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Register a new userAbsolute Drell-Yan Dimuon Cross Sections in 800 GeV/c pp and pd Collisions
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The Fermilab E866/NuSea Collaboration 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 indicate that recent global parton distribution fits provide a good description of the light antiquark sea in the nucleon over the Bjorken-$x$ range $0.03 lesssim x < 0.15$, but overestimate the valence quark distributions as $x to 1$.
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We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a hydrogen target. The polar and azimuthal angular distribution parameters have been extracted over the kinematic range $4.5 < m_{mu mu} < 15$ GeV/c$^2$ (excluding the $Upsilon$ resonance region), $0 < p_T < 4 $ 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 $cos 2 phi$ distribution either to the presence of the transverse-momentum-dependent Boer-Mulders structure function $h_1^perp$ or to QCD effects. The data indicate the presence of both mechanisms. The validity of the Lam-Tung relation in $p+p$ Drell-Yan is also tested.
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.
We report the results of a high-statistics, sensitive search for narrow baryon resonances decaying to $Xi^-pi^-$, $Xi^-pi^+$, $bar{Xi}^+pi^-$, and $bar{Xi}^+pi^+$. The only resonances observed are the well known $Xi^0(1530)$ and $bar{Xi^0}(1530)$. No evidence is found for a state near 1862 MeV, previously reported by NA49cite{NA49}. At the 95% confidence level, we find the upper limit for the production of a Gaussian enhancement with $sigma=7.6$ MeV in the $Xi^-pi^-$ effective mass spectrum to be 0.3% of the number of observed $Xi^0(1530)toXi^-pi^+$. We find similarly restrictive upper limits for an enhancement at 1862 MeV in the $Xi^-pi^+$, $bar{Xi}^+pi^-$, and $bar{Xi}^+pi^+$ mass spectra.
We have made a precise measurement of the inclusive jet cross section at 1800 GeV. The result is based on an integrated luminosity of 92 pb**-1 collected at the Fermilab Tevatron pbarp Collider with the DO detector. The measurement is reported as a function of jet transverse energy (60 GeV < ET < 500 GeV), and in the pseudorapidity intervals |eta|<0.5 and 0.1<eta<0.7. A preliminary measurement of the pseudorapidity dependence of inclusive jet production (eta<1.5) is also discussed. The results are in good agreement with predictions from next-to-leading order (NLO) quantum chromodynamics (QCD). DO has also determined the ratio of jet cross sections at $sqrt{s}$=630 GeV and $sqrt{s}$=1800 GeV ($|eta|leq 0.5$). This preliminary measurement differs from NLO QCD predictions.
MoEDAL is designed to identify new physics in the form of stable or pseudostable highly ionizing particles produced in high-energy Large Hadron Collider (LHC) collisions. Here we update our previous search for magnetic monopoles in Run 2 using the full trapping detector with almost four times more material and almost twice more integrated luminosity. For the first time at the LHC, the data were interpreted in terms of photon-fusion monopole direct production in addition to the Drell-Yan-like mechanism. The MoEDAL trapping detector, consisting of 794 kg of aluminum samples installed in the forward and lateral regions, was exposed to 4.0 fb$^{-1}$ of 13 TeV proton-proton collisions at the LHCb interaction point and analyzed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges equal to or above the Dirac charge are excluded in all samples. Monopole spins 0, 1/2 and 1 are considered and both velocity-independent and -dependent couplings are assumed. This search provides the best current laboratory constraints for monopoles with magnetic charges ranging from two to five times the Dirac charge.
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