Isospin effect in the projectile fragmentation of calcium isotopes and a possible experimental obser

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Isospin effect in the projectile fragmentation of
calcium isotopesand a possible experimental
observable?

• Chun-Wang Ma
• Department of Physics, Henan Normal University
• Email machunwang_at_126.com

Outlook

• 1. Backgrounds
• 2. The SAA Model
• 3. PF of calcium isotopes
• 4. Results and Discussion
• 5. Conclusions

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1. Backgrounds

• Projectile fragmentation is one of the basic
  experimental method in RIB era.
• NSCL experiment 40,48Ca9Be/181Ta,
  58,64Ni9Be/181Ta, 86Kr9Be
• New generation or updated RIB facilities expand
  the nuclear chart to more neutron-rich and
  proton-rich sides.
• Increasing interests in EOS of asymmetric nuclear
  matter n-rich nuclei
• Hotter in the research of ISOSPIN physics.
• Neutron density distribution of neutron-rich
  nucleus hard to be extracted or measured.
• Neutron skin thickness important in nuclear phys.
  etc.

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1. backgrounds neutron skin thickness and EOS
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1. Backgrounds

• Neutron density distribution or neutron skin
  thickness of asymmetric nuclear matter not easy
  to know but important in nuclear physics.
• Isospin phenomena are strongly related to the
  different proton and neutron density distribution
  of asymmetric nucleus.
• Can the isospin phenomena be used to extract
  neutron density distribution of neutron skin
  thickness directly? The observable!

D.Q.Fang, et al., PhysRevC61(2000)044610Ma
Chun-Wang, et al., Chin.Phys.B,17(2008)1216 Ma
Chun-Wang, et al., Phys.Rev.C79(2009)034606,Chin.
Phys. B18(11)(2009), to be published
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Chin. Phys. B 17(04)(2008)1674
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Backgrounds

• Isospin dependence of PF

140A MeV 40,48Ca/ 58,64Ni9Be

• Isospin effect in fragments production and its
  decrease
• Obvious in the productions of peripheral
  reactions. (big difference of proton and neutron
  density distribution in the surface of nucleus)
• Decrease and disappear in the productions of
  central collisions. (similar proton and neutron
  density distributions in the core of nucleus)

Ma Chun-Wang, et al., Chin. Phys. B18(11)(2009),
to be published
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1. Backgrounds

• How do the peak position of the fragments
  distributions change in the PF of a series of
  isotopes?
• If there are some parameters or observables that
  are related to neutron skin thickness? Find the
  correlation between neutron skin thickness and
  some observables.

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2. The statistical abrasion-ablation (SAA) model

• Brohm Schmidt, Fang, Zhong, etc,
• Simple and useful
• 2-steps reactions
• Collisionsparticipant and spectator
• De-excitation

RefsNPA569(1994)821, PRC61(2000)044610, CPC
27(2003)39, EPJA10(2001)381,PRC79(2009)034606
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2. The statistical abrasion-ablation (SAA) model
The colliding nuclei parallel tubes.
Isotope production
De-excitation
transmission probabilities for neutrons (protons)
at b
the average absorbed mass in an infinitesimal
tubes at b
Density distributions Fermi-type
Y.Eisenberg, PhysRev 52(1954)1378
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3. PF of odd 36-52Ca isotopes

• Fragments productions of 80A MeV 36-52Ca12C
  reactions

Plateau and its drop
Disappearance of the isospin effect the overlap
of the fragment cross section distributions
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4. Results and discussion

• Fit these isotopic distributions by Gaussian
  function
• Peak positions
• Widths

Good linear correlation pk Vs. Zfrag
preliminary

• Fit the linear correlations between pk position
  and Zfrag
• Slope (b)
• Intercept (a)

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4. Results and discussion

• correlations between slope b and binding energy,
  b and Nproj

preliminary
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4. Results and discussion

• Correlation between b and Sn-Sp

preliminary
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4. Results and discussion

• Correlation between b and neutron skin thickness

Good linear correlation
preliminary
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4. Results and discussion
preliminary
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5. Conclusion

• The cross sections of fragments produced in 80 A
  MeV even 36-52Ca PF on 12C were calculated by the
  SAA model.
• The fragments isotopic cross section
  distributions were fitted by Gaussian function,
  peak positions were obtained.
• The Apk have good linear correlation to the
  Zfrag. The linear correlation were fitted and
  slopes b were obtained.
• The correlation between b and Nproj., Sn, Sn-Sp,
  dnp were analyzed.
• Good linear correlation between b and dnp are
  found.
• Still a question b possible to serve as an
  observable for neutron skin thickness?