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تسجيل مستخدم جديدCorrelated $Lambda t$ pairs from the absorption of $K^-$ at rest in light nuclei
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Novel data from the $K^{-}_{stop}A$ absorption reaction in light nuclei $^{6,7}$Li and $^{9}$Be are presented. The study aimed at finding $Lambda t$ correlations. Regardless of $A$, the $Lambda t$ pairs are preferentially emitted in opposite directions. Reaction modeling predominantly assigns to the $K^-_{stop}AtoLambda t(N)A$ direct reactions the emission of the $Lambda t$ pairs whose yield is found to range from $10^{-3}$ to $10^{-4}$$/K^-_{stop}$. The experiment was performed with the FINUDA spectrometer at DA$Phi$NE (LNF).
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We investigate double $Lambda$ hyperfragment formation from the statistical decay of double $Lambda$ compound nuclei produced in the $Xi^-$ absorption at rest in light nuclei, $^{12}mathrm{C}$, $^{14}mathrm{N}$ and $^{16}mathrm{O}$. We examine the ta
rget and the $LambdaLambda$ bond energy dependence of the double $Lambda$ hyperfragment formation probabilities, especially of those double hypernuclei observed in experiments. For the $^{12}mathrm{C}$ ($^{14}mathrm{N}$) target, the formation probabilities of $^{6}_{LambdaLambda}mathrm{He}$ and $^{10}_{LambdaLambda}mathrm{Be}$ ($^{13}_{LambdaLambda}mathrm{B}$) are found to be reasonably large as they are observed in the KEK-E373 (KEK-E176) experiment. By comparison, for $^{16}mathrm{O}$ target, the formation probability of $^{11}_{LambdaLambda}mathrm{Be}$ is calculated to be small with $Delta B_{LambdaLambda}$ consistent with the Nagara event. We also evaluate the formation probability of ${}^{5}_{LambdaLambda}mathrm{H}$ from a $Xi^-$-${}^{6}mathrm{He}$ bound state, ${}^{7}_{Xi}mathrm{H}$.
$p,Lambda$ emission in coincidence following $K^-$ absorption at rest in nuclei is studied using quantum mechanical scattering theory and nuclear wave functions. $K^-$ absorption is assumed to occur on two protons in the nucleus. In the formalism, em
phasis is put on the study of the final state interaction (FSI) effects of $p$ and $Lambda$ with the recoiling nucleus. We include elastic scattering and single nucleon knock-out (KO) channels in the FSI. Calculations are presented for the $^{12}$C nucleus, using shell model wave functions, and without any extra mass modification of the $K^-,pp$ system in the nucleus. Calculated results are presented for the angular correlation distribution between $p$ and $Lambda$, their invariant mass distribution and the momentum spectra of $p$ and $Lambda$. These results are compared with the corresponding experimental measurements cite{agnello}. With only elastic scattering FSI included, the angular correlation distribution and the momentum spectra are found to be in good accord with the corresponding measurements. With full FSI the calculated $p,Lambda$ invariant mass distribution is found to have two peaks, one corresponding to the elastic scattering FSI and another to single nucleon KO FSI. The KO peak agrees fully, in position and shape, with the peak observed in Ref. cite{agnello}. The peak corresponding to elastic scattering FSI does not seem to exist in the measured distribution. Considering that such a two peak structure is always seen in the inclusive ($p$, $p^prime $) and ($e$, $e^prime $) reactions in nuclei at intermediate energies, absence of the elastic scattering peak in the $p,Lambda$ reaction is intriguing.
Correlated $Lambda d$ pairs emitted after the absorption of negative kaons at rest $K^{-}_{stop}Ato Lambda d A$ in light nuclei $^6Li$ and $^{12}C$ are studied. $Lambda$-hyperons and deuterons are found to be preferentially emitted in opposite direct
ions. The $Lambda d$ invariant mass spectrum of $^6Li$ shows a bump whose mass is 3251$pm$6 MeV/c$^2$. The bump mass (binding energy), width and yield are reported. The appearance of a bump is discussed in the realm of the [$bar{K}3N$] clustering process in nuclei. The experiment was performed with the FINUDA spectrometer at DA$Phi$NE (LNF).
Correlations of back-to-back coincident $Lambda d$ and $Lambda t$ pairs from the stopped $K^-$ reaction on $^4$He had been investigated, thereby $Lambda d$ and $Lambda t$ branches of non-mesonic three- and four-nucleon absorption processes of antikao
n at rest were identified as well-separable processes, respectively. The branching ratio of the three-nucleon process, ($^4$He-$K^-$)$_{atomic} rightarrow Lambda d n$, is estimated to be $(0.9 pm 0.1 (stat) pm 0.2 (syst)) times 10^{-3}$ from the normalized $Lambda d$ spectrum in a $Lambda d n$ final state, while the fraction of the four-nucleon process, ($^4$He-$K^-$)$_{atomic} rightarrow Lambda t$, is obtained to be $(3.1 pm 0.4 (stat) pm 0.5 (syst)) times 10^{-4}$ per stopped $K^-$.
Background: The high momentum distribution of atoms in two spin-state ultra-cold atomic gases with strong short-range interactions between atoms with different spins, which can be described using Tans contact, are dominated by short range pairs of di
fferent fermions and decreases as $k^{-4}$. In atomic nuclei the momentum distribution of nucleons above the Fermi momentum ($k>k_F approx 250$ Mev/c) is also dominated by short rangecorrelated different-fermion (neutron-proton) pairs. Purpose: Compare high-momentum unlike-fermion momentum distributions in atomic and nuclear systems. Methods: We show that, for $k>k_F$ MeV/c, nuclear momentum distributions are proportional to that of the deuteron. We then examine the deuteron momentum distributions derived from a wide variety of modern nucleon-nucleon potentials that are consistent with $NN$-scattering data. Results: The high momentum tail of the deuteron momentum distribution, and hence of the nuclear momentum distributions appears to decrease as $k^{-4}$. This behavior is shown to arise from the effects of the tensor part of the nucleon-nucleon potential. In addition, when the dimensionless interaction strength for the atomic system is chosen to be similar to that of atomic nuclei, the probability for finding a short range different-fermion pair in both systems is the same. Conclusions: Although nuclei do not satisfy all of the conditions for Tans contact, the observed similarity of the magnitude and $k^{-4}$ shape of nuclear and atomic momentum distributions is remarkable because these systems differ by about $20$ orders of magnitude in density. This similarity may lead to a greater understanding of nuclei and the density dependence of nuclear systems.
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