4,343 research outputs found
Analysing powers for the reaction and for np elastic scattering from 270 to 570 MeV
The analysing power of the reaction for neutron energies between threshold and 570 MeV has been determined
using a transversely polarised neutron beam at PSI. The reaction has been
studied in a kinematically complete measurement using a time-of-flight
spectrometer with large acceptance. Analysing powers have been determined as a
function of the c.m. pion angle in different regions of the proton-proton
invariant mass. They are compared to other data from the reactions and . The np elastic scattering analysing power was determined as a
by-product of the measurements.Comment: 12 pages, 6 figures, subitted to EPJ-
The reaction from threshold up to 570 MeV
The reaction has been studied in a
kinematically complete measurement with a large acceptance time-of-flight
spectrometer for incident neutron energies between threshold and 570 MeV. The
proton-proton invariant mass distributions show a strong enhancement due to the
pp() final state interaction. A large anisotropy was found in the
pion angular distributions in contrast to the reaction . At small energies, a large forward/backward asymmetry has been
observed. From the measured integrated cross section , the isoscalar cross section has been extracted.
Its energy dependence indicates that mainly partial waves with Sp final states
contribute. Note: Due to a coding error, the differential cross sections as shown in Fig. 9 are too small by a factor of two, and
inn Table 3 the differential cross sections
are too large by a factor of . The integrated cross sections and all
conclusions remain unchanged. A corresponding erratum has been submitted and
accepted by European Physics Journal.Comment: 18 pages, 16 figure
New Exclusion Limits for the Search of Scalar and Pseudoscalar Axion-Like Particles from "Light Shining Through a Wall"
Physics beyond the Standard Model predicts the possible existence of new
particles that can be searched at the low energy frontier in the sub-eV range.
The OSQAR photon regeneration experiment looks for "Light Shining through a
Wall" from the quantum oscillation of optical photons into "Weakly Interacting
Sub-eV Particles", such as axion or Axion-Like Particles (ALPs), in a 9 T
transverse magnetic field over the unprecedented length of m.
In 2014, this experiment has been run with an outstanding sensitivity, using an
18.5 W continuous wave laser emitting in the green at the single wavelength of
532 nm. No regenerated photons have been detected after the wall, pushing the
limits for the existence of axions and ALPs down to an unprecedented level for
such a type of laboratory experiment. The di-photon couplings of possible
pseudo-scalar and scalar ALPs can be constrained in the nearly massless limit
to be less than GeV and
GeV, respectively, at 95% Confidence Level.Comment: 6 pages, 6 figure
Polarised target for Drell-Yan experiment in COMPASS at CERN, part I
In the polarised Drell-Yan experiment at the COMPASS facility in CERN pion
beam with momentum of 190 GeV/c and intensity about pions/s interacted
with transversely polarised NH target. Muon pairs produced in Drel-Yan
process were detected. The measurement was done in 2015 as the 1st ever
polarised Drell-Yan fixed target experiment. The hydrogen nuclei in the
solid-state NH were polarised by dynamic nuclear polarisation in 2.5 T
field of large-acceptance superconducting magnet. Large helium dilution
cryostat was used to cool the target down below 100 mK. Polarisation of
hydrogen nuclei reached during the data taking was about 80 %. Two oppositely
polarised target cells, each 55 cm long and 4 cm in diameter were used.
Overview of COMPASS facility and the polarised target with emphasis on the
dilution cryostat and magnet is given. Results of the polarisation measurement
in the Drell-Yan run and overviews of the target material, cell and dynamic
nuclear polarisation system are given in the part II.Comment: 4 pages, 2 figures, Proceedings of the 22nd International Spin
Symposium, Urbana-Champaign, Illinois, USA, 25-30 September 201
EFFECT OF SITE AND COMPETITION ON DIAMETER GROWTH OF Araucaria angustifolia
Although the historical interest in using the wood of Araucaria angustifolia, it is still little known concerning the factors that affect the growth. A broader understanding in this context might contribute to the development of appropriate management systems, thus increasing the productivity of plantations and, consequently, the interest in commercially using this species. The present study was based on monospecific populations established in different site conditions (Site Indices between 18-24) where individuals (n=654) were submitted to different competition levels. With the aid of multiple regression techniques, the factors that significantly affected the accumulated growth in diameter of the trees after 20 years of intervention were determined. For the set formed by all trees, 77% of the growth variation can be explained by three factors: site, the proportion of tree diameter at breast height (dbh) of the object tree for analysis in relation to the average dbh of the population before performing the clearings (Cdbh_before) and dominance status in relation to the neighboring trees (Call). The significance of the competition level before the clearing shows that late clearings have limited effects on tree growth. It is concluded that individuals are benefited for having a dominant position in relation to the neighboring trees, reaching diameters 50% larger at the end of the production cycle. Clearings that favour selected trees by removing direct competitors seem to be an interesting management strategy for the species.Keywords: Paraná-pine; Forest Management; Silviculture; Timber Production
Search for weakly interacting sub-eV particles with the OSQAR laser-based experiment: results and perspectives
Recent theoretical and experimental studies highlight the possibility of new
fundamental particle physics beyond the Standard Model that can be probed by
sub-eV energy experiments. The OSQAR photon regeneration experiment looks for
"Light Shining through a Wall" (LSW) from the quantum oscillation of optical
photons into "Weakly Interacting Sub-eV Particles" (WISPs), like axion or
axion-like particles (ALPs), in a 9 T transverse magnetic field over the
unprecedented length of m. No excess of events has been
detected over the background. The di-photon couplings of possible new light
scalar and pseudo-scalar particles can be constrained in the massless limit to
be less than GeV. These results are very close to the
most stringent laboratory constraints obtained for the coupling of ALPs to two
photons. Plans for further improving the sensitivity of the OSQAR experiment
are presented.Comment: 7 pages, 7 figure
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