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Study ofStudy of AntiquarksAntiquarks inin thethe ProtonProton with a Highwith a High Energy Energy
Drell-YanDrell-Yan ExperimentExperiment
Florian Sanftl (D1 Student, Shibata laboratory)Florian Sanftl (D1 Student, Shibata laboratory)@ GCOE Colloquium@ GCOE Colloquium
January 14th 2011, Tokyo TechJanuary 14th 2011, Tokyo Tech
What we might learn today: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 2011January 14th 2011 22Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
Today‘s MenuToday‘s Menu
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 2011January 14th 2011 33Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
What‘s the Proton?What‘s the Proton?
In the nucleon:In the nucleon: Sea and gluons are important:Sea and gluons are important:
– 98% of mass; 60% of momentum at Q2 = 2 GeV2
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 What‘s the distribution of sea quarks?quarks?
January 14th 2011January 14th 2011 44Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
Gottfried Sum Rule:Gottfried Sum Rule:
SSGG = 1/3 if = 1/3 if
3
1
3
2
3
1 1
0
1
022
dxdu
x
dxFFS
np
G Charge Symmetry
du
du
January 14th 2011January 14th 2011 55Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
The Gottfried SumRuleThe Gottfried SumRule
SSGG = 0.235 +/- 0.026 = 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 2011January 14th 2011 66Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
NMC MeasurementNMC Measurement
Naïve Assumption: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 AsymmetryLight Antiquark Flavour Asymmetry
January 14th 2011January 14th 2011 77Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
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!!
Antiquark Flavour Asymmetry: Antiquark Flavour Asymmetry: Identifying Process CandidatesIdentifying Process Candidates
January 14th 2011January 14th 2011 88Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
January 14th 2011January 14th 2011 Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium 99
Overview of ModelsOverview of Models
LA-LP-98-56
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
Meson Cloud in the nucleon
Sullivan process in DIS
|p> = |p0>+ |N> + |> + …
Chiral ModelsInteraction btw. Goldstone Bosons and valence quarks
|u> → |d+> and |d> → |d->
Perturbative sea
apparently dilutes
meson cloud effects at large-x
Nonperturbative + perturbative Nonperturbative + perturbative ModelsModels
January 14th 2011January 14th 2011 1010Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
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 missingSomething is missing
January 14th 2011January 14th 2011 1111Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
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
Drell-Yan Scattering:Drell-Yan Scattering:A Direct Gate to Sea-Quarks A Direct Gate to Sea-Quarks
xtarget xbeam
January 14th 2011January 14th 2011 1212Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
Fermilab E866/NuSeaFermilab E866/NuSea Data in 1996-1997
1H, 2H, and nuclear targets 800 GeV proton beam
Fermilab E906/SeaQuestFermilab E906/SeaQuest First data maybe 2012
2 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!!50x statistics!!
Fixed
Target
Beam l
ines
Tevatron 800 GeVMain
Injector 120 GeV
Advantage of the 120GeV Injector Advantage of the 120GeV Injector
January 14th 2011January 14th 2011 1313Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium
January 14th 2011January 14th 2011 Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium 1414
Asymmetry extraction @ E906 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.
January 14th 2011January 14th 2011 Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium 1515
25m
Solid IronSolid 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 H2, d2, 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-SpectrometerThe E906-Spectrometer
January 14th 2011January 14th 2011 Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium 1616
• 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
Expect to start collecting data in spring 2011!
Reduce, Reuse, RecycleReduce, Reuse, Recycle
January 14th 2011January 14th 2011 Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium 1717
The E906 CollaborationThe E906 CollaborationAbilene 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
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
January 14th 2011January 14th 2011 Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium 1818
Contribution by Japanese Contribution by Japanese CollaboratorsCollaborators
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
January 14th 2011January 14th 2011 Florian Sanftl, GCOE ColloquiumFlorian Sanftl, GCOE Colloquium 1919
SummarySummary
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)