3,025 research outputs found
Determination of the Higgs boson spin with a linear e+e- collider
The energy dependence of the production cross section of a light Higgs boson
is studied at threshold and compared to the expectations of several spin
assumptions. Cross section measurements at three centre-of-mass energies with
an integrated luminosity of 20 fb-1 allow the confirmation of the scalar nature
of the Higgs Boson.Comment: 4 pages (Latex), 4 figures (Postscript
Measurement of the Charge Ratio of Cosmic Muons using CMS Data
We have performed the measurement of the cosmic ray muon charge ratio, as a
function of the muon momentum, using data collected by the CMS experiment,
exploiting the capabilities of the muon barrel drift tube (DT) chambers. The
cosmic muon charge ratio is defined as the ratio of the number of positive- to
negative-charge muons. Cosmic ray muons result from the interaction of
high-energy cosmic-ray particles (mainly protons and nuclei), entering the
upper layers of the atmosphere, with air nuclei. Since these collisions favour
positive meson production, there is an asymmetry in the charge composition and
more positive muons are expected.
The data samples were collected at the \textit{Magnet Test and Cosmic
Challenge} (MTCC). While the MTCC itself was a crucial milestone in the CMS
detector construction, not having physics studies among its primary goals, it
provided the first opportunity to obtain physics results and test the full
analysis chain using real data in CMS before the LHC startup, together with a
complementary check of the detector performance.Comment: Poster at ICHEP08, Philadelphia, USA, July 2008. 4 page
Measurement of the Higgs Boson Mass with a Linear e+e- Collider
The potential of a linear e+e- collider operated at a centre-of-mass energy
of 350 GeV is studied for the measurement of the Higgs boson mass. An
integrated luminosity of 500 fb-1 is assumed. For Higgs boson masses of 120,
150 and 180 GeV the uncertainty on the Higgs boson mass measurement is
estimated to be 40, 65 and 70 MeV, respectively. The effects of beam related
systematics, namely a bias in the beam energy measurement, the beam energy
spread and the luminosity spectrum due to beamstrahlung, on the precision of
the Higgs boson mass measurement are investigated. In order to keep the
systematic uncertainty on the Higgs boson mass well below the level of the
statistical error, the beam energy measurement must be controlled with a
relative precision better than 10-4.Comment: 19 pages, 10 Figure
Determination of the Higgs boson spin with a linear e+e− collider
The energy dependence of the production cross section of a light Higgs boson is studied at threshold and compared to the expectations of several spin assumptions. Cross section measurements at three centre-of-mass energies with an integrated luminosity of 20 fb-1 allow the confirmation of the scalar nature of the Higgs Boson.Facultad de Ciencias Exacta
Resonant CP Violation in Higgs Radiation at e^+e^- Linear Collider
We study resonant CP violation in the Higgsstrahlung process e^+e^- ->
H_{1,2,3} (Z -> e^+e^-, \mu^+\mu^-) and subsequent decays H_{1,2,3} -> b
\bar{b}, \tau^-\tau^+, in the MSSM with Higgs-sector CP violation induced by
radiative corrections. At a high-energy e^+e^- linear collider, the recoil-mass
method enables one to determine the invariant mass of a fermion pair produced
by Higgs decays with a precision as good as 1 GeV. Assuming an integrated
luminosity of 100/fb, we show that the production lineshape of a coupled system
of neutral Higgs bosons decaying into b\bar{b} quarks is sensitive to the
CP-violating parameters. When the Higgs bosons decay into \tau^-\tau^+, two CP
asymmetries can be defined using the longitudinal and transverse polarizations
of the tau leptons. Taking into account the constraints from electric dipole
moments, we find that these CP asymmetries can be as large as 80 %, in a
tri-mixing scenario where all three neutral Higgs states of the MSSM are nearly
degenerate and mix significantly.Comment: 22 pages, 8 figures, to appear in Phys. Rev.
Phenomenology of the nMSSM from colliders to cosmology
Low energy supersymmetric models provide a solution to the hierarchy problem
and also have the necessary ingredients to solve two of the most outstanding
issues in cosmology: the origin of dark matter and baryonic matter. One of the
most attractive features of this framework is that the relevant physical
processes are related to interactions at the weak scale and therefore may be
tested in collider experiments in the near future. This is true for the Minimal
Supersymmetric Standard Model (MSSM) as well as for its extension with the
addition of one singlet chiral superfield, the so-called nMSSM. It has been
recently shown that within the nMSSM an elegant solution to both the problem of
baryogenesis and dark matter may be found, that relies mostly on the mixing of
the singlet sector with the Higgs sector of the theory. In this work we review
the nMSSM model constraints from cosmology and present the associated collider
phenomenology at the LHC and the ILC. We show that the ILC will efficiently
probe the neutralino, chargino and Higgs sectors, allowing to confront
cosmological observations with computations based on collider measurements. We
also investigate the prospects for a direct detection of dark matter and the
constraints imposed by the current bounds of the electron electric dipole
moment in this model.Comment: 44 pp, 10 figures; Fig.9 replaced; discussion on CP violation
extended and references added; few minor additions in text about details of
the cut
Decoupling property of the supersymmetric Higgs sector with four doublets
In supersymmetric standard models with multi Higgs doublet fields,
selfcoupling constants in the Higgs potential come only from the D-terms at the
tree level. We investigate the decoupling property of additional two heavier
Higgs doublet fields in the supersymmetric standard model with four Higgs
doublets. In particular, we study how they can modify the predictions on the
quantities well predicted in the minimal supersymmetric standard model (MSSM),
when the extra doublet fields are rather heavy to be measured at collider
experiments. The B-term mixing between these extra heavy Higgs bosons and the
relatively light MSSM-like Higgs bosons can significantly change the
predictions in the MSSM such as on the masses of MSSM-like Higgs bosons as well
as the mixing angle for the two light CP-even scalar states. We first give
formulae for deviations in the observables of the MSSM in the decoupling region
for the extra two doublet fields. We then examine possible deviations in the
Higgs sector numerically, and discuss their phenomenological implications.Comment: 26 pages, 24 figures, text sligtly modified,version to appear in
Journal of High Energy Physic
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