Using GEMINI to study multiplicity distributions of Light Particles

Adil BahalimDavidson College

Summer REU 2005 – TAMU Cyclotron Institute

Overview What is the JBN group doing? Background for my project Procedures / Programs used Results Summary

Current Events in JBN Group Superheavy Elements – BigSol Quark-Gluon Plasma – BRAHMS

Collaboration Nuclear EOS / Reaction Dynamics of

Heavy Ion Collisions – NIMROD

Heavy Ion Collisions Primary Fragments – Thermal / Chemical Equilibrium

(Freezeout) Secondary Fragments & LP’s – Reconstruction Models

NIMROD Used to gather data such as:

Multiplicity distributions Charge/Mass distributions Energy spectra Angular distributions

4π Detector Array Neutrons detected by liquid

scintillators around target Charged particles detected

by modules consisting of a gas ionization chamber, one or two Si detectors and one or two CsI detectors.

Recent Experiments Time-frame of the reaction and technological limitations

make it difficult to gather important information about the properties of the nuclear matter (e.g. stiffness of EOS)

Most recent experiment devised in which neutrons and charged particles measured in coincidence with intermediate mass fragments (IMF’s) originating from primary fragments 64Zn and 64Ni beams incident on:

58Ni, 64Ni, 112Sn, 124Sn, 197Au, 232Th targets IMF’s detected by Si-CsI telescope Neutrons detected by detectors borrowed from DEMON Array LCP’s detected by CsI crystals

Reconstruction Main hurdle is secondary decay (IMF’s) which makes it difficult to

reconstruct primary fragments Antisymmetrized Molecular Dynamics (AMD) calculations used

have shown to be good models for reconstruction Mean multiplicities (obtained from experiment) and distributions

widths (difficult to obtain) of LP’s are used as input parameters in GEMINI

GEMINI is a statistical modeling code that uses the Monte-Carlo method to simulate sequential binary decays of nuclei

AMD Model Reconstruction

Procedure Simulated 1000 decay events for each nucleus

from Z=3 to Z=40 with at least one from each: Stability line (i.e. ~ Z = N) Proton-rich side (~ Z > N) Neutron-rich side (N > Z)

Excitation energies ranged from 2 to 5 MeV/amu in .5 MeV/amu increments

Assumed constant inverse level density parameter (8)

ROOT Relation between mean multiplicities and

the distribution widths of light particles emitted from system Width = 1σ =

Used the program ROOT to create histograms and calculate the distribution widths and the average multiplicities of each particle

Results Found correlation between the mean

multiplicities and distribution widths The best fit at specific Excitation Energies

was a power fit (i.e. y=AxB)

Neutron Width vs. Mean Multiplicity Z=3 to Z=40

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 2 4 6 8 10 12 14 16 18

M ean M ultiplicity

Wid

th

Proton Width vs. Mean Multiplicity Z=3 to Z=40

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 1 2 3 4 5 6 7 8

M ean M ultiplicity

Wid

th

Deuteron Width vs. Mean Multiplicity Z=3 to Z=40

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.5 1 1.5 2 2.5

M ean M ultiplicity

Wid

th

Triton Width vs. Mean Multiplicity Z=3 to Z=40

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

M ean M ultiplicity

Wid

th

3Helium Width vs. Mean Multiplicity Z=3 to Z=40

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

M ean M ultiplicity

Wid

th

4Helium Width vs. Mean Multiplicity Z=3 to Z=40

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 0.5 1 1.5 2 2.5

Mean Multiplicity

Wid

th

Neutron Width vs. Mean Multiplicity at Exc Energy = 3 MeV/amu

y = 0.6065x0.3583

R2 = 0.9766

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 2 4 6 8 10 12 14

M ean M ultiplicity

Wid

th

Neutron Width vs. Mean Multiplicity at Exc Energy = 3 MeV/amu

y = 0.6065x0.3583

R2 = 0.9766

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 2 4 6 8 10 12 14

M ean M ultiplicity

Wid

th

Proton Width vs. Mean Multiplicity at Exc Energy = 3 MeV/amu

y = 0.6859x0.3549

R2 = 0.9192

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 1 2 3 4 5 6

M ean M ultiplicity

Wid

th

Deuteron Width vs. Mean Multiplicity at Exc Energy = 3 MeV/amu

y = 0.9245x0.5224

R2 = 0.9778

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1 1.2

M ean M ultiplicity

Wid

th

Triton Width vs. Mean Multiplicity at Exc Energy = 3 MeV/amu

y = 0.9534x0.4914

R2 = 0.9989

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

M ean M ultiplicity

Wid

th

3Helium Width vs. Mean Multiplicity at Exc Energy = 3 MeV/amu

y = 0.9185x0.4813

R2 = 0.9976

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

M ean M ultiplicity

Wid

th

4Helium Width vs. Mean Multiplicity at Exc Energy = 3 MeV/amu

y = 0.9637x0.5068

R2 = 0.7343

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.5 1 1.5 2 2.5

M ean M ultiplicityW

idth

Power-Function Parameters A & B (y=AxB)

Proton Power Function Parameter A vs. EE

y = 0.016x + 0.6331

R2 = 0.7808

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 1 2 3 4 5 6

Excitation Energy

Param

eter A

Proton Power Function Parameter B vs. EE

y = 0.014x + 0.3183

R2 = 0.8711

00.05

0.10.15

0.20.25

0.30.35

0.40.45

0 1 2 3 4 5 6

Excitation Energy

Param

eter A

Conclusion As expected, we found the relation

between the mean multiplicities and distribution widths of the LP’s

These relations can be used as references to determine the distribution widths from the experimental data on mean multiplicities and implement them as input parameters for the reconstruction models

Acknowledgements JBN Group

REU 2005 Staff

Special Thanks

Dr. Seweryn Kowalski, Adil Bahalim, Dr. Joe Natowitz