116 research outputs found
NLO Standard model effective field theory for Higgs and EW precision data
A set of constructs, definitions, and propositions that present a systematic
view of the Standard Model Effective Field Theory (SMEFT), i.e. how the
influence of higher energy processes is localizable in a few structural
properties which can be captured by a handful of Wilson coefficients.Comment: Proceedings for Loops and Legs in Quantum Field Theory, 24-29 April
2016, Leipzig, German
Through precision straits to next standard model heights
After the LHC Run 1, the standard model (SM) of particle physics has been
completed. Yet, despite its successes, the SM has shortcomings vis-\`{a}-vis
cosmological and other observations. At the same time, while the LHC restarts
for Run 2 at 13 TeV, there is presently a lack of direct evidence for new
physics phenomena at the accelerator energy frontier. From this state of
affairs arises the need for a consistent theoretical framework in which
deviations from the SM predictions can be calculated and compared to precision
measurements. Such a framework should be able to comprehensively make use of
all measurements in all sectors of particle physics, including LHC Higgs
measurements, past electroweak precision data, electric dipole moment, ,
penguins and flavor physics, neutrino scattering, deep inelastic scattering,
low-energy scattering, mass measurements, and any search for
physics beyond the SM. By simultaneously describing all existing measurements,
this framework then becomes an intermediate step, pointing us toward the next
SM, and hopefully revealing the underlying symmetries. We review the role that
the standard model effective field theory (SMEFT) could play in this context,
as a consistent, complete, and calculable generalization of the SM in the
absence of light new physics. We discuss the relationship of the SMEFT with the
existing kappa-framework for Higgs boson couplings characterization and the use
of pseudo-observables, that insulate experimental results from refinements due
to ever-improving calculations. The LHC context, as well as that of previous
and future accelerators and experiments, is also addressed.Comment: 19 pages, 3 figure
How well can we guess theoretical uncertainties?
The problem of estimating the effect of missing higher orders in perturbation
theory is analyzed with emphasis in the application to Higgs production in
gluon-gluon fusion. Well-known mathematical methods for an approximated
completion of the perturbative series are applied with the goal to not truncate
the series, but complete it in a well-defined way, so as to increase the
accuracy - if not the precision - of theoretical predictions. The uncertainty
arising from the use of the completion procedure is discussed and a recipe for
constructing a corresponding probability distribution function is proposed
Large-Angle Bhabha Scattering at LEP 1
A critical assessment is given of the theoretical uncertainty in the
predicted cross-sections for large-angle Bhabha scattering at LEP 1, with or
without t-channel subtraction. To this end a detailed comparison is presented
of the results obtained with the programs ALIBABA and TOPAZ0. Differences in
the implementation of the radiative corrections and the effect of missing
higher-order terms are critically discussed.Comment: 10 pages, Late
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