Search results for "Nucleon"
showing 10 items of 1041 documents
Role of the D 13 and S 11 Resonances in Deuteron Photodisintegration
1995
The influence of the N(1520) and N(1535) isobar resonances in deuteron photodisintegration is investigated. The isobar configurations are treated in impulse approximation using one-pion exchange for the transition potentials. Isobar admixtures are included in scattering waves as well as in the deuteron. Their influence on the total and differential cross section and various polarization observables, e.g., nucleon polarization and photon asymmetry is small in the Δ resonance region, but not any longer negligible at higher energies.
Signatures of the d*(2380) Hexaquark in d(γ,pn→)
2020
We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured photon energy range of 300-700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E_{γ}∼570 MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition sugge…
Polarization Effects in Photo- and Electrodisintegration of the Deuteron
1986
Polarization observables in deuteron photodisintegration like photon and target asymmetries and one- and two nucleon polarization of the final state are studied with respect to their sensitivity to subnuclear degrees of freedom. Furthermore it is shown that the electric form factor of the neutron has a sizeable influence on the polarization asymmetry in d(\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}}{e}\),e’n)p with polarized electrons. Uncertainties arising from potential model dependence are discussed.
Nucleon structure observables with PANDA
2017
The PANDA detector will be built as a part of the future FAIR facility in Darmstadt. The availability of an antiproton beam with beam momenta up to 15 GeV/c will make possible a broad nuclear physics program. Topics like hadron spectroscopy in the charmonium mass region, the property of hadrons inside nuclear matter, hypernuclear physics, or nucleon properties using electromagnetic processes are part of the physics program of PANDA. The main part of this contribution concentrates on the feasibility of measurement of nucleon structure observables, such as electromagnetic form factors or transition distribution amplitudes, via experiments using electromagnetic processes in PANDA.
Computing the nucleon Dirac radius directly at $Q^2=0$
2016
We describe a lattice approach for directly computing momentum derivatives of nucleon matrix elements using the Rome method, which we apply to obtain the isovector magnetic moment and Dirac radius. We present preliminary results calculated at the physical pion mass using a 2HEX-smeared Wilson-clover action. For removing the effects of excited-state contamination, the calculations were done at three source-sink separations and the summation method was used.
Effect of a Triaxial Nuclear Shape on Proton Tunneling: The Decay and Structure of 145Tm
2007
Gamma rays deexciting states in the proton emitter 145Tm were observed using the recoil-decay tagging method. The 145Tm ground-state rotational band was found to exhibit the properties expected for an h{11/2} proton decoupled band. In addition, coincidences between protons feeding the 2{+} state in 144Er and the 2{+}-->0{+} gamma-ray transition were detected, the first measurement of this kind, leading to a more precise value for the 2{+} excitation energy of 329(1) keV. Calculations with the particle-rotor model and the core quasiparticle coupling model indicate that the properties of the pi{11/2} band and the proton-decay rates in 145Tm are consistent with the presence of triaxiality with…
Direct Observation of aρDecay of theD13(1520)Baryon Resonance
2001
The reaction {gamma}p{yields}{pi}{sup +}{pi}{sup 0}n has been measured at MAMI for photon energies up to 820MeV. Invariant mass spectra of the particles in the final state ({pi}{sup +}n) , ({pi}{sup 0}n) , ({pi}{sup +}{pi}{sup 0}) have been determined for several bins of incident photon energy. Differences in {pi}{sup +}{pi}{sup 0} and simultaneously measured {pi}{sup 0}{pi}{sup 0} invariant mass distributions are assigned to a {rho} branch of the D{sub 13}(1520) nucleon resonance.
Recoil Polarization and Beam-Recoil Double Polarization Measurement ofηElectroproduction on the Proton in the Region of theS11(1535)Resonance
2007
The beam-recoil double polarization P{sub x{sup '}}{sup h} and P{sub z{sup '}}{sup h} and the recoil polarization P{sub y{sup '}} were measured for the first time for the p(e-vector,e{sup '}p-vector){eta} reaction at a four-momentum transfer of Q{sup 2}=0.1 GeV{sup 2}/c{sup 2} and a center of mass production angle of {theta}=120 deg. at the Mainz Microtron MAMI-C. With a center of mass energy range of 1500 MeV<W<1550 MeV the region of the S{sub 11}(1535) and D{sub 13}(1520) resonance was covered. The results are discussed in the framework of a phenomenological isobar model (Eta-MAID). While P{sub x{sup '}}{sup h} and P{sub z{sup '}}{sup h} are in good agreement with the model, P{sub y{sup '…
Coulomb Excitation ofCu68,70: First Use of Postaccelerated Isomeric Beams
2007
We report on the first low-energy Coulomb excitation measurements with radioactive Ipi=6- beams of odd-odd nuclei 68,70Cu. The beams were produced at ISOLDE, CERN and were post-accelerated by REX-ISOLDE to 2.83 MeV/nucleon. gamma rays were detected with the MINIBALL spectrometer. The 6- beam was used to study the multiplet of states (3-, 4-, 5-, 6-) arising from the pi2p3/2nu1g9/2 configuration. The 4- state of the multiplet was populated via Coulomb excitation and the B(E2;6--->4-) value was determined in both nuclei. The results obtained illustrate the fragile stability of the Z=28 shell and N=40 subshell closures. A comparison with large-scale shell-model calculations using the 56Ni core…
Spectroscopy of Cd98 by two-nucleon removal from In100
2021
Low-lying states of Cd-98 have been populated by the two-nucleon removal reaction (In-100, Cd-98+gamma) and studied using in-beam gamma-ray spectroscopy at the Radioactive Isotope Beam Factory at RIKEN. Two new gamma transitions were identified and assigned as decays from a previously unknown state. This state is suggested to be based on a pi 1g(/9/2)(-1)2p(1/2)(-2) configuration with J(pi) = 5(-). The present observation extends the systematics of the excitation energies of the first 5(-) state in N = 50 isotones toward Sn-100. The determined energy of the 5(- )state in Cd-98 continues a smooth trend along the N = 50 isotones. The systematics are compared with shell-model calculations in d…