2,996 research outputs found
On the Spin of the X(3872)
Whether the much studied X(3872) is an axial or tensor resonance makes an
important difference to its interpretation. A recent paper by the BaBar
collaboration raised the viable hypothesis that it might be a 2-+ state based
on the 3 pions spectrum in the X -> J/psi omega decays. Furthermore, the Belle
collaboration published the 2 pions invariant mass and spin-sensitive angular
distributions in X -> J/psi rho decays. Starting from a general parametrization
of the decay amplitudes for the axial and tensor quantum numbers of the X, we
re-analyze the whole set of available data. The level of agreement of the two
spin hypotheses with data is interpreted with a rigorous statistical approach
based on Monte Carlo simulations in order to be able to combine all the
distributions regardless of their different levels of sensitivity to the spin
of the X. Our analysis returns a probability of 5.5% and 0.1% for the agreement
with data of the 1++ and 2-+ hypotheses, respectively, once we combine the
whole information (angular and mass distributions) from both channels. On the
other hand, the separate analysis of J/psi rho (angular and mass distributions)
and J/psi omega (mass distribution) indicates that the 2-+ assignment is
excluded at the 99.9% C.L. by the former case, while the latter excludes at the
same level the 1++ hypothesis. There are therefore indications that the two
decay modes behave in a different way.Comment: 12 pages, 9 figures, 2 tables. Added angular distributions, which
lead to different conclusion
Exotic Heavy Quarkonium Spectroscopy: A Mini-review
Since nine years experiments have been observing a host of exotic states
decaying into heavy quarkonia. The interpretation of most of them still remains
uncertain and, in some cases, controversial, notwithstanding a considerable
progress has been made on the quality of the experimental information available
and a number of ideas and models have been put forward to explain the
observations. In this mini-review we will summarize the measurements, with the
most recent updates, and list the useful ones yet to be done. We will discuss
the problem of the spin of the X, which could hide some major surprise on its
interpretation, and review some more phenomenological issues debated in the
field.Comment: 14 pages, 2 figures, 5 tables. To appear in Mod. Phys. Lett.
Development of Protective Clothing against Nanoparticle Based on Electrospun Nanofibers
In this paper, the development of efficient protective clothing against nanoparticulate aerosols is presented. Nanofibrous mats of polyamide 6 (PA6) were deposited onto a nonwoven viscose substrate by electrospinning technique. The influence of electrospinning parameters, including solution concentration, viscosity, and conductivity, was studied for the production of nonwovens with controlled fiber diameter showing a size distribution ranging from 66 to 195 nm. By varying several process parameters, textiles with different thickness of the nanofiber layer and thus air permeability were obtained. A hot-press lamination process using a thermoplastic resin as glue was applied to improve the adhesion of the nanofiber layer onto the textile support. After 1500 cycles of repeated compression and torsion, the nanofiber layer was still firmly attached to the support, while mechanical damage is visible in some areas. The penetration of NaCl particles with diameter ranging from 15 to 300 nm through the electrospun textiles was found to be strongly dependent on nanofiber layer thickness. A really thin nanofiber coating provides up to 80% retention of 20 nm size particles and over 50% retention of 200 nm size nanoparticles. Increasing the thickness of the nanofiber mat, the filtration efficiency was increased to over 99% along the whole nanoparticle range. The results obtained highlight the potential of nanofibers in the development of efficient personal protective equipments against nanoparticles.The financial support of this work was provided by MICINN (Spanish Ministry of Science and Innovation) and ERDF
(European Regional Development Fund) (ref.: PSE-420000-2008–003), and ACC1´O (Catalan Business Competitiveness
Support Agency
Higher Tetraquark Particles
There are strong arguments favoring a four-quark interpretation of sub-GeV
light scalar mesons and the diquark-antidiquark body-plan of the tetraquark
seems to provide the most convincing picture. The building diquarks of these
particles are assumed to be spin zero objects. In this paper we explore the
possibility that radially excited aggregations of spin zero or spin one
diquarks might exist and discuss the possibility of the Y(2175) state observed
by BaBar and confirmed by BES being one such state.Comment: 8 pages, 4 figure
Exploring the Adsorption of Pb on Microalgae-Derived Biochar: A Versatile Material for Environmental Remediation and Electroanalytical Applications
Biochar, a carbon material obtained by pyrolysis of biomasses, is increasingly applied in environmental remediation and sensing thanks to its functional properties, cost-effectiveness and eco-friendliness. The adsorption capacity of biochar, strictly dependent on its specific surface area, heteroatom doping and surface functional groups, is crucial for these applications. Here, biochar produced at low temperature (350â—¦ C) from a marine microalga (Nannochloropsis sp.) is proposed as an efficient adsorbent of lead (II) ions in aqueous solution; this production strategy promotes the natural self-doping of biochar without requiring harsh conditions. The kinetics and thermodynamics of the adsorption process, as well as the effect of pH, ionic strength and dissolved organic matter on the adsorption efficiency were systematically assessed. The microalgae-derived biochar shows superior adsorption performances compared to a nutshell-derived one (used as a reference of lignocellulosic feedstocks) under all the tested conditions. The microalgae-derived biochar was finally used to decorate screen-printed carbon electrodes to improve the electroanalytical performances towards the voltammetric detection of lead (II) ions. A two-fold increase in sensitivity was obtained compared to the unmodified electrode thanks to the enhanced electron transfer and adsorption properties provided by biochar. These results highlight the potentialities of microalgae-derived biochar for environmental and sensing applications
Search for Neutron Flux Generation in a Plasma Discharge Electrolytic Cell
Following some recent unexpected hints of neutron production in setups like
high-voltage atmospheric discharges and plasma discharges in electrolytic
cells, we present a measurement of the neutron flux in a configuration similar
to the latter. We use two different types of neutron detectors,
poly-allyl-diglicol-carbonate (PADC, aka CR-39) tracers and Indium disks. At
95% C.L. we provide an upper limit of 1.5 neutrons cm^-2 s^-1 for the thermal
neutron flux at ~5 cm from the center of the cell. Allowing for a higher energy
neutron component the largest allowed flux is 64 neutrons cm^-2 s^-1. This
upper limit is two orders of magnitude smaller than what previously claimed in
an electrolytic cell plasma discharge experiment. Furthermore the behavior of
the CR-39 is discussed to point our possible sources of spurious signals.Comment: 4 pages, 3 figure
Silicon Photo-Multiplier radiation hardness tests with a beam controlled neutron source
We report radiation hardness tests performed at the Frascati Neutron
Generator on silicon Photo-Multipliers, semiconductor photon detectors built
from a square matrix of avalanche photo-diodes on a silicon substrate. Several
samples from different manufacturers have been irradiated integrating up to
7x10^10 1-MeV-equivalent neutrons per cm^2. Detector performances have been
recorded during the neutron irradiation and a gradual deterioration of their
properties was found to happen already after an integrated fluence of the order
of 10^8 1-MeV-equivalent neutrons per cm^2.Comment: 7 pages, 6 figures, Submitted to Nucl. Inst. Meth.
A J^PG=1++ Charged Resonance in the Y(4260) to pi+pi- J/psi Decay?
New BES and Belle data show a peak in the Y(4260) decay into J/psi plus one
charged pion. We point out that the peak might correspond to a charged
resonance at about 3880 MeV predicted time ago within a tetraquark model. The
same tetraquark model predicts another peak at about 100 MeV below the observed
one. We discuss the possibility of having it in present data. On the other hand
we expect that if the molecular picture were the correct one, a peak
corresponding to a D* D*bar state should appear at about 4020 MeV.Comment: 8 pages, 3 figures. Includes more recent Belle dat
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