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Register a new userExperimental search for the bound state singlet deuteron in the radiative n-p capture
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We performed an experimental search for the bound state singlet deuteron predicted in some microscopic calculations. The predicted energy of this metastable level is in vicinity of the deuteron disintegration threshold. This state should manifest itself in two-photon transition following thermal neutron capture by protons. The experiment consists in the search for the second gamma-ray in the cascade through a high statistics measurement of $gamma$-ray spectra after cold neutron capture by hydrogen nuclei. The upper limit $2mu$b (2$sigma$ level) is obtained for the cross section of the singlet deuteron production with the bound energy in the range 10-125 keV.
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A search for the muon catalyzed fusion reaction dd --> ^4He +gamma in the ddmu muonic molecule was performed using the experimental mu CF installation TRITON and NaI(Tl) detectors for gamma-quanta. The high pressure target filled with deuterium at temperatures from 85 K to 800 K was exposed to the negative muon beam of the JINR phasotron to detect gamma-quanta with energy 23.8 MeV. The first experimental estimation for the yield of the radiative deuteron capture from the ddmu state J=1 was obtained at the level n_{gamma}leq 2times 10^{-5} per one fusion.
The 12C+16O resonant radiative capture reaction has been studied at 5 bombarding energies between Elab = 15.4 and 21.4 MeV, around the Coulomb barrier, at the Triumf laboratory (Vancouver, Canada) using the Dragon 0{deg} spectrometer and the associated BGO array. The most remarquable result is the previously unobserved decay path through 28Si doorway states of energies around 12 MeV leading to the measurement of new capture cross-sections. The feeding of specific, deformed states in 28Si from the resonances is discussed, as well as the selective feeding of 1^+ T=1 states around 11 MeV.
The astrophysical $S$-factor for the radiative capture $d(p,gamma)^3$He in the energy-range of interest for Big Bang Nucleosynthesis (BBN) is calculated using an {it ab-initio} approach. The nuclear Hamiltonian retains both two- and three-nucleon interactions - the Argonne $v_{18}$ and the Urbana IX, respectively. Both one- and many-body contributions to the nuclear current operator are included. The former retain for the first time, besides the $1/m$ leading order contribution ($m$ is the nucleon mass), also the next-to-leading order term, proportional to $1/m^3$. The many-body currents are constructed in order to satisfy the current conservation relation with the adopted Hamiltonian model. The hyperspherical harmonics technique is applied to solve the $A=3$ bound and scattering states. A particular attention is used in this second case in order to obtain, in the energy range of BBN, an uncertainty on the astrophysical $S$-factor of the order or below $sim$1 %. Then, in this energy range, the $S$-factor is found to be $sim$10 % larger than the currently adopted values.Part of this increase (1-3 %) is due to the $1/m^3$ one-body operator, while the remaining is due to the new more accurate scattering wave functions. We have studied the implication of this new determination for the $d(p,gamma)^3$He $S$-factor on deuterium primordial abundance. We find that the predicted theoretical value for $^2$H/H is in excellent agreement with its experimental determination, using the most recent determination of baryon density of Planck experiment, and with a standard number of relativistic degrees of freedom $N_{rm eff}=3.046$ during primordial nucleosynthesis.
Employing the Bonn-Gatchina partial wave analysis framework (PWA), we have analyzed HADES data of the reaction $p(3.5GeV)+pto pK^{+}Lambda$. This reaction might contain information about the kaonic cluster $ppK^-$ via its decay into $pLambda$. Due to interference effects in our coherent description of the data, a hypothetical $overline{K}NN$ (or, specifically $ppK^-$) cluster signal must not necessarily show up as a pronounced feature (e.g. a peak) in an invariant mass spectra like $pLambda$. Our PWA analysis includes a variety of resonant and non-resonant intermediate states and delivers a good description of our data (various angular distributions and two-hadron invariant mass spectra) without a contribution of a $overline{K}NN$ cluster. At a confidence level of CL$_{s}$=95% such a cluster can not contribute more than 2-12% to the total cross section with a $pK^{+}Lambda$ final state, which translates into a production cross-section between 0.7 $mu b$ and 4.2 $mu b$, respectively. The range of the upper limit depends on the assumed cluster mass, width and production process.
By measuring the lifetime of the negative muon in pure protium (hydrogen-1), the MuCap experiment determines the rate of muon capture on the proton, from which the protons pseudoscalar coupling g_p may be inferred. A precision of 15% for g_p has been published; this is a step along the way to a goal of 7%. This coupling can be calculated precisely from heavy baryon chiral perturbation theory and therefore permits a test of QCDs chiral symmetry. Meanwhile, the MuSun experiment is in its final design stage; it will measure the rate of muon capture on the deuteron using a similar technique. This process can be related through pionless effective field theory and chiral perturbation theory to other two-nucleon reactions of astrophysical interest, including proton-proton fusion and deuteron breakup.
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