. The theoretical predictions are compared to the experimental
measurements carried out at the Tevatron and the LHC.Comment: To appear in the proceedings of the XXIst International Europhysics
Conference on High Energy Physics, EPS-HEP2011. Extended version. 12 page
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