Weak Coherent Kaon Production

1. Weak Coherent Kaon Production L. Alvarez-Ruso1, J. Nieves1, I. Ruiz Simo2, M. Valverde3, M. Vicente Vacas1 • IFIC, Universidad de Valencia • Universidad de Granada • RCNP, Osaka TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAAA

5. Weak Coherent Kaon Production L. Alvarez-Ruso1, J. Nieves1, I. Ruiz Simo2, M. Valverde3, M. Vicente Vacas1 • IFIC, Universidad de Valencia • Universidad de Granada • RCNP, Osaka

6. Introduction • QE and 1¼ are the most important (large and relevant for oscillations) (anti)º interaction channels in the few-GeV region, but there are others… • Strangeness production: • ¢S = 0 e.g. • ¢S = 1 : • Cabibbo suppressed but with lower thresholds than ¢S = 0 • Hyperon e.g. • Kaon: • Background for proton decay p !º K+ • Accessible by Minerºa but also MiniBooNE, T2K, … • There is a coherent channel

7. Introduction • QE and 1¼ are the most important (large and relevant for oscillations) (anti)º interaction channels in the few-GeV region, but there are others… • Strangeness production: • ¢S = 0 e.g. • ¢S = -1 : • Cabibbo suppressed but with lower thresholds than ¢S = 0 • antiKaon: • Accessible by Minerºa but also MiniBooNE, T2K, … • Potentially interesting for antiº beams • There is a coherent channel

8. The model • Microscopic kaon production on the nucleon • The coherent reaction • Kaon distortion

9. The model • Microscopic kaon production on the nucleon Rafi Alam et al., PRD82 • Includes all terms in SU(3)chiral Lagrangians at leading order • Parameters: f¼ , ¹p and ¹n, D and F (from semileptonic decays) • A global dipole form factor : F(q2)=(1-q2/M2F)-2 , MF = 1 GeV • Absence of S=1 baryon resonances )Extended validity of model CT KP ¼F, ´F Cr§, Cr¤

10. The model • Microscopic kaon production on the nucleon Rafi Alam et al., PRD82 • Includes all terms in SU(3)chiral Lagrangians at leading order • A global dipole form factor : F(q2)=(1-q2/M2F)-2 , MF = 1 GeV (§ 10%)

11. The model • Microscopic kaon production on the nucleon Rafi Alam et al., PRD82 • vs ¢S = 0 from GENIE

12. The model 2. The coherent reaction • Amplitude: • Nuclear current: • ¼F, ´Fvanish with the sum • initial and final nucleons taken on-shell with averaged momenta:

13. The model 3. Kaon distortion (with DWBA) or in the eikonal approximation: The optical potential: C=0.13 or 0.114 ÃKlein-Gordon eq. Cabrera, Vicente Vacas, PRC69

14. Results • In the Impulse Approximation: • Very smallcross section…

15. Results • In the Impulse Approximation: • Very smallcross section… • Compare to Coh¼+ (on 12C): ¾(Coh¼+,1 GeV)~ 0.05-0.1 >> ¾(CohK+,1.35 GeV)~ 0.00014

16. Results • In the Impulse Approximation: • Very smallcross section… why?

17. Results • In the Impulse Approximation: • Very smallcross section… why? because K is heavy

18. Results • In the Impulse Approximation: • Very smallcross section… why? because K is heavy

19. Results • In the Impulse Approximation: • Very smallcross section… why? because K is heavy ) • Sensitive to the nuclear density distribution

20. Results • In the Impulse Approximation. Contribution from different mechanisms: • CT is the largest contribution, followed by Cr¤ • Interference stronger than in the free case Rafi Alam et al., PRD82 (2010)

21. Results • In the Impulse Approximation. Contribution from different mechanisms: • CT is the largest contribution, followed by Cr¤ • Interference stronger than in the free case

22. Results • With Kaon distortion. Kaon momentum distributions:

23. Results • With Kaon distortion. Kaon momentum distributions: • Eikonal approximation breaks down at low |pK|

24. Results • With Kaon distortion. Kaon momentum distributions: • Eikonal approximation breaks down at low |pK|, unlike in Coh¼ LAR et al., PRC

25. Results • With Kaon distortion. Angular distributions:

26. Results • With Kaon distortion. Angular distributions:

27. The model • Coherent K- production with antineutrinos • Elementary interaction: Rafi Alam et al., PRD 85 • Direct terms with strange baryons (¤, §, §*(1385)) in the intermediate state

28. The model • Coherent K- production with antineutrinos • Elementary interaction: Rafi Alam et al., PRD 85 • N-§*(1385) transition: C3V, C4V, C5V, C3A, C4A, C5A, C6A ff related to those of N-¢(1232) using SU(3) symmetry • In particular: C5A(0) Ã off-diagonal G-T

29. The model • Coherent K- production with antineutrinos • Elementary interaction: Rafi Alam et al., PRD 85 • Small contribution from §*(1385): it is below K production threshold

30. Results • Coherent K- production with antineutrinos • In the Impulse Approximation. Contribution from different mechanisms: • Largest contribution from CT • Strong destructive interference • (Relatively) large§* Rafi Alam et al., PRD85 (2012)

31. The model 3. antiKaon distortion (with DWBA) The optical potential: • K-p interaction dominated by ¤(1405) resonance • ¤(1405) dynamically generated by s-wave meson-baryon rescattering in coupled channels • Dressing of meson propagators (1p1h, ¢h) • Self consistent treatment of antiK ÃKlein-Gordon eq. Ramos, Oset, NPA 671 (2000)

32. The model 3. antiKaon distortion (with DWBA) The optical potential: • Very different interaction vs Kaon case: ÃKlein-Gordon eq. Ramos, Oset, NPA 671 (2000)

33. Results • With antiKaon distortion. Momentum distributions:

34. Conclusions • (anti)Neutrino induced coherent (anti)kaon production has been studied • Microscopic production mechanism based on SU(3)chiral Lagrangians • Coherent sum over all (noninteracting) nucleons • DWIA for the outgoing (anti)kaon by solving the KG eq. with a realistic density-dependent potential • Small cross sections are obtained due to: • Small (Cabibbo suppressed) c. s. on nucleons • Large momentum transferred to the nucleus because of the largekaon mass • Destructive interference • Kaondistortion (stronger for K- as expected) • Eikonal approximation is wrong at low momenta