13 research outputs found
A Pedagogical Review of Electroweak Symmetry Breaking Scenarios
We review different avenues of electroweak symmetry breaking explored over
the years. This constitutes a timely exercise as the world's largest and the
highest energy particle accelerator, namely, the Large Hadron Collider (LHC) at
CERN near Geneva, has started running whose primary mission is to find the
Higgs or some phenomena that mimic the effects of the Higgs, i.e. to unravel
the mysteries of electroweak phase transition. In the beginning, we discuss the
Standard Model Higgs mechanism. After that we review the Higgs sector of the
Minimal Supersymmetric Standard Model. Then we take up three relatively recent
ideas: Little Higgs, Gauge-Higgs Unification, and Higgsless scenarios. For the
latter three cases, we first present the basic ideas and restrict our
illustration to some instructive toy models to provide an intuitive feel of the
underlying dynamics, and then discuss, for each of the three cases, how more
realistic scenarios are constructed and how to decipher their experimental
signatures. Wherever possible, we provide enough pedagogical details, which the
beginners might find useful.Comment: 45 pages, Review based on a series of lectures; v2: 63 pages,
substantially expanded, references added, to appear in `Reports on Progress
in Physics
Top quark physics in hadron collisions
The top quark is the heaviest elementary particle observed to date. Its large
mass makes the top quark an ideal laboratory to test predictions of
perturbation theory concerning heavy quark production at hadron colliders. The
top quark is also a powerful probe for new phenomena beyond the Standard Model
of particle physics. In addition, the top quark mass is a crucial parameter for
scrutinizing the Standard Model in electroweak precision tests and for
predicting the mass of the yet unobserved Higgs boson. Ten years after the
discovery of the top quark at the Fermilab Tevatron top quark physics has
entered an era where detailed measurements of top quark properties are
undertaken. In this review article an introduction to the phenomenology of top
quark production in hadron collisions is given, the lessons learned in Tevatron
Run I are summarized, and first Run II results are discussed. A brief outlook
to the possibilities of top quark research a the Large Hadron Collider,
currently under construction at CERN, is included.Comment: 84 pages, 32 figures, accepted for publication by Reports on Progress
in Physic
Light 'Higgs', yet strong interactions
The claimed finding of a light Higgs boson makes the minimal Standard Model unitary. Yet, we recall that the general low-energy dynamics for the minimal electroweak symmetry breaking sector with three Goldstone bosons and one light scalar is not so. We construct the effective Lagrangian for these four particles and their scattering amplitudes, that can be extracted from LHC experiments when longitudinal W, Z modes be properly isolated for E >> M-W (equivalence theorem). We then observe the known increase in interaction strength with energy and explore various unitarization methods in the literature in the absence of other new physics (as LHC experiments fail to report anything up to 600 GeV). Our generic conclusion is that for most of parameter space the high-energy scattering of the longitudinal W's is strongly interacting (with the Minimal Standard Model a remarkable exception). We find and study a second sigma-like scalar pole of the WLWL amplitud