1. Study of Antiquarks in the Proton with a High Energy Drell-Yan Experiment Florian Sanftl (D1 Student, Shibata laboratory) @ GCOE Colloquium January 14th 2011, Tokyo Tech

2. What we might learn today:  Light antiquark flavour 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 January 14th 20112Florian Sanftl, GCOE Colloquium Today‘s Menu

3.   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 momentum quarks and antiquarks January 14th 20113Florian Sanftl, GCOE Colloquium What‘s the Proton?

4. In the nucleon:  Sea and gluons are important: –98% of mass; 60% of momentum at Q 2 = 2 GeV 2  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. CTEQ6m In nuclei:  The nucleus is not just protons and neutrons  What is the difference?  Bound system  Virtual mesons affects antiquarks distributions What‘s the distribution of sea quarks? January 14th 20114Florian Sanftl, GCOE Colloquium

5.  Gottfried Sum Rule: S G = 1/3 if Charge Symmetry January 14th 20115Florian Sanftl, GCOE Colloquium The Gottfried SumRule

6. S G = 0.235 +/- 0.026 New Muon Collaboration (NMC), Phys. Rev. D50 (1994) R1 Extrapolate results over all x (0 < x < 1) 0.004 < x < 0.8 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 January 14th 20116Florian Sanftl, GCOE Colloquium NMC Measurement

7.  Naïve Assumption:  NA51 (Drell-Yan)  E866/NuSea (Drell-Yan)  NMC (Gottfried Sum Rule) Knowledge of distributions is data driven  Sea quark distributions are difficult for Lattice QCD Light Antiquark Flavour Asymmetry January 14th 20117Florian Sanftl, GCOE Colloquium

8.   There is a gluon splitting component which is symmetric  –Symmetric sea via pair production from gluons subtracts off –No Gluon contribution at 1 st 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!! Antiquark Flavour Asymmetry: Identifying Process Candidates January 14th 20118Florian Sanftl, GCOE Colloquium

9. January 14th 2011Florian Sanftl, GCOE Colloquium9 Overview of Models LA-LP-98- 56  Pauli Blocking (excess up-valence quarks suppresses creation 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

10.   Meson Cloud in the nucleon Sullivan process in DIS |p> = |p 0 >+  |N  > +  |  > + …  Chiral Models Interaction btw. Goldstone Bosons and valence quarks |u> → |d  + > and |d> → |d  - > Perturbative sea apparently dilutes meson cloud effects at large-x Nonperturbative + perturbative Models January 14th 201110Florian Sanftl, GCOE Colloquium

11.   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?) Something is missing January 14th 201111Florian Sanftl, GCOE Colloquium

12. Detector acceptance chooses x target and x beam. Fixed target -> high x F = x beam – x target Valence Beam quarks at high-x. Sea Target quarks at low/intermediate-x. E906 Spect. Monte Carlo Drell-Yan Scattering: A Direct Gate to Sea-Quarks x target x beam January 14th 201112Florian Sanftl, GCOE Colloquium

13. Fermilab E866/NuSea  Data in 1996-1997  1 H, 2 H, and nuclear targets  800 GeV proton beam Fermilab E906/SeaQuest  First data maybe 2012 2 years of data taking  1 H, 2 H, 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!! 50x statistics!! Fixed Target Beam lines Tevatro n 800 GeV Main Injector 120 GeV Advantage of the 120GeV Injector January 14th 201113Florian Sanftl, GCOE Colloquium

14. January 14th 2011Florian Sanftl, GCOE Colloquium14 Asymmetry extraction @ 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.

15. January 14th 2011Florian Sanftl, GCOE Colloquium15 25m Solid Iron Solid Iron Focusing Magnet, Hadron absorber and beam dump 4.9m Mom. Meas. (KTeV Magnet) Hadron Absorber (Iron Wall) Station 1: Hodoscope array MWDC tracking Station 4: Hodoscope array Prop tube tracking Liquid H 2, d 2, and solid targets (e.g. Fe, Ca, C) Station 2 and 3: Hodoscope array Drift Chamber tracking Drawing: T. O’Connor and K. Bailey The E906-Spectrometer

16. January 14th 2011Florian Sanftl, GCOE Colloquium16 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 2 nd Magnet: KTeV Analysis Magnet Hadron Absorber: Fermilab Rail Head??? Solid Fe Magnet Coils: E-866 SM3 Magnet Shielding blocks: old beamline (Fermilab Today)Fermilab Today Solid Fe Magnet Flux Return Iron: E-866 SM12 Magnet Expect to start collecting data in spring 2011! Reduce, Reuse, Recycle

17. January 14th 2011Florian Sanftl, GCOE Colloquium17 The E906 Collaboration Abilene Christian University Obiageli Akinbule Brandon Bowen Mandi Crowder Tyler Hague Donald Isenhower Ben Miller Rusty Towell Marissa Walker Shon Watson Ryan Wright Academia Sinica Wen-Chen Chang Yen-Chu Chen Shiu Shiuan-Hal Da-Shung Su Argonne National Laboratory John Arrington Don Geesaman* Kawtar Hafidi Roy Holt Harold Jackson David Potterveld Paul E. Reimer* Josh Rubin University of Colorado Joshua Braverman Ed Kinney Po-Ju Lin Colin West Fermi National Accelerator Laboratory Chuck Brown David Christian University of Illinois Bryan Dannowitz Dan Jumper Bryan Kerns Naomi C.R Makins Jen-Chieh Peng KEK Shin'ya Sawada Ling-Tung University Ting-Hua Chang Los Alamos National Laboratory Gerry Garvey Mike Leitch Han Liu Ming Xiong Liu Pat McGaughey University of Maryland Prabin Adhikari Betsy Beise Kaz Nakahara University of Michigan Brian Ball Wolfgang Lorenzon Richard Raymond National Kaohsiung Normal University Rurngsheng Guo Su-Yin Wang RIKEN Yuji Goto Atsushi Taketani Yoshinori Fukao Manabu Togawa Rutgers University Lamiaa El Fassi Ron Gilman Ron Ransome Elaine Schulte Brian Tice Ryan Thorpe Yawei Zhang Texas A & M University Carl Gagliardi Robert Tribble Thomas Jefferson National Accelerator Facility Dave Gaskell Patricia Solvignon Tokyo Institute of Technology Toshi-Aki Shibata Kenichi Nakano Florian Sanftl Shintaro Takeuchi Shou Miyasaka Yamagata University Yoshiyuki Miyachi

18. January 14th 2011Florian Sanftl, GCOE Colloquium18 Contribution by Japanese Collaborators Station3 Drift Chamber:  Active area: 1.7m x 2.3m  Operation Gas Ar:CO 2 (80:20)  Voltage ~-2.6kV, Gas-Gain ~1.E+5, Δx<400um

19. January 14th 2011Florian Sanftl, GCOE Colloquium19 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)