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Time Reversal Invariance in electromagnetic interactions

Time Reversal Invariance in electromagnetic interactions. Alessandra Fantoni INFN - Laboratori Nazionali di Frascati. Introduction Processes Experimental Situation Perspectives. International Workshop on Nucleon Form Factors, LNF 12-14 Ottobre 2005. Introduction –1-.

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Time Reversal Invariance in electromagnetic interactions

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  1. Time Reversal Invariance in electromagnetic interactions Alessandra Fantoni INFN - Laboratori Nazionali di Frascati • Introduction • Processes • Experimental Situation • Perspectives International Workshop on Nucleon Form Factors, LNF 12-14 Ottobre 2005

  2. Introduction –1- Invariance of the laws of physics under discrete symmetry operations reflect fundamental properties of matter • Not all processes are invariant under every simmetry operation: • weak interaction violates invariance under space reflection (parity P) • decay of neutral K meson violates invariance under combined charge conjugation (C) and parity operations (CP) For certain whether C, P and CP conserving interactions are also invariant under time reversal (T): NOT known !!! T invariance is reflected in the law of conservation of energy for systems with conservative forces

  3. Introduction -2- Fundamental theorem of relativistic field theory All interactions must be invariant under CPT operation CP invariance T invariance CP violation T violation No direct tests of T invariance in CP conserving interactions Strong interaction Hh: invariant under Ph, Th and Ch E.m. interaction Hg: invariant under Pg, Tg and Cg

  4. Introduction -3- Hh andHg invariant under Ph = Pg and CgPgTg = ChPhTh For strong interacting particles no complete theory of electromagnetic interaction exists: No evidence Hg invariant under Ch or Th • Difficulty of detection Ch or Th violations: • electromagnetic effects well described by lowest order (Born approximation) • Gauge invariance Test for Th are challenging in electromagnetic interactions of leptons with nucleons

  5. Processes Inelastic lepton scattering on polarised target: l± + Nl± + G ds ≈ aW1 + bW2 + ST (k × k‘) cW3 W3 ≠ 0 Hg violates Th invariance (and also Ch) Literature: Bernstein et al. PR139 (1965) 1650; Christ & Lee PR143 (1966) 1310 Karpman et al PRL16 (1966) 633; Karpman et al. PR174 (1968) 1957 • A ≠ 0: • violation of Th invariance • higher order effects (a3) : interference between 1g and 2g amplitudes without requiring T invariance violation: • A(a3) small • A(a3) charge dependent

  6. Assumption: one-single-photon-exchange Results: No asymmetry at Q2 = 0.2 ÷ 0.7 Accuracy = 4 ÷ 12% Experimental Situation -1- • Cambridge: J.R.Chen et al. PRL 21 (1968) 1279 • J.A.Appel et al. PRD 1 (1970) 1285 Inelastic scattering on h.e. e- from polarized p Target: 92% C2H5OH, 8% H20 PT=22% E(e-) = 4, 6 GeV I = 3 nA

  7. Experimental Situation -1- • Cambridge: J.R.Chen et al. PRL 21 (1968) 1279 • J.A.Appel et al. PRD 1 (1970) 1285

  8. Experimental Situation -2- b) SLAC: S.Rock et al. PRL 24 (1970) 748 Target: 95% butanol, 5% H20 PT=35% E(e-) = 15, 18 GeV Q2 = 0.4, 0.6, 1.0 E(e+) = 12 GeV Q2 = 0.4 e- , e+ but not covering same kinematic range

  9. Experimental Situation -2- b) SLAC: S.Rock et al. PRL 24 (1970) 748 Data everywhere consistent with A = 0

  10. 3 bins at 1200 MeV: A = (4.5±1.4)% difficult explanation Experimental Situation -2- b) SLAC: S.Rock et al. PRL 24 (1970) 748 Data everywhere consistent with A = 0

  11. Experimental Situation -3- • Old data NOT very accurate • Conclusions hard to extract • Points still open for discussion • Jlab LoI 01-002 • How to better investigate the problem ? • What is needed?

  12. a) Inelastic lepton scattering on polarised target: l± + Nl± + G • no FSI interaction (no hadron detected) • e- and e+ A free of a3 effects same sign for e+ and e- ≈ a2 Perspectives -1- e+ and e- in the same kinematic range Emin (e+/e-) = 1.2 GeV (first resonance) Edes (e+/e-) = 3 GeV

  13. b) Unpolarised target, polarised outgoing particle: l± + Nl± + N* Perspectives -2- • no FSI interaction (no hadron detected) • detection of polarization vector of outgoing nucleon • same case as before

  14. c) Exclusive process: hadron detected in final state l± + Nl± + N + p • FSI interaction (hadron detected) • need to evaluate A(a3) effects • (2 g exchange) same sign for e+ and e- ≈ a2 free of FSI different sign for e+ and e- Model dependent access to T-odd GPDs Perspectives -3-

  15. Perspectives inside LNF • LNF is studying perspectives for the future • Increase of energy of DAFNE • Possibility to use upgraded DAFNE Linac

  16. Courtesy of SPARC/X Collaboration

  17. Courtesy of SPARC/X Collaboration

  18. Courtesy of SPARC/X Collaboration

  19. Courtesy of SPARC/X Collaboration

  20. Courtesy of SPARC/X Collaboration

  21. Courtesy of SPARC/X Collaboration

  22. Perspectives • LNF is studying scenarios for near-mid-long range • MIUR funds for SPARXino R&D • Proposal within beginning 2006 from SPARC/X Collaboration for Dafne Linac upgrade from 800 MeV to 1.2-1.5 GeV • Possibility to E=1.8 GeV under study (new cavities 11 GHz instead of 3 GHz ; new technology for LNF) • e+ beam available (PC) • Possibility to use these beams for dedicated proposals such as Time invariance in em interaction • Further developments depend on approval/decisions

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