Fermilab experiment 866 has measured the Drell-Yan dimuon cross sections in 800 GeV/c pp and pd collisions. This represents the first measurement of the Drell-Yan cross section in pp collisions over a broad kinematic region and the most extensive study to date of the Drell-Yan cross section in pd collisions. The results are compared to previous measurements and to predictions based on various global parton distribution function fits. The implications for future parton distribution fits are discussed.

T.H. Chang, ∗ M.E. Beddo, C.N. Brown, T.A. Carey, W.E. Cooper, C.A. Gagliardi, G.T. Garvey, D.F. Geesaman, E.A. Hawker, 6, † X.C. He, L.D. Isenhower, D.M. Kaplan, S.B. Kaufman, D.D. Koetke, P.L. McGaughey, W.M. Lee, ‡ M.J. Leitch, J.M. Moss, B.A. Mueller, V. Papavassiliou, J.C. Peng, ∗ P.E. Reimer, 2 M.E. Sadler, W.E. Sondheim, P.W. Stankus, R.S. Towell, 6 R.E. Tribble, M.A. Vasiliev, § J.C. Webb, ¶ J.L. Willis, and G.R. Young (FNAL E866/NuSea Collaboration) Abilene Christian University, Abilene, TX 79699 Argonne National Laboratory, Argonne, IL 60439 Fermi National Accelerator Laboratory, Batavia, IL 60510 Georgia State University, Atlanta, GA 30303 Illinois Institute of Technology, Chicago, IL 60616 Los Alamos National Laboratory, Los Alamos, NM 87545 New Mexico State University, Las Cruces, NM, 88003 Oak Ridge National Laboratory, Oak Ridge, TN 37831 Texas A&M University, College Station, TX 77843 Valparaiso University, Valparaiso, IN 46383 (Dated: August 4, 2003)

The Fermilab E866/NuSea Collaboration has measured the Drell-Yan dimuon cross sections in 800 GeV/c proton-proton and proton-deuterium collisions. This is the first measurement of the absolute Drell-Yan cross section in proton-proton collisions over a broad kinematic region and the most extensive study to date of the Drell-Yan cross section in proton-deuterium collisions. The Drell-Yan mechanism is sensitive to both the beam and target parton distributions, In particular, with the kinematics of the E866/NuSea data, the Drell-Yan mechanism is sensitive to the target antiquark distributions at low and intermediate Bjorken-x and to the beam quark distributions at high-x. Approximately 55K proton-proton and 121K proton-deuterium Drell-Yan events over the longitudinal momentum fraction (Feynman-x) range -0.05 < x(F) < 0.8 and the mass ranges 4.2 < Mmu+mu- < 8.7 GeV and 10.85 < M <16.85 GeV are included. The data analysis will be described, and the doubly-differential M(3)d(2)sigma/dMdx(F), and triply-differential cross sections Ed(3)sigma/dp(3) will be presented. These results will be compared with previous measurements by E605 and E772 and to predictions based upon next-to-leading order calculations utilizing the MRST2001 and CTEQ6 global parton distribution function fits. The results indicate that recent global parton distribution fits provide a good description of the light antiquark sea in the nucleon over the Bjorken-x range 0.03 < x < 0.15. In contrast, the valence quark distributions appear to be overestimated by the current parton distribution fits as x --> 1; a region in which, prior to this data, there was very little proton data to constrain the global fits.While the overall normalization is well reproduced, there are systematic deviations between the measurements and the predictions that are reflected in the large X 2 values. To elucidate these deviations, it is useful to examine the experimental cross sections separately as functions of x(1) and x(2) As noted, most of the events have x(1) much greater than x(2) which implies that the xi dependence is primarily sensitive to the valence quarks in the proton beam while the x2 dependence measures the antiquarks in the target. Figure 2 shows the ratios of the measured cross sections to NLO calculations using the MRST2001 PDFs, separately as functions of x(2) and x(1). The uncertainties in the NLO calculations from the PDF fit are also shown. he MRST2001 partons provide a good description of the x2 dependence of both the pp and pd cross sections. The CTEQ6 fits describe the x2 dependence equally well.As a function of x(1), MRST2001 and CTEQ6 have similar behavior: both overestimate the valence quarks by 15-20% at large x(1). The MRST2001 and CTEQ6 partons show essentially the same x(1) dependence, and the discrepancy between the data and current PDFs appears to be larger for the pd cross sections than the pp cross sections. Some of this discrepancy may be accounted for by radiative corrections, which are presently being studied. The pp and pd cross sections at large x, constrain two slightly different linear combinations of u(V) and d(V). The results imply that the u quark distributions in CTEQ6 and MRST2001 are overestimated as x --> 1. The Drell-Yan cross sections may also point to problems with the d/u ratio as x --> 1 [11]. However, determination of the d/u ratio at large x from these data will require a global fit to the full two-dimensional invariant cross sections together with the rest of the current world's data.It is important to recognize that this discrepancy is nearly within the quoted uncertainties on the valence quark distributions in the current PDFs [1, 12] and the +/-6.5% normalization uncertainty on the cross sections. Therefore, future global PDF fits that include these new results should provide a much better description of the E866 Drell-Yan cross sections, together with improved determinations of the antiquark distributions for 0.03 less than or equal to x < 0.15 and of the valence quark distributions for x --> 1, without significant degradation to the quality of the fit for the rest of the world's current data. This work was supported in part by the U.S. Department of Energy.

We present measurements of the polarization of the J/psi produced in 800-GeV proton interactions with a copper target. Polarization of the J/psi is sensitive to the ccmacr; production and hadronization processes. A longitudinal polarization is observed at large x(F), while at small x(F) the state is produced essentially unpolarized or slightly transversely polarized. No significant variation of the polarization is observed versus p(T).

We report the elliptic flow of charged and identified particles at mid-rapidity in Au+Au collisions at √ s NN = 130 GeV using the STAR TPC at RHIC. The integrated elliptic flow signal, v 2 , for charged particles reaches values of about 0.06, indicating a higher degree of thermalization than at lower energies. The differential elliptic flow signal, v 2 (p t) up to 1.5 GeV/c, shows a behavior expected from hydrodynamic model calculations. Above 1.5 GeV/c, the data deviate from the hydro predictions; however the v 2 (p t) is still large, suggesting finite asymmetry for the products of hard scattering. For the identified particles, elliptic flow as a function of p t and centrality differ significantly for particles of different masses. This dependence can be accounted for in hydrodynamic models, indicating that the system created shows a behavior consistent with collective hydrodynamical flow.

Despite QCD's success in describing many aspects of the strong interaction, an adequate description of quarkonia production is still missing. While the production of the heavy Q (Q) over bar pair from gluon-gluon fusion or quark-antiquark annihilation can be perturbatively calculated, the long-distance process involving the formation of the bound states is presently not amenable to calculation. Various models of quarkonia production have been proposed, including color singlet and octet components, and these models make predictions for polarization of the quarkonia. FNAL E866 has measured the polarization of quarkonia production in the psi and gamma families. The data show that the gamma(1S) is produced with only slight polarization, and only at large fractional longitudinal momentum (x(F)) or large transverse momenta (P-T), while the Y(2S) and (3S) states are completely polarized. In the psi family, the J/psi is produced with only slight polarization, which changes from transverse to longitudinal as a function of increasing x(F). These results are particularly important to both RHIC and CERN, where charmonium formation plays a critical role in the search for a quark-gluon plasma.

Measurements of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on liquid hydrogen and deuterium targets are reported. Approximately 360 000 Drell-Yan muon pairs remained after all cuts on the data. From these data, the ratio of down antiquark ((d) over bar) to up ((u) over bar) antiquark distributions in the proton sea is determined over a wide range in Bjorken-x. These results confirm previous measurements by E866 and extend them to lower x. From these data, ((d) over bar-(u) over bar) and integral((d) over bar-(u) over bar )dx are evaluated for 0.015<x<0.35. These results are compared with parametrizations of various par-ton distribution functions, models and experimental results from NA51, NMC and HERMES.

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.

Measurements at 18 beam kinetic energies between 1975 and 2795 MeV and at 795 MeV are reported for the pp elastic scattering spin correlation parameter A(00nn) = (N.N,0,0)= C-NN=A(NN). The c.m. angular range is typically 60 degrees -100 degrees. These results are compared to previous data from Saturne II and other accelerators. A search for energy-dependent structure at fixed c.m. angles is performed. Comparisons are made to phase shift analysis and theoretical model predictions of this spin observable.

Measurements of the suppression of the yield per nucleon of $J/\\ensuremath{\\psi}$ and ${\\ensuremath{\\psi}}^{\\ensuremath{'}}$ production for 800 GeV/ $c$ protons incident on heavy nuclear targets, relative to light nuclear targets, have been made with very broad coverage in ${x}_{F}$ and ${p}_{T}$. The observed suppression is smallest at ${x}_{F}$ values of 0.25 and below, and increases at larger values of ${x}_{F}$. It is also strongest at small ${p}_{T}$. Substantial differences between ${\\ensuremath{\\psi}}^{\\ensuremath{'}}$ and $J/\\ensuremath{\\psi}$ production are observed for the first time in $p\\ensuremath{-}A$ collisions. The suppression for ${\\ensuremath{\\psi}}^{\\ensuremath{'}}$ production is stronger than that for $J/\\ensuremath{\\psi}$ for ${x}_{F}$ near zero, but becomes comparable to that for $J/\\ensuremath{\\psi}$ for ${x}_{F}g0.6$.

Measurements of Drell-Yan cross sections from the bombardment of liquid deuterium and hydrogen with an 800 GeV proton beam are reported. The relative cross section (sigma (pd)/2 sigma (pp)) directly probes the ratio of anti-down ((d) over bar) to anti-up ((u) over bar) quarks in the nucleon sea, while absolute measurement of the deuterium cross section constrain (d) over bar + (u) over bar. Results are compared with previous experiments and next-to-leading order calculations based on current sets of parton distribution functions.

Evaluated nuclear structure and decay data are presented for 16 known A=126 nuclides (Rh, Pd, Ag, Cd, In, Sn, Sb, Te, I, Xe, Cs, Ba, La, Ce, Pr, Nd). The A=126 mass chain was last evaluated by J. Katakura and K. Kitao, which was published in Nuclear Data Sheets 97, 765 (2002) (2002Ka66). In 2015, B. Singh evaluated the data of 126Rh, 126Pd and 126Ag. The current work is an update of these previous evaluations. Experimental data from new publications since 2002Ka66 have been incorporated. Even when no new publications appeared, some previous datasets have been modified for new β-decay Q values and conversion coefficients. Adopted values for levels and gammas are based on data of various decays and reactions. Inconsistencies and discrepancies have been noted.

We have studied how lepton pairs from decays of heavy-flavoured mesons produced in pA collisions can be used to determine the modifications of the gluon distribution in the nucleus. Since heavy-quark production is dominated by the gg channel, the ratio of correlated lepton pair cross sections from DD and BB decays in pA and pp collisions directly reflects the ratio RgA≡fgA/fgp. We have numerically calculated the lepton-pair cross sections from these decays in pp and pA collisions at SPS, RHIC and LHC energies. We find that ratio of the pA to pp cross sections agrees quite well with the input RgA. Thus, sufficiently accurate measurements could be used to determine the nuclear modification of the gluon distribution over a greater range of x and Q2 than presently available, putting strong constraints on models.

A precise measurement of the ratios of the Drell-Yan cross section per nucleon for an 800 GeV/c proton beam incident on Be, Fe and W targets is reported. The behavior of the Drell-Yan ratios at small target parton momentum fraction is well described by an existing fit to the shadowing observed in deep-inelastic scattering. The cross section ratios as a function of the incident parton momentum fraction set tight limits on the energy loss of quarks passing through a cold nucleus.

Measurements at 18 beam kinetic energies between 1975 and 2795 MeV and at 795 MeV are reported for the pp elastic-scattering single spin parameter Aooon=Aoono=AN=P. The c.m. angular range is typically 60–100°. These results are compared to previous data from Saturne II and other accelerators. A search for energy-dependent structure at fixed c.m. angles is performed, but no rapid changes are observed.Received 1 June 1999DOI:https://doi.org/10.1103/PhysRevC.60.054002©1999 American Physical Society

Fermilab E866 has performed a precise measurement of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on hydrogen and deuterium targets, leading to the first determinations of (d) over bar/(u) over bar and (d) over bar - (u) over bar in the proton as functions of x. The results show that (d) over bar > (u) over bar over a broad range of x and provide valuable information regarding the origins of the (d) over bar/(u) over bar asymmetry and the antiquark sea in the nucleon.