Search results for "EXCITATION"
showing 10 items of 1290 documents
Gamow-Teller transitions in theA=40isoquintet of relevance for neutrino captures inAr40
2014
Background: The Gamow-Teller response of $^{40}\mathrm{Ar}$ is important for the use of liquid argon as a medium for neutrino detection. An ambiguity about the Gamow-Teller strength for the excitation of ${1}^{+}$ states at 2290 and 2730 keV in $^{40}\mathrm{K}$ results in a significant uncertainty for neutrino capture rates. This ambiguity is caused by the large discrepancy observed between strengths extracted from $^{40}\mathrm{Ar}$($p$, $n$) charge-exchange data and the transition strengths for the analog transitions studied in the $\ensuremath{\beta}$ decay of $^{40}\mathrm{Ti}$.Purpose: This study was aimed at resolving the ambiguity between the results from the $^{40}\mathrm{Ar}$($p$,…
Isoscalar Roper(N1440*)excitation in thepp→ppπ0reaction close to threshold
1999
A new mechanism for the $p\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{pp}{\ensuremath{\pi}}^{0}$ reaction close to threshold is suggested coming from the isoscalar excitation of the Roper and its decay into $N(\ensuremath{\pi}\ensuremath{\pi}{)}_{s\ensuremath{-}\mathrm{w}\mathrm{a}\mathrm{v}\mathrm{e}},$ with one of the ${\ensuremath{\pi}}^{0}$ emitted and the other one reabsorbed on the second nucleon. We show that this new mechanism can lead to important interference with other mechanisms suggested so far.
Predictions for η→ηπ+π− producing f0(500), f0(980) and a0(980)
2017
Abstract We perform calculations for the η c → η π + π − decay using elements of SU(3) symmetry to see the weight of different trios of pseudoscalars produced in this decay, prior to the final state interaction of the mesons. After that, the interaction of pairs of mesons, leading finally to η π + π − , is done using the chiral unitary approach. We evaluate the π + π − and πη mass distributions and find large and clear signals for f 0 ( 500 ) , f 0 ( 980 ) and a 0 ( 980 ) excitation. The reaction is similar to the χ c 1 → η π + π − , which has been recently measured at BESIII and its implementation and comparison with these predictions will be very valuable to shed light on the nature of th…
Coherent two pion photoproduction on C-12
1997
We develop the formalism for coherent two pion photoproduction in nuclei and perform actual calculations of cross sections for $\pi^-\pi^+$ and $\pi^0\pi^0$ photoproduction on $^{12}C$. We find that due to the isospin symmetry the cross section for $\pi^0\pi^0$ production is very small and has a maximum when the pions propagate together. However, the kinematical region where the energies and polar angles of the two $\pi^0$ mesons are equal and their relative azimuthal angle $\phi=180^0$ is forbidden. Conversely in the $\pi^-\pi^+$ production the pions prefer to have a relative azimuthal angle 180$^0$ and the production of the pions propagating together is suppressed. The dominant one-body m…
The role of Delta(1700) excitation and rho production in double pion photoproduction
2001
Recent information on invariant mass distributions of the $\gamma p\to\pi^+\pi^0 n$ reaction, where previous theoretical models had shown deficiencies, have made more evident the need for new mechanisms, so far neglected or inaccurately included. We have updated a previous model to include new necessary mechanisms. We find that the production of the $\rho$ meson, and the $\Delta(1700)$ excitation, through interference with the dominant terms, are important mechanisms that solve the puzzle of the $\gamma p\to\pi^+\pi^0 n$ reaction without spoiling the early agreement with the $\gamma p\to\pi^+\pi^- p$ and $\gamma p\to\pi^0\pi^0 p$ reactions.
A consistent explanation of the Roper phenomenology
1998
We study the electromagnetic transitions of the Roper N(1440) resonance. Our results, when combined with the previously obtained for the mass and the pionic strong decay widths of the Roper, show that within a non-relativistic constituent quark model scheme, a comprehensible understanding of the Roper phenomenology can be achieved. They also seem to support the view of the Roper as a radial excitation of the nucleon, though more experimental data are needed to reach a definitive conclusion.
Double pion photoproduction on the nucleon: study of the isospin channels
1995
A model for the gamma p ----> pion+ pion- p reaction developed earlier is extended to account for all isospin channels. The model includes N, Delta(1232), N^*(1440) and N^*(1520) as intermediate baryonic states and the rho-meson as an intermediate two pion resonance. Although many terms contribute to the cross section, some channels exhibit particular sensitivity to certain mechanisms of resonance excitation or decay and the reactions provide novel information on such mechanisms. In particular the gamma N ----> N^*(1520) ----> Delta(1232) pion process affects all the channels and is a key ingredient in the interpretation of the data. Comparison is made with all available data and t…
The two particle-phonon multiplet ?h 11/2 ?f 7/2 � 3? and higher-lying four-nucleon yrast states in the doubly-odd nucleus 146 63 Eu83
1988
From in-beamγ-ray measurements we have established the high-spin states in146Eu up to 3.5 MeV excitation andIπ=(15+). The highest levels observed are formed by alignment of four nucleons, involving excitation of the144Sm core. Negative-parity states at about 2 MeV are classified asπh11/2νf7/2 × 3− octupole excitations. Quantitative analyses for the octupole multiplet members and for theν=4 states based on empirical data from neighbouring nuclei are presented.
Optical measurement of the longitudinal ion distribution of bunched ion beams in the ESR
2013
Abstract An optical technique to study the longitudinal distribution of ions in a bunched ion beam circulating in a storage ring is presented. It is based on the arrival-time analysis of photons emitted after collisional excitation of residual gas molecules. The beam-induced fluorescence was investigated in the ultraviolet regime with a channeltron and in the visible region using a photomultiplier tube. Both were applied to investigate the longitudinal shape of bunched and electron-cooled 209Bi80+ ion beams at about 400 MeV/u in the experimental storage ring (ESR) at GSI Helmholtzzentrum fur Schwerionenforschung in Darmstadt, Germany. Bunch lengths were determined with an uncertainty of abo…
K+Λ and K+Σ0 photoproduction with fine center-of-mass energy resolution
2014
Measurements of γp→K+Λγp→K+Λ and γp→K+Σ0γp→K+Σ0 cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel K+K+ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy (W) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. The new analyses disfavor a strong role for quark–diqua…