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Analysis of Low Energy Pion Spectra

Analysis of Low Energy Pion Spectra. HIM Apr. 18, 2007 at Yonsei Univ. Suk Choi Prof.: Kang Seog Lee Chonnam National University. Low p t pion enhancement is either from D resonance contribution or Coulomb interaction.

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Analysis of Low Energy Pion Spectra

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  1. Analysis of Low Energy Pion Spectra HIM Apr. 18, 2007 at Yonsei Univ. Suk Choi Prof.: Kang Seog Lee Chonnam National University

  2. Low pt pion enhancement is either from D resonance contribution or Coulomb interaction. Near pion production threshold energy, pions are produced through D resonance. Charged pion spectra in Au+Au collision at 2, 4, 6, and 8 GeV/A by E895 Collaboration were analyzed by ellipsoidal Blastwave Model with resonance contribution& Coulomb Correction. p-/p+ is used as a fitting parameter to study beam energy dependence. Purpose

  3. Cooper-Frye Formula Fit Parameters Thermal Spectrum Blast-Wave Model Lorentz-Transformed Boltzman distribution Ellipsoidally expanding fireball model. Spectrum is determined by freeze-out values.

  4. is overall constant. Vp+ , Vp- each parameters are fitted. is longitudinal rapidity. is transverse rapidity at (R0, z=0) Inside : linear transverse rapidity profile ellipsoidal expansion Parameters Herald Dobbler et al

  5. Resonance contribution by J. Sollfrank N=118 ,Z=79 in Au+Au Spectrum Calculation Coulomb Correction Resonance Contribution Thermal Spectrum

  6. is the unshifted invariant cross section Coulomb Correction

  7. Fitted Values for each parameters

  8. E895, Au+Au at 2 GeV/A mt - m0 Transverse Mass Spectrum

  9. E895, Au+Au at 8 GeV/A mt - m0 Transverse Mass Spectrum

  10. Rapidity Spectrum

  11. for comparison Tch= 50MeV and mbch=850MeV at 1GeV/A Au+Au from particle ratio analysis Cleymans et al., Phys. Rev. C59, 1663(1999)

  12. Conclusion • Small freeze-out temperature with large expansion velocities are obtained and thus resonance contribution is negligible. • Difference in the low momentum region of the two oppositely charged pions are due to the final state Coulomb interaction. Effect of Coulomb interaction decreases as beam energy increases. • Near 2 GeV/A, p-/p+ is about 1.94. As energy increases the ratio decreases.

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