1,007 research outputs found
The Mellin Transform Technique for the Extraction of the Gluon Density
A new method is presented to determine the gluon density in the proton from
jet production in deeply inelastic scattering. By using the technique of Mellin
transforms not only for the solution of the scale evolution equation of the
parton densities but also for the evaluation of scattering cross sections, the
gluon density can be extracted in next-to-leading order QCD. The method
described in this paper is, however, more general, and can be used in
situations where a repeated fast numerical evaluation of scattering cross
sections for varying parton distribution functions is required.Comment: 13 pages (LaTeX); 2 figures are included via epsfig; the
corresponding postscript files are uuencode
A transportable strontium optical lattice clock
We report on a transportable optical clock, based on laser-cooled strontium
atoms trapped in an optical lattice. The experimental apparatus is composed of
a compact source of ultra-cold strontium atoms including a compact cooling
laser set-up and a transportable ultra-stable laser for interrogating the
optical clock transition. The whole setup (excluding electronics) fits within a
volume of less than 2 m. The high degree of operation reliability of both
systems allowed the spectroscopy of the clock transition to be performed with
10 Hz resolution. We estimate an uncertainty of the clock of .Comment: 12 pages, 9 figures, to be published in Appl. Phys.
Electrochemical polymerisation of phenol in aqueous solution on a Ta/PbO2 anode
This paper deals with the treatment of aqueous phenol solutions using an electrochemical technique. Phenol can be partly eliminated from aqueous solution by electrochemically initiated polymerisation. Galvanostatic electrolyses of phenol solutions at concentration up to 0.1 mol dm−3 were carried out on a Ta/PbO2 anode. The polymers formed are insoluble in acidic medium but soluble in alkaline. These polymers were filtered and then dissolved in aqueous solution of sodium hydroxide (1 mol dm−3). The polymers formed were quantified by total organic carbon (TOC) measurement. It was found that the conversion of phenol into polymers increases as a function of initial concentration, anodic current density, temperature, and solution pH. The percentage of phenol polymerised can reach 15%
Gravity with extra dimensions and dark matter interpretation: Phenomenological example via Miyamoto-Nagai galaxy
A configuration whose density profile coincides with the Newtonian potential
for spiral galaxies is constructed from a 4D isotropic metric plus extra
dimensional components. A Miyamoto-Nagai ansatz is used to solve Einstein
equations. The stable rotation curves of such system are computed and, without
fitting techniques, we recover with accuracy the observational data for flat or
not asymptotically flat galaxy rotation curves. The density profiles are
reconstructed and compared to that obtained from the Newtonian potential.Comment: 10 pages, 10 figures, submitted to Brazilian Journal of Physic
Strong Electron-Phonon Coupling in Superconducting MgB: A Specific Heat Study
We report on measurements of the specific heat of the recently discovered
superconductor MgB in the temperature range between 3 and 220 K. Based on a
modified Debye-Einstein model, we have achieved a rather accurate account of
the lattice contribution to the specific heat, which allows us to separate the
electronic contribution from the total measured specific heat. From our result
for the electronic specific heat, we estimate the electron-phonon coupling
constant to be of the order of 2, significantly enhanced compared to
common weak-coupling values . Our data also indicate that the
electronic specific heat in the superconducting state of MgB can be
accounted for by a conventional, s-wave type BCS-model.Comment: 4 pages, 4 figure
Spectroscopy of the neutron-rich actinide nucleus U-240 following multinucleon-transfer reactions
B. Birkenbach et al.; 9 pags.; 9 figs.; 2 tabs.; PACS number(s): 23.20.Lv, 25.70.Hi, 27.90.+b, 29.40.GxBackground: Nuclear structure information for the neutron-rich actinide nuclei is important since it is the benchmark for theoretical models that provide predictions for the heaviest nuclei. Purpose: gamma-ray spectroscopy of neutron-rich heavy nuclei in the actinide region. Method: Multinucleon-transfer reactions in Zn-70 + U-238 and Xe-136 + U-238 have been measured in two experiments performed at the INFN Legnaro, Italy. In the Zn-70 experiment the high-resolution HPGe Clover Array (CLARA) coupled to the magnetic spectrometer PRISMA was employed. In the Xe-136 experiment the high-resolution Advanced Gamma Tracking Array (AGATA) was used in combination with PRISMA and the Detector Array for Multinucleon Transfer Ejectiles (DANTE). Results: The ground-state band (g.s. band) of U-240 was measured up to the 20(+) level and a tentative assignment was made up to the (24(+)) level. Results from gamma gamma coincidence and from particle coincidence analyses are shown. Moments of inertia (MoI) show a clear upbend. Evidence for an extended first negative-parity band of U-240 is found. Conclusions: A detailed comparison with latest calculations shows best agreement with cranked relativistic Hartree-Bogoliubov (CRHB) calculations for the g.s. band properties. The negative-parity band shows the characteristics of a K-pi = 0 band based on an octupole vibration. ©2015 American Physical SocietyThe research leading to these results has received
funding from the German Bundesministerium fur Bildung ¨
und Forschung (BMBF) under Contract No. 05P12PKFNE
TP4, the European Union Seventh Framework Programme
(FP7/2007-2013) under Grant No. 262010-ENSAR, and the
Spanish Ministerio de Ciencia e Innovacion under Contract
No. FPA2011-29854-C04. A.V. thanks the Bonn-Cologne
Graduate School of Physics and Astronomy (BCGS) for
financial support. One of the authors (A. Gadea) was supported
by MINECO, Spain, under Grants No. FPA2011-29854-C04
759 and No. FPA2014-57196-C5; Generalitat Valenciana,
Spain, under Grant No. PROMETEOII/2014/019; and EU
under the FEDER program.Peer Reviewe
Heavy Quark Photoproduction in Ultra-peripheral Heavy Ion Collisions
Heavy quarks are copiously produced in ultra-peripheral heavy ion collisions.
In the strong electromagnetic fields, c c-bar and b b-bar are produced by
photonuclear and two-photon interactions; hadroproduction can occur in grazing
interactions. We present the total cross sections, quark transverse momentum
and rapidity distributions, as well as the Q Q-bar invariant mass spectra from
the three production channels. We consider AA and pA collisions at the
Relativistic Heavy Ion Collider and Large Hadron Collider. We discuss
techniques for separating the three processes and describe how the AA to pA
production ratios might be measured accurately enough to study nuclear
shadowing.Comment: Minor changes to satisfy referees and typo fixes; 52 pages including
17 figure
Development of a strontium optical lattice clock for the SOC mission on the ISS
The ESA mission "Space Optical Clock" project aims at operating an optical
lattice clock on the ISS in approximately 2023. The scientific goals of the
mission are to perform tests of fundamental physics, to enable space-assisted
relativistic geodesy and to intercompare optical clocks on the ground using
microwave and optical links. The performance goal of the space clock is less
than uncertainty and
instability. Within an EU-FP7-funded project, a strontium optical lattice clock
demonstrator has been developed. Goal performances are instability below and fractional inaccuracy .
For the design of the clock, techniques and approaches suitable for later space
application are used, such as modular design, diode lasers, low power
consumption subunits, and compact dimensions. The Sr clock apparatus is fully
operational, and the clock transition in Sr was observed with linewidth
as small as 9 Hz.Comment: 12 pages, 8 figures, SPIE Photonics Europe 201
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