7,036 research outputs found
Lepton Photon Symposium 2005: Summary and Outlook
Lepton Photon 2005 told the saga of the Standard Model which is still
exhilarating because it leaves all questions of consequence unanswered.Comment: Talk presented at the XXII International Symposium on Lepton-Photon
Interactions at High Energy, Uppsala, Sweden, July 2005. 11 pages, Latex2e
with ws-procs10x7.cls (included), 6 postscript figures (color). Typos
correcte
The Fine-Tuning Problem of the Electroweak Symmetry Breaking Mechanism in Minimal SUSY Models
We calculate the region of the MSSM parameter space (i.e. , ,
, \ldots) compatible with a correct electroweak breaking and a realistic
top-quark mass. To do so we have included {\em all} the one-loop corrections to
the effective potential and checked their importance in order to obtain
consistent results. We also consider the fine-tuning problem due to the
enormous dependence of on (the top Yukawa coupling), which is
substantially reduced when the one-loop effects are taken into account. We also
explore the reliability of the so-called "standard" criterion to estimate the
degree of fine-tuning. As a consequence, we obtain a new set of upper bounds on
the MSSM parameters or, equivalently, on the supersymmetric masses perfectly
consistent with the present experimental bounds.Comment: talk given at the XVI Kazimierz Meeting on Elementary Particle
Physics, Kazimierz (Poland) 24-28 May 1993, 4 pages in standard LATEX + 2
figures (not included but available upon request), CERN-TH.7024/9
Maximally correlated multipartite quantum states
We investigate quantum states that posses both maximum entanglement and
maximum discord between the pertinent parties. Since entanglement (discord) is
defined only for bipartite (two qubit) systems, we shall introduce an
appropriate sum over of all bi-partitions as the associated measure. The
ensuing definition --not new for entanglement-- is thus extended here to
quantum discord. Also, additional dimensions within the parties are considered
({\it qudits}). We also discuss nonlocality (in the form of maximum violation
of a Bell inequality) for all multiqubit systems. The emergence of more
nonlocal states than local ones, all of them possessing maximum entanglement,
will be linked, surprisingly enough, to whether quantum mechanics is defined
over the fields of real or complex numbers.Comment: 13 pages, 5 figures, 2 table
Implications for New Physics from Fine-Tuning Arguments: II. Little Higgs Models
We examine the fine-tuning associated to electroweak breaking in Little Higgs
scenarios and find it to be always substantial and, generically, much higher
than suggested by the rough estimates usually made. This is due to implicit
tunings between parameters that can be overlooked at first glance but show up
in a more systematic analysis. Focusing on four popular and representative
Little Higgs scenarios, we find that the fine-tuning is essentially comparable
to that of the Little Hierarchy problem of the Standard Model (which these
scenarios attempt to solve) and higher than in supersymmetric models. This does
not demonstrate that all Little Higgs models are fine-tuned, but stresses the
need of a careful analysis of this issue in model-building before claiming that
a particular model is not fine-tuned. In this respect we identify the main
sources of potential fine-tuning that should be watched out for, in order to
construct a successful Little Higgs model, which seems to be a non-trivial
goal.Comment: 39 pages, 26 ps figures, JHEP forma
The 750 GeV Diphoton Excess as a First Light on Supersymmetry Breaking
One of the most exciting explanations advanced for the recent diphoton excess
found by ATLAS and CMS is in terms of sgoldstino decays: a signal of low-energy
supersymmetry-breaking scenarios. The sgoldstino, a scalar, couples directly to
gluons and photons, with strength related to gaugino masses, that can be of the
right magnitude to explain the excess. However, fitting the suggested resonance
width, Gamma ~ 45 GeV, is not so easy. In this paper we explore efficient
possibilities to enhance the sgoldstino width, via the decay into two Higgses,
two Higgsinos and through mixing between the sgoldstino and the Higgs boson. In
addition, we present an alternative and more efficient mechanism to generate a
mass splitting between the scalar and pseudoscalar components of the
sgoldstino, which has been suggested as an interesting alternative explanation
to the apparent width of the resonance.Comment: 14 pages, 3 figure
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