Fermilab 15-ft Bubble Chamber Research Articles

Inclusive production of nonstrange resonances in high-energyνpcharged-current interactions

We have examined the inclusive production of nonstrange particle resonances in ..nu..p interactions using the Fermilab 15-ft bubble chamber. A sample of 2437 charged-current events with visible longitudinal momentum greater than 10 GeV/c was obtained. The rho/sup 0/ and ..delta../sup + +/(1232) are seen. An overall rate of 0.21 +- 0.04 rho/sup 0/ per event is found. For five-prong events, the rate is 0.44 +- 0.08 rho/sup 0/ per event. The rho/sup 0/ Z distribution falls rapidly for Z greater than 0.4. The production of ..delta../sup + +/ is seen clearly in events with an identified proton. No evidence is seen for ..delta../sup 0/ production. An upper limit of 0.34 is placed on the ratio of eta/..pi../sup 0/ (90% confidence level).

Charged- and neutral-particle production from 400-GeV/cppcollisions

Charged- and neutral-particle production from 400-GeV/c $\mathrm{pp}$ collisions are measured simultaneously using the Fermilab 15-ft bubble chamber. The ${\ensuremath{\pi}}^{0}$ and ${K}^{0}$ cross sections are rising at Fermilab energies, while the ${\ensuremath{\Lambda}}^{0}$ cross section remains fairly constant. Similarly, the average number of ${\ensuremath{\pi}}^{0}$'s and ${K}^{0}$'s increases as a function of the number of negative particles in an event, yet no such dependence is noted for the ${\ensuremath{\Lambda}}^{0}$'s. The ratio of average number of ${\ensuremath{\pi}}^{0}$ to average number of ${\ensuremath{\pi}}^{\ensuremath{-}}$ per inelastic collisions is found to be constant at Serpukhov and Fermilab energies (40 to 400 GeV/c) and equal to 1.22\ifmmode\pm\else\textpm\fi{}0.02. Cross sections for ${\ensuremath{\Sigma}}^{0}$ and ${\overline{\ensuremath{\Sigma}}}^{0}$ production are measured and limits are found for ${\ensuremath{\eta}}^{0}$ and ${\ensuremath{\omega}}^{0}$ production. Neutral- and charged-pion correlations are compared with five pion-production models.

Confirmation of the Existence of theΣc++andΛc+Charmed Baryons and Observation of the DecayΛc+→Λπ+andK¯0p

In a broadband neutrino exposure of the Fermilab 15-ft bubble chamber, we observe the production of the ${{\ensuremath{\Sigma}}_{c}}^{++}(2426)$ charmed baryon followed by its decay to ${{\ensuremath{\Lambda}}_{c}}^{+}(2260)$ and ${\ensuremath{\pi}}^{+}$. We find the mass of the ${{\ensuremath{\Lambda}}_{c}}^{+}$ to be 2257\ifmmode\pm\else\textpm\fi{}10 MeV and the $m({{\ensuremath{\Sigma}}_{c}}^{++})\ensuremath{-}m({{\ensuremath{\Lambda}}_{c}}^{+})$ mass difference to be 168\ifmmode\pm\else\textpm\fi{}3 MeV. Previously unseen two-body decay modes of the ${{\ensuremath{\Lambda}}_{c}}^{+}(2260)$ are observed.

Correlations between neutral and charged pions produced in 300-GeV/cppcollisions

Neutral-pion production in $\mathrm{pp}$ interactions has been studied using 8000 photon conversions in the Fermilab 15-ft bubble chamber. Inclusive ${\ensuremath{\pi}}^{0}$ multiplicity moments and $\ensuremath{\pi}\ensuremath{\pi}$ correlation integrals are presented; ${f}_{2}^{00}$ is determined to be + 3.0\ifmmode\pm\else\textpm\fi{}0.8. For the semi-inclusive ${\ensuremath{\pi}}^{0}$ multiplicity distributions we find ${〈n({\ensuremath{\pi}}^{0})〉}_{n\ensuremath{-}}$ to increase with ${n}_{\ensuremath{-}}$, while the dispersions are ${n}_{\ensuremath{-}}$ independent. Results on ${f}_{2}^{\ensuremath{-}0}$, ${f}_{2}^{00}$, and ${f}_{2,n\ensuremath{-}}^{00}$ are compared to predictions of simple cluster models.

Inclusive production of neutral strange particles in 250-GeV/cπ−pinteractions

Neutral-strange-particle production has been studied in a 46000-picture exposure in the Fermilab 15-ft bubble chamber. Cross sections for inclusive production of ${K}_{s}^{0}$, $\ensuremath{\Lambda}$, and $\overline{\ensuremath{\Lambda}}$ are given and compared with data at lower energies. The ${K}_{s}^{0}$'s are produced principally in the central region of rapidity with a cross section which increases with energy. The $\ensuremath{\Lambda}$'s are produced principally by proton fragmentation, whereas the $\overline{\ensuremath{\Lambda}}$'s are centrally produced. Correlations of ${K}_{s}^{0}{\ensuremath{\pi}}^{+}$ and ${K}_{s}^{0}{K}_{s}^{0}$ are shown to be different from those for ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$.

Ratio of Neutral-Current to Charged-Current Cross Sections for Inclusive Neutrino Interactions in Hydrogen

The ratio of neutral-current to charged-current cross sections is determined from a sample of events obtained in an exposure of the Fermilab 15-ft hydrogen bubble chamber to a high-energy, horn-focused neutrino beam. For events with three or more prongs and with visible hadron momentum above 10 GeV/c, the ratio is 0.40 ± 0.14. A Monte Carlo calculation assuming the Weinberg-Salam model is used to correct for excluded events, yielding RNCCC=0.48±0.17.Received 10 June 1977DOI:https://doi.org/10.1103/PhysRevLett.39.437©1977 American Physical Society

Scaling-Variable Distributions for Antineutrino-Nucleon Interactions

New data are reported on high-energy antineutrino interactions obtained using the Fermilab 15-ft bubble chamber filled with a light neon-hydrogen mixture. The new data support a gentle energy dependence for the $y$ distribution consistent with the trend of the existing data, but show no evidence for a marked energy threshold. The data for $〈x〉$ and $〈v〉=〈\mathrm{xy}〉$ show some decrease with increasing energy which may be related to scaling deviations measured in electron and muon experiments.

K0Phenomena Associated with Neutrino-Inducedμ−e+Events

Using the Fermilab 15-ft neon-hydrogen bubble chamber we have identified seventeen events of the type ..nu../sub ..mu../N ..-->.. ..mu../sup -/e/sup +/X. The ratio of the production of these events to ordinary neutrino charged-current events is (7.7 +- 3.0) x 10/sup -3/ for positron energy greater than 800 MeV and neutrino energy greater than 10 GeV. Associated with these seventeen events are 11 V's, of which eight fit K/sub s//sup 0/ ..-->.. ..pi../sup +/..pi../sup -/ and three fit K/sub s//sup 0/ ..-->.. ..pi../sup +/..pi../sup -/ and ..lambda.. ..-->.. p..pi../sup -/ ambiguously. The average K/sup 0/ multiplicity per ..mu../sup -/e/sup +/ event is determined to be 1.84/sup +0.63//sub -0.53/.

Search forμeEvents in Antineutrino-Nucleon Interactions

A search for ..mu..e events produced in an antineutrino hydrogen-neon experiment using the Fermilab 15-ft bubble chamber is reported. Based on a single candidate, the 90%-confidence upper limit for the relative yield of ..mu../sup +/e/sup -/ events is 0.5% of all charged-current events with antineutrino energy greater than 10 GeV.

Neutrino-proton interactions at Fermilab energies: Experimental arrangement, analysis procedures, and qualitative features of the data

The Fermilab 15-ft bubble chamber filled with hydrogen was exposed to a broad-momentum-band horn-focused neutrino beam produced by 300-GeV interacting protons. The selection procedure to choose a charged-current neutrino event sample is discussed. Less than three percent of the events are due to neutral hadron interactions. We present and experimentally test a method that can be used to identify the muon, estimate the incident neutrino energy, and eliminate most neutral-current interactions from the charged-current sample. Above 10 GeV the method produces an approximately 86% pure sample of charged-current events with an error in energy estimation of the order of 8% over a broad region of the data. In addition we establish experimentally several important properties of high-energy charged-current neutrino interactions. The hadrons are produced in a jet, the individual particles having sharply limited momenta perpendicular to the hadronic axis. The jet structure is maintained with constant properties to very high values of ${Q}^{2}$ and hadronic mass. The fraction of energy going into invisible particles is moderate, consistent with that expected. The average number of neutral pions rises linearly with the average number of charged particles.

Study of High-Energy Antineutrino-Proton Interactions

In an exposure of the Fermilab 15-ft hydrogen bubble chamber to a broad-band $\overline{\ensuremath{\nu}}$ beam, we have observed 106 $\overline{\ensuremath{\nu}}p\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}X$ events with a mean incident energy of 23 GeV. The experimental distributions agree well with the predictions of the quark-parton model. No anomaly is observed in strange-particle production.

Observation ofμ−e+KS0Events Produced by a Neutrino Beam

Four events have been observed with an ${e}^{+}$ and a ${{K}_{s}}^{0}$ decay in the final state induced by a neutrino beam incident on the Fermilab 15-ft neon bubble chamber. Conventional backgrounds are unable to account for these events. Two of the events have in addition a ${\ensuremath{\mu}}^{\ensuremath{-}}$ in the final state clearly identified by the external muon identifier. The other two have ${\ensuremath{\mu}}^{\ensuremath{-}}$ candidates.

Multiplicity Distributions in High-Energy Neutrino Interactions

We present results from the Fermilab 15-ft bubble chamber on the charged-particle multiplicity distributions produced in high-energy charged-current neutrino-proton interactions. Comparisons are made to $\ensuremath{\gamma}p$, $\mathrm{ep}$, $\ensuremath{\mu}p$, and inclusive $\mathrm{pp}$ scattering. The mean hadronic multiplicity $〈{n}_{c}〉$ appears to depend only on the mass of the excited hadronic state, independent of the mode of excitation. A fit to the neutrino data gives $〈{n}_{c}〉=(1.09\ifmmode\pm\else\textpm\fi{}0.38)+(1.09\ifmmode\pm\else\textpm\fi{}0.03)\mathrm{ln}{W}^{2}$.