Neutral Strange Particle Production Research Articles

Large angle Λ° production in exclusive reactions between 3 and 12 GeV/c

The analysis of exclusive neutral strange particle production in the reactions π −p → K° Λ + K° Σ° and pp → ΛΛ + ΛΣ° + c.c. at 3.15, 4.95, 7.9 and 12 GeV/ c yielded the differential cross section distributions up to about 90° c.m.s. scattering angle and the Λ-particle polarization at large transverse momentum. Applying a fit to d σ/d t ∞ s − n resulted in n = 8.6 ± 0.9 for the K° Λ + K° Σ° final state which is compatible with the quark counting rule n = 8 for meson-baryon reactions. The average Λ polarization around t = −1.6 (GeV/ c) 2 was P Λ = 0.79 ± 0.17 at 3.15 GeV/ c beam energy.

Inclusive production of neutral strange particles in $$\bar pp$$ interactions at 70 GeV/c

The inclusive production of K s 0, Λ and {Mathematical expression} particles is investigated in 70 GeV/c {Mathematical expression} interactions in an experiment performed at CERN using BEBC equipped with a TST. Differential cross-sections are studied and compared with corresponding data at surrounding energies. Differences with pp data obtained at the same energy allow an estimate of the K s 0, production cross-section in annihilation processes. Evidence is also given for central {Mathematical expression} production. © 1984 Springer-Verlag.

Neutral strange particle production in antineutrino-induced neutral current interactions

The study of neutral strange particle production in antineutrino-induced neutral current interactions is presented. The total multiplicity of neutral strange particles and the K 0 multiplicity in the current fragmentation region ( z>0.3) are used to estimate in two ways the coupling strength of the weak neutral current to the strange quark.

Production of neutral strange particles in [formula omitted] and νμd2 charged current interactions

The inclusive production of K 0, Λ and Λ in charged-current (anti) nuetrino interaction in deuterium is studied, using the BEBC bubble chamber exposed to the CERN-SPS wide band (anti) neutrino beam. In a selected sample of 8600 charged current ν μ d 2 and 6100 ν μd 2 interactions, 700 K 0, 448 Λ and 20 Λ particles were observed. The interactions have been separated in interactions on neutrons and on protons. The production properties are studied in terms of various kinematical variables. The associated production of strange particles, the production of K ∗±(890) and of Σ ±(1385) and the inclusive Λ polarization are discussed. The experimental results are compared with the predictions of the Field-Feynman and the Lund fragmentation models.

Inclusive neutral strange particle production in νp interactions

In a selected sample of 6770 charged current (CC) events of νp interactions with 〈 E ν 〉 = 43 GeV and 〈W〉 = 4.6 GeV, 359 K 0, 180 Λ and 13 Λ have been observed, which corresponds to a corrected production rate at least one neutral strange particle in (17.4±0.8)% of the CC events. The ratio of the inclusive Λ to K 0 production cross section is found to be 0.26±0.03. The number of CC events containing at least one K 0 increases with increasing E ν and Q 2, while the CC events containing at least one Λ remain practically constant. The fractions of the total hadronic energy carried by K 0 and Λ are found to be approximately the same in νp as in ep and μp interactions. In the hadronic c.m.s., the K 0 are produced mostly forwards, the Λ mostly backwards, with asymmetry parameters of +0.32±0.02 and −0.45±0.06, respectively. The total strange particle production cross section is estimated to be (25±4)% of the cross section for production of CC events with W>1.5 GeV and that for charm production (10±2)% of the CC cross section well above charm threshold ( W>3 GeV). The production of the resonances K ∗+ (890) and Σ + (1385) has been observed. The production rate of K ∗+ (890) is comparable to that of D ∗+ (2009), above the corresponding thresholds.

Neutral strange particle production in proton-proton collisions at $$\sqrt s = 63$$ GeV

The inclusive cross section for the production ofK 0 mesons, Λ and $$\bar \Lambda$$ particles in proton-proton interactions at $$\sqrt s = 63$$ GeV is presented. The produced particles have been detected in the full phase space. Behaviour of the longitudinal and transversal depandences of the cross sections are discussed. The total production cross sections for 0 mesons and Λ particles was determined to $$\sigma _{{\rm K}_S^0 } = (25.5 \pm 1.4)$$ mb andσ Λ =(7.8±1.2) mb respectively. A strong energy dependence of the production cross sections is observed.

Inclusive production of neutral strange particles in $$\bar pp$$ interactions at 32 GeV/c

The inclusiveKn, ¶,and\(\bar \Lambda\) production has been studied in a\(\bar pp\) experiment performed in the Mirabelle bubble chamber at an incident beam momentum of 32.1 GeV/c. Total, topological and differential cross sections are presented and compared with those obtained at other energies. The invariant structure functions have been parametrised in the fragmentation region by a power law and are consistent with the expectations based on quark counting rules.

Inclusive production of neutral strange particles by 147 GeV/ cπ+/K +/p interactions in hydrogen

Results are presented from a study of inclusive neutral strange particle production by a 147 GeV/ c tagged π +/K +/p beam in the Fermilab 30-inch hydrogen bubble chamber. The experiment made use of the proportional hybrid spectrometer system. Results are based on 995 K S 0, 485 Λ, and 83 Λ found in a sample of 132 000 pictures. Cross sections are given for inclusive production of these particles by each of the three beam particles, and comparisons are made with measurements at other energies. Topological cross sections are also calculated, and KNO multiplicity scaling is investigated. Distributions are presented of invariant cross sections as functions of the Feynman scaling variable x and c.m. rapidity y. The transverse momentum-squared distributions with their fitted slopes are also given. Comparisons are made of the production characteristics for the three beam types.

Neutral strange particle production in π−p interactions at 16 GeV/ c

The production of K S 0, Λ and Λ in π − p ractions at 16 GeV/ c is investigated. Cross sections for single strange particles are determined, both inclusively and as functions of the charged multiplicity. Some characteristics of the multiplicity distributions are also discussed. Inclusive distributions are studied as a function of the longitudinal and transverse variables of V 0 and the missing mass squared. The average charged multiplicities of the systems recoiling against the Λ and K S 0 are presented.

Production of strange particles in antineutrino interactions at the CERN PS

We have studied neutral strange particle production in the bubble chamber Gargamelle filled with propane and exposed to antineutrinos from the CERN PS. Cross sections are presented for Λ, Σ 0 and K 0 production. Associated production reactions ( ΔS = 0) have been observed in the charged and the neutral current channels. From 45 candidates for the quasi-elastic reaction ν p → μ +Λ , on bound and free protons, estimates of the axial transition form factor M A have been made using the total cross section and the t distribution. The weighted average from the two methods is M A = 862 ± 190 MeV. From a subsample of 15 candidates for ν interactions on free protons in propane, with (28±6)% background from ν interactions on bound protons, we obtain M A = 883 ± 243 MeV. The polarization of the Λ hyperons has been studied for the quasi-elastic reaction. We observe a significant Λ polarization in the production plane, normal to the Λ line of flight. The observed polarizations agree well with the predicted theoretical polarizations without any contribution from second-class axial coupling.

General features of [formula omitted] interactions at 32 GeV/ c

The general features of p p interactions at 32 GeV/ c are analysed in a bubble chamber experiment with a statistics of 5.2 μb/event. The inclusive production of neutral strange particles and pions is analysed and compared to results obtained at other energies and in pp interactions. Total cross sections are determined for various 4C reactions and the relative contributions of diffractive dissociation and ΔΔ production to the reaction p p→ p pπ +π − are estimated.

Inclusive production of neutral strange particles at 300 GeV: Triple-Regge behavior

The process p + nucleon → V 0+ anything has been studied at 300 GeV for V 0 = Λ 0, Λ 0 , and K S 0. The data are consistent with a simple Mueller-Regge formulation in the appropriate limit. Values of α( t) computed from the data agree with those expected from the simplest triple-Regge diagrams. If the pomeron is not a pure SU(3) singlet, a similar diagram is consistent with the Feynman x-dependence of the observed polarization of inclusively produced Λ 0.

Neutral strange particle production in pp interactions at 69 GeV/ c

From a study of 1226 neutral strange particles produced in pp interactions at 69 GeV/ c in the MIRABELLE hydrogen bubble chamber, we obtain the inclusive cross sections for K S 0, Λ/ Σ 0, Λ/ Σ 0 equal to 3.43 ± 0.23, 3.44 ± 0.2 and 0.16 ± 0.03 mb, respectively. The inclusive distributions are compared with corresponding data at other energies.

The use of approximately normal distribution to describe the production of neutral particles

The normal distribution in two variables is used in an approximate form to describe the data on the reactions pp, pi -p or pi -n to (j negatively charged particles)+(neutral pions). It is shown that the model predicts a linear relationship between j and the mean number of neutrals. Modifications of the model are proposed in order to incorporate specific isospin conserving mechanisms. Comparisons are made with the work of other authors. Neutral strange particle production is discussed.

Neutral strange-particle production in pp collisions at 6.92 GeV/c

Neutral strange particle production in pp collisions at 6.92 GeV/c has been studied in the 80 in. HBC at BNL. Partial crosssections for the different channels are given. No evidence for hyperon-nucleon resonances has been observed. Strong production ofN 3/2 * (1236) and Y 1 * (1385) has been seen in the four- and five-body final states, which has been analysed in terms of a one-pion-exchange mechanism.

Proton-Proton Interactions at 5.5 GeV/c

This report is based on about 10 500 $\mathrm{pp}$ collision events produced in the 81-cm Saclay hydrogen bubble chamber at CERN. Cross-section values for the different identified final states and resonances are given. The isobars ${{N}^{*}}_{1238}$, ${{N}^{*}}_{1420}$, ${{N}^{*}}_{1518}$, ${{N}^{*}}_{1688}$, ${{N}^{*}}_{1920}$, and ${{N}^{*}}_{2360}$ were identified and their production cross-section values were found via a best-fit analysis of different invariant-mass histograms. About 70% of the isobars are connected with the quasi-two-body reactions $\mathrm{pp}\ensuremath{\rightarrow}{N}^{*}N$ and $\mathrm{pp}\ensuremath{\rightarrow}{N}^{*}{N}^{*}$. The reaction $\mathrm{pp}\ensuremath{\rightarrow}n{{N}^{*}}_{1238}(p{\ensuremath{\pi}}^{+})$ with a cross section of 3.25\ifmmode\pm\else\textpm\fi{}0.16 mb was analyzed in terms of a peripheral absorption model, which was found to be in good agreement with the data. Various decay modes of the ${{N}^{*}}_{1518}$ and ${{N}^{*}}_{1688}$ isobars were observed and their branching ratios determined. The branching ratio of $n{\ensuremath{\pi}}^{+}$ to $p{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ was found to be 0.77\ifmmode\pm\else\textpm\fi{}0.45 for ${{N}^{*}}_{1518}$ and 0.67\ifmmode\pm\else\textpm\fi{}0.40 for ${{N}^{*}}_{1688}$. The branching ratio of ${{N}^{*}}_{1238}(p{\ensuremath{\pi}}^{+}){\ensuremath{\pi}}^{\ensuremath{-}}$ to $p{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ of ${{N}^{*}}_{1688}$ was estimated to be 0.74\ifmmode\pm\else\textpm\fi{}0.14. Pion production turned out to be mainly due to decay of isobars. Production of meson resonances turned out to be less important; the reaction $\mathrm{pp}\ensuremath{\rightarrow}\mathrm{pp}{\ensuremath{\omega}}^{0}\ensuremath{\rightarrow}\mathrm{pp}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ was identified with a cross-section value of 0.11\ifmmode\pm\else\textpm\fi{}0.02 mb. Finally, the production of neutral strange particles with a cross section of 0.45\ifmmode\pm\else\textpm\fi{}0.04 mb is descussed. Strong formation of ${{Y}^{*}}_{1385}$ is observed.