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Nuclear Physics at Jefferson Lab
Part III
R. D. McKeown
Jefferson Lab
College of William and Mary
Taiwan Summer School
June 30, 2011
Outline
• Meson spectroscopy
and confinement
• Nucleon tomography
• Electron Ion Collider
2
Quantum Numbers of Hybrid Mesons
Excited
Quarks
Hybrid Meson

Flux Tube
S0

L 0
J
PC
J PC  0  
like

1
   

1
J
PC


1
   

1
, K
Exotic
S 1
L 0
J
J PC  1 
like
PC


1

   

1
J
PC




0
1
2

      

0 1 2
, 
Flux tube excitation (and parallel quark spins) lead to exotic JPC
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3
Decay of Exotic Mesons
Possible daughters:
L=1: a,b,h,f,…
L=0:,,,,…
The angular momentum in
the flux tube stays in one of
the daughter mesons (L=1)
and (L=0) meson, e.g:
flux tube L=1
quark L=1
Example: 1→b1
→ (3)
or → ()
simple decay modes such as ,, … are suppressed.
4
4
Previous “Evidence” for 1-+ Exotic
BNL 852 (18 GeV -)
Results are sensitive to
assumption about background
partial waves
not robust
 not supported by COMPASS
5
Graphical Processor Units for LQCD
• Crays/BlueGene for Gauge Generation - capability
• GPUs for physics measurements - capacity
(ARRA)
6
Isovector Meson Spectrum
Hall D@JLab
States with Exotic Quantum Numbers
2 +0 +1 -+
Dudek et al.
7
Lattice vs. Models
Lattice
8
9
R. McKeown - MENU10
9
Proton Spin Puzzle
DIS → DS  0.25
HERMES
[X. Ji, 1997]
10
10
Spinning Gluons?
RHIC p + p data
 gluon polarization
Global Fit
D. de Florian et al., PRL 101 (2008) 072001
Well maybe not….
11
Proton Spin Puzzle
X X
[X. Ji, 1997]
Consider orbital angular
momentum
 Consider transverse momenta
12
12
6D Dist.
Wpu(x,kT,r ) Wigner distributions
d2kT drz
d3r
TMD PDFs
GPDs/IPDs
f1u(x,kT), .. h1u(x,kT)
3D imaging
d2 k
T
PDFs
f1u(x), .. h1u(x)
d2rT
1D
13
dx &
Fourier Transformation
Form
Factors
GE(Q2),
GM(Q2)
Beyond form factors and quark distributions –
Generalized Parton Distributions (GPDs)
X. Ji, D. Mueller, A. Radyushkin (1994-1997)
Proton form factors,
transverse charge &
current densities
Correlated quark momentum and helicity
distributions in transverse space - GPDs
Structure functions,
quark longitudinal
momentum & helicity
distributions
~
~
4 GPDs: H(x,x,t), E(x,x,t), H(x,x,t), E(x,x,t)
R. D. McKeown June 15,
14
14
Link to DIS and Elastic Form Factors
Form factors (sum rules)
DIS at x =t=0
H q ( x,0,0)  q( x)
~
H q ( x,0,0)  Dq( x)
( x, x, t)
]
 F1 ( t ) Dirac f.f.
( x, x, t)
]
 F2 ( t) Pauli f.f.
 dx[H
q
 dx[E
q
1
q
1
q
1
1
1
1
~q x 
~q x 
dx
H
(
x
,
,
t
)
G
(
t
)
,
dx
E
,
A
q

 (x, , t) GP,q ( t)
~ ~
H q , Eq , H q , E q ( x,x , t )
Angular Momentum Sum Rule
Jq
1
 1  J G = 1  xdx H q( x, x,0)  E q(x, x,0)
2
2 1
[
]
X. Ji, Phy.Rev.Lett.78,610(1997)
15
3 dimensional imaging of the nucleon
Deeply Virtual Compton Scattering (DVCS)
hard vertices
x+x

x-x
x – longitudinal quark
momentum fraction
2x – longitudinal
momentum transfer
–t – Fourier conjugate
to transverse impact
parameter
t
GPDs depend on 3 variables, e.g. H(x, x, t). They describe
the internal nucleon dynamics.
16
Cleanest process: Deeply Virtual Compton Scattering
s  s 
Ds
A = s s =
2s
hard vertices
ξ=xB/(2-xB)
t
Polarized beam, unpolarized target:
~
DsLU~ sinf{F1H+ ξ(F1+F2)H+kF2E}df
Unpolarized beam, longitudinal target:
~
DsUL~ sinf{F1H+ξ(F1+F2)(H+ξ/(1+ξ)E)}df
H(x,t)
~
H(x,t)
Unpolarized beam, transverse target:
E(x,t)
DsUT~ sinf{k(F2H – F1E)}df
17
Universality of GPDs
Elastic form
factors
Real Compton
scattering at high t
Parton momentum
distributions
Deeply Virtual
Meson production
Deeply Virtual
Compton Scattering
Single Spin
Asymmetries
18
Quark Angular Momentum
→ Access to quark
orbital angular
momentum
19
19
Imaging the Nucleon
Fourier transform of H in momentum transfer t
x < 0.1
x ~ 0.3
x ~ 0.8
gives transverse spatial distribution of quark (parton) with
momentum fraction x
20
DVCS beam asymmetry at 12 GeV CLAS12
sinφ moment of ALU
Experimental DVCS program
E12-06-119 was approved for the
12 GeV upgrade using polarized
beam and polarized targets.
ep
ep
High luminosity and large
acceptance allows wide coverage
in Q2 < 8 GeV2, xB< 0.65, and
t< 1.5GeV2
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SIDIS Electroproduction of Pions
•
Separate Sivers and Collins effects
target angle
hadron angle
q
•
Sivers angle, effect in distribution function:
–
•
e-e’ plane
(fh-fs) = angle of hadron relative to initial quark spin
Collins angle, effect in fragmentation function:
–
(fh+fs) = +(fh-fs’) = angle of hadron relative to final quark spin
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Access TMDs through Semi-Inclusive DIS
ds
2
y2


2
2
dxdydfS dzdfh dPh  xyQ 2(1   )
f1 =
{FUU ,T  ...
cos( 2fh )
UU
h1 =
  cos(2fh )  F
h1L =
 S L [ sin( 2fh )  FULsin( 2fh )  ...]
Transversity
h1T =
 ST [ sin(fh  fS )  FUTsin(fh fS )
Sivers
f 1T =
 sin(fh  fS )  ( FULsin(fh fS )  ...)
h1T
  sin(3fh  fS )  FUTsin( 3fh fS )  ...]
Boer-Mulder
Pretzelosity
=
g1 =
g1T  =
 ...
Unpolarized
Polarized
Target
Polarized
Beam and
cos(fh f S )
2
 ST e [ 1   cos(fh  fS )  FLT
 ...]} Target
 S L e [ 1   2  FLL  ...]
SL, ST: Target Polarization; e: Beam Polarization
23
Access TMDs through Semi-Inclusive DIS
24
Transverse Momentum Dependent Parton Distributions (TMDs)
Nucleon Spin
Quark Spin
Leading Twist
Quark polarization
Un-Polarized
Nucleon Polarization
U
Longitudinally
Polarized
Transversely Polarized
h1 =
f1 =
Boer-Mulder
g1 =
L
h1L =
Helicity
T
h1T =
f 1T =
Transversity
g1T  =
h1T =
Sivers
Pretzelosity
25
A Solenoid Spectrometer for SIDIS
SIDIS SSAs depend on 4 variables (x, Q2, z and PT )
Large angular coverage and precision measurement of
asymmetries in 4-D phase space are essential.
26
SoLID Transversity Projected Data
•
•
Total 1400 bins in x, Q2, PT and z for 11/8.8 GeV beam.
z ranges from 0.3 ~ 0.7, only one z and Q2 bin of 11/8.8 GeV is shown
here. π+ projections are shown, similar to the π- .
27
12 GeV Approved Experiments by Physics Topics
Topic
The Hadron spectra as probes of QCD (rated)
(GluEx and heavy baryon and meson spectroscopy)
The transverse structure of the hadrons (rated)
(Elastic and transition Form Factors)
Hall A
Hall B
Hall C
1
Hall D
Total
1
2
4
2
3
9
The longitudinal structure of the hadrons (rated)
(Unpolarized and polarized parton distribution
functions)
2
2
4
8
The 3D structure of the hadrons (unrated)
(Generalized Parton Distributions and Transverse
Momentum Distributions)
3
8
4
15
1
2
5
8
Hadrons and cold nuclear matter (rated)
(Medium modification of the nucleons, quark
hadronization, N-N correlations, hypernuclear
spectroscopy, few-body experiments)
Low-energy tests of the Standard Model and
Fundamental Symmetries (rated at PAC 37)
2
TOTAL
12
28
15
16
1
3
2
45
12 GeV Approved Experiments by PAC Days
Topic
Hall A
Hall B
Hall C
Hall D
Total
119
0
120
239
144
70
168
382
65
120
118
303
225
891
134
1250
5
100
139
244
The Hadron spectra as probes of QCD (rated)
(GluEx and heavy baryon and meson spectroscopy)
The transverse structure of the hadrons (rated)
(Elastic and transition Form Factors)
The longitudinal structure of the hadrons (rated)
(Unpolarized and polarized parton distribution functions)
The 3D structure of the hadrons (unrated)
(Generalized Parton Distributions and Transverse
Momentum Distributions)
Hadrons and cold nuclear matter (rated)
(Medium modification of the nucleons, quark
hadronization, N-N correlations, hypernuclear
spectroscopy, few-body experiments)
Low-energy tests of the Standard Model and Fundamental
Symmetries (to be rated at PAC 37)
513
TOTAL
952
Days in red are the requested days to be reviewed at PAC38
29
1300
559
79
592
199
3010
Electron Ion Collider
NSAC 2007 Long-Range Plan:
“An Electron-Ion Collider (EIC) with
polarized beams has been embraced by
the U.S. nuclear science community as
embodying the vision for reaching the next
QCD frontier. EIC would provide unique
capabilities for the study of QCD well
beyond those available at existing facilities
worldwide and complementary to those
planned for the next generation of
accelerators in Europe and Asia.”
JLAB Concept
Initial configuration (mEIC):
• 3-11 GeV on 12-60 GeV ep/eA collider
• fully-polarized, longitudinal and transverse
• luminosity: up to few x 1034 e-nucleons cm-2 s-1
Upgradable to higher energies (250 GeV protons)
30
30
EIC Physics Overview
• Hadrons in QCD are relativistic many-body systems, with a fluctuating number of
elementary quark/gluon constituents and a very rich structure of the wave function.
• With 12 GeV we study mostly
the valence quark component,
which can be described with
methods of nuclear physics
(fixed number of particles).
• With an (M)EIC we enter the region where the
many-body nature of hadrons, coupling to
vacuum excitations, etc., become manifest and
the theoretical methods are those of quantum
field theory. An EIC aims to study the sea
quarks, gluons, and scale (Q2) dependence.
mEIC
EIC
12 GeV
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31
Medium Energy EIC@JLab
Three compact rings:
• 3 to 11 GeV electron
• Up to 12 GeV/c proton (warm)
• Up to 60 GeV/c proton (cold)
32
MEIC : Detailed
Layout
warm ring
cold ring
33
EIC Site Plan
34
JLAB EIC Workshops
• Nucleon spin and quark-gluon correlations: Transverse spin, quark and gluon orbital motion,
semi-inclusive processes (Duke U., March 12-13, 2010 )
• 3D mapping of the glue and sea quarks in the nucleon (Rutgers U., March 14-15, 2010)
• 3D tomography of nuclei, quark/gluon propagation and the gluon/sea quark EMC effect
(Argonne National Lab, April 7-9, 2010)
• Electroweak structure of the nucleon and tests of the Standard Model
(College of W&M , May 17-18, 2010)
• EIC Detectors/Instrumentation
(JLab, June 04-05, 2010)
4/5 will produce white paper for publication
35
35
General Emergent Theme
Experimental study of multidimensional
distribution functions that map out the
quark/gluon properties of the nucleon, including:
(quark) flavor
spin and orbital angular momentum
longitudinal momentum
transverse momentum and position
(Challenge to accelerator physics!)
36
36
11 + 60 GeV
3+20 GeV
SIDIS SSA at EIC
37
Huang, Qian, et al
Duke workshop
Imaging at Low x
38
Gluon Saturation
•Gluon density should saturate
(unitarity)
• Access at very high E
• Use large nuclei
39
Phase Diagram of Nuclear Matter
40
MEIC & ELIC: Luminosity Vs. CM Energy
For 1 km
MEIC ring
e + p facilities
e + A facilities
41
Full Acceptance Detector
7 meters
detectors
solenoid
ion dipole w/ detectors
IP
0 mrad
electron FFQs
50 mrad
2+3 m
2m
electrons
2m
Central detector
TOF
Tracking
EM Calorimeter
Hadron Calorimeter
Muon Detector
RICH or DIRC/LTCC
RICH
HTCC
EM Calorimeter
4-5m
Solenoid yoke + Muon Detector
Detect particles with
angles down to 0.5o
before ion FFQs.
Need 1-2 Tm dipole.
Detect particles with
angles below 0.5o
beyond ion FFQs and
in arcs.
Very-forward detector
Large dipole bend @ 20 meter from IP
Solenoid yoke + Hadronic Calorimeter
(to correct the 50 mr ion horizontal crossing angle)
allows for very-small angle detection (<0.3o)
2m
3m
2m
42
EIC Realization Imagined
Activity Name
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025
12 Gev Upgrade
FRIB
EIC Physics Case
NSAC LRP
EIC CD0
EIC Machine
Design/R&D
EIC CD1/Downsel
EIC CD2/CD3
EIC Construction
43
Outlook
• The Jefferson Lab electron accelerator is
currently a unique world-leading facility
for nuclear physics research
• 12 GeV upgrade ensures another decade
of opportunities
• Growing program addressing physics
beyond the standard model
• Nucleon Tomography is a major future
theme
• Large future project on the horizon: EIC
44