1 / 35

Nucleon resonance electrocouplings in the non- perturbative regime

Nucleon resonance electrocouplings in the non- perturbative regime. VI. International Conference on Quarks and Nuclear Physics. Philip L Cole Idaho State University April 17, 2012. Palaiseau (France). L 2I 2J. N*. L. Motivation. J.J.Dudek and R.G.Edwards, Hybrid Baryons in QCD

francis-conley
Download Presentation

Nucleon resonance electrocouplings in the non- perturbative regime

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Nucleon resonance electrocouplingsin the non-perturbative regime VI International Conference on Quarks and Nuclear Physics Philip L ColeIdaho State UniversityApril 17, 2012 Palaiseau (France)

  2. L2I 2J N* L Motivation J.J.Dudek and R.G.Edwards, Hybrid Baryons in QCD arXiv:1201.2349[hep-ph] (January 10, 2012)

  3. Photo & Electroproduction • Difficulties (New Opportunities) • Access to N* structure • Non-perturbative strong interactions responsible for formation of N*s • A lot of resonances could be present in a relatively narrow energy region • Nonresonance background is almost equally as complicated • Experiments • Jefferson Lab (USA) • MAMI (Germany) • ELSA (Germany) • ESRF (France) • SPring-8 (Japan) • BES (China) ¶ ¶A unique way of studying the baryon spectrum and N* hadronic decays is via BES: J/ψN*,…

  4. CLAS and JLab

  5. Studying N*s gives insight into structure • Active degrees of freedom in baryon structure at various distance scales. The 6 GeV Program offers detailed information on the transition in N* structure from a superposition of meson-baryon and quark degrees of freedom to the quark-core dominance • Quark core regime The quark core of the nucleon is especially important since N* properties are determined through interactions between dressed-quarks at distances larger than those most important to the structure of ground states. • gvNN* electrocouplings at the higher Q2 Is dynamical chiral symmetry breaking in QCD the root cause for generating the vast bulk of the mass of observable matter in the universe? Indeed in the words of the theorist, Craig Roberts: “there is no greater challenge in the Standard Model, and few in physics, than learning to understand the truly non-perturbative long-range behavior of the strong interaction.”

  6. Electromagnetic Excitation of N*s The experimental N* Program has two major components:1) Transition helicity amplitudes of known resonances to study their internal structure and the interactions among constituents, which are responsible for resonance formation.2) Spectroscopy of excited baryon states, search for new states. • Both parts of the program are being pursued in various meson photo and electroproduction channels, e.g. Nπ, pη, pπ+π-, KΛ, KΣ, pω, pρ0using cross sections and polarization observables. • Global analysis of ALL meson photo- and electroproduction channels – within the framework of an advanced coupled-channel approach developed by EBAC (Excited Baryon Analysis Center – JLab).

  7. Physics Goals for CLAS6 Measure differential cross sections and polarization observables in single and double pseudo-scalar meson production: p+n, p0p, hp, KY, and p+p-p over the full polar and azimuthal angle range. Determine the transition form factors (i.e. electrocouplings) of prominent excited nucleon states (N*, Δ*) and their evolution in the range Q2 < 5 GeV2. Measure N* structure and its evolution with distance through the transition regime. Going from the “constituent quark region” of combined contributions of  meson-baryon dressing and quark core at Q2 < 1.0 GeV2 to quark-core dominance at Q2 > 5.0 GeV2.

  8. Announcement of Firsts from CLAS • First electroproduction data: • channels: p+n, p0p, and hp • Q2 evolution information on the gvNN* electrocouplings for the states: P33(1232),P11(1440),D13(1520), and S11(1535) for Q2 < 5.0 GeV. • I.G. Aznauryan et al., (CLAS Collaboration) Phys. Rev. C80, 055203 (2009). • We recently published the preliminary (first) results on the electrocouplings of the states P11(1440), D13(1520), S31(1620), P13(1720), and D33(1780) at Q2 < 0.6 GeV2 in Npp electro-production from protons • V.I. Mokeev, I.G. Aznauryan, V.D. Burkert, arXiv:1109.1294 [nucl-ex] + • I.G. Aznauryan, V.D. Burkert, V.I. Mokeev, arXiv:1108.1125 [nucl-ex]

  9. Summary of the CLAS data on single-pionelectroproduction off protons Number of data points >116000, W<1.7 GeV, 0.15<Q2<6.0 GeV2 , almost complete coverage of the final state phase space. • Low Q2 results: • I. Aznauryanet al., • PRC 71, 015201 (2005); • PRC 72, 045201 (2005). • High Q2 results on Roper: • I. Aznauryanet al., • PRC 78, 045209 (2008). • Final analysis: • I.G.Aznauryan, V.I Mokeev, • V.D. Burkert (CLAS Collaboration), • PRC 80. 055203 (2009). All datasets can be found in: http://clasweb.jlab.org/physicsdb/

  10. CLAS data on meson electro-production at Q2 < 4.0 GeV2 • Np/Npp channels are the two major contributors in N* excitation region; • these two channels combined are sensitive to almost all excited proton states; • they are strongly coupled by pN→ppN final state interaction; • may substantially affect exclusive channels having smaller cross sections, such as hp,KL, and KS. Why Np/Nppelectroproduction channels are important Therefore knowledge on Np/Npp electroproduction mechanisms is key for the entire N* Program

  11. How N* electrocouplings can be accessed • Isolate the resonant part of production amplitudes by fitting the measured observables within the framework of reaction models, which are rigorously tested against data. • These N* electrocouplings can then be determined from resonant amplitudes under minimal model assumptions. p, h, pp,.. p, h, pp,.. e’ γv γv e lgp=1/2 N*,△ + gv N N’ N’ N N lgp=3/2 A3/2, A1/2, S1/2 GM, GE, GC Non-resonant amplitudes. Consistent results on N* electrocouplings obtained in analyses of various meson channels (e.g. πN, ηp, ππN) with entirely different non-resonant amplitudes will show that they are determined reliably Advanced coupled-channel analysis methods are being developing at EBAC: B.Julia-Diaz, T-S.H.Lee et al., PRC76, 065201 (2007);T.Sato and T-S.H.Lee arXiv:0902.353[nucl-th]

  12. G.V.Fedotov et al., PRC 79 (2009), 015204 M.Ripani et al., PRL 91 (2003), 022002 p+D0 p+F15(1685) p+D13(1520) Full JM calc 2p direct rp p-D++ • Any contributing mechanism has considerably different shapes of cross sections in various observables defined by the particular behavior of their amplitudes. • A successful description of all observables allows us to check and to establish the dynamics of all essential contributing mechanisms. JM Mechanisms as Determined by the CLAS 2p Data

  13. LQCD/DSE q quark mass (GeV) e.m. probe Hadron Structure with Electromagnetic Probes p,r,w,.. Allows to address central question: What are the relevant degrees-of-freedom at varying distance scale? resolution of probe N,N*,D,D* low 3-q core+ MB cloud 3-q core pQCD high

  14. GD= 1 (1+Q2/0.71)2 Data from exclusive π0 production One third of G*M at low Q2 is due to contributions from meson–baryon (MB) dressing: Effects of Meson-Baryon Dressing bare quark core Q2=5GeV2 Within the relativistic Quark Model framework [B.Julia-Diaz et al., PRC 69, 035212 (2004)], the bare-core contribution is reasonably described by the three-quark component of the wavefunction

  15. The P11(1440) electrocouplings from the CLAS data Quark models: I. Aznauryan LC S1/2 S. Capstick LC Relativistic covariant approach by G.Ramalho/F.Gross . A1/2 EBAC-DCC MB dressing (absolute values). p+p-p 2010 p+p-p 2011 Np • Consistent values of P11(1440) electrocouplings determined in independent analyses of Np and p+p-p exclusive channels strongly support reliable electrocoupling extraction. • The physics analyses of these resultsrevealed the P11(1440) structure as a combined contribution of: a) quark core as a first radial excitation of the nucleon as a 3-quark ground state, and b) meson-baryon dressing.

  16. The D13(1520) electrocouplings from the CLAS data A3/2 A1/2 S1/2 M.Giannini/E.Santopinto hCQM MB dressing abs val. (EBAC) • at Q2>2.0 GeV2electrocouplings are consistent with D13(1520) structure as three dressedquarks in orbital excitation with L=1 . • sizable meson-baryon cloud at Q2<1.0 GeV2. The data on A1/2 electrocoupling at Q2>2.0 GeV2 for the first time offer almost direct access to quark core. They are of particular interest for the models of N* structure based on QCD .

  17. CLAS12 JLab Upgrade to 12 GeV Forward Tracker, Calorimeter, Particle ID • Luminosity > 1035cm-2s-1 • General Parton Distributions • Transverse parton distributions • Longitudinal Spin Structure • N* Transition Form Factors • Heavy Baryon Spectroscopy • Hadron Formation in Nuclei Solenoid, ToF, Central Tracker

  18. explore the interactions between the dressed quarks, which are responsible for the formation for both ground and excited nucleon states. • probe the mechanisms of light current quark dressing, which is responsible for >97% of nucleon mass. Q2 = 12 GeV2 Physics Objectives in the N* Studies with CLAS12 Approaches for theoretical analysis of N* electrocouplings: LQCD, DSE, Ads/CFT relativistic quark models. See details in the 62-page White Paper of EmNN* JLAB Workshop, October 13-15, 2008: http://www.jlab.org/~mokeev/white_paper/ Aznauryan et al., arXiv:0907.1901[nucl-th] Independent QCD Analyses Line Fit: DSE Points: LQCD Need to multiply by 3p2 to get the Q2 per quark

  19. CLAS12 For the foreseeable future, CLAS12 will be the only facility worldwide, which will be able to access the N* electrocouplings in the Q2regimeof 5 GeV2 to 10 GeV2, where the quark degrees of freedom are expected to dominate. Our experimental proposal “Nucleon Resonance Studies with CLAS12” was approved by PAC34 for the full 60-day beamtime request. http://www.physics.sc.edu/~gothe/research/pub/nstar12-12-08.pdf. Projections for N* Transitions CLAS published CLAS published CLAS PRL subm. CLAS preliminay CLAS12 projected CLAS12 projected

  20. Nucleon Resonance Studies with CLAS12 R. Arndt4, H. Avakian6, I. Aznauryan11, A. Biselli3, W.J. Briscoe4, V. Burkert6, V.V. Chesnokov7, P.L. Cole5, D.S. Dale5, C. Djalali10, L. Elouadrhiri6, G.V. Fedotov7, T.A. Forest5, E.N. Golovach7, R.W. Gothe*10, Y. Ilieva10, B.S. Ishkhanov7, E.L. Isupov7, K. Joo9, T.-S.H. Lee1,2, V. Mokeev*6, M. Paris4, K. Park10, N.V. Shvedunov7, S. Stepanyan6, P. Stoler8, I. Strakovsky4, S. Strauch10, D. Tedeschi10, M. Ungaro9, R. Workman4, and the CLAS Collaboration JLab PAC 34, January 26-30, 2009 Approved for 40 days beamtime Argonne National Laboratory (IL,USA)1, Excited Baryon Analysis Center (VA,USA)2, Fairfield University (CT, USA)3, George Washington University (DC, USA)4, Idaho State University (ID, USA)5, Jefferson Lab (VA, USA)6, Moscow State University (Russia)7, Rensselaer Polytechnic Institute (NY, USA)8, University of Connecticut (CT, USA)9, University of South Carolina (SC, USA)10, and Yerevan Physics Institute (Armenia)11 Spokesperson Contact Person* 21

  21. Theory Support Group V.M. Braun8, I. Cloët9, R. Edwards5, M.M. Giannini4,7, B. Julia-Diaz2, H. Kamano2, T.-S.H. Lee1,2, A. Lenz8, H.W. Lin5, A. Matsuyama2, M.V. Polyakov6, C.D. Roberts1, E. Santopinto4,7, T. Sato2, G. Schierholz8, N. Suzuki2, Q. Zhao3, and B.-S. Zou3 JLab PAC 34, January 26-30, 2009 Argonne National Laboratory (IL,USA)1, Excited Baryon Analysis Center (VA,USA)2, Institute of High Energy Physics (China)3, Istituto Nazionale di Fisica Nucleare (Italy)4, Jefferson Lab (VA, USA)5, Ruhr University of Bochum (Germany)6, University of Genova (Italy)7, University of Regensburg (Germany)8, and University of Washington (WA, USA)9 Open invitation. List is open to any and all who wish to participate! 22

  22. Our CLAS12 experiment will give access to • The electroproduction cross sections and beam-spin asymmetries of pπ, nπ, pηfor W =1.1 – 2.0 GeV, Q2 < 12 GeV2 with full coverage in cosθ*π,ηand φ* π,η; • 9 single differential cross sections of the pπ+π- channels in the energy range W =1.3 – 2.0 GeV, Q2 < 8 GeV2 with full angle coverage • Thus armed, we can extract the electrocouplings for the helicity amplitudes A1/2,A3/2, and S1/2as a function of Q2 for prominent nucleon and Δ states.

  23. The results from our experiment will be used by EBAC and the Theory Support Group for our proposal to provide • access to the dynamics of non-perturbative strong interactions among dressed quarks and their emergence from QCD and the subsequent formation into baryon resonances; • information on how the constituent quark mass arises from a cloud of low-momentum gluons, which constitute the dressing to the current quarks. [This process of dynamical chiral symmetry breaking accounts for over 97% of the nucleon mass] • enhanced capabilities for exploring the behavior of the universal QCD b-function in the infrared regime.

  24. Thank you Beaucoup Je vousremercie de votre attention

  25. BACKUP SLIDES

  26. Dyson-Schwinger Equation (DSE) Approach DSE provides an avenue to relate N* electrocouplings at high Q2 to QCD and to test the theory’s capability to describe the N* formation based on QCD. DSE approaches provide a link between dressed quark propagators, form factors, and scattering amplitudes and QCD. N* electrocouplings can be determined by applying Bethe-Salpeter /Fadeev equations to 3 dressed quarks while the properties and interactions are derived from QCD. By the time of the upgrade DSE electrocouplings of several excited nucleon states will be available as part of the commitment of the Argonne NL and the University of Washington.

  27. Npp Np P11(1440) electrocouplings from the CLAS data on Np/Npp electroproduction Light front models: I. Aznauryan S. Capstick hybrid P11(1440) [Q3g] • Good agreement between the electrocouplings obtained from theNpandNpp channels: Reliable measure of the electrocouplings. • The electrocouplings for Q2 > 2.0 GeV2are consistent withP11(1440) structure as a 3-quark radial excitation. • Zero crossing for the A1/2amplitude has been observed for the first time, indicating an importance of light-front dynamics. • Hypothesis on the hybrid origin of P11(1440) has been ruled out.

  28. Current Status of Lattice QCD N(1440)P11 D(1232)P33 LQCD calculations of the D(1232)P33 and N(1440)P11 transitions have been carried out with large p-masses. By the time of the upgrade LQCD calculations of N* electrocouplings will be extended to Q2 = 10 GeV2 near the physical p-mass as part of the commitment of the JLAB LQCD and EBAC groups in support of this proposal.

  29. JLAB-MSU meson-baryon model (JM) for N* electrocoupling extraction from the p+p-p electroproduction data V. I. Mokeev , V.D. Burkert, T.-S.H. Lee et al., Phys. Rev. C80, 045212 (2009) Isobar channels included: p-D++ 3-body processes: • All well established N*s with pDdecays and 3/2+(1720) candidate. • Reggeized Born terms with effective FSI and ISI treatment (absorptive approximation). • Extra pDcontact term. r0p • All well established N*s with rp decays and 3/2+(1720) candidate. • Diffractive ansatz for non-resonant part and r-line shrinkage in N* region. Unitarized Breit-Wigner anstaz for resonant amplitudes.

  30. JLAB-MSU meson-baryon model (JM) for N* electrocoupling extraction from the p+p-p electroproduction data 3-body processes: Isobar channels included: (p-) (P++33(1640)) • p+D013(1520), p+F015(1685), p-P++33(1640) isobar channels observed for the first time in the CLAS data at W > 1.5 GeV. (p+) F015(1685) Evidence for p+D013(1520) isobar channel in the CLAS p+p-p data full JM results with p+D013(1520) implemented W=1.74 GeV Q2=0.65 GeV2 full JM results without p+D013(1520) and adjusted direct 2p production p+D013(1520) contribution Mp+p, GeV

  31. N* parameters of the JM model and their relationships to the observables Regular Breit-Wigner (BW) ansatz as the start point : amplitudes are related to the partial N* decay widths to the pD or rp final states of definite helicity lf Definition of gvNN* electrocouplings : fdec is the kinematical factor, which depends on resonance spin, mass and abs. CM 3-momenta values of the stable final hadron averaged over the line of unstable final hadron at the running W (p) and at W=MN* (pN*). qf and jf are the CM final stable hadron ermission angles. Gg is N* electromagnetic decay width, qgN* is abs. photon CM 3-momentum value at W=MN*. The A1/2, A3/2, S1/2gvNN* electrocouplings and Glf N* partial decay widths are determined at resonant point W=MN*. The relationships between N* electroproduction amplitudes Tem and gvNN* electrocouplings A1/2, A3/2, S1/2 are obtained imposing the requirement: fully integrated resonant cross section should be described by the relativistic Breit-Wigner formula in a case of single contributing resonance. Exact expressions for the factors fem and fdec can be found in: M.Ripani et al., Nucl. Phys. A673, 220 (2000).

  32. lgp=1/2 gv N lgp=3/2 Electromagnetic Excitation of N*s e’ p, h, pp γv e N*,△ N’ N A3/2, A1/2, S1/2 Ml+/-, El+/-, Sl+/- DOE Milestone 2012 Measure the electromagnetic excitations of low-lying baryon states (<2 GeV) and their transition form factors over the range Q2 = 0.1 – 7 GeV2 and measure the electro- and photo-production of final states with one and two pseudo-scalar mesons.

  33. D13(1520) electrocouplings from the CLAS data on Np/Npp electroproduction • electrocouplings as determined from the Np & Npp channels are in good agreement overall • but the apparent discrepancies for the A3/2 amplitude at Q2 < 0.4 GeV2 will be further investigated in a combined Np/Npp analysis • hypercentric Consituent Quark Model calculations reasonably describe electrocouplings at Q2>2.5 GeV2, suggesting that the 3-quark component is the primary contribution to the structure of this state at high Q2. error bars include systematic uncertainties M.Giannini/ E.Santopinto hyper-centric CQM

  34. Meson-baryon dressing / Quark core contributions in the A1/2 electrocouplings of the P11(1440) & D13(1520) states. Estimates from EBAC for the MB dressing: B.Julia-Diaz et al., PRC 76, 5201 (2007). hypercentric -quark model by M.Giannini Light Front quark model by I.Aznauryan P11(1440) D13(1520) • MB dressing effects have substantial contribution to low lying N* electrouplings at Q2<1.0 GeV2 and gradually decrease with Q2; • Contribution from dressed quarks increases with Q2 and are expected to be dominant at Q2>5.0 GeV2.

  35. Roper resonance in LQCD Includes the quark loops in the sea, which are critical in order to reproduce the CLAS data at Q2<1.0 GeV2 A1/2, S1/2 => F1*, F2* Mπ = 390, 450, 875 MeV L box =3.0, 2.5, 2.5 f H.W. Lin and S.D. Cohen, arXiv:1108.2528 CLAS data • Full LQCD results consistent with CLAS data. • Approaching physical Mp and extending projection operators by creation of multi particle states, LQCD is making progress toward evaluation of gvNN* electrocouplings from the first QCD principles.

More Related