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Register a new userPolarizing mechanisms for stored $p$ and $bar p$ beams interacting with a polarized target
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Kinetics of the polarization buildup at the interaction of stored protons (antiprotons) with a polarized target is considered. It is demonstrated that for small scattering angles, when a projectile remains in the beam, the polarization buildup is completely due to the spin-flip transitions. The corresponding cross sections turn out to be negligibly small for a hydrogen gas target as well as for a pure electron target. For the latter, the filtering mechanism also does not provide a noticeable beam polarization.
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Nucleon pole contributions in $J/psi to N bar N pi$, $p bar p eta$, $p bar p eta^{prime}$ and $p bar{p} omega$ decays are re-studied. Different contributions due to PS-PS and PS-PV couplings in the $pi$-N interaction and the effects of $NNpi$ form factors are investigated in the $J/psi to N bar N pi$ decay channel. It is found that when the ratio of $|F_0| /|F_M|$ takes small value, without considering the $NNpi$ form factor, the difference between PS-PS and PS-PV couplings are negligible. However, when the $NNpi$ form factor is included, this difference is greatly enlarged. The resultant decay widths are sensitive to the form factors. As a conclusion, the nucleon-pole contribution as a background is important in the $J/psito Nbar{N}pi$ decay and must be accounted. In the $J/psito Nbar{N}eta$ and $Nbar{N}eta$ decays, its contribution is less than 0.1% of the data. In the $J/psito Nbar{N}omega$ decay, it provides rather important contribution without considering form factors. But the contribution is suppressed greatly when adding the off-shell form factors. Comparing these results with data would help us to select a proper form factor for such kind of decay.
We consider $Lambda$ and $bar{Lambda}$ production in a wide range of proton scattering experiments. The produced $Lambda$ and $bar{Lambda}$ may or may not contain a diquark remnant of the beam proton. The ratio of these two production mechanisms is found to be a simple universal function $r = [ kappa/(y_p - y) ]^i$ of the rapidity difference $y_p - y$ of the beam proton and the produced $Lambda$ or $bar{Lambda}$, valid over four orders of magnitude, from $r approx 0.01$ to $r approx 100$, with $kappa = 2.86 pm 0.03 pm 0.07$, and $i = 4.39 pm 0.06 pm 0.15$.
Provided the enhancement in the $p bar{p}$ spectrum in radiative decay $J/psi to gamma p bar{p}$ observed by the BES collaboration is due to an existence of a $p bar{p}$ molecular state, we calculate its binding energy and lifetime in the linear $sigma$ model. We consider a possibility that the enhancement is due to a $p bar p$ resonance which is in either S-wave or P-wave structure and compare our results with the data.
This submission was withdrawn because of an unresolved dispute between the authors [arXiv admin 2009-4-13].
The first observation of the decay $eta_{c}(2S) to p bar p$ is reported using proton-proton collision data corresponding to an integrated luminosity of $3.0rm , fb^{-1}$ recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The $eta_{c}(2S)$ resonance is produced in the decay $B^{+} to [cbar c] K^{+}$. The product of branching fractions normalised to that for the $J/psi$ intermediate state, ${cal R}_{eta_{c}(2S)}$, is measured to be begin{align*} {cal R}_{eta_{c}(2S)}equivfrac{{mathcal B}(B^{+} to eta_{c}(2S) K^{+}) times {mathcal B}(eta_{c}(2S) to p bar p)}{{mathcal B}(B^{+} to J/psi K^{+}) times {mathcal B}(J/psito p bar p)} =~& (1.58 pm 0.33 pm 0.09)times 10^{-2}, end{align*} where the first uncertainty is statistical and the second systematic. No signals for the decays $B^{+} to X(3872) (to p bar p) K^{+}$ and $B^{+} to psi(3770) (to p bar p) K^{+}$ are seen, and the 95% confidence level upper limits on their relative branching ratios are % found to be ${cal R}_{X(3872)}<0.25times10^{-2}$ and ${cal R}_{psi(3770))}<0.10$. In addition, the mass differences between the $eta_{c}(1S)$ and the $J/psi$ states, between the $eta_{c}(2S)$ and the $psi(2S)$ states, and the natural width of the $eta_{c}(1S)$ are measured as begin{align*} M_{J/psi} - M_{eta_{c}(1S)} =~& 110.2 pm 0.5 pm 0.9 rm , MeV, M_{psi(2S)} -M_{eta_{c}(2S)} =~ & 52.5 pm 1.7 pm 0.6 rm , MeV, Gamma_{eta_{c}(1S)} =~& 34.0 pm 1.9 pm 1.3 rm , MeV. end{align*}
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