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Register a new userMeasurement of the Enhanced Screening Effect of the d+d Reactions in Metals
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The investigation of the d+d fusion reactions in metallic environments at sub-Coulomb energies demands especially adapted techniques beyond standard procedures in nuclear physics. The measurements which were performed with an electrostatic accelerator at different self-implanted metallic target materials show an enhancement of the reaction cross-section compared to the gas target experiments. The resulting electron screening energy values are about one order of magnitude larger relative to the gas target experiments and exceed significantly the theoretical predictions. The measurements on deuterium inside metals are heavily affected by the interference of two peculiarities of this system: the possibly very high mobility of deuterium in solids and the formation of surface contamination layers under ion beam irradiation in high vacuum systems. Thorough investigations of these processes show their crucial influence on the interpretation of the experimental raw data. The differential data acquisition and analysis method employed to it is outlined. Non observance of these problems by using standard procedures results in fatal errors for the extraction of the screening energies.
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The Bochum experimental enhancement of the d+d fusion rate in a deuterated metal matrix at low incident energies is explained by the quantum broadening of the momentum-energy dispersion relation and consequent modification of the high-momentum tail of the distribution function from an exponential to a power-law.
New data on the tensor analyzing power Ayy of the ^9Be(d,p)X reaction at an initial deuteron momentum of 5 GeV/c and secondary particles (protons and deuterons) detection angle of 178 mr have been obtained at the JINR Synchrophasotron. The proton data obtained are analyzed within the framework of an approach based on the light-front dynamics using Karmanovs relativistic deuteron wave function. Contrary to the calculations with standard non-relativistic deuteron wave functions, we have managed to explain the new data within the framework of our approach without invoking degrees of freedom additional to nucleon ones. The ^9Be(d,d)X data are obtained in the vicinity of the excitation of baryonic resonances with masses up to 1.8 GeV/c^2. The Ayy data are in a good agreement with the previous data obtained at 4.5 and 5.5 GeV/c when they are plotted versus $t$. The results of the experiment are compared with the predictions of the plane wave impulse approximation and omega-meson exchange models.
We report first measurements of e+e- -> D(*)+D(*)- processes far above threshold. The cross-sections for e+e- -> DT*+DL*- and e+e- -> D+D*T- at sqrt{s}=10.58 GeV/c2 are measured to be 0.55 +- 0.03 +- 0.05 pb and 0.62 +- 0.03 +- 0.06 pb, respectively. We set upper limits on the cross-sections for e+e- -> DT*+DT*-, e+e- -> DL*+DL*-, e+e- -> D+D*L- and e+e- -> D+D- processes. The analysis is based on 88.9 fb-1 of data collected by the Belle experiment at the KEKB e+e- asymmetric collider.
Theoretical models of the (d,p) reaction are exploited for both nuclear astrophysics and spectroscopic studies in nuclear physics. Usually, these reaction models use local optical model potentials to describe the nucleon- and deuteron-target interactions. Within such a framework the importance of the deuteron D-state in low-energy reactions is normally associated with spin observables and tensor polarization effects - with very minimal influence on differential cross sections. In contrast, recent work that includes the inherent nonlocality of the nucleon optical model potentials in the Johnson-Tandy adiabatic-model description of the (d,p) transition amplitude, which accounts for deuteron break-up effects, shows sensitivity of the reaction to the large n-p relative momentum content of the deuteron wave function. The dominance of the deuteron D-state component at such high momenta leads to significant sensitivity of calculated (d,p) cross sections and deduced spectroscopic factors to the choice of deuteron wave function [Phys. Rev. Lett. {bf 117}, 162502 (2016)]. We present details of the Johnson-Tandy adiabatic model of the (d,p) transfer reaction generalized to include the deuteron D-state in the presence of nonlocal nucleon-target interactions. We present exact calculations in this model and compare these to approximate (leading-order) solutions. The latter, approximate solutions can be interpreted in terms of local optical potentials, but evaluated at a shifted value of the energy in the nucleon-target system. This energy shift is increased when including the D-state contribution. We also study the expected dependence of the D-state effects on the separation energy and orbital angular momentum of the transferred nucleon. Their influence on the spectroscopic information extracted from (d,p) reactions is quantified for a particular case of astrophysical significance.
Existing measurements of the angular distributions of the ground-state to ground-state transitions of the 12C(d,p)13C and 13C(p,d)12C neutron-transfer reactions have been analyzed systematically using the Johnson-Soper adiabatic and distorted-wave theories. When using a consistent set of physical inputs the deduced spectroscopic factors are consistent to within 20% for incident deuteron energies from 6 to 60 MeV. By contrast, original analyses of many of these data quoted spectroscopic factors that differed by up to a factor of five. The present analysis provides an important reference point from which to assess the requirements of future spectroscopic analyses of transfer reactions measured in inverse kinematics using rare nuclei.
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