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presented by V.I.Mokeev

Analysis of 2 p Production. presented by V.I.Mokeev. g p →2 p N exclusive channels in N* studies. modeling of 2 p photo- and electroproduction by tree level meson-baryon diagrams. phenomenological analysis within the framework of JLAB-MSU model.

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presented by V.I.Mokeev

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  1. Analysis of 2p Production presented by V.I.Mokeev • gp→2pN exclusive channels in N* studies. • modeling of 2p photo- and electroproduction by tree level meson-baryon diagrams. • phenomenological analysis within the framework of JLAB-MSU model. • N* studies in combined analysis of major exclusive channels. Argonne-Osaka coupled channel approach. • Conclusions.

  2. The p-p+p electroproduction amplitudes are needed for credibleevaluation of N* parameters in coupled channel analysis. CLAS data on meson electroproduction at Q2<4.0 GeV2 Exclusive channels in pN scattering responsible for ISI&FSI in meson electro- production p(e,e’)X (trigger) p(e,e’p)p0 p(e,e’p+)n p(e,e’pp+)p- p(e,e’pp+)X

  3. Why the studies of 2p electroproduction are important. D33(1700) electrocouplings from world data on 1p electroproduction from CLAS data on 2p electroproduction combined analysis of 1p/2p CLAS data

  4. Meson-baryon (MB) models(partial list of references). • L. Luke, P. Soding, Springer Tracts in Modern Physics 59 (1971) 39. • L.Y. Murphy, J.-M. Laget, DAPNIA-SPHN-96-10. • J.A. Gomez Tejedor, E. Oset, Nucl. Phys. A571 (1994) 667. • J.A. Gomez Tejedor, E. Oset, Nucl. Phys. A600 (1996) 413. • J.C. Nacher, et. al., Nucl. Phys. A695 (2001) 295. • S. Ong, J. Van de Wiele, Phys. Rev. C63 (2001) 024614. • W. Roberts, A.Rakotovao, hep-ph/9708236 • W. Roberts, T.Oed, Phys. Rev. C71 (2005) 055201. • M. Hirata, K. Ochi, T. Takaki, Phys. Rev. C56 (1997) 1472. • M. Hirata, N. Katagiri, T. Takaki, Phys. Rev. C67 (2003) 034601. • M. Ripani, V.I. Mokeev, et. al., Nucl. Phys. A672 (2000) 220. • V.I. Mokeev, et. al., Phys. of Atom. Nucl. 64 (2001) 1292. • V. Bernard, N .Kaiser, U.G. Meissner, Eur. Phys. J. A11 (2001) 209. • A. Fix, H. Arenhovel, Eur. Phys. J. A25 (2005) 115.

  5. Valencia group approach.(applicable at W<1.6 GeV) M=p,r; B=p,D,P11(1440),D13(1520), D33(1700); relevant for W<1.6 GeV Isobar channels: pD, rp, pP11(1440) & pN background non fully relativistic description (resolved in ref. 6 at p.5); c-numbers instead of vertex functions (in part resolved in ref. 6 at p.5) ; no ISI&FSI effects The contributions: -pD Born terms - to pD extra terms of JM06 - to direct 2p production ofJM06 -s-channel N* excitation

  6. Fully relativistic description. W.Roberts approach. p,V-mesons and all N*,D* of 1/2, 3/2 spin are included. A general framework for most comprehensive MB description in N* excitation region. r g N N*,D* p • Open problems: • reliability of effective MB lagrangians→test against data on N* LS partial decay widths; • vertex functions, most of them are still unknown; • ISI&FSI should be implemented

  7. A.Fix and H.Arenhövel approach. M=p,r,s, B=N,D All N*,D* with masses less then 1.8 GeV are included to s-channel amplitudes. Effective description of ISI&FSI within the framework of diffractive absorptive ansatz • Open problems: • completeness of mechanisms at high W; • credibility of approximations for ISI&FSI, considering huge absorptive effects

  8. How well MB approaches working? Reasonable description of fully integrated cross-sections in all approaches, BUT huge ad hoc absorptive corrections at W>1.6 GeV. gp→p0p0p ABBHHM, TAPS data in comparison with A.Fix, H.Arenhovel model

  9. Cont’d gp→p0p0p gp→p+p0n TAPS data E.Oset,et.al. model E.Oset,et.al. model Discrepancies Due to problems with description of 1-diff cross-sections neither of MB approaches was ever used to extract N* parameters from the 2p photo and electroproduction data.

  10. New prospects for N* studies in 2p production. Effective lagrangians + phenomenological parametrization hybrid approach. ELSA, MAMI, GRAAL photo- and CLAS electroproduction data extended amount of measured observables considerably. CLAS electroproduction data. For unpolarized beam/target, the final state, gr,v→p-p+p reaction offers 9 independent 1-differential cross-sections in each (W&Q2) bin. All these cross-sections are available from CLAS for the first time. Contributing mechanisms may be established in phenomenological analysis of all available data combined. It is joint JLAB/MSU effort.

  11. JLAB-MSU model (JM05) for 2-p electroproduction.V.I. Mokeev, V.D.Burkert et.al., Proc. of the Workshop NSTAR2005, World scientific, p.47 Quasi-2-body mechanisms included 3-body processes • All well established N* with pD decays +P33(1600)&P11(1710)&P13(1720)&P33(1920) 3-star states and 3/2+(1720) candidate. • Reggetiezed Born terms & effective FSI&ISI treatment (Ref. 11 p.5). • extra pD contact term • All well established N* with rp decays • +P11(1710)&P13(1720) 3-star states and 3/2+(1720) candidate. • Diffractive ansatz for non-resonant part & r-line shrinkage in N* region.

  12. con’d 3-body processes Quasi-2-body mechanisms included (p-) • for p+D013(1520) set of Born terms similar • to what was used for pD isobar channels. • for p+F015(1685), p-P++33(1640) 3-body contact term with exponential propagators of isobars in 2 body intermediate states. (P++33(1640)) (p+) F015(1685) Direct 2p production. Exchange processes, parameterized as:

  13. Evidences for processes beyond isobar channel superposition in 2p production. CLAS data M.Ripani, V.D.Burkert, et. al. Q2=0.95 GeV2 2p direct mechanisms The contributions from all isobar channels combined still underestimate 2p cross-sections. 2p direct mechanisms are needed to reproduce CLAS/world data.

  14. Evidences for exchange mechanisms in direct 2p production from the CLAS data. E93-006 CLAS data fit with remaining mechanisms: W=1.49 GeV Q2=0.65 GeV2 Q2=0.95 GeV2 exchange processes 3-body phase space remaining mechanisms shown on slide 6

  15. p+p-p cross-sections off protons from the fit of mass and p- angular distributions within the frameworkof JM05. s, mcbn CLAS data M.Ripani, V.D.Burkert, et. al. Q2=0.65 Gev2 Q2=0.95 Gev2 Q2=1.30 Gev2 Reasonable description of invariant mass and p- angular distributions were achieved without any need for an additional mechanisms beyond implemented to JM05. W, GeV

  16. Global fit of complete set of unpolarized 1-differential cross-sections within the framework of JM06 model (1.3<W<1.6 GeV & 0.25<Q2<0.60 GeV2) . JM06 full p-D++ p+D0 2p direct ai-angular distributions were calculated with parameters of JM06 fitted to 6 other 1-diff. cross-sections. Preliminary Successful description of all E94-005 data was achieved. Complete data on unpolarized 1-differential cross-sections for the first time available from CLAS allowed us to establish all significant mechanisms contributing to the 2p electroproduction.

  17. Modification of parameterization for direct 2 amplitudes JM05 JM06 JM06 +

  18. P11(1440) and D13(1520) electrocouplings. P11(1440) D13(1520) Preliminary from analysis of E94-005 CLAS 2p data within the framework of JM06 from analysis of 1p CLAS data from analysis of E93-006 CLAS 2p data within the framework of JM05 combined analysis of 1p/2p CLAS data

  19. Combined analysis of major exclusive electroproduction channels within the framework of the coupled channel (cc) approach, using phenomenological input from JM06 Argonne-Osaka approach (T-S.H.Lee, et.al.) is only available worldwide, capable to account for full complexity of FSI in the ppN final states. resulting AO amplitudes “bare” amplitudes, established within the framework of JM06 “bare’ amplitudes from other electroproduction channels ppN unitarity cut

  20. Current efforts in combined 1p/2p analysis. Hall B group & EBAC collaboration. • The amplitudes of all significant mechanisms in the 1p/2p exclusive channels were determined in phenomenological analysis of the CLAS data • (I. Aznauryan for 1p, JM06 for 2p). Modification of these amplitudes by FSI, is under evaluation, using AO approach at 0.25< Q2<1.5 GeV2 and W<1.5 GeV, where only 1p/2p channels contribute • 1p/2p CLAS electroproduction data will be re-fitted, using non-resonant amplitudes accounting for FSI. Clobal fit of observables from major exclusive channels, accounting for unitarity, will be gradually extended up to 2.0 GeV W, allowing us to extract most reliable data on electrocouplings for an entire excited nucleon spectrum. • Studies of underlying MB/partonic mechanisms for remaining JM06 phenomenological terms will be carried out. • Expected outcome: • MB vertex off-shell behavior → input for lattice simulation(?); • Understanding of the transition from MB mechanisms to pDrp GPD’s,/other partonic processes needed for N* studies at high Q2.

  21. What mechanisms behind JM06 phenomenological terms? JM06 phenomenological terms will be replaced by MB amplitudes, derived from modern effective Lagrangians of the outlined approach + residual phenomenological contributions, if any. S.Capstick, T.-S.H.Lee, A. Kiswandhi model For particular mechanisms isolated in JM06 the sum is rather limited

  22. Conclusions. • Considerable extension of the data on 2p photo- and electro- production from recent experiments, carried out worldwide on continues beams with 4p detectors, open up new opportunities for N* studies. Global analysis of full set of unpolarized observables for the first time available from CLAS, allowed us to develop the JM06 model with most complete accounting for all significant mechanisms. These studies demonstrated capability to map-out all sizeable mechanisms from the fit of various observables combined. The amplitudes, determined for all contributing mechanisms, provide necessary input for extraction of N* parameters in the cc analyses. • Global analysis of observables from major photo- / electro- production channels combined, implementing unitarity within the framework of most advanced Argonne-Osaka approach, offers promising way for credible N*/non-resonant processes separation. Therefore, all necessary tools are available to extract reliable values of N* electrocouplings, at various photo virtualities Q2 and to improve knowledge of N* hadronic parameters. • 2p exclusive channels offer very reach information both on resonant and non-resonant processes, vital for modern hadronic physics. Wealthy of this information may be accessed only in combined efforts, including phenomenological mapping of contributing mechanisms, comprehensive FSI treatment and the studies of actual mechanisms behind phenomenology within the framework of meson-baryon and partonic degrees of freedom.

  23. BACK-UP

  24. Modeling of 2p production by tree level meson-baryon diagrams. • Set of tree level meson-baryon diagrams. Particular meson and baryon states were implemented based on: • manifestation of unstable particles in invariant mass distributions; • established in analysis 1p production and experiments with pion beams; • needs to improve description of particular data features. • Full sets of diagrams were created, applying all possible permutations for meson/baryon legs

  25. Fit of E94-005 CLAS 2p data (L.Elouadrhiri, G.Fedotov, et. al.) collected at low W&Q2 within the framework of JM05 model. full p-D++ p+D0 2p direct JM05 succeeded to describe p+p, p-p+ p-pmass and p- angular distributions, Preliminary Failure in description of p+ and pf angular distributions, revealed necessity to modify direct 2p production mechanisms.

  26. General problems of MB approaches. • Available MB models are unable to establish all significant mechanisms contributing to the 2p production due to lack of guidance from fundamental theory and insufficient amount of analyzed observables to determine complexity of contribution processes from the data fit. • Most of MB vertex function are unknown and may be only fitted to the data. • FSI were either neglected or treated in oversimplified approximations. Comprehensive approach for description of FSI complexity in the 3 body ppN final state was needed. Such approach has been developed just recently by Argonne-Osaka collaboration (see T-S.H.Lee talk, hep-th/0608051). Neither of MB approaches was ever used to extract N* parameters from the 2p photo and electroproduction data.

  27. An additional contact terms in pD channels needed to fit data. 2 =1.64 GeV2

  28. The amplitudes for gpp+F015(1685) and gpp-P++33(1600) channels.

  29. Fit of single differential cross-sections from E93-006 experiment within the framework of JM05. Full calculations gpp-D++ gpp+D0 gpp+D13(1520) gprp gpp-P33++(1640) gpp+F150(1685) direct 2p production

  30. Selected p-p+p cross-sections calculated within the framework of JM05, most closed to the E93-006 CLAS data. p+ p, p-p+, p -p invar. masses and p- angular distributionswere fitted within the framework of JM05 (V.Mokeev et.al. , Proc. of NSTAR2005 Workshop, p.47) Q2=0 65GeV2 experimetal data from M.Ripani et. al. , Phys. Rev. Lett.91, 022002 (2003) Q2=0 95GeV2 Q2=1 30 GeV2

  31. Evidence for complementary contributions to pD isobar channels. JM05 full: W=1.76 GeV Q2=0.95 GeV2 extra contact term in pD channels p+D0 on off ds/dM, mcbn/GeV gp→p+D0: extra contact term in pD channels off on W=1.81 GeV Q2=0.95 GeV2 p-p mass, GeV p+p mass, GeV

  32. Manifestation of gp→p-P33++(1640) and gp→p+F15(1685) isobar channels. W=1.89 GeV Q2=0.95 GeV2 JM05 full gp→p+F15(1685) p-P33++(1640) and p+F15 (1685) isobar channels off gp→p-P 33(1640) Contribution from isobar channels: p-P33++(1640) p+F15(1685)

  33. Resonant/non-resonant mechanism separation. full JM06 calculations non-resonant part resonant part Preliminary Combined fit of all unpolarized 1-diff. cross-sections allows us to isolate resonant/non-resonant parts, exploiting difference in shapes of their cross-sections.

  34. Total p-p+p cross-sections calculated within the framework of JM06, most closed to the preliminary CLAS data at 0.25<Q2<0.60 GeV2 and W<1.57 GeV. preliminary CLAS data, exper.E94-005, L.Elouadrhiri, G.Fedotov, et.al. Preliminary

  35. High lying N* electrocouplings. D33(1700), P13(1720) resonances mostly decay with 2p emission. 1p data do not have enough sensitivity to these states. D33(1700) D33(1700) First preliminary data on Q2-evolution of S31(1620), D13(1700), D33(1700), P13(1720) electromagnetic form factors were obtained from analysis of CLAS E93-006 experiment on 2p electroproduction. P13(1720) P13(1720)

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