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Register a new userDirect experimental evidence of the weak $Lambda n p rightarrow n n p$ hypernucleus decay
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A direct experimental evidence of the occurrence of the weak reaction $Lambda nprightarrow nnp$ in nuclei has been obtained by the FINUDA experiment. Three events have been found that can be attributed to $^{7}_{Lambda}$Li and $^{9}_{Lambda}$Be two nucleon-induced non mesonic weak decays. The kinematic analysis of such events is presented here.
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This paper presents results from partial-wave analyses of the photoproduction reactions $gamma p rightarrow eta p$ and $gamma n rightarrow eta n$. World data for the observables DSG, $Sigma$, $T$, $P$, $F$, and $E$ were analyzed as part of this work. The dominant amplitude in the fitting range from threshold to a c.m. energy of 1900 MeV was found to be $S_{11}$ in both reactions, consistent with results of other groups. At c.m. energies above 1600 MeV, our solution deviates from published results, with this work finding higher-order partial waves becoming significant. Data off the proton suggest that the higher-order terms contributing to the reaction include $P_{11}$, $P_{13}$, and $F_{15}$. The final results also hint that $F_{17}$ is needed to fit double-polarization observables above 1900 MeV. Data off the neutron show a contribution from $P_{13}$, as well as strong contributions from $D_{13}$ and $D_{15}$.
Let $p(n)$ denote the partition function. Desalvo and Pak proved the log-concavity of $p(n)$ for $n>25$ and the inequality $frac{p(n-1)}{p(n)}left(1+frac{1}{n}right)>frac{p(n)}{p(n+1)}$ for $n>1$. Let $r(n)=sqrt[n]{p(n)/n}$ and $Delta$ be the difference operator respect to $n$. Desalvo and Pak pointed out that their approach to proving the log-concavity of $p(n)$ may be employed to prove a conjecture of Sun on the log-convexity of ${r(n)}_{ngeq 61}$, as long as one finds an appropriate estimate of $Delta^2 log r(n-1)$. In this paper, we obtain a lower bound for $Delta^2log r(n-1)$, leading to a proof of this conjecture. From the log-convexity of ${r(n)}_{ngeq61}$ and ${sqrt[n]{n}}_{ngeq4}$, we are led to a proof of another conjecture of Sun on the log-convexity of ${sqrt[n]{p(n)}}_{ngeq27}$. Furthermore, we show that $limlimits_{n rightarrow +infty}n^{frac{5}{2}}Delta^2logsqrt[n]{p(n)}=3pi/sqrt{24}$. Finally, by finding an upper bound of $Delta^2 logsqrt[n-1]{p(n-1)}$, we prove an inequality on the ratio $frac{sqrt[n-1]{p(n-1)}}{sqrt[n]{p(n)}}$ analogous to the above inequality on the ratio $frac{p(n-1)}{p(n)}$.
We studied the $^{12}$C(p,2p+n) reaction at beam momenta of 5.9, 8.0 and 9.0 GeV/c. For quasielastic (p,2p) events we reconstructed {bf p_f} the momentum of the knocked-out proton before the reaction; {bf p_f} was then compared (event-by-event) with {bf p_n}, the measured, coincident neutron momentum. For $|p_n|$ > k$_F$ = 0.220 GeV/c (the Fermi momentum) a strong back-to-back directional correlation between {bf p_f} and {bf p_n} was observed, indicative of short-range n-p correlations. From {bf p_n} and {bf p_f} we constructed the distributions of c.m. and relative motion in the longitudinal direction for correlated pairs. After correcting for detection efficiency, flux attenuation and solid angle, we determined that 49 $pm$ 13 % of events with $|p_f|$ > k_F had directionally correlated neutrons with $|p_n|$ > k$_F$. Thus short-range 2N correlations are a major source of high-momentum nucleons in nuclei.
Recently, a new technique for measuring short-range NN correlations in nuclei (NN SRCs) was reported by the E850 collaboration, using data from the EVA spectrometer at the AGS at Brookhaven Nat. Lab. In this talk, we will report on a larger set of data from new measurement by the collaboration, utilizing the same technique. This technique is based on a very simple kinematic approach. For quasi-elastic knockout of protons from a nucleus ($^{12}$C(p,2p) was used for the current work), we can reconstruct the momentum {bf p$_f$} of the struck proton in the nucleus before the reaction, from the three momenta of the two detected protons, {bf p$_1$} and {bf p$_2$} and the three momentum of the incident proton, {bf p$_0$} : {bf p$_f$} = {bf p$_1$} + {bf p$_2$} - {bf p$_0$} If there are significant n-p SRCs, then we would expect to find a neutron with momentum -{bf p$_f$} in coincidence with the two protons, provided {bf p$_f$} is larger than the Fermi momentum $k_F$ for the nucleus (${sim}$220 MeV/c for $^{12}$C). Our results reported here confirm the earlier results from the E850 collaboration.
Due to the high sensitivity of the N N --> N N gamma reaction to the nucleon-nucleon potential, Bremsstrahlung radiation is used as a tool to investigate details of the nucleon-nucleon interaction. Such investigations can be performed at the cooler synchrotron COSY in the Research Centre Juelich, by dint of the COSY-11 detection system. The results of the identification of Bremsstrahlung radiation emitted via the d p --> d p gamma reaction in data taken with a proton target and a deuteron beam are presented and discussed.
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