4,979 research outputs found
Mode locking of semiconductor laser with curved waveguide and passive mode expander
Active mode locking is reported for a 1.55 ÎŒm semiconductor laser with a curved waveguide and passive mode expander, placed in a wavelength tunable external cavity. One facet with a very low reflectivity of 8Ă10â6 is achieved through a curved active region that tapers into an underlying passive waveguide, thus expanding the mode to give reduced divergence. 10 GHz pulses of 3.1 ps duration have been generated, with a linewidth of 0.81 nm
The dependence of the measured asymmetry : the test of the Bjorken sum rule
We analyse the proton and deutron data on spin dependent asymmetry
supposing the DIS structure functions and
have the similar -dependence. As a result, we have obtained
that at and
at , what is in the
best agreement with the Bjorken sum rule predictions.Comment: LaTeX, 5 pages, no figures, to be published in JETP Letter
Today's View on Strangeness
There are several different experimental indications, such as the
pion-nucleon sigma term and polarized deep-inelastic scattering, which suggest
that the nucleon wave function contains a hidden s bar s component. This is
expected in chiral soliton models, which also predicted the existence of new
exotic baryons that may recently have been observed. Another hint of hidden
strangeness in the nucleon is provided by copious phi production in various N
bar N annihilation channels, which may be due to evasions of the
Okubo-Zweig-Iizuka rule. One way to probe the possible polarization of hidden s
bar s pairs in the nucleon may be via Lambda polarization in deep-inelastic
scattering.Comment: 8 pages LaTeX, 10 figures, to appear in the Proceedings of the
International Conference on Parity Violation and Hadronic Structure,
Grenoble, June 200
False Vacuum Inflation with a Quartic Potential
We consider a variant of Hybrid Inflation, where inflation is driven by two
interacting scalar fields, one of which has a `Mexican hat' potential and the
other a quartic potential. Given the appropriate initial conditions one of the
fields can be trapped in a false vacuum state, supported by couplings to the
other field. The energy of this vacuum can be used to drive inflation, which
ends when the vacuum decays to one of its true minima. Depending on parameters,
it is possible for inflation to proceed via two separate epochs, with the
potential temporarily steepening sufficiently to suspend inflation. We use
numerical simulations to analyse the possibilities, and emphasise the
shortcomings of the slow-roll approximation for analysing this scenario. We
also calculate the density perturbations produced, which can have a spectral
index greater than one.Comment: 10 pages, RevTeX 3.0, no figure
QCD Sum Rule Calculation of Twist-4 Corrections to Bjorken and Ellis-Jaffe Sum Rules
We calculate the twist-4 corrections to the integral of in the
framework of QCD sum rules using an interpolating nucleon field which contains
explicitly a gluonic degree of freedom. This information can be used together
with previous calculations of the twist-3 contribution to the second moment of
to estimate the higher-twist corrections to the Ellis-Jaffe and
Bjorken sum rules. We get and
. Numerically our results roughly agree
with those obtained by Balitsky, Braun and Kolesnichenko based on a sum rule
for a simpler current. Our calculations are far more stable as tested within
the sum rule approach but are more sensitive to less well known condensates.Comment: 18pp., 1 figure (uuencoded eps-file), Late
Hyperon semileptonic decays and quark spin content of the proton
We investigate the hyperon semileptonic decays and the quark spin content of
the proton taking into account flavor SU(3) symmetry breaking.
Symmetry breaking is implemented with the help of the chiral quark-soliton
model in an approach, in which the dynamical parameters are fixed by the
experimental data for six hyperon semileptonic decay constants. As a result we
predict the unmeasured decay constants, particularly for ,
which will be soon measured and examine the effect of the SU(3) symmetry
breaking on the spin content of the proton. Unfortunately
large experimental errors of decays propagate in our analysis making
and practically undetermined. We conclude that
statements concerning the values of these two quantities, which are based on
the exact SU(3) symmetry, are premature. We stress that the meaningful results
can be obtained only if the experimental errors for the decays are
reduced.Comment: The final version accepted for publication in Phys. Rev. D. 18 pages,
RevTex is used with 4 figures include
A Short Review on Jet Identification
Jets can be used to probe the physical properties of the high energy density
matter created in collisions at the Relativistic Heavy Ion Collider (RHIC).
Measurements of strong suppression of inclusive hadron distributions and
di-hadron correlations at high have already provided evidence for
partonic energy loss. However, these measurements suffer from well-known
geometric biases due to the competition of energy loss and fragmentation. These
biases can be avoided if the jets are reconstructed independently of their
fragmentation details - quenched or unquenched. In this paper, we discuss
modern jet reconstruction algorithms (cone and sequential recombination) and
their corresponding background subtraction techniques required by the high
multiplicities of heavy ion collisions. We review recent results from the STAR
experiment at RHIC on direct jet reconstruction in central Au+Au collisions at
GeV.Comment: Proceedings for the invited talk of Hot Quarks 2008, Estes Park, CO
18-23 August 200
Cosmology with a TeV mass GUT Higgs
The most natural way to break the GUT gauge symmetry is with a Higgs field
whose vacuum expectation value is of order 10^{16}\,\mbox{GeV} but whose mass
is of order to 10^3\,\mbox{GeV}. This can lead to a cosmological
history radically different from what is usually assumed to have occurred
between the standard inflationary and nucleosynthesis epochs, which may solve
the gravitino and Polonyi/moduli problems in a natural way.Comment: 4 pages, revte
Flavor Singlet Axial Vector Coupling of the Proton with Dynamical Wilson Fermions
We present the results of a full QCD lattice calculation of the flavor
singlet axial vector coupling of the proton. The simulation has been
carried out on a lattice at with dynamical
Wilson fermions. It turns out that the statistical quality of the connected
contribution to is excellent, whereas the disconnected part is
accessible but suffers from large statistical fluctuations. Using a 1st order
tadpole improved renormalization constant , we estimate .Comment: 13 pages, 5 eps figures, minor changes to text and citation
Magnetic moments of the 3/2 resonances and their quark spin structure
We discuss magnetic moments of the baryons based on an earlier model
for the baryon magnetic moments, allowing for flavor symmetry breaking in the
quark magnetic moments as well as a general quark spin structure. From our
earlier analysis of the nucleon-hyperon magnetic moments and the measured
values of the magnetic moments of and we predict the
other magnetic moments and deduce the spin structure of the resonance
particles. We find from experiment that the total spin polarization of the
decuplet baryons, , is considerably smaller than the
non-relativistic quark model value of 3, although the data is still not good
enough to give a precise determination.Comment: 13 pages, REVTeX, 2 figures, minor clarifying change
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