The EMC Effect
Gerald A. Miller, Univ. of Washington
INTERNATIONAL JOURNAL
OF
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VOLUME 53
NUMBER 4
MAY 2013
Deep in the nucleus:
a puzzle revisited
HEAVY IONS
ASTROWATCH
The key to finding
out if a collision
is head on
p31
Planck reveals an
almost perfect
universe
p12
IT’S A
HIGGS BOSON
The new particle
is identified p21
Higinbotham, Miller, Hen
CERN Courier 53N4(’13)24
WWW.
What is the EMC effect?
What does it mean?
1
What are the consequences?
EMC Effect -Outline
• Basic issues -what is the EMC effect, why
important?
• Simple ideas
• What is Drell-Yan pair production, why
relevant?
• Why nucleon structure must be modified for
nucleons in nuclei
• Simple models and examples of tests
• Two-nucleon effects are important
• Necessities for future progress
2
Fundamental questions of
Nuclear Physics
• Is the nucleus made only of nucleons and
mesons?
• How does the nucleus emerge from QCD, a theory
of quarks and gluons?
• Why is the nucleon-meson picture of nuclei so
accurate?
• Is the gluonic content of the nucleus the same as
for nucleons in free space?
• Is there a non-perturbative sea in the nucleon?
No one asked such questions before the EMC effect
3
was discovered
Primer- Deep Inelastic
Scattering- large ⌫, Q2
e
Electron loses energy and is scattered by some angle: two variables: ⌫, Q2
Large ⌫, Q2 scattering on elementary quark. Four-momentum conservation !
Q
dynamics depend on x =
x P+
Q2
2M ⌫
x ratio of quark p+ to proton momentum P + (P ± ⌘ P 0 ± P 3 )
Nucleon from PDG
P
1
0.9
NNPDF2.3 (NNLO)
0.
xf(x,µ 2=10 GeV2)
0.8
The EMC effect involves deep
inelastic scattering from nuclei
EMC= European Muon Collaboration
0.7
0.
g/10
0.
0.6
0.
uv
0.5
0.
0.4
0.3
0.
dv
0.2
u
0.1
0
-3
10
0.
s
0.
d
0.
c
10-2
4x
10-1
1
0
1
Figure 19.4: The bands are x times the u
(where f = uv , dv , u, d, s ≃ s̄, c = c̄, b = b̄, g)
The EMC EFFECT
Fig. 2: The image shows the ratio of deep-­inelastic cross sections of Ca to D from NMC
(solid circles) and SLAC (open circles). The downward slope from 0.3 < x < 0.7 and
subsequent rise from xB > 0.7 is a universal characteristic of EMC data and has became
known as the EMC effect. The reduction of the ratio at lower values of xB, where valence
quarks should no longer be playing a significant role, is known as the shadowing region.
Fig. 1: Image of the EMC data as it appeared in the November 1982 issue of the CERN
Courier. This image nearly derailed the highly cited refereed publication (Aubert et al.,
1983), as the editor argued that the data had already been published.
Valence quark
momentum is reduced
Nucleon structure is modified: valence quark momentum depleted.
How do quarks work in a nucleus?
BUT EFFECTS ARE SMALL ~15%
5
The EMC EFFECT
Fig. 2: The image shows the ratio of deep-­inelastic cross sections of Ca to D from NMC
(solid circles) and SLAC (open circles). The downward slope from 0.3 < x < 0.7 and
subsequent rise from xB > 0.7 is a universal characteristic of EMC data and has became
known as the EMC effect. The reduction of the ratio at lower values of xB, where valence
quarks should no longer be playing a significant role, is known as the shadowing region.
Fig. 1: Image of the EMC data as it appeared in the November 1982 issue of the CERN
Courier. This image nearly derailed the highly cited refereed publication (Aubert et al.,
1983), as the editor argued that the data had already been published.
Valence quark
momentum is reduced
Nucleon structure is modified: valence quark momentum depleted.
How do quarks work in a nucleus?
BUT EFFECTS ARE SMALL ~15%
5
Simple models of reduction of
valence quark momentum
• quarks in nuclei move through a larger
confinement volume (uncertainty principle)
• bound nucleons are larger than free ones
• nucleons in nuclei move in 6, 9 or 3A
quark bags
• nuclear binding, Fermi motion, pionic
effects
6
Simple models of reduction of
valence quark momentum
• quarks in nuclei move through a larger
confinement volume (uncertainty principle)
• bound nucleons are larger than free ones
• nucleons in nuclei move in 6, 9 or 3A
quark bags
• nuclear binding, Fermi motion, pionic
effects
EMC – “Everyone’s Model is Cool (1985)’’
6
One thing I learned since ‘85
One thing I learned since ‘85
• One model is not cool• unmodified nucleon -free
structure function
Deep Inelastic scattering from nucleinucleons only free structure function
• Hugenholz van Hove
theorem nuclear
stability implies (in rest
frame) P+=P- =MA
Smith Miller ‘02
Binding causes no
EMC effect
Pb
• P+ =A(MN - 8 MeV)
• average nucleon k+
k+=MN-8 MeV, Not much
spread
F2A/A~F2N no EMC effect
Smith & Miller
Phys.Rev. C65 (2002) 015211, Phys.Rev. C66 (2002) 049903
SLAC-E139
Phys.Rev. C65 (2002) 055206
Nucleons and pions
PA+ = PN+ + Pπ+ =MA
Pπ+ /MA =.04, explain EMC
try Drell-Yan,
Bickerstaff, Birse, Miller 84
proton(x1) nucleus(x2)
x1
x2
Phys.Rev.D33:3228,1986
Phys.Rev.Lett.53:2532,1984.
Nucleons and pions
PA+ = PN+ + Pπ+ =MA
Pπ+ /MA =.04, explain EMC
Drell-Yan, E772
PRL 69,1726 (92)
π
fails
No one’s model is cool
Nucleons and pions
PA+ = PN+ + Pπ+ =MA
Pπ+ /MA =.04, explain EMC
Drell-Yan, E772
PRL 69,1726 (92)
π
fails
No one’s model is cool
Bertsch, Frankfurt, Strikman “crisis in nuclear
theory” conventional physics does not work
Nucleons, pions, shadowing,
universal nucleon modification
• A model containing all of these aspects
does account for DIS and DY-Kulagin Petti
• No underlying dynamics-can’t predict other
phenomena
11
Single nucleon modification by nuclei
p
⇡
n
• Does it make sense? It is inevitable. Pion cloud
modified by nucleus, W cloud too
• Neutron in nucleus is modified, lifetime
changed from 15 minutes to forever
• Binding changes energy denominator,
suppresses peν component
• Change energy denominator change wave fun
• Also Strong fields polarize nucleons- analog of
Stark effect
Inevitability of medium modifications-(e,e’p)
⇤
MA
(⌫, ~q )
(Ef , p~ + ~q )
p
Form factor modified
because p2 6= M 2
Problem: conventional nuclear
wave function involves on-mass
shell nucleons
(Es , p~)
Nucleus A-1
13
Single nucleon in a nucleus
1968 SLAC-MIT nucleon not a point: !
quarks don’t interact
1947 Shell Model
R
R
1982 EMC
or
14
?
?
Nucl.Phys. B250 (1985) 143-
1985 PLC Suppression Frankfurt Strikman
1995 BLC Frank Jennings Miller
Phys.Rev. C54 (1996) 920-
+✏
?
?
?
?
Nucleon has large blob-like configuration BLC and small point like configuration PLC!
BLC is affected by nucleus PLC, not affected . Result PLC suppressed/BLC enhanced
15
Nucleon in medium- 5 models
1. QMC- quarks in nucleons
(MIT bag) exchange
mesons with nuclear
Nuclear matter
medium, quark mass
2. Use NJL instead of bag Cloét
External fields
3. CQSM- quarks in
nucleons (soliton)
exchange infinite pairs of
pions, vector mesons
with nuclear medium, mq
4. Suppression of point-likeconfigurations,
5. Enhancement of blob-like
configurations
polarization
Spin experiments-NJL in medium
•
g , g
1p in nuclei
1n
Bentz, Cloet, Thomas
!
• other way to
enhance EMC?
ratio of g1
medium to
free
Kuhn talk
Spin
Chiral Quark Soliton Model –
Diakonov, Petrov, Polykov, quarks couple to vacuum instantons
Negele et al hep-lat/9810053
• Vacuum dominated by
topological charge density
instantons
• quarks with
spontaneously generated
masses interact with
pions
!
!
• Nucleon is soliton in pion
field
• M=420 MeV
• good nucleon properties,
DIS and magnetic
moments
Chiral Quark Soliton Model of NucleusSmith, Miller
2 π exchange – attraction
ω (vector meson) exchange repulsion
Phys.Rev. C72 (2005) 022203
Phys.Rev. C70 (2004) 065205
Phys.Rev.Lett. 91 (2003) 212301, Phys.Rev.Lett. 98 (2007) 099902
Double self consistency
profile function and kf
Results Smith & Miller ’03,04,05
g1 ratio
EMC ratio
full
Nuclear Drell Yan
valence only
sea is not much modified
About same as DIS, not larger
contrasts QMC Kuhn talk
Models Predict
Form-Factor
Medium
Modifications
Another
medium effect:
form
factors
•
Changes in the internal
structure of bound nucleons
result also in bound nucleon
form factors.
•
Observable effects predicted:
CQS
QMC
ρ = 0.5 ρ0
ρ = 1.0 ρ0
ρ = 1.5 ρ0
Chiral Quark Soliton (CQS),
Quark Meson Coupling (QMC),
Skyrme, Nambu-Jona-Lasinio
(NJL), GPD Models.
•
Model predictions:
‣ are density and Q2 dependent,
‣ show similar behavior,
‣ consistent with experimental
CQS: J.R. Smith and G.A. Miller, Phys. Rev. C 70, 065205 (2004)
QMC: D.H. Lu et al., Phys. Lett. B 417, 217 (1998)
data (within large
uncertainties).
NJL: I.C. Cloet, W. Bentz, and A.W. Thomas (to be published)
7
S Strauch slide
21
S. Strauch ratio of
GE /GM
• 2H and 1H
polarization-transfer
data are similar
≈ 10%
Effect
• 4He data are
significantly different
than 2H, 1H data
low pm data
2H:
B. Hu et al., PRC 73, 064004 (2006). 4He: S. Dieterich et al., PLB 500, 47 (2001); S. S., et al., PRL 91, 052301 (2003);
M. Paolone, et al., PRL 105, 0722001 (2010); S. Malace et al., PRL 106, 052501 (2011)
1
22
Enhancement of Blob-like
Configurations- Frank,Jennings, Miller
PRC 54, 920
free
place in medium:
normal size components attracted energy goes
down
PLC does not interact- color screening-FS
BLC is enhanced
quarks lose momentum in medium
1995 Frank, Jennings, Miller
Enhancement of Blob-Like
Configurations
FS-PLC has NO
int. with medium
energy denominator increased
EMC ratio Frank,Jennings Miller ‘95
evaluated as
QCD Stark, not
modified energy
denominator
More data
[3-69] S. Bueltmann et al., Jefferson Lab Experiment E12-06-113
[4-1] J. Seely et al., Phys. Rev. Lett. 103, (2009) 202301
[3-70] G.G. Petratos et al., Jefferson Lab Experiment E12-10-103
[4-2]
N. Fomin,
et al.,
Rev. Lett. 108, 092502 (2012)
Another outstanding question is whether the [3-71]
nuclearP.A.
medium
alters
of Phys.
bound
Souder
et al.,the
Thestructure
SoLID Experiment,
Jefferson Lab Experiment E12
(a)
(b)
(c)
nucleons and, if so, how? The neutron lifetime in nuclei is certainly
different.
The first
evidence
[4-3]
J.J. Aubert
et al.,
Phys. Lett. 123B (1983) 275
[3-72]
Accardi
et al.,deep-inelastic
Phys. Rev. D 84,
014008 (2011)
for nucleon structure modification was the EMC
effectA.
[4-3],
in which
scattering
[4-4]
L.B.
Weinstein
et
al.,
Phys. Rev. Lett. 106, 052301 (2011
from nuclear quarks is significantly different [3-73]
than from a “free” nucleon G.D.quarks Cates,inside C.W. de
Jager, S.
Riodan(see
and B. Wojtsekhowski, Phys. Rev L
Figure 4.1a). The per-nucleon DIS cross section ratio
of nucleus
to Baillie
deuterium
[4-5]A N.
et al.,decreases
Phys. Rev. Lett. 108, 142001 (2012)
(2011)
252003
approximately linearly for 0.3 < xB < 0.7. The slope of this ratio in this region increases with A
[4-6] al.,
A.V.
Klimenko
Phys.
Rev. C I.C.
73, 035212
Eur.
Phys.
J. et
STal.,
140,
53 (2007);
Clöet et(2006)
al., Fewbut does not scale simply with average nuclear[3-74]
densityC.D.
(see Roberts
Figure et
4.2). Despite
a world-wide
Systems
46,
1
(2009)
Bueltmann
al.,GeV
“The Structure of the Free Neutron a
effort in experiment and theory, the origins of the EMC effect [4-7]
remainS.unclear.
Theet 12
LabMiller,
Experiment
E12-06-113.
experimental program will measure the EMC effect
in aI.C.
wide
range
nuclei
to help
unravel
the (2012)
[3-75]
Clöet
andofG.A.
PRC
86,
015208
mystery [4-24, 4-25].
Hen et al.,
Nucleon
Structure
Functions,
[3-76] M. Guidal,[4-8]
M. V.O.
Polyakov,
A.“In
V. Medium
Radyushkin,
and M.
Vanderhaeghen
Ph
Jefferson
Lab
Expt
E12-11-107.
72,4.2)
054013
Recent phenomenological comparisons [4-4] (see Figure
show(2005)
that the strength of the EMC
effect in different nuclei is linearly related to the
short P.Maris
range correlations
factor,
A62,
/Sargsian,
d055204
).
[4-9]
W.scale
Melnitchouk,
and
M.I. Strikman, Z. Phy
[3-77]
and
P.Tandy,
Phys.
Rev.𝑎2C(M.
(2000)
This linear relation indicates, but does not prove, that the EMC effect is caused by local
[4-10] L.
ElA.V.
Fassi,Radyushkin,
et al., Phys. Lett. B712, 326 (2012)
and
modifications of nucleon structure occurring[3-78]
when V.A.
two Nesterenko
would-be nucleons
make a closePhys. Lett. B115, 410(1982)
[4-11]
Frankfurt,
G.A.
Miller
encounter and briefly comprise a system of density
enough
toPhys.Rev.D
beL.comparable
to that
of and M.Strikman, Phys. Rev. C
[3-79] high
C-W.
Hwang,
64(2001)n034001
neutron stars. This relationship will be tested and refined at 12[4-12]
GeV by
seriesetofal.,EMC
andof Color Transparency in Exclusi
K. aHafidi
“Study
[4-1] J. Seely et al., Phys.
Rev. Lett.
103,
(2009)
202301
SRC experiments covering a wide range of nuclei [4-19, 4-20, 4-24,Electroproduction
4-25]. The deuteron
off Nuclei”, Jefferson Lab Experiment
N. (per-nucleon)
Fomin, et al.,
Rev. Lett.
108,
092502 (2012)
experiment
mentioned
[4-18]cross
will increase
our
understanding
of Phys.
the
system
Figure
4.1: The
electronabove
scattering
section[4-2]
ratios
of two-nucleon
various
nuclei
to
that
we
use
as
a
baseline
for
both
the
EMC
and
SRC
measurements.
12 [4-13] E.M. Aitala et al. [E791 Collaboration], Phys. Rev. Lett.
al.,<Phys.
123B
(1983)
deuterium. (a) Ratios for 0.2 < xB < 0.9 [4-1]; (b) [4-3]
RatiosJ.J.
forAubert
C foret0.3
xB < Lett.
2 [4-1,
4-2];
(c) 275
[4-14] L. Frankfurt, G.A. Miller and M. Strikman, Phys. Lett. B
Ratios for 0.8 < xB < 1.8 [4-2].
[4-4] L.B. Weinstein et al., Phys. Rev. Lett. 106, 052301 (2011)
[4-15] B. Clasie, et al., Phys. Rev. Lett. 99, 242502 (2007)
Nucleons acquire high-momentum via short-range
interactions,
influence
of
[4-5]
N. Baillie et rather
al., Phys.than
Rev.by
Lett.the
108,
142001 (2012)
4a.2
Nucleon
properties
in nuclei
relative NN
wave
function
at short distances.
the nuclear mean-field. Thus, for momenta above
Fermi
sea, the
of the
momentum
[4-6]theA.V.
Klimenko
et al.,shape
Phys. Rev.
C 73,
035212 (2006)
distribution should be universal. This is shown by[4-7]
the plateaus
(regions of constant cross section 60
S. Bueltmann et al., “The Structure of the Free Neutron at Large x-Bjorke
ratio) observed at xB > 1.5 (see Figure 4.1c). The values
of the ratio
at these plateaus, a2(A/d),
Lab Experiment
E12-06-113.
are closely related to the probability of finding a[4-8]
nucleon
belonging to a short-range correlated
O. Hen et al., “In Medium Nucleon Structure Functions, SRC, and the EM
pair in nucleus A relative to deuterium.
Jefferson Lab Expt E12-11-107.
W.understand
Melnitchouk, the
M. Sargsian,
M.I. Strikman,
Experiments at 12 GeV will study the deuteron to[4-9]
better
simplestand
nuclear
systemZ. Phys. A359, 99 (199
El Fassi, et above
al., Phys.
B712,greater
326 (2012)
[4-18]. Other experiments will extend the SRC [4-10]
studiesL.described
toLett.
a much
range
3
3
of xB, momentum transfers, and nuclei (including
H and
He) toG.A.
study
two
three nucleon
[4-11]
L. Frankfurt,
Miller
andand
M.Strikman,
Phys. Rev. C 78, 015208 (2008
correlations
(including
their
isospin
character),
with
higher
nucleon
momenta
[4-19,
4-20].
The
[4-12]
K.plotted
Hafidi
et al.,the“Study
Color
Transparency
in
Figure
4.2: (left) The
strength
of the EMC
effect (the EMC
slope)
versus
averageofnuclear
density
[426Exclusive Vector Meson
2
(right)from
The strength
effect plotted versus
the probe
SRCElectroproduction
scale
factors
[4-4]. off
TheNuclei”,
drawing
in
the upper
highest Q1]. data
the xofB the
> 1EMC
measurements
will
the
distribution
of superfast
quarks
in
Jefferson
Lab Experiment
E12-06-106.
left shows deep inelastic electron scattering from a quark in a nucleon. The drawing in the lower right shows
nuclei, greatly extending our understanding of nucleons
at short
[4-13] E.M.
Aitaladistances.
et al. [E791 Collaboration], Phys. Rev. Lett. 86, 4773 (2001)
More data
[3-69] S. Bueltmann et al., Jefferson Lab Experiment E12-06-113
[4-1] J. Seely et al., Phys. Rev. Lett. 103, (2009) 202301
[3-70] G.G. Petratos et al., Jefferson Lab Experiment E12-10-103
[4-2]
N. Fomin,
et al.,
Rev. Lett. 108, 092502 (2012)
Another outstanding question is whether the [3-71]
nuclearP.A.
medium
alters
of Phys.
bound
Souder
et al.,the
Thestructure
SoLID Experiment,
Jefferson Lab Experiment E12
(a)
(b)
(c)
nucleons and, if so, how? The neutron lifetime in nuclei is certainly
different.
The first
evidence
[4-3]
J.J. Aubert
et al.,
Phys. Lett. 123B (1983) 275
[3-72]
Accardi
et al.,deep-inelastic
Phys. Rev. D 84,
014008 (2011)
for nucleon structure modification was the EMC
effectA.
[4-3],
in which
scattering
[4-4]
L.B.
Weinstein
et
al.,
Phys. Rev. Lett. 106, 052301 (2011
from nuclear quarks is significantly different [3-73]
than from a “free” nucleon G.D.quarks Cates,inside C.W. de
Jager, S.
Riodan(see
and B. Wojtsekhowski, Phys. Rev L
Figure 4.1a). The per-nucleon DIS cross section ratio
of nucleus
to Baillie
deuterium
[4-5]A N.
et al.,decreases
Phys. Rev. Lett. 108, 142001 (2012)
(2011)
252003
approximately linearly for 0.3 < xB < 0.7. The slope of this ratio in this region increases with A
[4-6] al.,
A.V.
Klimenko
Phys.
Rev. C I.C.
73, 035212
Eur.
Phys.
J. et
STal.,
140,
53 (2007);
Clöet et(2006)
al., Fewbut does not scale simply with average nuclear[3-74]
densityC.D.
(see Roberts
Figure et
4.2). Despite
a world-wide
Systems
46,
1
(2009)
Bueltmann
al.,GeV
“The Structure of the Free Neutron a
effort in experiment and theory, the origins of the EMC effect [4-7]
remainS.unclear.
Theet 12
LabMiller,
Experiment
E12-06-113.
experimental program will measure the EMC effect
in aI.C.
wide
range
nuclei
to help
unravel
the (2012)
[3-75]
Clöet
andofG.A.
PRC
86,
015208
mystery [4-24, 4-25].
Hen et al.,
Nucleon
Structure
Functions,
[3-76] M. Guidal,[4-8]
M. V.O.
Polyakov,
A.“In
V. Medium
Radyushkin,
and M.
Vanderhaeghen
Ph
Jefferson
Lab
Expt
E12-11-107.
72,4.2)
054013
Recent phenomenological comparisons [4-4] (see Figure
show(2005)
that the strength of the EMC
effect in different nuclei is linearly related to the
short P.Maris
range correlations
factor,
A62,
/Sargsian,
d055204
).
[4-9]
W.scale
Melnitchouk,
and
M.I. Strikman, Z. Phy
[3-77]
and
P.Tandy,
Phys.
Rev.𝑎2C(M.
(2000)
This linear relation indicates, but does not prove, that the EMC effect is caused by local
[4-10] L.
ElA.V.
Fassi,Radyushkin,
et al., Phys. Lett. B712, 326 (2012)
and
modifications of nucleon structure occurring[3-78]
when V.A.
two Nesterenko
would-be nucleons
make a closePhys. Lett. B115, 410(1982)
[4-11]
Frankfurt,
G.A.
Miller
encounter and briefly comprise a system of density
enough
toPhys.Rev.D
beL.comparable
to that
of and M.Strikman, Phys. Rev. C
[3-79] high
C-W.
Hwang,
64(2001)n034001
neutron stars. This relationship will be tested and refined at 12[4-12]
GeV by
seriesetofal.,EMC
andof Color Transparency in Exclusi
K. aHafidi
“Study
[4-1] J. Seely et al., Phys.
Rev. Lett.
103,
(2009)
202301
SRC experiments covering a wide range of nuclei [4-19, 4-20, 4-24,Electroproduction
4-25]. The deuteron
off Nuclei”, Jefferson Lab Experiment
N. (per-nucleon)
Fomin, et al.,
Rev. Lett.
108,
092502 (2012)
experiment
mentioned
[4-18]cross
will increase
our
understanding
of Phys.
the
system
Figure
4.1: The
electronabove
scattering
section[4-2]
ratios
of two-nucleon
various
nuclei
to
that
we
use
as
a
baseline
for
both
the
EMC
and
SRC
measurements.
12 [4-13] E.M. Aitala et al. [E791 Collaboration], Phys. Rev. Lett.
al.,<Phys.
123B
(1983)
deuterium. (a) Ratios for 0.2 < xB < 0.9 [4-1]; (b) [4-3]
RatiosJ.J.
forAubert
C foret0.3
xB < Lett.
2 [4-1,
4-2];
(c) 275
[4-14] L. Frankfurt, G.A. Miller and M. Strikman, Phys. Lett. B
Ratios for 0.8 < xB < 1.8 [4-2].
[4-4] L.B. Weinstein et al., Phys. Rev. Lett. 106, 052301 (2011)
[4-15] B. Clasie, et al., Phys. Rev. Lett. 99, 242502 (2007)
Nucleons acquire high-momentum via short-range
interactions,
influence
of
[4-5]
N. Baillie et rather
al., Phys.than
Rev.by
Lett.the
108,
142001 (2012)
4a.2
Nucleon
properties
in nuclei
relative NN
wave
function
at short distances.
the nuclear mean-field. Thus, for momenta above
Fermi
sea, the
of the
momentum
[4-6]theA.V.
Klimenko
et al.,shape
Phys. Rev.
C 73,
035212 (2006)
distribution should be universal. This is shown by[4-7]
the plateaus
(regions of constant cross section 60
S. Bueltmann et al., “The Structure of the Free Neutron at Large x-Bjorke
ratio) observed at xB > 1.5 (see Figure 4.1c). The values
of the ratio
at these plateaus, a2(A/d),
Lab Experiment
E12-06-113.
are closely related to the probability of finding a[4-8]
nucleon
belonging to a short-range correlated
O. Hen et al., “In Medium Nucleon Structure Functions, SRC, and the EM
pair in nucleus A relative to deuterium.
Jefferson Lab Expt E12-11-107.
Coincidence?
W.understand
Melnitchouk, the
M. Sargsian,
M.I. Strikman,
Experiments at 12 GeV will study the deuteron to[4-9]
better
simplestand
nuclear
systemZ. Phys. A359, 99 (199
El Fassi, et above
al., Phys.
B712,greater
326 (2012)
[4-18]. Other experiments will extend the SRC [4-10]
studiesL.described
toLett.
a much
range
3
3
of xB, momentum transfers, and nuclei (including
H and
He) toG.A.
study
two
three nucleon
[4-11]
L. Frankfurt,
Miller
andand
M.Strikman,
Phys. Rev. C 78, 015208 (2008
correlations
(including
their
isospin
character),
with
higher
nucleon
momenta
[4-19,
4-20].
The
[4-12]
K.plotted
Hafidi
et al.,the“Study
Color
Transparency
in
Figure
4.2: (left) The
strength
of the EMC
effect (the EMC
slope)
versus
averageofnuclear
density
[426Exclusive Vector Meson
2
(right)from
The strength
effect plotted versus
the probe
SRCElectroproduction
scale
factors
[4-4]. off
TheNuclei”,
drawing
in
the upper
highest Q1]. data
the xofB the
> 1EMC
measurements
will
the
distribution
of superfast
quarks
in
Jefferson
Lab Experiment
E12-06-106.
left shows deep inelastic electron scattering from a quark in a nucleon. The drawing in the lower right shows
nuclei, greatly extending our understanding of nucleons
at short
[4-13] E.M.
Aitaladistances.
et al. [E791 Collaboration], Phys. Rev. Lett. 86, 4773 (2001)
Inclusive A(e,e ) measurements
! 
At high nucleon momentum,
distributions are similar in shape for
light and heavy nuclei: SCALING.
nA (k ) = CA ⋅ nD (k )
high k
Adapted from
Ciofi degli Atti
!  Short distance two-nucleon relative wave
function same in all nuclei .
!  One can get the probability of 2N-SRC in any nucleus, from the
scaling factor.
Piasetzky talk
27
Implications of data
• Previous models need to be extended to a
larger range of x
• Detailed nuclear dependence must be
explained (Dutta talk)
• Challenge: is EMC effect best described
as being on single nucleon or a correlated
pair of nucleons?
28
Are nucleons in the SRC modified?
• Need to start with a
nuclear model of SRC and
compute resulting EMC effect caused by modified
structure function
• Medium modification due to mean field (previously
discussed models) alternate hypothesis
29
Phenomenology
Hen et al Int. J. Mod. Phys.E22, (’13)1330017
• Ciofi degli Atti & Simula, PRC53,1689 (96)-nuclear
model- Spectral function has two terms - low
momentum, mean-field MF part 80%, high momentum
short-ranged correlations SRC 20% • Strikman & Frankurt: relate nuclear DIS to nucleon
structure function using spectral function PLB 183,
254 (87) • Modification of nucleon structure function is
associated with MF or with SRC- two models
30
April 11, 2013 0:17 WSPC/INSTRUCTION FILE
EMC˙reviewMar15b
April 11, 2013 0:17 WSPC/INSTRUCTION FILE
Universal modification to nucleon in SRC
The EMC Effect and High Momentum Nucleons in Nuclei
Universal modification to nucleon in MF
21
Which gives a better fit?
31
Int. J. Mod. Phys.E22, (’13)1330017
Fig. 9: The ratios of free to bound structure functions for various nuclei, extracted
EMC˙reviewMar15b
The EMC Effect and High Momentum Nucleons in Nuclei
23
13 0:17 WSPC/INSTRUCTION FILE
M
o
the EMC effect is the unique association with short ranged correlations. Note
9
Be was not included in the model calculations since a 9 Be spectral function
not available. Note also that this model does not separate valence and sea q
distributions and therefore can’t make predictions about the Drell-Yan data.
Further experiments are needed to determine whether the Mean-Field or
(SRC) nucleonsModified
Function
MFquasi-elastic ele
are modified byStructure
the nuclear medium.
For example,
scattering would be sensitive to the former but not the latter.
Modified Structure Functions
Modified Structure Function
O. Hen et al.
([1]* (x-[0])+[2]*(x -[0 ])^2)/((1./5 6)*(5./9 )*1.094*s qrt(x )*(26* 2* (1-x )^3+30*(9./8)* (1-x )^4)+(11./9)* 0.1857*(1-x)^ 7)
([1]* (x-[0])+[2]*(x- [0 ])^2)/((1./5 6)*(5./9 )*1.094*s qrt(x )*(26* 2* (1-x )^3+30*(9./8)*(1-x )^4)+(11./9)* 0.1857*(1-x)^ 7)
N
∆FN
2 / F2
N
∆FN
2 / F2
0
EMC˙reviewMar15b
0.3
0.25
0.04
0.03
0.02
0.01
0.2
0
-0.01
0.15
-0.02
0.1
-0.03
0.05
0.3
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.35
0.7
x
0.4
0.45
0.5
0.55
0.6
0.65
0.7
x
Fig. 10: Same as Fig. 8, assuming universal modification to Mean-Field nucl
It is assumed that deuterium has no Mean-Field component, see text for deta
ig. 8: The ratio of the modification term, ∆F2N to the free nucleon structure
Is the
effect due to nucleons in SRC pairs or to nucleons
unction,
F2NEMC
.
moving in the mean field?
Summary
We next proceed by assuming that nucleons in high energy excited5.states
(corelated nucleons) have a different structure function F!2N (x) than free ones
F
(x).
We have
recent data showing that the detailed A dependence of the
2Nreviewed
hus we make the replacements
effect provides important hints in understanding the origin of that effect. The
(0)
(1)
(0+1)
I1 (A)F2 → I1 (A)F2N + I1 (A)F!2N = I1
(1)
(A)F2N + I1 (A)∆F2N , etc, (19)
here
N
N
32
N
13 0:17 WSPC/INSTRUCTION FILE
M
o
the EMC effect is the unique association with short ranged correlations. Note
9
Be was not included in the model calculations since a 9 Be spectral function
not available. Note also that this model does not separate valence and sea q
distributions and therefore can’t make predictions about the Drell-Yan data.
Further experiments are needed to determine whether the Mean-Field or
(SRC) nucleonsModified
Function
MFquasi-elastic ele
are modified byStructure
the nuclear medium.
For example,
scattering would be sensitive to the former but not the latter.
Modified Structure Functions
Modified Structure Function
O. Hen et al.
([1]* (x-[0])+[2]*(x -[0 ])^2)/((1./5 6)*(5./9 )*1.094*s qrt(x )*(26* 2* (1-x )^3+30*(9./8)* (1-x )^4)+(11./9)* 0.1857*(1-x)^ 7)
([1]* (x-[0])+[2]*(x- [0 ])^2)/((1./5 6)*(5./9 )*1.094*s qrt(x )*(26* 2* (1-x )^3+30*(9./8)*(1-x )^4)+(11./9)* 0.1857*(1-x)^ 7)
N
∆FN
2 / F2
N
∆FN
2 / F2
0
EMC˙reviewMar15b
0.3
0.25
0.04
0.03
0.02
0.01
0.2
0
-0.01
0.15
-0.02
0.1
-0.03
0.05
0.3
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.35
0.7
x
0.4
0.45
0.5
0.55
0.6
0.65
0.7
x
Fig. 10: Same as Fig. 8, assuming universal modification to Mean-Field nucl
It is assumed that deuterium has no Mean-Field component, see text for deta
ig. 8: The ratio of the modification term, ∆F2N to the free nucleon structure
Is the
effect due to nucleons in SRC pairs or to nucleons
unction,
F2NEMC
.
moving in the mean field?
Summary
We next proceed by assuming that nucleons in high energy excited5.states
(corelated nucleons) have a different structure function F!2N (x) than free ones
F
(x).
We have
recent data showing that the detailed A dependence of the
2Nreviewed
hus we make the replacements
effect provides important hints in understanding the origin of that effect. The
I1 (A)F2 →
here
(0)
I1 (A)F2N
+
(1)
I1 (A)F!2N
N
YES
=
N
(0+1)
I1
(A)F2N
(1)
+ I1 (A)∆F2N , etc, (19)
32
N
Requirements & Goals
•
•
•
•
Model the free distributions
Good support
Consistency with nuclear properties
Describe deep inelastic and di-muon
production data- valence plus sea
• describe detailed A (N,Z)
dependence
• Predict new phenomena
Ways to search for medium
modification of nucleon structure
• Quasi-elastic scattering, Coulomb sum rule
form factors of bound nucleons
• Quasi-elastic, recoil polarization- GE /GM
• DIS on deuteron, detect spectator
• A dependence
• Parity violating DIS
34
Summary
• nucleon structure is modified by nucleus
• minimum model requirements- EMC, DY,
nuclear saturation, A-dependence
• predict new phenomena
• needed –better evaluations of models
• experimental tests –form factors
in medium, ( eA ! e0 XN ) spectator tag, PVDIS
nuclear gluon distribution??
• new experiments Jlab and others to
find out how quarks work in a nucleus
Where do we stand after 33 years?
36
Where do we stand after 33 years?
36