Heavy Ion Physics and Electron Ion Colliders W

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Heavy Ion Physics and Electron Ion Colliders W. A. Horowitz The Ohio State University

Heavy Ion Physics and Electron Ion Colliders W. A. Horowitz The Ohio State University July 29, 2010 With many thanks to Brian Cole, Miklos Gyulassy, Ulrich Heinz, Jiangyong Jia, and Yuri Kovchegov 10/3/2020 EIC at CUA 1

Two Major Discoveries at RHIC • Huge low-p. T v 2 • Huge high-p.

Two Major Discoveries at RHIC • Huge low-p. T v 2 • Huge high-p. T suppression 20 -30% Y. Akiba for the PHENIX collaboration, PLB 630, 2005 Hirano et al. , PRC 77, 2008 – p 0 RAA described by p. QCD – Described by hydro with low viscosity 10/3/2020 EIC at CUA 2

Why Are These Interesting? • Want to characterize the QGP – Can’t directly measure

Why Are These Interesting? • Want to characterize the QGP – Can’t directly measure • Use indirect tools • Is QGP: – Most perfect fluid ever created/studied? – Can one use strongly and/or weakly coupled field theory methods? • p. QCD vs. Ad. S/CFT • Enormous influence of geometry 10/3/2020 EIC at CUA 3

QCD: Theory of the Strong Force • Running as – -b-fcn • SU(Nc =

QCD: Theory of the Strong Force • Running as – -b-fcn • SU(Nc = 3) PDG ALEPH, PLB 284, (1992) • Nf(E) – Nf(RHIC) ≈ 2. 5 Griffiths Particle Physics 10/3/2020 EIC at CUA 4

What are We Interested In? • Measure manybody physics of strong force • Test

What are We Interested In? • Measure manybody physics of strong force • Test & understand theory of manybody non-Abelian fields Long Range Plan, 2008 10/3/2020 EIC at CUA 5

HI Collisions Tool for Strong Force Physics Study • Want a consistent picture of

HI Collisions Tool for Strong Force Physics Study • Want a consistent picture of matter produced in HI collisions – Then, want to quantify the properties of the produced matter 10/3/2020 EIC at CUA 6

Spacetime Evolution of a HI Collision • At RHIC t=-¥ t=0 Initial State Initial

Spacetime Evolution of a HI Collision • At RHIC t=-¥ t=0 Initial State Initial Overlap t = 1 fm/c Thermalization t = 3 fm/c QGP t=+¥ t = 4 fm/c Hadronization Hadron Gas – Nontrivial to learn about QGP through HIC 10/3/2020 EIC at CUA 7

Methods of QCD Calculation I: Lattice Long Range Plan, 2008 • All momenta •

Methods of QCD Calculation I: Lattice Long Range Plan, 2008 • All momenta • Euclidean correlators Kaczmarek and Zantow, PRD 71 (2005) 10/3/2020 Davies et al. (HPQCD), PRL 92 (2004) EIC at CUA 8

Methods of QCD Calculation II: p. QCD (perturbative QCD) Jäger et al. , PRD

Methods of QCD Calculation II: p. QCD (perturbative QCD) Jäger et al. , PRD 67 (2003) 10/3/2020 d’Enterria, 0902. 2011 • Any quantity • Small coupling (large momenta only) EIC at CUA 9

Methods III: Ad. S/CFT Maldacena conjecture: SYM in d IIB in d+1 Gubser, QM

Methods III: Ad. S/CFT Maldacena conjecture: SYM in d IIB in d+1 Gubser, QM 09 • All quantities • Nc → ∞ SYM, not QCD • Probably not good approx. for p+p; maybe A+A? • Applicable to condensed matter systems? 10/3/2020 EIC at CUA 10

Geometry and Flow • Qualitative picture: Anisotropic initial geometry => anisotropic flow 10/3/2020 EIC

Geometry and Flow • Qualitative picture: Anisotropic initial geometry => anisotropic flow 10/3/2020 EIC at CUA 11

Hydrodynamics and v 2 • Hydro – Early therm. – ¶m. Tmn = 0

Hydrodynamics and v 2 • Hydro – Early therm. – ¶m. Tmn = 0 – Equation of State (EOS) – Ideal: h/s = 0 – v 2: 2 nd Fourier coef of particle spectrum: 10/3/2020 EIC at CUA 12

Viscous Hydrodynamics • Viscosity reduces elliptic flow – Naive p. QCD => h/s ~

Viscous Hydrodynamics • Viscosity reduces elliptic flow – Naive p. QCD => h/s ~ 1 – Naive Ad. S/CFT => h/s ~ 1/4 p Shear Viscosity, Wikipedia 10/3/2020 => Strongly coupled. EICmedium? at CUA Luzum and Romatschke, Phys. Rev. C 78: 034915, 2008 13

Geometry in Viscosity Extraction • Poorly constrained initial geom => 100% uncertainty in viscosity

Geometry in Viscosity Extraction • Poorly constrained initial geom => 100% uncertainty in viscosity T Hirano, et al. , Phys. Lett. B 636: 299 -304, 2006 – KLN CGC breaks down at edge of nuclear overlap 10/3/2020 • Whole effect comes from edges! • Experimental constraints needed! EIC at CUA 14

Why High-p. T Particles? • Tomography in medicine One can learn a lot from

Why High-p. T Particles? • Tomography in medicine One can learn a lot from a single probe… and even more with multiple probes PET Scan 10/3/2020 http: //www. fas. org/irp/imint/docs/rst/Intro/P art 2_26 d. html EIC at CUA SPECT-CT Scan uses internal g photons and external X-rays 15

Tomography in QGP • Requires wellcontrolled theory of: – production of rare, highp. T

Tomography in QGP • Requires wellcontrolled theory of: – production of rare, highp. T probes p. T f , g, e- • g, u, d, s, c, b – in-medium E-loss – hadronization • Requires precision measurements of decay fragments 10/3/2020 EIC at CUA Invert attenuation pattern => measure medium properties 16

QGP Energy Loss • Learn about E-loss mechanism – Most direct probe of DOF

QGP Energy Loss • Learn about E-loss mechanism – Most direct probe of DOF p. QCD Picture Ad. S/CFT Picture 10/3/2020 EIC at CUA 17

High-p. T Observables Naively: if medium has no effect, then RAA = 1 Common

High-p. T Observables Naively: if medium has no effect, then RAA = 1 Common variables used are transverse momentum, p. T, and angle with respect to the reaction plane, f , g, e- f Fourier expand RAA: 10/3/2020 p. T EIC at CUA 18

p. QCD Rad Picture • Bremsstrahlung Radiation – Weakly-coupled plasma • Medium organizes into

p. QCD Rad Picture • Bremsstrahlung Radiation – Weakly-coupled plasma • Medium organizes into Debye-screened centers – T ~ 250 Me. V, g ~ 2 • m ~ g. T ~ 0. 5 Ge. V • lmfp ~ 1/g 2 T ~ 1 fm • RAu ~ 6 fm – 1/m << lmfp << L Gyulassy, Levai, and Vitev, NPB 571 (200) • mult. coh. em. – Bethe-Heitler – LPM dp. T/dt ~ -LT 3 log(p. T/Mq) 10/3/2020 EIC at CUA dp. T/dt ~ -(T 3/Mq 2) p. T 19

p. QCD Success at RHIC: (circa 2005) Y. Akiba for the PHENIX collaboration, PLB

p. QCD Success at RHIC: (circa 2005) Y. Akiba for the PHENIX collaboration, PLB 630, 2005 – Consistency: RAA(h)~RAA(p) – Null Control: RAA(g)~1 – GLV Prediction: Theory~Data for reasonable fixed L~5 fm and d. Ng/dy~d. Np/dy 10/3/2020 EIC at CUA 20

p. QCD Seemingly Inadequate • Lack of even qualitative understanding p 0 v 2

p. QCD Seemingly Inadequate • Lack of even qualitative understanding p 0 v 2 – p 0, h, g RAA well described, BUT – e- RAA, v 2 is not, even with elastic loss PHENIX p 0 9. 5 Ge. V! W HD G 30 -40% Centrality p 0 RAA Wicks et al. 10/3/2020 p. QCD assumes M << E: b E-loss not under control EIC at CUA Death of p. QCD at RHIC? 21

Jets in Ad. S/CFT • Model heavy quark jet energy loss by embedding string

Jets in Ad. S/CFT • Model heavy quark jet energy loss by embedding string in Ad. S space dp. T/dt = - m p. T m = pl 1/2 T 2/2 Mq – Similar to Bethe-Heitler dp. T/dt ~ -(T 3/Mq 2) p. T J Friess, S Gubser, G Michalogiorgakis, S Pufu, Phys Rev D 75 (2007) – Very different from LPM dp. T/dt ~ -LT 3 log(p. T/Mq) 10/3/2020 EIC at CUA 22

Compared to Data • String drag: qualitative agreement WAH, Ph. D Thesis 10/3/2020 EIC

Compared to Data • String drag: qualitative agreement WAH, Ph. D Thesis 10/3/2020 EIC at CUA 23

Light Quark and Gluon E-Loss WAH, in preparation DLgtherm ~ E 1/3 DLqtherm ~

Light Quark and Gluon E-Loss WAH, in preparation DLgtherm ~ E 1/3 DLqtherm ~ (2 E)1/3 10/3/2020 EIC at CUA Renk and Marquet, PLB 685, 2010 24

High-p. T and HIC Spacetime Evolution 10/3/2020 EIC at CUA 25

High-p. T and HIC Spacetime Evolution 10/3/2020 EIC at CUA 25

Geometry and High-p. T v 2 • Effects of geom. on, e. g. v

Geometry and High-p. T v 2 • Effects of geom. on, e. g. v 2, might be quite large – CGC vs. KLN and rotating RP – Effect not large enough WAH and J Jia, in preparation Need experimental constraints on initial geometry! 10/3/2020 EIC at CUA 26

Conclusions • Tantalizing physics discoveries at RHIC – Large low-p. T v 2 •

Conclusions • Tantalizing physics discoveries at RHIC – Large low-p. T v 2 • nearly perfect strongly coupled fluid – Large high-p. T suppression • weakly coupled quasiparticle plasma • Statement that QGP at RHIC is strongly coupled nearly ideal fluid depends sensitively on the IC – Diffuse medium and Ad. S/CFT – Sharp medium and p. QCD • Exciting e. RHIC and LHe. C HI physics opportunities – Knowledge of r (b) extremely important for quantitative (qualitative? ) HI physics 10/3/2020 EIC at CUA 27