We have measured cross sections, rapidity and transverse momentum distributions, and vector meson polarization for the reactions pp→ ϱ o +anything, pp→ ω +charged particles, and pp → K ∗± + anything at incident laboratory momenta of 12 and 24 GeV/ c . We discuss various consequences of our results as well as possible connections with lepton pair production.
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DATA OBTAINED FROM FIGURE BY A.A. LEBEDEV.
DATA OBTAINED FROM FIGURE BY A.A. LEBEDEV.
The reaction of K − p → Σ + (1660) π − was studied in a 65 event/μb sample of Σππ(π), Λππ(π) and p K 0 π − final states. The main production features observed are that the Σ (1660) decaying into Σππ is mostly Λ (1405) π and is produced only at small t ; the Σ (1660) decaying into Σπ shows both forward and backward production. This confirms earlier results suggesting the existence of two Σ (1660) resonances. An Adair analysis and a (model-dependent) moments analysis find a J = 3 2 preference for the Σ + (1660)→ Λ (1405) π + → Σ + π − π + ; a Dalitz-Miller analysis of the decay Σ + (1660) → Λ (1405) π + → Σ − π + π + determines J P to be 3 2 − . For the Σ + (1660) → Σ 0 π + a moments analysis suggests J = 3 2 . Branching ratios are determined, which (with the exceptation of the Λ (1405) π mode) are in reasonable agreement with results from formation experiments for the J P = 3 2 − Σ(1660) resonance. We compare our branching ratios with SU(3) and SU(6) predictions; the latter comparison suggests that, unless there is strong configuration mixing, Σ (1660) → Λ (1405) π , if 3 2 − , cannot be a member of the (70, 1 − ) multiplet.
No description provided.
PRODUCTION ANGULAR DISTRIBUTIONS OF SIG(1670D13)+ DIFFER FOR THE TWO FINAL STATES <LAM(1405S01) PI+> AND <SIGMA PION> SUGGESTING THE EXISTENCE OF TWO SIG(1660) RESONANCES.
VALUES IN STRONG DISAGREEMENT WITH THE STODOLSKY-SAKURAI MODEL PREDICTIONS.
Cross sections have been determined for the inclusive production of vector (ϱ 0 , ω, K ∗ ) and tensor (f, A 2 ± ) mesons in p p reactions at 9.1 GeV/c for both annihilation and non-annihilation processes. Distributions in the Feynman variable x and transverse momentum squared, p T 2 , have been examined for the ϱ 0 , ω and f mesons. The slopes for p T 2 appear to be exponential and decrease with increasing particle mass for both annihilation and non-annihilation reactions, furthermore the slopes have consistently higher values for non-annihilation reactions. Comparisons with other data indicate that the ratio ϱ 0 / π − is independent of antiproton momentum in annihilation processes.
NON-ANNIHILATION EVENTS.
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The e + e − → p p cross section has been measured in the energy interval (1975 ⩽ 2 E ⩽ 2250) MeV for |cos θ | < 0.7. The measurement is based on ∼ 100 events, thus improving by a factor 3 on the previous existing statistics in this energy interval. The form factor | G | 2 is given as a function of energy under the assumption | G E | = | G M |. We also give the first measurement of the differential cross section, averaged over the energy interval, and estimate the ratio G M |/| G E | from it.
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ASSUMING ABS(GE)=ABS(GM).
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We report measurements of the two-photon processes e+e−→e+e−π+π− and e+e−→e+e−K+K−, at an e+e− center-of-mass energy of 29 GeV. In the π+π− data a high-statistics analysis of the f(1270) results in a γγ width Γ(γγ→f)=3.2±0.4 keV. The π+π− continuum below the f mass is well described by a QED Born approximation, whereas above the f mass it is consistent with a QCD-model calculation if a large contribution from the f is assumed. For the K+K− data we find agreement of the high-mass continuum with the QCD prediction; limits on f′(1520) and θ(1720) formation are presented.
Data read from graph. Additional overall systematic error 20% not included.
Data read from graph.. Additional overall systematic error 20% not included.
Data read from graph.. Additional overall systematic error 20% not included.. The Q**2 dependence is normalized to unity for the bin centred on Q**2 = 0.
Results are presented on the exclusive production of four-prong final states in photon-photon collisions from the TPC/Two-Gamma detector at the SLAC e+e− storage ring PEP. Measurement of dE/dx and momentum in the time-projection chamber (TPC) provides identification of the final states 2π+2π−, K+K−π+π−, and 2K+2K−. For two quasireal incident photons, both the 2π+2π− and K+K−π+π− cross sections show a steep rise from threshold to a peak value, followed by a decrease at higher mass. Cross sections for the production of the final states ρ0ρ0, ρ0π+π−, and φπ+π− are presented, together with upper limits for φρ0, φφ, and K*0K¯ *0. The ρ0ρ0 contribution dominates the four-pion cross section at low masses, but falls to nearly zero above 2 GeV. Such behavior is inconsistent with expectations from vector dominance but can be accommodated by four-quark resonance models or by t-channel factorization. Angular distributions for the part of the data dominated by ρ0ρ0 final states are consistent with the production of JP=2+ or 0+ resonances but also with isotropic (nonresonant) production. When one of the virtual photons has mass (mγ2=-Q2≠0), the four-pion cross section is still dominated by ρ0ρ0 at low final-state masses Wγγ and by 2π+2π− at higher mass. Further, the dependence of the cross section on Q2 becomes increasingly flat as Wγγ increases.
UNTAGGED DATA.
TAGGED DATA, RESULTS OBTAINED USING TRANSVERSE-TRANSVERSE LUMINOSITY ONLY. DATA FOR Q2=0 ARE FROM UNTAGGED SAMPLE, ERRORS DUE TO RELATIVE NORMALISATION OF THESE SAMPLES IS INCLUDED INTO ERRORS QUOTED.
UNTAGGED DATA.
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We have performed an experiment in the Antiproton Accumulator at Fermilab to study two-body neutral final states formed in p¯p annihilations. Differential cross sections are determined in the center-of-mass energy range 2.911<s<3.686 GeV for the final states π0π0, ηπ0, ηη, π0γ, and γγ. The energy dependence of differential cross sections at 90° in the center of mass is studied to test the predictions of phenomenological QCD scaling hypotheses which predict power-law dependence.
No description provided.
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The exclusive production of proton-antiproton pairs in the collisions of two quasi-real photons had been studied using data taken at sqrt(s)_ee=183 GeV and 189 GeV with the OPAL detector at LEP. Results are presented for Ppbar invariant masses, W, in the range 2.15 W< <3.95 GeV. The cross-section measurements are compared with previous data and with recent analytic calculations based on the quark-diquark model.
Cross section as a function of the invariant mass of the pbar-p pair.
Cross section for two photon production of the pbar-p pair.
Angular distributions in 3 W ranges.
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