The differential cross section of π+p elastic scattering has been measured in two high-statistics bubble-chamber exposures at laboratory beam momenta of 3.7 and 7.1 GeV/c. A new feature suggested by these data is a dip in dσdu at −u≃3 GeV2. This dip corresponds well to the third zero of J0(b−u′), where ℏcb=1 fm. The effective u-channel Regge trajectory computed for these two energies has a slope of 0.22 ± 0.26.
No description provided.
In diffractive photoproduction ofηπ+π−, the two-body substatesηρ0 andA2π are found to contribute significantly to the cross-section forηπ+π− masses below 2.4 GeV. From a spin-parity analysis the branching ratio, ρ′(1600)→ηρ/ρ′(1600)→, is determined to be <0.02 at the 68.3% confidence level. TheA2π component shows an enhancement around 1.7 GeV. The spin-parity analysis indicates a probable contribution to this signal from exclusive photoproduction of theg(1690).
No description provided.
Not corrected for 35% background under the eta --> gamma gamma peak.
Not corrected for 35% background under the ETA --> GAMMA GAMMA peak.
We have made improved measurements of 43.8 ± 0.8, 41.3 ± 0.4 and 39.3 ± 0.8 mb for the p p elastic cross sections at 1.11, 1.33 and 1.52 GeV/ c laboratory momenta respectively. Sharp forward peaks in the differential cross sections with broad secondary maxima agree with previous observations [3–6]. The forward differential cross sections are (11 ± 3)% above the optical point in agreement with real amplitudes extended from lower momenta using dispersion relations [7]. The elastic cross sections do not show any structure in the s -channel. Backward differential cross sections show the onset of a “third diffraction peak” but no evidence for other structure in agreement with earlier experiments [6, 13].
STATISTICAL PLUS SYSTEMATIC ERRORS.
COUNTS WERE MULTIPLIED BY 1.000 TO GET THESE.. TOTAL NUMBER EVENTS= 543. READ FROM GRAPH.
COUNTS WERE MULTIPLIED BY .420 TO GET THESE.. TOTAL NUMBER EVENTS= 1099. READ FROM GRAPH.
Interactions of 683-MeV/c negative pions with protons were investigated using the BNL 14-in. hydrogen bubble chamber in a 17-kG field. Two thousand elastic scatterings were analyzed, yielding a cross section of 18.9±1.0 mb. No evidence for powers of cosθ higher than the second was observed in the elastic angular distribution. The angular distribution obtained was dσdω=(0.384±0.026)+(1.70±0.06)cosθ+(3.36±0.11)cos2θ mb/sr. The single-pion production reactions π−+p→π−+π0+p and π−+p→π−+π++n were studied in detail. A total of 441 π0 productions and 833 π+ productions were analyzed giving cross sections of 3.99±0.50 and 7.50±0.80 mb, respectively. The differential distributions for these inelastic processes are presented and compared with the predictions of the model of Olsson and Yodh. The distribution of events on the Dalitz plots for π0 production is accounted for by the model. However, for the π+ reaction, the model (so far developed) does not describe adequately the distribution of events on the Dalitz plot. In particular, the model fails to account for the enhancement at high (π+π−) effective masses in ππ mass distribution. The center-of-mass angular distributions for π0 and π+ production reactions are presented and compared with the model.
No description provided.
No description provided.
The total cross section of γ rays in hydrogen resulting in hadron production, σT, has been measured over the energy range 265-4215 MeV. A tagging system with narrow energy bins was employed. Structure in the resonance region followed by a steady fall with energy has been observed and the results are analyzed. The forward amplitude of γ-proton scattering is evaluated, and its behavior in the Argand diagram studied as a function of energy. The relationships of the measurements to Regge-pole theory and the vector-dominance model are detailed.
SPIN AVERAGED FORWARD COMPTON SCATTERING AMPLITUDE. IM(AMP) WAS CALCULATED VIA THE OPTICAL THEOREM FROM A SMOOTH FIT TO THE DATA, AND USED IN THE DISPERSION RELATION TO CALCULATE RE(AMP). AT THRESHOLD THE THOMSON AMPLITUDE IS -3.0 MUB*GEV.
The total cross section for photoproduction of hadrons on the deutron, σ T d , has been measured for photon energies in the range 0.265–40215 GeV. From this, using results for the photon total cross section, obtained previously with the same apparatus, the neutron total cross section has been determined in the resonance region. The resonant structure is found to be quite different from that for the proton. Thereafter the neutron cross section falls off steadily with energy, and the values obtained are consistently lower than those for the proton. Forward scattering amplitudes have been evaluated for the deuteron.
SPIN AVERAGED FORWARD COMPTON SCATTERING AMPLITUDE. IM(AMP) WAS CALCULATED VIA THE OPTICAL THEOREM FROM A SMOOTH FIT TO THE DATA AND RE(AMP) WAS CALCULATED USING THE FORWARD DISPERSION RELATION. THE ESTIMATE OF -1.7 MUB*GEV FOR THE FIXED POLE CONTRIBUTION IS COMPARABLE WITH THE THOMPSON THRESHOLD AMPLITUDE OF -3 MUB*GEV.
Based on 150 000 photographs taken at the ZGS with the 30 inch deuterium-filled chamber we present an analysis of the elastic p d scattering reaction. Due to unrecoreded small deuteron recoils we were only able to measure the elastic cross section in the four-momentum region | t | > 0.03 (GeV/ c ) 2 . Extrapolation towards small | t | by two different methods gave us two compatible estimates of the total elastic cross section. The differential cross section was analyzed by means of the Glauber formalism both with and without the effects due to the D-wave part of the deuteron wave function. The differential cross sections of np at 5.4 GeV/ c and pn deduced from our data were compared and exhibit a crossover phenomenon.
CALCULATED USING TOTAL ELASTIC SIG(-T > 0.03 GEV**2) = 7.2 +- 0.4. THE SMALL ANGLE SCATTERING APPROXIMATION HOLDS: D(SIG)/DOMEGA(RF=LAB) = (P**2/PI)*D(SIG)/DT.
INTEGRATED CROSS SECTION USING EITHER EXPONENTIAL EXTRAPOLATION OR GLAUBER MODEL FIT FOR -T < 0.03 GEV**2.
Absolute π±p elastic scattering differential cross sections have been measured at five incident pion energies between 87 and 139 MeV. An active target of scintillator material (CH1.1) was used to detect recoil protons in coincidence with scattered pions. Pions were detected at forward angles between 27 and 98°c.m. where the low-energy recoil protons stop in the target. The cross sections, typically 5–10% lower than phase shift predictions for π+p and 10–20% lower for the π−p cross sections, are consistent with earlier measurements by this group.
No description provided.
No description provided.
No description provided.
We present direct measurements of the $Z~0$-lepton coupling asymmetry parameters, $A_e$, $A_\mu$, and $A_\tau$, based on a data sample of 12,063 leptonic $Z~0$ decays collected by the SLD detector. The $Z$ bosons are produced in collisions of beams of polarized $e~-$ with unpolarized $e~+$ at the SLAC Linear Collider. The couplings are extracted from the measurement of the left-right and forward-backward asymmetries for each lepton species. The results are: $A_e=0.152 \pm 0.012 {(stat)} \pm 0.001 {(syst)}$, $A_\mu=0.102 \pm 0.034 \pm 0.002$, and $A_\tau=0.195 \pm 0.034 \pm 0.003$.
No description provided.
Measurements are presented of the cross section ratios R ℓ = σ ℓ ( e + e − →ℓ + ℓ − ) σ h ( e + e − →hadrons) for ℓ=e, μ and τ using data taken from a scan around the Z 0 . The results are R e =(5.09± o .32±0.18)%, R μ =(0.46±0.35±0.17)% and R τ =(4.72±0.38±0.29)% where, for the ratio R e , the t -channel contribution has been subtracted. These results are consistent with the hypothesis of lepton universality and test this hypothesis at the energy scale s ∼8300 GeV 2 . The absolute cross sections σ ℓ (e + e − →ℓ + ℓ − ) have also been measured. From the cross sections the leptonic partial widths Γ e =(83.2±3.0±2.4) MeV, (Γ e Γ μ ) 1 2 =(84.6±3.0±2.4) MeV and (Γ e Γ τ ) 1 2 =(82.6±3.3±3.2) MeV have been extracted. Assuming lepton universality the ratio Γ ℓ Γ h =(4.89±0.20±0.12) × 10 −2 w was obtained, together with Γ ℓ =(83.6±1.8±2.2) MeV. The number of light neutrino species is determined to be N v =3.12±0.24±0.25. Al the data are consistent with the predictions of the standard model.
E+ E- final state is t-channel subtracted.
No t-channel subtraction. Statistical errors only.
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