Fermilab 15-foot Bubble Chamber Research Articles

Coherent production of single pions and rho mesons in charged-current interactions of neutrinos and antineutrinos on neon nuclei at the Fermilab Tevatron.

The coherent production of [pi] and [rho] mesons in [nu][sub [mu]]([bar [nu]][sub [mu]])--neon charged-current interactions has been studied using the Fermilab 15-foot bubble chamber filled with a heavy Ne-H[sub 2] mix and exposed to the Teva- tron quadrupole triplet (anti)neutrino beam. The [nu][sub [mu]] ([bar [nu]][sub [mu]]) beam had an average energy of 80 GeV (70 GeV). From a sample corresponding to approximately 28 000 charged-current interactions, net signals of (53[plus minus]9) [mu][sup [plus minus]][pi][sup [minus plus]] coherent events and (19[plus minus]7) [mu][sup [plus minus]][pi][sup [minus plus]][pi][sup 0] coherent events are extracted. For [ital E][gt]10 GeV, the coherent pion production cross section is determined to be (3.2[plus minus]0.7)[times]10[sup [minus]38] cm[sup 2] per neon nucleus whereas the coherent [rho] production cross section is (2.1[plus minus]0.8)[times]10[sup [minus]38] cm[sup 2] per neon nucleus. These cross sections and the kinematical characteristics of the coherent events at [vert bar][ital t][vert bar][lt]0.1 GeV[sup 2] are found to be in general agreement with the predictions of a model based on the hadron dominance and, in the pion case, on the partially conserved axial-vector current hypothesis. Also discussed is the coherent production of systems consisting of three pions.

Study of high-energy neutrino neutral-current interactions.

From an exposure of the Fermilab 15-foot bubble chamber to the Tevatron quadrupole triplet neutrino beam, we have determined the ratio of neutral-current (NC) to charged-current (CC) interactions to be 0.288{plus minus}0.032 for events with visible hadron momentum above 10 GeV/{ital c}. The mean {nu}({bar {nu}}) event energy is 150 (110) GeV, which is higher than that for any previous beam. This result agrees with those from previous experiments at lower energies. The NC/CC ratio is derived for a combined sample of {nu} and {bar {nu}} events. A value of 0.274{plus minus}0.038 is obtained for the dominant {nu} component assuming {bar {nu}} NC/CC=0.39{plus minus}0.08. For events with visible hadron momentum above 25 GeV/{ital c}, where the neutral hadron contamination remaining in the NC sample is assumed to be negligible, the combined NC/CC is 0.323{plus minus}0.025 and the {ital K}{sup 0} production rates are 0.375{plus minus}0.064 per CC and 0.322{plus minus}0.073 per NC event. The corresponding {Lambda} rates are 0.161{plus minus}0.030 per CC and 0.113{plus minus}0.030 per NC event. The {ital K}{sup 0} and {Lambda} distributions of the fractional hadron energy variable {ital z} in NC events are consistent with those in CC events.

Holography of particle tracks in the Fermilab 15-foot bubble chamber

Holography of particle tracks in the Fermilab 15-foot bubble chamber

Laser pulse stretching via enhanced closed loop control with slow Q-switching

A pulse stretching technique in a Q-switched ruby laser oscillator is described. The major improvement to our previously developed pulse stretching circuit consists in a more adequate waveform for the feedforward part. This new system gives fairly flat pulses with adjustable duration up to ∼ 100 μs and good coherence length in excess of 11 m. The cavity is followed by several amplifiers and produces light energies up to 8 J for holographic recording of particle tracks in the Fermilab 15-foot bubble chamber. The considerably increased coherence length will find applications in many fields of pulsed holography and its use with fiber optics is particularily promising.

Monitoring of a high-power pulsed ruby laser

A high-power pulsed ruby laser was used to take holograms of neutrino interactions in the Fermilab 15-foot Bubble Chamber. This paper describes a system to monitor and record its most relevant parameters such as the light pulse energy, its width and shape, and the spatial intensity distribution. A second aim of this system was to help in the alignment of the laser beam towards the dispersing lens, located inside the Bubble chamber, as well as to provide a fast check of the alignment without interrupting the holographic recording. This system was required to work in the strong magnetic field (∼0.5 T) surrounding the 15-foot Bubble Chamber, which introduced additional technical problems.

Erratum: Measurement of muon-neutrino-electron elastic scattering in the Fermilab 15-foot bubble chamber

A total of 22 muon-neutrino-electron elastic-scattering events (${\ensuremath{\nu}}_{\ensuremath{\mu}}e\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\mu}}e$) have been observed in an exposure of the Fermilab 15-foot bubble chamber filled with a heavy neon-hydrogen mixture to a wide-band neutrino beam. The elastic-scattering cross section is measured to be $1.67\ifmmode\pm\else\textpm\fi{}0.44\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}42}{E}_{\ensuremath{\nu}}$ ${\mathrm{cm}}^{2}$ Ge${\mathrm{V}}^{\ensuremath{-}1}$. The value of the weak mixing angle (${{sin}^{2}\ensuremath{\theta}}_{W}$) determined from this cross section, which is consistent with other measurements of this angle, is ${0.20}_{\ensuremath{-}0.05}^{+0.06}$.

Left-right asymmetry in neutrino-produced hadron jets.

In an experiment (E546) to study interactions of {l angle}{ital E}{r angle}=100 GeV and {l angle}{ital Q}{sup 2}{r angle}=17 GeV{sup 2} neutrinos in the Fermilab 15-foot bubble chamber, we have looked for a left-right asymmetry in the azimuthal angle {phi} of individual hadrons about the direction of the lepton momentum transfer ({ital q} vector). Significant asymmetry is found for forward positive hadrons; for {ital x}{sub {ital F}}{gt}0.10, we find {l angle}cos{phi}{r angle}={minus}0.029{plus minus}0.008, where {ital x}{sub {ital F}} is the Feynman {ital x} variable. Negative hadrons with {ital x}{sub {ital F}}{gt}0.10 show no asymmetry, {l angle}cos{phi}{r angle}=0.004{plus minus}0.011. A model which includes parton intrinsic transverse momentum {ital k}{sub {ital t}} reproduces the asymmetry of combined positive and negative hadrons with {ital x}{sub {ital F}}{gt}0.10, {l angle}cos{phi}{r angle}={minus}0.018{plus minus}0.0065, if {l angle}{ital k}{sub {ital t}}{sup 2}{r angle}=0.065{plus minus}0.024 GeV{sup 2}/c{sup 2}. But the model predicts almost equal asymmetries for positive and negative hadrons. The model also agrees poorly with the observed dependence on the kinematic variables {ital x} and {ital Q}{sup 2} if the {ital k}{sub {ital t}} distribution is assumed to be independent of kinematic variables.

Measurement of muon-neutrino-electron elastic scattering in the Fermilab 15-foot bubble chamber.

A total of 22 muon-neutrino-electron elastic-scattering events (${\ensuremath{\nu}}_{\ensuremath{\mu}}e\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\mu}}e$) have been observed in an exposure of the Fermilab 15-foot bubble chamber filled with a heavy neon-hydrogen mixture to a wide-band neutrino beam. The elastic-scattering cross section is measured to be $1.67\ifmmode\pm\else\textpm\fi{}0.44\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}42}{E}_{\ensuremath{\nu}}$ ${\mathrm{cm}}^{2}$ Ge${\mathrm{V}}^{\ensuremath{-}1}$. The value of the weak mixing angle (${{sin}^{2}\ensuremath{\theta}}_{W}$) determined from this cross section, which is consistent with other measurements of this angle, is ${0.20}_{\ensuremath{-}0.05}^{+0.06}$.

Holography in the Fermilab 15-foot bubble chamber

Holography in combination with conventional photography offers the possibility of measuring rare interactions with short lifetimes in large detectors. First experience has been gained with a modified in-line holographic technique during an exposure of the Fermilab 15-Foot Bubble Chamber to a wide-band neutrino beam. Future plans for improvements are outlined.

Dilepton production by neutrinos in the Fermilab 15-foot bubble chamber

In an exposure of the Fermilab 15-foot neon-hydrogen bubble chamber to a quadrupole triplet neutrino beam, 49 ..mu../sup -/e/sup +/ and 14 ..mu../sup +/e/sup -/ events with e/sup + -/ momenta greater than 0.3 GeV/c have been observed, yielding ..mu..e rates per charged-current event of (0.73 +- 0.11)% and (1.1 +- 0.3)%, respectively. The ..mu../sup -/e/sup +/ rate shows no strong energy dependence in the range from 30 to 300 GeV. The 18 neutral strange particles observed in the 63 events contain 14 K/sup 0//sub S/, 2 ..lambda.., and 2 ..lambda../K/sup 0//sub S/ ambiguities, suggesting that the events are predominantly D-meson production and decay and that the ..lambda../sup +//sub c/..--> lambda..eX branching ratio is very small. The corrected numbers of neutral strange particles per ..mu../sup -/e/sup +/ and ..mu../sup +/e/sup -/ event are 1.2 +- 0.3 and 0.6/sup +0.6//sub -0.3/, respectively. Properties of the events, including strange-particle production, are compared to ..mu../sup - +/..mu../sup + -/ events in the same experiment and to a charm production and decay model, and good agreement is found, apart from a possible enhancement at approx.5--6 GeV/c/sup 2/ in the mass of the system recoiling against the ..mu../sup +/ in ..mu../sup +/e/sup -/ (and ..mu../supmore » +/..mu../sup -/) events. As reported previously, four events show short-lived-particle decays, and D-meson lifetime estimates are reevaluated using the final event sample. One ..mu../sup +/e/sup +/ and three ..mu../sup -/e/sup -/ events were observed. The ..mu../sup -/e/sup -/ events are consistent with background and lead to a ..mu../sup -/e/sup -//..mu../sup -/e/sup +/ ratio of less than 0.07 (90% confidence level) for e/sup + -/ momenta above 0.8 GeV/c. Five candidates for dilepton production by electron neutrinos and antineutrinos in the beam are consistent with approximately 1% rates. No good three-lepton candidates were found, and one, previously reported, four-lepton candidate was found.« less

Production and decay of F +(2030) observed in νμ interactions in emulsion

An event representing the production and decay of the charmed F + meson has been identified by means of a 3-constraint fit to decay hypothesis F + → π + π + π − π 0, in which both γ- rays from the π 0 converted. The event was produced by a charged current ν μ interaction in an emulsion stack located inside the Fermilab 15-foot bubble chamber. The F + traveled 50 μm, corresponding to a proper time of 1.4 × 10 −13 seconds, before decaying in flight. Its mass was determined to be 2017 ± 25MeV.

Dimuon production by neutrinos in the Fermilab 15-foot bubble chamber

Dimuon production by neutrinos in the Fermilab 15-foot bubble chamber

Neutrino and antineutrino proton scattering data and the ratio of down to up quarks in the proton

New data on the x-dependence of the ratio of down to up quarks in the proton are presented from neutrino and antineutrino experiments using the Fermilab 15-foot bubble chamber filled with hydrogen. The new data are in good agreement with existing data from electron scattering experiments performed at SLAC but are not accurate enough at large x to discriminate between the QCD prediction and a (1 − x) behavior as x → 1.