We present data on the five final states Λω, Λφ, Λϱ 0 , Σ 0 ⊘ and Σ 0 ϱ 0 produced in 3.1–3.6 GeV/ c K − p interactions. These data are from a bubble chamber experiment with 18 events/μb. For all reactions the data consist of the overall and differetial cross sections, and the hyperon polarisation and the vector meson's density matrix elements as a function of momentum transfer. For Λω and Λ⊘, an almost complete amplitude analysis is performed in several regions of momentum transfer. The data are examined from the point of view of various exchange models.
CORRECTED FOR UNSEEN DECAY MODES OF LAMBDA, OMEGA AND PHI.
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NO BACKWARD PHI PRODUCTION.
Results are reported based on a study of 3114 π−p events at 205 GeV/c in the National Accelerator Laboratory 30-in. bubble chamber. The measured π−p total and elastic cross sections are 24.0 ± 0.5 and 3.0 ± 0.3 mb, respectively. The elastic differential cross section has a slope of 9.0 ± 0.7 GeV−2 for 0.03≤−t≤0.6 GeV2. The average charged-particle multiplicity for the inelastic events is 8.02 ± 0.12.
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Results are presented for the quasi two-body hypercharge exchange reactions of the type using data from a high statistics bubble chamber experiment. Total and differential cross sections and the momentum transfer dependence of the meson and hyperon resonance single density matrix elements are discussed. Amplitude analyses are performed for the first two reactions. The results are compared with quark model and duality predictions and with those from other related reactions.
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Evidence for narrow states produced by Σ − interactions in beryllium, and decaying into ( Λ p + pions ), has been obtained in an experiment at the CERN SPS hyperon beam. At 3.1 GeV/ c 2 , the ( Λ p π + π + ), ( Λ p π + π + π − ) and ( Λ p π + π − ) effective mass distributions show an excess of 45, 19 and 62 events above a background of 50, 28 and 187, respectively. The possibility that these three signals are statistical fluctuations is remote. The observed widths of the signals are compatible with the mass resolution of the apparatus, 24 MeV/ c 2 FWHM. We have not been able to find an interpretation of the quantum numbers of the final states, which are baryon number 0, strangeness −1 and charge +1, 0 and −1.
A comparison is made of the low-mass three-meson systems (πππ), (Kππ), (π K K ) and ( K K K ) diffractively produced in the reaction meson + proton → three mesons + proton. Several striking similarities and a few important differences are observed: (i) the reactions are consistent with the assumption that the three mesons decay entirely into a 0 − meson and a 0 + , 1 − or 2 + resonance; (ii) the three-meson mass spectra have a peak ≈ 250 MeV above the effective threshold M eff of the dominant decay mode and then fall off approximately as (mass) −3 ;(iii) the average spin 〈 J 〉 = 0.55 + 1.1 Q eff , where Q eff = M - M eff ; (iv) the average orbital angular momentum 〈 l 〉 increases according to 〈 l 〉 = 0.75 Q eff ; (v) the three-meson states are produced dominantly in unnatural spin-parity states and no evidence for their being resonant is found; (vi) the only natural spin-parity states found are the well-established 2 + resonances A 2 and K ∗ (1420); they have similar properties to the non-resonant unnatural parity states except for a dip at t = 0 in the dσ/d t distributions; (vii) both the unnatural and natural spin-parity states are produced mostly by an exchange of natural parity; (viii) there is evidence for two types of production mechanism with different polarization properties, one approximately conserving helicity in the t -channel and the other in the s -channel.
Momenta of charged particles produced in inelastic αα, αp, andpp collisions were measured using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. Inclusive and semi-in-clusive spectra are presented as a function of rapidityy, Feynman-x, and transverse momentumpT. The inclusivey distributions agree well with predictions of the dual parton model; the highest particle densities are reached aty≃0 and the momenta of leading protons decrease significantly for increasing total multiplicity. ‘Temperatures’ are equal in αα, αp, andpp interactions. ThepT distributions depend weakly on the multiplicity.
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We have measured the differential cross section for pp and p̄p elastic scattering at √ s = 31, 53 and 62 GeV in the interval 0.05 < | t | < 0.85 GeV 2 at the CERN ISR using the Split Field Magnet detector. At 53 and 62 GeV, for 0.17 < | t | < 0.85 GeV 2 both pp and p̄p data show simple exponential behaviour in t ; at √ s = 31 GeV the data for 0.05 < | t | < 0.85 GeV 2 are consistent with a change in slope near | t | = 0.15 GeV 2 .
ERRORS CONTAIN BOTH STATISTICAL AND T-DEPENDENT SYSYEMATIC ERRORS.
No description provided.
LOCAL SLOPE PARAMETERS BASED ON QUADRATIC EXPONENTIAL FIT.
Antiproton-proton elastic scattering was measured at c.m.s. energies √s =546 and 1800 GeV in the range of four-momentum transfer squared 0.025<-t<0.29 GeV2. The data are well described by the exponential form ebt with a slope b=15.28±0.58 (16.98±0.25) GeV−2 at √s =546 (1800) GeV. The elastic scattering cross sections are, respectively, σel=12.87±0.30 and 19.70±0.85 mb.
Final results (systematic errors included).
Final results (systematic errors included).
Statistical errors only. Data supplied by S. Belforte.
In partial wave analyses of the ( π − π − π + ) system, substantial shape changes of the 1 + S ( ϱπ ) intensity as a function of t , and relative phase changes of ≈ 90°, provide compelling evidence for a resonant A 1 of mass ≈ 1280 MeV and width ≈ 300 MeV.
Exclusive production of $\rho^0$ and $J/\psi$ mesons in e^+ p collisions has been studied with the ZEUS detector in the kinematic range $0.25 < Q^2 < 50 GeV^2, 20 < W < 167 GeV$ for the $\rho^0$ data and $2 < Q^2 < 40 GeV^2, 50 < W < 150 GeV$ for the $J/\psi$ data. Cross sections for exclusive $\rho^0$ and $J/\psi$ production have been measured as a function of $Q^2, W$ and $t$. The spin-density matrix elements $r^{04}_{00}, r^1_{1-1}$ and $Re r^{5}_{10}$ have been determined for exclusive $\rho^0$ production as well as $r^{04}_{00}$ and $r^{04}_{1-1}$ for exclusive $J/\psi$ production. The results are discussed in the context of theoretical models invoking soft and hard phenomena.
Exclusive RHO0 electro- and photo- production and cross sections as a function of Q**2 from the BPC data set.
Exclusive RHO0 electro- and photo- production cross section as a function of W from the BPC data set.
Exclusive RHO0 electro- and photo- production cross sections as a function of W from the DIS data set.
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