Study of Antiquarks in the Proton with a High Energy Drell -Yan Experiment

1. Study ofAntiquarksintheProtonwith a HighEnergyDrell-YanExperiment Florian Sanftl (D1 Student, Shibata laboratory)@ GCOE ColloquiumJanuary 14th 2011, Tokyo Tech

2. Today‘s Menu What we might learn today: • Light antiquarkflavour Asymmetry in the Proton • Past Measurements • Introduction of Asymmetry Models • The Drell-Yan Process as a tool to probe this Flavour Asymmetry • The E906-Experiment Florian Sanftl, GCOE Colloquium

3. What‘sthe Proton? • Three “Valence” quarks • 2 “up” quarks • 1 “down” quark • Bound together by gluons • Gluons can split into quark-antiquark pairs • Forms large “sea” of low momentumquarks and antiquarks Florian Sanftl, GCOE Colloquium

4. What‘sthedistributionofseaquarks? In the nucleon: • Sea and gluons are important: • 98% of mass; 60% of momentum at Q2 = 2 GeV2 CTEQ6m • Not just three valence quarks and QCD. Shown by E866/NuSea d-bar/u-bar data • What are the origins of the sea? • Significant part of LHC beam. In nuclei: • The nucleus is not just protons and neutrons • What is the difference? • Bound system • Virtual mesons affects antiquarks distributions Florian Sanftl, GCOE Colloquium

5. The Gottfried SumRule • Gottfried Sum Rule: SG = 1/3 if Charge Symmetry Florian Sanftl, GCOE Colloquium

6. NMC Measurement 0.004 < x < 0.8 SG = 0.235 +/- 0.026 New Muon Collaboration (NMC), Phys. Rev. D50 (1994) R1 Extrapolate results over all x (0 < x < 1) Nuclear shadowing (double scattering of virtual photon from both nucleons in deuteron) ~ 4-10% effect on Gottfried sum  disagreement with naive calculation of GSR remains Florian Sanftl, GCOE Colloquium

7. Light Antiquark FlavourAsymmetry • Naïve Assumption: • NMC (Gottfried Sum Rule) • NA51 (Drell-Yan) • E866/NuSea (Drell-Yan) • Knowledge of distributions is data driven • Sea quark distributions are difficult for Lattice QCD Florian Sanftl, GCOE Colloquium

8. Antiquark FlavourAsymmetry: IdentifyingProcessCandidates • There is a gluon splitting component which is symmetric • Symmetric sea via pair production from gluons subtracts off • No Gluon contribution at 1st order in s • Nonperturbative models are motivated by the observed difference • A proton with 3 valence quarks plus glue cannot be right at any scale!! Florian Sanftl, GCOE Colloquium

9. LA-LP-98-56 Overviewof Models • Pauli Blocking(excess up-valence quarks suppressescreation up-anti-up-pair) • Meson Cloud in the nucleon-Sullivan Process in DIS: • Chiral Quark models – effective Lagrangians: • Instantons (so far no kinematic dependence known…) • Statistical Parton Distributions Florian Sanftl, GCOE Colloquium

10. Nonperturbative + perturbative Models • Chiral ModelsInteraction btw. Goldstone Bosons and valence quarks • |u> → |d+> and |d> → |d-> • Meson Cloud in the nucleon Sullivan process in DIS |p> = |p0>+  |N> + |> + … Perturbative sea apparently dilutes meson cloud effects at large-x Florian Sanftl, GCOE Colloquium

11. Something ismissing • All non-perturbative models predict large asymmetries at high x. • Are there more gluons and therefore symmetric anti-quarks at higher x? • Does some mechanism like instantons have an unexpected x dependence? (What is the expected x dependence for instantons in the first place?) Florian Sanftl, GCOE Colloquium

12. xtarget xbeam Drell-Yan Scattering:A Direct Gate to Sea-Quarks Detector acceptance chooses xtarget and xbeam. • Fixed target -> high xF = xbeam – xtarget • Valence Beam quarks at high-x. • Sea Target quarks at low/intermediate-x. E906 Spect. Monte Carlo Florian Sanftl, GCOE Colloquium

13. Main Injector 120 GeV Tevatron 800 GeV Advantage ofthe 120GeV Injector Fermilab E866/NuSea • Data in 1996-1997 • 1H, 2H, and nuclear targets • 800 GeV proton beam • Fermilab E906/SeaQuest • First data maybe 20122 years of data taking • 1H, 2H, and nuclear targets • 120 GeV proton Beam • Cross section scales as 1/s • 7x that of 800 GeV beam • Backgrounds, primarily from J/ decays scale as s • 7x Luminosity for same detector rate as 800 GeV beam • 50x statistics!! Fixed Target Beam lines Florian Sanftl, GCOE Colloquium

14. Asymmetryextraction @ E906 • E906/Drell-Yan will extend these measurements and reduce statistical uncertainty. • E906 expects systematic uncertainty to remain at approx. 1% in cross section ratio. Florian Sanftl, GCOE Colloquium

15. 4.9m The E906-Spectrometer Station 4: Hodoscope array Prop tube tracking Station 2 and 3: Hodoscope array Drift Chamber tracking Station 1: Hodoscope array MWDC tracking Solid IronFocusing Magnet, Hadron absorber and beam dump Mom. Meas. (KTeV Magnet) Hadron Absorber (Iron Wall) 25m Liquid H2, d2, and solid targets (e.g. Fe, Ca, C) Drawing: T. O’Connor and K. Bailey Florian Sanftl, GCOE Colloquium

16. Reduce, Reuse, Recycle Expect to start collecting data in spring 2011! • St. 4 Prop Tubes: Homeland Security via Los Alamos • St. 3 & 4 Hodo PMT’s: E-866, HERMES, KTeV • St. 1 & 2 Hodoscopes: HERMES • St. 2 & 3Minus- tracking: E-866 • St. 3Plus: NEW from Tokyo Tech!!! • St. 2 Support Structure: KTeV • Target Flasks: E-866 • Cables: KTeV • 2nd Magnet: KTeV Analysis Magnet • Hadron Absorber: Fermilab Rail Head??? • Solid Fe Magnet Coils: E-866 SM3 Magnet • Shielding blocks: old beamline (Fermilab Today) • Solid Fe Magnet Flux Return Iron: E-866 SM12 Magnet Florian Sanftl, GCOE Colloquium

17. The E906 Collaboration Fermi National Accelerator Laboratory Chuck BrownDavid Christian University of Illinois Bryan DannowitzDan JumperBryan KernsNaomi C.R MakinsJen-Chieh Peng KEK Shin'ya Sawada Ling-Tung University Ting-Hua Chang Los Alamos National Laboratory Gerry GarveyMike LeitchHan LiuMing Xiong LiuPat McGaughey University of Maryland Prabin AdhikariBetsy BeiseKaz Nakahara University of Michigan Brian BallWolfgang LorenzonRichard Raymond National Kaohsiung Normal University Rurngsheng GuoSu-Yin Wang RIKEN Yuji GotoAtsushi TaketaniYoshinori FukaoManabu Togawa Rutgers University Lamiaa El FassiRon GilmanRon RansomeElaine SchulteBrian TiceRyan ThorpeYawei Zhang Texas A & M University Carl GagliardiRobert Tribble Thomas Jefferson National Accelerator Facility Dave GaskellPatricia Solvignon Tokyo Institute of Technology Toshi-Aki Shibata Kenichi Nakano Florian Sanftl Shintaro Takeuchi Shou Miyasaka Yamagata University Yoshiyuki Miyachi Abilene Christian University Obiageli AkinbuleBrandon BowenMandi CrowderTyler HagueDonald IsenhowerBen MillerRusty TowellMarissa WalkerShon WatsonRyan Wright Academia Sinica Wen-Chen ChangYen-Chu ChenShiu Shiuan-HalDa-Shung Su Argonne National Laboratory John ArringtonDon Geesaman*Kawtar HafidiRoy HoltHarold JacksonDavid PotterveldPaul E. Reimer*Josh Rubin University of Colorado Joshua BravermanEd KinneyPo-Ju LinColin West Florian Sanftl, GCOE Colloquium

18. ContributionbyJapaneseCollaborators • Station3 Drift Chamber: • Active area: 1.7m x 2.3m • Operation Gas Ar:CO2 (80:20) • Voltage ~-2.6kV, Gas-Gain ~1.E+5, Δx<400um Florian Sanftl, GCOE Colloquium

19. Summary • The structure of the proton is far away from being completely understood • The mechanisms causing a Flavour Asymmetry of the Nucleon Sea can be of different origin and are not yet completely understood-> More precise data is needed • SeaQuest is the latest high rate Drell-Yan experiment allowing direct access to the Antiquark Flavour Asymmetry of the Proton • The SeaQuest spectrometer might be extended to perform polarized Drell-Yan measurements (@BNL, J-Parc or even FNAL) Florian Sanftl, GCOE Colloquium