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Neutrino cross sections from a theoretical perspective Luis Alvarez-Ruso IFIC, Valencia

Euro n. Neutrino cross sections from a theoretical perspective Luis Alvarez-Ruso IFIC, Valencia. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A A A A A A A. Introduction. Neutrino - nucleus interactions are important for:

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Neutrino cross sections from a theoretical perspective Luis Alvarez-Ruso IFIC, Valencia

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  1. Euron Neutrino cross sections from a theoretical perspectiveLuis Alvarez-RusoIFIC, Valencia TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAAAAAAA

  2. Introduction • Neutrino-nucleus interactions are important for: • Oscillation experiments • º detection, Eºreconstruction, ºflux calibration • Electron-like backgrounds: • NC¼0 production (incoherent, coherent) • Photon emission in NC • Hadronic physics • Nucleon and Nucleon-Resonance (N-¢, N-N*) axial form factors • Strangeness content of the nucleon spin • Nuclear physics • Information about: nuclear correlations, MEC, spectral functions • nuclear effects: essential for the interpretation of the data

  3. Introduction • Most relevant processes in the few-GeV region: • Quasielastic scattering • Single pion production (incoherent and coherent)

  4. QE scattering • º detection: • Eºreconstruction: • Assumes that • Important for oscillations: • QE ¾ affect the expected sensitivities to oscillation parameters • Example: Fernandez, Meloni, arXiv:1010.2329 • ¯ beam hypothetical exp.: < Eº > 0.3 GeV, 16O target • Sensitivities to µ13 and ±CP vary ~ 10-30 % depending on the nuclear CCQE model

  5. º QE scattering dipole ansatz PCAC • The (CC) elementary process: where • Vector form factors: extracted from e-p, e-d data • Axial form factors:

  6. º QE scattering • The (CC) elementary process: • gA = 1.267 ï decay • MA= 1.016 § 0.026 GeV ( ) Bodek et al., EPJC 53 (2008) • MA from ¼electroproduction on p: • Connected to FA at threshold and in the chiral limit (m¼ =0) • Using models to connect with data ) • MAep= 1.069 § 0.016 GeV Liesenfeld et al., PLB 468 (1999) 20 • Hadronic correction (ChPT) Bernard et al., PRL 69 (1992) 1877 • MA = MAep - ¢MA , ¢MA =0.055 GeV ) MA = 1.014 GeV

  7. º QE scattering • Relativistic Global Fermi GasSmith, Moniz, NPB 43 (1972) 605 • Impulse Approximation • Fermi motion • Pauli blocking • Average bindingenergy • Explains the main features of the (e,e’)inclusive¾ in the QE region • Fails in the details (nuclear dynamics needed)

  8. º QE scattering • Spectral functions of nucleons in nuclei • The nucleon propagator can be cast as • Sh(p)Ãhole (particle) spectral functions: 4-momentum (p) distributions of the struck (outgoing) nucleons • §Ã nucleon selfenergy • Better description of (e,e’)inclusive¾ Benhar et al., PRD 72 (2005) Ankowski, Sobczyk, PRC 67 (2008) Nieves et al., PRC 70 (2004) Leitner et al., PRC 79 (2009)

  9. º QE scattering • Relativistic mean field • Impulse Approximation • Initialnucleon in a bound state (shell) • ªi : Dirac eq. in a mean field potential (!-¾ model) • Finalnucleon • PWIA • RDWIA: ªf : Dirac eq. for scattering state • Glauber • Problem: nucleon absorption that reduces the c.s. • Can be used to study: • 1Nknockout • inclusive processes: with only Re[Vopt] Martinez et al., PRC 73 (2006) Budkevich, Kulagin, PRC 76 (2007) Complex optical potential

  10. º QE scattering • RPA long range correlations • Incorporates N-hole and ¢-hole states • V: ¼, ½ exchange, Landau-Migdal parameter g’ • Describes correctly ¹ capture on 12C and LSNDCCQE • Collective effect: important at low Q2for º QE Singh, Oset, NPA 542 (1992) Marteau, Delorme, Ericson, NIMA 76 (2000) Nieves et al., PRC 70 (2004)

  11. º QE scattering • Comparison toMiniBooNE¾ • At Eº =0.8 GeV: ¾th ~ 4.5-5 < ¾MB ~ 7 £ 10-38 cm2 • CCQE models with MA~1 GeV cannot reproduce MiniBooNE¾ Source: Boyd et al., AIP Conf. Proc. 1189 Data: MiniBooNE, PRD 81, 092005 (2009)

  12. º QE scattering • Comparison toMiniBooNE¾ • Proposed solutions: • MA=1.35 § 0.17 GeV (RFG) MiniBooNE, PRD 81, 092005 (2010) • However, MA>1 GeV is incompatible with: • data • ¼electroproduction on p (at low Q2) • NOMAD: MA = 1.05 § 0.02(stat) § 0.06(sys) GeV Lyubushkin et al., EPJ C63

  13. º QE scattering • Comparison toMiniBooNE¾ • Proposed solutions: • MA=1.37 GeV (RDWIA) Butkevich, arXiv:1006.1595 • Fit to d¾/dQ2 (shape only) • Better than RFG at low Q2

  14. º QE scattering • Comparison toMiniBooNE¾ • Proposed solutions: • MA=1.37 GeV (RDWIA) Butkevich, arXiv:1006.1595 • Fit to d¾/dQ2 (shape only) • Good description of double differential cross section

  15. º QE scattering • Comparison toMiniBooNE¾ • Proposed solutions: • MA=1.6 GeV (Spectral Function) Benhar, Coletti, Meloni, PRL 105 (2010) • Fit to d¾/dQ2

  16. º QE scattering • Comparison toMiniBooNE¾ • Proposed solutions: • MA=1.343 § 0.060 GeV (Spectral Function) Juszczak, Sobczyk, Zmuda, arXiv:1007.2195 • Fit to double differential c. s. including flux uncertainty • Momentum transfer cut qcut = 500 MeV to exclude IA breakdown region: insufficient to reconcile MiniBooNE with exp. on deuterium

  17. º QE scattering • Comparison toMiniBooNE¾ • Many body RPAMartini et al., PRC 80 (2009), 81 (2010) • RPA: small reduction • Large2p-2h contribution to º12C mainly from (2),(3),(3’)

  18. º QE scattering • Comparison toMiniBooNE¾ • Many body RPAMartini et al., PRC 80 (2009), 81 (2010) 12C(e,e’)X • RPA: small reduction • Large2p-2h contribution to º12C mainly from (2),(3),(3’) • MEC absent (but important for (e,e’) in the dip region) Gil, Nieves, Oset, NPA627

  19. º QE scattering • Comparison toMiniBooNE¾ • Many body RPAMartini et al., PRC 80 (2009), 81 (2010) • RPA: small reduction • Large2p-2h contribution to º12C mainly from (2),(3),(3’) • Prediction: smaller2p-2h contribution to anti-º12C • Detailed tests against e-scattering data are necessary

  20. 1¼ production • Reactions • Incoherent: • Coherent: • CC • NC • Relevant for oscillations • NC¼0: e-like background to º¹!ºe searches (µ13 & ±$CP violation) • Source of CCQE-like events (in nuclei), needs to be subtracted for a good Eº reconstruction

  21. 1¼ production • Reactions • Incoherent: • Coherent: • CC • NC • Relevant for oscillations • NC¼0: e-like background to º¹!ºe searches (µ13 & ±$CP violation) • Source of CCQE-like events (in nuclei), needs to be subtracted for a good Eº reconstruction Leitner, Mosel, PRC 81

  22. 1¼ production • Elementary process: • Dominated by resonance production • At Eº ~ 1 GeV: ¢(1232) • N-¢ transition current: • Form factors , Helicity amplitudes (A1/2, A3/2, S1/2)

  23. 1¼ production • Elementary process: • Dominated by resonance production • Rein-Sehgal model: Rein-Sehgal, Ann. Phys. 133 (1981) 79. • Used by almost all MC generators • Relativistic quark model of Feynman-Kislinger-Ravndal with SU(6) spin-flavor symmetry • Helicity amplitudes for 18 baryon resonances • Lepton mass = 0 • Corrections: • Poor description of ¼ electroproduction data on p Kuzmin et al., Mod. Phys. Lett. A19 (2004) Berger, Sehgal, PRD 76 (2007) Graczyk, Sobczyk, PRD 77 (2008)

  24. 1¼ production • Elementary process: • Dominated by resonance production • Rein-Sehgal model: Rein-Sehgal, Ann. Phys. 133 (1981) 79. • Used by almost all MC generators • Relativistic quark model of Feynman-Kislinger-Ravndal with SU(6) spin-flavor symmetry • Helicity amplitudes for 18 baryon resonances • Lepton mass = 0 • Corrections: • Poor description of ¼ electroproduction data on p Kuzmin et al., Mod. Phys. Lett. A19 (2004) Berger, Sehgal, PRD 76 (2007) Graczyk, Sobczyk, PRD 77 (2008)

  25. 1¼ production • N-¢ transition current • Helicity amplitudes can be extracted from data on ¼photo- and electro-production • Unitary isobar model MAID Drechsel, Kamalov, Tiator, EPJA 34 (2007) 69 • Uses world data • for all 4 star resonances with W<2 GeV • Unitary isobar model+Regge-pole BG at high energies I. Aznauryan, PRC67 • Dispersion relations • CLAS (JLab) data • 1st and 2nd resonance regions: ¢(1232), N*(1440), N*(1520), N*(1535)

  26. 1¼ production • N-¢ transition current • Axial form factors PCAC Adler model

  27. 1¼ production • N-¢axial form factors: determination of CA5(0) and MA ¢ • From ANL and BNL data on • with large normalization (flux) uncertainties • Graczyk et al., PRD 80 (2009) • Deuteron effects • Non-resonant background absent • CA5(0)=1.19 § 0.08, MA ¢= 0.94 § 0.03 GeV • Hernandez et al., PRD 81 (2010) • Deuteron effects • Non-resonant background fixed by chiral symmetry • CA5(0)=1.00 § 0.11 GeV, MA ¢= 0.93 § 0.07 GeV • 20 % reduction of the GT relation off diagonal GT relation

  28. 1¼ production • Incoherent 1¼production in nuclei • Large number of excited states )semiclassical treatment • ¼propagation (scattering, charge exchange), absorption (FSI) • Most models cannot calculate this reaction channel. Exceptions: • MC generators: NUANCE, NEUT, GENIE, NuWro • Cascade: Ahmad et al., PRD 74 (2006) • Transport: GiBUU

  29. 1¼ production • Incoherent 1¼production in nuclei (FSI) • NuWroJ. Sobczyk et al. • Intranuclear cascade • ¼propagation: empirical ¼-N vacuum ¾ • ¼absorption: ¼-A absorption data • Ahmad et al., PRD 74 (2006) • Cascade (~NuWro) • In-medium modification of ¢ spectral f. (only in the production) • GiBUU • Transport: one approach for eA, ºA, pA, ¼A reactions • ¼, N but also ¢ are propagated • Main absorption mech.: ¢N!N N, ¼N N!N N

  30. 1¼ production • Comparison to the ¾(CC¼+)/¾(CCQE-like) ratio at MiniBooNE Athar et al. NuWro GiBUU

  31. 1¼ production • Coherent pion production • CC • NC • Takes place at low q2 • Very small cross section • At q2» 0, axial current not suppressed NEUT Hiraide@NuInt09

  32. 1¼ production • Coherent pion production models • PCAC • In the q2=0 limit, PCAC is used to relate ºinduced coherent pion production to ¼Aelastic scattering • Extrapolated to q2 0 • R&S: describe ¼A in terms of ¼N scattering • B&S, P&S: use ¼A data • Problems: Hernandez et al., PRD 80 (2009) 013003 • q2=0 limit neglects important angular dependence at low energies • R&S: The ¼A elastic description is not realistic • B&S,P&S: spurious initial ¼ distortion present in ¼Abut not in coh¼ Rein & Sehgal NPB 223 (83) 29 Berger & Sehgal, PRD 76 (2007),79 (2009) Paschos & Schalla, PRD 80 (2009),

  33. 1¼ production • Coherent pion production models • PCAC • In the q2=0 limit, PCAC is used to relate ºinduced coherent pion production to ¼Aelastic scattering • Extrapolated to q2 0 • R&S: describe ¼A in terms of ¼N scattering • B&S, P&S: use ¼A data • Problems of PCAC models: less relevant as the energy increases • NOMAD: ¾=72.6 § 8.1(stat) § 6.9(syst) £ 10-40 cm2 • Consistent with RS:¾¼ 78£10-40 cm2 Rein & Sehgal NPB 223 (83) 29 Berger & Sehgal, PRD 76 (2007),79 (2009) Paschos & Schalla, PRD 80 (2009),

  34. 1¼ production • Coherent pion production • Microscopic models: • ¢ excitation is dominant • ¢ properties change in the nuclear medium • ¼distortion: DWIA with optical potential based on ¢-hole model • Treatment is consistent with incoherent ¼ production • Valid only at low energies Singh et al., PRL 96 (2006) LAR et al, PRC 76 (2007) Amaro et al., PRD 79 (2009) Nakamura et al., PRC 81 (2010)

  35. 1¼ production • Coherent pion production Boyd et al., AIP Conf. Proc. 1189

  36. 1¼ production • Coherent pion production • SciBooNE:PRD 81 (2010) • NC ¼0¾ compatible with R&S • CC¼+/NC¼0=0.14+0.30-0.28 • Theoretical models predict CC¼+/NC¼0» 1-2 ! Boyd et al., AIP Conf. Proc. 1189

  37. Conclusions • New data with high statistics available • Comparison shows discrepancies that await explanation (not fits) • QE: 2p2h and MEC more important that in (e,e’) at fixed energy • Incoherent 1¼ production data underestimated • Comparison to inclusive data is needed • SciBooNE CC¼+/NC¼0=0.14+0.30-0.28for 1¼ coherent is incompatible with theoretical results

  38. º QE scattering • Comparison toMiniBooNE¾ • Model dependence in data: • Background (CCQE-like) depends on the ¼ propagation (absorption and charge exchange) model (NUANCE) • Eº reconstruction (unfolding) Source: Boyd et al., AIP Conf. Proc. 1189 Data: MiniBooNE, PRD 81, 092005 (2009)

  39. 1¼ production • Reactions • Incoherent: • Coherent: • CC • NC • Relevant for oscillations • NC¼0: e-like background to º¹!ºe searches (µ13 & ±$CP violation) • Source of CCQE-like events (in nuclei), needs to be subtracted for a good Eº reconstruction Leitner, Mosel, PRC 81

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