e rhic the future qcd machine

eRHIC THE FUTURE QCD MACHINE

E.C. ASCHENAUERBNL

ERHIC DESIGN REVIEW, AUGUST 2011 2

THE PILLARS OF THE ERHIC PHYSICS PROGRAM

E.C. ASCHENAUER

Hadronisationspin Physics3D Imigingphysics of

strong color fields

Electro Weak

Wide physics program with high requirements on detector and machine performance


MOST COMPELLING PHYSICS QUESTIONS

spin physics

what is the polarization of gluons atsmall x where they are most abundant

what is the flavor decomposition ofthe polarized sea depending on x

determine quark and gluon contributionsto the proton spin at last

what is the spatial distribution ofquarks and gluons in nucleons/nuclei

imaging

possible window toorbital angular momentum

understand deep aspects of gaugetheories revealed by kT dep. distr’n

E.C. ASCHENAUER

physics of strong color fields

how do hard probes in eA interact with the medium

quantitatively probe the universality ofstrong color fields in AA, pA, and eA

understand in detail the transition to the non-linear regime of strong gluon fields and the physics of saturation


THE PROBE: DEEP INELASTIC SCATTERING

E.C. ASCHENAUER

Measure of resolution powerMeasure of inelasticityMeasure of

momentum fraction of struck quark

Kinematics:

Quark splitsinto gluonsplitsinto quarks …

Gluon splitsinto quarks

higher √sincreases resolution

10-19m

10-16m


WHAT DO WE KNOW

E.C. ASCHENAUER

small x

large x

Observation of large scaling violations

Strong increase of sea quarks towards

low x Density increases with Q2

more partons by magnified view

quark density

Dynamic creation of partons

at low x

gluon density

valence quarks

x=1

x=10-5

Gluon density dominates

eA-coverage


current theory (DGLAP) has a built in energy catastrophe G rapid raise violates unitary bound

HOW MANY GLUONS HAVE SPACE IN A PROTON?

E.C. ASCHENAUER

Bremsstrahlung~ asln(1/x)

x = Pparton/Pnucleon

small x / higher energy

Recombination~ asr

as~1 as << 1

Saturation must set in at low x high occupancy space becomes crowded gluons start to overlap

recombination

Terra Incognita

BK/JIMWLK non-linear evolution includes recombination effects saturation

Dynamically generated scale Saturation Scale: Q2

s(x) Increases with energy or decreasing x

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


eRHIC - REACHING THE SATURATION REGIME

E.C. ASCHENAUER

Saturation: dAu: Strong hints from RHIC at x ~ 10-3

p: Weak hints at Hera up to x=6.32⋅10-5, Q2 = 1-5 GeV2

Kowalski, Lappi and Venugopalan, PRL 100, 022303 (2008)); Armesto et al., PRL 94:022002; Kowalski, Teaney, PRD 68:114005)

Nuclear Enhancement:Hera

Coverage:Need lever arm in Q2 at

fixed x to constrain models

Need Q > Qs to study onset of saturation

ep: even 1 TeV is on the low sideeA: √s = 50 GeV is marginal, around √s = 100 GeV

desirable 20 GeV x 100 GeV


SATURATION IN eA DIS – WHAT TO EXPECT

E.C. ASCHENAUER

estimate relevance of non-linear effects from average strength of dipole scattering in DIS

recall: DIS in the proton rest frame: photon splits into a quark-antiquark pair (“color dipole”) which scatters off the target proton (= “slow” gluon field)

dipole amplitude

dipolesize r


SATURATION IN eA DIS

E.C. ASCHENAUER

quantitative estimatesM. Diehl, T. Lappi

HERA

EIC 30

x 32

5<NL> in ep DIS

0.2

0.3

0.4

x

Q2 [

GeV

2 ]find: most sensitive to gluons

as expected (HERA): no chance in ep

eA much more favorable to study saturation than ep

EIC 30

x 13

0<NL> in eAu DIS

EIC 5

x 1300.2

0.3

0.4

0.5

0.6

saturation effectsin eA benefit from

nuclear oompf


DEEP INELASTIC SCATTERING - VACUUM

tp

production time tp - propagating quark

htf

formation time htf - dipole grows to hadron

What happens if we add a nuclear medium

E.C. ASCHENAUER

Observables:Broadening:

Attenuation:link Dpt

2 directly with saturation scale (B. Kopeliovich)

modifications of nPDF cancel out


WHAT DO WE KNOW AND WHAT CAN EIC DO

E.C. ASCHENAUER

z

Eq = = Ee-Ee’ 13 GeVEh = z 2-15 GeV

Hermes: EIC:light hadronsCharm

Unprecedented precisionto distinguish between

Different processes


IMPORTANT TO UNDERSTAND HADRON STRUCTURE: SPIN

E.C. ASCHENAUER

SqDq

DG

Lg

SqLq

dq1Tf

SqDq

DG

Lg

SqLq dq1Tf

Is the proton spinning like this?

“Helicity sum rule”

total u+d+squark spin

angular momentum

gluonspin Where do we go with

solving the “spin puzzle” ?

N. BohrW. Pauli


Polarised opposite to proton spin

NLO FIT TO WORLD DATA

E.C. ASCHENAUER

includes all world data from DIS, SIDIS and pp

DSSV PRD 80 (2009) 034030

Du(x) > 0Polarised parallel to proton spin

Dd(x) < 0

LDRD: 08-004 Knowledge todayQuarks: 30%

Gluons: close to nothing??? Where is the spin of the proton ???


EIC: WHAT IS THE SPIN OF THE GLUONS ΔG?

E.C. ASCHENAUER

x

RHICpp

DIS&pp

• low x behavior unconstrained• no reliable error estimate for 1st moment (entering spin sum rule)

• find

pQCD scaling violations

pos

itive

Dg

cross section:

parameterizedthrough

F2, FL, g1, g2


use precise EIC data for different beam energies in theoretical extraction

..wow-cool, will finally know the contribution of the gluons to the spin of the proton

THE ANSWER ON DG WILL BE REVEALED

E.C. ASCHENAUER


Nobel Prize, 1943: "for his contribution to the development of the molecular ray method and his discovery of the magnetic moment of the proton" mp = 2.5 nuclear magnetons, ± 10% (1933)

Otto Stern Proton spins are used to image the structure and function of the human body using the technique

of magnetic resonance imaging.

Paul C. Lauterbur

Sir Peter Mansfield

Nobel Prize, 2003: "for their discoveries concerning magnetic resonance imaging"

THE SPIN OF THE PROTON IN 3D

E.C. ASCHENAUER


QUANTUM PHASE-SPACE TOMOGRAPHY OF THE NUCLEON

E.C. ASCHENAUER

3D picture in momentum space 3D picture in coordinate space transverse momentum generalized parton distributions dependent distributions exclusive reaction like DVCS

Polarized p d-quarku-quark Polarized p

Join the real 3D experience !!

TMDs GPDs

Wigner DistributionW(x,r,kt)


THE SIVERS FUNCTION

E.C. ASCHENAUER

HERMES:

EIC: 1 month @ 20 GeV x250 GeV

Sivers


GPDS AND THE HUNT FOR Lq

E.C. ASCHENAUER

Study of hard exclusive processes allows to access

a new class of PDFsGeneralized Parton Distributions

possible way to accessorbital angular momentum

exclusive: all reaction products are detected missing energy (DE) and missing Mass (Mx) = 0

From DISSpin Sum Rule in PRF:

E.C. ASCHENAUER

Goal: Cover wide range in t impact parameter space bDVCS AT eRHIC


e’

(Q2)e

gL*x+ξ x-ξ

H, H, E, E (x,ξ,t)~~

g

p p’t

Study by S. Fazio and M. Diehl


DIFFRACTIVE PHYSICS: p’ KINEMATICS

5x250

5x100

5x50

E.C. ASCHENAUER

t=(p4-p2)2 = 2[(mpin.mpout)-(EinEout - pzinpzout)]

“ Roman Pots” acceptance studies see later?

Diffraction:

p’


GOLDEN MEASUREMENTS: PHYSICS OF STRONG COLOR FIELDS

E.C. ASCHENAUER

ScienceDeliverable

BasicMeasurement Detector Requirements Machine

Requirements

integrated gluon distributions

nuclear wave fct.saturation, Qs

inclusive DISF2,L

very good electron ID very good momentum and angular resolution for e’

need to reach x~10-4 large x,Q2 coverage medium lumi highest √s

kT-dependent gluons;gluon correlations

non-linear QCD evolution/universality

semi-inclusive DISdi-hadron

correlations

very similar to inclusive DIS excellent particle ID wide coverage range in h

need to reach x~10-4 large x,Q2 coverage medium lumi highest √s

transport coefficients in cold nuclear matter

parton energy loss;shower evolution

energy loss mechanism

semi-inclusive DIS;light and heavy

hadrons (c,b), Jets

very good electron ID very good momentum and angular resolution for e’ excellent particle ID excellent vertex resolution

large x,Q2 coveragemulti-dim binning

medium - high lumi low - high √s


ScienceDeliverable


Requirements

spin structure at small xcontribution of Δg, ΔΣ

to spin sum ruleinclusive DIS

very good electron ID very good momentum and angular resolution for e’

need to reach x=10-4 large x,Q2 coverage

about 10fb-1

medium lumi high √s

full flavor separationin large x,Q2 range

strangeness, s(x)-s(x)polarized sea

semi-inclusive DISvery similar to inclusive DISexcellent particle ID separate p, K, p over a wide range in h

need to reach x=10-4 large x,Q2 coveragepolarized 3He beam

medium lumi high √s

electroweak probesof proton structureflavor separation

electroweak parameters

very high Q2

hadronic final state

very good coverage for hadronic final state kinematic from q-jet

20x250 to 30x325positron beam

polarized 3He beam high lumi highest √s

GOLDEN MEASUREMENTS: SPIN PHYSICS

E.C. ASCHENAUER


ScienceDeliverable


Requirements

Sivers + unpol PDFvalence, sea quarks & gluons• quantum interference • multiparton correlations• spin-orbit correlations & role of OAM • matching low-high pT

semi-inclusive DIStransverse nucl. pol.di-hadron/(di-jets)heavy-flavor production

very good electron ID very good momentum and angular resolution for e’ excellent particle ID separate p, K, p over a wide range in h full F-coverage around g* excellent vertex res.

large x,Q2 coverage5D binning high lumi

low - high √s

chiral odd fcts.valence, sea quarks & gluons• transversity & IFF• Collins-FF• Boer-Mulders fct.

semi-inclusive DIS as above as above

quark and gluon imaging via GPDs

in bT-spaceaccess to Lq and Lg

exclusive DIS DVCS, J/Ψ, r, F

very good electron ID very good momentum and angular resolution for e’ exclusivity and high resolution in t Roman pots

large x,Q2,t coverage4D binning

polarized beams high lumi

low - high √s

GOLDEN MEASUREMENTS: 3D-IMAGING IN bT / kT

E.C. ASCHENAUER


EMERGING DETECTOR CONCEPT

E.C. ASCHENAUER

high acceptance -5 < h < 5 central detectorgood PID (p,K,p and lepton) and vertex resolution (< 5mm)tracking and calorimeter coverage the same good momentum resolution, lepton PIDlow material density minimal multiple scattering and brems-strahlungvery forward electron and proton/neutron detection maybe dipole spectrometers

Forward / BackwardSpectrometers:


0.44

843

m

Q5 D5Q4

90.08703 m60.0559 m

10

0.25

82 m

INTEGRATION INTO MACHINE: IR-DESIGN

E.C. ASCHENAUER

3 m

4.5

q=4 mrad10.26m

39.98 m

q=10.3255 mrad

10 mrad5.3 m

0.31

5726

m3020

q=0.0036745 mrad

eRHIC - Geometry high-lumi IR with β*=5 cm, l*=4.5 mand 10 mrad crossing angle this is required for 1034 cm-2 s-1

Outgoing Proton direction already far advanced

30 GeV e-

325 GeV p

125 GeV/u ions


PROTON DISTRIBUTION IN y VS x AT s=20m

25x250 5x50

E.C. ASCHENAUER

without quadrupole aperture limit

25x250 5x50with quadrupole aperture limit


ACCEPTED IN “ROMAN POT” (EXAMPLE) AT s=20m

25x250 5x50

E.C. ASCHENAUER

25x250 5x50

GeneratedQuad aperture limitedRP (at 20m) accepted


KINEMATICS OF BREAKUP NEUTRONS

E.C. ASCHENAUER

Results from GEMINI++ for 50 GeV Au

by Thomas Ullrich+/-5mrad acceptance seems sufficient

Results:With an aperture of ±3 mrad we are in relative good shape• enough “detection” power for t > 0.025 GeV2

• below t ~ 0.02 GeV2 we have to look into photon detection‣ Is it needed?Question:• For some physics rejection power for incoherent is

needed ~104

How efficient can the ZDCs be made?


AND SUMMARY Machine and Detector Requirements determined from

golden measurements Variable beam energies and hadron beam species Need √s ~ 100 GeV to reach saturation regime High Polarisation for light hadrons and lepton beams High luminosity (~100 x Hera)

o Exclusive reactionso Multidimensional binning for semi-inclusive observableso Electroweak physics

Detector integration in IR design is critical Dedicated detector critical to realize the physics

program

E.C. ASCHENAUER

CURRENT eRHIC MACHINE DESIGN ADDRESSES ALL REQUIREMENTS

FROM THE PHYSICS PROGRAM

ERHIC DESIGN REVIEW, AUGUST 2011 31E.C. ASCHENAUER

BACKUP


DO GLUONS CREATE THE VISIBLE MASS?

E.C. ASCHENAUER

That is us !!!protons, neutrons

electrons

Atom10-10m

Nucleus10-14mProtons

Quarks & Gluons10-16m

Binding-energy: ~eV

Binding-energy: 8.5 106 eV

Binding-energy: ~109 eVQuark-Masses: 106-107 eVmass completely dominated by gluon


HOW ARE THE GLUONS DISTRIBUTED IN SPACE

E.C. ASCHENAUER

Experimental Requirement:

Photo-production c.s. large & |t| ~ pt2(VM)

J/Y easy to detect for |h| < 2 well separated from background Crucial: detecting breakup of nuclei

started to be included in simulation Need e’ to measure t for Q2>10-3 GeV2

Basic Idea:Exclusive diffractive VM production eA e’A’V dsA/dt fourier transform Fg(b) Promising method to measure gluon form factor in nuclei long wavelength gluons (small t)

Kowalski, Caldwell ‘09

Th. Ullrich, T. TollLDRD 10-042

based on saturatedgluon distribution


strategy to quantify impact: global QCD fit with realistic toy data

• DIS data sets produced for stage-1 [5x50, 5x100, 5x250, 5x325] and 20x250, 30x325•

W2 > 10GeV2 W2 > 10GeV2

POLARIZED DIS AND IMPACT ON ΔG(X,Q2)

E.C. ASCHENAUER

ECA+M. Stratmann


ACCEPTANCE FOR FORWARD SCATTERED PROTONS

E.C. ASCHENAUER

25x250

25x250

GeneratedQuad aperture limitedRP (at 20m) accepted

e’

t

(Q2)e

gL*x+ξ x-ξ

H, H, E, E (x,ξ,t)~~

g

p p’

Exclusive events:e+p/A e’+p’/A’+g / J/ψ / r / fdetect all event products in the detector


PROCESSES USED TO STUDY THE PHYSICS

E.C. ASCHENAUER

exclusive /diffractive reactions

ep/A e’p’/A’VM

semi-inclusivereactionsep/A e’pX

electro-weak

reactions

inclusivereactionsep/A e’X

Close to 4pacceptance

Excellentelectron

identificationPID:

to identifyHadrons

Backgroundsuppression

Detectoutgoing scattered proton

Detect very low Q2

electron

good jetidentification

excellentabsoluteand/or

relativeluminosity

very precisepolarization

measurementhigh demands onmomentum and/orenergy resolutiongood vertex

resolution


CMOS-PIXEL VERTEX DETECTOR FOR eRHIC

E.C. ASCHENAUER

Silicon Detectors at Atlas (61 m2) and CMS (198 m2) CMS: huge radiation length impossible to use for

eRHIC electrons do bremsstrahlung Pixel Detector for eRHIC (LDRD: 11-036)

Radiation length 0.05% Pixel-layer-thickness: 50mm not 300 -500 readout electronics integrated in Pixel current “chip” sizes 1x2cm2

o to small for forward / backward diskso Plan: extend to 5x5cm2 with 10M pixels with 16 mm pitch o Vertex resolution ~5mm

Useful for any application, which needs high resolution and low material budget

e rhic the future qcd machine

Documents