18,288 research outputs found
The Discovery of the Higgs Boson with the CMS Detector and its Implications for Supersymmetry and Cosmology
The discovery of the long awaited Higgs boson is described using data from
the CMS detector at the LHC. In the SM the masses of fermions and the heavy
gauge bosons are generated by the interactions with the Higgs field, so all
couplings are related to the observed masses. Indeed, all observed couplings
are consistent with the predictions from the Higgs mechanism, both to vector
bosons and fermions implying that masses are indeed consistent of being
generated by the interactions with the Higgs field. However, on a cosmological
scale the mass of the universe seems not to be related to the Higgs field: the
baryonic mass originates from the binding energy of the quarks inside the
nuclei and dark matter is not even predicted in the SM, so the origin of its
mass is unknown. The dominant energy component in the universe, the dark
energy, yields an accelerated expansion of the universe, so its repulsive
gravity most likely originates from a kind of vacuum energy. The Higgs field
would be the prime candidate for this, if the energy density would not be many
orders of magnitude too high, as will be calculated. The Higgs mass is found to
be 125.70.3(stat.)0.3(syst.) GeV, which is below 130 GeV, i.e. in the
range predicted by supersymmetry. This may be the strongest hint for
supersymmetry in spite of the fact that the predicted supersymmetric particles
have not been discovered so far.Comment: 26 pages, Conference Proceedings Time and Matter (TAM2013), Venice,
Feb. 201
An effective scanning method of the NMSSM parameter space
The next-to-minimal supersymmetric standard model (NMSSM) naturally provides
a 125 GeV Higgs boson without the need for large loop corrections from
multi-TeV stop quarks. Furthermore, the NMSSM provides an electroweak scale
dark matter candidate consistent with all experimental data, like relic density
and non-observation of direct dark matter signals with the present experimental
sensitivity. However, more free parameters are introduced in the NMSSM, which
are strongly correlated. A simple parameter scan without knowing the
correlation matrix is not efficient and can miss significant regions of the
parameter space. We introduce a new technique to sample the NMSSM parameter
space, which takes into account the correlations. For this we project the 7D
NMSSM parameter space onto the 3D Higgs boson mass parameter space. The reduced
dimensionality allows for a non-random sampling and therefore a complete
coverage of the allowed NMSSM parameters. In addition, the parameter
correlations and possible deviations of the signal strengths of the observed
125 Higgs boson from the SM values are easily predicted.Comment: 15 pages, 5 figure
Spontaneous electro-weak symmetry breaking and cold dark matter
In the standard model, the weak gauge bosons and fermions obtain mass after
spontaneous electro-weak symmetry breaking, which is realized through one
fundamental scalar field, namely Higgs field. In this paper we study the
simplest scalar cold dark matter model in which the scalar cold dark matter
also obtains mass through interaction with the weak-doublet Higgs field, the
same way as those of weak gauge bosons and fermions. Our study shows that the
correct cold dark matter relic abundance within uncertainty () and experimentally allowed Higgs boson mass
( GeV) constrain the scalar dark matter mass within GeV. This result is in excellent agreement with that of W. de
Boer et.al. ( GeV). Such kind of dark matter annihilation can
account for the observed gamma rays excess () at EGRET for energies
above 1 GeV in comparison with the expectations from conventional Galactic
models. We also investigate other phenomenological consequences of this model.
For example, the Higgs boson decays dominantly into scalar cold dark matter if
its mass lies within GeV.Comment: 4 Revtex4 pages, refs adde
A new Determination of the Extragalactic Background of Diffuse Gamma Rays taking into account Dark Matter Annihilation
The extragalactic background (EGB) of diffuse gamma rays can be determined by
subtracting the Galactic contribution from the data. This requires a Galactic
model (GM) and we include for the first time the contribution of dark matter
annihilation (DMA), which was previously proposed as an explanation for the
EGRET excess of diffuse Galactic gamma rays above 1 GeV.
In this paper it is shown that the newly determined EGB shows a
characteristic high energy bump on top of a steeply falling soft contribution.
The bump is shown to be compatible with a contribution from an extragalactic
DMA signal from weakly interacting massive particles (WIMPs) with a mass
between 50 and 100 GeV in agreement with the EGRET excess of the Galactic
diffuse gamma rays and in disagreement with earlier analysis. The remaining
soft contribution of the EGB is shown to resemble the spectra of the observed
point sources in our Galaxy.Comment: 7 pages, 4 figures. Accepted by A&A, made Fig. 4 and table 1
consisten
Further search for a neutral boson with a mass around 9 MeV/c2
Two dedicated experiments on internal pair conversion (IPC) of isoscalar M1
transitions were carried out in order to test a 9 MeV/c2 X-boson scenario. In
the 7Li(p,e+e-)8Be reaction at 1.1 MeV proton energy to the predominantly T=0
level at 18.15 MeV, a significant deviation from IPC was observed at large pair
correlation angles. In the 11B(d,n e+e-)12C reaction at 1.6 MeV, leading to the
12.71 MeV 1+ level with pure T=0 character, an anomaly was observed at 9
MeV/c2. The compatibility of the results with the scenario is discussed.Comment: 12 pages, 5 figures, 2 table
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