Gary Westfall 1

The Rare Isotope Accelerator Program at MSU

The Rare Isotope Accelerator Program at MSU

Gary WestfallMichigan State UniversityWith contributions from

Konrad GelbkePresentation to Rare Ion Science Assessment

Committee

Brad SherrillHendrik Schatz

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From the 2002 NSAC Long Range Plan

From the 2002 NSAC Long Range Plan

• 2. The Rare Isotope Accelerator (RIA) is our highest priority for major new construction. RIA will be the world-leading facility for research in nuclear structure and nuclear astrophysics.

• The exciting new scientific opportunities offered by research with rare isotopes are compelling. RIA is required to exploit these opportunities and to ensure world leadership in these areas of nuclear science.

• RIA will require significant funding above the nuclear physics base. This is essential so that our international leadership positions at CEBAF and at RHIC be maintained.

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Questions from Nuclear PhysicsQuestions from Nuclear Physics

•What are the heaviest nuclei that can exist?– How many neutrons can a nucleus hold?– What is the heaviest element?– Are there very long-lived super-heavy elements?

•How do protons and neutrons make stable nuclei and rare isotopes?– Is there a path to understand nuclei in terms of their fundamental constituents and their interactions?

– What are the relevant degrees of freedom and effective interactions in nuclei?

– What is the nature paring phenomena (superconducting phases) in nuclei?

•What is the origin of simple patterns in complex nuclei?– Where does the angular momentum of a nucleus come from?– What is the origin of the dynamical symmetries found in nuclei?

– How do we understand the transition between various symmetry phases?

•What is the equation of state of matter made of nucleons?

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What is the nature of matter at extreme conditions ?

(for example in neutron stars ?)

Questions from Astrophysics

What is the origin of the heavy elements from iron to uranium ?(one of 11 science questions for the “new” century –

NAS report “Connecting Quarks with the Cosmos”)

Why do stars explode ?                   

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International SolutionsInternational Solutions

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The Rare Isotope Accelerator - RIA

The Rare Isotope Accelerator - RIA

•High power heavy-ion driver (400 kW, 400 MeV/nucleon)

•Wide range of research capabilities

All four experimental areas are needed!

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What Science is Addressed by Each Technique?

What Science is Addressed by Each Technique?

• Experiments with fast beams cover most of the science effectively, and the techniques are well established

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Reduced-Cost Options Studied at MSU

Reduced-Cost Options Studied at MSU

• The NSCL group has studied options for rare isotope research

• Option 1: MSU-SCF (MSU South Campus Facility)– Build a new high-power heavy-ion driver plus reaccelerator on a green-field site, allowing staged upgrades to full RIA capability

• Option 2: NSCL Upgrade– Add a 80-100 kW driver and reaccelerator to the existing NSCL site

For both options the technologies for the driver linac and the fast beam capabilities are essentially developed and present no performance risk

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Option 1: MSU-SCFOption 1: MSU-SCF• Fast beams, gas stopping, ISOL, reacceleration

– Energy/nucleon: 180 MeV 238U, 227 MeV 129Xe, 300 MeV 3He, 340 MeV 1H

– Power: 100 kW

TPC $540 M

(FY2005-$)

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MSU-SCF Cost ElementsMSU-SCF Cost Elements

• All cost estimates are in FY05 dollars and based upon NSCL labor rates

• Total Estimated Cost (TEC) $376 M (excluding contingency)

• Contingency $94 M

• Preoperations $57 M

• R&D $10 M

• Total Project Cost (TPC) $537 M

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MSU-SCF Upgrade ElementsMSU-SCF Upgrade Elements• Multi-user capability, flexible selection of upgrade elements

– Energy/nucleon: 400 MeV 238U, 539 MeV 129Xe, 864 MeV 3He, 1122 MeV 1H

– Power 400 kW

Upgrade TPC: $355 M (FY2005-$)

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Option 2: NSCL UpgradeOption 2: NSCL Upgrade

TPC: $302 M (FY2005-

$)

• Fast beams, gas stopping, reaccelerated beams – no ISOL– 180 MeV/u 238U @ 80 kW, 215 MeV/u 129Xe @ 100 kW

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MSU-SCF Scientific Reach:Beam intensities (pps)

MSU-SCF Scientific Reach:Beam intensities (pps)

Scientific reach of NSCL upgrade is very similar to MSU-SCF when in-flight production and separation are used

Gary Westfall 14

MSU-SCF Intensity Gains over NSCL(MSU-SCF/NSCL)

MSU-SCF Intensity Gains over NSCL(MSU-SCF/NSCL)

Gain factors

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Intensity Gains from 400 AMeV Upgrade of MSU-SCF

Intensity Gains from 400 AMeV Upgrade of MSU-SCF

Gain factors

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Summary - RIA Program at MSU

Summary - RIA Program at MSU

• There are sound scientific reasons to include the fast beam capability for any reaccelerated exotic beams facility that makes use of in-flight production techniques Much larger scientific reach Proven technology with no risk

• Several options exist to build a world-class reaccelerated beams facility The NSCL upgrade is a particularly cost-effective

option – but it offers limited possibilities for additional on-site upgrades

The MSU-SCF is an attractive alternative that allows flexible upgrade options to full RIA capability without major disruption of the ongoing research and education program

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Balance Functions at RHIC

Balance Functions at RHIC

Previous ResultsAu+Au at 130 GeV

J. Adams et al., PRL 90, 172301 (2003)

New Results (long PRC paper being prepared by STAR)Au+Au, p+p, d+Au at 200 GeV

100 times more Au+Au eventsB() and B() for all chargedparticles

B(y) for pions and kaonsB(qinv) for pions and kaons

B(qlong), B(qout), and B(qside) for pionsWidths of the Balance FunctionComparison with HIJINGand Blast Wave Models

Gary WestfallMichigan State Universityfor the STAR Collaboration

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Balance Functions and Delayed Hadronization

Balance Functions and Delayed Hadronization

• Bass, Danielewicz, and Pratt [Phys. Rev. Lett. 85, 2689 (2000)] proposed the balance function

• The basic premise is that charge/anti-charge pairs are created close together in space-time

• If these pairs are created early in the collision, they will be pulled apart in rapidity by longitudinal expansion and will suffer scattering for the duration of the collision, losing their correlation in rapidity

• If instead, the system exists in a deconfined phase for a time long compared with 1 fm/c, and then the pairs are created at hadronization, they will experience less expansion and fewer collisions, retaining more of their correlation in rapidity

• Previous measurements for Au+Au at 130 GeV published by STAR, PRL 90, 172301 (2003)

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Definition of the Balance Function

Definition of the Balance Function

To quantify the correlation of charge/anti-charge pairs, Bass, Danielewicz, and Pratt proposed the balance function that counts correlated charge/anti-charge pairs as a function of relative rapidity, y |y2-y1|

N+-(y) is calculated by histogramming y for all negative particles correlated with all positive particles in a given event and the resulting histogram is summed over all events, similarly for N++(y), N-+(y), and N--(y)

N+(-) is the total number of positive(negative) particles summed over all events

€

€

B(Δy) =12

N+− (Δy) −N++(Δy)N+

+N−+(Δy) −N−− (Δy)

N−

⎧ ⎨ ⎩

⎫ ⎬ ⎭

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Understanding the Balance Function

Understanding the Balance Function

• Theoretical expectations for B(y)– PYTHIA representing p+p collisions shows a characteristic width of about 1 unit of y

– Bjorken thermal model representing delayed hadronization shows narrower balance function width• Nucleon-nucleon

– Wide• Delayed hadronization

– Narrow

• Use the width of the balance function as an observable

No STAR acceptance

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Balance Function for All Charged Pairs, Au+Au at 200 GeV

Balance Function for All Charged Pairs, Au+Au at 200 GeV no electrons

Central

Peripheral

RealShuffled

Mixed

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Balance Function Widths, All Charged Particles

p+p, d+Au, and Au+Au

Balance Function Widths, All Charged Particles

p+p, d+Au, and Au+Au

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ConclusionsConclusions• The balance function B() for all charged particles from Au+Au collisions at 200 GeV is much narrower in central collisions than in peripheral collisions– Consistent with models incorporating delayed hadronization

• The width of balance functions from p+p, d+Au, and Au+Au scale with Npart

• The width of the balance functions predicted by HIJING for Au+Au shows no centrality dependence and is similar to p+p

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Balance Function for Pion Pairs, Au+Au at 200 GeV

Balance Function for Pion Pairs, Au+Au at 200 GeV p < 0.7 GeV, no electrons

Central

Peripheral

Identified charged pion pairs (+,-)

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Balance Function for Kaon Pairs, Au+Au at 200 GeV

Balance Function for Kaon Pairs, Au+Au at 200 GeV

p < 0.7 GeV, no electrons

Central

Peripheral

Identified charged kaon pairs (K+,K-)

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Balance Function Widths for Pions and Kaons

p+p and Au+Au

Balance Function Widths for Pions and Kaons

p+p and Au+Au

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Comparison to Blast Wave Model

Comparison to Blast Wave Model

• Blast wave model by Pratt et al.

• Pion gas including emission of charge pairs close together in time and space, radial expansion, resonances, HBT, Coulomb, strong interactions, and STAR acceptance filter

• Predicted width of balance function is narrowest possible

• Agrees with balance function observed in most central bin

• More peripheral bins are clearly wider

Cheng, Petriconi, Pratt and Skoby, PRC 69, 054906 (2004)

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Balance Function for Pions using qinv

Balance Function for Pions using qinv

Peripheral

p < 0.7 GeV, no electronsIdentified charged pion pairs (+,-)

Central

HBT/Coulomb Effects

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Conclusions - Balance Function

Conclusions - Balance Function

• Au+Au results for balance function widths using all charged particles scale smoothly to the p+p and d+Au results as a function of Npart

– Consistent with models incorporating delayed hadronization

• B(y) for kaons is narrower than B(y) for pions and shows no centrality dependence– B(y) for pions in central Au+Au collisions is explained by a complete blast wave model

– B(y) for kaons represents not only a charge balance but a strangeness balance• May indicate that kaons are created early in the collision

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Backup SlidesBackup Slides

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Wait….Wait….• But wait, we still have some questions…– Do different particles have the same balance function widths?•Look at balance function for identified particles

•Look at detailed model predictions

– What about radial flow effects?•Look at B(qinv) that should be insensitive to flow effects

– Does the balance function narrow only in the longitudinal direction?•3D balance functions

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MSU-SCF Intensity Gains over FAIR at GSI

(MSU-SCF/FAIR)

MSU-SCF Intensity Gains over FAIR at GSI

(MSU-SCF/FAIR)

Gain factors