Inclusive strange particle production in π−p interactions at 6 GeV/c

The inclusive production of Λ, K_S⁰, Σ^±(1385) and $\text{K}{}^{\mathrm{1\pm }}\text{(892)}$ in π^?p interactions at 6 GeV/c has been studied. The observed cross sections are: σ(Λ)=0.94±0.06 mb, σ(K_S⁰)=0.98±0.06 mb, σ(Σ⁺(1385))=60±7 μb, σ(Σ^?(1385))=90±9 μb, $\text{σ(}\text{K}{}^{\mathrm{1+}}\text{(892))=216±28 μ}\text{b and}\text{σ(}\text{K}{}^{\mathrm{1?}}\text{(892))=41±8 μ}\text{b}$, respectively. The inclusive spectra of these particles are presented as functions of squared transverse momentum and Feynman scaling variable x. The polarization of Λ has also been investigated. It is found from a comparison with higher-energy data that the inclusive cross sections for Σ^±(1385) and the production ratios Σ^±(1385)/Λ in π^?p at 6 GeV/c have not reached the high-energy limiting values.     

Strange particle production from π−p interactions at 1.69 GeV/c

The three-body final states $\text{Σ}{}^{\mathrm{\pm }}\text{π}{}^{\mathrm{?}}\text{K}{}^0\text{, Σ}{}^{\mathrm{<mtext>0</mtext>}}\text{π}{}^{\mathrm{<mtext>0</mtext>}}\text{K}{}^{\mathrm{+}}$ and $\text{Λπ}{}^{\mathrm{<mtext>0</mtext>}}\text{K}{}^{\mathrm{+0}}$ produced from πp interactions at 1.69 GeV/c are examined. The quasi-two-body state Λ(1405)K⁰ is discussed in detail. In particular, the spin of Λ(1405) is determined, via the method of Byers and Fenster, to be consistent with $\text{1}\text{2}$. The Σ^±π^? mass spectrum is compared to that produced by various zero-range and effective-range parametrizations and the Λ(1405) is found to have a mass of 1405 MeV and width of 45–55 MeV. Production and decay characteristics of the quasi-two-body states $\text{Σ(1385)}{}^{\mathrm{<mtext>0</mtext>}}\text{K}{}^{\mathrm{<mtext>0</mtext>}}$ are reported.     

Inclusive production of Ξ+ and Ξ− in K+ p interactions at 32 GeV/c

The inclusive production of $\text{Ξ}{}^{\mathrm{+}}$ and Ξ^? hyperons is investigated in K⁺ p interactions at 32 GeV/c. The production cross sections, 36.4±9 μb for the $\text{Ξ}{}^{\mathrm{+}}$ and 6.5±3 μb for the Ξ^?, are rising strongly with energy similarly to $\text{Λ}$ and Λ production in K⁺ p interactions. The $\text{Ξ}{}^{\mathrm{+}}$ are produced preferentially in the forward direction in the c.m.s., while the Ξ^? are produced dominantly backwards. The average transverse momenta and 〈p_T〉_Ξ^?=0.58±0.09 GeV/c.     

Peripheral behaviour of pp → K1±K∓ between 1 and 2.5 GeV/c

The reaction $\text{p}\text{p}\text{→}\text{K}{}^1\text{K}$ does not exhibit any s-channel resonance effect between 1 and 2.5 GeV/c. On the contrary, the data on $\text{p}\text{p}\text{→}\text{K}{}^{\mathrm{1?}}\text{K}{}^{\mathrm{\pm }}$ are compatible with an exchange mechanism in the t- and u-channels above 1.5 GeV/c. Strong similarities are found with $\text{p}\text{p}\text{→}\text{K}{}^{\mathrm{?}}\text{K}{}^{\mathrm{+}}\text{and}\text{K}{}^{\mathrm{1?}}\text{K}{}^{\mathrm{1+}}$. The polarisation of K^1± is given. The reaction $\text{p}\text{p}\text{→}\text{K}{}^{10}\text{K}{}^0$ vanishes above 1.5 GeV/c     

A study of the reactions π−p → K1X, K1Σ and K1Y11(1385) at 3.93 GeV/c

We have investigated the final states K¹⁰(890)Σ, $\text{K}{}^{10}\text{(890)Σ}{}^0$ and K¹⁰(890) Y₁¹⁰(1385) produced in π^?p interactions at 3.93 GeV/c. We present the differential cross sections and spin density matrix elements for the resonances as functions of momentum transfer, as well as the gL and Σ⁰ polarizations. The Σ⁰ polarization is found to be positive and maximal. An amplitude analysis is performed for the K¹ Λ and $\text{K}{}^1\text{Σ}{}^0$ reactions, and it is found that one natural parity transversity amplitude is dominant for the latter.     

Evidence for a narrow peak in Ksoπ±π+π- at 2.6 gev in 12 gev/cpp interactions

We report the evidence for a narrow charged peak (5.5 s.d.), which we suggest calling the I, in the 6-prong-V⁰ topology of $\text{p}$p interactions at 12 GeV/c. The mass, widht and the product of cross section σ_I times the branching ratio BR into the final state (K_s^oτ±τ⁺τ^? are found to be: $\text{M}{}_{\mathrm{I}}\text{=2.60 ±}\text{0.01}\text{GeV}\text{/}\text{c}{}^2$, $\text{Γ}{}_{\mathrm{I}}\text{?}\text{0.018}\text{GeV}\text{/}\text{c}{}^2$, σ_I·BR≈20 μbarn     

Experimental results on J/ψ production by π±, K±, p and p incident on hydrogen at 39.5 GeV/c

J/ψ production at 40 GeV/c by π^±, K^±, p and $\text{p}$ incident on hydrogen has been studied and results compared with those obtained on tungsten in the same experiment. On hydrogen, J/ψ cross-section ratios relative to π^? have been measured to be (for $\text{x}{}_{\mathrm{<mtext>F</mtext>}}\text{> 0) σ(π}{}^{\mathrm{?}}\text{) : σ(π}{}^{\mathrm{+}}\text{) : σ(}\text{p}\text{) : σ(}\text{p}\text{) = 1 : (0.78 ± 0.09) : (0.83 ± 0.35) : (0.07 ± 0.04)}$. The suppression of the proton induced cross sections shows the importance of calence quark-antiquark fusiin J/ψ production at this energy (i.e. M_J²/_ψ/s=0.13).     

Inclusive K1±(892) production in pp and π+p interactions

A study is presented of the inclusive production cross sections of K^1±(892) vector mesons in pp interactions at 12 and 24 GeV/c and in π⁺p interactions at 16 GeV/c. The K^1± inclusive cross section is ～0.9 mb for both pp at 24 GeV/c and π⁺p interactions at 16 GeV/c. For pp interactions, $\text{σ(}\text{K}{}^{\mathrm{1+}}\text{)}$ and $\text{σ(}\text{K}{}^{\mathrm{1?}}\text{)}$ are seen to rise with energy, showing a threshold behaviour. In both pp and π⁺p interactions, $\text{σ(}\text{K}{}^{\mathrm{1+}}\text{)}$ largely exceeds $\text{σ(}\text{K}{}^{\mathrm{1?}}\text{)}$ at these energies and this excess is interpreted as K¹⁺ production by beam and target fragmentations. The decays of K^1±0 yield ～30% of the K⁰ observed in the final states. The p_T² dependence of both K¹⁺ and K^1? cross sections is described by an exponential with slope of ～3.3 (GeV/c)^?2. The longitudinal momentum spectra for K¹⁺ in 16 GeV/cπ⁺p and 24 GeV/c pp interactions are similar in shape in the target hemisphere. The K^1? spectra are similar over the whole kinematic region when viewed in the quark c.m.s. and point to a central production mechanism. Comparing K¹⁺ and ρ⁰ production, striking similarities are found.     

Four-pion final state in pp annihilations at 0.7 to 1.1 GeV/c

Results are reported on the reaction $\text{p}\text{p}\text{→ π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{?}}$ at six lab momenta spanning the region from 0.686 to 1.098 GeV/c. The cross section for this process drops from 5.2 ± 0.4 mb at 0.686 GeV/c to 2.9 ± 0.2 mb at 1.098 GeV/c. Resonance production is determined by means of a model which includes Bose symmetrization and Breit-Wigner amplitudes. The likelihood fit to the resonance channels yields a few per cent ?ππ, approximately 10% in each of the channels fππ, ??, and A₂π, and about 40% ?f production, with errors on the order of 5%. Excellent fits to the mass distributions are obtained. Essentially all production and decay angular distributions are found to be uniform, with only a few small deviations from isotropy reported. The angular correlations between like and unlike charged pion pairs are also found to be fit extremely well by the simple model of resonance production with Bose symmetrization.     

Strange particle cross sections and multiplicity distributions in 19 GeV/c proton-proton interactions

Inclusive cross sections are presented for strange-particle production in proton-proton interactions at 19 GeV/c for the pairs $\text{(}\text{K}{}^0\text{K}{}^0{}_{\mathrm{C=+1}}\text{,}\text{K}{}^0\text{Λ,}\text{K}{}^{\mathrm{+}}\text{Λ,}\text{K}{}^0\text{Σ}{}^{\mathrm{+}}\text{,}\text{K}{}^0\text{Σ}{}^{\mathrm{?}}$ and for Λ, K_s⁰, Σ⁺, Σ^? and Ξ^?. The $\text{K}\text{K}$, the KY and the total strange particle cross sections have been found to be 1.40 ± 0.10 mb, 2.69 ± 0.09 mb and 4.23 ± 0.20 mb, respectively. The charged multiplicity distributions for events with K_s⁰, Λ, $\text{(}\text{K}{}^0\text{K}{}^0\text{)}{}_{\mathrm{C=+1}}$ or K⁰ Λ are shown to follow a modified KNO curve, whereas K⁺ Λ does not. For the inclusive reactions $\text{pp}\text{→(}\text{K}{}^0\text{K}{}^0\text{)}{}_{\mathrm{C=+1}}\text{+}\text{X}{}^{\mathrm{++}}\text{,}\text{pp}\text{→}\text{K}{}^0\text{Λ +}\text{X}{}^{\mathrm{++}}\text{and pp}\text{→ Λ +}\text{X}{}^{\mathrm{++}}$, we find that the average charged multiplicity of the remainder system X⁺⁺ is the same as when X⁺⁺ is produced in other reactions with the same system energy and quantum numbers.     

Hyperon-antihyperon production in pp interactions at 3.6 GeV/c leading to ⩾3 particles in the final state

Results are presented on the properties of the $\text{p}$p interactions at 3.6 GeV/c leading to a hyperon or an antihyperon in final states with ?3 particles from an experiment of 35 eV/μb sensitivity. Results of amultidimensional mass fit to each final state are given along with the cross sections, differential cross sections and polarization, where possible, for the hypercharge exchange reactions $\text{p}\text{p}\text{→}\text{Λ}\text{Y}{}^1\text{(1385),}\text{Λ}\text{Y}{}^1\text{(1520),}\text{Σ}\text{Y}{}^1\text{(1385)}\text{and}\text{Σ}\text{Y}{}^1\text{(1520)}$.     

An isospin analysis of the reaction pN→NNπ from threshold to 2.90 GeV/c

We have performed an isospin analysis of single-pion production processes in antiproton-nucleon scattering from threshold to 2.90 GeV/c. Reactions used are $\text{p}\text{p}\text{→}\text{p}\text{p}\text{π}{}^0\text{,}\text{n}\text{p}\text{π}{}^{\mathrm{?}}\text{and}\text{p}\text{p}\text{→}\text{p}\text{p}\text{π}{}^{\mathrm{?}}$. Results show that σ₁, the total I=1 cross section, rises rapidly from threshold to reach a broad maximum around 2.5 GeV/c and σ₀, the I=0 cross section, rises from threshold and continues on a linearly rising trend at least up to 2.90 GeV/c. In the region of 2.9 GeV/c, σ₁ and σ₀ have comparable values, thus suggesting that considerable amount of $\text{I=}\text{1}\text{2}\text{N}\text{π}$ and $\text{N}\text{π}$ states is produced even in this low momentum region. We further determine that single pion production processes are not the source of the π₀ (2375,190) enhancement observed in the $\text{p}\text{p}$ and $\text{p}\text{d}$ total cross sections and may account for as much as 25±8% of the π₁ (2350,140) enhancement.     

Evidence for new meson resonances from the reaction pp → K−K+

The differential cross sections for $\text{p}\text{p}\text{→}\text{K}{}^{\mathrm{?}}\text{K}{}^{\mathrm{+}}$ provide new evidence for mesons with masses between 2.1 and 2.5 GeV/c². The zeros of the cross sections suggest the existence of J^P = 3^? states with both I = 1 and I = 0 at masses between 2.1 and 2.18 GeV/c². The results also support a J^P = 4⁺ state near 2.34 GeV and are consistent with 5^? states in both I = 1 and I = 0 close to 2.5 GeV. This analysis confirms the I = 1 3^?, 5^? and I = 0 4⁺ states seen previously in $\text{p}\text{p}\text{→ π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ and is in agreement with the existing data for the non-annihilation processes.     

Λ and Λ production in K+p interactions at 32 GeV/c

A study of the inclusive and semi-inclusive Λ and $\text{Λ}$ production in K⁺p interactions at 32 GeV/c is presented. The inclusive cross sections for Λ and $\text{Λ}$ amount to 0.78 ± 0.05 and 0.42 ± 0.04 mb thus showing a remarkable growth between 16 and 32 GeV/c with a factor of 1.7 for Λ and 2.8 for $\text{Λ}$. Target and beam fragmentation processes are found to be dominant for Λ and $\text{Λ}$ production respectively with the following lower limits for the corresponding cross sections: $\text{σ(p}\text{→}\text{K}{}^{\mathrm{+}}\text{?) > 0.5}\text{mb}$ and $\text{σ(K}{}^{\mathrm{+}}\text{→}\text{p}\text{?}\text{) > 0.3}\text{mb}$. Although the early scaling conditions are fulfilled for the Λ production in the target fragmentation region, and $\text{Λ}$ production in the beam fragmentation region, scaling is not observed between 16 and 32 GeV/c in the x and p_T² Feynman variables. The Λ production is found to be very similar in the K⁺p inclusive reaction at 32 GeV/c and in the semi-inclusive reaction $\text{K}{}^{\mathrm{?}}\text{p}\text{→ Λ}\text{K}\text{K}\text{X}$ at the same energy. The $\text{Λ}\text{Λ}$ pair production cross section increases significantly in K⁺p interactions from 16 to 32 GeV/c where it reaches the value $\text{σ}{}_{\mathrm{<mtext>\Lambda </mtext><mtext>\Lambda </mtext>}}\text{= 47 ± 11 μ}\text{b}$. The cross sections for Λ or $\text{Λ}$ produced in association with an identified proton are also given and discussed.     

The ϱ and A2 exchange amplitudes in meson-baryon scattering for ϱlab between 2.5 and 200 GeV/c

We present a parametrization of the ? and A₂ exchange amplitudes which fits all the available data on the reactions $\text{π}{}^{\mathrm{?}}\text{p}\text{→ π}{}^0\text{n}\text{, π}{}^{\mathrm{?}}\text{p}\text{→}\text{K}{}^0\text{n}\text{,}\text{and K}{}^{\mathrm{+}}\text{n}\text{→}\text{K}{}^0\text{p}$ in the momentum range from 2.5 to 200 GeV/c and for momentum transfers up to t = ?2.0 (GeV/c)².     

Five-pion final state in pp annihilations at 0.70 to 1.1 GeV/c

Results are reported on the reaction $\text{p}\text{p}\text{→ π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{?}}\text{π}{}^0$ at six lab momenta spanning the region from 0.686 to 1.098 GeV/c. The cross section for this process drops from 20.3 ± 1.2 mb at 0.686 GeV/c to 13 1.0 mb at 1.098 GeV/c. Resonance production is determined by means of a model which includes Bose symmetrization, Breit-Wigner amplitudes and Bose-Einstein correlations for the like-charged pion pairs in the nonresonant part of the amplitude. The likelihood fit to the resonance channels yields about 0.8% ηππ, 12% ?^±πππ, 2% fπππ, 8% ωππ, 22% ?^±?⁰π, 13% ω?⁰ and 9% ωf with errors on the order of a few percent. Several percent A₁^±ππ and X(1440)π were also needed to obtain good fits. The ?⁰πππ and ?⁰?⁰π channels as well as A₂ππ and A₁⁰ππ are consistent with zero. Reasonable fits to the mass distributions are obtained. Production angular distributions are found to be essentially uniform. The angular correlations between pion pairs are approximately fit by the simple model of resonance production with Bose symmetrization.     

Λ and K0 production in p↑p interactions at 6 GeV/c

Results on K⁰ and Λ production in p↑p interactions at 6 GeV are presented. The data are from an exposure of the Argonne 12 ft bubble chamber to a 60% transversely polarized proton beam. Results include data on Λ and K⁰ inclusive production, and on the reactions p↑p → pΛK⁺(pΣ⁰K⁺). The beam asymmetry parameter for $\text{p}\text{↑}\text{p}\text{→}\text{K}{}^0\text{(}\text{K}{}^0\text{) +}\text{X}$ is determined to be (?0.52 ± 0.12).     

Elastic scattering of π±p, K±p,pp ANDprmpp AT 39 AND 44.5 GeV/c

The differential cross sections for elastic $\text{π}{}^{\mathrm{?}}\text{p, K}{}^{\mathrm{?}}\text{p}\text{,}\text{p}\text{p and}\text{π}{}^{\mathrm{+}}\text{p, pp}$ scattering at 39 and 44.5 GeV/c, respectively, have been measured in the interval of momentum transfer squared 0.15 ≤ ovbt| ≤ 2 (GeV/c)².     

Inclusive η production at high pT at the ISR

The inclusive η production cross section at the CERN ISR has been measured for p_T values of up to 11 GeV/c. We find that the $\text{η}\text{π}{}^0$ cross-section ratio has an average value of 0.55 ± 0.07 and varies little with p_T.