4,203 research outputs found
Lorentz violation from gamma-ray bursts
The constancy of light speed is a basic assumption in Einstein's special
relativity, and consequently the Lorentz invariance is a fundamental symmetry
of space-time in modern physics. However, it is speculated that the speed of
light becomes energy-dependent due to the Lorentz invariance violation~(LV) in
various new physics theories. We analyse the data of the energetic photons from
the gamma-ray bursts (GRBs) by the Fermi Gamma-Ray Space Telescope, and find
more events to support the energy dependence in the light speed with both
linear and quadratic form corrections. We provide two scenarios to understand
all the new-released Pass~8 data of bright GRBs by the Fermi-LAT Collaboration,
with predictions from such scenarios being testable by future detected GRBs.Comment: 7 latex pages, 2 figures, final version for journal publicatio
Higgs Pair Production: Improved Description by Matrix Element Matching
Higgs pair production is crucial for measuring the Higgs boson self-coupling.
The dominant channel at hadron colliders is gluon fusion via heavy-quark loops.
We present the results of a fully exclusive simulation of gluon fusion Higgs
pair production based on the matrix elements for hh + 0, 1 partons including
full heavy-quark loop dependence, matched to a parton shower. We examine and
validate this new description by comparing it with (a) Higgs Effective Theory
predictions, (b) exact hh + 0-parton sample showered by pythia, and (c) exact
hh+1-parton distributions, by looking at the most relevant kinematic
distributions, such as PTh, PThh, Mhh spectra, and jet rate as well. We find
that matched samples provide an state-of-the-art accurate exclusive description
of the final state. The relevant LHE files for Higgs pair productions at the
LHC can be accessed via http://hepfarm02.phy.pku.edu.cn/foswiki/CMS/HH, which
can be used for relevant experimental analysis.Comment: accepted version in Phys. Rev. D. arXiv admin note: substantial text
overlap with arXiv:1110.172
Limit on in Two Higgs Doublet Models
Using the recent CLEO measurement of , we find that the
branching ratio of cannot be larger than in two Higgs doublet
models. The small experimental value of can no longer be
explained by charged Higgs boson effects.Comment: 11 pages + 3 Figures (not included), ReVTeX, NTUTH-94-16 and
NHCU-HEP-94-1
Discovery potential of Higgs boson pair production through 4+ final states at a 100 TeV collider
We explore the discovery potential of Higgs pair production at a 100 TeV
collider via full leptonic mode. The same mode can be explored at the LHC when
Higgs pair production is enhanced by new physics. We examine two types of fully
leptonic final states and propose a partial reconstruction method. The
reconstruction method can reconstruct some kinematic observables. It is found
that the variable determined by this reconstruction method and the
reconstructed visible Higgs mass are important and crucial to discriminate the
signal and background events. It is also noticed that a new variable, denoted
as which is defined as the mass difference of two possible
combinations, is very useful as a discriminant. We also investigate the
interplay between the direct measurements of couplings and other
related couplings and trilinear Higgs coupling at hadron colliders and
electron-positron colliders
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