Electroweak Corrections at the LHC with MCFM.
Electroweak Corrections at the LHC with MCFM.

Author:

Publisher:

Published: 2015

Total Pages:

ISBN-13:

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Electroweak (EW) corrections at the LHC can be enhanced at high energies due to soft/collinear radiation of W and Z bosons, being dominated by Sudakov-like corrections in the form of $\alpha_W^l\log^n(Q^2/M_W^2)$ $(n \le 2l, \alpha_W = \alpha/(4\pi\sin\theta_W^2))$ when the energy scale $Q$ enters the TeV regime. Thus, the inclusion of EW corrections in LHC predictions is important for the search of possible signals of new physics in tails of kinematic distributions. EW corrections should also be taken into account in virtue of their comparable size ($\mathcal{O}(\alpha)$) to that of higher order QCD corrections ($\mathcal{O}(\alpha_s^2)$). We calculated the next-to-leading-order (NLO) weak corrections to the neutral-current (NC) Drell-Yan process, top-quark pair production and di-jet producion, and implemented them in the Monte-Carlo program MCFM. This enables a combined study with the corresponding NLO QCD corrections. We provide both the full NLO weak corrections and their weak Sudakov approximation valid at high energies. The latter is often used for a fast evaluation of weak effects, and having the exact result available as well allows to quantify the validity of the Sudakov approximation.

Electroweak Physics at LEP and LHC
Electroweak Physics at LEP and LHC

Author: Arno Straessner

Publisher: Springer

Published: 2010-03-14

Total Pages: 222

ISBN-13: 3642051693

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During more than 10 years, from 1989 until 2000, the LEP accelerator and the four LEP experiments, ALEPH, DELPHI, L3 and OPAL, have taken data for a large amount of measurements at the frontier of particle physics. The main outcome is a thorough and successful test of the Standard Model of electroweak interactions. Mass and width of the Z and W bosons were measured precisely, as well as the Z and photon couplings to fermions and the couplings among gauge bosons. The rst part of this work will describe the most important physics results of the LEP experiments. Emphasis is put on the properties of the W boson, which was my main research eld at LEP. Especially the precise determination of its mass and its couplings to the other gauge bosons will be described. Details on physics effects like Colour Reconnection and Bose-Einstein Correlations in W-pair events shall be discussed as well. A conclusive summary of the current electroweak measurements, including low-energy results, as the pillars of possible future ndings will be given. The important contributions from Tevatron, like the measurement of the top quark and W mass, will round up the present day picture of electroweak particle physics. This is an open access book.

Electroweak Corrections Using Effective Theory
Electroweak Corrections Using Effective Theory

Author: Jui-Yu Chiu

Publisher:

Published: 2009

Total Pages: 104

ISBN-13:

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We study the infrared structure of perturbative amplitudes using the effective field theory (EFT) formalism and develop a general factorization scheme, frst for electroweak dynamics and then general gauge theories. We begin by discussing the factorization structure within the framework of the Soft-Collinear-Effective Theory. For the theories with a massive gauge boson, we introduce a (new) [Delta]-regulator to regulate the collinear singularities. In this way, we avoid the confusions in distinguishing different kinds of singularities which arise when considering unbroken theories. Consequently, we propose a factorization scheme to define a soft function free of collinear singularities and a jet function free of the soft singularities. We also clarify that heavy-quark effects change only the structure of collinear singularities and not the soft ones. With our definition of the soft function, we compute the one-loop soft anomalous dimension matrix for any fixed angle, multi-particle process by weighting the soft function with the proper group theory factor without additional calculation. Next, we use EFT methods to sum the Electroweak Sudakov logarithms at high energy, of the form ([alpha]/sin2 [theta]w log^m s/M_{Z, W}^2, are summed using effective theory (EFT) methods. The exponentiation of Sudakov logarithms and factorization is discussed in the EFT formalism. Radiative corrections are computed to scattering processes in the standard model involving an arbitrary number of external particles. The computations include non-zero particle masses such as the t-quark mass, electroweak mixing effects which lead to unequal W and Z masses and a massless photon, and Higgs corrections proportional to the top quark Yukawa coupling. The structure of the radiative corrections, and which terms are summed by the EFT renormalization group is discussed in detail. The omitted terms are smaller than 1%. We give numerical results for the corrections to dijet production, dilepton production, t-bar t production, and squark pair production. The purely electroweak corrections are significant -- about 15% at 1 TeV, increasing to 30% at 5 TeV, and they change both the scattering rate and angular distribution. The QCD corrections (which are well-known) are also computed with the EFT. They are much larger -- about a factor of four at 1 TeV, increasing to a factor of thirty at 5 TeV.