Transcript Semi-Inclusive Physics at the Electron

Semi-Inclusive Physics at
the Electron-Ion Collider
2007 Long-Range Plan
EIC: “half” recommendation
2010 JLab User
Workshops
2014 Joint Halls A/C Summer Meeting
Jefferson Lab – June 5-6, 2014
INT10-3 program
>500 page report
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Rolf Ent (JLab)
EIC white paper
arXiv:1212.17010 (v2)
Semi-Inclusive Physics at the Electron-Ion
Collider (EIC*)
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The Worldwide Quest for Electron-Ion Colliders
Into the “Sea”: the EIC* Science
Semi-Inclusive Physics – Nucleon Structure
The Utilization of Nuclear Beams
* EIC is the generic name for the Nuclear Science-driven Electron-Ion Collider, presently considered in the US
EIC
= QCD Mass Explorer
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of the atomic nucleus
Electron Ion Colliders
Past
Possible Future
Europe
China
EIC
CEIC
LHeC@CERN
ECM (GeV)
320
800-1300
70-150
12-70  140
12  65
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proton xmin
1 x 10-5
5 x 10-7
4 x 10-5
5 x 10-5
7 x10-3 3x10-4
5 x 10-3
ion
p
p to Pb
p to U
p to Pb
p to U
p to ~40Ca
polarization
-
-
p, 3He
p, d, 3He (6Li)
p, d, 3He
p,d
L [cm-2 s-1]
2 x 1031
1033-34
1033  1034
1034-35
1032-33  1035
1032
2
1
2+
2+
1
1
1992-2007
2025
2025
Post-12 GeV
2019  2030
upgrade to FAIR
Figure-8
Figure-8
Year
Followed by
FCC-he?
High-Energy Physics
MEIC@JLab
HIAF@CAS
Europe
HERA@DESY
IP
eRHIC@BNL
US
Hadron Physics
Note: xmin ~ x @ Q2 = 1 GeV2
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ENC@GSI
Dormant
The CM Energy vs Luminosity Landscape
CEIC1 = Chinese version
of Electron-Ion Collider
(“A dilution-free mini-COMPASS”)
MEIC1 = EIC@Jlab
eRHIC = EIC@BNL
LHeC = ep/eA collider
@ CERN
CEIC2
MEIC2
HL-eRHIC
FCC-he
4
}
future
extensions
EIC vs LHeC
EIC: L = about 1034 cm-2s-1
Ecm = 20- ~100 GeV
• Variable energy range
• Polarized and heavy ion beams
• High luminosity in energy region
of interest for nuclear science/QCD
world’s first polarized e-p collider
and world’s first e-A collider
LHeC: L = 1033-34 cm-2s-1
Ecm ~ 1 TeV
• Add ~60 GeV electrons to LHC
• Use IP2 interaction region
• High luminosity takes benefit of
large g’s (= E/m) of beams
high-energy e-p collider to follow on
DESY, plus plans for e-A collider
xmin ~ 1 x 10-4
xmin ~ 5 x 10-7
Small x
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High Q2
Understanding QCD and the Origin of Mass
 Nuclear Science: to discover, explore, and understand all forms of
nuclear matter and its benefits to our society
 Nuclear matter:
 the nucleus
 the nucleons
 the quarks and gluons
 QCD:
A fundamental theory for the dynamics of quarks and gluons
It describes the formation of all forms of nuclear matter
 QCD and the Origin of Mass
– 99% of the proton’s mass is due to
the self-generating gluon field
– Higgs mechanism has almost no role here
– M(up) + M(up) + M(down) ~ 10 MeV << M(proton)
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The Structure of the Proton
Naïve Quark Model: proton = uud (valence quarks)
QCD:
proton = uud + uu + dd + ss + …
The proton sea has a non-trivial structure: u ≠ d
& gluons are abundant
gluon dynamics
Non-trivial sea structure
 The proton is far more than just its up + up + down (valence) quark structure
 Gluon
photon:
and recombines:
Radiates
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Into the “sea”: the EIC
US-based Electron-Ion Collider EIC design and range driven by:
access to sea quarks and gluons
 s = ECM2 = few 100 - 1000 GeV2 seems right ballpark
 s = few 1000 allows access to gluons, shadowing
Polarization + good acceptance to detect spectators & fragments
An EIC aims to study the sea quarks and
gluon-dominated matter.
EIC
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EIC: Physics – see EPJA 48 (2012) 92;
(Jlab theory paper on MEIC science;
arXiv:1212.17010 (v2)
EIC White Paper)
Explore and image the spin and
3D structure of the nucleon
(show the nucleon structure picture of the day…)
Needs high (polarized) luminosity and
range of energies: s ~ 500-5000+
Discover the role of gluons in
structure and dynamics (without gluons
there are no protons, no neutrons, no atomic nuclei)
Needs range of ions up to A ~ 200
and energies: s ~ 1000-10000
Understand the emergence of hadrons
from color charge
(how does M = E/c2 work to create pions and nucleons?)
Needs access to ion fragments and
energy: s ~ few 100-few 1000
Search for physics beyond the Standard Model
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Needs energy & ultra-high polarized luminosity
World Data on F2p
World Data on g1p
World Data on h1p
FUTsin(fh+fs)(x,Q2) + C(x) ∝ h1
COMPASS
HERMES
momentum
spin
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transverse spin ~
angular momentum
g1(Q2) and xDg at an EIC
DIS
5 x 250 starts here
5 x 100 starts here
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Q2 = 10 GeV2
Helicity (collinear) PDFs at an EIC

g1L 
g1L 

kt-integrated pdfs
current data
DG
w/ EIC data
DS
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Sea Quark Polarization
}
• Spin-Flavor Decomposition of the Light Quark Sea
Needs intermediate √s ~ 30 (and good luminosity)
| p
>=
u
u
d
u
+
u
u
u
u
+
d
d
u
d
d
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+ …
Many models
predict
Du > 0, Dd < 0
3D Parton Distributions: TMDs
A surprise of transverse-spin experiments
 Access orbital motion of quarks
 contribution to the proton’s spin
 Observables: Azimuthal asymmetries due
to correlations of spin q/n and transverse
momentum of quarks
quark polarization
h1
f1
Boer-Mulders
g1L
L
helicity
T
T
f1T
Sivers
g1T
h1L
worm-gear
T
nucleon polarization
T
T
Illustration of the
possible correlation
between the internal
motion of an up quark
and the direction in
which a positivelycharged pion (ud)
flies off.
U
L
T
U
h1, h1T
worm-gear
transversity pretzelosity
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TMDs Accessible through Semi-Inclusive Physics
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Separate Sivers and Collins effects
Naturally, two scales:
• High Q: localized probe
to “see” quarks and gluons
• Low PT: sensitive to confining scale
target angle
to “see” their confined motion
+ Theory input: TMD QCD factorization
TMD QCD evolution
hadron angle
•
•
•
Sivers angle, effect in distribution function: (fh-fs)
Collins angle, effect in fragmentation function: (fh+fs)
Or other combinations: Pretzelosity: (3fh-fs)
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TMD Landscape at an EIC: Sivers as example
(
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√s ~ 15 GeV
√s ~ 45 GeV
√s ~ 140 GeV ) upgraded EIC
TMD at an EIC: Experimental Intermezzo
DIS
Accessible (x,Q2) phase space directly correlated with y
Can determine scattering kinematics (x, Q2) from:
Electron kinematics method
y (=E’/E) > 0.01
Hadron X kinematics method
y (=E’/E) < 0.01
X
(as resolution Dx blows up at small y with electron method)
x = Q2/ys
TMD
Need to determine
(fh-fs), (fh+fs), (3fh-fs)
PT
PT
sin fh 

Ph zyPe
On the other hand, to
determine the
scattering kinematics:
tan q ~
pe
Q
~
pe  pe' ype
 tan q y 1 pe'
~
~
tan q
y y pe'
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Work it out, one needs high y!
 one can not use hadron X
kinematics method to do TMD
measurements
 Use versatility of EIC to get
range in √s (=15, 45, 100)
Sivers
Imaging the Transverse Momentum of Quarks into the Sea
u
u
Only a small subset of
the (x,Q2) landscape
has been mapped here:
terra incognita
Gray band: present
“knowledge”
Purple band: EIC (2s)
An EIC with good
luminosity & high
transverse polarization
is the optimal tool to to
study this!
(Distortion of quark distribution
due to nucleon polarization)
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Sivers effect: sea contributions
(Harut Avakian)
GRV98, DSS FF
M. Anselmino et al
arXiv:0805.2677
GRV98, Kretzer FF
S. Arnold et al
arXiv:0805.2137
• Negative Kaons most sensitive to sea contributions.
• Biggest uncertainty in experimental measurements (K- suppressed at large x).
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Correlation between Transverse Spin and
Momentum of Quarks in Unpolarized Target
Transition from low pT (TMD
factorization) to high pT
(collinear factorization)
All Projected Data
Perturbatively
Calculable at
Large pT
Assumed
100 days
of 1035
luminosity
Vanish like
1/pT (Yuan)
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Access to the Gluon TMDs
Access to gluon TMDs may be possible by:
• Di-jet/di-hadron production
• Heavy quark production
• Quarkonium production
Example:
Integrated luminosity of 100 fb-1
where both D and D are in the current
fragmentation region, with momentum
k1 and k2, respectively, and N is a
transversely polarized nucleon.
Gluon Sivers will introduce an
azimuthal asymmetry correlating
k’ = k1 + k2 of the DD pair
with the transvers polarization S
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Hadronization – semi-inclusive physics in a nucleus
un-integrated parton distributions
EIC: Understand the
conversion of quarks and
gluons to hadrons through
fragmentation and breakup
current
fragmentation
Fragmentation
from
QCD vacuum
target
fragmentation
EIC: Explore the interaction
of color charges with matter
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+h ~ 4
E
I
C
-h ~ 4
e - A Physics Landscape at an EIC
12 GeV electrons and 40 GeV (= 100 GeV*Z/A) heavy ions  √s ~ 45 GeV
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Hadronization – energy loss
How do hadrons emerge from quarks or gluons?
Wide range of n and Q2 possible
Neutralization of color – hadronization
Different for light and heavy quarks?
(Controlled access to current quarks and correlation with fragments)
Need the collider energy of EIC and its control on parton kinematics
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Hadronization – parton propagation in matter
p+
e’
e
DpT2
Accardi, Dupre
pT
g*
L
DpT2 = pT2(A) – pT2(2H)
“pT Broadening”
Comprehensive studies possible:
• wide range of energy v = 10-1000 GeV
• wide range of Q2: evolution
• Hadronization of charm, bottom
• High luminosity for 3D and correlations
EIC: Understand the conversion of
color charge to hadrons through
fragmentation and breakup
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Color neutralization – it’s a correlated 3D problem
Can we learn more from
correlating with the target
fragmentation region?
Final transverse momentum of the detected
pion Pt arises from convolution of the struck
quark transverse momentum kt with the
transverse momentum generated during the
fragmentation pt.
Dup+(z,pt)
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EIC Scientific Assessment
From 2013 NSAC Subcommittee of Facilities, chaired by Bob Redwine (MIT):
(US Nuclear Science Advisory Committee)
“ The EIC would be a unique and powerful microscope to provide a
dynamical mapping of gluons in the nucleon and in nuclei. It is an ideal tool
to investigate the mechanism of how quarks and gluons propagate in
nuclear matter and join together to form hadrons. The EIC is our portal to
an in-depth and fundamental understanding of gluonic matter and of QCD.
As stated in the 2007 Long Range Plan, "An EIC with polarized beams
has been embraced by the U.S. nuclear science community as embodying
the vision for reaching the next QCD frontier."
The Subcommittee ranks an EIC as Absolutely Central in its ability to
contribute to world-leading science in the next decade.”
• NSAC Long-Range Planning Effort in the US just started
(April 24), hope to get a recommendation to build the EIC.
• EIC Workshop at Stony Brook University June 24-27, 2014
http://skipper.physics.sunysb.edu/~eicug/meetings/SBU.html
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Early Physics examples at EIC: √s ~ 45 GeV
current data
w/ EIC data
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Semi-Inclusive Physics Outlook
• This is a defining period for the EIC with the LRP started
• EIC science requires polarization & luminosity & detection capability.
EIC allows a unique opportunity to make a (textbook) breakthrough in
nucleon structure and QCD dynamics
•
•
•
explore and image the 3D (spin) structure of the nucleon
discover the role of gluons in structure and dynamics
understand the emergence of hadrons from color charge
Specifically, for semi-inclusive physics:
• Next decade gets important input from COMPASS, JLab-12 GeV (Halls A,
B and C), RHIC-spin, FNAL Polarized Drell-Yan?
• EIC will allow unprecedented measurements, making explicitly use of
longitudinally and transversely polarized beams and correlating current
and target fragmentation regions, e.g., of:
•
•
•
•
Completion of quark flavor decomposition of proton spin
Detailed mapping of valence and sea quark TMDs
First-ever (?) measurement of gluon TMDs
Detailed studies of energy loss and understanding of fragmentation in nuclei
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EIC Design Specs
Base EIC Requirements per Executive Summary INT Report:
• highly polarized (>70%) electron and nucleon beams
• ion beams from deuteron to the heaviest nuclei - uranium or lead
• center of mass energies from about 20 to about 150 GeV
• maximum collision luminosity ~1034 e-nucleons cm-2 s-1
• possibilities of having more than one interaction region
• non-zero crossing angle of colliding beams
• staged designs where the first stage would reach √s of ~70 GeV
• the possibility to have multiple interaction regions
Base EIC Requirements per Executive Summary EIC White Paper:
• highly polarized (~70%) electron and nucleon beams
• ion beams from deuteron to the heaviest nuclei (uranium or lead)
• variable center of mass energies from √s ~ 20 to √s ~ 100 GeV,
upgradable to ~150 GeV
• high collision luminosity ~1033-34 e-nucleons cm-2 s-1
• possibilities of having more than one interaction region
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To cover the physics we need…
arXiv:1212.17010 (v2)
(x,Q2) phase space directly
correlated with s (=4EeEp) :
x = Q2/ys
Most science plots in
white paper for:
√s ~ 45 GeV
Some for √s ~ 140
@ Q2 = 1 lowest x scales like s-1
@ Q2 = 10 lowest x scales as 10s-1
Need for good polarized
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luminosity