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Measurement of Angular Distributions of Drell-Yan Dimuons in p + p Interactions at 800 GeV / c

2009; American Physical Society; Volume: 102; Issue: 18 Linguagem: Inglês

10.1103/physrevlett.102.182001

1092-0145

Lilin Zhu, J. C. Peng, P. E. Reimer, T. C. Awes, M. L. Brooks, C. N. Brown, J. D. Bush, T. A. Carey, Tung‐Zong Chang, W. E. Cooper, C. A. Gagliardi, G. T. Garvey, D. F. Geesaman, E. Hawker, X. He, L. Isenhower, Daniel M. Kaplan, S. Kaufman, S. Klinksiek, D. D. Koetke, D. M. Lee, W. M. Lee, M. J. Leitch, N. C. R. Makins, P. L. McGaughey, J. M. Moss, B. Mueller, P. M. Nord, V. Papavassiliou, B. K. Park, G. Petitt, M. E. Sadler, W. E. Sondheim, P. W. Stankus, T. N. Thompson, R. S. Towell, R. E. Tribble, M. A. Vasiliev, J. C. Webb, J. L. Willis, Derek K. Wise, G. R. Young,

Quantum Chromodynamics and Particle Interactions

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an $800\text{ }\text{ }\mathrm{GeV}/c$ proton beam on a hydrogen target. The polar and azimuthal angular distribution parameters have been extracted over the kinematic range $4.5<{m}_{\ensuremath{\mu}\ensuremath{\mu}}<15\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ (excluding the $\ensuremath{\Upsilon}$ resonance region), $0<{p}_{T}<4\text{ }\text{ }\mathrm{GeV}/c$, and $0<{x}_{F}<0.8$. The $p+p$ angular distributions are similar to those of $p+d$, and both data sets are compared with models which attribute the $\mathrm{cos}2\ensuremath{\phi}$ distribution either to the presence of the transverse-momentum-dependent Boer-Mulders structure function ${h}_{1}^{\ensuremath{\perp}}$ or to QCD effects. The data indicate the need to include QCD effects before reliable information on the Boer-Mulders function can be extracted. The validity of the Lam-Tung relation in $p+p$ Drell-Yan data is also tested.