4,556 research outputs found
Search for the Higgs boson: theoretical perspectives
We present a short review of experimental and theoretical constraints on the
mass of the Standard Model Higgs boson. We briefly illustrate the
unsatisfactory aspects of the standard theory, and we present some general
considerations about possible non-standard scenarios.Comment: 13 pages latex, 6 PS figures. Talk given at Les Rencontres de la
Vallee d'Aoste, La Thuile, Italy, March 4-10, 200
Heavy quark production: recent developments
I discuss some aspects of the comparison between QCD predictions and
experimental data in charm and bottom production.Comment: 5 pages Latex, uses epsfig.sty,aipproc.sty, 7 eps figures included.
Talk given at the 5th International Workshop on Deep Inelastic Scattering and
QCD (DIS 97), Chicago, IL, 14-18 Apr 199
On positivity of parton distributions
We discuss the bounds on polarized parton distributions which follow from
their definition in terms of cross section asymmetries. We spell out how the
bounds obtained in the naive parton model can be derived within perturbative
QCD at leading order when all quark and gluon distributions are defined in
terms of suitable physical processes. We specify a convenient physical
definition for the polarized and unpolarized gluon distributions in terms of
Higgs production from gluon fusion. We show that these bounds are modified by
subleading corrections, and we determine them up to NLO. We examine the ensuing
phenomenological implications, in particular in view of the determination of
the polarized gluon distribution.Comment: 20 pages, 8 figures included by epsf, plain tex with harvma
Heavy Flavour Production
We review the status of heavy flavour production in QCD. Comparison of
experimental and theoretical results for top and bottom production are given.
Selected topics in charm production are also discussed.Comment: 18 pages, Latex, epsfig, 12 tar-gzip-uuencoded figures. Invited talk
given at the XV International conference "Physics in Collisions", Cracow,
Poland, June 8-10, 199
On the metastability of the Standard Model vacuum
If the Higgs mass m_H is as low as suggested by present experimental
information, the Standard Model ground state might not be absolutely stable. We
present a detailed analysis of the lower bounds on m_H imposed by the
requirement that the electroweak vacuum be sufficiently long-lived. We perform
a complete one-loop calculation of the tunnelling probability at zero
temperature, and we improve it by means of two-loop renormalization-group
equations. We find that, for m_H=115 GeV, the Higgs potential develops an
instability below the Planck scale for m_t>(166\pm 2) GeV, but the electroweak
vacuum is sufficiently long-lived for m_t < (175\pm 2) \GeV.Comment: LaTex 23 pages, 4 eps figures. Misprint in the abstract corrected,
reference adde
Higgs Boson Properties in the Standard Model and its Supersymmetric Extensions
We review the realization of the Brout-Englert-Higgs mechanism in the
electroweak theory and describe the experimental and theoretical constraints on
the mass of the single Higgs boson expected in the minimal Standard Model. We
also discuss the couplings of this Higgs boson and its possible decay modes as
functions of its unknown mass. We then review the structure of the Higgs sector
in the minimal supersymmetric extension of the Standard Model (MSSM), noting
the importance of loop corrections to the masses of its five physical Higgs
bosons. Finally, we discuss some non-minimal models.Comment: To be published in "Search of the Higgs Particle", Comptes Rendus de
l'Academie des Sciences, Franc
Complex Networks Unveiling Spatial Patterns in Turbulence
Numerical and experimental turbulence simulations are nowadays reaching the
size of the so-called big data, thus requiring refined investigative tools for
appropriate statistical analyses and data mining. We present a new approach
based on the complex network theory, offering a powerful framework to explore
complex systems with a huge number of interacting elements. Although interest
on complex networks has been increasing in the last years, few recent studies
have been applied to turbulence. We propose an investigation starting from a
two-point correlation for the kinetic energy of a forced isotropic field
numerically solved. Among all the metrics analyzed, the degree centrality is
the most significant, suggesting the formation of spatial patterns which
coherently move with similar vorticity over the large eddy turnover time scale.
Pattern size can be quantified through a newly-introduced parameter (i.e.,
average physical distance) and varies from small to intermediate scales. The
network analysis allows a systematic identification of different spatial
regions, providing new insights into the spatial characterization of turbulent
flows. Based on present findings, the application to highly inhomogeneous flows
seems promising and deserves additional future investigation.Comment: 12 pages, 7 figures, 3 table
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