334 research outputs found
Unification in 5D SO(10)
Gauge unification in a five dimensional supersymmetric SO(10) model
compactified on an orbifold is studied. One
orbifolding reduces N=2 supersymmetry to N=1, and the other breaks SO(10) to
the Pati-Salam gauge group \ps. Further breaking to the standard model gauge
group is made through the Higgs mechanism on one of the branes. The differences
of the three gauge couplings run logarithmically even in five dimensions and we
can keep the predictability for unification as in four dimensional gauge
theories. We obtain an excellent prediction for gauge coupling unification with
a cutoff scale GeV and a compactification scale
GeV. Finally, although proton decay due to
dimension 5 operators may be completely eliminated, the proton decay rate in
these models is sensitive to the placement of matter multiplets in the 5th
dimension, as well as to the unknown physics above the cutoff scale.Comment: 33 pages, one reference added and fig. 3 caption correcte
Higgs boson mass limits in perturbative unification theories
Motivated in part by recent demonstrations that electroweak unification into
a simple group may occur at a low scale, we detail the requirements on the
Higgs mass if the unification is to be perturbative. We do this for the
Standard Model effective theory, minimal supersymmetry, and next-to-minimal
supersymmetry with an additional singlet field. Within the Standard Model
framework, we find that perturbative unification with sin2(thetaW)=1/4 occurs
at Lambda=3.8 TeV and requires mh<460 GeV, whereas perturbative unification
with sin2(thetaW)=3/8 requires mh<200 GeV. In supersymmetry, the presentation
of the Higgs mass predictions can be significantly simplified, yet remain
meaningful, by using a single supersymmetry breaking parameter Delta_S. We
present Higgs mass limits in terms of Delta_S for the minimal supersymmetric
model and the next-to-minimal supersymmetric model. We show that in
next-to-minimal supersymmetry, the Higgs mass upper limit can be as large as
500 GeV even for moderate supersymmetry masses if the perturbative unification
scale is low (e.g., Lambda=10 TeV).Comment: 20 pages, latex, 6 figures, references adde
Supersymmetry on the Run: LHC and Dark Matter
Supersymmetry, a new symmetry that relates bosons and fermions in particle
physics, still escapes observation. Search for SUSY is one of the main aims of
the recently launched Large Hadron Collider. The other possible manifestation
of SUSY is the Dark Matter in the Universe. The present lectures contain a
brief introduction to supersymmetry in particle physics. The main notions of
supersymmetry are introduced. The supersymmetric extension of the Standard
Model - the Minimal Supersymmetric Standard Model - is considered in more
detail. Phenomenological features of the MSSM as well as possible experimental
signatures of SUSY at the LHC are described. The DM problem and its possible
SUSY solution is presented.Comment: Latex, 37 pages, 35 figures. Lectures given at 48 Schladming School
on Theoretical Physics, March 201
Finite Theories and the SUSY Flavor Problem
We study a finite SU(5) grand unified model based on the non-Abelian discrete
symmetry A_4. This model leads to the democratic structure of the mass matrices
for the quarks and leptons. In the soft supersymmetry breaking sector, the
scalar trilinear couplings are aligned and the soft scalar masses are
degenerate, thus solving the SUSY flavor problem.Comment: 17 pages, LaTeX, 1 figur
Supernova Bounds on Majoron-emitting decays of light neutrinos
Neutrino masses arising from the spontaneous violation of ungauged
lepton-number are accompanied by a physical Goldstone boson, generically called
Majoron. In the high-density supernova medium the effects of Majoron-emitting
neutrino decays are important even if they are suppressed in vacuo by small
neutrino masses and/or small off-diagonal couplings. We reconsider the
influence of these decays on the neutrino signal of supernovae in the light of
recent Super-Kamiokande data on solar and atmospheric neutrinos. We find that
majoron-neutrino coupling constants in the range 3\times 10^{-7}\lsim g\lsim
2\times 10^{-5} or g \gsim 3 \times 10^{-4} are excluded by the observation
of SN1987A. Then we discuss the potential of Superkamiokande and the Sudbury
Neutrino Observatory to detect majoron neutrino interactions in the case of a
future galactic supernova. We find that these experiments could probe majoron
neutrino interactions with improved sensitivity.Comment: 28 pages, 5 figure
Linking the Practice Environment to Nurses' Job Satisfaction Through Nurse-Physician Communication
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74776/1/j.1547-5069.2005.00063.x.pd
Dependence of the C(,pd) reaction on photon linear polarisation
The sensitivity of the C reaction to photon linear
polarisation has been determined at MAMI, giving the first measurement of the
reaction for a nucleus heavier than He. Photon asymmetries and cross
sections were measured for =170 to 350 MeV. For below
the resonance, reactions leaving the residual Be near its ground
state show a positive asymmetry of up to 0.3, similar to that observed for
He suggesting a similar reaction mechanism for the two nuclei.Comment: 4 pages, 2 figure
Measurements of 12C(→γ,pp) photon asymmetries for Eγ= 200–450 MeV
The 12C (→γ ,pp) reaction has been studied in the photon energy range 200-450 MeV at the Mainz microtron MAMI-C, where linearly polarised photons were energy-tagged using the Glasgow-Mainz Tagged Photon Spectrometer and protons were detected in the Crystal Ball detector. The photon asymmetry Σ has been measured over a wider Eγ range than previous measurements. The strongest asymmetries were found at low missing energies where direct emission of nucleon pairs is expected. Cuts on the difference in azimuthal angles of the two ejected protons increased the magnitude of the observed asymmetries. At low missing energies the Σ data exhibit a strong angular dependence, similar to deuteron photodisintegration
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