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Transcript of 1 Fermilab: Joint Experimental-Theoretical Seminar January 11, 2013 Probing the Quark Sea and...
1
Fermilab: Joint Experimental-Theoretical SeminarJanuary 11, 2013
Probing the Quark Sea and Gluons: the Electron-Ion Collider Project
Rolf Ent (JLab)
2007 Long-Range PlanEIC: “half” recommendation
2010 JLab User Workshops
INT10-3 program>500 page report
EIC white paper – to be published
2
Probing the Quark Sea and Gluons: the Electron-Ion Collider Project
• Electron-Ion Colliders Worldwide
• Electron-Ion Collider Nuclear Science
• Electron-Ion Collider Accelerator Design
• Integrated Detector and Interaction Region
• Electron-Ion Collider Status and Plans
EIC is the generic name for the Nuclear Science-driven Electron-Ion Collider, presently considered in the US
3
Electron Ion Colliders on the World Map
RHIC eRHIC
LHC LHeCCEBAF MEIC
HERA
FAIR ENC
HIAFEIC@China
4
Possible FuturePast
High-Energy Physics Nuclear Physics
Electron Ion Colliders
HERA@DESY LHeC@CERN eRHIC@BNL MEIC@JLab HIAF@CAS ENC@GSI
ECM (GeV) 320 800-1300 45-175 12-140 12 65 14
proton xmin 1 x 10-5 5 x 10-7 3 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 ~40Ca
polarization - - p, 3He p, d, 3He (6Li) p, 3He? p,d
L [cm-2 s-1] 2 x 1031 1033 1033-34 1034-35 1032-33 1035 1032
IP 2 1 2+ 2+ ? 1
Year 1992-2007 2022 (?) 2022 (?) Post-12 GeV 2019 2030 upgrade to FAIR
5
EIC vs LHeCLHeC: L = 1.1x1033 cm-2s-1
Ecm = 1.4 TeV
EIC: L = 1033-1034 cm-2s-1
Ecm = 20-70+ GeV • Add 70-100 GeV electron ring to interact with LHC ion beam• Use LHC-B interaction region• High luminosity mainly due to large g’s (= E/m) of beams
• Variable energy range• Polarized and heavy ion beams• High luminosity in energy region of interest for nuclear science
Nuclear science goals:• Map the spin and spatial structure of quarks and gluons in nucleons• Discover the collective effects of gluons in atomic nuclei• Understand the emergence of hadronic matter from color charge
High-Energy/Nuclear physics goals:• Parton dynamics at the TeV scale - high-Q2 electron-quark scattering
(constrain the size of the quark) - physics beyond the Standard Model - physics of high parton densities (low x)
“world’s first polarized e-p collider and world’s first e-A collider”
high-energy e-p collider to follow on DESY, plus plans for e-A collider
6
eRHIC: take advantage of higher proton/ion energies
Stage I eRHIC @ BNL MEIC / ELIC @ JLab
√s = 15 – 66 GeV
Ee = 3 – 11 GeV
Ep = 20 – 100 GeV
EPb
= up to 40 GeV/A
√s = 25 – 100 GeV
Ee = 3 – 10 GeV
Ep = 50 – 250 GeV
EPb
= up to 100 GeV/A
(MEIC)
MEIC: take advantage of lower proton/ion energies for detector/IR design
Stage I
A High-Luminosity US-Based Electron Ion Collider
“world’s first polarized e-p collider and world’s first e-A collider” Stage 1 MEIC: dedicated ~1 km ring
optimized for 30-100 GeV protons
MEICELIC
(Hall A & C)
CLAS12
eRHIC2
eRHIC1
7
• An EIC aims to study the sea quarks and gluon-dominated matter.
EIC12 GeV
• With 12 GeV we study mostly the valence quark component
MEIC
Into the “sea”: the EIC
8
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
The proton is far more than just its up + up + down (valence) quark structure
Nuclear physicists are trying to answer how basic properties like mass, shape, and spin come about from the flood of gluons, quark/anti-quark pairs, and a few ever-present quarks.
& gluons are abundant
9
QCD and the Origin of Mass
99% of the proton’s mass/energy is due to the self-generating gluon field
– Higgs mechanism has no role here.
The similarity of mass between the proton and neutron arises from the fact that the gluon dynamics are the same
– Quarks contribute almost nothing.
M(up) + M(up) + M(down) ~ 10 MeV << M(proton)
10
The Physics Program of an EICI) Map the spin and spatial structure of quarks and gluons in nucleons
Sea quark and gluon polarizationTransverse spatial distributionsOrbital motion of quarks/gluonsParton correlations: beyond one-body densities
(show the nucleon structure picture of the day…)
II) Discover the collective effects of gluons in atomic nucleiColor transparency: Small-size configurationsNuclear gluons: EMC effect, shadowingStrong color fields: Unitarity limit, saturationFluctuations: Diffraction
(without gluons there are no protons, no neutrons, no atomic nuclei)
III) Understand the emergence of hadronic matter from color chargeMaterialization of color: Fragmentation, hadron breakup, color correlationsParton propagation in matter: Radiation, energy loss
(how does M = E/c2 work to create pions and nucleons?)
Needs high luminosity and range of energies
+ some developing ideas for fundamental symmetry tests
11
5 x 250 starts here
5 x 100 starts here
current data
w/ EIC data
Q2 = 10 GeV2Helicity PDFs at an EIC
12
Sea Quark Polarization• Spin-Flavor Decomposition of the Light Quark Sea
| p = + + + …>u
u
d
u
u
u
u
d
u
u
dd
d Many models predict
Du > 0, Dd < 0
Needs intermediate √s ~ 30 (and good luminosity)}
13
Wpu(x,k
T,r) Wigner distributions
d2kT
PDFs f1
u(x), .. h1u(x)
d3r
TMD PDFs f1
u(x,kT), .. h1u(x,kT)
3D imaging
6D Dist.
Form FactorsGE(Q2), GM(Q2)
d2rT
dx &Fourier Transformation
1D
Unified View of Nucleon Structure
GPDs/IPDs
d2kT drz
14
TMDs2+1 D picture in momentum space
GPDs2+1 D picture in impact-parameter space
Towards Imaging - Two Approaches
• intrinsic transverse motion
• spin-orbit correlations = indicator of OAM
• non-trivial factorization
• accessible in SIDIS, DY
• collinear but long. momentum transfer
• indicator of OAM; access to Ji’s total Jq,g
• existing factorization proofs
• DVCS, deep exclusive meson production
Quark Sivers function fit to SIDIS (Anselmino et al. 2009)
k y
kx
-0.5
0.5
0.0
-0.5 0.0 0.5
(Lattice Calculation of the IP density of up quark, QCDSF/UKQCD Coll., 2006)
bx [fm]
15
Transverse Quark & Gluon ImagingDeep exclusive measurements in ep/eA with an EIC:
diffractive: transverse gluon imaging J/y, f, ro, g (DVCS) non-diffractive: quark spin/flavor structure p, K, r+, …
Describe correlation of longitudinal momentum and transverse position of quarks/gluons
Transverse quark/gluon imaging of nucleon(“tomography”)
Are gluons uniformly distributed in nuclear matter or are there small clumps of glue?Are gluons & various quark flavors similarly distributed? (some hints to the contrary)
16
Detailed differential images from nucleon’s partonic structure
EIC: Gluon size from J/Y and f electroproduction (Q2 > 10 GeV2)
[Transverse distribution derived directly from t dependence]
t
Hints from HERA:Area (q + q) > Area (g)
Dynamical models predict difference: pion cloud, constituent quark picture
-
t
EIC: singlet quark size from deeply virtual compton scattering
EIC: strange and non-strange (sea) quark size from p and K production
• Q2 > 10 GeV2 for factorization • Statistics hungry at high Q2!
17
Example: Transverse Spatial Distribution of Gluons from J/Y
DVCS transverse spatial projections in progress
18
Image the Transverse Momentum of the Quarks
The difference between the p+, p–, and K+ asymmetries reveals that quarks and anti-quarks of different flavor are orbiting in different ways within the proton.
Swing to the left, swing to the right: A surprise of transverse-spin experiments
dsh ~ Seq2q(x) dsf Df
h(z)
Sivers distribution
19
Image the Transverse Momentum of the Quarks
Only a small subset of the (x,Q2) landscape has been mapped here:
terra incognitaGray band: present
“knowledge”Purple band: EIC (2s)
u u
An EIC with good luminosity & high
transverse polarization is the optimal tool to to
study this!
20
Gluons in Nuclei
NOTHING!!!
What do we know about gluons in a nucleus?
Ratio of gluons in lead to deuterium
• EIC: access gluons through FL (needs variable energy) and dF2/dln(Q2)
• Knowledge of gluon PDF essential for quantitative studies of onset of saturation
21
Tomography: Hard Diffraction
A 7 TeV equivalent electron bombarding the proton … but nothing happens to the proton in 15% of cases
Diffractive event
No activity in proton direction
Predictions for eA for such hard diffractive events range up to: ~30-40%... given saturation models
22
Hadronization – parton propagation in matter
EIC: Understand the conversion of color charge to hadrons through fragmentation and breakup
Le
e’g*
p+
pT
DpT2 = pT
2(A) – pT2(2H)
“pT Broadening”
Dp T
2
Comprehensive studies possible:• wide range of energy v = 10-1000 GeV move hadronization inside/outside nucleus, distinguish energy loss and attenuation• wide range of Q2: QCD evolution of fragmentation functions and medium effects• Hadronization of charm, bottom Clean probes with definite QCD predictions• High luminosity Multi-dimensional binning and correlations• √s > 30: jets and their substructure in eA
Accardi, Dupre
Can we learn more from correlating with the target fragmentation region?
23
C. Weiss
s
• For large or small y, uncertainties in kinematic variables become large
Range in y
Range in s
Range of kinematics
• Detecting the electron ymax
/ ymin
~ 10• Also detecting hadrons y
max / y
min ~ 100
– Requires hermetic detector (no holes)
• Accelerator considerations limit smin
– Depends on smax
(dynamic range)
• At fixed s, changing the ratio Ee / E
ion
can for some reactions improve resolution, particle identification (PID), and acceptance
C. WeissC. Weiss
valence quarks/gluons
non-pert. sea quarks/gluons
radiative gluons/sea
s
To cover the physics we need…
Vacuum fluct.
pQCD radiation
x = Q2/ys
Range of nuclei
24
A High-Luminosity US-Based 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.”
Base EIC Requirements per Executive Summary of Institute for Nuclear Theory Report:• range in energies from √s ~ 20 to √s ~ 70 & variable• fully-polarized (>70%), longitudinal and transverse• ion species from deuterium to A = 200 or so• high luminosity: about 1034 e-nucleons cm-2 s-1
• multiple interaction regions• upgradable to higher energies (√s ~ 150 GeV)
“world’s first polarized
e-p collider and world’s
first e-A collid
er”
25
How MEIC meets the Design Specs
Base EIC Requirements per Executive Summary INT Report:• center of mass energies from √s ~ 20 to √s ~ 70 GeV & variable
- electron energies above 3 GeV to allow efficient electron trigger- proton energy adjustable to optimize particle identification
• highly polarized (>70%) electron and nucleon beams- longitudinally polarized electron and nucleon beams- transversely polarized nucleon beams
• ion species from deuterium to A = 200 or so• high luminosity ~1034 e-nucleons cm-2 s-1
- optimal luminosity in √s ~ 30-50 region- luminosity ≥1033 e-nucleons cm-2 s-1 in √s ~ 20-70 region
• multiple interaction regions• integrated detector/interaction region
- non-zero crossing angle of colliding beams- crossing in ion beam to prevent synchrotron background
- ion beam final focus quads at ~7 m to allow for full acceptance detector space- bore of ion beam final focus quads sufficient to let particles pass through
up to t ~ 2 GeV2 (t ~ Ep2Q2)
• upgradeable to center of mass energy of about √150 GeV
25
26
MEIC (= stage-I EIC @ JLab) Design• Collider is based on a figure eight concept
– Avoids crossing polarization resonances• Improves polarization for all species• Makes polarized deuterons possible
– Advantage of having a new ion ring
• Highest luminosity comes with final focus quadrupoles close together – Interferes with detection of (spectator) particles at small angles– MEIC is designed around a full-acceptance
detector with ±7 meters free space around
the interaction point and a high-luminosity
detector with ±4.5 meters free space
• The present MEIC design takes a conservative technical approach by limiting
several key design parameters within state-of-the-art. It relies on regular
electron cooling to obtain the ion beam properties.
• The present JLab EIC design focuses on a
CM energy range from 12 up to 65 GeV
Emphasis on integrated detector/interaction region
27
EIC@JLab (MEIC) Technical Design Strategy
Limit as many design parameters as we can to within or close to the present state-of-art in order to minimize technical uncertainty and R&D tasks
– Stored electron current should not be larger than 3 A– Stored proton/ion current should be less than 1 A (better below 0.5 A)– Maximum synchrotron radiation power density is 20 kW/m
– Maximum peak field of warm electron magnet is 1.7 T– Maximum peak field of ion superconducting dipole magnet is 6 T
– Maximum betatron value at FF quad is 2.5 km
• New beta-star, appropriate to the detector requirements
2.5 km βmax + 7 m βy*= 2 cm Full acceptance
2.5 km βmax + 4.5 m βy*=0.8 cm Large acceptance
• This design will form a base for future optimization guided by – Evolution of the science program – Technology innovation and R&D advances
28
Medium Energy EIC@JLab
JLab Concept
Initial configuration (LEIC & MEIC):• 3-11 GeV on 10-25 & 20-100 GeV ep/eA collider• fully-polarized, longitudinal and transverse• luminosity: up to ~2 x 1034 e-nucleons cm-2 s-1
Upgradable to higher energies (EIC)• 3-11 GeV on up to 250 GeV ep/eA collider• luminosity: up to few x 1034 e-nucleons cm-2 s-1
Electron collider ring
(3 to 11 GeV)
Cold ion collider ring
(up to 100 GeV)
Warm ion collider ring (up to 25 GeV)
“Like Mike”
“Ike”
29
MEIC Design Report
• Posted: arXiv:1209.0757
• Stable concept for 3 yearsDesign Feature: High & Flexible PolarizationFully integrated detector/interaction region
“… was impressed by the outstanding quality of the present MEIC design”“The report is an excellent integrated discussion of all aspects of the MEIC concept.” (JSA Science Council 08//29/12)
• EPJA article by JLab theory on EIC science case• EIC white paper near-final (w. BNL & JLab users)
30
Design Features: High Polarization
All ion rings (two boosters, collider) have a figure-8 shape • Spin precessions in the left & right parts of the ring are exactly cancelled• Net spin precession (spin tune) is zero, thus energy independent
• Ensures spin preservation and ease of spin manipulation • Avoids energy-dependent spin sensitivity for ion all species• The only practical way to accommodate medium energy polarized deuterons
This design feature promises a high polarization for all light ion beams
(The electron ring has a similar shape since it shares a tunnel with the ion ring, section 4.7)
Use Siberian Snakes/solenoids to arrange polarization at IPs
IIP
IP
longitudinal axis
IIP
IP
Vertical axis
IP
IIP
Solenoid
IP
IIP
Insertion
Longitudinal polarization at both IPs
Transverse polarization at both IPs
Longitudinal polarization at one IP
Transverse polarization at one IP
Proton or Helium-3 beams Deuteron beam
Slide 30
31
Design Features: High Luminosity
• Based on high bunch repetition rate CW colliding beams• Very high bunch repetition rate Very small bunch charge
• Very short bunch length (sz ~ b*) Very small β*
• Crab crossing Small transverse emittance
• A proven concept: KEK-B @ 2x1034 /cm2/s
• JLab aims to replicate this in colliders w/ hadron beams• The electron beam from CEBAF possesses a high bunch repetition rate • Ion beams from a new ion complex to match the electron beam
KEK-B MEIC
Repetition rate MHz 509 748.5
Particles per bunch (e-/e+) or (p/e-) 1010 3.3 / 1.4 0.42 / 2.5
Beam current A 1.2 / 1.8 0.5 / 3
Bunch length cm 0.6 1 / 0.75
Horizontal & vertical β* cm 56 / 0.56 10/2 to 4/0.8
Beam energy (e-/e+) or (p/e-) GeV 8 / 3.5 60 / 5
Luminosity per IP, 1034 cm-2s-1 2 0.56 ~ 1.4
• •
•
Slide 31
32
A New Ion Complex at JLab
Length (m)
Max. energy (GeV/n)
Electron Cooling Process
Proton Lead
SRF linac ~100 0.285 0.1 Stripping
Pre-booster ~300 3 1.2 DC accumulation
Large booster ~1350 25 10 Stacking
collider ring~1350 100 40 ERL
De-bunching/re-bunching
ion sources
SRF Linacpre-booster
(accumulator ring)large booster medium energy
collider ring
to high energy collider ring
coolingcooling
Slide 32
Ion Linac (by ANL)MEBT
QWR
QWR HWR
DSR
Ion Sources
IHRFQ
Stripper
SuperconductingNormal conducting
ARC 1
Injection Insertion section
ARC 2
ARC 3
RF Cavities
Electron Cooling
Solenoids
Extraction to
large booster
Collimation
Beam from LINAC
Pre-booster (by NIU)
33
MEIC Layout
• Vertical stacking for identical ring circumferences• Horizontal crab crossing at IPs due to flat colliding beams• Ion beams execute vertical excursion to the plane of the
electron orbit for enabling a horizontal crossing
• Ring circumference: 1340 m• Maximum ring separation: 4 m• Figure-8 crossing angle: 60 deg.
Interaction point locations:
• Downstream ends of the electron straight sections to reduce synchrotron radiation background
• Upstream ends of the ion straight sections to reduce residual gas scattering background
Electron Collider
Ion Collider
Large Ion Booster
Interaction Regions
PreboosterIon
source
Three Figure-8rings stacked
vertically
Ion transfer beam line
Medium energy IP withhorizontal crab
crossing
Electron ring
Injector
12 GeV CEBAF
SRF linac
Warm large booster
(up to 25 GeV/c)
Cold 97 GeV/c proton collider
ring
Electron path
Ion path
34
Crab Crossing• High bunch repetition rate requires crab crossing of colliding beams to avoid parasitic beam-
beam collisions• Present baseline: 50 mrad crab crossing angle
Crab Cavity
Energy (GeV/c)
Kicking Voltage (MV)
R&D
electron 5 1.35 State-of-art
proton 60 8 Factor of six
Crab cavity State-of-the-art: KEKB Squashed cell@TM110 Mode Vkick=1.4 MV, Esp= 21 MV/m 750 MHz SRF crab cavity design ongoing
35
Crab Crossing• Restore effective head-on bunch collisions with 50 mrad crossing angle Preserve luminosity• Dispersive crabbing (regular accelerating / bunching cavities in dispersive region) vs.
Deflection crabbing (novel TEM-type SRF cavity at ODU/JLab, very promising!)
Incoming At IP Outgoing
36
Electron Cooling
• Essential to achieve high luminosity for MEIC
• Traditional electron cooling, not Coherent Electron Cooling
• MEIC cooling schemePre-booster: Cooling for assisting accumulation of positive ion beams
(Using a low energy DC electron beam, existing technology)
Collider ring: Initial cooling after injection Final cooling after boost & re-bunching, for reaching design values Continuous cooling during collision for suppressing IBS
(Using new technologies)
• Challenges in cooling at MEIC collider ring – High ion energy
(State-of-the-art: Fermilab recycler, 8 GeV anti-proton, DC e-beam)
– High current, high bunch repetition rate CW cooling electron beam
Slide 36
37
Staged Electron Cooling In Collider Ring
Initial Cooling after boost & bunching
Colliding Mode
Energy GeV/MeV 20 / 8.15 60 / 32.67 60 / 32.67
Beam current A 0.5 / 3 0.5 / 3 0.5 / 3
Particles/Bunch 1010 0.42 / 3.75 0.42 / 3.75 0.42 / 3.75
Ion and electron bunch length cm (coasted) 1 / 2~3 1 / 2~3
Momentum spread 10-4 10 / 2 5 / 2 3 / 2
Horiz. and vert. emitt, norm. µm 4 / 4 0.35 / 0.07
Laslett’s tune shift (proton) 0.002 0.006 0.07
Cooling length /circumference m/m 15 / 1000 15 / 1000 15 / 1000
• Initial cooling: after injection for reduction of longitudinal emittance < acceleration
• Final cooling: after boost & rebunching, for reaching design values of beam parameters
• Continuous cooling: during collision for suppressing IBS & preserving luminosity lifetime
38
ERL Circulator Electron Cooler
ion bunch
electron bunch
circulator ring
Cooling section
solenoid
Fast kickerFast kicker
SRF Linac dumpinjector
e-bunches circulates 10 -100 times reduction of current from an ERL by a same factor
Design Choices• Energy Recovery Linac (ERL) • Compact circulator ring
to meet design challenges• Large RF power (up to 81 MW) • Long gun lifetime (average current 1.5 A)
Required technologies• High bunch charge magnetized gun• High current ERL (55 MeV, 15 to150 mA)• Ultra fast kicker
energy recovery
30 m
Solenoid (20 m)
SRF
injector
dumper
Optimization• eliminating a long return path could double the cooling rate Proposal: A technology demonstration
using JLab FEL facility
Slide 38
39
MEIC Collider Ring Footprint
m
Quarter arc 140
Universal spin rotator
50
IR insertion 125
Figure-8 straight 140 x 2
RF short straight 25
Circumference ~ 1300
Ring design is a balance between • Synchrotron radiation prefers a large ring (arc) length• Ion space charge prefers a small ring circumference
Multiple IPs require long straight sections
Straights also hold required service components (cooling, injection and ejection, etc.)
3 rd IR (125 m)
UniversalSpin Rotator
(8.8°/4.4°, 50 m)
1/4 Electron Arc
(106.8°, 140 m)
Figure-8 Crossing Angle: 2x30°
Experimental Hall (radius 15 m)
RF (25 m)
Universal
Spin Rotator
(8.8°/4.4°, 5
0 m)
Universal
Spin Rotator
(8.8°/4.4°, 5
0 m)
UniversalSpin Rotator
(8.8°/4.4°, 50 m)
IR (125 m) IR (125 m)
Injection from CEBAF
Compton Polarimeter
(28 m)
1/4 Electron Arc
(106.8°, 140 m)
40
MEIC assumptions
(x,Q2) phase space directly correlated with s (=4EeEp) :
@ Q2 = 1 lowest x scales like s-1
@ Q2 = 10 lowest x scales as 10s-1
(“Medium-Energy”) MEIC@JLab option driven by:access to sea quarks (x > 0.01 (0.001?) or so)deep exclusive scattering at Q2 > 10 (?)any QCD machine needs range in Q2
s = few 100 - 1000 seems right ballpark s = few 1000 allows access to gluons, shadowing
Requirements for deep exclusive and high-Q2 semi-inclusive reactions also drives request for (lower &) more symmetric beam energies.Requirements for very-forward angle detection folded in IR design
x = Q2/ys
C. Weiss
s
C. Weiss
s
• Detecting only the electron ymax
/ ymin
~ 10
• Also detecting all hadrons ymax
/ ymin
~ 100
41
Where do particles go - generalp or A e
Several processes in e-p:1) “DIS” (electron-quark scattering) e + p e’ + X2) “Semi-Inclusive DIS (SIDIS)” e + p e’ + meson + X3) “Deep Exclusive Scattering (DES)” e + p e’ + photon/meson + baryon4) Diffractive Scattering e + p e’ + p + X5) Target fragmentation e + p e’ + many mesons + baryons
Even more processes in e-A:6) “DIS” e + A e’ + X7) “SIDIS” e + A e’ + meson + X8) “Coherent DES” e + A e’ + photon/meson + nucleus9) Diffractive Scattering e + A e’ + A + X10)Target fragmentation e + A e’ + many mesons + baryons11)Evaporation processes e + A e’ + A’ + neutrons
In general, e-p and even more e-A colliders have a large fraction of their science related to the detection of what happens to the ion beams. The struck quark remnants can be guided to go to the central detector region with Q2 cuts, but the spectator quark or struck nucleus remnants will go in the forward (ion) direction.
Token example: 1H(e,e’π+)n
42
Transverse spatial imaging – recoil baryons
DVCS on the proton
J.H. Lee
~ √t/Ep
5x30 GeV5x250 GeV
ep → e'π +n
8 mrad @ t = -1
40 mrad @ t = -1 GeV2
T. Horn
• Colliders allow straightforward detection of recoil baryons, making it possible to map the t-distribution down to very low values of –t
– eRHIC (partially) solves this by squeezing the high-energy recoil baryons through a high-gradient interaction region focusing magnet and the use of Roman Pots
• At very high proton energies, recoil baryons are all scattered at small angles– Moderate proton energies give the best resolution
– High luminosity at intermediate proton energies and excellent small-angle detection make the MEIC a perfect tool for imaging of the proton
43
Detector/IR in pocket formulas
• bmax ~ 2 km = l2/b* (l = distance IP to 1st quad)
• IP divergence angle ~ 1/sqrt(b*)
• Luminosity ~ 1/b*
Example: l = 7 m, b* = 20 mm bmax = 2.5 km
Example: l = 7 m, b* = 20 mm angle ~ 0.3 mrExample: 12 s beam-stay-clear area
12 x 0.3 mr = 3.6 mr ~ 0.2o
Making b* too small complicates small-angle (~0.5o) detection before ion Final Focusing Quads, and would require too high a peak field for these quads given the large apertures (up to ~0.5o). b* = 1-2 cm and Ep = 20-100 GeV ballpark right!
• FFQ gradient ~ Ep,max /sqrt(b*) (for fixed bmax, magnet length)
Example: 6.8 kG/cm for Q3 @ 12 m @ 60 GeV 7 T field for 10 cm (~0.5o) aperture
44
MEIC: Full acceptance detector – strategy
ultra forwardhadron detectionlow-Q2
electron detection large apertureelectron quads
small diameterelectron quads
central detector with endcaps
ion quads
50 mrad beam(crab) crossing angle
n
ep
p
small anglehadron detection
60 mrad bend
solenoid
electron FFQs50 mrad
0 mrad
ion dipole w/ detectors
ions
electrons
IP
ion FFQs
2+3 m 2 m 2 m
detectors
Central detector
7 meters
Three-stage detection
In general, e-p and even more e-A colliders have a large fraction of their science related to the detection of what happens to the ion beams… spectator quark or struck nucleus remnants will go in the forward (ion) direction this drives the integrated detector/interaction region design: NO HOLES!
(P. Nadel-Turonski, V. Morozov, T. Horn, C. Hyde)
45
solenoid
electron FFQs50 mrad
0 mrad
ion dipole w/ detectors
ions
electrons
IP
ion FFQs
2+3 m 2 m 2 m
Detect particles with angles below 0.5o beyond ion FFQs and in arcs.Need 4 m machine element free region
detectors
Central detector
Detect particles with angles down to 0.5o before ion FFQs.Need 1-2 Tm dipole
EM
Ca
lorim
ete
r
Ha
dro
n C
alo
rime
ter
Mu
on
De
tect
or
EM
Ca
lorim
ete
r
Solenoid yoke + Muon Detector
TOF
HT
CC
RIC
H
RICH or DIRC/LTCC
Tracking
2m 3m 2m
4-5m
Solenoid yoke + Hadronic Calorimeter
Very-forward detectorLarge dipole bend @ 20 meter from IP (to correct 50 mr ion horizontal crossing angle) allows for very-small angle detection (<0.3o).Need 20 m machine element free region
MEIC: Full Acceptance Detector
7 meters
Three-stage detection
All incorporated in MEIC design
(P. Nadel-Turonski, V. Morozov, T. Horn, C. Hyde)
4646
e
p
n20 Tm dipole
2 Tm dipole
solenoid
• 100 GeV maximum ion energy allows using large-aperture magnets with achievable field strengths
• Momentum resolution < 3x10-4
– limited by intrinsic beam momentum spread
• Excellent acceptance for all ion fragments
• Neutron detection in a 25 mrad cone down to zero degrees
• Recoil baryon acceptance:– up to 99.5% of beam energy for all angles
– down to 2-3 mrad for all momenta
npe
MEIC Detector & Interaction RegionGEANT4 model of extended IR exists
Full acceptance
47
Extended Detector & Interaction Region
Truly fully integrated detector & interaction region, also for eA
48
Design Feature: Full-Acceptance Detector
6 T max
9 T max
12 T max
Forward acceptance horizontal plane
Forward acceptance vertical plane
Full acceptance detector• Demonstrated excellent acceptance & resolution• Completed the detector-optimized IR optics
• Fully integrated detector and interaction region
• Working on hardware engineering design
Addressing accelerator challenges• Demonstrated chromaticity compensation (section 7.5)
49
Reviews and Activities
Slide 49
• 2nd EIC International Advisory Committee Review (Nov. 2-3, 2009) (Accelerator members: R. Gerig, U. Wienands)
• Physics-Machine Joint Meeting (for a design goal) (Feb. 11&12, 2010)
• MEIC Machine Design Week (March 4-8, 2010) (Detector/IR consultant: M. Sullivan of SLAC )
• MEIC Internal Machine Design Review (Sept. 15-16, 2010) (Reviewers: A. Chao and G. Hoffstaetter)
• RF & Beam Synchronization Mini-Workshop (Oct. 29, 2010)
• MEIC Ion Complex Design Workshop (Jan. 27-28, 2011)
• 3rd ElC International Advisory Committee Review (April 9, 2011) (Accelerator members: R. Gerig, S. Nagaitsev, V. Shiltsev)
• MEIC Detector and IR Design Mini-Workshop (Oct. 31, 2011)
• ERL Circulator Cooler Test Facility Retreat (Jan. 31, 2012)
50
EIC Progress• Close and frequent collaboration between accelerator and nuclear physicists regarding the machine, interaction region and detector requirements has taken place.
“We are proud to announce that we have achieved a fully integrated detector and interaction region”
• Several JLab user proposals for generic detector R&D call
• Draft MEIC Intermediate Design Report completed Aug. 2012
• Concept for regular electron cooling further worked out- Many aspects of cooling can be tested at JLab/FEL- Mainly use “brute force” lenient at lower energies
• Cost Estimate developed, estimate being iterated(3 main cost drivers: Ion Linac, SC Magnets & SRF Cooling, Civil construction)
• Steering committee with many JLab users working on EIC white paper accessible to general nuclear science community
• Integrate LEIC (up to 25 GeV/c protons) into design
51
MEIC
warm e-ring
warm p-ring
cold p-ring
warm e-ring
cold p-ring
EIC
(LEIC)25 GeV 100 GeV 250 GeV
MEIC = MEIC + LEIC has large advantages:1) Design flexibility2) Ease of commissioning3) Separate warm ion ring
from cold ion ring4) Reduce risk
Integrate LEIC into MEIC planning
cooling
52
LEIC as An Intermediate Technology StepLEIC minimizes technology challenges, and provides a test bed for MEIC• Electron cooling
– Requires lower electron energies (13.6 MeV vs. 4.3 MeV Fermilab cooler) and a lower (~0.5 A) current electron cooling beam
• Ion linac/pre-booster– An accumulation of a lower current ion beam in the pre-booster
• Beam synchronization – Variation of number of bunches in the LEIC ion collider ring provides a large set of
synchronization energies for experiments – Variation of the warm LEIC ion ring path-length for covering other energies is technically
feasible, RF frequency variation can be avoided • Crab cavity
– The integrated kicking voltage is reduced by a factor of 4, now about 3 times of KEK-B
• Chromaticity– Start with only one IR, the chromaticity is reduced by half.
• IR magnets– The maximum fields are reduced by a factor of 4.
• Ion polarization– Magnetic field of some spin rotators are reduced by a factor of 4.
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MEIC 2013 Plans/Goals
• By Spring 2013:• Finalize First Optimization:
- Copy main IR into 2nd IR and do dynamical aperture studies- Shorten electron spin rotator & reshuffle to allow LEIC to 25+ GeV
• Fold in Detector solenoid in accelerator design- optics requirements and initial return field optimization- ion beam deflection & optics compensation- polarization impact
• By Summer 2013:• Completing:
- Electron cooling channels in both warm and cold ion collider rings- Vertical chicane for separating two cooling beams- Ion vertical chicanes to electron ring plane
• Ramp up detector studies: resolution, fast MC• First concepts/checks of all magnets• Cartoon drawings of full MEIC
• Workshop adjacent to APS/DNP meeting October 2013• By end of 2013:
• Polarization tracking study with misalignments, etc.• Initial results of resolution & fast MC studies• Supplement to MEIC design report to outline the completed integration of machine
design and science capabilities utilizing protons/ions from the warm magnet ring
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Dechirper Rechirper
MEIC Planned Accelerator R&D• Electron Cooling
– Proof of staged beam cooling concept– Design of an ERL Circulator cooler– Cooler test facility proposal
• Interaction Region Design– Detector/IR integration, small angle
(down to 0°) particle detection– Nonlinear beam dynamics, chromatic
compensation and dynamic aperture– Implementation of crab crossing
• Polarization– Electron spin matching– Proof of figure-8 ring concept– Realization of fast spin flip
• Beam-beam effect• Electron cloud effect in ion ring
Solenoid (15 m
)
SRF
injector
dumper
MEIC Electron cooler
e-Cooler Test Facility
Interaction Region w/ Forward tagging
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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
Assumes endorsement for an EIC at the next NSAC Long Range Plan (2013/14?)
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New MEIC/EIC Layout
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Summary
• Collider environment provides tremendous advantages – Kinematic coverage (high center-of-mass energy)
– Polarization measurements with excellent Figure-of-Merit
– Detection of spectators, recoil baryons, and target fragmentation
• EIC is a maturing project– MEIC design report on arXiv, and elegant plans to integrate LEIC-MEIC:
Everybody wants to be “Like Mike”
– Accelerator R&D funds allocated, and joint detector R&D projects have started
• EIC is the ultimate tool to study sea quarks and gluons– Sea quarks and gluons play a prominent role in nucleon structure
– EIC is required to completely understand nucleon structure and the role of gluons in nuclei
• We have a unique opportunity to make a breakthrough in nucleon structure and QCD dynamics:
- explore and image the nucleon- discover the role of gluons in structure and dynamics- understand the emergence of hadrons from color charge
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59
longitudinal momentum
transverse distribution
orbital motion
quark to hadron
conversion
Dynamical structure! Gluon saturation?
• Obtain detailed differential transverse quark and gluon images (derived directly from the t dependence with good t resolution!)
- Gluon size from J/Y and f electroproduction- Singlet quark size from deeply virtual compton scattering (DVCS)- Strange and non-strange (sea) quark size from p and K production
• Determine the spin-flavor decomposition of the light-quark sea• Constrain the orbital motions of quarks & anti-quarks of different flavor
- The difference between p+, p–, and K+ asymmetries reveals the orbits• Map both the gluon momentum distributions of nuclei (F2 & FL measurements) and the transverse spatial distributions of gluons on nuclei (coherent DVCS & J/Y production).• At high gluon density, the recombination of gluons should compete with gluon splitting, rendering gluon saturation. Can we reach such state of saturation?• Explore the interaction of color charges with matter and understand the conversion of quarks and gluons to hadrons through fragmentation and breakup.
Why a New-Generation EIC? Why not HERA?
60
A CB
D Continuous Electron Beam• Energy 0.4 ─ 6.0 GeV• 200 mA, polarization 85%• 3 x 499 MHz operation• Simultaneous delivery 3 halls
JLab accelerator CEBAF
• 416 PhDs completed• On average 22 US PhDs per year, close to 30% of US PhDs in nuclear physics• On average 50 undergrads per year involved in research at Jefferson Lab• 1385 users in FY12, anticipated to grow to ~1500+ users with 12-GeV operations• International: non-US nuclear physics users = 1/3 of total, from 33 countries
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12 GeV Upgrade Project: $310M, ~80% obligated
Scope of the project includes: • Doubling the accelerator beam energy• New experimental Hall and beamline• Upgrades to existing Experimental Halls
Maintain capability to deliver lower pass beam energies: 2.2, 4.4, 6.6….
New Hall
Add arc
Enhanced capabilitiesin existing Halls
Add 5 cryomodules
Add 5 cryomodules
20 cryomodules
20 cryomodules
Upgrade arc magnets and supplies
CHL upgrade
Upgrade is designed to build on existing facility: vast majority of accelerator and experimental equipment have continued use
The completion of the 12 GeV Upgrade of CEBAF was ranked the highest priority in the 2007 NSAC Long Range Plan.
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21st Century Science Questions
• What is the role of gluonic excitations in the spectroscopy of light mesons?
• Where is the missing spin in the nucleon?What is the role of orbital angular momentum?
• Can we reveal a novel landscape of nucleon substructure through measurements of new multidimensional distribution functions?
• What is the relation of short-range nuclear structure and parton dynamics?
• Can we discover evidence for physicsbeyond the standard modelof particle physics?
Excited Glue
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The road to orbital motion
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.
Pt = pt + z kt + O(kt
2/Q2)
SIDIS – kT Dependence
p
M
xTMD
TMDu(x,kT)
f1,g1,f1T ,g1T
h1, h1T ,h1L ,h1
Linked to framework of Transverse Momentum Dependent Parton Distributions
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Wu(x,k,r)Towards a “3D” spin-
flavor landscape (Wigner Function)
t
EIC: Transverse spatial distribution derived directly from t dependence:
• Gluon size from J/Y and f• Singlet quark size from g• Strange and non-strange (sea)
quark size from p and K production
Hints from HERA: Area (q + q) > Area (g)
(x,r)(x,k)
p
m
xTMD
EIC: Transverse momentum distribution derived directly from semi-inclusive measurements, plus large gain in our knowledge of transverse momentum effects as function of x.
Exact kT distribution presently unknown – EIC can do this well
-
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Parameters for Full Acceptance Interaction Point
Proton Electron
Beam energy GeV 60 5
Collision frequency MHz 750 750
Particles per bunch 1010 0.416 2.5
Beam Current A 0.5 3
Polarization % > 70 ~ 80
Energy spread 10-4 ~ 3 7.1
RMS bunch length mm 10 7.5
Horizontal emittance, normalized µm rad 0.35 54
Vertical emittance, normalized µm rad 0.07 11
Horizontal β* cm 10 10
Vertical β* cm 2 2
Vertical beam-beam tune shift 0.014 0.03
Laslett tune shift 0.06 Very small
Distance from IP to 1st FF quad m 7 3.5
Luminosity per IP, 1033 cm-2s-1 5.6
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Parameters for High Luminosity Interaction Point
Proton Electron
Beam energy GeV 60 5
Collision frequency MHz 750 750
Particles per bunch 1010 0.416 2.5
Beam Current A 0.5 3
Polarization % > 70 ~ 80
Energy spread 10-4 ~ 3 7.1
RMS bunch length mm 10 7.5
Horizontal emittance, normalized µm rad 0.35 54
Vertical emittance, normalized µm rad 0.07 11
Horizontal β* cm 4 4
Vertical β* cm 0.8 0.8
Vertical beam-beam tune shift 0.014 0.03
Laslett tune shift 0.06 Very small
Distance from IP to 1st FF quad m 4.5 3.5
Luminosity per IP, 1033 cm-2s-1 14.2
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Chromaticity and Dynamic Aperture• Compensation of chromaticity with 2 sextupole families only using symmetry
• Non-linear dynamic aperture optimization under way
p/p = 0.310-3 at 60 GeV/c
5 p/p
Ions
p/p = 0.710-3 at 5 GeV/c
5 p/p
Electrons
Normalized Dynamic Aperture
𝑥 /𝜎 𝑥
𝑦/𝜎
𝑦
w/o Octupole
with Octupole
𝑥/𝜎
𝑥
𝛿 /𝜎 𝛿
68
-10000
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000
10000
-20000 -15000 -10000 -5000 0 5000 10000 15000 20000x [cm]
z [cm]
Figure-8 Collider Ring - Footprint
Use Crab Crossing for Very-Forward Detection too!
Present thinking: ion beam has 50 mr horizontal crossing angleRenders good advantages for very-forward particle detection
~60 mr bend would need 12 Tm dipole @ ~20 m from IP
(Reminder: MEIC/ELIC scheme uses 50 mr crab crossing)
69
Pion momentum = 5 GeV/c, 4T ideal solenoid field, 1.25 m tracking region
Detector/IR – Magnetic Fields
Add <2 Tm transverse field component in forward-ion direction to get dp/p roughly constant vs. angle
• Goal: resolution dp/p (for pions) better than 1% for p < 10 GeV/c• obtain effective 0.5 Tm field by having 50 mr crossing angle (for 5 m long central solenoid)• probably suffices to add 1-2 Tm dipole field for small-angles (<10o?) only to get dp/p < 1% for pions of up to 10 GeV/c.
Here we added dipole for angles smaller than 25o
70
• From arc where electrons exit and magnets on straight section
Synchrotron radiation
Random hadronic background
• Dominated by interaction of beam ions with residual gas in beam pipe between arc and IP
• Comparison of MEIC (at s = 4,000) and HERA (at s = 100,000)− Distance from ion exit arc to detector: 50 m / 120 m = 0.4
− Average hadron multiplicity: (4000 / 100000)1/4 = 0.4
− p-p cross section (fixed target): σ(90 GeV) / σ(920 GeV) = 0.7
− At the same ion current and vacuum, MEIC background should be about 10% of HERAo Can run higher ion currents (0.1 A at HERA)o Good vacuum is easier to maintain in a shorter section of the ring
• Backgrounds do not seem to be a major problem for the MEIC− Placing high-luminosity detectors closer to ion exit arc helps with both background types
− Beyond arcs proton/ion beams get manipulated (crab crossing angle), electron beam stays straight to go through detector minimizes synchroton radiation
− Signal-to-background will be considerably better at the MEIC than HERAo MEIC luminosity is more than 100 times higher (depending on kinematics)
Backgrounds and detector placement