820 research outputs found
Minimal Anomalous U(1)' Extension of the MSSM
We study an extension of the MSSM by an anomalous abelian vector multiplet
and a St\"uckelberg multiplet. The anomalies are cancelled by the Green-Schwarz
mechanism and the addition of Chern-Simons terms. The advantage of this choice
over the standard one is that it allows for arbitrary values of the quantum
numbers of the extra U(1). As a first step towards the study of hadron
annihilations producing four leptons in the final state (a clean signal which
might be studied at LHC) we then compute the decays Z'\to Z_0 \g and . We find that the largest values of the decay rate is
GeV, while the expected number of events per year at LHC is at most of the
order of 10.Comment: 45 pages, 8 eps figures, feynmf. Phenomenological section expanded. 2
plots and references adde
Spin Gap and Resonance at the Nesting Wavevector in Superconducting FeSe0.4Te0.6
Neutron scattering is used to probe magnetic excitations in
FeSe_{0.4}Te_{0.6} (T_c=14 K). Low energy spin fluctuations are found with a
characteristic wave vector that corresponds to Fermi surface
nesting and differs from Q_m=(\delta,0,0.5) for magnetic ordering in
Fe_{1+y}Te. A spin resonance with \hbar\Omega_0=6.5 meV \approx 5.3 k_BT_c and
\hbar\Gamma=1.25 meV develops in the superconducting state from a normal state
continuum. We show that the resonance is consistent with a bound state
associated with s+/- superconductivity and imperfect quasi-2D Fermi surface
nesting.Comment: 4 pages, 4 figures, Submitted to Phys. Rev. Let
Ultrahigh Energy Nuclei in the Galactic Magnetic Field
Observations are consistent with a significant fraction of heavy nuclei in
the cosmic ray flux above a few times 10^19 eV. Such nuclei can be deflected
considerably in the Galactic magnetic field, with important implications for
the search of their sources. We perform detailed simulations of heavy nuclei
propagation within recent Galactic magnetic field models. While such models are
not yet sufficiently constrained to predict deflection maps in detail, we find
general features of the distribution of (de-) magnified flux from sources.
Since in most theoretical models sources of heavy nuclei are located in the
local large scale structure of galaxies, we show examples of images of several
nearby galaxy clusters and of the supergalactic plane. Such general features
may be useful to develop efficient methods for source reconstruction from
observed ultrahigh energy cosmic ray arrival directions.Comment: 17 pages, 11 figures. Published in JCA
The Origin of Galactic Cosmic Rays
Motivated by recent measurements of the major components of the cosmic
radiation around 10 TeV/nucleon and above, we discuss the phenomenology of a
model in which there are two distinct kinds of cosmic ray accelerators in the
galaxy. Comparison of the spectra of hydrogen and helium up to 100 TeV per
nucleon suggests that these two elements do not have the same spectrum of
magnetic rigidity over this entire region and that these two dominant elements
therefore receive contributions from different sources.Comment: To be published in Physical Review D, 13 pages, with 3 figures,
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Baryonic Bound State of Vortices in Multicomponent Superconductors
We construct a bound state of three 1/3-quantized Josephson coupled vortices
in three-component superconductors with intrinsic Josephson couplings, which
may be relevant with regard to iron-based superconductors. We find a Y-shaped
junction of three domain walls connecting the three vortices, resembling the
baryonic bound state of three quarks in QCD. The appearance of the Y-junction
(but not a Delta-junction) implies that in both cases of superconductors and
QCD, the bound state is described by a genuine three-body interaction (but not
by the sum of two-body interactions). We also discuss a
confinement/deconfinement phase transition.Comment: 11 pages, 3 figures, one section on confinement/deconfinement
transition added, published versio
Influence of hadronic interaction models and the cosmic ray spectrum on the high energy atmospheric muon and neutrino flux
The recent observations of muon charge ratio up to about 10 TeV and of
atmospheric neutrinos up to energies of about 400 TeV has triggered a renewed
interest into the high-energy interaction models and cosmic ray primary
composition. A reviewed calculation of lepton spectra produced in cosmic-ray
induced extensive air showers is carried out with a primary cosmic-ray spectrum
that fits the latest direct measurements below the knee. In order to achieve
this, we used a full Monte Carlo method to derive the inclusive differential
spectra (yields) of muons, muon neutrinos and electron neutrinos at the surface
for energies between 80 GeV and hundreds of PeV. The air shower simulator {\sc
corsika} 6.990 was used for showering and propagation of the secondary
particles through the atmosphere, employing the established high-energy
hadronic interaction models {\sc sibyll} 2.1, {\sc qgsjet-01} and {\sc
qgsjet-ii 03}. We show that the performance of the interaction models allows
makes it possible to predict the spectra within experimental uncertainties,
while {\sc sibyll} generally yields a higher flux at the surface than the
qgsjet models. The calculation of the flavor and charge ratios has lead to
inconsistent results, mainly influenced by the different representations of the
K/ ratio within the models. Furthermore, we could quantify systematic
uncertainties of atmospheric muon- and neutrino fluxes, associated to the
models of the primary cosmic-ray spectrum and the interaction models. For most
recent parametrizations of the cosmic-ray primary spectrum, atmospheric muons
can be determined with an uncertainty smaller than % of the
average flux. Uncertainties of the muon- and electron neutrino fluxes can be
calculated within an average error of % and %,
respectively.Comment: 16 pages, 10 figures, version 2 includes analytic approximatio
Flux of Atmospheric Neutrinos
Atmospheric neutrinos produced by cosmic-ray interactions in the atmosphere
are of interest for several reasons. As a beam for studies of neutrino
oscillations they cover a range of parameter space hitherto unexplored by
accelerator neutrino beams. The atmospheric neutrinos also constitute an
important background and calibration beam for neutrino astronomy and for the
search for proton decay and other rare processes. Here we review the literature
on calculations of atmospheric neutrinos over the full range of energy, but
with particular attention to the aspects important for neutrino oscillations.
Our goal is to assess how well the properties of atmospheric neutrinos are
known at present.Comment: 68 pages, 26 figures. With permission from the Annual Review of
Nuclear & Particle Science. Final version of this material is scheduled to
appear in the Annual Review of Nuclear & Particle Science Vol. 52, to be
published in December 2002 by Annual Reviews (http://annualreviews.org
Tau Neutrinos Underground: Signals of Oscillations with Extragalactic Neutrinos
The appearance of high energy tau neutrinos due to
oscillations of extragalactic neutrinos can be observed by measuring the
neutrino induced upward hadronic and electromagnetic showers and upward muons.
We evaluate quantitatively the tau neutrino regeneration in the Earth for a
variety of extragalactic neutrino fluxes. Charged-current interactions of the
upward tau neutrinos below and in the detector, and the subsequent tau decay
create muons or hadronic and electromagnetic showers. The background for these
events are muon neutrino and electron neutrino charged-current and
neutral-current interactions, where in addition to extragalactic neutrinos, we
consider atmospheric neutrinos. We find significant signal to background ratios
for the hadronic/electromagnetic showers with energies above 10 TeV to 100 TeV
initiated by the extragalactic neutrinos. We show that the tau neutrinos from
point sources also have the potential for discovery above a 1 TeV threshold. A
kilometer-size neutrino telescope has a very good chance of detecting the
appearance of tau neutrinos when both muon and hadronic/electromagnetic showers
are detected.Comment: section added and two new figs; accepted for publication in Physical
Review
Mixed-symmetry tensor conserved currents and AdS/CFT correspondence
We present the full list of conserved currents built of two massless spinor
fields in Minkowski space and their derivatives multiplied by Clifford algebra
elements. The currents have particular mixed-symmetry type described by Young
diagrams with one row and one column of arbitrary lengths and heights. Along
with Yukawa-like totally antisymmetric currents the complete set of constructed
currents exactly matches the spectrum of AdS mixed-symmetry fields arising in
the generalized Flato-Fronsdal theorem for two spinor singletons. As a
by-product, we formulate and study general properties of primary fields and
conserved currents of mixed-symmetry type.Comment: 17 pages; v2: typos corrected, clarifications and refs added; v3:
more explanations and refs added; contribution to the J.Phys.A special volume
on "Higher Spin Theories and AdS/CFT" edited by Matthias Gaberdiel and
Mikhail Vasilie
Neutral-Current Atmospheric Neutrino Flux Measurement Using Neutrino-Proton Elastic Scattering in Super-Kamiokande
Recent results show that atmospheric oscillate with eV and , and that
conversion into is strongly disfavored. The Super-Kamiokande (SK)
collaboration, using a combination of three techniques, reports that their data
favor over . This distinction
is extremely important for both four-neutrino models and cosmology. We propose
that neutrino-proton elastic scattering () in water
\v{C}erenkov detectors can also distinguish between active and sterile
oscillations. This was not previously recognized as a useful channel since only
about 2% of struck protons are above the \v{C}erenkov threshold. Nevertheless,
in the present SK data there should be about 40 identifiable events. We show
that these events have unique particle identification characteristics, point in
the direction of the incoming neutrinos, and correspond to a narrow range of
neutrino energies (1-3 GeV, oscillating near the horizon). This channel will be
particularly important in Hyper-Kamiokande, with times higher rate.
Our results have other important applications. First, for a similarly small
fraction of atmospheric neutrino quasielastic events, the proton is
relativistic. This uniquely selects (not ) events,
useful for understanding matter effects, and allows determination of the
neutrino energy and direction, useful for the dependence of oscillations.
Second, using accelerator neutrinos, both elastic and quasielastic events with
relativistic protons can be seen in the K2K 1-kton near detector and MiniBooNE.Comment: 10 pages RevTeX, 8 figure
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