13-Jan-07 RHIC II Upgrade and Science Program QCD Town Meeting Rutgers, NJ W.A. Zajc Columbia...

13-Jan-07

RHIC II Upgrade and Science Program

QCD Town MeetingRutgers, NJ

W.A. ZajcColumbia University

13-Jan-07

OutlineOutline

A capsule history of the initial discovery phase of RHIC operations

Compelling scientific questions

for RHIC II

The elements of RHIC II

The primacy of QCD

13-Jan-07

The Plan c. 2000The Plan c. 2000 Use RHIC’s unprecedented capabilities

Large √s Access to reliable pQCD probes Clear separation of valence baryon number and glue

Polarized p+p collisions

Two small detectors, two large detectors Complementary capabilities Small detectors envisioned to have 3-5 year

lifetime Large detectors ~ facilities

Major capital investments Longer lifetimes Potential for upgrades in response to discoveries

13-Jan-07

Since Then…Since Then… Accelerator complex

Routine operation at 2-4 x design luminosity (Au+Au) Extraordinary variety of operational modes

Species: Au+Au, d+Au, Cu+Cu, p+p Energies: 22 GeV (Au+Au, Cu+Cu, p), 56 GeV (Au+Au),

62 GeV (Au+Au,Cu+Cu, p+p) , 130 GeV (Au+Au), 200 GeV (Au+Au, Cu+Cu, d+Au, p+p), 410 GeV (p), 500 GeV (p)

Experiments Worked Collaborations worked

Science 160 refereed publications, 89(!) PRL’s Major discoveries

Future Demonstrated ability to upgrade Key science questions identified Accelerator and experimental upgrade program

developed to perform that science

13-Jan-07

A Non-Surprise: RHIC Energy Reduces Scale A Non-Surprise: RHIC Energy Reduces Scale DependenceDependence

The high √s of RHIC makes contact with rigorous pQCD calculations minimizes “scale dependence”

A huge advantage in Spin program Providing calibrated probes in A+A

PHENIX p+p 0 + X-NLO pQCD F. Aversa et al. Nucl. Phys. B327, 105 (1989)

-CTEQ5M pdf/PKK frag

-Scales =pT/2, pT, 2pT

=pT/2

=2pT

13-Jan-07

RHIC Spin SuccessesRHIC Spin Successes

BRAHMS & PP2PP (p)

STAR (p)

PHENIX (p)

AGS

LINACBOOSTER

Pol. Proton Source500 A, 300 s

Spin Rotators

Partial Siberian Snake

Siberian Snakes

200 MeV Polarimeter AGS Internal PolarimeterRf Dipoles

RHIC pC PolarimetersAbsolute Polarimeter (H jet)

2 1011 Pol. Protons / Bunch = 20 mm mrad

RHIC accelerates heavy ions to 100 GeV/A and polarized protons to 250 GeV

Achieved 60-65% polarization during RHIC Run-6 !

GeVs

L

50050

onPolarizati70%

cms102 2132max

13-Jan-07

Our First Hard Look Our First Hard Look

“Standard” value of g from pre-RHIC DIS data

Assuming g = 0

(x)g-(x)gΔg(x) -

13-Jan-07

RHIC’s Two RHIC’s Two MajorMajor Discoveries Discoveries Discovery of

strong “elliptic” flow: Elliptic flow in Au + Au

collisions at √sNN= 130 GeV, STAR Collaboration, (K.H. Ackermann et al.). Phys.Rev.Lett.86:402-407,2001

307 citations

Discovery of “jet quenching” Suppression of hadrons with

large transverse momentum in central Au+Au collisions at √sNN = 130 GeV, PHENIX Collaboration (K. Adcox et al.), Phys.Rev.Lett.88:022301,2002

357 citations

Flo

w s

tre

ng

thS

up

pre

sio

n F

acto

r

13-Jan-07

Thehottest densestmatter

ever studied in the laboratoryflows

as a (nearly) perfect fluidwith systematic patterns consistent with

quark degrees of freedom

and a viscosity to entropy density ratio lower (?) than any other known fluid with a value near (?) a conjectured

quantum bound

To SummarizeTo Summarize

T ~ 200- 400 MeV

i ~ 30-60 o

(thermal yields)

large “elliptic” flow

/s ~ (2-3) /4

valence quark scaling

13-Jan-07

See See SS Run Run The low viscosity is

“understood” as a result of Short mfp’s Large cross sections Strong coupling

near the phase “transition”

(really cross-over) Small /s sQGP

Strongly-coupledQuark-Gluon “Plasma”

“Perfect liquid"

We need to understand s when it is large!

“The strong coupling constant at low Q2”, A. Deur, hep-ph/0509188

“Perturbative QCD theory (includes our knowledge of s )”,

Y. Dokshitzer, hep-ph/9812252

13-Jan-07

How Perfect is “Perfect” ?How Perfect is “Perfect” ? All “realistic” hydrodynamic calculations for RHIC

fluids to date have assumed zero viscosity Viscosity= 0 “perfect fluid” But there is a (conjectured) quantum limit: “A Viscosity

Bound Conjecture”, P. Kovtun, D.T. Son, A.O. Starinets, hep-th/0405231

Where do “ordinary” fluids sit wrt this limit?

RHIC “fluid” mightbe at ~2-3 on this scale (!)

T=10T=101212 KK

sDensityEntropy

4

)(4

13-Jan-07

RHIC FutureRHIC FutureThe fundamental matter created at RHIC compels further

investigation How imperfect is its “perfection” ? How does it respond to truly heavy probes? (charm, bottom) Can even higher energy densities be achieved in U+U collisions? Is there a critical point in the QCD phase diagram ?

All of this (and more) is addressed by RHIC II: EBIS Electron Beam Ion Source to extend ranges of species Upgrades to STAR and PHENIX

Vertex detectors for precision heavy flavor tomography Increased coverage in forward regions Increased rate and triggering capabilities

x10 Luminosity increase by electron coolingx10 Luminosity increase by electron cooling Efficient access to the rare probes that have proven so incisive

in the first generation discovery measurements at RHIC.

13-Jan-07

Gold collisions (100 GeV/n x 100 GeV/n): no e-cooling with e-cooling

Ave. store luminosity [1026 cm-2 s-1] 8 70

Pol. Proton Collision (250 GeV x 250 GeV):

Ave. store luminosity [1032 cm-2 s-1] 1.5 5.0

Ongoing experiments and simulations in progress

RHIC II Luminosity Enhancement via e-RHIC II Luminosity Enhancement via e-CoolingCooling

13-Jan-07

Detector Upgrades Detector Upgrades

STAR PHENIX

forward meson spectrometerDAQ & TPC electronicsfull ToF barrelheavy flavor trackerbarrel silicon trackerforward tracker

Key:Completedongoingproposal submittedproposal in preparation

hadron blind detectormuon Triggersilicon vertex barrel (VTX)forward silicon forward EM calorimeter

Ongoing effort with projects in different stages

13-Jan-07

Fundamental Questions for Fundamental Questions for RHIC IIRHIC II

What are the phases of QCD Matter?

What is the wave-function of a heavy nucleus?

What is the wave-function of the proton?

What is the nature of non-equilibrium processes in a fundamental theory?

13-Jan-07

Compelling Physics of RHIC IICompelling Physics of RHIC II

High T QCD (A+A, d+A, and p+p): Electromagnetic radiation (e+epair continuum) Heavy flavor (c- and b-production) Jet tomography (jet-jet and -jet) Quarkonium ( J/, ’ , c and (1s),(2s),(3s) )

Spin structure of the nucleon: Quark spin structure q/q (W-production) Gluon spin structure g/g (heavy flavor and -jet

correlations)

Low x phenomena gluon saturation in nuclei

(particle production at forward rapidity)

Provide key measurements so far inaccessible at RHIC in three broad areas:

requires highestAA luminosity

All measurements require upgrades of detectors and/or RHIC luminosity

“Low x” “forward measurements”

13-Jan-07

What is the wave-function

of the proton?

13-Jan-07

Spin Goals for RHIC IISpin Goals for RHIC II Use the increased luminosity

to achieve a precision in g comparable to (at least) present knowledgeof :

Asymptotic expectation ( X. Ji, J. Tang, P. Hoodbhoy, Phys.Rev.Lett. 76, 740 (1996) )

Cleanest probe for g(x) : Prompt-photon production ( -jet, to determine parton kinematics ) Also the rarest, clearly benefits from increased luminosity RHIC II samples of ~ 1 fb -1 allow

Systematic cross checks (e.g., same x measured at variety of Q2 ) Extension to small x regions (using forward upgrades)

gq

proton

LgL 2

1

2

1

0.30.1Δq(x)dxq

ΔΣ

}

0.18163n

3n

2

1

f

f

}

163n

16

2

10.32

f

13-Jan-07

Sea quark/antiquark polarization Flavor decomposition likely to be

key to understanding small value of .

Major tool: Parity-violatingsingle-spin asymmetry AL from W ± decays.

Requires ~ 1 fb-1 data sets RHIC II luminosity Detector upgrades

Ultimate goal: charm-tagged W’s

Transverse spin measurements To study transversity To understand role of quark angular momentum To extract Sivers functions over unparalled range of x

and Q2 .

Spin Goals for RHIC II (Cont’d)Spin Goals for RHIC II (Cont’d)

13-Jan-07

What is the wave-function

of a heavy nucleus?

13-Jan-07

Rapidity Density600 1200

PHOBOS Central Au+Au (200 GeV)

Compilation by K. EskolaColor Glass

Kharzeev & Levin, Phys. Lett. B523 (2001) 79

Data: PHOBOS,Phys. Rev. Lett. 87, 102303 (2001)

From Eskola, QM 2000

A Surprise: RHIC Multiplicities Are A Surprise: RHIC Multiplicities Are “Low”“Low” Low, that is, compared to

pre-data predictions of “cascading partons”

Consistent with predictions based on gluon saturation :

13-Jan-07

AssertionAssertion In these complicated events, we have

(a posteriori ) control over the event geometry:

Degree of overlap Number of (nucleon) participants NPart

Orientation with respect to overlapReaction

Reaction

PlanePlane

““Central”Central” ““Peripheral”Peripheral”

23

dN/d

/ .5N

part

Saturation Saturation Running of Running of SS

)Part2

2S

2SSPart

CH log(N~)Λ

Qlog(~

)(Qα

1~

N

N

NPart

13-Jan-07

Fundamental Fields in NucleiFundamental Fields in Nuclei Nucleus increases saturation momentum scale QS 2 ~

(A/x)1/3

Occupation numbers ~ 1 / S(QS) > 1 This is the condition

for ~ classical fields: That is:

Quasi-classical states of the gluon field may be explored at low x in a nucleus

Exploration tools: Near-term: d+A collisions (RHIC RHIC II) Long-term: Electron-ion Collider

Goal: To understand

the wave-functionof a heavy nucleus

13-Jan-07

Relevance to Heavy Ion Relevance to Heavy Ion CollisionsCollisions

Lesson from RHIC:A+A collisionsare very efficientin translating Initial gluon state

Strong shadowing? Saturated gluons? Color Glass

Condensate?

intoFinal thermal state

It is difficult to understand this efficiency without invoking some form of dense gluonic initial state

We need to measure rather than invoke

13-Jan-07

What are the phases of QCD Matter?

What is the nature of non-equilibrium processes

in a fundamental theory?

13-Jan-07

Understanding the Understanding the MediumMedium Energy loss in a fluid:

☑ Jets travel faster than the speed of sound in the medium.

☑ While depositing energy via interactions with same

QCD “sonic boom” or “Mach cone”

To be expected in a dense fluid which is strongly-coupled

13-Jan-07

Observation of Mach Cone?Observation of Mach Cone? Seen in di-hadron correlation functions in : Modifications to di-jet hadron pair correlations in Au+Au

collisions at √sNN = 200 GeV, (S.S. Adler et al.), Phys.Rev.Lett.97:052301,2006

Sensitive to Speed of

sound Equation

of state

13-Jan-07

The Ultimate Calibrated ProbeThe Ultimate Calibrated Probe Extend the di-hadron correlations to

(direct) photon-hadron correlations Photons emerge directly, unaffected by the medium A clean measure of initial (hard) Q2

Heavy ion analog to tagged photon beam Current state of the art:

A potentially beautiful technique, desperately in need of RHIC II luminosities !

as compared

to

-h h-h

13-Jan-07

Heavy Flavor at RHIC IIHeavy Flavor at RHIC II Because the u, d, (s) current masses are small compared to T

Properties of the medium are(at zero baryon number)uniquely determined by T

But “introducing” heavy flavor establishes a new scale: Mc ~ 1.3 GeV Mb ~ 5.0 GeV

with associated length scales 1 / Mc ~ 0.15 fm 1 / Mb ~ 0.04 fm Flavor tagged jets to measure

Mach cones, heavy quark energy loss

Bohr radii (onium): J/ ~ 0.29 fm ~ 0.13 fm “Onium” spectroscopy

to measure plasma screening lengths

Measurements of such essential medium properties using rare probes becomes possible via RHIC II luminosities and the detector upgrades

RHICF

low

str

eng

th

13-Jan-07

The Promise of Heavy FlavorThe Promise of Heavy Flavor Present measurements

rely on detection of e’s, ’sfrom semi-leptonic decayof heavy flavor Little or no ability to determine

relative contributions of charm versus bottom

But recent results for Energy loss: RAA(pT) Flow : v2 (pT)

Strongly suggest

Similar estimates obtained from Light quark flow PT fluctuations

4)32(~

s

“Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √sNN = 200 GeV”, A. Adare et al., submitted to PRL, nucl-ex/0611018

“What do elliptic flow measurements tell us about the matter created in the little bang at RHIC?”, R. Lacey and A. Taranenko, nucl-ex/0610029

“Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions”, S. Gavin and M. Abdel-Aziz, nucl-th/0606061

13-Jan-07

Water Water RHIC RHIC Water Water RHIC RHIC The search for QCD phase transition of course

was informed by analogy to ordinary matter Results from RHIC are now “flowing” back to

ordinary matter

“On the Strongly-Interacting Low-Viscosity Matter Created in Relativistic Nuclear Collisions”,L.P. Csernai, J.I. Kapusta and L.D. McLerran, Phys.Rev.Lett.97:152303,2006, nucl-th/0604032

/

s

13-Jan-07

Is There a QCD Critical Point?Is There a QCD Critical Point? Here the analogy with phase transitions

in ordinary matter breaks down: Recall “ Properties of the medium are

(at zero baryon number)uniquely determined by T ”

Pressure = P(T) can’t vary independently(unlike water)

But if baryon number is non-zero (intensive order parameter) baryon chemical potential B :

To increase B : Lower collision energy Raise atomic mass

Both part of RHIC II

13-Jan-07

EBIS StatusEBIS Status EBIS Electron Beam Ion Source

Replaces tandems (thereby avoiding ~$9 M reliability investment)

Extends range of species (polarized 3He, noble elements, uranium )

Approved for construction CD-1 obtained $19.4M cost

($4.5M NASA) 3.5 yr schedule

FY06-09

New Physics!

(Next slide)

13-Jan-07

U+U collisionsU+U collisions Static deformation provides a way to vary the

‘other’ order parameter (baryon chemical potential B )

13-Jan-07

RHIC’s Energy Range Ideal For The RHIC’s Energy Range Ideal For The HuntHunt

There is considerable uncertainty in the location of the QCD critical point

RHIC RHIC II can make major advances on the “other” QCD front: U+U beams Comprehensive

detectors Collider superb control of systematics when changing √s Major importance when varying √sNN from 5 to 200 GeV !

RHIC II will be the ideal facility for systematically exploring the major region of the QCD phase diagram.

13-Jan-07

Heavy Ions at the LHCHeavy Ions at the LHC How could we not choose to investigate “QGP” at

every opportunity? LHC offers unparalleled

increase in √s Will this too create a

strongly-coupled fluid?

Active pursuit via Dedicated experiment (ALICE) Targeted studies (CMS,

ATLAS)

13-Jan-07

Heavy ion collisions at the LHC could reveal entirely new phenomena.

With RHIC II and LHC together we explore deconfined QCD matter over an unprecedented range …

With RHIC II e-cooling, the integrated luminosity per year is 36x larger at RHIC than LHC for heavy ions. From yesterday (Urs Wiedemann):

“The properties of the hot and dense QCD matter produced at the LHC may differ from those produced at RHIC. We can state already now that testing QCD evolution of properties of hot and dense QCD matter is of fundamental interest and is experimentally testable in an interplay of RHIC and LHC… Knowledge about (rare hard high-pT) probes at RHIC can be improved significantly with a luminosity upgrade, which thus could enhance the interplay between RHIC and LHC significantly (in particular if operational during the LHC discovery era).”

RHIC II will continue the demonstrated RHIC capabilities Precision probes Extended data runs Wide variety of beams and energies.

log

1/x

RHIC II and LHCRHIC II and LHC

13-Jan-07

From Urs Wiedemann From Urs Wiedemann (yesterday)(yesterday)

1. Results from the LHC heavy ion run will provide substantial novel tests for the key dynamical ideas (hydrodynamic behavior, hard parton propagation in matter, saturation) developed in the context of the RHIC heavy ion program. Consequence:

Any theory initiative (even if it aims primarily at meeting the challenges of the RHIC heavy ion program), must aim at an unbiased use of all experimental constraints. The most successful theory efforts will work towards a phenomenological framework testable in the entire energy range spanning RHIC and LHC.

2. The properties of the hot and dense QCD matter produced at the LHC may differ from those produced at RHIC. We can state already now that testing QCD evolution of properties of hot and dense QCD matter is of fundamental interest and is experimentally testable in an interplay of RHIC and LHC. Consequence:

We should recognize this novel opportunity. Rare hard high-pt probes provide the most versatile class of tools for characterizing properties of matter. Knowledge about these probes at RHIC can be improved significantly with a luminosity upgrade, which thus could enhance the interplay between RHIC and LHC significantly (in particular if operational during the LHC discovery era).

13-Jan-07

Long Term Timeline of Heavy Ion Long Term Timeline of Heavy Ion FacilitiesFacilities

2006 2012

RHIC

2009

LHC

FAIRPhase III: Heavy ion physics

QCD Laboratory at BNL

PHENIX & STAR upgrades

electron cooling “RHIC II”

electron injector/ring “e RHIC”

2015

Vertex tracking, large acceptance, rate capabilities

13-Jan-07

RHIC and RHIC II in World RHIC and RHIC II in World ContextContext

: 2009

: 2000RHIC II

: 2012

13-Jan-07

New DimensionsNew Dimensions Expanding our theoretical tools

Perturbative QCD (pQCD) for understanding jet quenching Lattice QCD (LQCD) for calculating static properties (s, ) Hydrodynamics as zero-mean-free-path limit of strong

coupling AdS/CFT for calculating static and dynamic properties of

strongly-coupled gauge theories Both sides of this equation

were calculated using black hole physics (in 5 dimensions)

RHICRHIC DensityEntropyityVis )(4

)cos(

Color Screening

cc

MULTIPLICITY

Entropy Black Hole Area

DISSIPATION

Viscosity Graviton

Absorption

13-Jan-07

New Dimensions in RHIC PhysicsNew Dimensions in RHIC Physics “The stress tensor of a quark moving through N=4

thermal plasma”, J.J. Friess et al., hep-th/0607022

Our 4-d Our 4-d worlworl

dd

String String theorist’theorist’

s 5-d s 5-d worldworld

The stuff The stuff formerly formerly known as QGPknown as QGP

Heavy Heavy quark quark

moving moving through through

the the mediummedium

Energy loss Energy loss from from string string dragdrag

Jet Jet modificationmodifications from wake s from wake

fieldfield

13-Jan-07

S G P S G P “Formerly known as quark-gluon plasma?” You can still use that label if you like, but- PARADIGM PARADIGM

SHIFTSHIFT RIHC does not produce asymptotically “free” quarks and

gluons Contrary to expectations (and announcements ! ), we did

not find evidence for “quarks (that) are liberated to roam freely”

The analogy to atomic plasmas is also strained: Atomic plasmas:

Can vary density and temperature independently Photon momentum-energy density (usually) irrelevant Can be strongly-coupled or weakly coupled

“QGP” One number (the temperature T ) determines all properties Intrinsically strongly-coupled fluid for any(?) accessible T

The matter created at RHIC could be called “S G P” S G P Sui Generis Plasma Sui generis : “Being the only example of its kind; unique ”

13-Jan-07

The Primacy of QCDThe Primacy of QCD While the (conjectured) bound

is a purely quantum mechanical result . . .

It was derived in and motivated by the Anti-de Sitter space / Conformal Field Theory correspondence

Weak form: “Four-dimensional N=4 supersymmetric SU(Nc) gauge theory is

equivalent to IIB string theory with AdS5 x S5 boundary conditions.”( The Large N limit of superconformal field theories and supergravity, J. Maldacena, Adv. Theor. Math. Phys. 2, 231, 1998 hep-th/9711200 )

Strong form: “Hidden within every non-Abelian gauge theory, even within the

weak and strong nuclear interactions, is a theory of quantum gravity.”( Gauge/gravity duality, G.T. Horowitz and J. Polchinski, gr-qc/0602037 )

Strongest form: Only with QCD can we explore experimentally these fascinating connections over the full range of the coupling constant to study QGP

4

s

Quantum Gauge Phluid

13-Jan-07

RHIC Scientific FutureRHIC Scientific Future Fundamental Strings(??)

Fundamental Particles Understand the spin structure of the nucleon p+p at RHIC, RHIC II, …. Polarized e-p collider

Fundamental Fields Understand the wave-function of a heavy nucleus d+A at RHIC, RHIC II, …. Electron-ion collider

Fundamental Matter Understand the phase diagram of QCD A+A at RHIC, RHIC-II, LHC, FAIR