4 research outputs found
The Voyage of Discovery of the Higgs Boson at the LHC
The journey in search for the Higgs boson started in earnest with the discovery of the W and Z bosons. The LHC accelerator, the ATLAS and CMS experiments were conceived in the late 1980s and early 1990s, and it took two decades to turn the concepts to reality. Novel and innovative technologies needed to be developed and turned into superbly functioning engines for providing proton-proton collisions in the case of the LHC and physics results in the case of the experiments. The most significant discovery so far to emerge from the LHC project is that of a heavy scalar boson, announced on 4th July 2012. The data collected so far point strongly to its properties as those expected for the Higgs boson associated with the Brout-Englert-Higgs mechanism
What if Supersymmetry Breaking Unifies beyond the GUT Scale?
We study models in which soft supersymmetry-breaking parameters of the MSSM
become universal at some unification scale, , above the GUT scale,
\mgut. We assume that the scalar masses and gaugino masses have common
values, and respectively, at . We use the
renormalization-group equations of the minimal supersymmetric SU(5) GUT to
evaluate their evolutions down to \mgut, studying their dependences on the
unknown parameters of the SU(5) superpotential. After displaying some generic
examples of the evolutions of the soft supersymmetry-breaking parameters, we
discuss the effects on physical sparticle masses in some specific examples. We
note, for example, that near-degeneracy between the lightest neutralino and the
lighter stau is progressively disfavoured as increases. This has the
consequence, as we show in planes for several different values
of , that the stau coannihilation region shrinks as
increases, and we delineate the regions of the plane
where it is absent altogether. Moreover, as increases, the focus-point
region recedes to larger values of for any fixed and
. We conclude that the regions of the plane that are
commonly favoured in phenomenological analyses tend to disappear at large
.Comment: 24 pages with 11 eps figures; references added, some figures
corrected, discussion extended and figure added; version to appear in EPJ
Particle physics after the Higgs boson discovery: opportunities for the Large Hadron Collider
Two-loop QCD corrections to the helicity amplitudes for H → 3 partons
Many search strategies for the Standard Model Higgs boson apply specific selection criteria on hadronic jets observed in association with the Higgs boson decay products, either in the form of a jet veto, or by defining event samples according to jet multiplicity. To improve the theoretical description of Higgs-boson-plus-jet production (and the closely related Higgs boson transverse momentum distribution), we derive the two-loop QCD corrections to the helicity amplitudes for the processes H → ggg and H → qq¯¯gqq¯g in an effective theory with infinite top quark mass. The helicity amplitudes are extracted from the coefficients appearing in the general tensorial structure for each process. The coefficients are derived from the Feynman graph amplitudes by means of projectors within the conventional dimensional regularization scheme. The infrared pole structure of our result agrees with the expectation from infrared factorization and the finite parts of the amplitudes are expressed in terms of one- and two-dimensional harmonic polylogarithms