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Parity violating neutron spin asymmetry of process in pionless effective theory

Parity violating neutron spin asymmetry of process in pionless effective theory. Jae Won Shin Collaborators: Shung-Ichi Ando 1) , Chang Ho Hyun 1) , Seung-Woo Hong Department of Physics, Sungkyunkwan University, Korea 

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Parity violating neutron spin asymmetry of process in pionless effective theory

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  1. Parity violating neutron spin asymmetry of process in pionless effective theory Jae Won Shin Collaborators: Shung-IchiAndo1), Chang Ho Hyun1), Seung-Woo Hong Department of Physics, Sungkyunkwan University, Korea  1)Department of Physics Education, Daegu University, Korea The 5th Asia-Pacific Conference on Few-Body Problems in Physics 2011(APFB 2011)

  2. OUTLINE • Introduction • Effective Lagrangian • Results • Summary

  3. 1. Introduction • Pionless Effective Field Theory with dibaryon field (dEFT) approach • Pion (heavy degree of freedom) → integrate out • Expansion of Q/Λ (Q: light, Λ: heavy) • fast conversions Applications for low energy nuclear physics • Radiative neutron capture on a proton at BBN energies 1) • neutron-neutron fusion 2) • neutral pion production in proton-proton collision near threshold 3) • proton-proton fusion 4) 1)S. Ando et al., Phys. Rev. C 74, 025809 (2006). 2)S. Ando and K. Kubodera, Phys. Lett. B 633, 253 (2006). 3)S. Ando, Eur. Phys. J. A 33, 185 (2007). 4)S. Ando et al., Phys. Lett. B 668, 187 (2008).

  4. Extend the dEFT works, “parity violating (PV) interaction” was considered. • PV asymmetry in at thermal energies 5) • PV polarization in at threshold 6-8) From these works, unknown LEC h0tdNN, h0sdNN and h1dNN are appearing. Not yet were determined ! Recent work • Neutron spin polarization in 9) - Neutron spin polarization Py’ [Px’, Pz’ = 0 (chosen coordinate)] - Only parity conserving part contribute ! • However, • Px’ and Pz’≠ 0 with parity violating interactions • Pz’ (in this work) 5)M. J. Savage, Nucl. Phys. A 695, 365 (2001). 6)C. H. Hyun, J. W. Shin and S. Ando, Modern Phys. Lett. A 24, 827 (2009). 7)S. Ando, C. H. Hyun and J. W. Shin, Nucl. Phys. A 844, 165c (2010). 8)J. W. Shin, S. Ando and C. H. Hyun, Phys. Rev. C 81, 055501 (2010). 9)S. Ando et al., Phys. Rev. C 83, 064002 (2011).

  5. Weak interactions • In this work, • We consider the two-nucleon weak interactions with a pionless effective field theory. • Introducing a di-baryon field for the deuteron, we can facilitate the convergence of the theory better than the one without di-baryon fields. dEFT Standard way Contact interactions (LEC) Exchange of π, ω, ρ meson • The weak interactions are accounted for with the parity-violating di-baryon-nucleon-nucleon vertices, which contain unknown weak coupling constants. • We calculate the parity-violating neutron spin asymmetry in process, where we consider incident photon energies up to 30~MeV.

  6. 2. Effective Lagrangian a) Parity conserving part of the Lagrangian

  7. : Odd at a PV vertex b) Parity violating part of the Lagrangian : Even 1S0 ↔ 3P0 3S1 ↔ 1P1 Unknown LECs 3S1 ↔ 3P1

  8. 3. Results Leading order (Q0) PV diagrams * Counting rules Single solid line : nucleon Wavy line : photon Double line with a filled circle : dressed dibaryon Blue circle : PC dNN vertex Circle with a cross : PV dNN vertex ∨PC dNN vertex ∝ Q1/2 ∨Photon, derivative ∝ Q1 ∨ Nucleon, Dibaryon propagator ∝ Q-2 ∨Loop ∝ Q5

  9. Amplitude χ1, χ2 : nucleon spinors ɛ(d) : deuteron polarization vector ɛ(γ) : photon polarization vector

  10. Pz’ A = APC + APV |APC|2 term |APC*APV| interference term * |APV|2 terms are ignored. PV LECs ∝ 10-5 |APV|2 term ∝ 10-10

  11. Preliminary results h100 : Coefficient of h0tdNN h010 : Coefficient of h0sdNN h001 : Coefficient of h1dNN • Coefficients of h010, h001 shows same feature. As the angle (lab) increase, dependency of the incident photon energies (lab) of neutron spin polarization decrease. • But, coefficient of h100 seem to be seen angle (lab) independent.

  12. h100 : Coefficient of h0tdNN • Θlab increase • → E1 contribution increase • → M1 contribution decrease (go to zero) • For Θlab = 90° • → E1 contribution dominants ! • Cancelation between E1 and M1 ~ nearly constant Preliminary results

  13. h010 : Coefficient of h0sdNN Θlab increase → E1 contribution increase → M1 contribution decrease For Θlab = 90° → E1 contribution (65% ?) Preliminary results

  14. h001 : Coefficient of h1dNN • Θlab increase • → E1 contribution increase • → M1 contribution decrease (go to zero) • For Θlab = 90° • → E1 contribution dominants ! • For Θlab = 30° • → M1 contribution dominants ! Preliminary results

  15. 4. Summary • The weak interactions are accounted for with the parity-violating di-baryon-nucleon-nucleon vertices, which contain unknown weak coupling constants. • We calculate the parity-violating neutron spin asymmetry in process, where we consider incident photon energies up to 30~MeV. • Overall characteristics, Θlab increase and E1 contribution increase but M1 contribution decrease. • M1 contribution gives significant role for PV neutron spin polarization. • A possible experiment or theory from which one can get information about the unknown weak coupling constants and hadronic weak interactions is discussed.

  16. Thank you for your attention !

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