Final State Proton Research Articles

An analyser of deuteron tensor polarisation for the GeV/ c momentum range

For deuteron momenta 0.5 to at least 3 GeV/ c, the reaction dA → (pp) A′ on hydrogen and light nuclei is predicted to have useful analysing powers t 20 and t 22 when the final state protons are in the singlet state. A region of phase space covering small momentum transfers and low diproton masses may be selected where the reaction is experimentally distinctive and t 20 is large and insensitive to experimental cuts. Converter thickness may be used giving efficiencies for hydrogen of 1% at the lowest momentum down to 0.12% at the highest.

Quasi-free scattering of polarized protons

Cross section and analyzing power, energy-sharing spectra have been measured for the 16O( p , 2p) reaction at an incident energy of 200 MeV for twenty-four different pairs of angles of the detected final-state protons. This general survey is intended to test the validity of the distorted wave impulse approximation (DWIA), particularly with respect to the predicted j-dependent analyzing power caused by the distorting optical potentials and nuclear spin-orbit coupling. Although the data in general confirm this j-dependence, agreement in detail between DWIA calculations and the analyzing power data becomes worse as the momentum of the recoiling nucleus increases. Predictably, the cross-section calculations show more sensitivity to the optical-model parameters than do the analyzing powers. Within the present limits imposed by scanty elastic scattering data, there seems to remain a choice between predicted ( p , 2p) cross sections which either are unreasonably large or which have the incorrect energy-sharing shapes. More comprehensive elastic scattering and total reaction cross section data are clearly needed.

Diffractive dissociationn→pπ−π0induced by 12-GeV/cK−mesons

A sample of 198 events, corresponding to a cross section of 110 \ifmmode\pm\else\textpm\fi{} 15 \ensuremath{\mu}b, has been isolated of the baryon-diffractive-dissociation process $n\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ for three-body masses less than 2.5 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$. These dissociations are induced by 12-GeV/c ${K}^{\ensuremath{-}}$ mesons. To isolate this process from background, it is necessary to observe the final-state proton explicitly by its ionization in the bubble chamber. The three-body mass spectrum seems different from that of the $n{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ neutron diffractive breakup. A ${\ensuremath{\Delta}}^{0}$ signal is seen as well as possible ${N}_{1470}^{*}$, but no clear ${\ensuremath{\Delta}}^{+}$ is observed. The angular distribution of the proton in the $p{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ rest frame indicates that a multiperipheral mechanism is present.

Final state interactions in deuteron breakup by protons at 585 and 800 MeV

Neutron-proton final state interactions (FSI) were observed in the deuteron breakup reaction 2H(p, 2p)n-via a kinematically complete experiment at incident proton energies of 585 and 800 MeV. Kinematic conditions were chosen which allowed the final state proton and neutron to have small relative energies; data were taken at four proton c.m. scattering angles at 800 MeV, ranging from 71° to 119° and at 94° and 106° at 585 MeV. The data are analyzed in terms of the Goldberger-Watson formalism for final state interactions, and the individual contributions of the 1S 0 and 3S 1 np states are determined. The 3S 1 1S 0 ratio is large, as expected from some reaction models. The ratio of 3S 1 (almost elastic) to pd elastic cross sections is in good agreement with FSI analysis.

Polarization inp−pelastic scattering at large four-momentum transfers

New results are presented from the continuation of an experiment designed to study the polarization in elastic p-p scattering at large four- momentum transfers. A high intensity unpolarized proton beam of momentum 12.3 GeV/c was incident on a propanediol polarized porton target and both final-state protons were detected and momentum analyzed in multiwire proportional chamber spectrometers. The measurements spanned the t range 1.5 < absolute t < 6.2 (GeV/ c)$sup 2$. The results are discussed in the framework of optical, exchange, and parton models. (AIP)

Bremsstrahlung in the proton-proton interaction at 6.92 MeV

Measurements of p-p bremsstrahlung cross sections have been performed by detecting the two final-state protons in coincidence at 37°–37° and 38°–38° in the laboratory system, yielding respectively the following values corrected for noncoplanarity 1.2 ± 0.5 and 1.7 ± 0.7 μb sr −2 in fair agreement with theoretical values. This appears to resolve a discrepancy existing at low energies between theory and experiment, within the quoted errors.

A recurrence relation for the polarization in elastic p-p scattering in the framework of a parton model

Recent studies have shown that it is possible to account for the general features of large angle elastic proton-proton differential cross sections in a model where each constituent of one proton scatters from at least one constituent of the other proton in such a way that all constituents remain near their mass shell. Each of the parton-parton scatters is assumed to occur at approximately the same angle, so that the outgoing partons can easily recombine to form the two final state protons. In the present article we show that such a model, with additional assumptions regarding the scattering mechanisms at small | t|, leads to a non-trivial recurrence relation which is consistent with the structure recently reported in the high energy p-p polarization and fixed angle differential cross section.

On the average transverse momentum of particles produced in baryon-exchange reactions

The consequences of the assumption that the mean transverse momentum of pions produced in pp annihilations is an increasing function of total energy are examined within the framework of the uncorrelated jet model. Relationships between the mean-square transverse momentum and the mean number of produced pions are derived. A similar study is made of the reaction π+-p→ p + pions and π+-p→ p + anything, where the final state proton is moving rapidly forward in the lab.

The 40Ca(p,2p)39K Reaction at 45.0 MeV

A study of the 40Ca(p,2p)39K reaction has been made for two states of 39K, the 1d3/2−1(g.s.) and 2s1/2−1(2.53 MeV). Angular correlations at symmetric, coplanar angles between 30 and 105° have been measured. The data are compared with a distorted wave t-matrix calculation which utilizes a nonlocal bound state wave function. A further comparison is made with the angular correlation for unequal energies of the final state protons.

Proton-proton Bremsstrahlung at 99 MeV

The reaction p+p → p+p+γ at 99 MeV has been investigated. The two final-state protons were detected in coincidence at equal polar angles on opposite sides of the beam. Cross sections dσ/dΩ 1dΩ 2 of 3.77, 5.14, 9.01 and 18.8 μb sr 2 ±5 % were obtained at laboratory angles of 25°, 30°, 35° and 40° respectively. The angular distributions of the photons were inferred and were found to have shapes which are characteristic of quadrupole radiation.

Proton-Proton Bremsstrahlung atEp=10MeV

A measurement of the proton-proton bremsstrahlung cross section at ${E}_{p}=10$ MeV has been made. Two silicon surface-barrier detectors were placed in a hydrogen gas target at 30\ifmmode^\circ\else\textdegree\fi{} on opposite sides of the beam axis. The energies of the two final-state protons and their time-of-flight difference were measured. ${E}_{1}\ensuremath{-}{E}_{2}$ spectra corresponding to events in the true and accidental regions of the time spectrum were obtained in off-line analysis. An upper limit of 0.42 ${\mathrm{\ensuremath{\mu}}\mathrm{b}/\mathrm{s}\mathrm{r}}^{2}$ has been established for the proton-proton bremsstrahlung cross section at ${E}_{p}=10$ MeV, $\ensuremath{\theta}=30\ifmmode^\circ\else\textdegree\fi{}$.

Proton-Proton Bremsstrahlung at 61.7 MeV

The two final-state protons in the reaction $p+p\ensuremath{\rightarrow}p+p+\ensuremath{\gamma}$ at 61.7\ifmmode\pm\else\textpm\fi{}0.1 MeV were detected by ($\ensuremath{\Delta}E, E$) telescopes placed at 30\ifmmode^\circ\else\textdegree\fi{} on opposite sides of the beam. About 250 events were detected in a geometry with angular acceptance comparable to the maximum possible noncoplanarity. Additional data were obtained with apertures of smaller height, restricting the measurement to a more nearly coplanar geometry. The data indicate that the cross section is smaller for noncoplanar events. The estimated coplanar cross sections and differential cross section as a function of $\ensuremath{\gamma}$-ray angle are presented. The results agree with recent theoretical predictions.

Polarization Parameter inp−pScattering from 1.7 to 6.1 BeV

The polarization parameter in proton-proton scattering has been measured at incident proton kinetic energies of 1.7, 2.85, 3.5, 4.0, 5.05, and 6.15 BeV and for four-momentum transfer squared between 0.1 and 1.0 ${(\mathrm{B}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. The experiment was done with an unpolarized proton beam from the Bevatron striking a polarized proton target. Both final-state protons were detected in coincidence and the asymmetry in counting rate for target protons polarized parallel and antiparallel to the scattering normal was measured. The maximum polarization was observed to decrease from 0.4 at 1.7 BeV to 0.2 at 6.1 BeV. The maximum of the polarization at all energies studied occurs at a four-momentum transfer squared of 0.3 to 0.4 ${(\mathrm{B}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$.