2,972 research outputs found
Beyond the standard model physics at RHIC in polarized pp collision
A polarized hadron collider experiment must have a great discovery potential
for a search of physics beyond the standard model. Experimental data of various
symmetry tests at RHIC are going to be obtained within a few years. The author
developed a simulation tool, studying a sensitivity of hunting contact
interaction at RHIC by measuring parity violating spin asymmetries.Comment: 8 pages, 9 figure, Proc. of Praha-SPIN-200
Magnetic properties of polypyrrole - coated iron oxide nanoparticles
Iron oxide nanoparticles were prepared by sol -gel process. Insitu
polymerization of pyrrole monomer in the presence of oxygen in iron oxide
ethanol suspension resulted in a iron oxide - polypyrrole nanocomposite. The
structure and magnetic properties were investigated for varying pyrrole
concentrations. The presence of the gamma - iron oxide phase and polypyrrole
were confirmed by XRD and FTIR respectively. Agglomeration was found to be
comparatively much reduced for the coated samples, as shown by TEM. AC
susceptibility measurements confirmed the superparamagnetic behaviour.
Numerical simulations performed for an interacting model system are performed
to estimate the anisotropy and compare favourably with experimental results.Comment: 11 pages,8 figure
Simple predictions from ALCOR_c for rehadronisation of charmed quark matter
We study the production of charmed hadrons with the help of ALCOR_c, the
algebraic coalescence model for rehadronisation of charmed quark matter.
Mesonic ratios are introduced as factors connecting various antibaryon to
baryon ratios. The resulting simple relations could serve as tests of quark
matter formation and coalescence type rehadronization in heavy ion collisions.Comment: 7 pages in Latex, 1 PS figur
Electrochemistry and spectroelectrochemistry of polymers based on D-A-D and D-D-D bis( N -carbazolyl) monomers, effect of the donor/acceptor core on their properties
In this work we present electropolymerization of monomers of an unusual type using N-linked carbazole units to limit their conjugation. The polymers thus obtained have limited conjugation through the backbone. Using donor-acceptor-donor (D-A-D) and donor-donor-donor (D-D-D) monomers we evaluate the effects of the presence (or absence) of charge transfer states on synthesized electropolymers. The use of a D-A-D monomer resulted in obtaining an ambipolar polymer with quasi-reversible reduction
Neutrinos and Future Concordance Cosmologies
We review the free parameters in the concordance cosmology, and those which
might be added to this set as the quality of astrophysical data improves. Most
concordance parameters encode information about otherwise unexplored aspects of
high energy physics, up to the GUT scale via the "inflationary sector," and
possibly even the Planck scale in the case of dark energy. We explain how
neutrino properties may be constrained by future astrophysical measurements.
Conversely, future neutrino physics experiments which directly measure these
parameters will remove uncertainty from fits to astrophysical data, and improve
our ability to determine the global properties of our universe.Comment: Proceedings of paper given at Neutrino 2008 meeting (by RE
Spin-independent elastic WIMP scattering and the DAMA annual modulation signal
We discuss the interpretation of the annual modulation signal seen in the
DAMA experiment in terms of spin-independent elastic WIMP scattering. Taking
into account channeling in the crystal as well as the spectral signature of the
modulation signal we find that the low-mass WIMP region consistent with DAMA
data is confined to WIMP masses close to GeV, in
disagreement with the constraints from CDMS and XENON. We conclude that even if
channeling is taken into account this interpretation of the DAMA modulation
signal is disfavoured. There are no overlap regions in the parameter space at
90% CL and a consistency test gives the probability of . We
study the robustness of this result with respect to variations of the WIMP
velocity distribution in our galaxy, by changing various parameters of the
distribution function, and by using the results of a realistic N-body dark
matter simulation. We find that only by making rather extreme assumptions
regarding halo properties can we obtain agreement between DAMA and CDMS/XENON.Comment: 21 pages, 12 figures, matches version accepted in JCA
New approach to 3D electrostatic calculations for micro-pattern detectors
We demonstrate practically approximation-free electrostatic calculations of
micromesh detectors that can be extended to any other type of micropattern
detectors. Using newly developed Boundary Element Method called Robin Hood
Method we can easily handle objects with huge number of boundary elements
(hundreds of thousands) without any compromise in numerical accuracy. In this
paper we show how such calculations can be applied to Micromegas detectors by
comparing electron transparencies and gains for four different types of meshes.
We demonstrate inclusion of dielectric material by calculating the electric
field around different types of dielectric spacers
On the two-loop contributions to the pion mass
We derive a simplified representation for the pion mass to two loops in
three-flavour chiral perturbation theory. For this purpose, we first determine
the reduced expressions for the tensorial two-loop 2-point sunset integrals
arising in chiral perturbation theory calculations. Making use of those
relations, we obtain the expression for the pion mass in terms of the minimal
set of master integrals. On the basis of known results for these, we arrive at
an explicit analytic representation, up to the contribution from K-K-eta
intermediate states where a closed-form expression for the corresponding sunset
integral is missing. However, the expansion of this function for a small pion
mass leads to a simple representation which yields a very accurate
approximation of this contribution. Finally, we also give a discussion of the
numerical implications of our results.Comment: Typos corrected and minor changes in Table 2. Published version. 19
pages, 1 figure, 2 table
Gamma-ray Constraints on Effective Interactions of the Dark Matter
Using an effective interaction approach to describe the interactions between
the dark matter particle and the light degrees of freedom of the standard
model, we calculate the gamma-ray flux due to the annihilation of the dark
matter into quarks, followed by fragmentation into neutral pions which
subsequently decay into photons. By comparison to the mid-latitude data
released from the Fermi-LAT experiment, we obtain useful constraints on the
size of the effective interactions and they are found to be comparable to those
deduced from collider, gamma-ray line and anti-matter search experiments.
However, the two operators induced by scalar and vector exchange among
fermionic dark matter and light quarks that contribute to spin-independent
cross sections are constrained more stringently by the recent XENON100 data.Comment: 22 pages, 4 figures; title fixed and a couple of references adde
Vector- and Pseudoscalar-baryon coupled channel systems
In this manuscript, I will report the details of our recent work on the
vector meson-baryon (VB) interaction, which we studied with the motivation of
finding dynamical generation of resonances in the corresponding systems. We
started our study by building a formalism based on the hidden local symmetry
and calculating the leading order contributions to the scattering equations by
summing the diagrams with: (a) a vector meson exchange in the t-channel (b) an
octet baryon exchange in the s-, u-channels and (c) a contact interaction
arising from the part of the vector meson-baryon Lagrangian which is related to
the anomalous magnetic moment of the baryons. We find the contribution from all
these sources, except the s-channel, to be important. The amplitudes obtained
by solving the coupled channel Bethe-Salpeter equations for the systems with
total strangeness zero, show generation of one isospin 3/2, spin 1/2 resonance
and three isospin 1/2 resonances: two with spin 3/2 and one with spin 1/2. We
identify these resonances with (1900) , (2080) ,
(1700) , and (2090) , respectively.
We have further extended our study by including pseudoscalar meson-baryon
(PB) as the coupled channels of VB systems. For this, we obtain the PB
VB amplitudes by using the Kroll-Ruddermann term where,
considering the vector meson dominance phenomena, the photon is replaced by a
vector meson. The calculations done within this formalism reveal a very strong
coupling of the VB channels to the low-lying resonances like (1405)
and (1670), which can have important implications on certain reactions
producing them. In addition to this, we find that the effect of coupling the
higher mass states to the lighter channels is not restricted to increasing the
width of those states, it can be far more strong.Comment: Proceedings of the "DAE-BRNS Workshop on Hadron Physics" held in
Mumbai, India during October 31-November 04, 201
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