The “Hot” Science of RHIC

Status and Future

Berndt Mueller Brookhaven National Laboratory Associate Laboratory Director for Nuclear and Particle Physics

BSA Board Meeting BNL, 29 March 2013

Friday, April 5, 13 RHIC: A Discovery Machine

Polarized Jet Target (PHOBOS) 12:00 o’clock 10:00 o’clock (BRAHMS) 2:00 o’clock RHIC

PHENIX 8:00 o’clock RF 4:00 o’clock STAR 6:00 o’clock LINAC EBIS NSRL Booster BLIP AGS

Tandems

Friday, April 5, 13 RHIC: A Discovery Machine

Polarized Jet Target (PHOBOS) 12:00 o’clock 10:00 o’clock (BRAHMS) 2:00 o’clock RHIC

PHENIX 8:00 o’clock RF 4:00 o’clock STAR 6:00 o’clock LINAC EBIS NSRL Booster BLIP AGS

Tandems Pioneering

Perfectly liquid quark-gluon plasma; Polarized proton collider

Friday, April 5, 13 RHIC: A Discovery Machine

Polarized Jet Target (PHOBOS) 12:00 o’clock 10:00 o’clock (BRAHMS) 2:00 o’clock RHIC

PHENIX 8:00 o’clock RF 4:00 o’clock STAR 6:00 o’clock LINAC EBIS NSRL Booster BLIP Versatile AGS Wide range of: beam energies ion species polarizations Tandems Pioneering

Perfectly liquid quark-gluon plasma; Polarized proton collider

Friday, April 5, 13 RHIC: A Discovery Machine

Polarized Jet Target (PHOBOS) 12:00 o’clock 10:00 o’clock (BRAHMS) 2:00 o’clock RHIC

PHENIX 8:00 o’clock RF 4:00 o’clock STAR 6:00 o’clock LINAC EBIS NSRL Booster BLIP Versatile AGS Wide range of: beam energies ion species polarizations Tandems Pioneering Productive

>300 refereed papers Perfectly liquid >30k citations quark-gluon plasma; >300 Ph.D.’s in 12 years Polarized proton collider productivity still increasing

Friday, April 5, 13 Detector Collaborations

559 collaborators from 12 countries 540 collaborators from 12 countries

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Friday, April 5, 13 RHIC explores the Phases of Nuclear Matter

LHC: High energy collider at CERN with 13.8 - 27.5 mes higher beam energy: Pb+Pb, p+Pb, p+p collisions only.

FAIR & NICA: Planned European facilies at lower energies. Range of matter explored at RHIC RHIC: Spans largest swath of the phase diagram in preferred collider mode. (location unknown)

Message

RHIC is the perfect facility to explore Atomic nuclei the phases of nuclear (QCD) matter. Matter known before RHIC If RHIC did not exist, someone would have to build it (...but no one could afford it!)

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Friday, April 5, 13 Quantum Chromo-Dynamics (QCD): Fundamental theory of nuclear or “strong” interactions

Nuclei are really complex assemblies of quarks and gluons

➠ Nuclear matter in all its forms is known as “QCD matter”

RHIC has pioneered the laboratory study of condensed QCD maer

RHIC’s results have defined a new subfield of (nuclear) physics.

Scientists, from condensed matter physicists to string theorists, have taken note.

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Friday, April 5, 13 So what has RHIC discovered? Imagine....

...heating a liquid (nuclear matter) until it turns into vapor (nucleon/hadron gas) at approximately 100 billion degrees.

But when you heat it to 20 times this temperature (2 trillion degrees) you find that it suddenly turns into a liquid again, in fact, into the most perfect liquid ever observed.

How is this possible? [We don’t really know.]

What happens at even higher temperatures? [We know.]

Where is the perfect liquid formed? [We almost know.]

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Friday, April 5, 13 RHIC has pioneered the lab study of condensed QCD Maer

distributions and correlations of produced particles kinetic freeze-out QGP Phase Boundary lumpy initial energy density

QGP phase quark and gluon degrees of freedom

Friday, April 5, 13 RHIC has pioneered the lab study of condensed QCD Maer

distributions and correlations of produced particles kinetic freeze-out QGP Phase Boundary lumpy initial energy density

QGP phase quark and gluon degrees of freedom

Initial-state quantum fluctuations propagate into to “macroscopic” final-state fluctuations by hydrodynamic response.

Friday, April 5, 13 RHIC has pioneered the lab study of condensed QCD Maer “Big Bang”

Penetrating probe: photons distributions and Chemical probes: light nuclei correlations of produced particles kinetic Bulk probe: temperature fluctuations freeze-out QGP Phase Boundary lumpy initial energy density

“Little Bang” Penetrating probes: photons, jets ChemicalQGP phase probes: hadrons quark and gluon Bulkdegrees of freedom probe: flow fluctuations

Initial-state quantum fluctuations propagate into to “macroscopic” final-state fluctuations by hydrodynamic response.

Friday, April 5, 13 A “Guinness” record temperature

Exponential fit in pT Exponential fit in pT T = 304 ±51 MeV T = 221 ±23 ±18 MeV

New record “temperature” measured at LHC: Corresponds to initial temperature: Tinit ≥ 300 MeV TLHC = 1.37 TRHIC

Tinit ≥ 4 trillion degrees Tinit ≥ 5.5 trillion degrees

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Friday, April 5, 13 Measuring “fluidity”

Viscosity (η) measures how well a fluid responds to variations in the uniformity of flow.

Quantum physics dictates that viscosity cannot be zero.

A dimensionless measure of perfect fluidity is η/s, which cannot be less than 1/4π ≈ 0.08.

The RHIC data indicate that QCD matter has η/s ≈ 0.12.

No other liquid is known with such a low value.

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Friday, April 5, 13 Anisotropic flow

Reaction z plane

Only matter in the overlap area gets compressed and heated y

x

dN ⎛ ⎞ 2π = N0 ⎜1+ 2∑vn (pT ,η)cosn(φ −ψ n (pT ,η))⎟ dφ ⎝ n ⎠

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Friday, April 5, 13 QCD Matter at RHIC is most “perfect”

Initial density distribution

RHIC

B. Schenke (BNL - Goldhaber Fellow)

(η/s)RHIC ≈ 0.6 (η/s)LHC

A study of the opacity of the matter LHC to energetic quarks (jets) confirms this conclusion:

QCD matter at RHIC is less transparent by the same factor 0.6.

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Friday, April 5, 13 The Black Hole connection

Dynamics of hot QCD matter can be mathematically mapped on black hole dynamics in 4 dimensions

BH swallowing matter

Perfect fluid hydrodynamics

Formation of hot QCD matter at RHIC is similar to formation of a black hole, tied to information loss.

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Friday, April 5, 13 The Black Hole connection II

BH horizon acts like a perfect liquid; BH destroys information as fast as possible. Why and how?

Study the dynamics of elements of empty space: Strings in string theory; or polyhedra in loop quantum gravity

Chris Coleman-Smith Dynamics of tetrahedron (Duke grad. student) is regular and periodic

Dynamics of pentahedron is irregular and chaotic

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Friday, April 5, 13 RHIC explores the most perfectly liquid, most opaque form of the quark-gluon plasma.

This discovery connects to the deepest properties of space and time

New upgrades will make RHIC even more powerful:

Vertex detectors will identify heavy quarks

Electron cooling will increase luminosity

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Friday, April 5, 13 Where is the “Perfect” Liquid formed?

Probing the QCD Phase-Diagram STAR Preliminary Stat. errors only 7.7GeV 11.5GeV • RHIC Beam Energy Scan: use beam Not feed-down corrected 10 19.6GeV energy as control parameter to vary initial 27GeV 39GeV temperature and chemical potential 62.4GeV opacity 200GeV STAR(2003) • Beam energy range in area of relevance is 2.76TeV ALICE

unique to RHIC! (0-5%/60-80%) 1 CP • BES-II will deliver precision required to R N search for signatures of the CEP part jet suppression 10-1 0 1 2 3 4 5 6 7 8 9 10 p (GeV/c) T

Net-proton 0.4

1.1 BES II Projected Errors 1 2 σ

κ 0.9

0.8 ϕ-meson flow 0.7 STAR Preliminary 5 6 7 10 20 30 100 200

sNN 15 (GeV)

Friday, April 5, 13 RHIC: Science Goals for the Next Decade

Quantify properties of the QGP by measuring heavy quarks and features of the QCD phase diagram as functions of temperature and net quark density.

LHC Experiments Exploit new discovery potential

Full-energy RHIC Experiments in searches for a QCD critical point and for the nature and influence of quantum fluctuations in initial densities and gluon vacuum excitations.

~155 MeV

Continue explorations of the role of soft gluons in cold nuclear matter (gluon saturation, gluon and sea quark contributions to proton spin). Precursor to eRHIC program. Search for a QCD Critical endpoint via low-energy scan in RHIC-II era Caveat: Budget constraints make a deliberate execution of a decadal program of scientific inquiry challenging

Friday, April 5, 13 EIC: An electron microscope for QCD matter

eRHIC

arXiv:1212.1701 Friday, April 5, 13 eRHIC will be a QCD laboratory

Gluon structure of proton

Microscopic processes High density phase of studied in bulk at RHIC gluon matter (CGC)

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Friday, April 5, 13 From RHIC to e-RHIC

Polarized New e-gun detector GeV

Linac Beam dump

Linac 2.45 1 to 2.45 Phase II only GeV 5.50 GeV Cost-effective 4 local loops eRHIC for phase I Coherent e-cooler 10.4 GeV

15.3 GeV 6 passes are needed for 30 GeV 20.2 GeV

25.1 GeV Phase I requires

30 GeV ePHENIX 30.0 GeV only 1 to 2 passes

100 m

eSTAR 30 GeV

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Friday, April 5, 13 Summary

§ If RHIC did not exist, it would need to be built § $2B infrastructure uniquely capable to explore QCD matter in the perfect liquid domain § RHIC sits at the sweet spot: most liquid & opaque QGP § The discovery potential of RHIC is undiminished § RHIC-2 exists now -- on track to RHIC-3 in 2017/18 § RHIC’s path toward eRHIC is clearly delineated and provides for a cost-effective realization of the EIC § We are developing the technical and scientific case for eRHIC to be presented at the next long range plan § RHIC & eRHIC can ensure U.S. preeminence in research on QCD for the next 2-3 decades

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Friday, April 5, 13