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Parton Physics – from Fermilab to RHIC. Mike Leitch – LANL Peter Barnes, Jan Boissevain(Eng), Melynda Brooks, Allan Hansen(PD), Dave Lee, Ming Liu, Pat McGaughey, Joel Moss, Andrea Palounek, Walter Sondheim(Eng), John Sullivan, Hubert vanHecke.

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Parton Physics – from Fermilab to RHIC

Mike Leitch – LANL

Peter Barnes, Jan Boissevain(Eng), Melynda Brooks, Allan Hansen(PD), Dave Lee, Ming Liu, Pat McGaughey, Joel Moss, Andrea Palounek, Walter Sondheim(Eng), John Sullivan, Hubert vanHecke

  • FNAL: parton structure & processes; their modification in nuclei – nucleon flavor asymmetry, DY & J/Y Adep, parton dE/dx …
  • RHIC: QGP and spin physics – muons at PHENIX, QGP via J/Y’s, gluon shadowing
  • PHENIX Run-II & the MVD
  • Silicon-vertex upgrades for open heavy-mesons?

E772 - 1991


A measurement of

Anti-quark asymmetry in the Nucleon Sea

FNAL E866/NuSea



From Draft NSAC Long Range Plan :

“The Structure of the Nuclear Building Blocks”


Nuclear modification of parton level structure & dynamics



Drell-Yan Process





E772 R(W/D)

E866 R(W/Be)


  • Modification of parton momentum distributions of nucleons embedded in nuclei
  • e.g. shadowing – depletion of low-momentum partons. Process dependent?
  • Nuclear effects on parton “dynamics”
  • energy loss of partons as they propagate through nuclei
  • and (associated?) multiple scattering effects

Nuclear Dependence for heavy vector mesons, e.g. J/Ψ, Ψ ',

  • production: color singlet or octet ( ) and color neutralization timescale
  • hadronization time:
  • Coherence length for cc fluctuations:
  • absorption on nucleons or co-movers
  • feed-down from higher mass resonances, e.g. χc



E866/NuSea: 800 GeV p-A (Fermilab)

PRL 84, 3256 (2000)

PT Broadening at 800 GeV

open charm: no A-dep

at mid-rapidity



  • J/Ψ and Ψ’ similar at large xF where they both correspond to a traversing the nucleus
  • but Ψ’ absorbed more strongly than J/Ψ near mid-rapidity (xF ~ 0) where the resonances are beginning to be hadronized in nucleus.

a(pT) shape is independent of xF & same for NA3 at a lower energy


PT Broadening in Drell-Yan and associated Radiative Energy Loss

Baier et al. NP B484, 265 (1987)

E866 – Preliminary


So energy loss associated with observed pT broadening is tiny, e.g. for W:


Quark energy loss in nuclear matter

Johnson, Kopeliovich et al., PRL 86, 4483 (2001)


dE/dx = 0

dE/dx & Shadowing

dE/dx =0.25

Charged hadron and p0 production at PHENIX versus pT for central collisions which, when compared to pQCD models that work well for peripheral collisions, suggests that jet-quenching or energy-loss may be present.

Analysis of our p-A Drell-Yan data (E772 - PRL 64, 2479 (1990) using the Kopeliovich model. Dashed lines with shadowing only; solid lines with parton energy loss of,

dE/dz = 2.32 ± 0.52 ± 0.5 GeV/fm


Theoretical Models for PT Broadening

  • Predicts a different dominant mechanism for pT broadening in DY at RHIC & LHC energies:
    • For lower energy fixed target measurements initial-state multiple scattering is most important
    • But at RHIC & LHC color filtering preserves small dipole configurations which have high-pT and therefore give larger pT broadening

Kopeliovich et al, hep-ph/0110221

“Light Cone Dipole” approach





(longitudinal only)

DY as bremsstrahlung in the target rest frame


J/Ψ Polarization

  • NRQCD based predictions (color octet model) necessary to explain CDF charm cross sections
  • E866 J/Y measurement not in agreement with NRQCD based predictions [Beneke & Rothstein, PRD 54, 2005 (1996)] which give
  • 0.31 < λ < 0.63
  • Complicated by feedown (~40%) from higher mass states.


E866/NuSea – PRL 86, 2529 (2001).

However U(2S+3S), which should not suffer from feeddown, have maximal polarization consistent with the Octet model!


11 Physics Questions for the New Century

The February 2002 issue of Discover magazine based its cover story on the recent 105-page

public draft of the National Research Council Committee on Physics of the Universe report,

Connecting Quarks with the Cosmos: 11 Science Questions for the New Century.

7. Are there new states of matter at ultrahigh temperatures and densities?

The theory of how protons and neutrons form the atomic nuclei of the chemical elements is well developed. At extremely high densities and temperatures, protons and neutrons may "dissolve" into an undifferentiated "soup" of quarks and gluons, which can be probed in heavy-ion accelerators. Still higher densities occur and can be probed in neutron stars and the early universe. The Relativistic Heavy Ion Collider (RHIC) is in operation at the DOE's Brookhaven National Laboratory to study of extremely hot, dense nuclear matter. It collides beams of gold nuclei at energies sufficient to form brief microcosms of the hot, dense soup of elementary particles (quarks and gluons) that previously existed only for the first microseconds after the Big Bang origin of our universe. The experimental data to date have revealed unexpected characteristics and provide the first tantalizing clues of possible quark-gluon plasma formation.

Physicists around the world are interested in the RHIC collisions, which occur thousands of times per second. Each one acts as a microscopic pressure cooker, producing temperatures and pressures more extreme than exist now even in the cores of the hottest stars. In fact, the temperature inside a RHIC collision can exceed 1,000,000,000,000 degrees above absolute zero - about ten thousand times the temperature of the sun. Although RHIC collisions may be super-fast and super-hot, which makes them interesting to physicists, they're too small and too brief to be dangerous.

In a RHIC experiment using the massive PHENIX detector, the impact of two gold nuclei ejected fewer particles transverse to the collision axis than standard theory predicts. This is the first indicator of an exotic state of matter, but much more evidence is needed. By combining this finding with many to come in the next few years, researchers may be able to understand a state of matter that hasn't existed since the dawn of the universe.

From Science Highlights – DOE Office High Energy & Nuclear Physics.


J/Ψ suppression – an effective signature of Quark-gluon plasma (QGP) formation?

  • Color screening in a QGP would destroy pairs before they can hadronize into charmonium
  • But ordinary nuclear effects also absorb or modify J/Ψ’s
  • We need a comprehensive understanding of charmonium production in nuclei
  • Competing effects may be identified in p-A collisions by their strong kinematic dependencies, together with complementary studies of Drell-Yan scattering and open-charm production

NA50 -- Anomalous J/ suppression. Evidence for QGP??


J.C.Peng, LANL

Eskola, Kolhinen, Vogt hep-ph/0104124







E866 (mid-rapidity)


Kopeliovich, Tarasov, & Hufner


Expected statistical errors from a 2-week

d-A run at PHENIX and measurements form E866/NuSea

Gluon Shadowing for J/Ψ’s – predictions?

  • In PHENIX μ acceptance for Au-Au collisions?
  • Eskola… : ~ 0.8
  • Kopeliovich… : ~ 0.4
  • Strikman…[hep-ph/9812322] : ~ 0.4

PHENIX μ+μ- (Au)


Charmonium at PHENIX - Coming soon!


  • PHENIX: South Muon & Electrons taking first data now (Au-Au over; p-p in progress)
  • North Muon in 2003 (after shutdown)
  • d-A collisions: strong consensus building; hopefully coming soon.




* Min-bias/RHIC-year for a = .92 (Nagle & Brooks)

** E866 nuclear dependence data only *** Upsilons from E772


From Draft NSAC Long Range Plan :

“The Structure of the Nuclear Building Blocks”


m Physics Program - High-pT Single m’s

  • High-pT single-m’s come from heavy mesons, i.e. D’s or B’s
  • These mesons are produced primarily through gluon fusion and thus are sensitive to the gluon structure functions.
  • In p-A collisions the shadowing of gluons can be studied


  • With polarized beams the gluon polarization, G, can be studied.
  • W±m±νm can be identified by high-pT single-m’s and W+/W- can be used to measure the flavor asymmetry in the nucleon sea including its spin decomposition


phenix muliplicity vertex detector mvd
PHENIX Muliplicity & Vertex Detector (MVD)
  • dN/dη for charged particles over very broad rapidity range
  • Provides s(Zvertex) < 2 mm for the rest of PHENIX, muon spectrometer needs vertex to maintian good J/Y mass resolution
  • Reaction plane for in- & out-of-plane comparisons for various signals in PHENIX, e.g. J/Y suppression, “jet-quenching”.

PHENIX w/o MVD : | η | < 0.35

dN/dη from MVD

for 125 Au-Au events

dN/dη from MVD

for one Au-Au event


PHENIX Silicon Vertex Upgrade

  • Matching tracklets in silicon to tracks in m-arms
  • Momentum measurement
  • displaced vertex

And also detect h in silicon

LANL LDRD supporting

R&D for us ($250K/yr)

  • Gluon polarization in proton
  • Nuclear dependence of open charm:
    • Gluon shadowing
    • Charm cross section
    • To understand J/Y in A-A collisions

Accurate projection to collision vertex

=> close, thin detector


History of the LANL HENP Program

E772 (1987 - …)

DY, J/Y, Y’, U Nuclear Dep.

Spokesman: Moss

NA44 (1990 - …)

Bose-Einstein Correlations,…

Jacak, Sullivan,van Hecke

E789 (1990 - …)

sbb, sJ/Y, D0 Nuclear Dep.

Spokesman: Peng

SSC (GEM,SLD 1990 - …)

GEM Silicon tracker

(Brooks, Lee, Palounek)

E866/NuSea (1996 - …)

, J/Y, Y’, Nuclear Dep.

Spokesmen: Garvey,McGaughey,Leitch

PHENIX (1990 - …)

Muons: J/Y, single-m, open-charm, spin, p-A, QGP


E906 (2006?)

at high-x, parton dE/dz

Spokesman: Reimer (ANL)


PHENIX Timetable





Jan 26












Prepare Sm

Sm with Au-Au beams


Run Nm & Sm

1stmm physics (J/ suppression & single m’s)

2-Arm physics

Install Nm chambers

Build Nm chambers

Install Nm FEE

Start Building Nm FEE

Complete Nm FEE

Fix Sm


Prepare MVD



Finish MVD

1st MVD physics (dN/dη, vertex & fluctuations)


Au-Au Beams


Si vertex upgrade R&D for charm physics

In FY2003 d-A, p-p and Au-Au collisions are all likely


The North-m Arm

  • North-m arm advantages:
  • Superior arm with more kick, better momentum resolution & better mass resolution than South (for ’s: sNorth= 190 MeV compared to sSouth = 240 MeV )
  • While J/’s should melt in a QGP, ’s are smaller and should not, so a well separated  peak (separation of 1S &2S is 563 MeV) is critical
  •  mesons may be broadened, shifted in mass or even enhanced in a QGP. With its 10o (as opposed to 12o for South) minimum theta, the North-m arm has much larger acceptance for ’s which tend to decay into m’s are small angles.
  • The mID is directly behind the tracking volume (in contrast with the South-m arm which has a large gap). This should help reduce backgrounds and improve matching between tracking and mID.
  • Two m-arms:
  • Doubles the counting rate
  • Allows measuring forward and backwardm+m- simultaneously, i.e. negative & positive rapidity at the same time. Important for the study of formation-time effects in p-A.
  • Allows for events with one m in each arm, e.g. mid-rapidity ’s
  • Required for W±m±νmspin measurements since the Z0m+m- backgrounds can be determined only using two arms.

South m arm

North m arm



    • Barnes (1/2 on EDM, return-to-research funding ended last year) : chamber construction, PHENIX physics.
    • Brooks: m-tracking detector council representative, m-software leader, m-electronics, PHENIX Institutional Board representative.
    • Garvey(retired) : E866, eRHIC, advisor to BNL management & John Browne, RHIC program supporter but no direct involvement in PHENIX.
    • Hansen (postdoc) : hadron physics, MVD electronics & software.
    • Lee : chamber construction manager, silicon-vertex upgrade.
    • Leitch: HENP team leader , m-electronics, m-calibration system, m-software, J/ suppression, p-A, shadowing, parton energy-loss, E866 spokesman, PHENIX Executive Council
    • McGaughey : m-electronics, m-calibration system, m-software, parton enegy-loss, silicon-vertexupgrade LDRD spokesman, former E866 spokesman, E906.
    • Liu (newest staff member) : m-electronics, m-software, online monitoring, spin physics
    • Mischke(now off the program) : was m-electronics manager & is now expert consultant.
    • Moss : spin physics, parton energy-loss, silicon-vertex upgrade, APS DNP chair.
    • Peng (1/4 time on EDM; leaving LANL in Jan) : E866 physics, parton energy-loss, p-A and parton physics at RHIC, PHENIX upgrades, extensive long-range planning work, FNAL/E906, JHF.
    • Silvermyr: new postdoc (April 2002).
    • Sullivan :MVD PHENIX detector council representative, hadron physics, MVD electronics & software.
    • Van Hecke :MVD ancillary systems & DAQ, hadron physics
  • Engineers
    • Boissevain (1/4) : MVD constuction, m layout engineering.
    • Sondheim (funded by construction $’s) : PHENIX mlead engineer & system integration