Dimuon Production with High Energy Proton Beams

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Dimuon Production with High Energy Proton
Beams
Jen-Chieh Peng, University of Illinois
KEK, Jan. 11, 2008

• Highlights of results from Fermilab E772, E789
  and E866 dimuon experiments
• What have we learned?
• Future prospects of Fermilab E906 and J-PARC
  dimuon experiments
• What do we hope to learn?

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A Brief History
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First Dimuon Experiment
Lederman et al. PRL 25 (1970) 1523

• Experiment originally designed to search for
  neutral weak boson (Z0)
• Miss the J/? signal !

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Lepton-pair production is a powerful tool for
finding new quarks/particles
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Lepton-pair production also provides unique
information on parton distributions
Probe antiquark in nucleon
Probe antiquark in pion
Probe antiquark in antiproton
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Meson East Spectrometer
(E605/772/789/866)
Open-aperture
Closed-aperture
Beam-dump (Cu)
J/?
J/?
?
s(J/?) 15 MeV
s(J/?) 150 MeV
s(J/?) 300 MeV
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Physics with High-Mass Dimuons
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Deep-Inelastic Scattering versus Drell-Yan
Drell-Yan
DIS
Drell-Yan cross sections are well described by
NLO calculations
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Modification of Parton Distributions in Nuclei
EMC effect observed in DIS
F2Fe / F2D
X
F2 contains contributions from quarks and
antiquarks
How are the antiquark distributions modified in
nuclei?
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The Drell-Yan Process
The x-dependence of can be
directly measured
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PRL 83 (1999) 2304
The Drell-Yan p-A measurement can be extended to
lower x at RHIC
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Is in the proton?

Test of the Gottfried Sum Rule
New Muon Collaboration (NMC) obtains
SG 0.235 0.026
( Significantly lower than 1/3 ! )
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The Drell-Yan Process
The x-dependence of can be
directly measured
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Fermilab E866 Measurements
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Fermilab E866 Measurements
To appear in PRL, arXiv 0710.2344
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Models for asymmetry
Meson Cloud Models
Chiral-Quark Soliton Model
Instantons

• Quark degrees of freedom in a pion mean-field
• nucleon chiral soliton
• expand in 1/Nc

Theses models also have implications on

• asymmetry between and

• flavor structure of the polarized sea

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Spin and flavor are closely connected

• Meson Cloud Model

• Pauli Blocking Model

A spin-up valence quark would inhibit the
probability of generating a spin-down antiquark

• Instanton Model

• Chiral-Quark Soliton Model

• Statistical Model

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JCP, Eur. Phys. J. A18 (2003) 395
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Quark Bremsstrahlung in Nuclear Medium

• Landau-Pomeranchuk-Migdal (LPM) effect of medium
  modification for electron bremsstralung has
  been observed
• LPM effect in QCD remains to be identified
• Quark energy loss ?E is predicted to be
  proportional to L2, where L is the length of the
  medium
• Enhanced quark energy loss in traversing
  quark-gluon plasma

PHENIX Collaboration (nucl-ex/0306021)
Quark energy loss in cold nuclei needs to be
better measured
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Quark Energy Loss in Cold Nuclei
Drell-Yan
Semi-inclusive DIS
(PRL 86 (2001) 4483)
(PRL 89 (2002) 162301)
5ltMlt6 GeV
7ltMlt8 GeV
(depends on shadowing correction)
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Quark Energy Loss with D-Y at Lower Energies
Correspond to larger x2, no nuclear shadowing
Fractional energy loss is larger at 50 GeV
Possible to test the LPM effect from the
A-dependence
Garvey and Peng, PRL 90 (2003) 092302
Fermilab E906 can study this at 120 GeV
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Drell-Yan decay angular distributions
T and F are the decay polar and azimuthal angles
of the µ in the dilepton rest-frame
Collins-Soper frame
A general expression for Drell-Yan decay angular
distributions
In general
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Decay Angular Distribution of Drell-Yan
Data from Fermilab E772
McGaughey, Moss, Peng Annu. Rev. Nucl. Part.
Sci. 49 (1999) 217 (hep/ph-9905409)
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Drell-Yan decay angular distributions
T and F are the decay polar and azimuthal angles
of the µ in the dilepton rest-frame
Collins-Soper frame
A general expression for Drell-Yan decay angular
distributions
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Decay angular distributions in pion-induced
Drell-Yan
NA10 p- W
Z. Phys. 37 (1988) 545
Dashed curves are from pQCD calculations
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Decay angular distributions in pion-induced
Drell-Yan
Is the Lam-Tung relation violated?
140 GeV/c
194 GeV/c
286 GeV/c
Data from NA10 (Z. Phys. 37 (1988) 545)
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QCD vacuum effects

• Brandenburg, Nachtmann Mirkes, Z. Phy.
  C60,697(1993)
• Nontrivial QCD vacuum may lead to correlation
  between the transverse spins of the quark (in
  nucleon) and the antiquark (in pion).
• The helicity flip in the instanton-induced
  contribution may lead to nontrivial vacuum.
• Boer,Brandenburg,NachtmannUtermann,
  EPC40,55(2005).

?00.17, mT1.5
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Boer-Mulders function h1-
?10.47, MC2.3 GeV
Boer, PRD 60 (1999) 014012
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Motivation for measuring decay angular
distributions in pp and pd Drell-Yan

• No proton-induced Drell-Yan azimuthal decay
  angular distribution data
• Provide constraints on models explaining the
  pion-induced Drell-Yan data. (h1- is expected to
  be small for sea quarks. The vacuum effects
  should be similar for pN and pN)
• Test of the Lam-Tung relation in proton-induced
  Drell-Yan
• Compare the decay angular distribution of pp
  versus pd

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Decay angular distributions for pd Drell-Yan at
800 GeV/c
pd at 800 GeV/c
No significant azimuthal asymmetry in pd
Drell-Yan!
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Azimuthal cos2F Distribution in pd Drell-Yan
L.Y. Zhu,J.C. Peng, P. Reimer et al., PRL 99
(2007) 082301
With Boer-Mulders function h1- ?(p-W?µµ-X)
valence h1-(p) valence h1-(p) ?(pd?µµ-X)
valence h1-(p) sea h1-(p)
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What does this mean?

• These results suggest that the Boer-Mulders
  functions h1- for sea quarks are significantly
  smaller than for valence quarks.
• These results also suggest that the non-trivial
  vacuum correlation between the sea-quark
  transverse spin (in one hadron) and the
  valence-quark transverse spin (in another hadron)
  is small.

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J/? and ? cross sections
E789 data p Au ? J/? (?) x (open aperture)
S1/2 38.8 GeV
Large discrepancy between the observed J/? (?)
cross sections and the calculations of
color-singlet model
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Polarization of J/?
E866 p Cu ? J/? x (beam dump) s1/2 38.8
GeV
(hep-ex/030801, T. Chang et al.)
Typical dimuon mass spectrum for various xF, pT,
cos? bins
ds/dO 1 ?cos2? (extraction of ? for various
xF, pT bins)
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Polarization of J/? in p Cu Collision
ds/dO 1 ? cos2?
(?1 transversely polarized, ? -1
longitudinally polarized ? 0, unpolarized)
E866 data

• ? is small, but nonzero
• ? becomes negative at large xF
• No strong pT dependence for ?

hep-ex/030801
Polarization of ? is being analyzed
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Polarization of ?(1S),?(2S3S)
p Cu ?? x (E866 beam-dump data)
Dimuon mass spectrum
Decay angular distributions
?(1S)
?(2S3S)
Brown et al. PRL 86, 2529 (2001)
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Polarization of ?(1S),?(2S3S)
p Cu ?? x (E866 beam-dump data)
? for D-Y, ?(1S), ?(2S3S)

• D-Y is transversely polarized
• ?(1S) is slightly polarized (like J/?)
• ?(2S3S) is transversely polarized!
• Analysis of Y polarization in pp and pd is
  underway (nuclear dependence?)
• Preliminary result shows ? is also transversely
  polarized!

?
pT (GeV)
?
xF
Brown et al. PRL 86, 2529 (2001)
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Nuclear effects of Quarkonium productions
p A at s1/2 38.8 GeV
E772 data
s(pA) Aas(pN)
Strong xF - dependence
Nuclear effects scale with xF, not x2 What about
negative xF?
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PT - broadening for D-Y, J/? and ?
Extract ltPT2gt from fits to data

• ?ltPT2gt for J/? is larger than for D-Y
• Similar behavior for J/? and ?

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Comparison between the J/? and ? nuclear effects
p A ? J/? or ? at s1/2 38.8 GeV
a(xF) is largely the same for J/? and ? (except
at xF 0 region)
Universal behavior for a(pT) (similar for J/?,
? weak s1/2 dependence)
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Nuclear effects of open-charm production
p A ? D x at s1/2 38.8 GeV
E789 open-aperture, silicon vertex dihadron
detection
hh- mass spectrum (after vertex cut)
No nuclear effect for D production (at xF 0)
D0 ? K- p
Need to extend the measurements to large xF region
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hep-ex/0506071
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Fermilab E906/Drell-Yan Collaboration
Abilene Christian University Donald Isenhower,
Mike Sadler, Rusty Towell Argonne National
Laboratory John Arrington, Don Geesaman, Kawtar
Hafidi, Roy Holt, Harold Jackson, David
Potterveld Paul E. Reimer, Patricia
Solvignon University of Colorado Ed
Kinney Fermi National Accelerator
Laboratory Chuck Brown University of
Illinois Naiomi C.R Makins, Jen-Chieh Peng Los
Alamos National Laboratory Gerry Garvey, Mike
Leitch, Pat McGaughey, Joel Moss Co-Spokesperso
ns
University of Maryland Elizabeth Beise Rutgers
University Ron Gilman, Charles Glashausser,
Xiaodong Jaing, E. Kuchina, Ron Ransome, Elaine
Schulte Texas A M University Carl Gagliardi,
Bob Tribble Thomas Jefferson National
Accelerator Facility Dave Gaskell Valparaiso
University Don Koetke, Jason Webb Academia
Sinica Wen-Chen Chang, Yen-Chu Chen,
Ping-Kun Teng
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Fermilab Accelerator ComplexFixed Target Program
Fixed Target Beamlines
Tevatron 800 GeV
Main Injector 120 GeV
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Measurement of High-Mass dimuon Production at
J-PARC (P-04)
Collaboration
Abilene Christian University, Argonne National
Laboratory, Duke University, High
Energy Accelerator Research Organization,
University of Illinois at Urbana-Champaign, Kyoto
University, Los Alamos National
Laboratory, Pusan National University, RIKEN,
Seoul National University, Tokyo Institute of
Technology, Tokyo University of
Science, Yamagata University
Collaboration members
J.K. Ahn, J. Chiba, Seonho Choi, D. Dutta, H.
Gao, Y. Goto, L.D. Isenhower, T. Iwata, S.
Kato,M.J. Leitch, M.X. Liu, P.L. McGaughey, J.C.
Peng, P. Reimer, M. Sadler, N. Saito, S.
Sawada,T.-A. Shibata, K.H. Tanaka, R. Towell,
H.Y. Yoshida
(Spokesperson S. Sawada and J. C. Peng)
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Polarized proton beam at J-PARC ?

• Polarized proton beam at J-PARC with
• Polarized H source
• RF dipole at 3 GeV RCS
• Two 30 partial snakes at 50 GeV Main Ring

30 GeV
pC CNI Polarimeter
50 GeV
Extracted Beam Polarimeter
Pol. H- Source
Rf Dipole
180/400 MeV Polarimeter
25-30 Helical Partial Siberian Snakes
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Physics with High-Mass Dimuons at J-PARC
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Summary

• Dimuon production experiments at Fermilab have
  provided unique information on nucleon and
  nuclear substructures
• Future dimuon production experiments at lower
  beam energies (120 GeV Main-Injector and 50 GeV
  J-PARC) could provide interesting new information
  at large x and spin-dependent parton
  distributions in the nucleons