Single neutral pion production via muon antineutrino charged-current interactions in plastic scintillator (CH) is studied using the \minerva detector exposed to the NuMI low-energy, wideband antineutrino beam at Fermilab. Measurement of this process constrains models of neutral pion production in nuclei, which is important because the neutral-current analog is a background for $\bar{\nu}_e$ appearance oscillation experiments. The differential cross sections for $\pi^0$ momentum and production angle, for events with a single observed $\pi^0$ and no charged pions, are presented and compared to model predictions. These results comprise the first measurement of the $\pi^0$ kinematics for this process.
Flux-averaged differential cross section in $\pi^0$ momentum, $d\sigma/dp_{\pi^0}(10^{-40}\text{cm}^2/\text{nucleon}/(\text{GeV/c})$, for 1$\pi^0$ production with statistical (stat) and systematic (sys) uncertainties.
Flux-averaged differential cross section in $\pi^0$ angle, $d\sigma/d\theta_{\pi^0}(10^{-42}\text{cm}^2/\text{nucleon}/\text{deg.})$, for 1$\pi^0$ production with statistical (stat) and systematic (sys) uncertainties.
The inclusive A(e,e') cross section for $x \simeq 1$ was measured on $~2$H, C, Fe, and Au for momentum transfers $Q~2$ from 1-7 (GeV/c)$~2$. The scaling behavior of the data was examined in the region of transition from y-scaling to x-scaling. Throughout this transitional region, the data exhibit $\xi$-scaling, reminiscent of the Bloom-Gilman duality seen in free nucleon scattering.
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We have measured the ratio g1pF1p over the range 0.029<x<0.8 and 1.3<Q2<10 (GeV/c)2 using deep-inelastic scattering of polarized electrons from polarized ammonia. An evaluation of the integral ∫01g1p(x, Q2)dx at fixed Q2=3 (GeV/c)2 yields 0.127±0.004(stat)±0.010(syst), in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160±0.006. In the quark-parton model, this implies Δq=0.27±0.10.
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Values of G1 computed assuming G1/F1 is independent of Q**2 and using a fixed Q**2 of 3 GeV**2.
We report on a high-statistics measurement of the deuteron spin structure function g1d at a beam energy of 29 GeV in the kinematic range 0.029<x<0.8 and 1<Q2<10 (GeV /c)2. The integral γ1d=∫1g1ddx evaluated at fixed Q2=3 (GeV /c)2 gives 0.042±0.003(stat)±0.004(syst). Combining this result with our earlier measurement of g1p, we find γ1p−γ1n=0.163±0.010(stat)±0.016(syst), which agrees with the prediction of the Bjorken sum rule with O(αs3) corrections, γ1p−γ1n=0.171±0.008. We find the quark contribution to the proton helicity to be Δq=0.30±0.06.
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Values of G1 computed assuming G1/F1 is independent of Q**2 and evaluated at Q**2 = 3 GeV**2.
The spin structure function of the neutron g1n has been determined over the range 0.03<x<0.6 at an average Q2 of 2 (GeV/c)2 by measuring the asymmetry in deep inelastic scattering of polarized electrons from a polarized He3 target at energies between 19 and 26 GeV. The integral of the neutron spin structure function is found to be F01g1n(x)dx=-0.022±0.011. Earlier reported proton results together with the Bjorken sum rule predict F01g1n(x)dx=-0.059±0.019.
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Extrapolarity to full x range.
Results are presented on the difference in R , the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, for the deuteron and the proton. They are obtained by comparing the ratio of cross sections for the deep inelastic scattering of muons from deuterium and hydrogen targets at 90 and 280 GeV incident energy. The results cover the range x =0.01–0.30, at an average Q 2 of 9 GeV 2 . The measured difference R d - R p shows no significant x dependence and is compatible with zero, as well as with expectations from perturbative QCD. We use the same method to obtain the difference R Ca - R C from cross section ratios measured on carbon and calcium targets at 90 and 200 GeV incident energy.
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Average overall x values.
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The structure function ratiosF2C/F2Li,F2Ca/F2Li andF2Ca/F2C were measured in deep inelastic muonnucleus scattering at an incident muon energy of 90 GeV, covering the kinematic range 0.0085<x<0.6 and 0.8<Q2<17GeV2. The sensitivity of the nuclear structure functions to the size and mean density of the target nucleus is discussed.
Overall normalization error of 0.7%, due to uncertainties in target thickness, not included in the table.
Overall normalization error of 0.8%, due to uncertainties in target thickness, not included in the table.
Overall normalization error of 0.5%, due to uncertainties in target thickness, not included in the table.
We present the structure function ratiosF2He/F2D,F2C/F2D andF2Ca/F2D measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. The kinematic range 0.0035<x<0.65 and 0.5<Q2<90 GeV2 is covered. At lowx the three ratios are significantly smaller than unity and the size of the depletion grows with decreasingx and increasing mass numberA. At intermediatex the ratios show an enhancement of about 2% above unity for C/D and Ca/D, possibly less for He/D. There are indications of someQ2 dependence in the Ca/D data. The integrals of the structure function differencesF2A−F2D are discussed.
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Experimental results obtained at the CERN Super Proton Synchrotron on the structure-function ratio F2n/F2p in the kinematic range 0.004<x<0.8 and 0.4<Q2<190 GeV2, together with the structure function F2d determined from a fit to published data, are used to derive the difference F2p(x)-F2n(x). The value of the Gottfried sum F(F2p-F2n)dx/x=0.240±0.016 is below the quark-parton-model expectation of 1/3.
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