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 $\frac{d \sigma}{d X_{L}}$ $\sim(1-X_{L})^{p}$, where ${X_{L}}$ is the ratio of the longitudinal momentum of the observed pair to the total incident beam momentum. Small value of $p$ 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

Задача № 3 Дифференциальная диагностика кистозных образований легких

.

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(CH₃)­CH₂– (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