Large-X PDFs in the Drell-Yan Process
description
Transcript of Large-X PDFs in the Drell-Yan Process
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Large-X PDFs in the Drell-Yan Process
Jen-Chieh Peng
“3rd International Workshop on Nucleon Structure at Large Bjorken X”
Jefferson Lab, Newport News, Oct. 13-15, 2010
University of Illinois at Urbana-Champaign
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• Complementarity between the DIS and the Drell-Yan process for probing parton distributions in nucleon and nuclei
• Sea-quark distributions in the medium-X region with Drell-Yan and W-boson production
• Parton distributions in nuclei with proton and pion induced Drell-Yan process
• Charge-symmetry breaking of parton distributions with the W-boson production
• Transverse-momentum-dependent parton distributions with the Drell-Yan process
Outline
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Complimentality between DIS and Drell-Yan
Both DIS and Drell-Yan process are tools to probe the quark and antiquark structure in hadrons (factorization, universality)
DIS Drell-Yan
McGaughey, Moss, JCP,
Ann.Rev.Nucl. Part. Sci. 49 (1999) 217
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Lepton-pair production provides unique information on parton distributions
194 GeV/c
W X
800 GeV/c
p W X
1.8 TeV
p p l l X
Probe antiquark distribution in nucleon Probe antiquark
distribution in pion Probe antiquark
distributions in antiproton
Unique features of D-Y: antiquarks, unstable hadrons…
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Fermilab Dimuon Spectrometer(E605 / 772 / 789 / 866 / 906)
"Nuclear Dependence of Drell-Yan and Quark
1) Fermilab E772
2) Fermilab E789
(proposed in 1986 and completed in 1988)
(proposed in 1989 and completed in 199
onium Production"
"Search for Two-Bo
1)
dy Decays of Heavy Quark Mesons"
"Determination of / Ratio of the Proton via Drell-Ya
(proposed in 1993 and completed in 13) Fermilab E866
4) Fermilab E906
996)
(proposed in 1999, will run in 2010-20
n
)
"
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d u
"Drell-Yan with the FNAL Main Inje ctor"
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/ flavor asymmetry from Drell-Yand u
2 2
1/ 2 (1 ( ) / ( )Dr )
2ell-Yan: pd pp d x u x
2 2
21 2 1 2
1 2 1 2. .
4( ) ( ) ( ) ( )
9 a a a a aaD Y
de q x q x q x q x
dx dx sx x
1 2 :at x x
800 GeV proton beam
on hydrogen and deuterium
mass spectrum
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What's next for / ?d u2
21 2 1 2
1 2 1 2
4[ ( ) ( ) ( ) ( )
1]
3DY
i ii
de q x q
sx q x q x
dx dx x x
J-PARC 50 GeV
Intriguing / behavior at large
can be studied at lower beam energies
d u x DY cross section is 6 times larger
at 120 GeV than at 800 GeV
120 GeV proton bea
Fermilab E-906
(P. Reimer, D. Geesaman et al.)
J-PARC P-04
(J. Peng, S. Sawada et
m
50 GeV proton
al
be
.)
am
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/ from W production d u production in collisionW p p
p p W x p p W x
( )u d W ( )d u W
No nuclear effects !
No assumption of charge-symmetry !
Large Q2 scale !
21
21
( )( )
(
( )(
( ) ))
( )
FF
F
dpp W X
dx u xR x
d d xpp
d x
uW xXdx
9
u d
u d
R. Z. Yang, JCP, Perdekamp, PL B680 (2009) 231
/ from W production at RHICd u/ ( )
( ) at 500 GeV/ ( )
FF
F
d dx pp W xR x s
d dx pp W x
u d
u d
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/ from W production at PHENIXd u/ ( )
( ) at 500 GeV/ ( )
d dy pp W x l xR y s
d dy pp W x l x
detection
u d
300 pb-1 integrated luminosity
detectione
u d
u d detection
R. Z. Yang, JCP, Perdekamp, PL B680 (2009) 231
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Gluon distributions in proton versus neutron?
New data on ( / ) / 2 ( / ) expected for E906p d J p p J
/ 2 [1 ( ) / ( )] / 2:
/ , : / 2 [1 ( ) / ( )] / 2
pd pp
pd ppn p
d x uDrell Y x
g
an
J x g x
Lingyan Zhu et al., PRL, 100 (2008) 062301 (arXiv: 0710.2344)
Gluon distributions in proton and neutron are very similar
E866data: ( ) / 2 ( )p d X p p X
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Charge Symmetry Violation in PDF?
2 2
Charge symmetry : rotation around isospin axis by 180
Charge symmetry in PDF is generally assumed, bu
( ; .)
A compari
t not tested
son of with shows upper limit o f
n
y
p n pp n u d u d u d u d etc
F F
I
The NuTeV anomaly in the Weinberg angle could be partly
explained b
(Lon
y ch
CS breaking
of 5 1
arge symmetry vio
dergan and
latio
Thomas, hep-ph/0407247)
(Londergan and Thomas,
n
0%
P
L B558
(2003) 132)
See recent review of Londergan, JCP, and Thomas (arXiv:0907.2352)
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Charge Symmetry violation from MRST Global fits
(Eur. Phys. J. C35, 325 (2004))
4 0.5(
(
) (1 ) ( 0.0
) ( ) ( )
Best fit: 0.2
0.8 0.65 (90%
( ) ( ) ( )
( )
C.L.)
90
(
9
)
)
( )
V V
p nV V V
p nV V V
u x d x f x
d x d x u x
u x u
f x x x
x
x
x d
Best fit: 0.08
(8% of C
0.08 0.18 (90
( ) ( )[
SV
1 ]
( ) ( )[
fo
% C
1 ]
r
.L
.
!
)
sea )
n p
n p
u x d x
d x u x
CSV for sea quarks
CSV for valence quarks
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Comparison between MRST and quark-model calculation
Charge symmetry violation for valence quarks
MRST Quark-model
(Rodionov, Thomas, Londergan)Eur. Phys. J. C35, 325 (2004)
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CSV from W production2 / ( )
( ) at 500 GeV/ ( )
FF
F
d dx pp W xR x s
d dx pd W x
2 2
2 2
/ ( )( )
2 / ( )
( ) ( )11
2 (
for 0, ( ) is sensitive to
valence-quar
) ( )
k CSV
FF
F F
F
d dx pd W xR x
d dx pp W x
d x d x
u x u x
x R x
R. Yang and JCP, preprint
Charge symmetry violating
Charge-symmetric
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CSV from W production2 / ( )
( ) at 500 GeV/ ( )
FF
F
d dx pp W xR x s
d dx pd W x
2 2
2 2
/ ( )( )
2 / ( )
( ) ( )11
2 ( ) ( )
for 0, ( ) is sensitive to
sea-quark CSVF F
FF
F
d dx pd W xR x
d dx pp W x
d x d x
u x
x
u x
R x
R. Yang and JCP, preprint
Charge-symmetric
Charge symmetry violating
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Modification of Parton Distributions in NucleiEMC effect observed in DIS
How are the antiquark distributions modified in nuclei?F2 contains contributions from quarks and antiquarks
(Ann. Rev. Nucl. Part. Phys., Geesaman, Sato and Thomas)
Extensive studies by Kumano et al. and Strikman et al.
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Drell-Yan on nuclear targets
The x-dependence of can be directly measured( ) / ( )A Nu x u x
( )
( )
pAA
pdN
u x
u x
PRL 64 (1990) 2479 PRL 83 (1999) 2304
No evidence for enhancement of antiquark in niclei !?E906 will extend the measurement to larger x
1919
Cloet, Bentz, and Thomas, arXiv:0901.3559
Isovector mean-field generated in Z≠N nuclei can modify nucleon’s u and d PDFs in nuclei
How can one check this prediction?
Flavor dependence of the EMC effects ?
• SIDIS (JLab proposal) and PVDIS (P.Souder)
• Pion-induced Drell-Yan ?
Q2= 10 GeV2
Gold nucleus
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(Dutta, JCP, Cloet, Gaskell, arXiv:1007.3916)
W+, W- production in P+A collision is also sensitive to flavor-dependent EMC
2121
Related to quark’s transverse momentum and/or transverse spin
1) Transversity
2) Sivers function
3) Boer-Mulders function
Correlation between and q Ns S
Correlation between and q qs k
Correlation between and N qS k
Three transverse quantities:
1) Nucleon transverse spin
2) Quark transverse spin
3) Quark transverse
mo
Three diff
me
er
ntum
ent correlations
N
q
q
S
s
k
Probing novel PDFs with the Drell-Yan
2222
4
26 4
Q
sxd
),()(])1(1{[ 211
,
22 h
qqq PzDxfey
22 (1) 2
1 12,
22 (1) 2
1 12,
2 21 1
,
cos(2 )
sin(2 )
(1 ) ( ) ( , )4
| |
s
(1 ) ( ) ( , )4
| | (1 ) ( ) (in( )) ,
q qhq h
q qN h
q qhL q L h
q qN h
q
lh
lh
l lh
qhST q h
q qh
Py e h x H z P
z M M
PS y e h x H z P
z M M
PS y e h x H z P
zM
2 2 (1) 21 1
,
32 (2) 2
1 13 2,
2 21 1
,
1| | (1 ) ( ) ( , )
2
| | (1 ) ( ) ( , )6
1| | (1 ) ( ) ( , )
2
1| | (1 )
sin( )
sin(3 )
co ( )2
s
q qhT q T h
q qN
q qhT q T h
q qN h
q qe L q h
q q
he T
N
l lh S
l lh S
l lh S
PS y y e f x D z P
zM
PS y e h x H z P
z M M
S y y e g x D z P
PS y y e
zM
2 (1) 2
1 1,
( ) ( , )}q qq T h
q q
g x D z P
Unpolarized
Polarized target
Polarzied beam and
target
SL and ST: Target Polarizations; λe: Beam Polarization
Sivers
Transversity
Boer-Mulders
Transversity and Transverse Momentum Dependent PDFs are probed in Semi-Inclusive DIS
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Transversity and Transverse Momentum Dependent PDFs are also probed in Drell-Yan
1 1
1
a) Boer-Mulders functions:
b) Sivers functions
- Unpolarized Drell-Yan:
- Single transverse spin asymmetry in polarized Drell-Yan:
:
c) Transv
( ) ( ) cos(2 )
( ) ( )
e
DY q q
DYN T q q q
d h x h x
A f x f x
1 1
rsity distributions:
Drell-Yan does not require knowledge of the fragmentation functions
T-odd TMDs are pre
- Double transverse spin asymmetry in polarized Drell-Yan:
(
d
) ( )DYTT q qA h x h x
icted to change sign from DIS to DY
(Boer-Mulders and S
Remains to be te
ivers functions)
sted experimenta lly!
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Transverse Momentum Dependent PDFs with polarized Drell-Yan
Ralston and Soper
Pire and Ralston
Tangerman and Mulders
Boe
(NP B152 (1979) 109)
(PR D28 (1983) 260)
(PR D51 (1995) 3357)
(r
Arnold, Metz, and
PR D60 (1999) 0
Schlegel
14012)
(PR D79 ( 2009)
034005)
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Boer-Mulders function h1┴ from Drell-Yan
1
1
is a time-reversal odd, chiral-odd TMD parton distribution
can lead to an azimuthal cos(2 ) dependence in Drell-Yan
h
h
Boer, PRD 60 (1999) 014012
● Observation of large cos(2Φ) dependence in Drell-Yan with pion beam
●
● How about Drell-Yan with proton beam?
194 GeV/c π + W
2 21 31 cos sin 2 cos sin cos 2
4 2
d
d
1 1 ( ) ( )q qh x h x
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Boer-Mulders function h1┴:
ν(π-Wµ+µ-X)~ [valence h1┴(π)] * [valence
h1┴(p)]
ν(pdµ+µ-X)~ [valence h1┴(p)] * [sea h1
┴(p)]
Azimuthal cos2Φ Distribution in p+p and p+d Drell-Yan
E866 Collab., Lingyan Zhu et al., PRL 99 (2007) 082301; PRL 102 (2009)
182001
Sea-quark BM functions are much smaller than valence quarks
Smallνis observed for p+d D-Y
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Results on cos2Φ Distribution in p+p Drell-Yan
QCD (Boer, Vogelsang; Berger, Qiu, Rodriguez-Pedraza)
p+p
p+d
L. Zhu, J.C. Peng, et al., PRL 102 (2009) 182001
More data are anticipated from Fermilab E906
Combined analysis of SIDIS and D-Y by Melis et al.
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Transversity and Transverse Momentum Dependent PDFs are also probed in Drell-Yan
1 1
1
a) Boer-Mulders functions:
b) Sivers functions
- Unpolarized Drell-Yan:
- Single transverse spin asymmetry in polarized Drell-Yan:
:
c) Transv
( ) ( ) cos(2 )
( ) ( )
e
DY q q
DYN T q q q
d h x h x
A f x f x
1 1
rsity distributions:
Drell-Yan does not require knowledge of the fragmentation functions
T-odd TMDs are pre
- Double transverse spin asymmetry in polarized Drell-Yan:
(
d
) ( )DYTT q qA h x h x
1 1
icted to change sign from DIS to DY
(Boer-Mulders and Sivers functi
Remain
( )ons)
s to be tested experimentally!
( )T q DY T q DISf x f x
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30
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32PAC recommends preparation of full proposal
From Y. Goto
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Future prospect for Drell-Yan experiments• Fermilab p+p, p+d, p+A
– Unpolarized beam and target
• RHIC– Doubly and singly polarized p+p collision
• COMPASS– π-p and π-d with polarized targets
• FAIR– Polarized antiproton-proton collision
• J-PARC– Possibly polarized proton beam and target
• JINR– NICA with polarized target
• IHEP– SPASCHARM with polarized target p-p and π-p
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• Does Sivers function change sign between DIS and Drell-Yan?
• Does Boer-Mulders function change sign between DIS and Drell-Yan?
• Are all Boer-Mulders functions alike (proton versus pion Boer-Mulders functions)
• Flavor dependence of TMD functions• Independent measurement of transversity
with Drell-Yan
Outstanding questions to be addressed by future Drell-Yan experiments
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Summary• The Drell-Yan process is a powerful
experimental tool complementary to the DIS for exploring quark structures in nucleons and nuclei.
• Unique information on flavor structures of sea-quark has been obtained with Drell-Yan experiments. First results on TMD have also been extracted.
• On-going and future Drell-Yan experiments at various hadron facilities can address many important unresolved issues in the spin and flavor structures of nucleons and nuclei.