Unpolarized quark distributions: valence quarks and sea quarks
x X here is x-bjorken. In DIS it can be measured explicitly event by event In p-p scattering it is not possible to use it, but can be inferenced from MC events generation.
7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 80 Deep Inelastic Scattering: Precision and control
Kinematics: Q2 = −q2 = −(k − k" )2 Measure of µ µ resolution 2 power Q = 2Ee Ee"(1 − cosΘe ' ) pq E" %θ" ( y 1 e cos2 e Measure of = = − ' * inelasticity pk Ee & 2 ) Q2 Q2 Measure of High lumi & acceptance x = = momentum Exclusive DIS 2 pq sy fraction of detect & identify everything e+p/A à e’+h(p,K,p,jet)+… struck quark Hadron : Semi-inclusive events: e+p/A à e’+h(p,K,p,jet)+X Eh detect the scattered lepton in coincidence with identified hadrons/jets z = ; pt E*/"$.#,=#-/$/%$g* ν Inclusive events: e+p/A à e’+X s = 4 Eh Ee Low lumi & acceptance detect only the scattered lepton in the detector
6/24/21 NNPSS 2021 EIC Lecture 3 81 The x-Q2 Plane
y = 0.95 Energy s y = const 2 2 Q s x y ⇡ · · log Q The x-Q2 y = 0.01
plane… y = const
log x 1 • Low-x reach requires large √s • Large-Q2 reach requires large √s • y at colliders typically limited to 0.95 < y < 0.01
!18
7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 82 Kinematic coverage as a function of energy of collisions
5 x 50 10 x 100
As beam energies increase, so does the x, Q2 coverage of the collider: 5, 10 20 x 250 and 20 GeV electrons colliding with 50, 100 and 250 GeV protons y = 0.95 and 0.01 are shown on all plots (they too shift as function of energy of collisions)
7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 83 7/04/2014 Questions in Hadron Physics: RHIC Spin 25 Monte Carlo Generated events: for a pT range of pions produced what is the x of the leading parton that created the pion p+p à pi + X Principle LimitationsStart with any polarized gluon distribution and• Limited produce P_T distribution x-range of pions or gamma distribution. • Need to widen it… See bottom. • Higher and lower Center of Mass For any pTOperationrange, one see one sees the x distribution of the originating partons associated• PHENIX with it. measured at 62 GeV CM
There is a large overlap. The lowest pT distribution end at 10^{-2}.
Any thingExtendsignificantly less to than pT of 2 is going to be difficult to measure and identify inlower detectors. x at √s = 500 GeV 7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 84
• Overlapping x for p bins T • Need more exclusive π measurements (Luminosity) x • γ-Jet (PHENIX VTX upgrade) √ • Jet-Jet (STAR ready)
Abhay Deshpande Center for Frontiers in Nuclear Science Electron Ion Collider The Electron Ion Collider Abhay Deshpande Lecture 3 of 3 Lecture 1 of 3
NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider
85 Abhay Deshpande Overview of these lectures: Understanding the structure of matter
Lecture 3: Electron Ion Collider: Frontiers in investigations of QCD • Solving the spin puzzle è 3D imaging of the nucleon • Gluons in nuclei: what role in nuclei? Do they saturate?
• Designing an EIC detector and Interaction Region (IR) • EIC: Status and prospects • What can you do for the US EIC?
7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 86 Center for Frontiers in Nuclear Science
Electron Ion Collider: Science, Status & Prospects
2018 2015 2016 2019 2019 - future
Realization Physics of EIC Evaluation
6/24/21 NNPSSAbhay 2021 Deshpande EIC Lecture 3 87 On the menu today:
• Highlights of the Electron Ion Collider science
• The EIC project setup • Machine, detector & call for proposal
• EIC Users Group aspirations & recent developments • Proto-Collaborations/consortia…
• Realization and the path forward (particularly for experiments)
6/24/21 NNPSS 2021 EIC Lecture 3 88 Deep Inelastic Scattering: Precision and control
Kinematics: Q2 = −q2 = −(k − k" )2 Measure of µ µ resolution 2 power Q = 2Ee Ee"(1 − cosΘe ' ) pq E" %θ" ( y 1 e cos2 e Measure of = = − ' * inelasticity pk Ee & 2 ) Q2 Q2 Measure of High lumi & acceptance x = = momentum Exclusive DIS 2 pq sy fraction of detect & identify everything e+p/A à e’+h(p,K,p,jet)+… struck quark Hadron : Semi-inclusive events: e+p/A à e’+h(p,K,p,jet)+X Eh detect the scattered lepton in coincidence with identified hadrons/jets z = ; pt E*/"$.#,=#-/$/%$g* ν Inclusive events: e+p/A à e’+X s = 4 Eh Ee Low lumi & acceptance detect only the scattered lepton in the detector
6/24/21 NNPSS 2021 EIC Lecture 3 89 Ep proton beam energy Ee electron beam energy p =(0, 0,Ep,Ep) four momentum of incoming proton with mass mp e =(0, 0, °Ee,Ee) four momentum of incoming electron 0 0 0 0 0 0 e =(Eesinµe, 0,Eecosµe,Ee) four momentum of scattered electron 2 s =(e + p) =4EpEe square of total ep c.m. energy q2 =(e ° e0)2 = °Q2 mass squared of exchanged current J = square of four momentum transfer ∫ = q · p/mp energy transfer by J in p rest system ∫max = s/(2mp)maximumenergytransfer y =(q · p)/(e · p)=∫/∫max fraction of energy transfer x = Q2/(2q · p)=Q2/(ys) Bjorken scaling variable 0 qc = x · p +(e ° e ) four momentum of current quark 2 0 2 M =(e + qc) = x · s mass squared of electron - current quark system.
0 The electron and proton masses (me,mp) have been neglected. The angle µe of the scattered electron is measured with respect to the incoming proton (see Fig. 1b). For simplicity, the scattered electron has been assumed to have zero azimuthal angle. For p fixed c.m. energy s,theinclusiveprocessep ! eX is described by two Lorentz- invariant variables which can be determined from the electron or the hadronic system. The electron side yields:
0 Ee 0 y =1° (1 ° cosµe) 2Ee 2 0 0 Q =2EeEe(1 + cosµe) 0 0 x = Ee(1 + cosµe)/(2yEp) 0 Ee =(1° y)Ee + xyEp xyE E°j (1 ° y)E cosµ0 x = p (1 + cosµej)/(1 ° y) Some times scatterede =electron2Ep can’t be measured…. xyEp +(1° y)Ee 0 2 2 0 Ej = yEe + x(1 ° y)Ep Ee sin µe =4xy(1 ° y)EeEp . (3) Reason: ° yEe +(1° y)xEp cospµj = 1) ScatteringWith theangle help so of small the relation that it isM too= closex · stothe theyE variable beame +(1 pipe°x ycan)xE bep replaced by the mass 2 2 2 2) RadiativeM of correction the electron too current large, quark i.e. Eelectronj system.sin µj lost=4 itsxy (1energy° y)E edueEp = toQ Initial(1 ° yState) . Radiation or(4) BrehmstrahlungNeglectingthrough the proton material remnant, -- So the the hadron kinematic system reconstructionj,withenergy unreliable.E and production Using the method of Jacquet-Blondel [8] the hadron variablesj can be determined What toangle do? µThen,yields: see if we can reconstruct the hadronic final state? j approximately by summing the energies (E ) and transverseEj (p ) and longitudinal h x = (1Th + cosµj)/(1 ° y) momenta (p ) of all final state particles. The method2 restsEp on the assumption Zh Ej that the total transversey = momentum(1 ° cos carriedµj) by thoseEj hadrons= yE whiche + x(1 escape° y)E detectionp 2Ee through the beam hole in the proton direction as well as the energy° yEe carried+(1° byy)xE particlesp 2 2 2 cosµ Q = E sin µj/(1 ° y) j = escaping through the beamj hole in the electron direction canyE be neglected.e +(1° y) ThexEp result is: E2sin2µ xy y E E Q2 y . 3 j j =4 (1 ° ) e p = (1 ° ) (4) 1 yJB = (Eh ° pZh) Using the2E methode of Jacquet-Blondel [8] the hadron variables can be determined Xh approximately by summing2 the energies2 (Eh) and transverse (pTh) and longitudinal 2 ( h pXh) +( h pYh) QmomentaJB = (pZh) of all final state particles. The method rests on the assumption P 1 ° yJBP that the total2 transverse momentum carried by those hadrons which escape detection xthroughJB = theQJB beam/(yJB holes) in the proton direction as well as the (5) energy carried by particles escaping through the beam hole in the electron direction can be neglected. The result 7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 90 The double-angle (DA) methodis: of [1] uses the electron scattering angle and the angle ∞h which characterizes the longitudinal and transverse momentum1 flow of the hadronic system (in the naive quark-parton model y∞JBis= the scattering(Eh ° anglepZh) of the h 2Ee struck quark): Xh ( p )2 +( p )2 Q2 = h Xh h Yh 2 2 JB 2 y ( h pXh) +( h pYh) ° ( h(Eh ° pZhP)) 1 ° JBP cos∞ = 2 (6) h 2 2 x = Q /2(y s) (5) (Ph pXh) +(Ph pYh) +(PhJB(Eh ° pZhJB)) JB P P P leading to The double-angle (DA) method of [1] uses the electron scattering angle and the angle ∞h which characterizes the longitudinal and transverse momentum flow of the 2 0 hadronic4E systemsin∞h (in(1 +thecos naiveµ ) quark-parton model ∞ is the scattering angle of the Q2 e e h DA = 0 0 strucksin∞ quark):h + sinµe ° sin(∞h + µe) 0 0 Ee sin∞h + sinµe + sin(∞2h + µe) 2 2 xDA = · ( h pXh) +( h pYh) ° ( h(Eh ° pZh)) E sin∞ cos+∞hsin=µ0 ° sin(∞ + µ0 ) (6) p h (e p )2h +(e p )2 +( (E ° p ))2 Ph0 Xh Ph Yh Ph h Zh sin∞h (1 + cosµe) y = P P P DA sin∞ sinµ0 sin ∞ µ0 leading toh + e + ( h + e) (1 ° cos∞ ) sinµ0 = h e 0 0 4E2sin∞ (1 + cosµ0 ) sin∞h + sinµe °Q2sin(∞h + µe) e h e DA = 0 0 2 sin∞h + sinµe ° sin(∞h + µe) = QDA/(xDAs) . (7) E sin∞ + sinµ0 + sin(∞ + µ0 ) x e h e h e DA = · 0 0 4 Ep sin∞h + sinµe ° sin(∞h + µe) sin∞ (1 + cosµ0 ) y h e DA = 0 0 sin∞h + sinµe + sin(∞h + µe) 0 (1 ° cos∞h) sinµe = 0 0 sin∞h + sinµe ° sin(∞h + µe) 2 = QDA/(xDAs) . (7)
4 Deep Inelastic Scattering: Deeply Virtual Compton Scattering Kinematics: e’ Measure of 2 2 2 resolution g Q = −q = −(k − k" ) e µ µ power 2 gL*(Q ) 2 Q = 2Ee Ee"(1 − cosΘe ' ) x+ξ x-ξ % ( Measure of ~ ~ pq E" 2 θ" H, H, E, E (x,ξ,t) y = = 1 − e cos ' e * inelasticity p p’ pk Ee & 2 ) t 2 2 Q Q Measure of Exclusive measurement: xB = = momentum e + (p/A) à e’+ (p’/A’)+ g / J/ψ / r / f 2 pq sy fraction of struck quark detect all event products in the detector x t = ( p − p')2 ,ξ = B Special sub-event category rapidity gap events 2 − x e + (p/A) à e’ + g / J/ψ / r / f / jet B Don’t detect (p’/A’) in final state à HERA: 20% non- exclusive event contamination missing mass technique as for fixed target does not 7/15/2019work NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 91 Complete set of variables for DIS e-p: https://core.ac.uk/download/pdf/25211047.pdf We will use some of these more often than others, you should know them all.
Ep proton beam energy Ee electron beam energy p =(0, 0,Ep,Ep) four momentum of incoming proton with mass mp e =(0, 0, °Ee,Ee) four momentum of incoming electron 0 0 0 0 0 0 e =(Eesinµe, 0,Eecosµe,Ee) four momentum of scattered electron 2 s =(e + p) =4EpEe square of total ep c.m. energy q2 =(e ° e0)2 = °Q2 mass squared of exchanged current J = square of four momentum transfer ∫ = q · p/mp energy transfer by J in p rest system ∫max = s/(2mp)maximumenergytransfer y =(q · p)/(e · p)=∫/∫max fraction of energy transfer x = Q2/(2q · p)=Q2/(ys) Bjorken scaling variable 0 qc = x · p +(e ° e ) four momentum of current quark 2 0 2 M =(e + qc) = x · s mass squared of electron - current quark system.
7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 92
0 The electron and proton masses (me,mp) have been neglected. The angle µe of the scattered electron is measured with respect to the incoming proton (see Fig. 1b). For simplicity, the scattered electron has been assumed to have zero azimuthal angle. For p fixed c.m. energy s,theinclusiveprocessep ! eX is described by two Lorentz- invariant variables which can be determined from the electron or the hadronic system. The electron side yields:
0 Ee 0 y =1° (1 ° cosµe) 2Ee 2 0 0 Q =2EeEe(1 + cosµe) 0 0 x = Ee(1 + cosµe)/(2yEp) 0 Ee =(1° y)Ee + xyEp
0 xyEp ° (1 ° y)Ee cosµe = xyEp +(1° y)Ee 0 2 2 0 Ee sin µe =4xy(1 ° y)EeEp . (3) p With the help of the relation M = x · s the variable x can be replaced by the mass M of the electron current quark system.
Neglecting the proton remnant, the hadron system j,withenergyEj and production angle µj,yields:
Ej y = (1 ° cosµj) 2Ee 2 2 2 Q = Ej sin µj/(1 ° y) 3 Kinematic coverage as a function of energy of collisions
5 x 50 10 x 100
As beam energies increase, so does the x, Q2 coverage of the collider: 5, 10 20 x 250 and 20 GeV electrons colliding with 50, 100 and 250 GeV protons y = 0.95 and 0.01 are shown on all plots (they too shift as function of energy of collisions)
7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 93 Home Work: Where do electrons and quarks go?
Angles measured w.r.t. proton direction
0 0 q,e 177 160 p q 10 GeV x 250 GeV
100 10 GeV
5 GeV 5 GeV 900
scattered electron scattered quark
7/15/2019 NNPSS 2021: UNAM/IU: Lectures94 on the Electron Ion Collider Electron, Quark Kinematics q,e p q 5 GeV x 50 GeV
scattered electron scattered quark
7/15/2019 NNPSS 2021: UNAM/IU: Lectures95 on the Electron Ion Collider There are multiple ways to reconstruct events: Four measured quantities: E0 , ✓,E ,
e p/A
7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 96 QCD Landscape to be explored by a future facility
QCD at high resolution (Q2) —weakly correlated quarks and gluons are well-described
Strong QCD dynamics creates many-body correlations between quarks and gluons à hadron structure emerges
Systematically explore correlations in this region. : 1708.01527 An exciting opportunity: Observation of a new regime in arXiv QCD of weakly coupled high-density matter
Need Precision and Control
6/24/21 NNPSS 2021 EIC Lecture 3 97 EIC Physics at-a-Glance
How are the sea quarks and gluons, and their spins, distributed in space and momentum inside the nucleon? How do the nucleon properties (mass & spin) emerge from their interactions?
How do color-charged quarks and gluons, and colorless jets, interact with a nuclear medium? How do the confined hadronic states emerge from these quarks and gluons? How do the quark-gluon interactions create nuclear binding? QS: Matter of QDefinitionS: Matter andof Definition Frame (II) and Frame (II) Infinite Momentum Frame: How does a dense nuclear environmentInfinite affect the Momentum quarks and gluons, Frame: their correlations, and their interactions?• BFKL (linear QCD): splitting• BFKL functions(linear QCD): ⇒ gluon splitting density functions grows ⇒ gluon density grows What happens to the gluon density in• nucleiBK (non-linear):? Does it saturate recombination at high• BK (non-linear):gluon of gluons recombination ⇒ gluon density ofgluon gluons tamed ⇒ gluon density tamed energy, giving rise to a gluonic matter with universal properties in all emission recombination nuclei, even the proton? ? BFKL: BFKL: BK adds:= BK adds: 6/24/21 NNPSS 2021 EIC Lecture 3 98
• At Qs: gluon emission• Atbalanced Qs: gluon by recombinationemission balanced by recombination ) ) 2 T 2 T k k Unintegrated gluon distribution ~ 1/kT ~ 1/k Unintegrated gluon distribution
(x, T (x, φ
φ depends on kT and x:
T depends on kT and x: T k k the majority of gluonsthe have majority of gluons have transverse momentumtransverse kT ~ QS momentum kT ~ QS (common definition)
max. density max. (common definition) max. density max. know how to ? do physics here know how to ? do physics here
αs ∼ 1 ΛQCD Qs αs << 1 k TQ αs ∼ 1 ΛQCD s αs << 1 kT 7 7 EIC: Kinematic reach & properties
10 3 Current polarized DIS data: For e-N collisions at the EIC: 3 CERN DESY JLab SLAC ü Polarized beams: e, p, d/ He Current polarized BNL-RHIC pp data: ü Variable center of mass energy PHENIX π0 STAR 1-jet ü Wide Q2 range à evolution 2 ) 10 2 ü Wide x range à spanning valence 0.95 0.95 ≤ ≤ y y ≤ ≤ to low-x physics (GeV 2 Q 10 s= 140 GeV, 0.01 s= 65 GeV, 0.01 √ √ EIC EIC
1
-4 -3 -2 -1 10 10 10 10 1 For e-A collisions at the EIC: x ü Wide range in nuclei ü Lum. per nucleon same as e-p ü Variable center of mass energy ü Wide x range (evolution) ü Wide x region (reach high gluon densities)
2/15/18 Exploring the Glue That Binds Us All @ UCR 99 Nucleon Spin: Precision with EIC
1 1 = ⌃ + L +[ g + L ] 2 2 Q G DS/2 = Quark contribution to Proton Spin g1 ~ - Dg = Gluon contribution to Proton Spin LQ = Quark Orbital Ang. Mom )
LG = Gluon Orbital Ang. Mom -3 0.3 5 DSSV 2014
) 2
2 g1(x,Q ) uncertainty 0.2 2 2 Spin structure function g1 needs to be Q =10 GeV < x 10 -6 (x,Q eRHIC pseudo-data 2 1 0.1 measured over a large range in x-Q g 0 -0
Precision in DS and Dg è A clear idea -0.1 -5 EIC Of the magnitude of LQ+LG = L √s=44.7 GeV -0.2 √s=44.7−70.7 GeV √s=44.7−141.4 GeV s = 141.4 GeV s = 63.2 GeV s = 44.7 GeV dx (Quarks + Gluons) (10 √ √ √ SIDIS: strange and charm quark spin -0.3 -5 -4 -3 -2 -1 − ∫ -0.2 0 0.2 10 10 10 10 10 1 contributions x -3 ½ - ∫dx (Quarks + Gluons) (10 < x < 1) 6/24/21 NNPSS 2021 EIC Lecture 3 100 2+1D Imaging of hadrons: beyond precision PDFs
Precision PDFs and TMDs valuable for LHC(?) Near future promise of direct Comparison with lattice QCD
6/24/21 Figure 2.2: Connections between di↵erent quantities describingNNPSS 2021 the EIC distributionLecture 3 of partons 101 inside the proton. The functions given here are for unpolarized partons in an unpolarized proton; analogous relations hold for polarized quantities.
tum, and specific TMDs and GPDs quan- for heavy nuclei, the theoretical descriptions tify the orbital angular momentum carried based on either parton distributions or color by partons in di↵erent ways. dipoles are both applicable and can be re- The theoretical framework we have lated to each other. This will provide us with sketched is valid over a wide range of mo- valuable flexibility for interpreting data in a mentum fractions x, connecting in particular wide kinematic regime. the region of valence quarks with the one of The following sections highlight the gluons and the quark sea. While the present physics opportunities in measuring PDFs, chapter is focused on the nucleon, the con- TMDs and GPDs to map out the quark- cept of parton distributions is well adapted gluon structure of the proton at the EIC. to study the dynamics of partons in nuclei, as An essential feature throughout will be the we will see in Sec. 3.3. For the regime of small broad reach of the EIC in the kinematic x, which is probed in collisions at the highest plane of the Bjorken variable x (see the Side- energies, a di↵erent theoretical description is bar on page 18) and the invariant momentum at our disposal. Rather than parton distribu- transfer Q2 to the electron. While x deter- tions, a basic quantity in this approach is the mines the momentum fraction of the partons amplitude for the scattering of a color dipole probed, Q2 specifies the scale at which the on a proton or a nucleus. The joint distri- partons are resolved. Wide coverage in x bution of gluons in x and in kT or bT can is hence essential for going from the valence be derived from this dipole amplitude. This quark regime deep into the region of gluons high-energy approach is essential for address- and sea quarks, whereas a large lever arm in ing the physics of high parton densities and Q2 is the key for unraveling the information of parton saturation, as discussed in Sec. 3.2. contained in the scale evolution of parton dis- On the other hand, in a regime of moder- tributions. 3 ate x, around 10 for the proton and higher
17 Exclusive Processes and Generalized Parton Distributions
Generalized parton distributions (GPDs) can be extracted from suitable exclusive scat- tering processes in e+p collisions. Examples are deeply virtual Compton scattering (DVCS: + p + p) and the production of a vector meson ( + p V + p). The virtual photon ⇤ ! ⇤ ! is provided by the electron beam, as usual in deep inelastic scattering processes (see the Sidebar on page 18). GDPs depend on three kinematical variables and a resolution scale:
x + ⇠ and x ⇠ are longitudinal par- The crucial kinematic variable for par- • • ton momentum fractions with respect ton imaging is the transverse momen- to the average proton momentum (p + tum transfer = p p to the T T0 T p0)/2 before and after the scattering, as proton. It is related to the invariant 2 shown in Figure 2.18. square t =(p0 p) of the momentum 2 2 2 Whereas x is integrated over in the transfer by t = ( T +4⇠ M )/(1 2 scattering amplitude, ⇠ is fixed by the ⇠ ), where M is the proton mass. process kinematics. For DVCS one has ⇠ = x /(2 x ) in terms of the usual B B Bjorken variable x = Q2/(2p q). For The resolution scale is given by Q2 B · • the production of a meson with mass in DVCS and light meson production, M one finds instead ⇠ = x /(2 x ) whereas for the production of a heavy V V V with x =(Q2 + M 2 )/(2p q). meson such as the J/ it is M 2 +Q2. V V · J/ Even for unpolarized partons, one has a nontrivial spin structure, parameterized by two functions for each parton type. H(x, ⇠,t) is relevant for the case where the helicity of the proton is the same before and after the scattering, whereas E(x, ⇠,t) describes a proton helicity flip. For equal proton four-momenta, p = p0, the distributions H(x, 0, 0) reduce to the familiar quark, anti-quark and gluon densities measured in inclusive processes, whereas the forward limit E(x, 0, 0) is unknown. Weighting with the fractional quark charges eq and integrating over x, one obtains a relation with the electromagnetic Dirac and Pauli form factors of the proton:
q p q p eq dx H (x, ⇠,t)=F1 (t) , eq dx E (x, ⇠,t)=F2 (t) (2.14) q q 2+1 D partonic imageX ofZ the proton with theX EICZ Spin-dependent 3D momentum space images fromand an analogousSpin relation-dependent to the neutron 2D coordinate form factors. space At small (transverse)t the Pauli + 1D form factors semi-inclusive scattering (SIDS) of the proton and(longitudinal the neutron are momentum) both large, so images that the from distributions exclusiveE for scattering up and down quarks cannot be small everywhere. Transverse Momentum Distributions Transverse Position Distributions ⇤ ⇤ V Quarks Gluons: Only @ Motion x + ⇠ x ⇠ x + ⇠ x ⇠ Collider 2 1.5 -3 4GeV 0fm 10 = = = 2 p x p0 p p0 x 1.0 b Q
Deeply Virtual Compton Scattering 0.5 Fourier transform of momentum → 0.0 Figure 2.18: Graphs for deeply virtual(fm) Compton scattering (left) and for exclusivesea 2 vector-2 Measure all three final states y xq (x,b ,Q ) (fm ) b meson production (right) in terms of generalizedtransferred=(p parton distributions,-p’) à Spatial which distribution are0.0 represented0.5 1.0 1.5 by -0.5 e + p à e’+ p’+ g -1.5 the lower blobs. The upper filled oval in the right figure represents the meson wave function. -1.0 -1.0 -1.5 -0.5
1.5 1.0 0.5 0.0 2D position distribution for sea-quarks
b
) (fm ) ,Q (x,b
xq y
-2 2 sea
⇑ 0.0
Possible measurements of K (s) and D (c) (fm) → 42 unpolarized polarized → → q(x=10-3,b,Q2 = 4 GeV2) q⇑(x=10-3,b,Q2 = 4 GeV2) 0.5 Q b
[0.9, 1.00] 2 2 x 1.0 x 2 = = 1.5 = 1.5 1.5 [0.9, 0.99] -3 -3 2 10 0fm 4GeV 4GeV 0fm 10 4GeV 0fm 1.5
10 [0.9, 0.97] -3 -3 = 1.5 = = = = = 2 x 4GeV 0fm 2 1 [0.9, 0.94] 10 x x 1.0 1.0 x 2 b Q b Q = = = 2
x [0.8, 0.90] x 1.0 b Q 0.5 [0.7, 0.80] 0.5 0.5 [0.6, 0.70] 0.5 [0.5, 0.60] 0 → (fm) 0.0 (fm) (fm) 0.0 ⇑sea 2 -2 y y y xq (x,b[0.4,,Q 0.50]) (fm ) b b 0.0 (fm) b 0.0 0.5 1.0 1.5 [0.3, 0.40] y b -0.5 [0.2, 0.30] -0.5 -0.5 -1.5
[0.1, 0.20] -0.5 -1 [0.0, 0.10] -1.0 -1.0 -1.0 [0.0, 0.05] -1.0 -1.5 sea [0.0,→ 0.02]2 -2
-1.5 xq (x,b,Q ) (fm ) -1.5 -0.5
[0.0, 0.01] -1.5 0.0 0.5 1.0 1.5 -1.5 -1 -0.5 0 0.5 1 1.5 -1.5 -1 -0.5 0 0.5 1 1.5
0.0 0.5 1.0 1.5
1.5 1.0 0.5 0.0
1.5 1.0 0.5 0.0
b
-1.5
) (fm ) ,Q (x,b xq
) (fm ) ,Q (x,b
xq (x,b ,Q (fm ) ) xq
y
-2 2 sea -2 2 sea
b (fm) b (fm) ⇑ sea 2 ⇑ -2 (fm)
x x 0.0 → → →
6/24/21 NNPSS 2021 EIC Lecture 3 -1.0 104 0.5 -0.5 2 2 Q b 1.0 x x 2 1.5 1.5 = = = -3 -3 b 10 0fm 4GeV 4GeV 0fm 10 4GeV 0fm y 10 0.0 (fm) = = -3 = = = = 1.5 2 x 1.0 x 2 x b 1.0 x Q b Q 2 0.5 0.5 0.5 Q b x 1.0 x 2 (fm) 0.0 = = = y (fm) 0.0 b 10 y 0fm 4GeV b -3 1.5 -0.5 2 -0.5 -1.0 -1.0
→ -1.5
xq⇑sea(x,b,Q2) (fm-2) -1.5
0.0 0.5 1.0 1.5
1.5 1.0 0.5 0.0
) (fm ) ,Q (x,b xq
-2 2
0.0 0.5 1.0 sea 1.5 → -1.5 xq (x,b ,Q (fm ) ) sea → 2 -2 -1.0 -0.5 b y (fm) 0.0 0.5 Q b 1.0 x x 2 = = = 10 0fm 4GeV -3 1.5 2 2+1 D partonic image of the proton with the EIC
Spin-dependent 3D momentum space Spin-dependent 2D coordinate space images from semi-inclusive scattering (transverse) + 1D (longitudinal momentum) images from exclusive scattering Transverse Momentum Distributions Transverse Position Distributions
e + p → e + p + J/ψ 4 15.8 < Q2 + M2 < 25.1 GeV2 20 sea-quarks xV J/ψ 3 u-Quark 25 Gluons-1 15 unpolarized fb polarized 2 0.12 50 20 2 10 0.1 t = 1 0.08 s Ld 4 0.16 < x < 0.25 0.06 10 n ∫ V 0 0.04 1 o 40 15 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0.02
150 u
l 3 0
g 1.2 1.4 1.6
5 f 30 10 2 o 6 0.12
n 0.1
−1 o 1 0.08 100 20 5 i 5 t 0.06 0.016 < xV < 0.025
10 u 0 0.04 b 4 i 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0.02 r
10 x t 0 s 3 −2 i 1.2 1.4 1.6 50 D 10 2 0.12 0.1 1 0.08 0.06 0.0016 < xV < 0.0025 −3 0 0.04 1 10 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0.02 0 0.2 0.4 0.6 0.8 0 Quark transverse momentum (GeV) 1.2 1.4 1.6 bT (fm)
2/15/18 Exploring the Glue That Binds Us All @ UCR 105 Study of internal structure of a watermelon:
A-A (RHIC) 1) Violent collision of melons
2) Cutting the watermelon with a knife Violent DIS e-A (EIC)
3) MRI of a watermelon Non-Violent e-A (EIC)
7/15/2019 NNPSS 2021: UNAM/IU: Lectures on the Electron Ion Collider 107 Emergence of Hadrons from Partons Nucleus as a Femtometer sized filter Unprecedented ν, the virtual photon energy range Energy loss by light vs. heavy quarks: @ EIC : precision & control 1.50
1.30
lead over proton proton lead over 1.10 Q2 Study in light quarks ⌫ = vs. 0.90 2mx heavy quarks 0.70 Pions (model-I) Pions (model-II) D0 mesons
0.50 x > 0.1 25 GeV2 < Q2 < 45 GeV2 Ratio of particles produced in 140 GeV < ν < 150 GeV ∫Ldt = 10 fb-1 0.30 0.0 0.2 0.4 0.6 0.8 1.0 Fraction of virtual photons energy Control of ν by selecting kinematics; carried by hadron, z Also under control the nuclear size. Identify p vs. D0 (charm) mesons in e-A collisions:
(colored) Quark passing through cold QCD matter emerges Understand energy loss of light vs. heavy quarks as color-neutral hadron è traversing the cold nuclear matter: Clues to color-confinement? Connect to energy loss in Hot QCD Need the collider energy of EIC and its control on parton kinematics 6/24/21 NNPSS 2021 EIC Lecture 3 108 EIC: impact on the knowledge of 1D Nuclear PDFs Valence Sea Gluon 1.5 1.5 1.5 Q2=1.69 GeV2 Q2=1.69 GeV2 Q2=1.69 GeV2 )
2 1 1 1 (x,Q i
R 0.5 EPPS16 0.5 0.5 EIC w/o charm EIC with charm 0 0 0 10-3 10-2 10-1 1 10-3 10-2 10-1 1 10-3 10-2 10-1 1 x x x
Ratio of1.5 Parton Distribution Functions1.5 of Pb over Proton: 1.5 2 2 2 2 2 2 vWithoutQ EIC,=10 large GeV uncertainties in nuclearQ =10 GeV sea quarks and gluonsQ =10è WithGeV EIC
significantly) reduced uncertainties
2 1 1 1 vComplementary to RHIC and LHC pA data. Provides information on initial state for (x,Q i
heavyR 0.5 ion collisions. 0.5 0.5 vDoes the nucleus behave like a proton at low-x? è such color correlations relevant to
the understanding0 of astronomical0 objects 0 10-3 10-2 10-1 1 10-3 10-2 10-1 1 10-3 10-2 10-1 1 2/15/18 x Exploring the Glue That Binds Usx All @ UCR x 109 Low x physics with nuclei Reaching the Saturation Region HERA (ep): Despite high energy range: 2 1/3 F2, Gp(x, Q ) outside the • A 2 2 A saturation regime (Qs ) cQ0 Boost ⇡ x Key Topic in eA: Gluon Saturation• Need (I) also Q2 lever arm! Only way in ep is to In QCD, the proton• is made up increase &s of quanta that fluctuate in and ' -1 1/3 &!()* • Would require an ep L ~ (2m x) > 2 R ~ A out of existence N A !"##""$ collider at &s ~ 1-2 TeV pQCD Boosted proton: Probe interacts coherently • 2 evolution Different approach (eA): Accessiblewith allrange nucleons of saturation scale Qs at the EIC with e+A ' ‣ equation Fluctuations time dilated on 1/3 collisions.
21"& strong interactionA time2 2# A& 9 (Q ) " cQ arXiv:1708.01527 QS: Matter of QDefinitionS: Matter andof Definition Frame (II) and Framescales (II)s 0 % ( x ≤ 0.01 $ x ' ‣ Long lived gluons can !+,-.+,/01 radiate further small x Infinite MomentumInfinite Frame: Momentum Frame: "%"$ EIC √smax = 40 GeV (eAu) 101345.,-.6+,/75".58/01 ! gluons! 8 BFKL (linear QCD): splitting21") functions gluon‣ densityExplosion growsof gluon density • BFKL (linear QCD): splitting• functions ⇒ gluon density grows⇒ ! EIC √smax = 90 GeV (eAu) BK (non-linear): recombination of gluons gluon! violates density unitarity tamed • BK (non-linear): recombination• gluonof gluons ⇒ gluon density tamedgluon⇒ 300 GeV HERA (ep) emission recombination New Approach: Non-Linear Evolution perturbative regime 2 BFKL: BFKL: New evolution= equations at low-xAt Q S& low to moderate Q •BK adds: BK adds: 0 0.5 1 1.5 2 2.5 Saturation of gluon densities characterized by scale Qs(x) 2 2 • 2 Λ QS (GeV ) 6/24/21 • Wave function is Color Glass Condensate NNPSSQCD 2021 EIC Lecture 3 110 6 • At Qs: gluon emission Atbalanced Qs: gluon by recombinationemission balanced by recombination 2 • Figure 6: Accessible values of the saturation scale Qs at an EIC in e+A collisions assuming two di↵erent maximal 2 center-of-mass energies. The reach in Qs for e+p collisions at HERA is shown for comparison. ) ) 2 T 2 T k k Unintegrated gluon distribution ~ 1/kT ~ 1/k Unintegrated gluon distribution 2 (x, T pared to psmax = 40 GeV. The di↵erence in Qs At high energies, this dipole scattering ampli- (x, φ
φ depends on kT and x:
may appear relatively mild but we will demon- tude enters all relevant observables such as the to- T depends on kT and x: T k k the majority of gluons have strate in the following that this di↵erence is su - tal and di↵ractive cross-sections. It is thus highly the majority of cientgluons to generate have a dramatic change in DIS observ- relevant how much it can vary given a certain col- transverse momentumtransverse kT ~ QS momentumables with increased kT ~ Q center-of-massS energy. This lision energy. If a higher collision energy can pro- (common definition) is analogous to the message from Fig. 5 where we vide access to a significantly wider range of values max. density max. (common definition)clearly observe the dramatic e↵ect of jet quench- for the dipole amplitude, in particular at small x, max. density max. ing once ps is increased from 39 GeV to 62.4 it would allow for a more robust test of the satu- know how to NN ? do physics here know how to GeV and beyond. ration picture. ? do physics here To compute observables in DIS events at high
αs ∼ 1 ΛQCD Qs αs << 1 k energy, it is advantageous to study the scattering TQ αs ∼ 1 ΛQCD s αs << 1 kT 7 process in the rest frame of the target proton or nucleus. In this frame, the7 scattering process has two stages. The virtual photon first splits into a quark-antiquark pair (the color dipole), which subsequently interacts with the target. This is il- lustrated in Fig. 7. Another simplification in the high energy limit is that the dipole does not change its size r (transverse distance between the quark and antiquark)? over the course of the interaction with the target. Figure 7: The forward scattering amplitude for DIS Multiple interactions of the dipole with the tar- on a nuclear target. The virtual photon splits into a get become important when the dipole size is of the qq¯ pair of fixed size r , which then interacts with the ? order ~r 1/Qs. In this regime, the imaginary target at impact parameter b . | ?| ⇠ ? part of the dipole forward scattering amplitude N(~r ,~b ,x), where ~b is the impact parameter, To study the e↵ect of a varying reach in takes? on? a characteristic? exponentiated form [16]: Q2, one may, to good approximation, replace r in (1) by the typical transverse resolution scale? 2 2 ~ r Qs(x, b ) 1 2/Q to obtain the simpler expression N 1 N =1 exp ? ? ln , (1) ⇠ 4 r ⇤! exp Q2/Q2 . The appearance of both Q2 and ? s s Q2 in the exponential is crucial. Its e↵ect is where ⇤ is a soft QCD scale. demonstrated in Fig. 8, where the dipole ampli-
11 Can EIC discover a new state of matter?
EIC provides an absolutely unique opportunity counting experiment of to have very high gluon densities Di-jets in ep and eA à electron – lead collisions Saturation: combined with an unambiguous observable Disappearance of backward jet in eA EIC will allow to unambiguously map the transition from a non-saturated to e p e A saturated regime
Coverage of Saturation 1.4 √s=40 GeV 2 2
Region for Q > 1 GeV ep / √s=63 GeV √s=90 GeV 10 0.95 ep √smax=90 GeV ≤ ) 1.2 eA √smax=40 GeV φ
0.95 Δ ≤ = 90 GeV, y
) s 2
/C( 1
s = 40 GeV, y EIC (eAu) eAu ) (GeV 2 φ increased suppression
Q 0.8 EIC (eAu) Δ à C( 0.6
1 Q 2 Q 2 S (U) S (Fe) Q 2 Q 2 (Xe) (Au) increased √s Q 2 S S S (Ca) 0.4
#backward jets in #backward jets 2 2.5 3 3.5 4 − − − 10 4 10 3 10 2 Δφ (rad) 6/24/21 x NNPSS 2021 EIC Lecture 3 111 Diffraction in Optics and high energy scattering
Light with wavelength l obstructed by an opaque Calculation of e-A diffraction disk of radius R suffers diffraction: k à wave number t k2✓2 1 | | ⇡ ✓ i (kR) ⇠ Light Incoherent/Breakup Intensity /dt σ d Coherent/Elastic
0 θ1 θ2 θ3 θ4 Angle
t1 t2 t3 t4 2/15/18 Exploring the Glue That Binds Us All @ UCR|t| 112
Figure 3.13: Left panel: The di ractive pattern of light on a circular obstacle in wave optics. Right panel: The di ractive cross-section in high energy scattering. The elastic cross-section in the right panel is analogous to the di ractive pattern in the left panel if we identify t k2 2. | | ⇥
1/(kR) for small-angle di raction. (i) The proton/nuclear target is not always i Elastic scattering in QCD has a similar an opaque “black disk” obstacle of geomet- structure. Imagine a hadron (a projectile) ric optics. A smaller projectile, which in- scattering on a target nucleus. If the scat- teracts more weakly due to color-screening tering is elastic, both the hadron and the nu- and asymptotic freedom, is likely to pro- cleus will be intact after the collision. The duce a di erent di ractive pattern from the elastic process is described by the di eren- larger, more strongly interacting, projectile. tial scattering cross-section d⇥el/dt with the (ii) The scattering in QCD does not have to Mandelstam variable t describing the mo- be completely elastic: the projectile or tar- mentum transfer between the target and the get may break up. The event is still called projectile. A typical d⇥el/dt is sketched by di ractive if there is a rapidity gap, as de- the solid line in the right panel of Fig. 3.13 scribed in the Sidebar on page 61. The cross- as a function of t.Identifyingtheprojectile section for the target breakup (leaving the hadron with the incident plane wave in the projectile intact) is plotted by the dotted line wave optics example, the target nucleus with in the right panel of Fig. 3.13, and does not the obstacle, and writing t k2 2 valid for exhibit the di ractive minima and maxima. | | ⇥ small angles, we can see that the two pan- The property (i) is very important for els of Fig. 3.13 exhibit analogous di ractive di raction in DIS in relation to satura- patterns and, therefore, describe very simi- tion/CGC physics. As we have seen above, lar physics! The minima (and maxima) of owing to the uncertainty principle, at higher 2 the cross-section d⇥el/dt in the right panel Q , the virtual photon probes shorter trans- of Fig. 3.13 are also related to the inverse verse distances, and is less sensitive to sat- size of the target squared, t 1/R2.This uration e ects. Conversely, the virtual pho- | i| is exactly the same principle as employed for ton in DIS with the lower Q2 is likely to be spatial imaging of the nucleons as described more sensitive to saturation physics. Due to in Sec. 2.3. the presence of a rapidity gap, the di rac- The essential di erence between QCD tive cross-section can be thought of as aris- and wave optics is summarized by two facts: ing from an exchange of several partons with
73 Transverse imaging of the gluons nuclei
Diffractive vector meson production in e-Au Diff. MC: “Sartre” d ,g ∫Ldt = 10 fb-1/A coherent - no saturation ∫Ldt = 10 fb-1/A coherent - no saturation 4 5 10 1 < Q2 < 10 GeV2 incoherent - no saturation 10 1 < Q2 < 10 GeV2 incoherent - no saturation x < 0.01 coherent - saturation (bSat) x < 0.01 coherent - saturation (bSat)
) |η(edecay)| < 4 incoherent - saturation (bSat) |η(Kdecay)| < 4 incoherent - saturation (bSat) ) 2
p(e ) > 1 GeV/c 2 4 p(K ) > 1 GeV/c 3 decay 10 decay 10 δt/t = 5% δt/t = 5%
103 102 ) /dt (nb/GeV /dt ) /dt (nb/GeV /dt ψ φ 102 10 10 e’ e’ Au’+ + e’ e’ Au’+ + J/ → → 1 1 (e + Au(e +
è Au(e +
Does low x dynamics (Saturation) modify the σ σ d transversed gluon10-1 distribution? 10-1 J/ψ φ
Experimental10-2 challenges being studied. 10-2 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 |t | (GeV2) |t | (GeV2) Simulation study by Toll & Ullrich 2/15/18 Figure 3.23: d /dt distributionsExploring for exclusive the Glue ThatJ/ Binds Us(left) All @ UCR and (right) production in coherent and 113 incoherent events in di↵ractive e+Au collisions. Predictions from saturation and non-saturation models are shown.
pected, the di↵erence between the satura- quantitative understanding of the initial con- tion and non-saturation curves is small for ditions of a heavy ion collision as described the smaller-sized J/ (< 20%), which is less in Sec. 3.4.2. It might even shed some light sensitive to saturation e↵ects, but is substan- on the role of glue and thus QCD in the nu- tial for the larger , which is more sensitive clear structure of light nuclei (see Sec. 3.3). to the saturation region. In both cases, the As described above, in di↵ractive DIS, the di↵erence is larger than the statistical errors. virtual photon interacts with the nucleus via In fact, the small errors for di↵ractive pro- a color-neutral exchange, which is dominated duction indicate that this measurement can by two gluons at the lowest order. It is pre- already provide substantial insight into the cisely this two gluon exchange which yields a saturation mechanism after a few weeks of di↵ractive measurement of the gluon density EIC running. Although this measurement in a nucleus. could be already feasible at an EIC with Experimentally the key to the spatial low collision energies, the saturation e↵ects gluon distribution is the measurement of the would be less pronounced due to the larger d /dt distribution. As follows from the op- values of x. For large Q2, the two ratios tical analogy presented in Sec. 3.2.1, the asymptotically approach unity. Fourier-transform of (the square root of) this As explained earlier in Sec. 3.2.1, coher- distribution is the source distribution of the ent di↵ractive events allow one to learn about object probed, i.e., the dipole scattering am- 2 the shape and the degree of “blackness” of plitude N(x, rT ,bT ) on the nucleus with rT 2 2 ⇠ the black disk: this enables one to study the 1/(Q + MV ), where MV is the mass of spatial distribution of gluons in the nucleus. the vector meson [188] (see also the Sidebar Exclusive vector meson production in di↵rac- on page 40). Note that related studies can tive e+A collisions is the cleanest such pro- be conducted in ultra-peripheral collisions of cess, due to the low number of particles in the nuclei, albeit with a limited kinematic reach. final state. This would not only provide us This is discussed in section 3.4.2. with further insight into saturation physics Figure 3.23 shows the d /dt distribution but also constitute a highly important con- for J/ on the left and mesons on the tribution to heavy-ion physics by providing a right. The coherent distribution depends on
85 )
-3 0.3
0.2 < x 10 -6 0.1 EIC science -0
-0.1 → → EIC q(x=10-3,b,Q2 = 4 GeV2) q⇑(x=10-3,b,Q2 = 4 GeV2) √s=44.7 GeV highlights -0.2 √s=44.7−70.7 GeV [0.9, 1.00] 1.5 [0.9, 0.99] s=44.7 141.4 GeV √ − [0.9, 0.97] dx (Quarks + Gluons) (10 -0.3 1 [0.9, 0.94] − ∫ -0.2 0 0.2 [0.8, 0.90] -3 0.5 [0.7, 0.80] ½ - ∫dx (Quarks + Gluons) (10 < x < 1) [0.6, 0.70] [0.5, 0.60] 0 (fm)
y [0.4, 0.50] b [0.3, 0.40] -0.5 [0.2, 0.30] [0.1, 0.20] QS: Matter of Definition and-1 Frame (II) [0.0, 0.10] [0.0, 0.05] DSSV 2014 5 -1.5 [0.0, 0.02] ) 2 Infinite Momentum Frame:
2 g1(x,Q ) [0.0, 0.01] uncertainty -1.5 -1 -0.5 0 0.5 1 1.5 -1.5 -1 -0.5 0 0.5 1 1.5 Q2=10 GeV2 • BFKL (linear QCD): splitting functions ⇒ gluon density grows bx (fm) bx (fm) (x,Q eRHIC pseudo-data 1 • BK (non-linear): recombination of gluons ⇒ gluon density tamed g 0 BFKL: BK adds:
• At Qs: gluon emission balanced by recombination -5 ) 2 T
k ? Unintegrated gluon distribution ~ 1/kT (x, QS: Matter of Definition and Frame (II) φ
depends on kT and x: s = 141.4 GeV s = 63.2 GeV s = 44.7 GeV T √ √ √ k the majority of gluons have -5 -4 -3 -2 -1 Infinite Momentum Frame: 10 10 10 10 10 1 transverse momentum kT ~ QS x BFKL (linear QCD): splitting functions ⇒ gluon density grows (common definition)• max. density max. • BK (non-linear): recombination of gluons ⇒ gluon density tamed know how to ? do physics here BFKL: BK adds: Q αs ∼ 1 ΛQCD s αs << 1 kT 7
• At Qs: gluon emission balanced by recombination ) 2 T k Unintegrated gluon distribution ~ 1/kT (x, φ
depends on kT and x: T k the majority of gluons have transverse momentum kT ~ QS 6/24/21 NNPSS 2021 EIC Lecture 3 (common114 definition) max. density max.
know how to ? do physics here
Q αs ∼ 1 ΛQCD s αs << 1 kT 7 Consensus Study Report on the US based Electron Ion Collider
Summary: The science questions that an EIC will answer are central to completing an understanding of atoms as well as being integral to the agenda of nuclear physics today. In addition, the development of an EIC would advance accelerator science and technology in nuclear science; it would as well benefit other fields of accelerator based science and society, from medicine through materials science to elementary particle physics EIC science: compelling, fundamental and timely
6/24/21 NNPSS 2021 EIC Lecture 3 115 National Academy’s Assessment
Machine Design Parameters: • High luminosity: up to 1033-1034 cm-2sec-1 • a factor ~100-1000 times HERA • Broad range in center-of-mass energy: ~20-100 GeV upgradable to 140 GeV • Polarized beams e-, p, and light ion beams with flexible spin patterns/orientation • Broad range in hadron species: protons…. Uranium EIC science: compelling, fundamental • Up to two detectors well-integrated detector(s) into the and timely machine lattice
6/24/21 NNPSS 2021 EIC Lecture 3 116 117 EIC Physics and the machine parameters
39 ) 10 -1 ep Facilities & Experiments: CM vs. Luminosity vs. Integrated luminosity s JLAB/CEBAF -2 6 12 Past Colliders 1038 Collider Concepts SLAC 1037 Past Fixed Target Ongoing Fixed Target Luminosity (cm 1036 EIC Project
1035
LHeC/HE-LHC FCC-he 34 10 EIC LHeC/HL-LHC EIC 33 10 COMPASS LHeC/CDR HIAF-EIC BCDMS 1032
1031 HERMES NMC HERA (ZEUS/H1)
2 3 10 10 10 s (GeV)
The US EIC with a wide range in √", polarized electron, proton and light nuclear beams and luminosity makes it a unique machine in the world. The EIC Users Group: EICUG.ORG
Formally established in 2016, now we have: ~1300 Ph.D. Members from 34 countries, 254 institutions New members welcome
Map of institution’s locations
EICUG Structures in place and active: EIC UG Steering Committee, Institutional Board, Speaker’s Committee, Election & Nominations Committee
Year long workshops: Yellow Reports for detector design
Annual meetings: Stony Brook (2014), Berkeley (2015), ANL (2016), Trieste (2017), CAU (2018), Paris (2019), FIU (2020), New: Remote (2021), Warsaw (2022) Center for Frontiers in Nuclear Science (at Stony Brook/BNL) EIC2 at Jefferson Laboratory
6/24/21 NNPSS 2021 EIC Lecture 3 118 Physics @ the US EIC beyond the EIC’s core science
New Studies with proton or neutron target: • Impact of precision measurements of unpolarized PDFs at high x/Q2, on LHC-Upgrade results(?) • What role would TMDs in e-p play in W-Production at LHC? Gluon TMDs at low-x! • Heavy quark and quarkonia (c, b quarks) studies with 100-1000 times lumi of HERA • Does polarization of play a role (in all or many of these?) Physics with nucleons and nuclear targets: • Quark Exotica: 4,5,6 quark systems…? Much interest after recent LHCb led results. • Physic of and with jets with EIC as a precision QCD machine: • Internal structure of jets : novel new observables, energy variability, polarization, beam species • Entanglement, entropy, connections to fragmentation, hadronization and confinement • Studies with jets: Jet propagation in nuclei… energy loss in cold QCD medium • Connection to p-A, d-A, A-A at RHIC and LHC • Polarized light nuclei in the EIC Precision electroweak and BSM physics: • Electroweak physics & searches beyond the SM: Parity, charge symmetry, lepton flavor violation 6/24/21 NNPSS 2021 EIC Lecture 3 119 Detector Challenge of the EIC e e’, ν Aim of EIC is 3D nucleon and nuclear structure beyond the longitudinal description. γ, Z,W This makes the requirements for the machine p/A q and detector different from all previous colliders. p remnant “Statistics”=Luminosity × Acceptance
e’ EIC Physics demands ~100% e acceptance for all final state particles (including particles associated with p/A initial ion) Ion remnant is particularly challenging Ø not a usual concern at colliders 1. Scattered electron Ø at EIC integrated from the start with a 2. Particle associated with initial Ion 3. Particle associated with struck quark highly integrated (and complex) detector (or associated gluon) and interaction region scheme.
6/24/21 NNPSS 2021 EIC Lecture 3 Aschenauer/Ent122 Cartoon/Model of the Extended Detector and IR
q EIC physics covers the entire region (backward, central, forward) q Many EIC science processes rely on excellent and fully integrated forward detection scheme Adapted from 2nd Yellow Report Meeting, Detector Working Group p/ion beam e beam
forward Ion final- forward far-forward far-forward far-backward e final- “Central detector”, includes dipole focus quads dipole h-detection h-detection e-detection focus e-endcap, central, and p/ion incl. h quads endcap detectors detection
Low-Q2 Inclusive Structure Functions, GPDs/DVCS, Baryon decay GPDs, spectroscopy TMDs, heavy flavors and jets, tagging, p/K structure tagging, electrons for GPDs diffraction, evaporated n diffraction, high-medium t lowest-t
GEMs Vertex and Tracking detectors, Si/GEMs GEMs Roman Diamond particle identification detectors, Roman pots, Roman pots pots detectors? calorimetry detectors, muon e/g calorim. e/g calorim. ZDCs detectors, etc.
physics examples detector examples 6/24/21 NNPSS 2021 EIC Lecture 3 123 Resulting Experimental Requirements
More and more demanding moving from inclusive to fully exclusive scattering • Inclusive measurements (DIS), required: • Precise scattered electron identification (e.m. calorimetry, e/h PID) and extremely fine resolution in the measurement of its angle (tracking) and energy (calorimetry) • Semi-inclusive measurements (SI-DIS), also required: • excellent hadron identification over a wide momentum and rapidity range (h-PID) • full 2p acceptance for tracking (tracking) and momentum analysis (central magnet) • excellent vertex resolution (low-mass vertex detector) • Exclusive measurements also required: • Tracker with excellent space-point resolution (high resolution vertex) and momentum measurement (tracking), • Jet energy measurements (h calorimetry) • very forward detectors also to detect n and neutral decay products (Roman pots, large acceptance zero-degree calorimetry) • And luminosity control, e and A polarimeters, r-o electronics, DAQ, data handing
EIC Detector Advisory Committee (DAC) Meeting, 28-29 September 2020 S. Dalla Torre (INFN) & T. Horn (CUA)124 6/24/21 NNPSS 2021 EIC Lecture 3 Concept DETECTOR This detector concept was included in the EIC CDR prepared for the CD1 Review
HCal
HCal HCal ECal PID TRD ECal ECal PID TPC Gaseous RICH TRD
Si trackers
125 6/24/21 NNPSS 2021 EIC Lecture 3 Reference Detector – Backward/Forward Detectors
Lesson learned from HERA – ensure low-Q2 coverage Highly Integrated detector system: ~75m 1.Central detector: ~10m Various stage detector to capture forward-going protons 2.Backward electron detection: ~35m and neutrons, and also decay products (D, L). 3.Forward hadron spectrometer: ~40m
far-backward far-forward detectors detectors
6/24/21 NNPSS 2021 EIC Lecture 3 Ent 126 EIC moved forward…. A major step! !"#$%&$'$(#")*%+%,*#"("-,#$.%#"/$'"*$ • !"#$%&&'(&)*+,$-%&(%./$01$2323 • 4!3$!*)*56*.$701$2370 • 89:*$';$#<4,$=.''>?%@*&$A%:9'&%B$C%6'.%:'./$ • =AC$%&+$-C%6 .*%B9D*$#<4$%E$F%.:&*.E
• G$;'.5%B$#<4$F.'H*):$9E$&'I$E*:(F$%:$=AC • =ACJ-B%6 5%&%K*5*&:$L$E)9*&:9E:E$%.*$ I'.>9&K$:'K*:?*.$:'$.*%B9D*$9:$'&$%$;%E:$:95*B9&*M
• 4!7$%&:9)9F%:*+$-(&*$2N1$2327 • 4!2$GFF.'@%B$7!" O(%.:*.$PQ232R$ • 4!R$S"# O(%.:*.$PQ232R$TE:%.:$)'&E:.():9'&U • #<4$4!SG$#%.B/$P9&9E?$S"#O$PQ2320$ • #<4$4!S=$R$%O$PQ$23R2 6/24/21 NNPSS 2021 EIC Lecture 3 128 EIC Project and Experimental Program Credits: Slides in this section are taken from various public presentations by J. Jeck, F. Willeke, R. Ent & E. Aschenauer
Some are minimally modified for compactness by me.
6/24/21 NNPSS 2021 EIC Lecture 3 129 The US Electron Ion Collider
Hadrons up to 275 GeV Ø Existing RHIC complex: Storage (Yellow), injectors (source, booster, AGS) Ø Need few modifications Ø RHIC beam parameters fairly close to those required for EIC@BNL
Electrons up to 18 GeV Ø Storage ring, provides the range sqrt(s) = 20-140 GeV. Beam current limited by RF power of 10 MW Ø Electron beam with variable spin pattern (s) accelerated in on-energy, spin transparent injector (Rapid-Cycling-Synchrotron) with 1-2 Hz cycle frequency Ø Polarized e-source and a 400 MeV s-band injector v Electron storage ring with frequent injection of LINAC in the existing tunnel fresh polarized electron bunches v Hadron storage ring with strong cooling or Design optimized to reach 1034 cm-2sec-1 frequent injection of hadron bunches 6/24/21 NNPSS 2021 EIC Lecture 3 130 Reference Detector – Location
Two possible locations – IP6 and IP8 – for detectors and Interaction Regions.
IP6 is the assumed detector location from project risk view (mainly schedule). • IP8 is also suitable.
Hadron Storage Ring Electron Storage Ring Electron Injector Synchrotron Possible on-energy Hadron injector ring Hadron injector complex
6/24/21 NNPSS 2021 EIC Lecture 3 Aschenauer/Ent 131 p: 41 GeV, 100 to 275 GeV e: 5 GeV to 18 GeV
Large rapidity (-4 < h < 4) coverage Nomenclature à Detect from 2o to 178o… … and far beyond à Many detectors in backward + forward region
low Q2 scattered electrons Main detector = particles from nuclear Bethe-Heitler photons Barrel + breakup, i.e. neutrons, for luminosity scattered protons, and ions Lepton Endcap + from diffractive reactions Hadron Endcap Backward Forward Endcaps critical because of largely asymmetric beam energies (with different beams). Similar large impact on IR/accelerator. 132 6/24/21 NNPSS 2021 EIC Lecture 3 EIC Experimental Equipment Requirements
Any general purpose EIC Detector is complex
Overall detector requirements: q Large rapidity (-4 < h < 4) coverage; and far beyond in especially far- forward detector regions q High precision low mass tracking o small (µ-vertex) and large radius (gaseous-based) tracking
q Electromagnetic and Hadronic Calorimetry o equal coverage of tracking and EM-calorimetry q High performance PID to separate p, K, p on track level o also need good e/p separation for electron-scattering q Large acceptance for diffraction, tagging, neutrons from nuclear breakup: critical for physics program Integration into Interaction o Many ancillary detector integrated in the beam line: low-Q2 Region is critical tagger, Roman Pots, Zero-Degree Calorimeter, …. q High control of systematics o luminosity monitors, electron & hadron Polarimetry
6/24/21 NNPSS 2021 EIC Lecture 3 Ent/Aschenauer133 Reference Detector – technologies
Table from CDR based on Yellow Report initiative
We used the first column as reference detector but also consider alternate detector technologies as options for risk reduction, as the final call comes from the community detector proposals. The context of this was mentioned in CDR Section 8.1 “Realization of the Experimental Equipment in the National and International Context”. 6/24/21 NNPSS 2021 EIC Lecture 3 134 6/24/21 Reference General-Purpose EIC Detector
6.10.07 Magnets Reference detector magnet = 3T, with 3.2 meter bore and 3.84 meter cryostat length
(Hadronic calorimetry also Note: this is NOT the final integrated with iron yoke) reference detector, but many of us use this figure for the talks as it gives an 6.10.06 6.10.05 6.10.04 Particle 6.10.03 easy direct snapshot. Hadronic EM Identification Tracking 135 Calorimetry Calorimetry NNPSS 2021 EIC Lecture 3 Expressions of Interests Received
• 47 Expressions of Interest received • There is clearly large interest in EIC science and experimental equipment o Both domestically among universities and national labs o And international, with many countries represented (Canada, China, Czech, France, India, Italy, Japan, Korea, Poland, UK and institutional EoIs of Chile, Hungary, Mexico, Rumania, and group EoIs with Armenia, Israel, Saudi Arabia and Taiwan as members) • With EIC science still a decade away, impressively many are committed to work on EIC. • ~500 FTEs annually, $50-100M non-DOE in-kind • In-kind contributions suffice to maintain low-risk for a general-purpose EIC detector. • It is clear we need to remain vigilant and follow up to secure in-kind contributions and even argue • if we want to be able to secure a second detector, with crisp arguments on why. • Make the case for collaboration internationally
6/24/21 NNPSS 2021 EIC Lecture 3 136 Pre-proposals è detector collaborations…
• ECCE IP8 or IP6 è EIC Collider Experiment: • Or Hen, Tanja Horn, John Lejoie
• ATHENA è at IP6 • Silvia Dalla Torre, Abhay Deshpande, Yulia Ferlatova, Olga Evdokimov, Barbara Jacak, Alexander Kiselev, Franck Sabatie, Bernd Surrow, • CORE: at IP7 • a COmpact detectoR for the Eic: Charles Hyde, Pavel Nadol-Turonski
• HL-LCM (“IR2”) White Paper: Volker Burkert, Latifa Eloudrihiri, and Marco Contalbrigo, John Arrington, Franck Sabatie, Abhay Deshpande, Richard Milner, Todd Satogata, Xiangdong Ji
6/24/21 NNPSS 2021 EIC Lecture 3 137 ECCE 101
• 77 institutions developing an EIC detector with full energy coverage and an optimized far forward detection region.
• Based on an existing 1.5T solenoid in either EIC interaction regions, ready for the beginning of EIC accelerator operation.
• ECCE will respond to the EIC call for detector proposals, addressing the full range of EIC physics outlined in the NAS study and the Yellow Report, as the EIC project detector (“Detector 1”).
• ECCE shares the vision of the Nuclear Physics community that the EIC science mission is best served by two detectors.
• ECCE is open to all to participate - freedom of choice to also work on other proposals
6/24/21 NNPSS 2021 EIC Lecture 3 138 Ø ATHENA pre-collaboration is open to the whole EICUG community Ø Web-page: https://sites.temple.edu/eicatip6 Ø Mailing lists: https://lists.bnl.gov/mailman/listinfo/ Ø Join EIC@IP6 on Slack: link Ø The coordination committee: Silvia Dalla Torre, Abhay Deshpande, Olga Evdokimov, Yulia Furletova , Barbara Jacak, Alexander Kiselev, Franck Sabatie, Bernd Surrow Ø Institutional board, charter committee, proposal committee, Working Groups for detector and physics in place. Ø 94+ institutions contributing to the effort
Up to 3T magnet
6/24/21 NNPSS 2021 EIC Lecture 3 140 CORE: a COmpact detectoR for the EIC e-endcap h-endcap
CORE is a hermetic general-purpose detector that fulfills the EIC physics requirements. • outlined in the Yellow Report. White Paper, etc.
The compact size has several advantages, including. • higher luminosity for all c.m. energies • reduced cost allowing investment in critical components p/A e
Main systems New 2.5 T solenoid (2.5 m long, 1 m inner radius) Central all-Si tracker (+ GEM in h-endcap) PID: DIRC in barrel, dual-radiator RICH in h-endcap, LGAD TOF in e-endcap EMcal: PWO for h < 0 and W-Shashlyk for h > 0
Hcal and KL-µ (KLM) detectors integrated with the CORE in Geant magnetic flux return of the solenoid P. N a d e l -Turonski 6/24/21 NNPSS 2021 EIC Lecture 3 142 Physics at Low CM-High Lumi IR: A separate detector?
• Aim: to produce a White Paper to highlight the science at the EIC with a high-luminosity at low-CM energy Interaction Region. • DES, SIDIS, Jets, HF, Spectroscopy, various researches with light nuclei • Contact: Volker Burkert, Latifa Elouadrhiri, AD • Conditions from the Call for proposal for the 2nd detector: • D2/IR2 complementary to D1/IR1, physics focus beyond EIC WP, and possibly modified IR2 design (compatible with IR1 and machine operations) Recent machine development and studies • Series of Center for Frontiers In Nuclear Science Possible to get high luminosity by only adjusting st nd rd Workshops: 1 @ CFNS, 2 @ ANL-CFNS, 3 magnetic polarities of near-IR magnets APCTP=CFNS, 4th CNF-CFNS (DC).
6/24/21 NNPSS 2021 EIC Lecture 3 143 Proposed Schedule
Detector 1 needs to be ready by CD4A to help with initial collider operations. This is the 1st (left) CD4A blue band (uncertainty)
Detector 2 ideally should be ready by CD4 (about 2 yrs later, the 2nd blue band on right)
144 6/24/21J. Yeck NNPSS 2021 EIC Lecture 3 Summary: Challenging but EXCITING times ahead EIC Science : enthusiastically supported by NAS & 1300+ (growing) users, 254 institutions and 34 countries EIC Project is a very large one within DOE NP and Office of SC • International partners are significant component of the success: DOE actively pursuing contacts and collaborators • BNL and JLab managements are working together to realize the EIC
EIC Detector: unique in its demanding : IR integration • Encouraged by the international interest: Large Users Group assembled and organized • R&D program absorbed by the Detector Advisory Committee • Yellow report produced a concept of an ideal reference detector
Emerging detector collaborations will realize the promise of EIC 6/24/21 NNPSS 2021 EIC Lecture 3 145 https://www.bnl.gov/newsroom/news.php?a=117399
NNPSS 2021 EIC Lecture 3 6/24/21 146 R. Ent, T. Ullrich, R. Venugopalan Scientific American (2015) Translated into multiple languages A. Deshpande & R. Yoshida June 2019 Translated in to multiple languages
E. Aschenauer R. Ent October 2018
6/24/21 NNPSS 2021 EIC Lecture 3 147 Thank you!
6/24/21 NNPSS 2021 EIC Lecture 3 148