Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction V.I. Mokeev Jefferson Lab NPQCD2014 Workshop V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
Nucleon Resonances in Inclusive Electron Scattering Excited nucleon state spectrum Status of 2014 after updates provided by Total virtual photon cross sections analyses of the recent exclusive meson F. Foster and G.Hughes, Rep. Progr. photoproduction data from JLAB, ELSA, Phys. 46, 1445 (1983). MAMI, GRAAL, LEPS (V. D. Burkert, Int. J. Q 2 , Mod. Phys. Conf. Ser.,26, 1460050 (2014)). 1000 GeV 2 The peak content 0.1 D 1232)3/2 + 0.5 100 s , mcbn 1.3 N(1440)1/2 + , N(1520)3/2 - , 2.3 N(1535)1/2 - , D (1620)1/2 - 3.3 5.0 10 N(1650)1/2 - , N(1685)5/2 + , 6.0 D (1700)3/2 - , N(1710)1/2 + , N(1720)3/2 + , Quantum excitations of nucleon constituents 3/2 + (1720). (infinite amount of current quarks and gauge gluons) should generate the spectrum of 2.0 1.2 1.5 excited N*-states. W, GeV Data on all essential exclusive meson electroproduction channels are needed in order to determine parameters of prominent nucleon resonances. V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
N* Studies in Exclusive Meson Electroproduction with CLAS Our experimental program seeks to determine g v NN* electrocouplings at photon virtualities up to 5.0 GeV 2 for most of the excited proton states through analyzing major meson electroproduction channels independently and in global multi-channel analyses. Unique source of information on different manifestations of the non-perturbative strong interaction in the generation of different excited nucleons and their emergence from QCD. See details in the review papers: 1. I.G. Aznauryan and V.D. Burkert, Prog. Part. Nucl. Phys. 67, 1 (2012). 2. I.G. Aznauryan et al., Int. J. Mod. Phys. E22, 133015 (2013). 3. I. C. Cloët and C. D. Roberts, Prog. Part. Nucl. Phys, 77, 1 (2014). 4. A. Bashir et al., Comm. Theor. Phys. 58, 79 (2012 ). V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain .
Dynamical Constituents of the Ground and Excited Nucleons Emergence of dressed dynamical quarks: quark/gluon confinement D.Q. N/N* states as the bound systems of dressed dynamical quarks: D.Q. D.Q. D.Q. • more than 98% of dressed quark (N/N*) masses as well as their dynamical structure are generated non-perturbatively through dynamical chiral symmetry breaking (DCSB). The Higgs mechanism accounts for less than 2% of the nucleon and N* mass. • the momentum dependence of the dressed quark mass reflects the transition from quark/gluon confinement to asymptotic freedom. V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
Mapping Dressed Quark Mass Function from the Results on Elastic and Transition g v NN* Electrocouplings I.C.Cloët, C.D.Roberts, A.W.Thomas , Quark mass Phys. Rev. Lett. 111, 101803 (2013). function • data on elastic form factors at Q 2 >5.0 GeV 2 are sensitive to momentum dependence of quark mass function. • mass function should be the same for dressed quarks in the ground and excited nucleon states. • consistent results on dressed quark mass function determined from the data on elastic form factors and transition g v NN* electrocouplings are critical for reliable extraction of this quantity. m p G E /G M (Q 2 ) in DSEQCD . Mapping dressed quark mass function addresses the most challenging problems of hadron physics: • how >98% of hadron masses are generated non-perturbatively? • how quark-gluon confinement in baryons emerges from QCD? V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
Definition of g v NN* electrocouplings and basics for their extraction from the data on exclusive meson electroproduction off nucleons Resonant amplitudes Non-resonant amplitudes p, h, pp ,.. e’ p, h, pp,.. γ v e N*, △ * + N ’ N N ’ N • A 1/2 (Q 2 ), A 3/2 (Q 2 ), S 1/2 (Q 2 ) N*’s photo -/electrocouplings g v NN* are defined See details in: or at W=M N* through the N* electromagnetic I.G.Aznauryan and • G 1 (Q 2 ), G 2 (Q 2 ), G 3 (Q 2 ) decay width g : V.D.Burkert, Progr. or 2 Part. Nucl. Phys. q • G M (Q 2 ), G E (Q 2 ), G C (Q 2 ) g 2 M 67, 1 (2012). 2 2 N A A r g p 1 / 2 3 / 2 ( 2 1 ) J M r N * • Separation of resonant/non-resonant contributions within the framework of reaction models; Breit Wigner ansatz for parameterization of resonant amplitudes; fit of resonance electroexcitation and hadronic parameters to the data. • Consistent results on g v NN* electrocouplings from different meson electroproduction channels and different analysis approaches demonstrated reliable extraction of N* parameters. V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
CEBAF Large Acceptance Spectrometer Torus magnet Large angle calorimeters 6 superconducting coils Lead/scintillator, 512 PMTs Liquid D 2 (H 2 )target + g start counter & minitorus Gas Cherenkov counters Drift chambers e/ p separation, 216 PMTs argon/CO 2 gas, 35,000 cells Electromagnetic calorimeters Time-of-flight counters Lead/scintillator, 1296 PMTs plastic scintillators, 684 PMTs The unique combination of the CEBAF continuous electron beam and the CLAS detector makes Hall-B@JLAB the only facility operational worldwide, that is capable of measuring unpolarized cross sections and polarization asymmetries of most exclusive meson electroproduction channels with substantial contributions at W<3.0 GeV and Q 2 <5.0 GeV 2 . V.I.Mokeev User Group Meeting June 18 2008
Summary of the CLAS Data on Exclusive Meson Electroproduction off Protons in N* Excitation Region • d s /d W- CM angular Covered Q 2 - Hadronic final Covered Measured range, GeV 2 state W-range, GeV observables distributions • A b ,A t ,A bt -longitudinal C beam, target, and p + n d s /d W 1.1-1.38 0.16-0.36 beam-target asym- d s /d W 1.1-1.55 0.3-0.6 metries d s /d W, A b 1.1-1.7 1.7-4.5 • P 0 P’ – recoil and p 0 p d s /d W 1.1-1.38 0.16-0.36 transfered polarization d s /d W, A b ,A t ,A bt 1.1-1.68 0.4-1.8 of strange baryon d s /d W 1.1-1.39 3.0-6.0 h p d s /d W 1.5-2.3 0.2-3.1 Almost full coverage K + L d s /d W thresh-2.6 1.40-3.90 of the final hadron 0.70-5.40 P 0 , P’ phase space in p N, p + p - p, h p, and KY K + S 0 d s /d W thresh-2.6 1.40-3.90 electroproduction thresh-2.6 0.70-5.40 P’ The data are p + p - p 1.3-1.6 0.2-0.6 Nine 1-fold available in the 1.4-2.1 0.5-1.5 differential CLAS Physics cross sections Data Base: http://depni.sinp.msu.ru/cgi-bin/jlab/db.cgi V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
N* Electroexcitation in Exclusive Meson Electroproduction off Protons Hadronic decays of prominent N*s at W<1.8 GeV CLAS data on yields of meson electroproduction at Q 2 <4 GeV 2 State Bran. Fract. Bran. Fract. Bran.Fract. to N p . to N h Nππ Δ (1232)P 33 0.995 N(1440)P 11 0.3-0.4 0.55-0.75 0.55-0.65 0.4-0.5 N(1520)D 13 N(1535)S 11 0.48±0.03 0.46±0.02 0.20-0.30 0.70-0.80 D (1620)S 31 N(1650)S 11 0.60-0.95 0.03-0.11 0.1-0.2 N(1685)F 15 0.65-0.70 0.30-0.40 0.1-0.2 0.8-0.9 Δ(1700)D 33 N(1720)P 13 0.1-0.2 > 0.7 N p /N pp channels are major and complementary sources of information on g v NN* electrocouplings of most resonances with masses up to 1.8 GeV V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
Approaches for Extraction of g v NN* Electrocouplings from the CLAS Exclusive Meson Electroproduction Data • Analyses of different pion electroproduction channels independently: p + n and p 0 p channels: Unitary Isobar Model (UIM) and Fixed-t Dispersion Relations (DR) I.G.Aznauryan, Phys. Rev. C67, 015209 (2003). I.G.Aznauryan et al., CLAS Coll., Phys Rev. C80, 055203 (2009). h p channel: Extension of UIM and DR I.G.Aznauryan, Phys. Rev. C68, 065204 (2003). Data fit at W<1.6 GeV, assuming S 11 (1535) dominance H.Denizli et al., CLAS Coll., Phys.Rev. C76, 015204 (2007). p + p - p channel: Data driven JLAB-MSU meson-baryon model (JM) V.I.Mokeev, V.D.Burkert et al., Phys. Rev. C80, 045212 (2009). V.I.Mokeev et al., CLAS Coll., Phys. Rev. C86, 035203 (2012). Global coupled-channel analyses of the CLAS/world data of p N, g r,v N → p N, h N, pp N, K L , K S exclusive channels: T.-S. H. Lee , AIP Conf. Proc. 1560, 413 (2013). H. Kamano et al., Phys. Rev. C88, 035209 (2013). V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
The Approaches for Extraction of g v NN* Electrocouplings from N p Exclusive Electroproduction off Protons Unitary Isobar Model (UIM) The Model based on fixed-t Dispersion Relations (DR) p p • the real parts of invariant N p electroproduction amplitudes are computed from their imaginary parts employing fixed-t dispersion relations; N N • the imaginary parts of the N p electroproduction amplitudes at p p N W>1.3 GeV are dominated by p w,r,p resonant parts and were computed N from N* parameters fit to the data. p N p + I. G. Aznauryan, Phys. Rev. C67, 015209 (2003), I.G.Aznauryan, V.D.Burkert, et al. (CLAS Collaboration), PRC 80. 055203 (2009). V.I.Mokeev, NPQCD14 Workshop 30-th September – 4-th October 2014, Huelva, Spain
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