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Register a new userCoupled reaction channel study of the 12C(alpha,8Be) reaction, and the 8Be+8Be optical potential
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Given the established 2 alpha structure of 8Be, a realistic model of 4 interacting alpha clusters must be used to obtain a 8Be+8Be interaction potential. Such a four-body problem poses a challenge for the determination of the 8Be+8Be optical potential (OP) that is still unknown due to the lack of the elastic 8Be+8Be scattering data. The main goal of the present study is to probe the complex 8Be+8Be optical potential in the coupled reaction channel (CRC) study of the alpha transfer 12C(alpha,8Be) reaction measured at 65 MeV, and to obtain the spectroscopic information on the alpha+8Be cluster configuration of 12C. The 3- and 4-body Continuum-Discretized Coupled Channel (CDCC) methods are used to calculate the elastic alpha+8Be and 8Be+8Be scattering at the energy around 16 MeV/nucleon, with the breakup effect taken into account explicitly. Using the CDCC-based OP and alpha spectroscopic factors given by the cluster model calculation, a good CRC description of the alpha transfer data without any adjustment of the (complex) potential strength.
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The possible occurence of highly deformed configurations in the $^{40}$Ca di-nuclear system formed in the $^{28}$Si + $^{12}$C reaction is investigated by analyzing the spectra of emitted light charged particles. Both inclusive and exclusive measurements of the heavy fragments (A $geq$ 10) and their associated light charged particles (protons and $alpha$ particles) have been made at the IReS Strasbourg {sc VIVITRON} Tandem facility at bombarding energies of $E_{lab}$ ($^{28}$Si) = 112 MeV and 180 MeV by using the {sc ICARE} charged particle multidetector array. The energy spectra, velocity distributions, in-plane and out-of-plane angular correlations of light charged particles are compared to statistical-model calculations using a consistent set of parameters with spin-dependent level densities. This spin dependence approach suggests the onset of large nuclear deformation in $^{40}$Ca at high spin. This conclusion might be connected with the recent observation of superdeformed bands in the $^{40}$Ca nucleus. The analysis of $alpha$ particles in coincidence with $^{32}$S fragments suggests a surprisingly strong $^{8}$Be cluster emission of a binary nature.
A $6.8,sigma$ anomaly has been reported in the opening angle and invariant mass distributions of $e^+e^-$ pairs produced in ${^8Be}$ nuclear transitions. It has been shown that a protophobic fifth force mediated by a $17,textrm{MeV}$ gauge boson $X$ with pure vector current interactions can explain the data through the decay of an excited state to the ground state, ${^8Be^*} to {^8Be}, X$, and then the followed saturating decay $X to e^+e^-$. In this work we propose a renormalizable model to realize this fifth force. Although axial-vector current interactions also exist in our model, their contributions cancel out in the iso-scalar interaction for ${^8Be^*} to {^8Be} ,X$. Within the allowed parameter space, this model can alleviate the $(g-2)_mu$ anomaly problem and can be probed by the LHCb experiment. Several other implications are discussed.
We apply tensor version of antisymmetrized quasi cluster model (AQCM-T) to 4He and 8Be while focusing on the NN correlations in alpha clusters. We adopt the NN interactions including realistic ones containing a repulsive core for the central part in addition to the tensor part. In 4He, the pn pair in the 3D channel has been known to play a decisive role in the tensor correlation and the framework is capable of treating not only this channel but also the NN correlations in the 1S and 3S channels. In 8Be, when two alpha clusters approach, the 3D pair is suppressed because of the Pauli blocking effect, which induces the decrease of the 3S component through the 3S-3D coupling. This effect results in the reduction of the attractive effect of the central-even interaction in the middle-range region.
A significant decay branch of 8B to the ground state of 8Be would extend the solar neutrino spectrum to higher energies than anticipated in the standard solar models. These high-energy neutrinos would affect current neutrino oscillation results and also would be a background to measurements of the hep process. We have measured the delayed alpha particles from the decay of 8B, with the goal of observing the two 46-keV alpha particles arising from the ground-state decay. The 8B was produced using an in-flight radioactive beam technique. It was implanted in a silicon PIN-diode detector that was capable of identifying the alpha-particles from the 8Be ground state. From this measurement we find an upper limit (at 90% confidence level) of 7.3 x 10^{-5} for the branching ratio to the ground state. In addition to describing this measurement, we present a theoretical calculation for this branching ratio.
In the present work, we report our in depth study of 12C(p,pgamma)12C reaction both experimentally and theoretically with proton beam energy ranging from 8 MeV to 22 MeV. The angular distributions were measured at six different angles. We discuss the gamma angular distributions, total cross sections values for 4.438, 9.64, 12.7 and 15.1 MeV states. We also describe the theoretical interpretation of our measurements using optical model analysis. We also report the branching ratios from our measurements. For the first time, we have measured the the cross section and branching ratio for the 9.64 MeV state.
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