Interactions initiated by 3-Bev protons of the Brookhaven Cosmotron were studied by photoemulsion technique. With appropriate criteria, 115 events are attributed to interactions of the incident beam protons with hydrogen nuclei (∼55%) and with bound protons of other nuclei (∼45%). A detailed analysis allowed the subdivision of the 115 events in categories, according to the number of π mesons (N>~0) produced in the collision. The ratio of elastic scattering to the total number of events was estimated to be σelσtotal=0.20−0.07+0.04. The observed cross section for pure elastic scattering is σel=8.9±1.0 mb. The percentages of single, double, triple, and quadruple π-meson production are respectively: 34−20+22; 35.6−23+20; 9.6−4+6; ∼1.0+3.5. Among the 20 most probable cases of single π-meson production—the estimated ratio of π+ to π0 is σπ+σπ0=5.3−1.4+0.3. The experimental results are not in agreement with the Fermi statistical-model theory (in particular the lower limit for the experimental ratio of triple to single production is given by σ3σ1>∼110 in contrast with the predicted ratio σ3σ1=167) but are not inconsistent with the Peaslee excited-state-model theory.

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This paper reports experimental findings on the Dirac (F1) and Pauli (F2) form factors of the proton. The form factors have been obtained by using the Rosenbluth formula and the method of intersecting ellipses in analyzing the elastic electron-proton scattering cross sections. A range of energies covering the interval 200-1000 Mev for the incident electrons is explored. Scattering angles vary from 35° to 145°. Values as high as q2≅31 f−2 (q=energy−momentumtransfer) are investigated, but form factors can be reliably determined only up to about q2=25 f−2. Splitting of the form factors is confirmed. The newly measured data are in good agreement with earlier Stanford data on the form factors and also with the predictions of a recent theoretical model of the proton. Consistency in determining the values of the form factors at different energies and angles gives support to the techniques of quantum electrodynamics up to q2≅25 f−2. At the extreme conditions of this experiment (975 Mev, 145°) the behavior of the form factors may be exhibiting some anomaly.

The total cross sections σT of p, p¯, π±, and K± on hydrogen and deuterium have been measured between 6 and 22 GeVc at intervals of 2GeVc to an accuracy greater than previously reported. The method utilized was a conventional good-geometry transmission experiment with scintillation counters subtending various solid angles at targets of liquid H2 and D2. With the increase in statistical accuracy of the data, it was found that a previously adopted procedure of linearly extrapolating to zero solid angle the partial cross sections measured at finite solid angles was not a sufficiently accurate procedure from which to deduce σT. The particle-neutron cross sections are derived by applying the Glauber screening correction to the difference between the particle-deuteron and particle-proton cross sections. The cross sections σT(π+d) and σT(π−d) are equal at all measured momenta, which confirms the validity of charge symmetry up to 20GeVc. Results are presented showing the variation of cross sections with momentum; evidence is presented for a small but significant decrease in σT(pp) [and σT(pn)] in the momentum region above 12GeVc.

Absolute measurements of the elastic electron-proton cross section have been made with a precision of about 4% for values of the square of the four-momentum transfer, q2, in the range 6.0 to 30.0 F−2 and for electron scattering angles in the range 45° to 145°. To within the experimental errors, it is found that the charge and magnetic form factors of the proton have a common dependence on q2 when normalized to unity at q2=0, and that an accurate representation of the behavior of the form factor and that of the cross sections themselves can be given in terms of a three-pole approximation to the dispersion theory of nucleon form factors.

Three new bosons, referred to as S, T and U, have been observed in the reaction π - + p → p + X - using the missing-mass spectrometer; their masses are 1929, 2195 and 2382 MeV, respectively. Their physical widths are equal to our experimental resolution and compatible with zero-width, with the upper limits: Γ ≤ 35, ≤ 13 and ≤ 30 MeV, respectively. They are produced with the differential cross section d σ/d t between 20 and 40 microbarn per (GeV/ c ) 2 at an average t = 0.3 (GeV/ c ) 2 .

Three narrow peaks with masses 1632 ± 15, 1700 ± 15 and 1748 ± 15, reffered to as R 1 , R 2 and R 3 , have been observed in missing-mass spectrometer runs at incident pion momenta of 7 and 12 GeV/ c and a mass-resolution of ± 15 MeV. One-peak hypothesis gives a confidence level P ( χ 2 )=0.8%; the three-peak one gives P ( χ 2 )=60%. Statistical significance for R 1 , R 2 and R 3 is, respectively, 3.8, 6.6 and 6.1 standard deviations from the highest background line. R 1 and R 2 decay into one and three, while the R 3 decays mainly into three charged particles. Their physical widths are compatible with zero, with upper limits of the order of Γ ⩽30 MeV.

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Differential cross sections for elastic π±−p scattering have been measured at lab momenta of 8 and 12 GeV/c in a momentum-transfer region corresponding to 1.2≤−t≤6 (GeV/c)2. Also, differential cross sections near 180° were measured for 4 and 8 GeV/c pions. At momentum transfers greater than −t=2 (GeV/c)2, the π−p cross sections drop much faster with increasing angle than the corresponding p−p cross sections. Also, in the region −t≃1.3 (GeV/c)2, there is structure in the π−p angular distribution but not in the p−p angular distribution. At −t≃3 (GeV/c)2, the drop in cross section appears to stop and from then on the angular distribution is consistent with isotropy. But in the angular region 170° to 180°, the cross sections have become much larger, and sharp backward peaks are observed. Information is given on the energy and charge dependences and widths of these backward peaks.

The differential cross section for the reaction γ+p→π++n was measured at 32 laboratory photon energies between 589 and 1269 MeV at the Caltech synchrotron. At each energy, data have been obtained at typically 15π+ angles between 6° and 90° in the center-of-mass (c.m.) system. A magnetic spectrometer was used to detect the π+ photoproduced in a liquid-hydrogen target. Two Cerenkov counters were used to reject background of positrons and protons. The data clearly show the presence of a pole in the production amplitude due to one-pion exchange. Moravcsik fits to the angular distributions, including data from another experiment carried out by Thiessen, are presented. Extrapolation of these fits to the pole gives a value for the pion-nucleon coupling constant of 14.2±1.7, which is consistent with the accepted value. The "second" and "third" pion-nucleon resonances are evident as peaks in the total cross section and as changes in the shape of the angular distributions. At the third resonance, there is evidence for both a D52 and an F52 amplitude. The absence of large variations with energy in the 0° and 180° cross sections implies that the second and third resonances are mostly produced from an initial state with helicity 32.

We have measured the differential cross section for π−p elastic scattering at 180° in steps of 0.10 GeV/c or less in the region P0=1.6 to 5.3 GeV/c. We detected elastic scattering events, from protons in a liquid H2 target, with a double spectrometer consisting of magnets and scintillation counters in coincidence. The incident π− beam was counted by scintillation counters. The cross section was found to have considerable structure. This may be interpreted as interference between the resonant amplitudes and the nonresonant or background amplitude. Very strong destructive interference occurs around P0=2.15 GeV/c, where the cross section drops almost two orders of magnitude in passing through the N*(2190). Another interesting feature of the data is a large narrow peak in the cross section at P0=5.12 GeV/c, providing firm evidence for the existence of a nucleon resonance with a mass of 3245±10 MeV. This N*(3245) has a full width of less than 35 MeV, which is about 1% of its mass. From this experiment we were able to determine the parity and the quantity χ(J+12) for each N* resonance, where χ is the elasticity and J is the spin of the resonance.

Cross section angular distributions for [...] photoproduction from hydrogen were measured for 28 laboratory photon energies from 574 to 1211 MeV. At most energies, the [...] center of mass angle was varied from 60[degrees] to 170[degrees] in steps of 10[degrees]. A magnetic spectrometer was used to measure the momentum and angle of the recoil proton. A scintillation counter hodoscope with lead convertors was used to detect the presence of at least one of the [...] decay gamma rays. For a majority of the measurements the [...] rates were separated from a contamination of pi pair rates using the difference in their distribution among the gamma counters. For the remainder of the measurements, charged pi pairs were eliminated using veto counters in front of the gamma counters. Internal inconsistency and comparison with other experiments indicate that the veto data are 10 to 15% low near 90[degrees] in the region of 750 MeV. The remainder of the data show good internal consistency and fair agreement with data of other experiments. The results show a peak at 140[degrees] near 1050 MeV which had been expected but not previously measured. Comparison of the backward angle data with that from experiments measuring cross sections very near 180[degrees] indicates either an inconsistency between experiments or a rapid drop in the cross section near 180[degrees] in the region around 800 MeV.

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The differential cross section for neutron-proton elastic scattering was measured in the diffraction region with incident-neutron momenta between 8 and 30 GeV/c. The experiment was a spark-chamber-counter experiment, conducted at the alternating-gradient synchrotron. Results are presented and compared with currently available lower energy np data and comparable energy pp data.

The cross section for γp→π−Δ++(1236), measured at 5, 8, 11, and 16 GeV from nearzero momentum transfer to -1 GeV2 (-2 GeV2 at 16 GeV), rises from small t to a maximum near −t=mπ2, then falls as e12t out to −t≈0.2 GeV2, after which it becomes roughly equal in slope and magnitude to the single π+ photoproduction cross section (e3t). At fixed t, the cross section varies as k−2, where k is the laboratory photon energy. The results do not agree well with the simple vector-dominance model.

The differential cross sections for the elastic scattering of negative pions by deuterons have been measured for 2.01-, 3.77-, and 5.53-GeV/c incident pion momenta, over an interval of the squared four-momentum transfer from -0.25 (GeV/c)2 to ∼-1.0 (GeV/c)2. The results are consistent with calculations based on a Glauber model of the scattering process.

π±p elastic differential cross sections in the momentum range 1.72-2.80 GeV/c have been measured at the proton synchrotron "NIMROD" of the Rutherford High Energy Laboratory. The results are tabulated, and analyses of the differential cross sections employing optical models and Legendre polynomial expansions are advanced. A critical discussion of a recent interpretation of differential-cross-section structure in terms of interference between resonant and background amplitudes is presented.

Elastic π±−p, K−−p, and p¯−p scattering cross sections have been measured using three different experimental arrangements covering the c.m. angular regions ∼20°-120°, ∼135°-169°, and ∼165°-180° at incident momenta from 6 to 17 GeV/c. In the region 130°-180°, only π±−p scattering was measured. In the angular region near 180°, the energy dependences and shapes of the π−p backward peaks were determined up to crossed-momentum transfers of u∼−2 (GeV/c)2. At all energies, the π+−p backward peak had a sharp dip at u=−0.13 (GeV/c)2, with no similar effect in the π−−p case. Nearly complete angular distributions of π−−p elastic scattering from 20° to 180° have been obtained at 6 and 10 GeV/c. These results at 6 and 10 GeV/c as well as at 8 GeV/c reveal a sharp dip in π−−p scattering at t=−3 (GeV/c)2. Several structures in the form of dips or shoulders were seen in the p¯−p angular distributions also, with less pronounced structure observed in K−−p scattering. At fixed momentum transfer, all cross sections when expressed as dσdt appear to be decreasing with increasing energy.

Total and differenial cross sections of the reaction γ +n→p+ π − have been determined for photon-energies between 0.2 and 2.0 GGeV. Below 500 MeV the differential cross sections are compared with theoretical predictions derived from fixed-momentum-transfer dispersion relations.

Cross sections for the reactions γp→K+Λ and γp→K+Σ0 have been measured at squared four-momentum transfer (−t) from 0.005 to 2 GeV2, at photon energies 5, 8, 11, and 16 GeV. For −t>0.2 GeV2 each of the K+ cross sections is about ⅓ of the π+n photoproduction cross section, having nearly the same energy and momentum-transfer dependence. The K+ cross sections fall off at small |t|, however, in contrast to the sharp forward spike seen in π+n; this leads to a disagreement with an SU(3) prediction for −t<0.1 GeV2. The ratio of K+Σ0 to K+Λ cross sections is typically between 0.5 and 1.0.

Differential cross sections have been measured for π − p elastic scattering at laboratory momenta in the range 1.2 to 3.0 GeV/ c for the c.m. range 0.97 > cos θ ∗ > −0.98 . The corresponding mass range is 1.78 to 2.56 GeV/ c 2 . The data was obtained from a counter experiment in which the scattered pions and protons were detected in coincidence by arrays of scintillation counters.

The differential cross section for the reaction γ+n→π−+p was measured for laboratory photon energies between 600 and 1250 MeV, using a liquid deuterium target. The internal nucleon momentum distribution of the deuteron was used to calculate the major effect of using deuterium as a neutron target. The data show that the amplitude to excite the F15(1688) resonance is small, in agreement with a recent quark-model prediction.

An experiment designed to study the π−p total neutral cross section and its breakdown into several channels has been performed at eleven incident pion momenta ranging from 654 to 1247 MeV/c. Angular distributions for the charge exchange π0 and for η0 production are given in terms of Legendre-polynomial expansion coefficients. Forward and backward differential cross sections are presented for the charge-exchange channel and comparisons with recent dispersion-relation predictions for the forward cross section are made.

The differential cross sections for the γ + n → π O + n reaction have been measured at the photon energies of 500–900 MeV. The ratios, R oo = [ d δ d Ω(γ n → π o n ) ] [ d δ d Ω(γ p → π o p ) ] , have been obtained at the c.m. pion angles of 60 O , 90 O , 105 O , 120 O , and 140 O .

Polarization and differential cross section data for elastic proton-proton scattering between 0.86 and 2.74 GeV/ c are presented. A comparison is made with existing phase-shift analyses.