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I. G. Aznauryan Jefferson Lab Yerevan Physics Institute October 13, 2008, Jlab

Electroexcitation of P 11 (1440), D 13 (1520), and S 11 (1535) from CLAS data and quark model predictions. On the definitions of the g * p N * helicity amplitudes. I. G. Aznauryan Jefferson Lab Yerevan Physics Institute October 13, 2008, Jlab

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I. G. Aznauryan Jefferson Lab Yerevan Physics Institute October 13, 2008, Jlab

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  1. Electroexcitation of P11(1440), D13(1520), and S11(1535) from CLAS data and quark model predictions.On the definitions of the g*p N* helicity amplitudes I. G. Aznauryan Jefferson Lab Yerevan Physics Institute October 13, 2008, Jlab Electromagnetic N-N* Transition Form Factors Workshop

  2. Outline Resultson the g * pP11(1440), D13(1520), S11(1535)helicity amplitudes extracted from CLAS p and 2p electroproduction data, comparison with earlier data Correct definition of the amplitudes : very important as Q2dependence of the g* NN*amplitudes extracted in wide region of Q2is highly sensitive to different description of Nand N* : - 3q picture - additional qq components - hybrid q3G states - resonances dynamically generated in p N interaction - results of lattice QCD Comparison with quark model predicions Summary

  3. CLAS: the eNeNp data Analysis: DR, UIM I.Aznauryan et al., PR C71 (2005) 015201 PR C72 (2005) 045201 Analysis: DR, UIM I.Aznauryan et al., nucl-exp/0804.0447, will appear in PRC s(epeNp+,0)  14 863 data points: K. Joo et al., PRL 88 (2002) 122001 PR C68 (2003) 032201 PR C70 (2004) 042201 H.Egiyan et al., PR C73(2006) 025204 s(epeNp+)  36 300 data points: K. Park et al., PR C77 (2008) 015208 Q2 = 0.4, 065 GeV2 Q2 = 1.72, 2.05, 2.44, 2.91, 3.48, 4.16 GeV2

  4. CLAS: the epepp+p-data Data: G.Fedotov,V.Mokeev, V.Burkert,… nucl-ex/0809.1562 Combined analysis ofepepp, epepp+p-data: I.Aznauryan, V.Burkert, V.Mokeev et al., PR C72 (2005) 045201 Q2 = 0.65 GeV2 Q2 = 0.275, 0.325, 0.375, 0.425, 0.475, 0.525, 0.575 GeV2 Analysis: V.Mokeev, V.Burkert, J.Phys. Conf.Ser. 69 (2007) 012019; Proc. of NSTAR2007, p. 76

  5. Helicity amplitudes of the g*p P11 (1440) transition CLAS data : Np Np, Npp, combined gppp0 M.Dugger et al., PR C76 025211,2007 Npp (preliminary) First measurements of S1/2 First measurements of A1/2at Q2 > 0 PDG

  6. Helicity amplitudes of the g*p S11 (1535) transition CLAS data : Np gppp0 M.Dugger Nh it is difficult to extract S1/2inh electroproduction First measurements of S1/2 : Results for A 1/2obtained in p and hproduction agree with each other with bp N = 0.45, b hN = 0.52  PDG: bp N = 0.35-0.55, b hN = 0.45-0.6 PDG Slow falloff of A1/2observed in hproduction is confirmed by p data

  7. Helicity amplitudes of the g*p D13(1520) transition CLAS data : Np gppp0 ,M. Dugger Np, Npp, combined Npp(preliminary) Old data: Bonn, DESY, NINA First definite results for A 1/2 , A 3/2 in wide range of Q2 First measurements of S1/2 PDG

  8. Definitions: common sign of the g*p N*amplitudes In the analyses of g*N N pdata, the g*p N*helicity amplitudes are defined through reaction multipole amplitudes. For example, for g*p P11(1440) in g*p p p0 we have: N N* N p g* This definition contains information on signs of two vertices g*NN* andN*Np : g(N*Np)  {G(N*Np)}1/2

  9. Common sign of the g*p N*amplitudes (con-d) Definition of A1/2in theoretical approaches: N N* N Depends on the phase of FN* (FN*)* FN* Contains information on the g*N N* vertex only g* p

  10. Common sign of the g*p N*amplitudes (con-d) A1/2 sign pNN* Commonly used definition of A1/2in quark modelis: R.L.Walker, Proc. of IV Int. Symp. on Electron-Photon Inter. at High Energies, Liverpool (1969), p. 21. Possibly, it will be right to make some changes in conventions to avoid this confusion, for example, to reflect in the amplitude extracted from experiment the final state: A ApN, …? In QM, traditionally, thesign pNN* was chosen to describe the sign of the experimentalA1/2amplitude for Q2=0; sometimes this can bring to confusing and wrong results

  11. Common sign of the g*p N*amplitudes (con-d) For example, for P11 (1440) : We need explicit formulas, how to account for the relative sign of the contributions : , if Born terms: Res.: I.Aznauryan, V.Burkert, H.Lee, nucl-th/0810.0997 Through covariant calculations, we have obtained the relations:

  12. Definition of the g*p N*amplitudes (con-d) Through the g*N N p multipole amplitudes Through the g*N N* electromagnetic current Through the g*N N* form factors In this way, we have also checked, which definition of We have presented different definitions of A1/2, A3/2, S1/2 : These definitions are consistent with each other, and may be useful in theoretical calculations In nonrelativistic quark model gives the sign consistent with the relative sign of the amplitudes extracted from experiment, i.e.S1/2relatively to A1/2, A3/2

  13. Common sign of the g*p N*amplitudes (con-d) For the resonances of [70,1- ] –plet, common signs of the g*p N*amplitudesin quark model were found (using PCAC for the pNN* vertex) by Aznauryan, Bagdasaryan,Sov.J.Nucl.Phys. 41 (1985) 158 For all resonances, except D13(1700), traditionally used sign is right For P11(1440), sign of the g*p N*amplitudes was found using 3Pomodel for the pN N* vertex by Capstick, Keister, PR D51 (1995) 3598 using PCAC for the pN N* vertex by Aznauryan, PR C76 (2007) 025212

  14. Signs for g*p  P11 (1440) 1. strong model dependence 2. for some models strong disagreement with experiment Corrected signs 1. less model dependence 2. better agreement with exp. Signs taken in ‘traditional way’ Light-front RQM Capstick, Keister (1995) Weber, PR C41 (1990)2783 Simula… PL B397 (1997)13 NRQM Warns… Z.Phys. C45 (1990)627 Giannini… J.Phys. G24 (1998)753

  15. g*p  P11 (1440): 3q picture with P11 (1440) as [56,0+]r All LF RQM describe sign change of A1/2 the amplitudeS1/2 LF RQM: Weber, PR C41 (2783) 1990 Capstick, Keister, PR D51 (1995) 3598 Pace, Simula et.al., PR D51 (1995) 3598 Aznauryan, PR C76 (2007) 025212 All LF RQM fail to describe the amplitude A1/2 at Q2 < 1 GeV2 Strong evidence in favor of P11 (1440) as a first radial excitation of 3q ground state

  16. P11 (1440): Additional components and contributions Pion cloud EBAC (preliminary) Julia-Diaz et.al., PR C77(2008)045205 • 30% admixture of • qqqqq components in • the Roper resonance • G(theory) = G(exp) : • Li, Riska, PR C74(2006)015202 Pion cloud contributions and additional qqqqq components in the Roper resonance can improve the description at small Q2

  17. P11 (1440) as a q3G hybrid state P11 (1440) as q3G hybrid state is ruled out !!! Supression of S1/2has its origin in the form of the vertex g*q  qG; it is practically independent of relativistic effects P11 (1440) as q3G: Li, Burkert,Li, PR D46 (1992) 70

  18. g*p D13 (1520): 3q picture + pion cloud In 3q picture, the signs of all amplitudes are described; however, this picture fails to describe A3/2 at small Q2 Significant contribution at small Q2forA3/2 Nonrelativistic approaches: Warnset al., Z.Phys.C45(1990)627 Aiello et.al., J.Phys.G24 (1998)753 Merten…, Eur.Phys.J.A14 (2002)477 Pion cloud: EBAC (preliminary)

  19. g*p S11 (1535): 3q picture Opposite sign of S1/2!!! Impossible to change in quark model !!! Combined with the difficulties in the description of large width of S11(1535)h N and large S11(1535)fN,LKcouplings, this shows that 3q picture for S11(1535) should be complemented LF RQM: Capstick, Keister, PR D51 (1995) 3598 Pace, Simula et.al., PR D51 (1995) 3598

  20. S11 (1535): Additional components and contributions Pion cloud: EBAC (preliminary),MAINZ sign should be consistent with the interference of (uu,dd) and ss components in G(S11 (1535)hp) qq (mostly ss) : An,Zou , nucl-th/0802.3996 It is possible that agreement of 3q picture with experimental data will be achieved by taking into account pion cloud contribution and additionalqqqqq components in S11(1535)

  21. Summary The results for the g* p S11(1535) transverse amplitude extracted from p andhelectroproduction data are consistent with each other For the first time transverse and longitudinal amplitudes of the g* p P11(1440) transition are extracted from experiment for Q2 > 0in wide range of Q2 For the first time longitudinal amplitudes of the g* p D13(1520), S11(1535) transitions are extracted from experiment, and in wide range of Q2 For the first time definite results are obtained for the transverse amplitudes of the g* p D13(1520) transition in wide range of Q2

  22. Summary: P11(1440) Comparison with quark model predictions provides strong evidence in favor of P11(1440) as a first radial excitation of the 3q ground state Pion cloud contributions and additionalqqcomponents in the Roper resonance can improve description of A1/2 at small Q2 Quark model predictions underestimate the value of A1/2 at smallQ2 Presentation of P11(1440) as aq3G hybrid state is ruled out The results for g* p P11(1440)available in wide region of Q2 allow us to make conclusions on the nature of P11(1440):

  23. Summary: D13(1520), S11(1535) There is significant underestimation at small Q2for A3/2 which apparently is related to the pion cloud contribution Quark models predict opposite sign for the S1/2 amplitude of the g* p S11(1535)transition !!! Combined with the difficulties in the description of couplings to hadronic channels, this shows that 3q picture for S11(1535) should be complemented Quark models describe the signs of all amplitudesfor theg* p D13(1520)transition Apparently, agreement of 3q picture with experimental data can be achieved by taking into account pion cloud contribution, and additionalqqqqq components in S11(1535)

  24. Summary: definitions of the g* N N*amplitudes The g* N N*amplitudes extracted from the experimental data on the g* N Np reaction are related to the g* N N*amplitudes calculated in theoretical approaches through the sign of the pNN*vertex Possibly, it makes sense to introduce new conventions in order to avoid confusion caused by this fact

  25. S11 (1535) as a dynamically generated resonance Dynamically generated S11 (1535): Oset… , nucl-th/0712.0038 sign should be checked via calculation of the vertex S11 (1535)pNin addition to g*p S11 (1535) For both signs, presentation of S11 (1535)as only dynamically generated resonance is ruled out. However, it is interesting to investigate the possibility of the dynamically generated resonance as a component additional to 3q state.

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