The pion parton distribution function in the valence region

The parton distribution function of the pion in the valence region is extracted in a next-to-leading order analysis from Fermilab E-615 pionic Drell-Yan data. The effects of the parameterization of the pion's valence distributions are examined. Modern nucleon parton distributions and nuclear corrections were used and possible effects from higher twist contributions were considered in the analysis. In the next-to-leading order analysis, the high-$x$ dependence of the pion structure function differs from that of the leading order analysis, but not enough to agree with the expectations of pQCD and Dyson-Schwinger calculations.Comment: 5 pages, 4 figures, submitted to Phys. Rev.

What can more Drell-Yan data tell us about QCD?

The Drell-Yan process may be used as a unique probe of the partonic structure of hadrons and of fundamental QCD interactions, providing complementary information to deep inelastic scattering (DIS) measurements. Drell-Yan provides the ability to distinguish between the quarks and antiquarks based on kinematics. Unpolarized Drell-Yan provides access to the longitudinal distributions antiquarks in the proton. Angular distributions are sensitive to the h ⊥ 1, Boer-Mulders, distribution. With the addition of polarization, other transverse momentum distributions (TMDs) can be accessed, including the Sivers’ distribution, f ⊥ 1

Probing transverse-momentum distributions with the Drell-Yan process

The Drell-Yan process offers access, complementary to deep inelastic scattering (DIS) to the transverse-momentum distributions of the quarks within a hadron. When neither the beam nor the target are polarized, the angular distributions of Drell-Yan scattering provide access to the h⊥1 , Boer-Mulders, distribution. With the addition of either a polarized beam or target, other transverse-momentum distributions (TMDs) can be accessed, in particular the Sivers’ distribution, f⊥1'. Existing Boer-Mulders and planned Sivers’ Drell-Yan measurements of these distributions are discussed

Parity violating deep inelastic scattering

Measurements of parity violation in electron scattering have provided a wealth of information on the nucleon, the nucleus and the electroweak interaction. Many of these measurement have been at relatively low four-momentum Exchange (Q). The upgrade of the CEBAF beam energy at Thomas Jefferson National Accelerator Facility (JLab) to a maximum of 12 GeV will expand the kinematics in which PVES measurements can be made to include significantly more of the deep inelastic scattering (DIS) region. To take advantage of this, a new spectrometer, named SoLID, has been proposed. Measurements in the DIS region will provide new information on a variety of topics, including charge symmetry violation, higher twist contributions to proton structure and electroweak coupling constants. To differentiate between these effects, measurements with the SoLID spectrometer will simultaneously cover a large kinematic range in both xBj and Q2

Marine reservoir corrections : St. Helena, South Atlantic Ocean

We present the first marine reservoir age and ∆R determination for the island of St. Helena using marine mollusk radiocarbon dates obtained from an historical context of known age. This represents the first marine reservoir age and ∆R determination in the southern Atlantic Ocean within thousands of kilometers of the island. The depletion of 14C in the shells indicates a rather larger reservoir age for that portion of the surface Atlantic than models indicate. The implication is that upwelling old water along the Namibian coast is transported for a considerable distance, although it is likely to be variable on a decadal timescale. An artilleryman’s button, together with other artifacts found in a midden, demonstrate association of the mollusk shells with a narrow historic period of AD 1815–1835

Non-thermal high-energy emission from colliding winds of massive stars

Colliding winds of massive star binary systems are considered as potential sites of non-thermal high-energy photon production. This is motivated merely by the detection of synchrotron radio emission from the expected colliding wind location. Here we investigate the properties of high-energy photon production in colliding winds of long-period WR+OB-systems. We found that in the dominating leptonic radiation process anisotropy and Klein-Nishina effects may yield spectral and variability signatures in the gamma-ray domain at or above the sensitivity of current or upcoming gamma-ray telescopes. Analytical formulae for the steady-state particle spectra are derived assuming diffusive particle acceleration out of a pool of thermal wind particles, and taking into account adiabatic and all relevant radiative losses. For the first time we include their advection/convection in the wind collision zone, and distinguish two regions within this extended region: the acceleration region where spatial diffusion is superior to convective/advective motion, and the convection region defined by the convection time shorter than the diffusion time scale. The calculation of the Inverse Compton radiation uses the full Klein-Nishina cross section, and takes into account the anisotropic nature of the scattering process. This leads to orbital flux variations by up to several orders of magnitude which may, however, be blurred by the geometry of the system. The calculations are applied to the typical WR+OB-systems WR 140 and WR 147 to yield predictions of their expected spectral and temporal characteristica and to evaluate chances to detect high-energy emission with the current and upcoming gamma-ray experiments. (abridged)Comment: 67 pages, 24 figures, submitted to Ap