Transcript The Rare Isotope Accelerator Program at MSU

The Rare Isotope Accelerator
Program at MSU
Gary Westfall
Michigan State University
With contributions from
Konrad Gelbke
Presentation to Rare Ion Science Assessment Committee
Brad Sherrill
Hendrik Schatz
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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 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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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 ?
What is the nature of matter at extreme conditions ?
(for example in neutron stars ?)
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International Solutions
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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?
• 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
• 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-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 Elements
• All cost estimates are in FY05 dollars and based upon NSCL labor
rates
• Total Estimated Cost (TEC)
(excluding contingency)
$376 M
• Contingency
$94 M
• Preoperations
$57 M
• R&D
$10 M
• Total Project Cost (TPC)
$537 M
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MSU-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 Upgrade
• Fast beams, gas stopping, reaccelerated beams – no ISOL
– 180 MeV/u 238U @ 80 kW, 215 MeV/u 129Xe @ 100 kW
TPC: $302 M
(FY2005-$)
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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
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MSU-SCF Intensity Gains over NSCL
(MSU-SCF/NSCL)
Gain factors
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Intensity Gains from 400 AMeV Upgrade of MSU-SCF
Gain factors
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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
Previous Results
Au+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 events
B() and B() for all charged
particles
B(y) for pions and kaons
B(qinv) for pions and kaons
B(qlong), B(qout), and B(qside) for pions
Widths of the Balance Function
Comparison with HIJING
and Blast Wave Models
Gary Westfall
Gary Westfall
Michigan State University
for the STAR Collaboration
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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
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|
1 N (y)  N (y) N (y)  N (y) 
B(y)  


2 
N
N

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
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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
no electrons
Central
Real
Shuffled
Mixed
Peripheral
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Balance Function Widths, All Charged Particles
p+p, d+Au, and Au+Au
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Conclusions
• 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
Identified charged pion pairs (+,-)
p < 0.7 GeV, no electrons
Central
Peripheral
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Balance Function for Kaon Pairs, Au+Au at 200 GeV
Identified charged kaon pairs (K+,K-)
p < 0.7 GeV, no electrons
Central
Peripheral
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Balance Function Widths for Pions and Kaons
p+p and Au+Au
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Comparison to Blast Wave Model
Cheng, Petriconi, Pratt and Skoby, PRC 69, 054906 (2004)
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•
•
•
•
Gary Westfall
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
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Balance Function for Pions using qinv
Identified charged pion pairs (+,-)
p < 0.7 GeV, no electrons
HBT/Coulomb Effects
Central
Peripheral
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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 Slides
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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)
Gain factors
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