We report measurements of the invariant cross section in the forward hemisphere for inclusive photoproduction of π±, K±, p, and p¯ from hydrogen and deuterium with an incident photon energy of 18 GeV. A small amount of data was also taken at incident energies of 9 and 13 GeV. The measurements were made using the SLAC 20-GeV/c spectrometer, and a bremsstrahlung-subtraction technique was used to obtain the cross sections at the specified incident energy. The data are compared with those from lower-energy experiments and interpreted within the context of the Mueller-Regge model and the constituent-interchange model.
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The reaction π − p → ω n has been studied at 8 and 12 GeV / c incident momenta with the CERN Omega spectrometer using a neutron time of flight trigger. The differential cross sections and the ω-decay density matrix elements are presented as functions of the momentum transfer squared − t in the range of 0.02 to 0.80 GeV 2 . The data are used to evaluate the intercept and slope of both the natural and unnatural parity exchange trajectories. Regge exchange amplitude factorisation tests involving the reaction π N → ω N are investigated.
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In view of the possible production of heavy leptons or charmed states in e+e− collisions, we searched for anomalous muons with momenta pμ≳1 GeV/c. The inclusive cross section for nch>~3 has an upper limit of 96 pb (assuming isotropy). For nch=2 and noncoplanarity > 20°, an excess of muonic events is observed, corresponding to (dσdΩ)|90°=23−9+12 pb/sr; the probability that known processes produce the observed events is 2×10−4.
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We have done an inclusive study of ϱ 0 production in π − p interactions at 15 GeV/ c . Evidence for two different production mechanisms, in addition to the known quasi two-body processes, is presented: production of ϱ 0 's in the central region of rapidity similar to the “pionization” region seen in the inclusive studies of pions; and forward production in the beam dissociation region of rapidity. Cross sections and rapidity distributions for the ϱ 0 are given inclusively and by topology, and the results are compared with similar studies at other energies and with other incident particles. Results are also presented for the semi-inclusive reaction π − p → p ϱ 0 + X − and the exclusive final state p π − ϱ 0 .
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The reaction π−p→X−p, X−→ηπ−, η→γγ has been studied in an optical spark-chamber experiment at the Argonne ZGS (Zero Gradient Synchrotron) at a beam momentum of 6.0 GeV/c and with 0.27≤|t|≤0.42 (GeV/c)2. The ηπ mass spectrum contains about 1400 events in the mass range 0.80<M(ηπ)<1.55 GeV/c2, and is dominated by approximately 1000 events of the type A2−→ηπ−. No structure is discernible within the A2 mass spectrum for an experimental resolution of 7.1 MeV/c2 [16.7 MeV/c2 FWHM (full width at half maximum)]. A single D-wave Breit-Wigner distribution fits the data with a high confidence level, yielding for the A2 the parameters M0=1.323±0.003 GeV/c2 and Γ0=0.108±0.009 GeV/c2. The angular distribution of the decay A2−→ηπ− is analyzed and the resultant density matrix elements have the values ρ11=0.45±0.02, ρ1−1=0.45±0.04, and ρ00=0.09±0.04. All other elements are consistent with zero. Finally, the missing-mass spectrum in the region of the A2 is presented. A signal of 230 events above background per 5-MeV/c2 interval is observed at the A2 peak, with a signal to background ratio of greater than 1:1. A single D-wave Breit-Wigner distribution together with a quadratic background fits the data well, with the parameters for the A2 being M0=1.324±0.003 GeV/c2 and Γ0=0.104±0.009 GeV/c2. Both A2 mass spectra are incompatible with the dipole shape.
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THIS FIT ASSUMES ALL OTHER DENSITY MATRIX ELEMENTS (RHO(2M) AND RE(RHO(10))) ARE ZERO SINCE THEY ARE QUITE CONSISTENT WITH ZERO IN A FULL FIT. QUOTED ERRORS INCLUDE SYSTEMATIC ERRORS, WHILE STATISTICAL FITTING ERRORS ARE SHOWN SEPARATELY.
We have measured deep inelastic muon-deuteron scattering in the range 0.4<Q2<3.4 and 1.6<ν<5.6 GeV. We have extracted the neutron structure function and find that νW2n differs significantly from νW2p, as also found in e−d scattering. To compare μ−d and e−d scattering we form the ratio r(Q2)=(νW2)μd(νW2)ed=N(1+Q2Λ2)−2 and find N=0.925±0.038 and 1Λ2=−0.019±0.016.
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ONE EVENT SEEN - PROBABLY AN ANTIPROTON.
We report measurements of the ratio of the deep-inelastic electron-neutron to electron-proton differential cross sections in the threshold ( ω <3) region. The ratio was found to scale and to decrease monotically with decreasing ω . No violation of the quark model lower bound of 0.25 was observed in the ratio.
DATA ARE AVERAGED THROUG AVAILABLE KINEMATIC REGION.
Differential cross sections for electron scattering from hydrogen and deuterium in the deep-inelastic region show that the neutron cross section is significantly smaller than the proton cross section over a large part of the kinematic region studied. Although νW2d differs in magnitude from νW2p, it exhibits a similar scaling behavior.
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We have measured ep, eπ+, and eπ− coincidences for scattered electrons in the range Q2=0.4 to 2.2 GeV2 and W=2 to 4 GeV. We find (a) that vector-meson production decreases with Q2 more rapidly than does the total virtual-photon-plus-proton cross section, more rapidly even than the prediction of simple vector dominance, (b) that the slope of the t distribution in ρ and ω production becomes flatter with increasing Q2 and seems to be at least approximately a function of the single variable xρ=(Q2+mρ2)2Mν, (c) that the fraction of final states containing a proton decreases with increasing Q2, (d) that in the central region of longitudinal momenta the inclusive π+ yield seems to increase relative to the π− yield as Q2 increases, and (e) that the average transverse momentum of π− is greater than of π+ in the central region of longitudinal momenta.
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The data with (C=Q=RHO+OMEGA) are obtained by excluding the contribution from RHO and OMEGA production.
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The v and v nucleon total cross-sections have been determined as a function of energy using a sample of 2500 v and 950 v event. The results are compared with predictions of scaling and charge symmetry hypotheses.
Measured charged current total cross section.
Measured charged current total cross section.
Cross sections for inelastic scattering of electrons from hydrogen and deuterium were measured for incident energies from 4.5 to 18 GeV, at scattering angles of 18°, 26°, and 34°, and covering a range of squared four-momentum transfers up to 20 (GeVc)2. Neutron cross sections were extracted from the deuterium data using an impulse approximation. Comparisons with the proton measurements show significant differences between the neutron and proton cross sections.
Axis error includes +- 1/1 contribution (DUE TO ERRORS IN ABOVE CORRECTIONSFOR DEAD-TIME LOSSES, INEFFICIENCIES IN E- IDENTIFICATION).
We have measured angular distributions for single photoproduced π+ mesons at 4.0-, 5.0-, and 7.5-GeV incident photon energies and at lab angles from 11° to 66° with the Stanford Linear Accelerator Center 8-GeV spectrometer. Combined with previous Stanford Linear Accelerator Center results, this gives complete angular coverages for this range of energies. The data show the usual "t" and "u" diffraction peaks and a "central plateau" region dropping as S−7.3.
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We have found 431 events of the reaction K+d→K0pps at 3.8−GeVc K+ beam momentum in a 295 000-frame exposure of the Argonne National Laboratory 30-in. deuterium-filled bubble chamber. The event sample consists of one- and two-prong events with a visible K0 decaying to π+π− The total and differential cross sections are found after correction for unseen K0's and for efficiencies in the scanning-measuring-fitting chain. Comparisons of the data are made to an SU(3) sum rule, a Regge model, and data for K−p→K¯0n.
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GLAUBER SCREENING AND PAULI EXCLUSION PRINCIPLE CORRECTIONS ARE REQUIRED TO YIELD THE K+ N CHARGE EXCHANGE CROSS SECTION. THE GLAUBER CORRECTION IMPLIES AN INCREASE IN THE CROSS SECTIONS BY THE FACTOR 1.016. THE PAULI CORRECTION IS SLIGHT EXCEPT AT LOW -T (<0.2 GEV**2) WHERE IT IS LARGE AND UNCERTAIN.
We have measured ρ0, ω (combined) and ϕ electroproduction over a range of virtual-photon four-momentum Q2 from 0.4 to 2.2 GeV2 and for photon energies ν from 2.7 to 8.6 GeV. We find that the slope of the t (momentum transfer) dependence of the ρ0 and ω forward peak decreases with increasing Q2 to less than half of the photoproduction slope.
The cross section for virtual photon are derived from E- P cross section bydividing on the virtual-photon flux factor.
We have extracted the strong interaction form factors from K o e3 and K o μ3 data of our previously reported K o L experiment in a manner which does not assume an explicit q 2 = ( p K − p π ) 2 dependence. We present the unparameterized form factors ƒ + (q 2 ) from the K o L → πeν and K o L → πμν modes and ƒ o (q 2 ) and ξ ( q 2 ) from the K o L → πμν data. A comparison of these unparameterized results is made with the results of the Dalitz plot analyses.
The conventional form factor f+ is studied.
We have measured the asymmetry parameter Σ=(σ∥−σ⊥)(σ∥+σ⊥) for the photoproduction of ϕ mesons with photons polarized parallel and perpendicular to the plane of decay for the reaction γp→ϕp→K+K−p. We find Σ=0.985±0.12 at a photon energy of 8.14 GeV and |t| of 0.2 (GeVc)2, consistent with pure diffraction production, or pure naturalparity Regge exchange.
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Electron-proton elastic-scattering cross sections have been measured at the Stanford Linear Accelerator Center for four-momentum transfers squared q 2 from 1.0 to 25.0 (GeVc)2. The electric (GEp) and magnetic (GMp) form factors of the proton were not separated, since angular distributions were not measured at each q 2. However, values for GMp were derived assuming various relations between GEp and GMp. Several theoretical models for the behavior of the proton magnetic form factor at high values of q 2 are compared with the data.
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We have studied the proper time distribution of coherent π + π − decays from a 3 – 10 GeV/ c K L o beam incident on a one meter liquid hydrogen target using a wire spark chamber spectrometer in the 3 0 neutral beam at SLAC. We find ∣(ƒ(0) − ƒ (0))/k∣ = 0.43 ± 0.11 mb , φ(ƒ(0) − ƒ (0)) = -101 0 ± 42 0 .
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Differential cross sections for electrons scattered inelastically from hydrogen have been measured at 18°, 26°, and 34°. The range of incident energy was 4.5 to 18 GeV, and the range of four-momentum transfer squared was 1.5 to 21 (GeVc)2. With the use of these data in conjunction with previously measured data at 6° and 10°, the contributions from the longitudinal and transverse components of the exchanged photon have been separately determined. The values of the ratio of the photoabsorption cross sections σSσT are found to lie in the range 0 to 0.5. The question of scaling of 2MpW1 and νW2 as a function of ω is discussed, and scaling is verified for a large kinematic range. Also, a new scaling variable which reduces to ω in the Bjorken limit is introduced which extends the scaling region. The behavior of σT and σS is also discussed as a function of ν and q2. Various weighted sum rules of νW2 are evaluated.
Axis error includes +- 0.0/0.0 contribution (0. TO 2.////DUE TO PION CONTAMINATION).
Axis error includes +- 0.0/0.0 contribution (0. TO 2.////DUE TO PION CONTAMINATION).
Axis error includes +- 0.0/0.0 contribution (0. TO 2.////DUE TO PION CONTAMINATION).
Compton-scattering cross sections from hydrogen (γp→γp) and from deuterium have been measured at four-momentum transfer t in the range 0.014<~−t<~0.17 GeV2 and photon energies of 8 and 16 GeV. Fits to our proton data of the form dσdt=AeBt give B≈7.8 GeV−2 and an intercept A which is in agreement with the optical point. Both coherent scattering from deuterons and incoherent scattering from neutrons and protons are seen from deuterium. A small difference between the neutron and proton cross sections is seen, indicating the presence of about a 3% isovector t-channel exchange amplitude in addition to the predominant isoscalar amplitude. The vector-dominance model predicts lower cross sections (by at least 20%) for both the hydrogen and deuterium cases.
Axis error includes +- 3/3 contribution (SUBTRACTIONS WERE MADE FOR THE REACTIONS GAMMA P --> PI0 N, ETA N, OMEGA N AND PI0 DELTA(1232)).
Axis error includes +- 3/3 contribution (SUBTRACTIONS WERE MADE FOR THE REACTIONS GAMMA P --> PI0 N, ETA N, OMEGA N AND PI0 DELTA(1232)).
Cross sections for π − p→n π o at 5.9, 10.1 and 13.8 GeV/ c incident momentum are presented in the angular region from 180 o to u , the crossed four-momentum transfer squared, of −2(GeV) 2 and the energy dependence is discussed. The cross section for π − p→n η o integrated over the same angular region at 5.9 GeV/ c is also presented.
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Electron-proton elastic scattering cross sections have been measured at the Stanford Linear Accelerator Center at four-momentum transfers squared (q 2 ) of 1.0, 1.5, 2.0, 2.5and 3.75 (GeV/ c ) 2 . The angular distributions at q 2 = 2.5 and 3.75 (GeV/ c ) 2 are sufficient to provide values of the ratio G E / G M independent of the results from other laboratories. Our results are compatible with scaling, G E (q 2 ) = G M (q 2 )/ μ , within the experimental errors.
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