E432a: Decay of Highly Excited Projectile-like Fragments Formed in dissipative peripheral collisions at intermediate energies

1. Understanding thermodynamic properties as a function of N/Z

2. Studying N/Z equilibration allows us to probe mass and energy transport in heavy-ion collisions at intermediate energies.

Indiana University + DEMON + GANIL+ GSI + Daresbury + LNS-INFN

M.B. Tsang et al., PRL 92, 260701 (2004)

Both these issues are related to the density dependence of the

asymmetry term!

Creation of more “surface material” (low density nuclear matter that is significantly excited)

1. L.G. Sobotka et al., PRL 93, 132702 (2004)2. J. Toke et al, PRC 72 031601 (2005)3. L.G. Sobotka et al., PRC 73, 014609 (2006)

PLF* decay

Comparison of PLF* decay (~ 0) with mid-rapidity (low )

Event selection: 15≤Z≤46 in 2≤lab≤4 Nc≥5 in 4

Proof of approach in studying PLF* decay

PLF*

TLF*

Decreasing VPLF*

Increasing E*

R. Yanez et al., PRC68, 011602(2003)

Ability to reach high excitation energy (E*/A~6 MeV) and select it.

114Cd + 92Mo at E/A = 50 MeV

Study particles emitted from surface

YieldSpectraCompositionQuantum states

Thermodynamics of surface with varying

N/Z

114Cd + 92Mo at E/A = 50 MeV

Tidal Effect and Proximity decay

11.35 MeV

3.03 MeV

gr. st.

8Be α + α93 keV

11.44 MeV

3.12 MeV

3.5 MeV

=1.51 MeV

=6.8 eV

• Select 2 particles forward of the PLF (15≤Z≤46)

• construct statistical background with mixed event technique

• Mixed event background in agreement with Monte Carlo simulation

Zsource

Cluster

Transverse Higher Erel

Zsource Zsource

Longitudinal Lower Erel

Short-lived state probes nuclear surface

Zsource

Zsource

β

Zsource

Erel depends on decay angle,

consistent with coulomb tides model

20% effect

11 MeV state only evident for transverse decay

A. B. McIntosh et al., in preparation

This demonstrates the level of resonance spectroscopy possible in

these reactions with FIRST+LASSAAlso intend neutron-fragment resonance spectroscopy!

Keys:1. Good event selection of peripheral

collisions2. High resolution measurement

(angle/energy/isotope) for charged particles

3. Measurement of neutron spectra (DEMON)

FIRST

LASSA

FIRST and LASSA are highly segmented 600 Si channels

ISiS

Measure Z,A,E,Al T. Paduszynski et al., NIM A 547,464 (2005)

Experimental Setup

Data from FIRST commissioning expt.!

FIRST + LASSA at TAMU

Since E432 proposal:

1. Scattering chamber built (thin-wall)2. FIRST concept proved in commissioning expt.3. Publication of initial physics results underway4. ASIC readout successfully used in HiRA experiments5. New electronics (MASE) to facilitate readout of FIRST near completion.6. Integration of VME QDC/TDC into DAQ for DEMON readout.

ElectronicsMASE: Multiplexed

AnalogShaper Electronics

(Readout of FIRST)

512 channels in 2 crate configuration

HiRA ASIC (HINP16C)

(Readout of LASSA)(Preamps, Shaper, Discriminator, TAC)

George L. Engle et al., submitted to NIM

C. J. Metelko et al., in preparation

MRS(low )

QP(normal )

Neutron enrichment of low-density nuclear matter

64Zn + 64Zn at E/A=45 MeV (commissioning expt. for FIRST)

• no initial driving force to N/Z equilibrate

• low density mid-rapidity (MRS) is neutron-rich in comparison to high density (QP).

• Different behavior is observed for the emitted charged particles (large clusterization of N=Z at low density)

• Observation of enrichment above that of the system’s N/Z requires measurement of free neutrons.

Limited neutron statistics! (only 7 n-TOF detectors)

D. Thériault et al., in preparation

Systematic measurement of N/Z enrichment with driving force needed

cross-bombardment reactions

136Xe + 124Sn 6 UT 1.52 1.48 0 YES

136Xe + 112Sn 6 UT 1.52 1.24 YES YES

124Xe + 124Sn 6 UT 1.30 1.48 YES NO

124Xe + 64Ni 6 UT 1.30 1.28 0 YES

136Xe + 112Sn 6 UT 1.52 1.24 Remove all charged particle dets. except FIRST to assess neutron scattering

(N/Z)projectile

Calibration: Fragmentation beams (E/A=20-40 MeV); Time required: 3UT

Count rate estimate: We anticipate running at 2 x 103 events/sec.

1000 evt/sec x 50 part/evt x 4 words/part x 32 bits/word 6 Mb/sec.

This will correspond to a factor of 60 more data than previous expt.

(geometrical efficiency: x 10; running time x 6; interaction rate x 1)

(N/Z)target

N/Z drift

Mass driftE/A=50 MeV

System Lab Publications64Zn + 64Zn,209Bi @ 45 MeV/A TAMU NIMA 547, 464 (2005)

D. Theriault (in preparation)

114,106Cd +98,92Mo @ 50 MeV/A MSU-NSCL A. McIntosh (in preparation)PRC71, 054604 (2005)PRC 70 031601 (R) (2004)PRC 68, 011602 (R) (2003) PRC 65, 061602(R) (2002)PRC 65, 064614 (2002)

112,124Sn + 112,124Sn @ 50 MeV/A MSU-NSCL PRL 92 062701 (2004). PRC 69, 014603 (2004)

Xe + Au @ 50 MeV/A MSU-NSCL PRC 69 061304 (2004).

60Ni + 92,100Mo @ 5-9 MeV/A ANL PRC. 67, 044611 (2003).

12C + 232Th at E/A=16,22 MeV ANL and MSU-NSCL PRC 66,014608 (2002)

Selected publications

Extra slides start here

Proposed measurement

Define emitting source by selecting PLF size (Z) and excitation (velocity damping).

Measure neutrons with DEMON

Measurement with different projectile N/Z

Measurement of different N/Z and mass asymmetry

Measure N/Z of fragments produced in highly aligned breakups

Statistical decay of nuclear matter as a function of N/Z, size, and E*:Isotope yields (e.g. mirror nuclei), spectral shapes (sensitivity to level density), correlation functions (emission timescales), population ratios, etc.

Isospin equilibration/reaction dynamics

Correlation studies of short-lived particle unbound states

W.P. Tan et al., PRC 69, 061304(R) (2004)

FIRST :Forward Indiana Ring Silicon Telescopes

T1 : 200 m Si(IP), S2/ 1mm Si(IP), S2/ 2-3cm CsI(Tl)At 28 cm, = 2.25-7.05 with = 0.1

T2 : 300 m Si(IP), S1/ 2-3cm CsI(Tl) At 19 cm, = 7.37-14.5 with = 0.4

T3 : 300 m Si(IP), S1/ 2-3cm CsI(Tl) At 9 cm, = 15.2-28.5 with = 0.7

Device dedicated to measure the decay of the PLF* :

Limiting temperature Dynamical process PLF* fragmentation ...

Large number of channelsuse of MASE

Design : P.H. Sprunger

5811

6194

6139

6072

5903 5946

1. <M> and Tslope depend linearly on VPLF*

2. E*/A deduced by calorimetry increases monotonically with increasing dissipation reaching a maximum of approximately 6 MeV.

3. <E*> attained is independent of ZPLF, depends on VPLF*

• Select PLF* size by selecting residue Z.• Select excitation by selecting VPLF*

• Vary N/Z by changing (N/Z)proj.,tgt.

FIRST performanceResolution:

• T1: A up to 30 Z up to projectile

• T2: A up to 18• T3: A up to 15

Telescope Case a Case b Case c Case d RejectT1 16 72 0.04 1.2 10.8T2 69 4.7 26.3T3 49 24 27

T. Paduszynski et al.,NIMA547, 464 (2005)

• Second Si of T1 = 1 mm• Particle with large Z

Charge split on the rings

Al