Search results for "Pion"
showing 10 items of 1304 documents
Chiral Symmetry And Low Energy Pion Photoproduction
1992
The low energy theorem based on chiral symmetry for the photoproduction of neutral pions from proton at threshold is reviewed in the light of recent experimental results from Saclay and Mainz. There is no appreciable disagreement at threshold but the energy dependence of the threshold amplitude remains unexplained. A critique of the assumptions made in deriving low energy theorems by various methods is presented.
Bag models and hadron structure
2008
We review the fundamental ideas leading to the basic assumptions behind the bag model description of hadron structure and explore in some detail the so called MIT bag model. We discuss the relevance of chiral symmetry and incorporate it in a bag model scheme by adding a pion field. We show perturbative techniques of calculating gluonic and pionic effects. We discuss the consequences of the solitonic nature of the hedgehog solution of the pion field and introduce the skyrmion bag model. We end up by drawing some conclusions of our study and discussing recent developments in this area.
The role of resonances in chiral perturbation theory
1989
32 páginas, 2 figuras, 5 tablas.-- BUTP-88-18 ; CERN-TH-5185-88 ; CPT-2158 ; UWTHPH-1988-29.
Chiral dynamics in the γ→p→pπ0 reaction
2015
Abstract We investigate the neutral pion photoproduction on the proton near threshold in covariant chiral perturbation theory with the explicit inclusion of Δ degrees of freedom. This channel is specially sensitive to chiral dynamics and the advent of very precise data from the Mainz microtron has shown the limits of the convergence of the chiral series for both the heavy baryon and the covariant approaches. We show that the inclusion of the Δ resonance substantially improves the convergence leading to a good agreement with data for a wider range of energies.
Pion photo- and electroproduction in relativistic baryon chiral perturbation theory and the chiral MAID interface
2013
We present a calculation of pion photo- and electroproduction in manifestly Lorentz-invariant baryon chiral perturbation theory up to and including order ${q}^{4}$. We fix the low-energy constants by fitting experimental data in all available reaction channels. Our results can be accessed via a Web interface, the so-called chiral MAID. We explain how our program works and how it can be used for further analysis.
Pion Production at Threshold as Test of Chiral Perturbation Theory
2003
An overview of recent results in threshold pion production is given. While the photoproduction data are in impressive agreement with calculations in the framework of Chiral Perturbation Theory, electroproduction data at low four-momentum transfer show severe deviations from these calculations.
Gas-liquid chromatographic analyses of chlorination products of propionyl chloride
1981
Abstract Photochlorination of propionyl chloride with chlorine in the liquid phase at room temperature gives all eleven chloropropionyl chlorides from the mono-to the pentachloro isomer. The process was investigated every 2 h by gas-liquid chromatography, and the products were identified and estimated as their methyl esters by comparison with model compounds. The isomer distribution of the products was studied in detail. Because the process favours the 3-position, the main components were 3-chloropropionyl chloride up to 15 h, 3,3-dichloropropionyl chloride between 15 and 29 h, 3,3,3-trichloropropionyl chloride between 29 and 56 h and pentachloropropionyl chloride after 56 h of chlorination.
Ioannis Lodovici Viuis ... Sommium : Quae et praefatio ad Sommium Scipionis Ciceronis. Eisusdem Vigilia.
1521
Caplletres Port. arquitectònica
Enantiomeric separation of chiral phenoxy acid herbicides by electrokinetic chromatography. Application to the determination of analyte-selector appa…
2001
The enantiomeric resolution of chiral phenoxy acid herbicides was performed by electrokinetic chromatography using a cyclodextrin as chiral pseudophase (CD-EKC). A systematic evaluation of several neutral and charged cyclodextrins was made. Among the cyclodextrins tested, (2-hydroxy)propyl beta-cyclodextrin (HP-beta-CD) was found to be the most appropriate for the enantioseparation of phenoxy acids. The influence of some experimental conditions, such as nature and pH of the background electrolyte, chiral selector concentration, and temperature, on the enantiomeric separation of phenoxy acids was also studied. The use of a 50 mM electrolyte solution in ammonium formate at pH 5 and a temperat…
Nowe dane o rozmieszczeniu 50 gatunków ryjkowców (Coleoptera: Curculionoidea) w Polsce
2016
Fifty weevil species have been recorded from new localities in Poland. They belong to four families: Anthribidae (1), Apionidae (6), Nanophyidae (2) and Curculionidae (41). The new records, 124 in all, are from 64 UTM squares (10×10 km) in 17 of 24 regions of Poland, according to the division adopted from the Catalogus Faunae Poloniae issued in 1971-2000. Nearly half of them (57) are first records for a region. The largest numbers of the new records are from the Małopolska Upland (13), the Pomeranian Lakeland (8), Upper Silesia (7) and the Wielkopolsko-Kujawska Lowland (5). Kyklioacalles navieresi (Boh.) has been recorded from Poland for the first time, whereas K. roboris (Curtis) has been …