2,696 research outputs found
Double Higgs production at TeV Colliders in the Minimal Supersymmetric Standard Model
The reconstruction of the Higgs potential in the Minimal Supersymmetric
Standard Model (MSSM) requires the measurement of the trilinear Higgs
self-couplings. The `double Higgs production' subgroup has been investigating
the possibility of detecting signatures of processes carrying a dependence on
these vertices at the Large Hadron Collider (LHC) and future Linear Colliders
(LCs). As reference reactions, we have chosen and ,
respectively, where is the lightest of the MSSM Higgs bosons. In both
cases, the interaction is involved. For , the two reactions are
resonant in the mode, providing cross sections which are detectable
at both accelerators and strongly sensitive to the strength of the trilinear
coupling involved. We explore this mass regime of the MSSM in the decay channel, also accounting for irreducible background effects.Comment: LaTeX, 23 pages, 13 PostScript figures (contribution to the Summary
Report of the Higgs WG, Workshop `Physics at TeV Colliders', Les Houches,
France, 8-18 June 1999): some modifications to the bibliograph
d13C tracing of dissolved inorganic carbon sources in Patagonian rivers (Argentina)
The main Patagonian rivers (Colorado, Negro, Chubut, Deseado, Coyle, Chico, Santa Cruz and Gallegos) were sampled between September 1995 and November 1998 to determine their chemical and isotopic compositions, the origins of the suspended and dissolved river loads and their inputs to the South Atlantic Ocean. This paper focuses on the dissolved inorganic carbon (DIC) transport and its υ13C isotopic signature. The υ13CDIC values vary between 12Ð8 and 1Ð8‰ and allow one to distinguish two river groups: (i) the Colorado, Negro, Chubut and Santa Cruz, which display the highest values and the lowest seasonal variations; (ii) the Deseado, Coyle, Chico and Gallegos, which show the lowest values and the highest seasonal variations. For the first group, υ13CDIC is mainly controlled by important exchanges between the river waters and atmospheric CO2, due to the presence of lakes and dams. For the second group, υ13CDIC also appears to be controlled by the oxidation of organic carbon, showing a negative relationship between υ13CDIC and the dissolved organic carbon. These biogeochemical processes interfere with the contribution of carbonate and silicate weathering to the riverine DIC and do not allow use of υ13CDIC alone to distinguish these contributions. The annual DIC flux exported by Patagonian Rivers to the South Atlantic Ocean averages 621 ð 109 g. of C, i.e. a specific yield of 2Ð7 g m2 year1. The mean υ13CDIC can be estimated to 4Ð9‰, which is high compared with other rivers of the world
Higgs look-alikes at the LHC
The discovery of a Higgs particle is possible in a variety of search channels
at the LHC. However the true identity of any putative Higgs boson will at first
remain ambiguous, until one has experimentally excluded other possible
assignments of quantum numbers and couplings. We quantify to what degree one
can discriminate a Standard Model Higgs boson from "look-alikes" at, or close
to, the moment of discovery at the LHC. We focus on the fully-reconstructible
"golden" decay mode to a pair of Z bosons and a four-lepton final state,
simulating sPlot-weighted samples of signal and background events. Considering
both on-shell and off-shell Z's, we show how to utilize the full decay
information from the events, including the distributions and correlations of
the five relevant angular variables. We demonstrate how the finite phase space
acceptance of any LHC detector sculpts the decay distributions, a feature
neglected in previous studies. We use likelihood ratios to discriminate a
Standard Model Higgs from look-alikes with other spins or nonstandard parity,
CP, or form factors. For a benchmark resonance mass of 200 GeV/c^2, we achieve
a median expected discrimination significance of 3 sigma with as few as 19
events, and even better discrimination for the off-shell decays of a 145
GeV/c^2 resonance.Comment: 39 pages, 55 figures, typos fixed, figures added, and minor
clarification
Higgs Physics at the Large Hadron Collider
In this talk I will begin by summarising the importance of the Higgs physics
studies at the LHC. I will then give a short description of the pre-LHC
constraints on the Higgs mass and the theoretical predictions for the LHC along
with a discussion of the current experimental results, ending with prospects in
the near future at the LHC. In addition to the material covered in the
presented talk, I have included in the writeup, a critical appraisal of the
theoretical uncertainties in the Higgs cross-sections at the Tevatron as well
as a discussion of the recent experimental results from the LHC which have
become available since the time of the workshop.Comment: LateX, 12 figures, 15 pages, Presented at the XIth Workshop on High
Energy Physics Phenomenology, 2010, Ahmedabad, Indi
Formalizing the transformations of a cognitive universe
International audienceIn an effort to continue the pioneering work of Harary in USA and Flament in France, we have undertaken to develop, on an experimental basis, a formalized theory of systems of beliefs and their modifications. This theory uses the psycho-social concepts of theories of cognitive consistency and of the tools of discrete mathematics, such as rewriting and intervals within graphs. The axioms and rewriting rules are elaborated from experimental data, and we demonstrate that the system we have built has the property of termination. This result is in accordance with experimental observations that show that every subject having an inconsistent system of beliefs (i.e., one containing contradictions) makes this system evolve towards consistency to reach a simple, consistent reference framework
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Image analysis and statistical inference in neuroimaging with R
R is a language and environment for statistical computing and graphics.
It can be considered an alternative implementation of the S language
developed in the 1970s and 1980s for data analysis and graphics (Becker and
Chambers, 1984; Becker et al., 1988). The R language is part of the GNU
project and offers versions that compile and run on almost every major
operating system currently available. We highlight several R packages built
specifically for the analysis of neuroimaging data in the context of
functional MRI, diffusion tensor imaging, and dynamic contrast-enhanced MRI.
We review their methodology and give an overview of their capabilities for
neuroimaging. In addition we summarize some of the current activities in the
area of neuroimaging software development in R
Disentangling Dimension Six Operators through Di-Higgs Boson Production
New physics near the TeV scale can generate dimension-six operators that
modify the production rate and branching ratios of the Higgs boson. Here, we
show how Higgs boson pair production can yield complementary information on
dimension-six operators involving the gluon field strength. For example, the
invariant mass distribution of the Higgs boson pair can show the extent to
which the masses of exotic TeV-scale quarks come from electroweak symmetry
breaking. We discuss both the current Tevatron bounds on these operators and
the most promising LHC measurement channels for two different Higgs masses: 120
GeV and 180 GeV. We argue that the operators considered in this paper are the
ones most likely to yield interesting Higgs pair physics at the LHC.Comment: 20 pages, 7 figures; v2: to match JHEP versio
A threshold-improved narrow-width approximation for BSM physics
A modified narrow-width approximation that allows for O(Gamma/M)-accurate
predictions for resonant particle decay with similar intermediate masses is
proposed and applied to MSSM processes to demonstrate its importance for
searches for particle physics beyond the Standard Model.Comment: 10 pages, 5 figures, version to appear in JHE
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