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dbar/ubar Asymmetry and the Origin of the Nucleon Sea

J. C. Peng, G. T. Garvey, T. C. Awes, M. E. Beddo, M. L. Brooks, C. N. Brown, J. D. Bush, T. A. Carey, T. H. Chang, W. E. Cooper, C. A. Gagliardi, D. F. Geesaman, E. A. Hawker, X. C. He, L. D. Isenhower, S. B. Kaufman, D. M. Kaplan, P. N. Kirk, D. D. Koetke, G. Kyle, D. M. Lee, W. M. Lee, M. J. Leitch, N. Makins, P. L. McGaughey, J. M. Moss, B. A. Mueller, P. M. Nord, B. K. Park, V. Papavassiliou, G. Petitt, P. E. Reimer, M. E. Sadler, J. Selden, P. W. Stankus, W. E. Sondheim, T. N. Thompson, R. S. Towell, R. E. Tribble, M. A. Vasiliev, Y. C. Wang, Z. F. Wang, J. C. Webb, J. L. Willis, D. K. Wise, G. R. Young

Abstract

The Drell-Yan cross section ratios, $σ(p+d)/σ(p+p)$, measured in Fermilab E866, have led to the first determination of $\bar d(x) / \bar u(x)$, $\bar d(x) - \bar u(x)$, and the integral of $\bar d(x) - \bar u(x)$ for the proton over the range $0.02 \le x \le 0.345$. The E866 results are compared with predictions based on parton distribution functions and various theoretical models. The relationship between the E866 results and the NMC measurement of the Gottfried integral is discussed. The agreement between the E866 results and models employing virtual mesons indicates these non-perturbative processes play an important role in the origin of the $\bar d$, $\bar u$ asymmetry in the nucleon sea.

dbar/ubar Asymmetry and the Origin of the Nucleon Sea

Abstract

The Drell-Yan cross section ratios, , measured in Fermilab E866, have led to the first determination of , , and the integral of for the proton over the range . The E866 results are compared with predictions based on parton distribution functions and various theoretical models. The relationship between the E866 results and the NMC measurement of the Gottfried integral is discussed. The agreement between the E866 results and models employing virtual mesons indicates these non-perturbative processes play an important role in the origin of the , asymmetry in the nucleon sea.

Paper Structure

This paper contains 7 equations, 3 figures, 1 table.

Figures (3)

  • Figure 1: Comparison of the E866 $\bar{d} - \bar{u}$ results with the predictions of various models as described in the text.
  • Figure 2: $F^p_2 - F^n_2$ as measured by NMC compared with predictions based on the CTEQ4M and MRS(R2) parametrizations. Also shown are the E866 results for the sea-quark contribution to $F^p_2 - F^n_2$. For each prediction, the top (bottom) curve is the valence (sea) contribution and the middle curve is the sum of the two.
  • Figure 3: Comparison of E866 $\bar{d} / \bar{u}$ ratios at $Q$ = 7.35 GeV with the predictions of two virtual pion models and the chiral model. The fit $1 + 1120 x^{2.75} (1-x)^{15}$ is also shown.