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.
The analyzing power Ay for π+p→ scattering at 68.3 MeV has been measured at the Paul Scherrer Institut with the magnetic spectrometer LEPS. The measurements cover the angular range 40°≤θlab≤70°. The protons have been polarized in a butanol target, operated in frozen spin mode. The S31 phase shift comes out by about 1° smaller than the Koch-Pietarinen [Nucl. Phys. A 336, 331 (1980)] phase shift analysis, supporting the necessity of an alternative dispersion analysis of πN scattering to determine the σ term and the πN coupling constant. © 1996 The American Physical Society.
The two data sets correspond to measurements with two different target compositions (see text).
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A determination of branching ratios for D meson decays into all charged particle final states is reported. The values obtained: (D ± → K ∓ π ± π ± /all D ± ) = (14 ± 6)% and ( D 0 /D 0 → K ± π ∓ π + π − /all D 0 /D 0 ) = (10 ± 4)%, are higher than those currently accepted. This result, if confirmed, implies a corresponding reduction in the accepted values for some total cross section measurements. Revised inclusive cross sections for D meson production in the forward hemisphere in π − p and pp interactions at 360 GeV/ c , are presented.
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We have studied the reaction π − p → X − p followed by the decay X − → ωπ − at 11.2 GeV/ c . The partial-wave analysis in the mass range 1.36–2.0 GeV shows a clear structure in the J P = 3 − , m = 0 wave peaking at 1.67 GeV with a width of ∼0.21 GeV. We interpret this result as resulting from the g → ωπ decay. The differential cross section d σ d t is in agreement with the production of the g-meson through one-pion exchange.
FROM BREIT-WIGNER FIT TO <OMEGA PI-> MASS SPECTRUM. CORRECTED FOR OMEGA TAILS AND OTHER DECAY MODES. CROSS SECTION ORIGINALLY GIVEN IN R. GESSAROLI ET AL., NP B126, 382 (1977).
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Quasi-inclusive and total inclusive ϱ + , ϱ − and ϱ 0 cross sections have been studied, using data of a π + p and a pp bubble chamber experiment at 16 and 24 GeV/ c , respectively. In pp collisions it is found that the total inclusive cross sections for ϱ 0 , ϱ + and ϱ − production are about equal. This equality also holds for the differential cross sections d σ/ d y ∗ , all showing the characteristics of dominantly central production. In the π + p reactions the ϱ − are mainly produced centrally, whereas there are strong additional contributions in the beam fragmentation region for ϱ + and ϱ 0 mesons. In the central region, however, the cross sections for ϱ + , ϱ − and ϱ 0 production are almost equal within errors. All our findings agree with what is expected from quark model predictions.
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Results are given for the production differential cross sections and the ω decay angular distribution in terms of the ω spin density matrix elements.
PAPER ALSO GIVES OFF-DIAGONAL ELEMENTS OF THE ERROR COVARIANCE MATRIX.
PAPER ALSO GIVES OFF-DIAGONAL ELEMENTS OF THE ERROR COVARIANCE MATRIX.
Invariant single-particle cross sections for pion and proton production in π ± p interactions at 8 and 16 GeV/ c are presented in terms of integrated distributions as functions of x , reduced rapidity ζ and p ⊥ 2 , and also in terms of double differential cross sections E d 2 σ /(d x d p ⊥ 2 ) and d ζ d p ⊥ 2 ). A comparison of π ± and π − induced reactions is made and the energy dependence is discussed. It is shown that the single-particle structure function cannot be factorized in its dependece on transverse and longitudinal momentum. For the beam-unlike pion, there is an indication for factorizability in terms of rapidity and transverse momentum in a small central region.
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Theπ0 andη0 production is studied inπ−p interactions at 360 GeV/c. The cross section forπ0 production in the forward hemisphere (X>0) isσ(π0)=(49.7 ± 1.0 ± 1.1) mb and for η withX>0.1,Nch>2,σ(η0)=(3.1 ± 0.5) mb. The ratio of theπ0 toη0 cross section forX>0.1,Nch>2 isσ(π0)/σ(η0). Results on FeynmanX andpT distributions are presented. The data were obtained using the European Hybrid Spectrometer EHS and the bubble chamber LEBC at CERN.
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We report on a study ofρ0 andf2 inclusive production in π−−p interactions at 360 GeV/c, using the LEBC-EHS set-up at CERN and reconstructing about 165000 events. Theρ0,f2 andρ30 cross sections are determined forxF>0,xF>0.4 andxF>0.6 respectively and theρ0 andf2 Feynman-x distributions and transverse momentum distributions are presented.
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The first kinematically complete, good-statistics data for the (π,2π) reaction on the proton are presented. They involve double- and triple-differential cross sections as well as π+π− angular correlations. At energies around the Δ resonance, they exhibit a marked difference from phase space. The data are qualitatively described within the framework of an extension of Weinberg’s effective chiral Lagrangian.
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A search for production of D*−'s using the decay chain D0π−, D0→K+π−, was carried out at the Brookhaven National Laboratory multiparticle spectrometer with a 16-GeV/c π− beam and a hydrogen target. At 95% confidence level the upper limits for the product of peripheral production cross section by branching ratio are 2.4 nb for inclusive D*− production and 1.3 nb for the exclusive channel π−p→D*−Λc.
UPPER LIMIT TO CROSS SECTIONS.
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The ωπ − mass spectrum, in the reaction π −p → ωπ − pat 11.2 GeV/ c , shows the production of the B − meson with a cross section of 27 ± 5 μb as well as a clear enhancement around 1670 MeV. In the differential cross section for B − production, there is a strong forward peak and a change of slope at t ' t 0.2 GeV 2 .
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ABS(D-WAVE/S-WAVE) = 0.4 +- 0.1 FOR B DECAY.
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The angular distribution π+-p at 1.0 GeV was determined on the basis of l032 events measured in a propane bubble chamber. Comparison is made with data of 820 and 900 MeV and with angular distributions π−+p at similar energies.
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Production and decay properties of the B-meson are studied in the reactions π±p→B±p at 11 GeV/c. Values for mass, width, total and differential cross-sections and spin density matrix elements are given. The spin and parity, and the helicity states in the B→πω decay, are analysed.
BREIT-WIGNER FIT WITH 30 PCT BACKGROUND SUBTRACTED AND CORRECTED FOR UNSEEN OMEGA DECAYS.
FOR <OMEGA PION> EVENTS IN THE B REGION (1.16 TO 1.32 GEV) WITHOUT SUBTRACTING BACKGROUND.
ASSUMING B HAS SPIN-PARITY OF 1+.
The first data on the production of D ∗ (2010) are presented as observed in π − -proton interactions at √ s = 27 GeV . It is found that D ∗ (2010) dominates the total charm D-meson production, without a significant non-central component.
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We present the results of a search for charm F mesons in 360 GeV/ c π − p interactions. Several methods have been used; all yield no evidence for the F and are interpreted as 90% confidence level cross section upper limits.
D/S+- lifetime was assumed tau = 3.2*10**-13 s.
D/S+- lifetime was assumed tau = 3.2*10**-13 s.
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The inclusive reactions h+p→ φ +X, (h= π ±, ,K ± ,p ± ), are studied for 0⪅ x F ⪅0.3 and p ⊥ ⩽ 1 GeV at 93 and and 63 GeV incident momentum. Differential cross sections d σ /d p ⊥ 2 and dσ /d x F are presented and are compared with predictions of the naive parton model.
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The inclusive production of vector mesons (charged ρ(770), ω(783), ϕ(1020) and neutralK*(892)) in π−p interactions at 360 GeV/c is studied. The data are based on 160 000 reconstructed events recorded in the NA 27 Experiment using the LEBC-EHS facility at CERN. The production cross sections in the forward hemisphere in c.m.s. and the longitudinal momentum distributions are determined. The results are compared with data obtained at lower energies.
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Upper limits of cross sections.
Cross sections extrapolated to x > 0.
Charm-charm correlation properties are studied in detail for the first time using a sample of D D pairs produced in 360 GeV/ c π − p interactions. The data are compared with various models of charm production.
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