E.C. Aschenauer
 Physics deliverable in the EIC-WP:
Quark hadronization: By measuring pion and D0 meson production in both
electron+proton and electron+nucleus collisions, the EIC would provide the
first measurement of the quark mass dependence of the hadronization along
with the response of nuclear matter to a fast moving quark.
But what do we really know about hadronization ?
individual vs. collective phenomena
P1
q(x1)
x1P1
Hard Scattering Process
ŝ
P2
2
x2P2
X
g(x2)
POETIC, September 2015
E.C. Aschenauer
 EIC unique machine to study hadronization
 DIS is sensitive to favored and unfavored FFs
o can still improve significantly collinear FFs
 access to wide kinematic range, x, Q2, pt, z
 detector design foresee wide h coverage (-5 to 5) with PID
 can study correlations between current and target FF region
 can we see a pt (kt), z ordering as predicted by string models
 how to access kt
 Many interesting spin dependent phenomena in FF
 IFF, Collins FF, which manifest themselves in hadron correlations
and azimuthal distributions
 how do they translate from the current to the target
fragmentation region
3
POETIC, September 2015
E.C. Aschenauer
Creating QCD color from pure energy - dynamic confinement
 Can we learn more about the hadronization mechanisms comparing p vs. A?
 Lund string model: expect correlation between rapidity and string position
For Nuclei:
Hadrons near mid-string sample more medium path length.
Look for greater attenuation and broadening in mid-rapidity?
4
POETIC, September 2015
E.C. Aschenauer
 Photo-production in ep/eA is like pp/pA collisions
 ep and eA particle correlations for rare high multiplicity events
 can we see effects as v2n like in pp and p(d)A
 can we see the “ridge” in such events
 Do these effects go away with Q2 increasing
-5<eta<5, all final states
Dpmjet eA
Dpmjet ep
Pythia ep
will put strong constrains on
theoretical models
 IS vs. FS effects
5
POETIC, September 2015
E.C. Aschenauer
4 different contributions to the pt of a hadron
 kt: non-pertubative; very often called “intrinsic”
 ktPS: from parton showers  connection to softfactors in TMDs
 ptfrag: pt contribution from the fragmentation
 pthard : from hard QCD scattering (QCDC, PGF, …)
How to disentangle the different contributions?
6
POETIC, September 2015
E.C. Aschenauer
for the first time very precise multidimensional data (x, Q2, pt, z)
BUT:
Multiplicities at forward rapidities mix initial, final and QCD effects creating pt
Need observables which distinguish different contributions
7
POETIC, September 2015
E.C. Aschenauer
T
<p2 >
Chgd. hadrons Q 2>1.0 GeV2 15x100 ep
0.7
0.7
Full QCD on (std) EIC det. acceptance
pQCD, NO PS EIC det. acceptance
0.6
0.6
PS only EIC det. acceptance
No QCD EIC det. acceptance
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
2
0.4
0.6
0.8
2
T
<p2 >
Chgd. hadrons Q >1.0 GeV 15x100 ep
0
1
xF
kT = 1.3 GeV EIC det. acceptance
1.4
1.4
kT = 0.88 GeV EIC det. acceptance
1.2
1.2
kT = 0.44 GeV EIC det. acceptance
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
-1
8
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0
1
x
POETIC,
F
0.8
xF>0: “struck” parton hemisphere
xF<0 “target remnant” hemisphere
sensitive to intrinsic kts (initial +
fragmentation)
What else can be learnt
from xF<0 region?  Harut’s talk
September 2015
E.C. Aschenauer
First a small detour about jets at EIC in general
 all plots are for 20x250 GeV on pythia pseudo-data
 anti-kt as included in fast-jet and all the experience for jets in pp@STAR
 use PGF and QCD as example processes
rapidity
9
POETIC, September 2015
E.C. Aschenauer
can jets help to disentangle different contributions to pt
 initial, final state and QCD radiation
Alternative observable:
X1
1<Q2<10
P2
10<Q2<100
10
1<Q2<10
P1
X2
POETIC, September 2015
Y1
Y2
XTot = (X1/P1) + (X2/P2)
YTot = (Y110<Q
/P1) +
(Y2/P2)
2<100
Imbalance = √(XTot2 + YTot2)
E.C. Aschenauer
DIS jets very clean  low underlying event
 Linearly polarized gluons
A. Dimutru et al. http://arxiv.org/abs/1508.04438
 Jet tomography
 study parton radiation of heavy quarks vs light ones
in ep vs eA
 parton energy loss
 first direct test of parton shower evolution
 essential of MC generators
 pQCD inspired
kt vs. angular ordering
 and ……….
11
POETIC, September 2015
E.C. Aschenauer
e
k⊥<<pt
qqbar interacts like g
“Correlation limit”
study charm
to tag PGF
The Gluon Sivers Function:
γ*p⇑ → D0bar+D0 + X
Measure a pair
of D mesons
k⊥ = |k1T + k2T|
PT = (k1T - k2T) / 2
Statistically
challenging
p⇑
k’=0.75GeV
0.4 Single Spin Asymmetry
g N­-->DD+X
~8 months with
50% efficiency and
L = 1034cm2s-1
0.2
0
-0.2
 Beam Energies: 20 GeV x 250 GeV
 Q2: 1 – 10 GeV2, y: 0.01 – 0.95, z>0.25
-0.4
 no cut on k⊥ and pt,
but on k⊥/pt < 0.5 for “correlation limit”
12
k’=1.5 GeV
0
POETIC, September 2015
2
4
f
E.C. Aschenauer
Sk’
6
Unpolarized and polarized photon structure
unpolarized:
arXiv:9504004, arXiv:9710018, Eur. Phys. J. C 10, 363{372 (1999), DESY 97-164
polarized:
no data
theory: Z. Phys. C 74, 641—650 (1997) and arXiv:971125
13
POETIC, September 2015
E.C. Aschenauer
H1 and ZEUS
sr, NC x 2
i
small x
10 7
–1
HERA NC e–p 0.4 fb
+
–1
HERA NC e p 0.5 fb
Ös = 318 GeV
Fixed Target
HERAPDF2.0 e–p NNLO
HERAPDF2.0 e+p NNLO
10 6
10 5
10 4
10 3
10 2
xBj = 0.032, i=7
xBj = 0.05, i=6
xBj = 0.08, i=5
10
xBj = 0.13, i=4
xBj = 0.18, i=3
10
10
s~s0.096
xBj = 0.25, i=2
1
10
g(x, Q2 )
xBj = 0.00005, i=21
xBj = 0.00008, i=20
xBj = 0.00013, i=19
xBj = 0.00020, i=18
xBj = 0.00032, i=17
xBj = 0.0005, i=16
xBj = 0.0008, i=15
xBj = 0.0013, i=14
xBj = 0.0020, i=13
xBj = 0.0032, i=12
xBj = 0.005, i=11
xBj = 0.008, i=10
xBj = 0.013, i=9
xBj = 0.02, i=8
xBj = 0.40, i=1
-1
-2
large x
counting
partons
xBj = 0.65, i=0
-3
1
10
10
2
10
3
10
4
10
5
2
Q / GeV
14
2
POETIC, September 2015
unresolved objects
Q2=Q2eff
E.C. Aschenauer
50
2
g1(x,Q ) + const(x)
-5
x=5.2´10 (+52)
40
DSSV+
-5
8.2´10 (+43)
EIC 5´100
-4
EIC 5´250
1.3´10 (+36)
EIC 20´250
covered by
present data
-4
2.1´10 (+31)
30
3.3´10-4 (+27)
-4
5.2´10 (+24)
-4
8.2´10 (+21)
1.3´10-3 (+19)
20
3.3´10-3 (+15.5)
-3
5.2´10 (+14)
-3
8.2´10 (+13)
1.3´10-2 (+12)
-2
2.1´10 (+11)
-2
3.3´10 (+10)
-2
5.2´10 (+9)
-2
8.2´10 (+8)
-1
1.3´10 (+7)
-1
2.1´10 (+6)
-1
3.3´10 (+5)
-1
5.2´10 (+4)
10
15
1
POETIC, September 2015
10
10
2
10
3
Q Aschenauer
[GeV ]
E.C.
2
2
BNL EIC Science Task Force
2.1´10-3 (+17)
In high energy ep collision, two types of processes lead to the production of
jets:
direct: point-like photon
resolved: hadronic photon
 Di-hadron/di-jets measurements in photon-production will
investigate the photon structure
 Direct/resolved contributions can be separated.
 Resolved photon contribution provides a sensitive
way of determining the parton distribution in the
photon.
16
POETIC, September 2015
DESY 97-196
E.C. Aschenauer
Di-jet method
LAB
102
6
hasso
LAB
hasso
Di-hadron method
6
5
4
4
10
3
10
2
2
1
0
1
0
1
-1
-2
-2
-4
-4
-2
0
2
4
10-1
-3
-3
6
-2
-1
0
1
2
3
4
LAB
´10
direct
[pb]
7
LAB
resolved
trig
8
6
5
6
LAB
´10
3
ds/dh
LAB
ds/dh
trig
[pb]
3
5
htrig
h
trig
3.5
3
2.5
2
4
1.5
3
2
1
1
0.5
0
-4
-2
0
2
4
6
8
0
-4
h
trig
-2
-1
0
1
2
3
4
5
htrig
LAB
pTtrig>2GeV , pTasso>1GeV
-3
LAB
pTtrig>4GeV, pTasso>3.5GeV
For both methods:
 At positive ηLAB especially ηLAB>2, the cross section is dominated by resolved
process.
 Direct contributions for cross section dominates at negative ηLAB.
17
POETIC, September 2015
E.C. Aschenauer
xbparton
Di-hadron method
Di-jet method
1
0.9
0.8
102
0.7
0.6
0.5
0.4
10
0.3
0.2
0.1
0
0
1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
xrec
g
 Both di-hadron and di-jet methods can
help us separate resolved/direct process.
 Di-jet method provides a better way to
reconstruct xγ.
18
POETIC, September 2015
E.C. Aschenauer
Parton momentum fraction in photon:
Di-hadron method
If we choose different xrec cut,
how well can we separate
resolved/direct processes:
´10
counts
3
1.6
resolved
1.4
direct
Nres/Ntot
1.2
1
0.8
0.6
1
0.95
dijet
0.4
0.9
0.2
0
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0.85
0.8
dihadron
300
0.75
250
100
50
0
19
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
x rec<0.9
x rec<0.8
x rec<0.7
x rec<0.6
x rec<0.5
x rec<0.4
x rec<0.3
150
x rec<0.2
0.7
200
x rec<0.1
counts
Di-jet method
1
xrec
g
 small xγ : mainly resolved contribution
 large xγ : mainly direct contribution.
xrec
POETIC, September 2015
E.C. Aschenauer
 Low Q2 tagger
hadrons
z = - 45m
- 35m
electrons
- 15m
- 4m 0m 4m
18m
38m
´10
6
Q2[GeV2]
6
1
5
10-1
 acceptance
for
4
electrons
down
3
to Q2~1x10-5 GeV2
10-2
pythia events
with electron
10-3
reconstructed
in the tagger
10-4
10-8
10-7
2
 verify assumptions in
1
WW
10-6
10-5
10-4
10-3
10-2
10-1
0
x
 lepton beam polarisation
 redo everything for polarised photons  PDFs
 no data at all  desperately needed for gg option of ILC
20
POETIC, September 2015
E.C. Aschenauer
Hadron Spectroscopy
21
POETIC, September 2015
E.C. Aschenauer
 EIC - rich source for real photon beam in a broad high-energy range
 Photon beams are expected to be favorable for the production of exotic
states as the photon effectively behaves like a vector meson. Vector mesons
can be excited via an extra gluonic degree of freedom to both ordinary and
exotic quantum number JPC states
 Polarization of photons at EIC helps in determining the spin-parity of the
measured system by giving direct information on the production mechanism and
therefore largely reducing potential ambiguities
 JLab 12 GeV upgrade to map the spectrum of light and strange quark hybrid
mesons
 EIC - High luminosity, broad energy range, polarization, detector capability:
suitable for spectroscopy including heavy quark/charm sector
22
POETIC, September 2015
E.C. Aschenauer
 gp
 Recent discoveries of charmonium-like
“exotic” “XYZ” states at BaBar, Belle,
BESIII, CLEO, LHCb…
 cannot be easily accommodated in the
c-cbar scheme - underlying structure is
unclear
 New and independent production
mechanism for the XYZ states provides
new insight into the nature of the
exotic states
 γp➝Zc+(3900)n, Zc+(3900)➝J/ψπ+
 γp➝Zc+(4430)n, Zc+(3900)➝ψ’π+
 γp➝Zc+(4200)n, Zc+(3900)➝J/ψπ+
 γp➝Y(3940)p, Y(3900)➝J/ψω
 Discovery potential for new states
23
POETIC, September 2015
E.C. Aschenauer
 Zc photoproduction is predicted to
be enhanced at near the
threshold - suitable for the EIC
energy range
 At higher energy - photonpomeron background dominates
EIC
 At JLab12 GeV (max √sγp = 4.8
GeV) - highly suppressed
 Exclusive reconstruction of J/ψ,
π, n in the acceptance of the
current EIC detector design
background
p
 predicted cross-section ~ O(0.01
μb) - high statistics sample within
reach at EIC
PRD88 114009 (2013) Q. Lin et al.
24
POETIC, September 2015
E.C. Aschenauer
Compton backscattering:
 collision of a high-power, approximately optical wavelength laser beam
with an intense, high-energy electron beam
 gs closely follow the original trajectory of the electron beam.
 The original electrons are degraded substantially in energy,
but also continue approximately on their original path.
 small lepton beam bunch sizes + laser with 1-5 J of laser flash energy
 Ng/Ne ~ 1  same lumi as in ep collisions
Beamstrahlung:
emission of a real photon by an electron (positron) as it traverses the
strong electromagnetic field in the opposing proton bunch in an ep (eA) collider.
Coherent Bremsstrahlung: (used at Hall-D@JLab)
 the photon beam is produced by having a low-emittance electron beam
incident on a thin (~ 20 μm) diamond wafer. A small fraction, about 0.01%
of the electrons, emit a photon via incoherent or coherent bremsstrahlung
 thickness of the diamond wafer  photon beam luminosity
 By collimation of the photon beam can be used to enhance the fraction of
photons of the coherent radiation. This has the effect and the degree of
linear polarization
25
POETIC, September 2015
E.C. Aschenauer
 The EIC whitepaper has
demonstrated the potential of the
EIC to provide definitive answers to
outstanding questions regarding
fundamental structure of matter
 The full range of scientific
opportunities offered by such a
versatile machine are only beginning
to be realized…
26
EIC WP
New opportunities
POETIC, September 2015
E.C. Aschenauer
BACKUP
27
POETIC, September 2015
E.C. Aschenauer
“Simple” measurement giving access to multi-parton correlations
pTtrig
 saturation
Same observable as in dA @ RHIC
pTassoc 
0.45
Zheng et al., PRD89 (2014) 074037
0.4
10 GeV x 100 GeV
Q2 = 1 GeV 2
beam-view
ep, No Sudakov
eAu, No Sudakov
0.35
ep, With Sudakov
C(Df)
0.3
eAu, With Sudakov
0.25
0.2
0.15
0.1
0.05
0
2.4
2.6
2.8
3
3.2
3.4
3.6
Df [rad]
Fully based on:
Dominguez et al. PRD83, 105005 (2011),
PRL 106, 022301 (2011)
3.8
0.45
0.4
T
>2 GeV/c
1 GeV/c <passoc <ptrig
0.35
0.3
C(Df)
p
trig
0.25
T
T
trig
0.2<z h , zassoc <0.4
2
h
2
1 GeV <Q <2 GeV
0.6<y<0.8
0.2
0.15
2
Advantage of eA over p(d)A:
 eA
experimentally
much cleaner20 GeV x 100 GeV
10 GeV
x 100 GeV
 no “spectator” background to subtract
sat
 Access to the exacteAu
kinematics
of the
2
2
2
DIS process (x,Q ) Qs/2,2*Q s
 only process sensitive to WW gluon
distribution G1(x,kT,Q2)
ep
0.1
0.05
0
28
2
2.5
3
3.5
Df [rad]
POETIC, September
2015
4
4.5
2
2.5
3
3.5
4
Df [rad]
E.C.
Aschenauer
4.5
(Phys.Lett.B322(1994))
 (b) Single inclusive jet / (c) Dijet h distribution.
 At positive h, the cross section is dominated by resolved contribution.
xrecγ =(ΣpT×e-h)/2yEe
 small xγ region dominated by resolved contribution, otherwise, direct
contribution.(DESY 97-169)
29
POETIC, September 2015
E.C. Aschenauer
Why we choose SAS, ACFGP, LAC:
 GRV closest to HERA data
Photon PDF set
DO-G LO
LAC-G/GAL-G
LO
GS-G LO
GS-G-96 LO
GRV-G/GRS-G
LO
ACFGP/AFG-G
NLO
WHIT-G LO
SAS-G(v1/v2) LO
30
POETIC, September 2015
E.C. Aschenauer
Di-jet pT distribution:
passo [GeV]
109
108
107
T
T
T
dN/(p dp ) [GeV-2]
jet pT distribution:
106
105
14
12
102
10
8
4
10
6
10
103
4
102
2
10
0
2
4
6
8
10
12
14
16
18
20
0
0
2
4
6
8
10
12
14
1
ptrig [GeV]
p [GeV]
T
T
ptrigT>4GeV , passoT>3.5GeV
31
POETIC, September 2015
E.C. Aschenauer
 ep and eA particle correlations for rare high multiplicity
events
 can we see effects as v2n like in pp and p(d)A
-5<eta<5, all final states
Dpmjet eA
Dpmjet ep
Pythia ep
32
will put strong constrains on
theoretical models
 IS vs. FS effects
POETIC, September 2015
E.C. Aschenauer
Transverse momentum dependent distributions (TMD)
33
POETIC, September 2015
E.C. Aschenauer
observable: azimuthal modulations
of 6-fold differential SIDIS cross section
• theoretically interesting multi-scale problem: Q2, pT
• TMD framework/factorization applicable for Q2 >> pT
• so far if at all only valence quark TMDs
extracted from fixed target data
• very different evolution then collinear PDFs
pertubative & non-pertubative contributions
• slew of different TMDs can be defined
example: Sivers function
Leading
Twist TMDs
Spin
Quark Spin
correlation
of nucleon’sNucleon
transverse
spin
Quark Polarization
with the kT of an
unpolarized quark
modulation
unpolarised TMD
Nucleon Polarization
Un-Polarized
(U)
U
Longitudinally Polarized
(L)
h1┴ =
ƒ1 =
g1L =
h1L┴ =
h1 =
—
g1T┴ =
—
—
Sivers function
Transversity
—
• measures spin-orbit correlations
Sivers
34
—
Helicity
ƒ1T┴ =
—
Boer-Mulders
L
T
Transversely Polarized
(T)
—
h =
important link to physics of
• link to parton orbital motion (through models)
gluon saturation at Similar
small xfor gluons
• reveals non-trivial aspects of QCD color gauge
POETIC, September
2015
invariance
┴
1T
E.C. Aschenauer
eRHIC:
large x,Q2,pT and z coverage
 only place to measure data
to pin down TMD evolution
 only place to
test theoretical concepts of
TMD to collinear TWIST-3
three-parton correlation functions
eRHIC vs. world coverage
Collinear
Twist-3
Q,QT>>LQCD
pT~Q
TMD
Q>>QT>=LQCD
Q>>pT
LQCD
shows emerges of a scale Qs
where gluon density saturates
35
<< QT/PT <<
Q
QT/PT
• unintegrated gluon density g(x,Q2,kT) important
for physics at small x
 CGC
 many applications at LHC
Important: eRHIC ideal machine to understand
transition form low to high kT
?
POETIC, SeptemberWhat
2015 are the best observables
E.C. Aschenauer
11:
12:
13:
28:
53:
68:
fi fj -> fi fj
fi fi_bar -> fk fk_bar
fi fi_bar -> g g
fi g -> fi g
g g -> fk fk_bar
g g -> g g
131:
132:
135:
136:
36
fi γT* -> fi g
fi γL* -> fi g
g γT* -> fi fi_bar
g γL* -> fi fi_bar
91:
92:
hQCD 93:
94:
95:
Gamma
Elastic
Single Diffraction (xB)
Single Diffraction (Ax)
Double Diffraction
Low-pT Production
99: γ*q -> q
POETIC, September 2015
sQCD
DIS
E.C. Aschenauer
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