Drell Yan experiments: Past and ‘Future‘ Florian Sanftl (Tokyo Tech, Shibata laboratory) @...

Drell Yan experiments:Drell Yan experiments:Past and ‘Future‘Past and ‘Future‘

Florian Sanftl (Tokyo Tech, Shibata laboratory)Florian Sanftl (Tokyo Tech, Shibata laboratory)@ Nucleon11@ Nucleon11

January 7th 2011, KEKJanuary 7th 2011, KEK

January 7th 2011January 7th 2011 22Florian Sanftl, Nucleon11Florian Sanftl, Nucleon11

On Today‘s MenuOn Today‘s Menu

What is the structure of the What is the structure of the nucleon?nucleon?– What is d-bar/u-bar?– What are the origins of the sea

quarks?– What is the high-x structure of

the proton?

Answers from Fermilab E906/Drell-Yan– Significant increase in physics reach over previous

Drell-Yan experiments– US DOE/Nuclear Physics funded spectrometer

What is the structure of nucleonic matter?– Where are the nuclear pions?– Is anti-shadowing a valence effect?

What is the transverse Structure of the proton?– Lam-Tung relation and Boer-Mulders h1

┴

– Transversely polarized beam and/or target?

Early Di-Muon DATAEarly Di-Muon DATA

January 7th 2011January 7th 2011 Florian Sanftl, Nucleon11Florian Sanftl, Nucleon11 33

Muon Pairs in the mass range 1 < mμμ < 6.7 GeV/c2 have been observed in collisions of high-energy protons with uranium nuclei. At an incident energy of 29 GeV, the cross section varies smoothly as dσ/dmμμ ≈ 10-32 / mμμ

5 cm2 (GeV/c)-2 and exhibits no resonant structure. The total cross section increases by a factor of 5 as the proton energy rises from 22 to 29.5 GeV.


What they could have seen if they if they had sufficient had sufficient resolution

J/Psi Peak @ J/Psi Peak @ ~3.1GeV~3.1GeV

Nobel PrizeNobel Prize for Richter&Ting in 19741974

Data from Fermilab E-866/NuSea

Recent Di-Muon DataRecent Di-Muon Data


Also predicted Also predicted (1+cos(1+cos22) ) angular distributionsangular distributions

Drell Yan‘s explanationDrell Yan‘s explanation

Detector acceptance chooses xDetector acceptance chooses xtargettarget and x and xbeambeam

• 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



Next-to-leading order diagrams complicate the picture

These diagrams are responsible for 50% of the measured cross section

Intrinsic transverse momentum of quarks (although a small effect, > 0.8)

Still holds reasonably well Actual data analysis used full Next-to-

Leading Order calculation

Drell-Yan Scattering:Drell-Yan Scattering:A Direct Gate to Sea-Quarks A Direct Gate to Sea-Quarks

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


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?


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


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


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


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



Models: An AppetizerModels: An Appetizer

LA-LP-98-56

Chiral Quark models—effective Lagrangians

Meson Cloud in the nucleon—Sullivan process in DIS

Instantons

Statistical Parton Distributions

Antiquarks in spin 0 object → No net spin

Pauli Blocking:Excess of up-quarks permits creation of up-anti-up-pairs

Meson Cloud in the nucleonMeson Cloud in the nucleon

Sullivan process in DIS|p> = |p0>+ |N> + |> + …

Chiral ModelsChiral 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


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


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



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.


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

MWPC tracking

Station 4:

Hodoscope array

Prop tube tracking

Liquid H2, d2, and

solid targets

Station 2 and 3:

Hodoscope array

Drift Chamber tracking

Drawing: T. O’Connor and K. Bailey

The E906-SpectrometerThe E906-Spectrometer


• 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 Japanese Collaborators• 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 this spring!

Reduce, Reuse, RecycleReduce, Reuse, Recycle

http://www.fnal.gov/pub/today/archive_2010/today10-09-24.html


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

Alde et al (Fermilab E772) Phys. Rev. Lett. 64 2479 (1990)


Comparison with Deep Inelastic Scattering (DIS)

EMC: Parton distributions of bound and free nucleons are different.

Antishadowing not seen in Drell-Yan—Valence only effect

Structure of Nucleonic Matter:Structure of Nucleonic Matter:Are Antiquark distr. Different?Are Antiquark distr. Different?

Alde et al (Fermilab E772) Phys. Rev. Lett. 64 2479 (1990)


Comparison with Deep Inelastic Scattering (DIS)

EMC: Parton distributions of bound and free nucleons are different.

Antishadowing not seen in Drell-Yan—Valence only effect

Structure of Nucleonic Matter:Structure of Nucleonic Matter:Are Antiquark distr. Different?Are Antiquark distr. Different?

DIS as comparison


The binding of nucleons in a nucleus is expected to be governed by the exchange of virtual “Nuclear” mesons.

No antiquark enhancement seen in Drell-Yan (Fermilab E772) data.

Contemporary models predict large effects to antiquark distributions as x increases.

Models must explain both Models must explain both DIS-EMC effect and Drell-YanDIS-EMC effect and Drell-Yan

Structure of Nucleonic Matter:Structure of Nucleonic Matter:Were are Nucleon Pions?Were are Nucleon Pions?


Structure function formalism Derived in analogy to DIS Independent of Drell-Yan and parton

“models” Showed same relations follow as a general

consequence of the quark-parton model

Lam-Tung relation Derived in analogy to Colin-Gross relation of DIS Unaffected by O(s) (NLO) corrections

NNLO [O(s2)] corrections also small Mirkes and Ohnemus, PRD

51 4891 (1995)

Chi-Sing Lam and Wu-Ki Tung—basic formula for lepton pair production angular distributions PRD 18 2447 (1978)

Generalized Angular Generalized Angular Distribtions: Lam-Tung RelationDistribtions: Lam-Tung Relation


-- Drell-Yan Drell-Yan

– Violates L-T relation

– Large (cos2) dependence

– Strong with pT

Proton Drell-Yan

– Consistent with L-T relation

– No (cos2) dependence

– No pT dependence With Boer-Mulders function h1

┴:


1ˆ

Tf T TS (p×k )

1( ) Lh T T Lk s S

1ˆ h T Ts (p×k )

Survive kT integration

kT - dependent, T-even

1Lg L LS s

Boer-Mulders Function

Sivers Function

kT - dependent, NaiveT-odd

Short Reminder: Transverse Short Reminder: Transverse Momentum Dependent DFsMomentum Dependent DFs


-- Drell-Yan Drell-Yan

– Violates L-T relation

– Large (cos2) dependence

– Strong with pT

Proton Drell-Yan

– Consistent with L-T relation

– No (cos2) dependence

– No pT dependence With Boer-Mulders function h1

┴:

–ν(π-W → µ+µ-X)

valence h1┴(π) * valence h1

┴(p)

–ν(pd → µ+µ-X)

valence h1┴(p) * seasea h1

┴(p) E-906/SeaQuest will have

Higher statistics Poorer resolution


Sivers’ distribution f?1T(x, kT)

Single spin asymmetry

Possibly explanation for E704 data Collins Fragmentation function could also

produce such an asymmetry

With Drell-Yan: f?1T(x, kT)|DIS = - f?1T(x, kT)|D-Y

fundamental prediction of QCD (goes to heart of gauge formulation of field theory)

With transversely polarized target one measures sea quarks Sea quark effects might be small Eventually transversely polarized beam at Fermilab, J-PARC????

TMD Future: Sivers FunctionTMD Future: Sivers Function


Drell-Yan—JPARC– Initial phase of JPARC is 30 GeV—sufficient only for J/ studies, no

Drell-Yan (no phase space for events above J/)– JPARC Phase II—50 GeV

• great possibilities for polarized Drell-Yan• Berger criteria for nuclear targets—insufficient energy for heavy A• No partonic energy loss studies—xbeam-xtarget correlations• Experimental issues: pT acceptance, -/+ decay in flight background

– Physics Program cannot be reached by 30 GeV machine

(physics program strongly endorsed)

Future: Sivers FunctionFuture: Sivers Function


SummarySummary

The structure of the proton and nuclear matter 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

Drell Yan serves as a laboratory to access many different kinds of Physics

Results so far are not yet enough to gain full understanding of the underlying phyics mechanism

The SeaQuest spectrometer might be extended to perform polarized Drell-Yan measurements (@BNL, J-Parc or even FNAL)


Additional MaterialAdditional Material


An understanding of partonic energy loss in both cold and hot nuclear matter is paramount to elucidating RHIC data.

Pre-interaction parton moves through cold nuclear matter and looses energy.

Apparent (reconstructed) kinematic values (x1 or xF) is shifted

Fit shift in x1 relative to deuterium

Models:– Galvin and Milana

– Brodsky and Hoyer

– Baier et al.

X1X1

Partonic Energy LossPartonic Energy Loss


E866 data are consistent with NO partonic energy loss for all three models

Caveat: A correction must be made for shadowing because of x1—x2 correlations– E866 used an empirical

correction based on EKS fit do DIS and Drell-Yan.

Treatment of parton propagation length and shadowing are critical Johnson et al. find 2.7 GeV/fm (≈1.7 GeV/fm after QCD vacuum effects) Same data with different shadowing correction and propagation length

Better data outside of shadowing region are necessary. Drell-Yan pT broadening also will yield information



Shift in x / 1/s– larger at 120 GeV

Ability to distinguish between models

Measurements rather than upper limits

E906 will have sufficient statistical precision to allow events within the shadowing region, x2 < 0.1, to be removed from the data sample


September 16th 2010September 16th 2010 Florian Sanftl, HANEC10Florian Sanftl, HANEC10 3636

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

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Drell Yan experiments: Past and ‘Future‘ Florian Sanftl (Tokyo Tech, Shibata laboratory) @...

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