Search Results (10 total)

We report on the extraction of R  =  σ_L / σ_T from CCFR ν_μ-Fe and ν̅ _μ-Fe differential cross sections. The CCFR differential cross sections do not show the deviations from the QCD expectations that are seen in the CDHSW data at very low and very high x. R as measured in ν_μ scattering is in agreement with R as measured in muon and electron scattering. All data on R for Q²>1 GeV² are in agreement with a NNLO QCD calculation which uses NNLO parton distribution functions and includes target mass effects. We report on the first measurements of R in the low x and Q²<1 GeV² region (where an anomalous large rise in R for nuclear targets has been observed by the HERMES Collaboration).

A new structure function analysis of CCFR deep inelastic ν-N and ν̅ -N scattering data is presented for previously unexplored kinematic regions down to Bjorken x  =  0.0045 and Q²  =  0.3 GeV². Comparisons to charged lepton scattering data from NMC and E665 experiments are made and the behavior of the structure function F₂^ν is studied in the limit Q²→0.

We report on the extraction of the structure functions F₂ and ΔxF₃  =  xF₃^ν-xF₃^ν̅ from CCFR ν_μ-Fe and ν̅ _μ-Fe differential cross sections. The extraction is performed in a physics model-independent (PMI) way. This first measurement of ΔxF₃, which is useful in testing models of heavy charm production, is higher than current theoretical predictions. The ratio of the F₂ (PMI) values measured in ν_μ and μ scattering is in agreement (within 5%) with the predictions of next-to-leading-order parton distribution functions using massive charm production schemes, thus resolving the long-standing discrepancy between the two sets of data.

Data from the CCFR E770 neutrino deep inelastic scattering experiment at Fermilab contain events with a large Bjorken x (x>0.7) and high momentum transfer [Q²>50 (GeV/c)²]. A comparison of the data with a model based on no nuclear effects at large x shows a significant excess of events in the data. The addition of Fermi gas motion of the nucleons in the nucleus to the model does not explain the excess. Adding a higher momentum tail due to the formation of “quasi-deuterons” makes some improvement. An exponentially falling F₂∝e^-s(x-x₀) at large x, predicted by “multi-quark clusters” and “few-nucleon correlations,” can describe the data. A value of s=8.3±0.7(stat)±0.7(syst) yields the best agreement with the data.

We present new limits on v_e(v_e)→v_τ(v_τ) and v_e(v_e)→v_s oscillations by searching for v_e disappearance in the high-energy wideband CCFR neutrino beam. Sensitivity to v_τ appearance comes from τ decay modes in which a large fraction of the energy deposited is electromagnetic. The beam is composed primarily of v_μ(v_μ), but this analysis uses the 2.3% v_e(v_e) component of the beam. Electron neutrino energies range from 30 to 600 GeV and flight lengths vary from 0.9 to 1.4 km. This limit improves the sensitivity of existing limits for v_e→v_τ at high Δm² and obtains a lowest 90% confidence upper limit in sin² 2α of 9.9×10^-2 at Δm²∼125 eV².

We extract a set of values for the Gross–Llewellyn Smith sum rule at different values of 4-momentum transfer squared ( Q²), by combining revised CCFR neutrino data with data from other neutrino deep-inelastic scattering experiments for 1<Q²<15 GeV²/c². A comparison with the order α_s³ theoretical predictions yields a determination of α_s at the scale of the Z-boson mass of 0.114±_0.012^0.009. This measurement provides a new and useful test of perturbative QCD at low Q², because of the low uncertainties in the higher order calculations.

We present an improved determination of the proton structure functions F₂ and xF₃ from the Columbia-Chicago-Fermilab-Rochester Collaboration ν-Fe deep inelastic scattering experiment. Comparisons to corrected high-statistics charged-lepton scattering results for F₂ from the NMC, E665, SLAC, and BCDMS experiments indicate good agreement for x>0.1 but some discrepancy at lower x. The Q² evolution of both the F₂ and xF₃ structure functions yields a value of the strong coupling constant at the scale of mass of the Z boson of α_s(M_Z²)  =  0.119±0.002(expt)±0.004(theory). This is one of the most precise measurements of this quantity.

Limits on ν_μ(ν̅ _μ)→ν_e(ν̅ _e) oscillations based on a statistical separation of ν_eN charged current interactions in the CCFR detector at Fermilab are presented. Neutrino energies range from 30 to 600 GeV with a mean of 140 GeV, and ν_μ flight lengths vary from 0.9 to 1.4 km. The result excludes oscillations in the region with sin²2α>1.8×10^-3 for large Δm² (>1000 eV²) and Δm²>1.6 eV² for sin²2α  =  1. This result is the most stringent limit to date for Δm²>25 eV² and it excludes the high Δm² oscillation region favored by the LSND experiment. The ν_μ-to- ν_e cross-section ratio was measured as a test of ν_μ(ν̅ _μ)↔ν_e(ν̅ _e) universality to be 1.026±0.025(stat)±0.049(syst).

We present limits on ν_μ(ν̅ _μ)→ν_τ(ν̅ _τ) and ν_μ(ν̅ _μ)→ν_e(ν̅ _e) oscillations based on a study of inclusive νN interactions performed using the CCFR massive coarse-grained detector in the Fermilab Tevatron Quadrupole Triplet neutrino beam. The sensitivity to oscillations is from the difference in the longitudinal energy deposition pattern of ν_μN vs ν_τN or ν_eN charged-current interactions. The ν_μ energies ranged from 30 to 500 GeV with a mean of 140 GeV. The minimum and maximum ν_μ flight lengths are 0.9 and 1.4 km, respectively. For ν_μ→ν_τ oscillations, the lowest 90% confidence upper limit in sin²2α of 2.7 × 10^-3 is obtained at Δm²∼50 eV². This result is the most stringent limit to date for 25<Δm²<90 eV². For ν_μ→ν_e oscillations, the lowest 90% confidence upper limit in sin²2α of 1.9 × 10^-3 is obtained at Δm²∼350 eV². This result is the most stringent limit to date for 250<Δm²<450 eV², and also excludes at 90% confidence much of the high Δm² region favored by the recent LSND observation.

We report a precise measurement of the weak mixing angle from the ratio of neutral current to charged current inclusive cross sections in deep-inelastic neutrino-nucleon scattering. The data were gathered at the CCFR neutrino detector in the Fermilab quadrupole-triplet beam, with neutrino energies up to 600 GeV. Using the on-shell definition, sin²θ_W==1-M_W²/M_Z², we obtain sin²θ_W=0.2218±0.0025(stat)±0.0036(expt syst)±0.0037(model).