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

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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?

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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

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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

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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

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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

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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

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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

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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

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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.

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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

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• 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

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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

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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)