e rhic the future qcd machine
DESCRIPTION
e RHIC THE future QCD machine. E.C. Aschenauer BNL. The Pillars of the eRHIC Physics program. spin Physics. Hadronisation. Electro Weak. physics of strong color fields. 3D Imiging. Wide physics program with high requirements on detector and machine performance. - PowerPoint PPT PresentationTRANSCRIPT
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
ERHIC DESIGN REVIEW, AUGUST 2011 3
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
ERHIC DESIGN REVIEW, AUGUST 2011 4
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
ERHIC DESIGN REVIEW, AUGUST 2011 5
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
ERHIC DESIGN REVIEW, AUGUST 2011 6
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 DESIGN REVIEW, AUGUST 2011 7
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
ERHIC DESIGN REVIEW, AUGUST 2011 8
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
ERHIC DESIGN REVIEW, AUGUST 2011 9
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
ERHIC DESIGN REVIEW, AUGUST 2011 10
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
ERHIC DESIGN REVIEW, AUGUST 2011 11
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
ERHIC DESIGN REVIEW, AUGUST 2011 12
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
ERHIC DESIGN REVIEW, AUGUST 2011 13
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 ???
ERHIC DESIGN REVIEW, AUGUST 2011 14
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
ERHIC DESIGN REVIEW, AUGUST 2011 15
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
ERHIC DESIGN REVIEW, AUGUST 2011 16
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
ERHIC DESIGN REVIEW, AUGUST 2011 17
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)
ERHIC DESIGN REVIEW, AUGUST 2011 18
THE SIVERS FUNCTION
E.C. ASCHENAUER
HERMES:
EIC: 1 month @ 20 GeV x250 GeV
Sivers
ERHIC DESIGN REVIEW, AUGUST 2011 19
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
ERHIC DESIGN REVIEW, AUGUST 2011 20
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
ERHIC DESIGN REVIEW, AUGUST 2011 21
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’
ERHIC DESIGN REVIEW, AUGUST 2011 22
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
ERHIC DESIGN REVIEW, AUGUST 2011 23
ScienceDeliverable
BasicMeasurement Detector Requirements Machine
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
ERHIC DESIGN REVIEW, AUGUST 2011 24
ScienceDeliverable
BasicMeasurement Detector Requirements Machine
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
ERHIC DESIGN REVIEW, AUGUST 2011 25
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:
ERHIC DESIGN REVIEW, AUGUST 2011 26
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
ERHIC DESIGN REVIEW, AUGUST 2011 27
PROTON DISTRIBUTION IN y VS x AT s=20m
25x250 5x50
E.C. ASCHENAUER
without quadrupole aperture limit
25x250 5x50with quadrupole aperture limit
ERHIC DESIGN REVIEW, AUGUST 2011 28
ACCEPTED IN “ROMAN POT” (EXAMPLE) AT s=20m
25x250 5x50
E.C. ASCHENAUER
25x250 5x50
GeneratedQuad aperture limitedRP (at 20m) accepted
ERHIC DESIGN REVIEW, AUGUST 2011 29
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?
ERHIC DESIGN REVIEW, AUGUST 2011 30
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
ERHIC DESIGN REVIEW, AUGUST 2011 32
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
ERHIC DESIGN REVIEW, AUGUST 2011 33
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
ERHIC DESIGN REVIEW, AUGUST 2011 34
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
ERHIC DESIGN REVIEW, AUGUST 2011 35
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
ERHIC DESIGN REVIEW, AUGUST 2011 36
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
ERHIC DESIGN REVIEW, AUGUST 2011 37
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