18 research outputs found
Longitudinal Momentum Fraction X_L for Two High P_t Protons in pp->ppX Reaction
We present an analysis of new data from Experiment E850 at BNL. We have
characterized the inclusive cross section near the endpoint for pp exclusive
scattering in Hydrogen and in Carbon with incident beam energy of 6 GeV. We
select events with a pair of back-to-back hadrons at large transverse momentum.
These cross sections are parameterized with a form
, where is the ratio of the longitudinal momentum
of the observed pair to the total incident beam momentum. Small value of
may suggest that the number of partons participating in the reaction is large
and reaction has a strong dependence on the center-of-mass energy. We also
discuss nuclear effects observed in our kinematic region.Comment: 4 pages, 2 figures, to be published in Proceedings of CIPANP2000,
Quebec, May 22-28, 2000, requires aipproc.sty(included
Energy Dependence of Nuclear Transparency in C(p,2p) Scattering
The transparency of carbon for (p,2p) quasi-elastic events was measured at
beam energies ranging from 6 to 14.5 GeV at 90 degrees c.m. The four momentum
transfer squared q*q ranged from 4.8 to 16.9 (GeV/c)**2. We present the
observed energy dependence of the ratio of the carbon to hydrogen cross
sections. We also apply a model for the nuclear momentum distribution of carbon
to normalize this transparency ratio. We find a sharp rise in transparency as
the beam energy is increased to 9 GeV and a reduction to approximately the
Glauber level at higher energies.Comment: 4 pages, 2figures, submitted to PR
Practical divide-and-conquer algorithms for polynomial arithmetic
We investigate two practical divide-and-conquer style algorithms for univariate polynomial arithmetic. First we revisit an algorithm originally described by Brent and Kung for composition of power series, showing that it can be applied practically to composition of polynomials in Z[x] given in the standard monomial basis. We offer a complexity analysis, showing that it is asymptotically fast, avoiding coefficient explosion in Z[x]. Secondly we provide an improvement to Mulders' polynomial division algorithm. We show that it is particularly efficient compared with the multimodular algorithm. The algorithms are straightforward to implement and available in the open source FLINT C library. We offer a practical comparison of our implementations with various computer algebra systems
Continuous Wave and Time-Resolved Electron Paramagnetic Resonance Study of Photoinduced Radicals in Fluoroacrylic Porous Polymer Films
Fluoroacrylic polymers with inherent
micro/nanoporosity are promising
media for incorporation of fluorescent molecules and following application
as pressure-sensitive paints (PSPs), and UV photostability of PSPs
is critically important for their long-term performance. Although
photodegradation mechanisms of fluoroacrylic polymers have been studied
previously in solutions, they have never been addressed in practically
relevant for PSPs solid-state porous films. In this work we combined
continuous wave (CW) and time-resolved (TR) electron paramagnetic
resonance (EPR) to study UV photodegradation of thin porous films
of a few representative fluoroacrylic polymers. Different types of
spectra were detected using CW and TR EPR and assigned to the species
formed on the inner surface of the pores and in the bulk of the polymer,
respectively. The radical pairs formed in the bulk are short-lived,
as is evidenced by TR EPR, and most likely recombine back to the initial
polymer. On the contrary, the radicals formed on the surface of the
pores are metastable in the absence of oxygen; they can be studied
by CW EPR and clearly assigned to the radicals of type ·C(CH<sub>3</sub>)CH<sub>2</sub>– (so-called propagating radicals) formed
via the cleavage of the C–C bond of the ester side chains and
consecutive β-scission. Remarkably, their CW EPR spectra closely
resemble solution-state spectra, indicating that these radicals are
localized in the pores where the mobility of methyl and methylene
protons is not suppressed. Thus, based on complementary results of
CW and TR EPR, we conclude that UV photodegradation of porous fluoroacrylic
polymer films mainly occurs on the inner surface of the pores, which
needs to be considered in future development of this type PSPs