# Presentation: 590916

## Opportunities with Drell-Yan scattering: Probing the sea quark distributions of the nucleon and nucleus

*Paul E. Reimer*
*Using Drell-Yan to probe sea quark distributions*
*What is the structure of the nucleon?*
- Origins of the nucleonic sea:  dbar/ubar in the proton
*What is the structure of nucleonic matter?*
- Nuclear pions and antishadowing of sea quarks
*What are the properties of *_*hot*_* nuclear matter?*
- Parton energy loss in _cold _nuclear matter
*The E906 spectrometer*

## Drell-Yan scattering (Fixed Target):A laboratory for studying sea quark distributions

- Leading Order

- Detector acceptance chooses range in xtarget and xbeam.
- xF = xbeam – xtarget > 0
- high-x Valence *Beam* quarks.
- Low/interm.-x sea *Target* quarks.

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## Fermilab Accelerator Complex:  Fixed Target Program

**Fixed Target Beam lines**

- E866 vs. E906:
- 800 vs. 120 GeV
- Cross section scales as 1/s
*7**£** that of 800 GeV beam*
- Backgrounds (J/ decay)  scale as s
*7**£** Luminosity for same detector rate as 800 GeV beam*
- 50£ statistics!!

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## FNAL E906 Collaboration

- Abilene Christian University
- Donald Isenhower, Mike Sadler,
- Rusty Towell
- Argonne National Laboratory
- John Arrington, Don Geesaman*, Kawtar Hafidi, Roy Holt, Hal Jackson, Paul E. Reimer*,  David Potterveld
- University of Colorado
- Ed Kinney
- Fermi National Accelerator Laboratory
- Chuck Brown
- University of Illinois
- Jen-Chieh Peng
- *Co-Spokespersons

- Los Alamos National Laboratory
- Gerry Garvey,  Mike Leitch,
- Pat McGaughey, Joel Moss
- Rutgers University
- Ron Gilman, Charles Glashausser,
- Xiaodong Jaing, Ron Ransome
- Texas A & M University
- Carl Gagliardi, Bob Tribble,
- Maxim Vasiliev
- Thomas Jefferson National Accelerator Facility
- Dave Gaskell
- Valparaiso University
- Don Koetke

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## FNAL E866/NuSea Collaboration

- Abilene Christian University
- Donald Isenhower, Mike Sadler, Rusty Towell,
- Josh Bush, Josh Willis, Derek Wise
- Argonne National Laboratory
- Don Geesaman, Sheldon Kaufman,
- Naomi Makins, Bryon Mueller, Paul E. Reimer
- Fermi National Accelerator Laboratory
- Chuck Brown, Bill Cooper
- Georgia State University
- Gus Petitt, Xiao-chun He, Bill Lee
- Illinois Institute of Technology
- Dan Kaplan
- Los Alamos National Laboratory
- Melynda Brooks, Tom Carey, Gerry Garvey,
- Dave Lee, Mike Leitch, Pat McGaughey, Joel Moss, Brent Park, Jen-Chieh Peng, Andrea Palounek,
- Walt Sondheim, Neil Thompson

- Louisiana State University
- Paul Kirk, Ying-Chao Wang,  Zhi-Fu Wang
- New Mexico State University
- Mike Beddo, **Ting Chang**, Gary Kyle,
- Vassilios Papavassiliou, J. Seldon,
**Jason Webb**
- Oak Ridge National Laboratory
- Terry Awes, Paul Stankus, Glenn Young
- Texas A & M University
- Carl Gagliardi, Bob Tribble, **Eric Hawker**, Maxim Vasiliev
- Valparaiso University
- Don Koetke, Paul Nord

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## Structure of the nucleon:  What is d-bar/u-bar in the proton? Why?

***Structure of the nucleon:  What is d-bar/u-bar in the proton? Why?***

- Parton Distributions
- Study ratio of cross sections for deuterium to hydrogen
- (In analysis, we use a full Next-to-Leading order cross section calculation with both terms)
- PDF fits are and uncertainties completely dominated by E866.
- E906 will significantly extend these measurements and improve on uncertainty.

**	****	****	**Impact
- Collider/LHC sensitivity for tests of the Standard Model—Background.
- Origins of the Proton Sea—Models explain d-bar  ̧ u-bar.  No theory (model) expects the results seen for x  ̧ 0.3.

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## Structure of nucleonic matter: How do sea quark distributions differ in a nucleus?

***Structure of nucleonic matter: ******How do sea quark distributions differ in a nucleus?***

- Comparison with Deep Inelastic Scattering (DIS)
- Antishadowing not seen in Drell-Yan—Valence only effect?—better statistical precision needed—E906.
-  Intermediate-*x* *sea* PDF’s set by -DIS on iron—unknown nuclear effects.
- What can the sea parton distributions tell us about nuclear binding?

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## Structure of nucleonic matter:  Where are the nuclear pions?

***Structure of nucleonic matter:  ******Where are the nuclear pions?***

- The binding of nucleons in a nucleus is expected to be governed by the exchange of virtual “Nuclear” pions.
- Antiquark enhancement expected from Nuclear Pions.
- Early predictions (Berger and Coester) proved false by Fermilab E772 Drell-Yan data.
*Note that E772 has relatively large uncertainties, especially as x increases.*

- Paul E. Reimer  PANIC05

- 25 Oct 2005

**Notes:**
George Bertsch in Science:  Where are the nuclear pions?  Answers in terms of Gluonic fields

Berger and Coester:  Standard nuclear convolution:  
		F_2^A = \int dy f_N^A(y) F_2^N(x/y) + \int dy f_\pi^A(y) F_2^\pi(x/y) 
	where the F_2’s are the DIS structure functions of the nucleus, nucleon and pion and f_N/\pi^A are the nucleon/pion distribution functions. Other baryons are added as well and all is subject to conservation rules on baryon number and small f’s have total momentum conservation rules

Jung and Miller:  Start with Berger and Coester, but uses different pionic distribution function in nucleus from Ericson and Thomas—points out that Berger and Coester should have used a light cone rather that instant-(time) form nuclear wave function.

Brown et al.: Brown, Rho rescaling—inside a nuclear environment masses of hadron composed of light quarks all decrease with density (at the same rate—see eqn 2.23).  The rescaling is based on a partial restoration of Chiral Symmetry.  This the also effects the coupling strengths.  Based on this, one obtains a modified pion density distribution and follows the convolution model of Berger and Coester.

Dieperink and Korpa: First, range of curves is for various Migdal parameters.  Looks at real and imaginary parts of particle-hole (nucleon-hole?) and \Delta-hole contributions.  Also look at the self-energy of the pion propagator.  The dressed pion propagator included nucleon and \Delta terms.  These affect the pion distribution function (f_pi)

## Parton Energy Loss

***Parton Energy Loss***

- Colored parton moving in strongly interacting media.
- Only initial state interactions are important—*no final state strong interactions*.

_*E866 data are consistent with no energy loss*_
- Treatment of parton propagation length and shadowing are critical
- Johnson *et al*. find 2.2 GeV/fm from the same data
- Energy loss / 1/s—larger at 120 GeV
- Important to understand RHIC data.

- Paul E. Reimer  PANIC05

- 25 Oct 2005

**Notes:**
Brodsky and Hoyer:  Gluon Bremsstrahlung process (A^1/3 / s)

Baier:  Build on Brodsky.  Energy loss depends on characteristic scattering length (A^1/3) and on squared p_T (A^1/3) giving a total A^2/3 / s effect.  Also make predictions for both hot and cold nuclear matter.

Johnson et al.:  2.2 GeV/fm Different treatment of shadowing and parton propagation length

## Drell-Yan Absolute Cross Sections: Proton Structure as x! 1

- Radiative corrections calculations are now finished—small effect.

- Fermilab E906 will add much more precise high-*x* data.

***Drell-Yan Absolute Cross Sections: Proton Structure as x******!****** 1***

- MRST and CTEQ: d/u!0 as x!1

- Reach high-x through *beam proton—*Large xF)large xbeam.
- Proton-Proton—no nuclear corrections—*4u(x) + d(x)*
- Proton-deuterium (cross check) agrees with proton-proton data.
- Parton distributions overestimate cross section.
- Working with CTEQ to incorporate data in global PDF fits.

**PRELIMINARY**

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## E906  Apparatus

**Boost difference between 800 and 120 GeV requires shorter experiment.**
- Previous (E866) spectrometer was over 60m long; E906 spect. is only 26m long
- Fabrication of new coils for M1 magnet (was 14.5 m long new M1 is only 4.8 m)
- Complications with  decays between target and absorber
**Other items:**
- New Station 1 to handle higher rate
- Replace some *very old* scintillators, additional phototubes
**Key to rates:  Beam dump and hadron absorber within M1 Magnet**

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## Drell-Yan Acceptance

- Programmable trigger removes likely J/ events
- Transverse momentum acceptance to above 2 GeV
- Spectrometer could also be used for J/, 0 studies

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## E906 Cost and Schedule

**Fermilab Long Range Schedule—Committed to starting E906 in FY2009**
- Must have minimal impact on instantaneous neutrino production.
- Require slow extraction out of Main Injector.
**Approximate Cost:**
- Magnet coil fabrication:  US$1.4M
- US$0.8M for Spectrometer upgrades
**Funding sources**
- US DOE-Office of Nuclear Physics US$2.0M
- US NSF US$0.3M
- Fermilab support through magnet assembly, electronics, power supplies, *etc*

- Paul E. Reimer  PANIC05

- 25 Oct 2005

## Drell-Yan at Fermilab

***Drell-Yan at Fermilab***

**Fixed-Target Drell-Yan is the ideal way to study the quark sea.**
**What is the structure of the nucleon?**
- d-bar/u-bar at intermediate-*x*

**Answers from Fermilab Drell-Yan**
- Significant increase in physics reach
- Scheduled to run in 2009

- Parton distributions as x!1
**What is the structure of nucleonic matter?**
- Where are the nuclear pions?
- Is antishadowing a valence effect?
**Do partons lose energy?**

**PRELIMINARY**

- Paul E. Reimer  PANIC05

- 25 Oct 2005