Drell Yan experiments: Past and ‘Future‘ Florian Sanftl (Tokyo Tech, Shibata Nucleon11 January 7th 2011, KEK

January 7th 20112Florian Sanftl, Nucleon11 On Today‘s Menu What is the structure of the nucleon? What is the structure of the 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 h 1 ┴ – Transversely polarized beam and/or target?

Early Di-Muon DATA January 7th 2011Florian Sanftl, Nucleon113 Muon Pairs in the mass range 1 < m μμ < 6.7 GeV/c 2 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/dm μμ ≈ / m μμ 5 cm 2 (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.

January 7th 2011Florian Sanftl, Nucleon114 if they had sufficient  What they could have seen if they had sufficient resolution  J/Psi ~3.1GeV  Nobel Prize 1974  Nobel Prize for Richter&Ting in 1974 Data from Fermilab E-866/NuSea Recent Di-Muon Data

January 7th 2011Florian Sanftl, Nucleon115  Also predicted (1+cos 2  ) angular distributions Drell Yan‘s explanation

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 7th 20116Florian Sanftl, Nucleon11

January 7th 2011Florian Sanftl, Nucleon117   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: 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 January 7th 20118Florian Sanftl, Nucleon11 What‘s the Proton?

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 7th 20119Florian Sanftl, Nucleon11

 Gottfried Sum Rule: S G = 1/3 if Charge Symmetry January 7th Florian Sanftl, Nucleon11 The Gottfried SumRule

S G = / New Muon Collaboration (NMC), Phys. Rev. D50 (1994) R1 Extrapolate results over all x (0 < x < 1) < 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 7th Florian Sanftl, Nucleon11 NMC Measurement

 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 7th Florian Sanftl, Nucleon11

  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 7th Florian Sanftl, Nucleon11

January 7th 2011Florian Sanftl, Nucleon1114 Models: An Appetizer LA-LP  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 nucleon Sullivan process in DIS |p> = |p 0 >+  |N  > +  |  > + …  Chiral Models  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 7th Florian Sanftl, Nucleon11

  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 7th Florian Sanftl, Nucleon11

Fermilab E866/NuSea  Data in  1 H, 2 H, and nuclear targets  800 GeV proton beam Fermilab E906/SeaQuest  First data maybe 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 7th Florian Sanftl, Nucleon11

January 7th 2011Florian Sanftl, Nucleon1118 Asymmetry 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 7th 2011Florian Sanftl, Nucleon m 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 MWPC tracking Station 4: Hodoscope array Prop tube tracking Liquid H 2, d 2, and solid targets Station 2 and 3: Hodoscope array Drift Chamber tracking Drawing: T. O’Connor and K. Bailey The E906-Spectrometer

January 7th 2011Florian Sanftl, Nucleon1120 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 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 this spring! Reduce, Reuse, Recycle

January 7th 2011Florian Sanftl, Nucleon1121 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

Alde et al (Fermilab E772) Phys. Rev. Lett (1990) January 7th 2011Florian Sanftl, Nucleon1122  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: Are Antiquark distr. Different?

Alde et al (Fermilab E772) Phys. Rev. Lett (1990) January 7th 2011Florian Sanftl, Nucleon1123  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: Are Antiquark distr. Different? DIS as comparison

January 7th 2011Florian Sanftl, Nucleon1124  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 DIS-EMC effect and Drell-Yan Structure of Nucleonic Matter: Were are Nucleon Pions?

January 7th 2011Florian Sanftl, Nucleon1125 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(  s 2 )] corrections also small Mirkes and Ohnemus, PRD (1995) Chi-Sing Lam and Wu-Ki Tung—basic formula for lepton pair production angular distributions PRD (1978) Generalized Angular Distribtions: Lam-Tung Relation

January 7th 2011Florian Sanftl, Nucleon1126   - Drell-Yan –Violates L-T relation –Large (cos2  ) dependence –Strong with p T  Proton Drell-Yan –Consistent with L-T relation –No (cos2  ) dependence –No p T dependence  With Boer-Mulders function h 1 ┴ :

January 7th 2011Florian Sanftl, Nucleon1127 Survive k T integration k T - dependent, T-even Boer- Mulders Function Sivers Function k T - dependent, NaiveT-odd Short Reminder: Transverse Momentum Dependent DFs

January 7th 2011 Florian Sanftl, Nucleon1128   - Drell-Yan –Violates L-T relation –Large (cos2  ) dependence –Strong with p T  Proton Drell-Yan –Consistent with L-T relation –No (cos2  ) dependence –No p T dependence  With Boer-Mulders function h 1 ┴ : –ν(π-W → µ + µ - X) valence h 1 ┴ (π) * valence h 1 ┴ (p) –ν(pd → µ + µ - X) sea valence h 1 ┴ (p) * sea h 1 ┴ (p)  E-906/SeaQuest will have  Higher statistics  Poorer resolution 

January 7th 2011Florian Sanftl, Nucleon1129 Sivers’ distribution f ? 1T (x, k T )   Single spin asymmetry   Possibly explanation for E704 data   Collins Fragmentation function could also produce such an asymmetry  With Drell-Yan: f ? 1T (x, k T )| DIS = - f ? 1T (x, k T )| 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 Function

January 7th 2011Florian Sanftl, Nucleon1130  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—x beam -x target correlations Experimental issues: p T acceptance,  -/+ decay in flight background –Physics Program cannot be reached by 30 GeV machine (physics program strongly endorsed) Future: Sivers Function

January 7th 2011Florian Sanftl, Nucleon1131 Summary  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 J-Parc or even FNAL)

January 7th 2011Florian Sanftl, Nucleon1132 Additional Material

January 7th 2011Florian Sanftl, Nucleon1133   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 (x 1 or x F ) is shifted   Fit shift in x 1 relative to deuterium  Models: –Galvin and Milana –Brodsky and Hoyer –Baier et al. X1X1 X1X1 Partonic Energy Loss

January 7th 2011Florian Sanftl, Nucleon1134   E866 data are consistent with NO partonic energy loss for all three models   Caveat: A correction must be made for shadowing because of x 1 —x 2 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 p T broadening also will yield information Partonic Energy Loss

January 7th 2011Florian Sanftl, Nucleon1135  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, x 2 < 0.1, to be removed from the data sample Partonic Energy Loss

September 16th 2010Florian Sanftl, HANEC1036 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