news from the eic

RHIC/AGS User Meeting, June 2009

1

News from the EIC

E.C. Aschenauer

Thanks to everybody to let me use slides, plots, ……..

RHIC/AGS User Meeting, June 2009 2

QCD and confinement

E.C. Aschenauer

Large DistanceLow Energy

Small DistanceHigh Energy

Perturbative QCD Strong QCD

High Energy Scattering

GluonJets

Observed

Spectroscopy

GluonicDegrees of Freedom Missing

Search for mesons with exotic quantum numbers


Nature of Glue The major driver: “Nature of Glue”

Despite the success of QCD our knowledge about glue is limited - we know it plays a dominant role:

DIS ⇒ only 1/2 of a proton's momentum is carried by the quarks

Completely dominates the structure of matter at low-x

Quenched QCD explains mass spectrum to ± 10%Dominates structure of QCD vacuum (⇒ mass?)

Glue determines essential features of strong interactions

E.C. Aschenauer


Questions to Address with the EIC

E.C. Aschenauer

What is the nature of glue at high density? How do strong fields appear in hadronic or nuclear wave

functions at high energies? Do gluon densities saturate?

What drives saturation, what’s the underlying dynamics What are the appropriate degrees of freedom

(Pomerons?)Does the Color Glass Condensate describe matter at

low-x? Universality of gluon dynamics & energy dependence Is there a “fixed” point where all hadronic matter have

a component of their wave function with the same behavior

Could a better knowledge of glue help solve the longstanding problem of confinement in QCD?

What’s the role in gluons in the nuclear structure?


What to Measure and in What System?

Understanding the role of the glue in matter involves understanding its key properties which in turn define the required measurements:What is the momentum distribution of the gluons in matter?

e+p and e+AExploration of saturation regime only possible in e+A

What is the space-time distributions of gluons in matter?

e+p and e+AUnknown in e+A

How do fast probes interact with the gluonic medium?Strength of e+A

Do strong gluon fields effect the role of color neutral excitations (Pomerons)?

e+p and e+AUnknown in e+AE.C. Aschenauer

Deep Inelastic Scattering

E.C. Aschenauer RHIC/AGS User Meeting, June 2009 6

( , )E k( ', ')E k

q

Important kinematic variables:

cross section:DF FF

2

~'

Ld

d dEW

1 2 1 22 ( )p p i i

g q s q p qsF gs pF gW q

1 2 3 41 1 1

( ) ( ) ( )6 2 2

r s t u s u s tb b b b

Spin 1

2 2 2( ')Q q k k

x

Q2

2 pqQ2

yhE

z

Photon:

Hadron:

Quark:

2tp

y pqpk

1−E'

Eco2(q

'

2)


Measure Glue through DIS

E.C. Aschenauer

Scaling violation: dF2 /dlnQ2

and linear DGLAP Evolution ⇒ G(x,Q2)


Issues with our Current Understanding

E.C. Aschenauer

Linear DGLAP evolution scheme Weird behavior of xG from

HERA at small x and Q2 G(x,Q2) < Qsea(x,Q2) ? Unexpectedly large

diffractive cross-section built in high energy

“catastrophe”- xG rapid rise violates

unitary bound Linear BFKL Evolution

Density along with grows as a power of energy: N ~ sΔ

Can densities & cross-section rise forever?

Black disk limit: total ≤ 2 p R2


Universality & Geometric Scaling Crucial consequence of non-

linear evolution towards saturation:Physics invariant along trajectories

parallel to saturation regime (lines of constant gluon occupancy)

Scale with Q2/Q2s(x) instead of x and

Q2 separately

⇐ Geometric ScalingConsequence of saturation

which manifests itself up to kT > Qs

x < 0.01

E.C. Aschenauer


FL: measure glue directly

Assume:L = 3.8 1033 cm-2 s-1

T = 10 weeksduty cycle: 50%L ~ 1/A (approx) ∫Ldt = 11 fb-1

Plot contains: ∫Ldt = 4/A fb-1 (10+100) GeV = 4/A fb-1 (10+50) GeV = 2/A fb-1 (5+50) GeVstatistical errors only

FL ~ αs G(x,Q2) requires √s scan Q2/xs = y

⇒ G(x,Q2) with great precision

Can start at 2+100 GeV!E.C. Aschenauer


Parton Propagation and Fragmentation

HERMES

EICnDIS: •Suppression of high-pT hadrons analogous but weaker than at RHIC EIC: Clean measurement in ‘cold’ nuclear matter•Energy transfer in lab rest frame

‣ EIC: 10 < ν < 1600 GeV HERMES: 2-25 GeV

‣ EIC: can measure heavy flavor energy loss

Nuclear Modification Measure:

Work in Progress:Simulation with PYTHIA 6.4.19

• 10 weeks of beam at eRHIC• 10+100 GeV• Large reach in Q2 and pT

• small ν - hadronization inside A• large ν - precision tests of QCD

‣ parton energy loss‣ DGLAP evolution and showers

p

E.C. Aschenauer


How do the partons contribute

E.C. Aschenauer

SqΔq

ΔG

Lg

SqLq

dq1Tf

SqΔq

ΔG

Lg

SqLq dq1Tf

Is the proton spinning like this?

“Helicity sum rule”

12h P,12 |JQCΔ

z |P,12 12q

∑ SqzSgz Lqzq∑ Lgz

total u+d+squark spin

angular momentum

gluonspin Where do we stand

solving the “spin puzzle” ?

N. BohrW. Pauli


Polarized Quark Distributions

E.C. AschenauerDSSV: arXiv:0904.3821

EIC: 10GeV@250GeV at 9 fb-1

X

0.2

-0.8

0.

0.8

How to measure ΔS and ΔG


ΔG: Indirect from scaling violation

g1@EIC

Integrated Lumi: 5fb-1

The Gluon Polarization


x

RHIC range0.05· x · 0.2

small-x0.001< x < 0.05

large-xx > 0.2

Δg(x) very small at medium x best fit has a node at x ~ 0.1 huge uncertainties at small x

Δg(x) small !?Δg(x) dx

0.

1

∫ = −0.084@10GeV 2Need to enlarge x-range

g*p D0 + X


Beyond form factors and quark distributions

E.C. Aschenauer

Generalized Parton Distributions

Proton form factors, transverse charge & current densities

Structure functions,quark longitudinalmomentum & helicity distributions

X. Ji, D. Mueller, A. Radyushkin (1994-1997)

Correlated quark momentum and helicity distributions in transverse space - GPDs

How to access GPDs?


quantum number of final state selects different GPDs: theoretically very clean DVCS (g): H, E, H, E VM (r, w, f): H E info on quark flavors PS mesons (p, h): H E ~

~ ~

~

ρ0 2ud, 9g/4ω 2ud, 3g/4f s, g

ρ+ ud

J/ψ g

p0 2ΔuΔdh 2ΔuΔd

Jq

z 12

xdx H q E q( )−1

1

∫⎛⎝

⎞⎠t→ 0

J q

z 12

Δqq∑ Lq

z

q∑

12Jq

z Jgz

12

Δqq∑ Lq

z

q∑ Jg

z

Deeply Virtual Compton Scattering


HERMES / JLAB kinematics: BH >> DVCS

two experimentally undistinguishable processes:

DVCS Bethe-Heitler (BH)

p + Δ

( )* 2 2*~ | | | |BH DVCS DVC BS HB DVCSHd t t t t t t

isolate BH-DVCS interference term non-zero azimuthal asymmetries

€

d / dp d dg(pb / GV r2 )

H, %H, E, %Emost clean channel for interpretation in terms of GPDs

can measure DVCS – cross section and I

Hermes BCA CLAS BSA

Hall A Hall A

different GPD parametrisations

Results from Theory


cont

ribu

tion

to

nucl

eon

spin

mp2 GeV2

LHPC Collab. hep-lat/0705.4295

Lattice:K. Kumericki & D. MuellerarXiv: 0904.0458

t=0

t=-0.3

First hints for a small Jq Lq


DVCS @ EIC

E.C. Aschenauer

Need wide x and Q2 range to extract GPDs Need sufficient luminosity to bin in multi-dimensions


ERL-based eRHIC Design

E.C. Aschenauer

10 GeV electron design energy.

Possible upgrade to 20 GeV by

doubling main linac length. 5 recirculation passes ( 4 of

them in the RHIC tunnel) Multiple electron-hadron

interaction points (IPs) and detectors;

Full polarization transparency at all energies for the electron beam;

Ability to take full advantage of transverse cooling of the hadron beams;

Possible options to include polarized positrons: compact storage ring; compton backscattered; undulator-based. Though at lower luminosity.

Four recirculation passes

PHENIX

STAR

e-ion detector

eRHIC

Main ERL (1.9 GeV)

Low energy recirculation pass

Beam dump

Electronsource

Possible locationsfor additional e-ion detectors


ERL-based eRHIC Parameters: e-p modeHigh energy setup Low energy setup

p e p e

Energy, GeV 250 10 50 3

Number of bunches 166 166

Bunch spacing, ns 71 71 71 71

Bunch intensity, 21011 1.21011 2 1.2

Beam current (mA) 420 260 420 260

Normalized 95% emittance (p mm mrad) 6 460 6 570

Rms emittance, nm 3.8 4 19 16.5

b*, x/y, cm 26 25 26 30

Beam-beam parameters, x/y 0.015 0.59 0.015 0.47

Rms bunch length, cm 20 1 20 1

Polarization, % 70 80 70 80

Peak Luminosity,

Aver. Luminosity x1.e33 cm-2s-1

2.610 33 cm-2 s-1 0.5310 33 cm-2 s-1

0.87 0.18

Luminosity integral /week pb-1 530 105E.C. Aschenauer

23

ERL-based eRHIC Parameters: e-Au mode


High energy setup Low energy setupAu e Au e

Energy, GeV 100 10 50 3

Number of bunches 166 166

Bunch spacing, ns 71 71 71 71Bunch intensity, 1011 1.1 1.2 1.1 1.2Beam current, mA 180 260 180 260

Normalized 95% emittance (p mm.mrad) 2.4 460 2.4 270

Rms emittance (nm) 3.7 3.8 7.5 7.8b*, x/y (cm) 26 25 26 25Beam-beam parameters x/y 0.015 0.26 0.015 0.43Rms bunch length (cm) 20 1 20 1Polarization (%) 0 0 0 0

Peak e-nucleon luminosity

Average e-nucleon luminosity 1.e33 cm-2s-1

2.91033 cm-2 s-1 1.51033 cm-2 s-1

1.0 0.5Luminosity integral /week pb-1 580 290

E.C. Aschenauer


Pre-cooling of the protons at the injection energy (22 GeV) is required to achieve proton beam-beam limit (xp=0.015) and maximize the luminosity. It can be done by electron cooling (in ~1h).

To reduce the electron current requirements it would be great to have the effective transverse cooling at the storage energy (250 GeV) which can effectively counteract IBS and maintain the emittance well below 6p mm*mrad. Recent revival of the Coherent Electron Cooling idea (V.N.Litvinenko, Ya.S.Derbenev) brings the possibility of the effective longitudinal and transverse cooling for high energy protons. Proof of principle test of CEC has been suggested at RHIC.

no cooling

Luminosity and cooling

E.C. Aschenauer 24


Medium Energy EIC in RHIC: race track concept

E.C. Aschenauer 25

Geometrical constraints: If it is possible use the existing interaction region at RHIC 2 o’clock and wider tunnel to place the superconducting linac inside it. Minimize civil construction cost and use for eRHIC already built and installed linac.


IR2 Hall: Detector and Injector System

E.C. Aschenauer

Polarized gun200 keV DCwith combiner cavity

WienSpin rotator 5 (10) MeV

Linac

Bunching section

Beam Dump250 (500) kW

95 MeVERL

Soft bend0.05T, 1m


Requirements from Physicsep-physics

the detector needs to cover inclusive semi-inclusive exclusive reactions

large acceptance absolutely crucial particle identification (p,K,p,n) over wide momentum range excellent vertex resolution (charm) particle detection for very low scattering angle

uncertainty for e/p polarization measurements luminosity measurement uncertainty

eA-physicsrequirements very similar to ep

most challenging get information on recoiling heavy ion

from exclusive and diffractive reactions.

E.C. Aschenauer


First ideas for a detector concept

E.C. Aschenauer

/ TRD

Dipol3Tm

Dipol3Tm

Solenoid (4T)


Accelerator and detector integration and SR protection

E.C. Aschenauer

Solenoid (4T)

Dipole~3Tm

Dipole~3Tm

To provide effective SR protection:-soft bend (~0.05T) is used for final bending of electron beam-combination of vertical and horizontal bends

J.Beebe-Wang, C.Montag, B.Parker, D.Trbojevic


ELIC Figure-8 Collider Ring Footprint

E.C. Aschenauer

60°

Medium Energy IP

Low Energy IP

Snake Insertion

Arc 157 m

Figure-8 straight 150 m

Insertion 10 m

Circumference 634 m

Ring design is optimized with Synchrotron radiation power of e-beam

prefers large ring (arc) length Space charge effect of i-beam

prefers small ring circumference

Multi IPs require long straight sections

Straight sections also hold required components (e-cooling, injection and ejections, etc.)

WM

SURA

City of NNState

City of NN

ELIC Footprint (~1800m)

MEIC Footprint (~600m)

CEBAF


EIC@JLab at Low to Medium Energy

E.C. Aschenauer

Three compact rings:• 3 to 11 GeV electron• Up to 12 GeV/c proton

(worm)• Up to 60 GeV/c proton (cold)

polarimetry


EIC@JLab Parameters at Low-to-Medium Energy

E.C. Aschenauer

Beam Energy GeV 60/5 60/3 12/3Collision freq. MHz 499Particles/bunch 1010 0.74/2.9 1.1/6 0.47/2.3Beam current A 0.59/2.3 0.86/4.8 0.37/2.7Energy spread 10-4 ~ 3RMS bunch length mm 5 5 50Horz. emit., norm. μm 0.56/85 0.8/75 0.18/80Vert. emit. Norm. μm 0.11/17 0.8/75 0.18/80Horizontal beta-star mm 25 25 5Vertical beta-star mm 5Vert. beam-beam tune shift / IP 0.01/0.03 0.015/0.08 0.015/0.013Laslett tune shift (p-beam) 0.1 0.054 0.1

Peak Luminosity/IP, 1034 cm-2s-1 1.9 4.0 0.59


ELIC at High Energy & Staging

E.C. Aschenauer

Ion Sources

SRF Linac

p

e

e e

pp

prebooster

ELIC collider

ring

MEIC collider

ring

injector

12 GeV CEBAF

Ion ring

electron ring

Vertical crossing

Interaction Point

Small Large

Circumference m 1800 2500

Radius m 140 180

Width m 280 360

Length m 695 920

Straight m 306 430

Stage Max. Energy (GeV/c)

Ring Size (M)

Ring Type IP#

p e p e p e

1 Low 12 5 (11) 630 630 Warm Warm 1

Medium 60 5 (11) 630 630 Cold Warm 2

2 Medium 60 10 600 1800 Cold Warm 4

3 High 250 10 1800 1800 Cold Warm 4


EIC@JLab Parameters: High Energy

E.C. Aschenauer

Beam Energy GeV 250/10 150/7Collision freq. MHz 499Particles/bunch 1010 1.1/3.1 0.5/3.25Beam current A 0.91/2.5 0.4/2.6Energy spread 10-4 3RMS bunch length mm 5Horz. beta-star mm 125 75Vert. beta-star mm 5Horz. emit., norm. μm 0.7/51 0.5/43Vert. emit. Norm. μm 0.03/2 0.03/2.87B-B tune shift per IP 0.01/0.1 0.015/0.05Laslett tune shift (p-beam) 0.1 0.1

Lumi. per IP, 1034 cm-2s-1 11 4.1

Major design change: symmetric IR asymmetric IR


Summary and A lot of work a head of us

need to finalize a compelling physics case for medium and high energy EIC

need to come from a detector sketch to a detector designsimulate golden physics channels in a detector

frame-work start machine, detector and “physics” R&D

have several LDRDs submittedeverybody who wants to join is more than welcome; regular TF meetings Thursday @ 2pm at BNL

2 proposals in Europe: low energy: ENC @ FAIR (e: 3.5 GeV, p: 15GeV) high energy: LHeC @ CERN (e: 70 – 140GeV, p/A: LHC)

E.C. Aschenauer

A wealth of science @ EIC

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