1. Measurement of flavor asymmetry of light-quark sea in the proton with Drell-Yan dimuon production in $p+p$ and $p+d$ collisions at 120 GeV
- Author
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Dove, J., Kerns, B., Leung, C., McClellan, R. E., Miyasaka, S., Morton, D. H., Nagai, K., Prasad, S., Sanftl, F., Scott, M. B. C., Tadepalli, A. S., Aidala, C. A., Arrington, J., Ayuso, C., Barker, C. T., Brown, C. N., Chang, T. H., Chang, W. C., Chen, A., Christian, D. C., Dannowitz, B. P., Daugherity, M., Diefenthaler, M., Fassi, L. El, Geesaman, D. F., Gilman, R., Goto, Y., Guo, L., Guo, R., Hague, T. J., Holt, R. J., Isenhower, D., Kinney, E. R., Kitts, N. D., Klein, A., Kleinjan, D. W., Kudo, Y., Lin, P. -J., Liu, K., Liu, M. X., Lorenzon, W., Makins, N. C. R., de Medeiros, M. Mesquita, McGaughey, P. L., Miyachi, Y., Mooney, I., Nakahara, K., Nakano, K., Nara, S., Peng, J. C., Puckett, A. J., Ramson, B. J., Reimer, P. E., Rubin, J. G., Sawada, S., Sawada, T., Shibata, T. -A., Shiu, S. H., Su, D., Teo, M., Tice, B. G, Towell, R. S., Uemura, S., Watson, T. S., Wang, S. G., Wickes, A. B., Wu, J., Xi, Z., and Ye, Z.
- Subjects
High Energy Physics - Phenomenology ,High Energy Physics - Experiment ,Nuclear Experiment - Abstract
Evidence for a flavor asymmetry between the $\bar u$ and $\bar d$ quark distributions in the proton has been found in deep-inelastic scattering and Drell-Yan experiments. The pronounced dependence of this flavor asymmetry on $x$ (fraction of nucleon momentum carried by partons) observed in the Fermilab E866 Drell-Yan experiment suggested a drop of the $\bar d\left(x\right) / \bar u\left(x\right)$ ratio in the $x > 0.15$ region. We report results from the SeaQuest Fermilab E906 experiment with improved statistical precision for $\bar d\left(x\right) / \bar u\left(x\right)$ in the large $x$ region up to $x=0.45$ using the 120 GeV proton beam. Two different methods for extracting the Drell-Yan cross section ratios, $\sigma^{pd} /2 \sigma^{pp}$, from the SeaQuest data give consistent results. The $\bar{d}\left(x\right) / \bar{u}\left(x\right)$ ratios and the $\bar d\left(x\right) - \bar u\left(x\right)$ differences are deduced from these cross section ratios for $0.13 < x < 0.45$. The SeaQuest and E866/NuSea $\bar{d}\left(x\right) / \bar{u}\left(x\right)$ ratios are in good agreement for the $x\lesssim 0.25$ region. The new SeaQuest data, however, show that $\bar d\left(x\right)$ continues to be greater than $\bar u\left(x\right)$ up to the highest $x$ value ($x = 0.45$). The new results on $\bar{d}\left(x\right) / \bar{u}\left(x\right)$ and $\bar{d}\left(x\right) - \bar{u}\left(x\right)$ are compared with various parton distribution functions and theoretical calculations.
- Published
- 2022