Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session DF: Mini-Symposium on Hadron Structure and QCD in High Energy Processes I |
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Chair: Naohito Saito, KEK Room: Kohala 3 |
Thursday, October 15, 2009 7:00PM - 7:30PM |
DF.00001: Probing hadron structure by high energy scattering processes Invited Speaker: Protons and neutrons are known to be the building blocks of matter, and also known to be the bound states of quarks and gluons - the partons, whose dynamics is best described by Quantum Chromodynamics (QCD). QCD has been very successful in interpreting and predicting high-energy scattering processes and in extracting the information on short-distance QCD dynamics. In this talk, I will review the progress in probing hadron structure by using high energy scattering processes. In addition to probing parton momentum and helicity distribution functions, I will discuss possibilities and progresses to probe parton's transverse motion and multiparton quantum correlations inside a hadron by using various QCD high energy scattering processes. [Preview Abstract] |
Thursday, October 15, 2009 7:30PM - 7:45PM |
DF.00002: Parton distributions in nuclear systems Wolfgang Bentz, Takuya Ito, Ian Cloet, Anthony Thomas Quark distribution functions in the nuclear medium are calculated by using an effective quark theory of QCD. We mainly concentrate on the flavor dependence of the in-medium quark distributions, and discuss the following interesting applications: (1) The EMC effect for parity-violating deep inelastic scattering of charged leptons on nuclear targets: Here we make predictions for the spin asymmetries, which are relevant to future experiments. (2) An explanation of the NuTeV anomaly in deep inelastic scattering of neutrinos on nuclear targets: Here we point out that the medium modifications of parton distribution functions can explain a large part of the so called NuTeV anomaly, which was observed in 2002 by using an iron target. [Preview Abstract] |
Thursday, October 15, 2009 7:45PM - 8:00PM |
DF.00003: A Study of Quark Energy Loss in p-A Collisions in the Fermilab E906 Experiment Ming Liu It is believed that the jet suppression observed at RHIC is maimly due to parton energy loss. However, our knowledge of the high energy parton energy loss in nuclear matter is very limited and constitues one of the largest gaps in our understanding of the fundamental nuclear interactions at relativistic heavy ion collisions. As a consequency, it also hampers the quantitative determination of the properties of the new state of matter created in the relativistic heavy ion collisions at RHIC. A unique opportunity exists today to perform a benchmark measurement at the Fermilab E906 experiment via an active p+A program. The E906 Dimuon Experiment will use Drell-Yan scattering to measure the anti- quark strcuture of both the nucleon and nucleus, to measure absolute DY cross sections and to exame quark energy loss. The experiment will use the 120GeV proton beam extracted from the Fermilab Main Injector and is scheduled to take data in 2010. In this talk I will briefly discuss our experimental approach how to determine quark energy loss in p+A collisions in the E906 experiment. [Preview Abstract] |
Thursday, October 15, 2009 8:00PM - 8:15PM |
DF.00004: Forward particle production at STAR Andrew Gordon STAR has enhanced its forward acceptance with a new calorimeter (Forward Meson Spectrometer (FMS), $2.5<\eta<4.0$, $0<\phi<2\pi$), first brought online during the 2008 transverse p+p and d+Au RHIC run. This has extended the kinematic reach of asymmetry measurements and enhanced the ability to analyze multi-cluster correlations within an event. Multi-cluster events in the FMS hold the promise of separating Collins and Sivers effects by summing over fragmentation products. As a step towards understanding such data, we have begun to analyze three-cluster events, with a focus on the spin 1 $\omega$ through its decay to a neutral pion and photon. I will discuss the data obtained in 2008 and progress made in the analysis. [Preview Abstract] |
Thursday, October 15, 2009 8:15PM - 8:30PM |
DF.00005: First Observation of W Boson Production at the PHENIX Detector Ken'ichi Karatsu The collisions of polarized protons at the Relativistic Heavy-Ion Collider (RHIC) provide us very good opportunities to study proton spin structure. One of the main goals of the RHIC spin program is to measure the polarization of sea quarks using W boson production. The uncertainty of sea quark polarization still remains large, though the polarizations of valence quarks have been determined well by DIS and Semi-Inclusive DIS. Asymmetry of W boson production is a clean way to measure the sea quark polarization due to the V-A coupling of W bosons to quarks, which means the chirarity of interacting quarks are almost fixed. The flavor identification of sea quarks is also possible by separate measurement of W+/W- production. PHENIX is a detector located at one of the collision points of RHIC, and observes W bosons through the decay to leptons at mid-rapidity ($\vert $eta$\vert <$0.35) and forward rapidity (1.2$<\vert $eta$\vert <$2.4). The first sqrt(s) = 500GeV run at RHIC was held in early 2009 (RHIC Run9), and the first attempt to measure W bosons was performed at PHENIX. In this talk, the current status of the measurement of W bosons at PHENIX mid-rapidity region will be presented. [Preview Abstract] |
Thursday, October 15, 2009 8:30PM - 8:45PM |
DF.00006: The STAR W Physics Program at RHIC Joseph Seele The production of $W^{-(+)}$ bosons in polarized proton-proton collisions provides an ideal tool to study the spin-flavor structure of the proton, namely the polarized and unpolarized light quark sea asymmetries. $W^{-(+)}$ bosons are produced in $\bar{u}+d\,(\bar{d}+u)$ collisions and can be detected through their leptonic decays, $e^{-}+\bar{\nu}_{e}\,(e^{+}+\nu_{e})$, where only the respective charged lepton is measured. The discrimination of $\bar{u}+d (\bar{d}+u)$ quark combinations requires distinguishing between high $p_{T}$ $e^{-(+)}$ through their opposite charge sign, which in turn requires precise tracking information. In spring 2009, STAR recorded its first data set at $\sqrt{s}=500$GeV which allows for a first measurement of the cross section and single helicity asymmetry for $W^{-(+)}$ production at mid-rapidity in polarized proton-proton collisions. The status of the $W^{-(+)}$ production analysis will be presented. [Preview Abstract] |
Thursday, October 15, 2009 8:45PM - 9:00PM |
DF.00007: High-X measurement of the anti-quark distributions in the nucleon: An extension of E866/NuSea measurements Larry Donald Isenhower The quark-level structure of the nucleon has been studied by various methods. Fixed-target Drell-Yan scattering can kinematically select events which specifically probe the target's antiquark distributions and is ideally suited to study these effects. The Fermilab E906 detector is under construction at the NM4 area at Fermilab. It is planned for the experiment to begin taking data in June 2010. E866/NuSea yielded a number of important physics results, including the first measurement of the cross section ratio of proton-proton to proton-deuterium collisions over a large kinematic range, allowing the extraction of the ratio of anti-down to anti-up quarks in the proton. The increase in the Drell-Yan cross section at 120 GeV/c will allow the extension of the range of the light anti-quark ratios to larger Bjorken-x. The apparatus to be used will be discussed, along with the expected impacts these measurements should have on our understanding of the nucleon. [Preview Abstract] |
Thursday, October 15, 2009 9:00PM - 9:15PM |
DF.00008: Measurement of nuclear effects in antiquark distributions Paul Reimer Parton distribution within a free nucleon differ from those of a bound nucleon, an effect first discovered by the EMC collaboration. Most of the data on nuclear dependence is from charged lepton scattering and is sensitive only to the charge-weighted sum of all quarks and antiquarks. Nuclear effects in the quark sea were observed to be different from those in the valence sector by Fermilab E-772; although, with limited statistics. In the context of nuclear convolution models, virtual pion contributions to nuclear structure functions were expected to lead to sizable increases in sea distributions of the nuclei compared with deuterium, an expectation that was convincingly shattered by the E-772 data, calling into question widely believed traditional meson-exchange models of the nucleus. A new experiment, Fermilab E-906/Drell-Yan, will be able to precisely measure nuclear effects in antiquark distributions with higher precision and to larger $x$ than previous experiments. This talk will discuss the nuclear parton distribution measurements proposed by E-906/Drell-Yan. The experiment is being installed at Fermilab and anticipates data collection to begin in summer 2010. [Preview Abstract] |
Thursday, October 15, 2009 9:15PM - 9:30PM |
DF.00009: Design and Kinematical Coverage of FNAL-E906 Spectrometer for Drell-Yan Measurement with 120-GeV Proton Beam Kenichi Nakano One of the major goals of the E906 experiment at FNAL is a precise measurement of the asymmetry between the distributions of $\bar{u}$ and $\bar{d}$ in the nucleon. With the 120 GeV proton beam and the liquid hydrogen and deuterium targets, muon pairs from the Drell-Yan process ($q + \bar{q} \to \gamma^* \to \mu^+ + \mu^-$) are measured. Particularly E906 focuses on the higher Bjorken-$x$ range ($>0.3$) of anti-quark distributions, at which a non-zero and unpredicted negative asymmetry has been observed by the FNAL-E866 experiment although it has a rather large experimental uncertainty. The E906 spectrometer has been designed to effectively collect high-$x$ events. This presentation will show the spectrometer design and its kinematical coverage of expected physics results. [Preview Abstract] |
Thursday, October 15, 2009 9:30PM - 9:45PM |
DF.00010: Probing Quark-Gluon Correlations in the Neutron: Precision Measurements of $d_2^n$ and $g_2^n$ Brad Sawatzky The spin structure function $g_2$ and the higher twist reduced matrix element $d_2$ are fundamentally coupled to the quark-gluon interactions and transverse momentum of the quarks in the nucleon. Unlike most higher-twist processes which can not be separated from associated leading twist terms, $g_2$ contributes to leading order in the longitudinal-polarized lepton scattering on a transversely polarized nucleon. This makes $g_2$ one of the \emph{cleanest} higher twist observables. Within the OPE, the second moment of a linear combination of $g_1$ and $g_2$ may be connected to the higher twist reduced matrix element $d_2$. This quantity has been well studied in Lattice QCD and other theoretical models. While calculations on the proton are in good agreement with data, calculations on the neutron not only have the opposite sign, but are 3--4 sigma away from the world average. This talk presents two Jefferson Lab measurements focused on $g_2$ and $d_2$ for the neutron. The first, E06-014, completed its run in March 2009 and will reduce the uncertainty on the neutron $d_2$ by a projected factor of four. The second experiment to be described, E12-06-121, is targeted to run shortly after the JLab 12\,GeV upgrade is completed (est. 2014--5) and will focus on precision measurements of $g_2^n$ over the region $0.2 < x < 0.95$ and $2.5 < Q^2 < 6$\,GeV$^2/c^2$. [Preview Abstract] |
Thursday, October 15, 2009 9:45PM - 10:00PM |
DF.00011: Measurement of $F_{2}$ and $R=\sigma_{L}/\sigma_{T}$ on Nuclear Targets in the Nucleon Resonance Region Vahe Mamyan Jefferson Lab Experiment E04-001 used the Rosenbluth technique to measure $R=\sigma_{L}/\sigma_{T}$ and $F_{2}$ on nuclear targets. This experiment was part of a multilab effort[1] to investigate quark-hadron duality and the electromagnetic and weak structure of the nuclei in the resonance region. In addition to the studies of quark-hadron duality in electron scattering on nuclear targets, these data will be used as input form factors in future analysis of neutrino data which investigate quark-hadron duality of the nucleon and nuclear axial structure functions. An important goal of this experiment is to provide precise data which to allow a reduction in uncertainties in neutrino oscillation parameters for neutrino oscillation experiments (K2K, MINOS). This inclusive experiment was completed in July 2007 at Jefferson Lab where the Hall C High Momentum Spectrometer detected the scattered electron. Measurements were done in the nuclear resonance region (1 $<$ $W^{2}$ $<$ 4 $GeV^{2}$) spanning the four-momentum transfer range 0.5 $<$ $Q^{2}$ $<$ 4.0 ($GeV^{2}$). Data was collected from four nuclear targets: C, Al, Fe and Cu. After a brief presentation of the physics motivation of the experiment and its experimental and analysis details, the results will be presented. The results of global fit performed on existing world data in this kinematics region will also be presented. \\[4pt] [1] Fermilab Minerva Experiment[http://minerva.fnal.gov/] [Preview Abstract] |
Thursday, October 15, 2009 10:00PM - 10:15PM |
DF.00012: A Confinement Theory for Quarks Carl Case Wilson et al (Phys Rev D, Vol 49, pp 6720; 1994) states that 4 barriers have prohibited a quark confinement theory. These are: (1) diverging confinement potentials, (2) spontaneous chiral symmetry breaking, (3) unlimited growth of running coupling constant in confinement region, and (4) non-perturbative structure of QCD vacuum. This paper identifies a \textit{fiber bundle} (a constant force acting upon each flavor) and \textit{winding numbers} matching one to one with angular momentum quantum numbers. The single constant force spawns a degenerate series of ground states for the quark flavors. Chiral symmetry is broken. Quarks are trapped by color magnetic forces. Gluons, in the form of quantized color magnetic flux bundles, are trapped by encirculating quarks. The flavors behave as a composite particle. Quantized color magnetic flux allows calculation of the running coupling constant. Using Hartree-Fock methods and chiral symmetry breaking leads to Dirac equations for each flavor and anti-flavor (a set of 12 Dirac equations). Mass calculations are presented for observed baryons and mesons. A scaling law for flavor speeds predicts the $b'$ flavor is in the mass range of 110-120 GEV. [Preview Abstract] |
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