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Quarkonium Production from Fermilab E772/789/866

Jen-Chieh PengUniversity of Illinois

• J/ Ψ, Ψ’ production cross sections at s1/2 = 38.8 GeV– Comparison with theoretical models

• Nuclear effects of J/ Ψ, Ψ’, D and Υ productions

– xF and pT dependences

• Polarization of J/ Ψ and Υ– Test of color-octet models

• J/ Ψ and Υ production ratios for (p+d)/(p+p)– Nuclear effects in p+d– Prospects for extracting dbar/ubar asymmetry

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Meson East Spectrometer(E605/772/789/866)

Open-aperture Closed-aperture Beam-dump (Cu)

J/ΨJ/Ψ

Ψ’

σ(J/ψ) ~ 15 MeV σ(J/ψ) ~ 150 MeVσ(J/ψ) ~ 300 MeV

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J/Ψ production cross sectionsE789 data p + Cu (beam dump) → J/Ψ + x

S1/2 = 38.8 GeV

Calculations using Color Evaporation Model and CTEQ5L parton distributions

No nuclear effects included Nuclear dependence taken into account

total

q-qbar

g-g

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J/Ψ and Ψ’ cross sections

E789 data p + Au → J/Ψ (Ψ’) + x (open aperture)

S1/2 = 38.8 GeV

Large discrepancy between the observed J/Ψ (Ψ’) cross sections and the calculations of color-singlet model

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Nuclear effects of Quarkonium productions

p + A at s1/2 = 38.8 GeV

E772 data σ(p+A) = Aασ(p+N)Strong xF - dependence

Nuclear effects scale with xF, not x2

(should be checked at RHIC/LHC energies)

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Nuclear effects of open-charm productionp + A → D + x at s1/2 = 38.8 GeV

E789 open-aperture, silicon vertex + dihadron detection

h+h- mass spectrum (after vertex cut)

D0 → K- π+

No nuclear effect for D production (at xF ~ 0)

Need to extend the measurements to large xF region

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Comparison between the J/Ψ and Ψ’ nuclear effects

p + A → J/Ψ or Ψ’ at s1/2 = 38.8 GeV

α(xF) is largely the same for J/Ψ and Ψ’ (except at xF ~ 0 region)

‘Universal’ behavior for α(pT) (similar for J/Ψ, Ψ’; weak s1/2 dependence)

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PT - broadening for D-Y, J/Ψ and Υ

• Δ<PT2> for J/Ψ is larger than for D-Y

• Similar behavior for J/Ψ and Υ

Extract <PT2> from fits to data

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E866 - J/Y Nuclear dependence even for Deuterium/Hydrogen

)011.06.1()( 2TTT ppAp )034.052.1()( 2

FFF xxAx From fits to E866/NuSeap + Be, Fe, W data:

A = 1.2

A = 2

Preliminary

Nuclear dependence in deuterium seems to follow the systematics of larger nuclei, but with an effective A smaller than two.

A = 1.35

A = 2

Preliminary

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Polarization of J/Ψ and ΥE866 p + Cu → J/Ψ + x (beam dump) s1/2 = 38.8 GeV

Typical dimuon mass spectrum for various xF, pT, cosθ bins

dσ/dΩ ~ 1 + λcos2θ (extraction of λ for various xF, pT bins)

(hep-ex/030801)

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Polarization of J/Ψ in p + Cu Collision dσ/dΩ ~ 1 + λ cos2θ

(λ=1: transversely polarized, λ = -1: longitudinally polarized λ = 0, unpolarized)

E866 data

hep-ex/030801

• λ is small, but nonzero

• λ becomes negative at large xF

• No strong pT dependence for λ

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Polarization of Υ(1S),Υ(2S+3S) p + Cu →Υ + x (E866 beam-dump data)

Dimuon mass spectrum λ for D-Y, Υ(1S), Υ(2S+3S)

• D-Y is transversely polarized

• Υ(1S) is slightly polarized (like J/Ψ)

• Υ(2S+3S) is transversely polarized!

• Need to measure Ψ’ polarization

Υ(1S)

Υ(2S+3S)

Decay angular distributions

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đ/ū flavor asymmetry and quarkonium production

σDY(p+d) / 2σDY(p+p) ~ (1 + đ/ū) / 2

đ / ū đ - ū

đ / ū at x > 0.15 need to be better determined

(Future Fermilab E906 experiment with 120 GeV proton)

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Is quarkonium production also sensitive to đ/ū asymmetry?

Both gluon-gluon fusion and q-qbar annihilation contribute

Color-evaporation model calculation for p+p at 800, 120 and 50 GeV (CTEQ5L PDF)

CEM predicts dominance of q-qbar annihilation at lower beam energies

total

q-qbar

g-g

800 GeV 120 GeV 50 GeV

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σJ/Ψ(p+d) / 2σJ/Ψ(p+p) at lower beam energies is sensitive to đ/ū asymmetry

CEM calculations for σJ/Ψ(p+d)/2σJ/Ψ(p+p) at 800, 120 and 50 GeV

E866 preliminary

ū = đ

ū ≠ đ

Future J/Ψ measurements at E906 (and at JHF) could provide interesting information on đ/ū asymmetry

800 GeV 120 GeV 50 GeV

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đ/ū asymmetry from Υ production?

Future J/Ψ data could provide much improved statistics

gg

CEM calculation (CTEQ5L)

total

q-qbar

σΥ(p+d)/2σΥ(p+p)

E866 preliminary

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Future prospects

• J/Ψ A-dependence at negative xF will be available from RHIC and LHC

• Open-charm A-dependence data at large xF is crucial for understanding medium effects

• Polarization of quarkonium remains a mystery. Ψ’ polarization data from E866 are being analyzed

• J/Ψ production at lower beam energies (120 GeV Main-Injector and 50 GeV JHF) could provide interesting new information on their production mechanisms as well as đ/ū flavor asymmetry