Backward Proton Production Research Articles

Experimental and theoretical results for weak charge current backward proton production

In this paper, we study deuteron breakup by high energy neutrinos. We present previously unpublished data on neutrino induced backward protons from deuteron targets; we calculate the contributions from both the two-nucleon $(2N)$ and six-quark $(6q)$ deuteron components, which depend upon the overall normalization of the part that is $6q;$ and, we suggest other signatures for distinguishing the $2N$ and $6q$ clusters. We conclude that the $6q$ cluster naturally contributes to the high momentum backward proton spectrum just in the region where the standard $2N$ models lie below the data, and the absolute size of the far backward data is nicely explained if the amount of $6q$ is one or a few percent by normalization of the deuteron.

Internal nuclear momentum and subthreshold kaon production

The role of the high momentum component of the nuclear spectral function in subthreshold K + meson production in proton-nucleus collisions is studied. We use the parametrization of the elementary NN → NYK cross section, which is based on the calculations performed with the boson exchange model. The experimental data on quasi-elastic electron and gamma scattering and backward proton production are analyzed in order to extract the high momentum component in nuclei. It is shown that the contribution from the high momentum component to the kaon production is negligible.

Backward proton production in ?+ andK + collisions with Al and Au nuclei at 250 GeV/c

Backward proton production is studied in interactions of π+ andK + mesons withAl andAu nuclei at 250 GeV/c. The proton momentum spectra are measured at different emission angles. From the two-proton correlations, it is found, that a significant part ((26±4)% forAl and (44±6)% forAu) of the backward proton production can be attributed to secondary pion absorption by a nucleon pair in the nuclear medium,\(\pi ^ + (pn) \to \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\leftarrow}$}}{p} p\) and\(\pi ^0 (pp) \to \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\leftarrow}$}}{p} p\). It is found that the share of the secondary pion absorption can be fitted by a power dependence αA β, with β=0.27±0.05. An upper limit of the cross section for the colour-charge-exchange mechanism of backward proton production is estimated.

Cross sections of backward proton production in [formula omitted] interactions

The inclusive cross sections of backward proton production in π −( K −, p ) -Be, Al, Cu, Pb interactions at 40 GeV/ c are presented. Protons have been detected in the angular range 150°–165° and kinetic energy region 0.1–0.3 GeV. The invariant cross-section ratios for various beam particles are independent of the values of kinetic energy and of the nuclear target type: 〈ƒ K −/ƒ π −〉= 0.87 ± 0.03 stat ± 0.03 syst , 〈ƒ p /ƒ π −〉 = 1.82 ± 0.10 stat ± 0.05 syst . The A-dependence of the cross-section slope parameter for A⩾27 is less than ∼2%.

Multiparticle interactions in backward proton production, subthreshold antiproton production, and inclusive electron scattering from nuclei.

The phenomena of backward proton emission and subthreshold antiproton production in the proton-nucleus interactions, and findings from the inclusive scattering of electrons from nuclei, are interpreted in terms of multiparticle interactions. Rates for multiparticle collisions are calculated using the results from many-body theory, with the products of the squared interaction amplitudes and Wigner functions. The rates for the processes with different number of particles are proportional to the different powers of spatial density. The many-body amplitudes are expanded in terms of propagators and elementary amplitudes with only two particles in the initial state. The leading processes are isolated on a tree level. They correspond to the expansion of a ground-state nuclear wave function. Reasonable agreement with data is obtained.

Internal nuclear momentum and subthreshold anti-proton production in p-nucleus and nucleus-nucleus collisions

We investigate subthreshold anti-proton production in p-nucleus and nucleus-nucleus collisions in terms of the internal nuclear momentum of the nucleons in the colliding nuclei. We employ a first collision model which contains the kinematics of individual NN collisions, with the inclusion of internal nuclear momentum distributions extracted from data on quasi-elastic electron scattering and backward proton production. Calculations for subthreshold particle production in p-nucleus collisions show excellent agreement with experimental data on subthreshold anti-proton and K + production in p + Cu collisions. An extension of the model to nucleus-nucleus collisions includes also the internal momentum for the incoming projectile nucleons, and contains the parameters obtained from a best fit to the p + Cu → p + X data. Despite the excellent agreement with the p + Cu → p + X data, this model underestimates recent experimental data on subthreshold p production in nucleus-nucleus collisions by large factors. Implications for collective phenomena at large nuclear densities and temperatures are discussed.

Problem of backward proton production.

The problem of backward proton production in proton-nucleus collisions at intermediate energies is discussed. We develop a model which is based on the correlated two-nucleon-cluster picture. Feynman diagrams including intermediate \ensuremath{\Delta}-resonance states are evaluated. The model is applied first to the deuteron target (p+d\ensuremath{\rightarrow}p+X) at intermediate energies. This presents a good test for the elementary process in our model. Our calculation reproduces well the observed energy spectra of backward protons. Then the model is applied to heavier nuclear targets. There we employ the Fermi momentum distribution which is deduced from other sources of information. This contains high momentum components that play a crucial role in reproducing the high energy part of the backward proton spectra. The model describes remarkably well a wide range of the single particle energy spectra as well as the angular distributions of the backscattered proton. As a further test of the model, we calculate the coincidence spectra of the backward- and the forward-going protons at 800 MeV. The calculation reproduces well the shape (particularly two mountains in the contour plot) of the coincidence experiment which has recently been done by Miake et al. The present analysis strongly supports the existence of the high momentum components in the nuclear Fermi motion. This seems to be rather universal from light to heavy nuclei, and may reflect a new length scale inside the nucleus.

New direct way of checking the nuclear core hypothesis in inclusive hadron scattering off the polarized deuteron

We demonstrate that S, D deuteron wave functions and therefore the nuclear core hypothesis can be investigated directly by studying the backward proton production in the hadronic reaction h+D→p+X with a polarized deuteron.

Backward proton production and high-momentum components of nuclei

The production of energetic protons at 180/sup 0/ by the inclusive reaction A (p,p') X is studied. A mechanism which involves A - 1 nucleon transfer and relates the inclusive cross section to the total cross section sigma/sub T/(p,A - 1) and realistic nuclear single-particle momentum distributions gives a qualitative understanding of the data.