Photoproduction at Threshold and in the Delta Region
نویسنده
چکیده
A new partial wave analysis of pion photoproduction has been obtained in the framework of fixed-t dispersion relations valid form threshold up to 500 M eV. It is based on new Mainz data for π • and π + production off the proton and both older and more recent data from Bonn, Frascati and TRIUMF for π + and π −. At threshold we obtain a good agreement with the existing data for both charged and neutral pion production. In the resonance region we have precisely determined the electromagnetic properties of the ∆(1232) resonance, in particular the E2/M1 ratio R EM = −2.5 ± 0.1%. We show that a model independent resonance background subtraction is possible with the speed-plot technique and obtain the ∆ pole at W = (1211 − 50i) MeV and the E2/M1 ratio of the residues as R ∆ = −0.035 − 0.046i.
منابع مشابه
The Impact of Rural-Urban Migration on Poultry Production in the Niger Delta Region, Nigeria
This study was conducted to reveal the impact of rural-urban migration on broiler production in the Niger Delta Region of Nigeria. Data were collected from 795 household heads and farmers/managers/supervisors of 25 selected broiler farms in the study area. Descriptive statistics and multiple regression analysis was utilized to analyze the data. Able bodied young men constituted most of the rura...
متن کاملAssociative Photoproduction of Roper Resonance and ω-Meson
Associative photoproduction of ω-meson and N∗(1440) on nucleons, γ + N → ω + N∗(1440), in the near threshold region is investigated in a framework employing effective Lagrangians. Besides π-exchange in t-channel, baryon exchanges, i.e. Nand N∗-exchanges, in the sand u-channels are also taken into account in calculations of differential cross-section and beam asymmetry. Important inputs of this ...
متن کاملThe Lifetime Behavior of a New Discrete Time Mixed $delta$-shock Model
In this study, a mixed $delta$-shock model with discrete-time is defined by combining $delta$-shock and extreme shock models. In this model, a system with multiple states fails in two ways: first, when k interarrival times between two consecutive shocks with magnitude larger than the critical threshold $gamma$ are in $[delta_1, delta _2], delta_1 < delta _2$; and second, when the interarrival t...
متن کاملω-Meson Photoproduction on Nucleons In the Near Threshold Region
The ω-meson photoproduction, γ+p → p+ω, is studied in the framework of a model, containing π-meson exchange in t-channel and nucleon-exchange in sand u-channels. Considering both ωNN -coupling constants in the region of time-like meson four momenta as the free parameters, we find different sets of solutions for these constants from the existing data on the t-dependence of the differential cross...
متن کامل