Phase Shift Solutions Research Articles

Determination of proton-nucleon analyzing powers and spin-rotation-depolarization parameters at 500 MeV.

500 MeV p\ensuremath{\rightarrow}+p elastic and quasielastic, and p\ensuremath{\rightarrow}+n quasielastic, analyzing powers (${A}_{y}$) and spin-rotation-depolarization parameters (${D}_{\mathrm{SS}}$, ${D}_{\mathrm{SL}}$, ${D}_{\mathrm{LS}}$, ${D}_{\mathrm{LL}}$, ${D}_{\mathrm{NN}}$) were determined for center-of-momentum angular ranges 6.8\ifmmode^\circ\else\textdegree\fi{}--55.4\ifmmode^\circ\else\textdegree\fi{} (elastic) and 22.4\ifmmode^\circ\else\textdegree\fi{}--55.4\ifmmode^\circ\else\textdegree\fi{} (quasielastic); liquid hydrogen and deuterium targets were used. The p\ensuremath{\rightarrow}+p elastic and quasielastic results are in good agreement; both the p\ensuremath{\rightarrow}+p and p\ensuremath{\rightarrow}+n parameters are well described by current phase shift solutions.

Isobar-width effects in the coupling of nucleon to isobar channels.

The investigation of the effects of isobar coupling to two-nucleon channels has been extended to include additional physical features. A new code discretizes the mass distribution of the isobar widths and treats each mass as a separate channel. This allows the treatment of width in the presence of coupling by transition potentials, in addition to the previously permitted boundary coupling. It also produces the S-italic-matrix components required to describe the many-body final-state distributions. When indicated by the one-pion-exchange coupling strength new isobar channels are included. The new results for nucleon-nucleon scattering fit the data better, starting from more realistic models. The observed /sup 1/D/sub 2/ and /sup 3/F/sub 3/ structures are well understood as coupled-channel effects, without exotic-quark contributions. The existence of a structure in the /sup 3/P/sub 0/ channel depends on the amount of inelasticity, which differs among the phase shift solutions. The energy dependence seen in recent analyses, of the /sup 3/P/sub 2/ phase shift near T-italic/sub L-italic/ = 800 MeV, is shown to be a consequence of the isobar channel coupling. Improved models obtained for the /sup 1/S/sub 0/ and /sup 3/S/sub 1/-/sup 3/D/sub 1/ channels are being developed. They are important to accurately extrapolate those phasesmore » to higher energies where six-quark effects are expected.« less

Proton-nucleon spin-rotation and -depolarization parameters at 800 MeV.

Using a liquid deuterium target, 800 MeV quasielastic parrow+p and parrow+n spin-rotation and -depolarization parameters (D/sub S/S,D/sub S/L,D/sub L/S,D/sub L/L,D/sub N/N ) were determined over the center-of-momentum angular range 14.3/sup 0/--69.2/sup 0/. The parrow+p results are in good agreement with existing elastic results and predictions from phase shift analysis. The parrow+n results, in general, are not in agreement with predictions from phase shift solutions. Small corrections to previously reported parrow+p elastic observables are also discussed.

Measurements of the spin-spin correlation parameterCSS=(S,S;0,0)at 487, 639, and 791 MeV

The spin-spin correlation parameter ${C}_{\mathrm{SS}}=(S,S;0,0)$ has been measured for $p\ensuremath{-}p$ elastic scattering over a large angular range. The data are particularly useful in checking currently available phase-shift solutions.

Measurement of Spin Parameters for a Decisive Clarification of the Structure Observed in thep−pSystem

Recent data are presented on spin-spin correlation parameters CLL=(L,L;0,0) and CSL=(S,L;0,0) at forward angles from 1.18 to 2.47 GeV/c incident momenta in proton-proton elastic scattering. Values for ΔσL (inelastic) are derived and are shown to disagree with predictions of theoretical models attempting to describe p−p scattering without dibaryon resonances. Finally, the CLL and CSL data discriminate among various phase-shift solutions, and will lead to a clarification of the p−p phase shifts.

Prediction of n- 4He phase shifts from p- 4He data between 20 and 55 MeV

Effective two-body Coulomb corrections are applied to R-matrix n- 4He phase shifts below 20 MeV lab energy leading to charge symmetric phase shifts that are qualitatively consistent with R-matrix p- 4He phases. The inverse procedure is pursued for energies above 20 MeV yielding charge symmetric n- 4He phases from two different sets of p- 4He phase shift solutions. The Coulomb corrections to both sets of proton data are roughly the same, whereas the predicted n- 4He values differ as much as the input proton data do. For energies between 20 and 30 MeV the predictions are compared with the best available neutron data. In some partial waves the measured phase shifts and the predictions are about compatible. The Coulomb corrections above 30 MeV can be utilized for analysing upcoming n- 4He data on the basis of better known p- 4He data.

Spin transfer measurements forpp→ppat 647 MeV

Measurements have been made of the spin depolarization parameters D/sub N/N, D/sub S/S, D/sub L/S (27/sup 0/ ..pp at 647 MeV. Typical uncertainties are about 0.03 compared with about 0.1 for previous data. Previous data are reviewed. The present data are in agreement with corrected previous data, and are in agreement with Arndt's phase-shift solutions.

Amplitude Analysis of the Reactionπ+π−→π0π0from 1.0 to 2.3 GeV

An amplitude analysis of ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ scattering, from the reaction ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\Delta}}^{++}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$, has been carried out between 1.0 and 2.3 GeV. The data are consistent with only one of the four $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ phase-shift solutions determined from ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ data. A new ${J}^{\mathrm{PC}}={2}^{++}$ state at 1800 MeV with a width of 280 MeV is observed.

First Measurement of the Spin Rotation ParameterQforp-Ca40Elastic Scattering at 500 MeV

The spin rotation parameter $Q$ has been measured for $p$-$^{40}\mathrm{Ca}$ elastic scattering at 497 MeV for $0.01<~\ensuremath{-}t<~0.15$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ with use of the new high-resolution spectrometer focalplane polarimeter. In conjunction with analyzing power and differential cross section, this measurement uniquely determines the elastic scattering amplitudes up to an arbitrary phase. A parameter-free analysis within the Glauber diffractive approximation with use of $N\ensuremath{-}N$ phase-shift solutions is presented.

How to improve np phase-shifts at 25 and 50 MeV

Measurements of the spin-correlation parameter ALL at backward angles with errors of +or-0.02 eliminate the strong correlation between epsilon 1 (the parameter which mixes 3S1 and 3D1 states) and the 1P1 phase-shift, and stabilise the phase-shift solutions at 25 and 50 MeV.

Neutron-proton elastic scattering between 200 and 500 MeV. III. Phase shift analysis

Data on ${D}_{t}$, ${R}_{t}$, ${A}_{t}$, and $P$ lead to unique and accurate $\mathrm{np}$ phase shift solutions at 210, 325, 425, and 515 MeV. The $I=O, D, \mathrm{and} G$ waves show large systematic deviations from current theoretical models.NUCLEAR REACTIONS $p(n,n)p$, $E=210, 325, 425, \mathrm{and} 515$ MeV; phase shift analysis.

Proton-nucleus total cross sections in the intermediate energy range

Proton-nucleus total and reaction cross sections are computed for a number of target nuclei at energies ranging from 100 to 2200 MeV using the Kerman, McManus, and Thaler optical potential formalism and the impulse approximation. Corrections due to Pauli, short-range dynamical, and center-of-mass correlations are included in the calculations. In addition, the electric form factor of the neutron and the nucleon magnetic moments are included in deriving the necessary proton densities from available empirical charge distributions. The proton-nucleon scattering amplitudes are obtained from phase shift solutions or directly from the published $N\ensuremath{-}N$ data. The proton and neutron point densities are deduced where possible from analyses of electron and proton scattering or from Hartree-Fock predictions if the appropriate elastic angular distribution data are unavailable. An estimate of the uncertainty in the calculated total cross sections is given. The total and reaction cross sections computed in this way are shown to be in very good agreement with the data above 400 MeV but overestimate the data by 15-25% at lower energies, indicating that the approximate multiple scattering calculations generally performed near 1 GeV are inadequate when applied at energies below 400 MeV. Several theoretical improvements are suggested for this lower energy range and some numerical estimates are given. Analysis of total cross section data is also shown to be an unsuitable method for obtaining accurate measurements of neutron matter densities.NUCLEAR REACTIONS proton-nucleus scattering; total and reaction cross sections; ${E}_{p}=100 \mathrm{to} 2200$ MeV; targets $^{12}\mathrm{C}$, $^{16}\mathrm{O}$, $^{27}\mathrm{A}1$, $^{56}\mathrm{Fe}$, $^{63,65}\mathrm{Cu}$, $^{72,74}\mathrm{Ge}$, $^{127}\mathrm{I}$, and $^{208}\mathrm{Pb}$; Kerman, McManus, and Thaler optical potential; target nucleon correlations.

Cluster-Model Study of the T=1 States in A=4 System: 3He+p Scattering

We investigate the properties of 4Li within the framework of a [3He+p]-cluster model, using the generator coordinate method (GCM). Roles of spin-orbit and tensor forces are clarified through the angular momentum dependence of the GCM kernels which is characteristic of these non-central forces. The 3He+p scattering problem is solved by the variational method. Results are compared with available phase-shift analyses and it is found that our calculation agrees with a group of phase-shift solutions which includes Tombrello's solution. This fact indicates the ordering of T=1 negative parity states in the A=4 system to be 2-, 1- (triplet-main), 0- and 1- (singlet-main). The cluster model successfully reproduces the available experimental data including various kinds of polarization measurements. Comparison is made with the 1p-1h harmonic-oscillator shell model. Our results suggest that it is very promising to survey the A=4 system with a [A=3 nucleus+one nucleon]-cluster model.

Differential and channel cross sections for the reactions K L0p → K S0p and K L0p → Λ0π+ in the c.m. energy range 1605 to 1910 MeV

The differential and channel cross sections have been measured for the reactions K L 0p → K S 0p and K L 0p → Λ 0 π + in nine energy intervals in the c.m. range 1605 to 1910 MeV. The regeneration reaction is a combination of the KN amplitudes (with I = 0 and 1) and the KN amplitude ( I = 1) and is very sensitive to the various KN phase-shift solutions, some of which show an exotic I = 0, P 1 resonance. Our results have been expressed in terms of frequency distributions and cross sections, normalised by the Λ 0 π + reaction. These results have been compared with the predictions of various partial-wave analyses. Qualitatively we can eliminate the P 1 non-resonant solution, though no solution correctly predicts our results.

Medium-energy pion scattering and the alpha -cluster description of12C

The elastic, 2+ inelastic (4.43 MeV level) and total scattering cross sections of medium-energy pions on 12C have been calculated within Glauber theory using the microscopic alpha -cluster model. For the input the authors take the gaussian parametrised pi -N amplitude. It is found that the model gives a fairly good account of the scattering data. The agreement between the calculated and experimental angular distributions at higher energies is particularly good when the pi -N phase-shift solutions of Roper and Wright (1965) are used.

Bias-Free Pole Search on the S* Resonance

A pole-search technique developed recently is applied to the I=0 S-wave ππ amplitude. The S* pole is definitely found out at (1010±20)-i(30±20) MeV for the phase-shift solution of Hyams et al. (1973), that of Froggatt and Petersen (1977) and the β-solution of Martin and Pennington (1977) in agreement with most analyses, but not for the α-solution of the last authors. Negative arguments are made for the α-solution and for the analyses against the ordinary S* results.

Unique isospin-zero phase-shift solution for nucleon-nucleon scattering near 325 MeV

The recent measurement of D t in np scattering at 325 MeV by the BASQUE group permits a unique I = 0 phase shift solution to be determined, provided that the triplet G-wave phase shifts are constrained by theory.

Does the so-called dibaryon resonance exist?

It is pointed out that (i) in the study of p-p scattering around 1.5 GeV/c, the phase shift solution given by Hoshizaki et al. is consistent with the absence rather than the existence of a dibaryon resonance and (ii) there is a possible case in which not only σel (σtot) but also |ΔσL| may have apeak irrelevant to resonance.

Systematic study ofπ−pbackward elastic scattering between 1.28 and 3.0 GeV/c

We have measured the backward differential cross section in ${\ensuremath{\pi}}^{\ensuremath{-}}p$ elastic scattering at 31 momenta from 1.28 to 3.0 GeV/c. These measurements covered the center-of-mass angular range of 125\ifmmode^\circ\else\textdegree\fi{}-178\ifmmode^\circ\else\textdegree\fi{} corresponding to $\ensuremath{-}0.570\ensuremath{\lesssim}{cos\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\lesssim}\ensuremath{-}0.999$. Considerable structure in the angular distribution is found. We compare these data with data from other experimets and to predictions made by the latest phase-shift solution. We find, in general, good agreement with other data in the few regions of overlap. The fits from the phase-shift solution do not accurately reproduce these data at low momenta below 1.9 GeV/c but give excellent agreement above this momentum.

Kaon-nucleon finite energy sum rules revisited

Kaon-nucleon finite energy and continuous moment sum rule integrals are evaluated using recent phase-shift solutions to extract the t-channel exchange amplitudes and the results are compared with Regge pole models. The exchange degeneracy breaking previously observed in the ϱ and A 2 amplitudes is confirmed, and it is suggested that this may be due to an exotic P 01 KN resonance. Regge trajectories are extracted from the integrals and are in good agreement with those found from direct fits to high-energy data.