Can Transition Formfactors Reveal Diquark Correlations? Ralf W. - PowerPoint PPT Presentation

Can Transition Formfactors Reveal Diquark Correlations? Ralf W. Gothe for the CLAS Collaboration Diquark Correlations in Hadron Physics: Origin, Impact and Evidence September 23-27, 2019, ECT*, Trento, Italy  γ v NN* Experiments: The best access to the baryon and quark structure?  Analysis and New Results: Exclusive, quasi-free, and final state interaction!  Outlook: New experiments with extended scope and kinematics! This work is supported in parts by the National Science Foundation under Grant PHY 1812382. 1 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Can Transition Formfactors Reveal Diquark Correlations? Ralf W. Gothe for the CLAS Collaboration Diquark Correlations in Hadron Physics: Origin, Impact and Evidence September 23-27, 2019, ECT*, Trento, Italy  Are dressed quarks fictious model creatures? Do we have evidence that they exist?  Why are quarks in DIS pointlike? What is the difference between a large-x valence quark and a dressed quark?  When does (precocious) scaling set in? What does it mean? This work is supported in parts by the National Science Foundation under Grant PHY 1812382. 2 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Spectroscopy 3 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Quark Model Classification of N* Dietmar Menze L P + q³g D 13 (1520) + q³qq S 11 (1535) J + N-Meson + … ∆ (1232) Roper P 11 (1440) 1135 MeV 1545 MeV 1839MeV 2130 MeV Mass 4 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

N and ∆ Excited Baryon States … Simon Capstick  Orbital excitations (two distinct kinds in contrast to mesons)  Radial excitations (also two kinds in contrast to mesons) 5 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Build your Mesons and Baryons … ? Frank Wilczek, Physics Today, August 2000 6 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Electron Scattering 7 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Baryon Excitations and Quasi-Elastic Scattering Paticle and Nuclei, Povh et al., MAMI B Elastic Peak of H E = 246 MeV θ = 148 o Quasi-Elastic Peak in 16 O Deep Inelastic Scattering S. Stein et al., PR D22 (1975) 1884 8 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Quark-Hadron Duality PRL 16 (1970) 1140, PR D4 (1971) 2901 E.D. Bloom and F.J. Gilman W = 1.9 GeV E’ = 17.6 GeV ν = 2.37 GeV Q 2 = 1.72 GeV m q = Q 2 /2 ν m q = 0.36 GeV p F = 0.67 GeV ∆ r F =  c * √9 π /2 r F = 0.79 fm ∆ p F Deep Inelastic Scattering S. Stein et al., PR D22 (1975) 1884 9 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Baryon Excitations and Quasi-Elastic Scattering quasi-elastic off point-like constituents Deep Inelastic Scattering M. Breidenbach et al., Phys. Rev. Lett. 23 (1969) 935 10 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Baryon Excitations and Quasi-Elastic Scattering hard and confined quasi-elastic e - hard soft Deep Inelastic Scattering S. Stein et al., PR D22 (1975) 1884 11 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Transition Form Factors 12 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Hadron Structure with Electromagnetic Probes  Study the structure of the nucleon spectrum in the domain Q 2 π,ρ,ω … where dressed quarks are the major active degree of freedom.  Explore the formation of excited nucleon states in interactions low of dressed quarks and their emergence from QCD. k N,N * , ∆,∆ * … 3q-core+MB-cloud K 2 µ N P 2 µ * Q 2 = − K µ 2 3q-core K 1 µ N P 1 µ not high pQCD 13 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Hadron Structure with Electromagnetic Probes  Study the structure of the nucleon spectrum in the domain Quark mass extrapolated to the chiral limit, where q Q 2 π,ρ,ω … where dressed quarks are the major active degree of freedom. is the momentum variable of the tree-level quark low propagator using the Asqtad action. q N,N * , ∆,∆ * … meson dressed quark LQCD, DSE and … 3q-core+MB-cloud quark mass (GeV) confinement current quark 3q-core e.m. probe high pQCD 14 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Hadron Structure with Electromagnetic Probes  The SM α s diverges as Q 2 approaches zero, but confinement and the meson cloud heal this artificial divergence as QCD Q 2 π,ρ,ω … k becomes non-perturbative. low N,N * , ∆,∆ * … 3q-core+MB-cloud 3q-core high pQCD 15 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Hadron Structure with Electromagnetic Probes Rolf Ent  The pion, or a meson cloud, explains light-quark asymmetry Q 2 π,ρ,ω … of the sea quarks in the nucleon. low k N,N * , ∆,∆ * … 3q-core+MB-cloud 3q-core high pQCD 16 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Data-Driven Data Analyses QCD Consistent Results Single Pion DSE, QM N*, Δ * LQCD Amplitude Reaction Models analysis Data Hadronic Electromagnetic Int. J. Mod. Phys. E, Vol. 22, 1330015 (2013) 1-99 production production 17 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Data-Driven Data Analyses QCD Consistent Results Double Pion DSE, QM N*, Δ * LQCD Amplitude Reaction Models analysis Data Hadronic Electromagnetic Int. J. Mod. Phys. E, Vol. 22, 1330015 (2013) 1-99 production production 18 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Data-Driven Data Analyses QCD Consistent Results DSE, QM N*, Δ * LQCD  Single meson production: Unitary Isobar Model (UIM) Fixed- t Dispersion Relations (DR) Amplitude  Double pion production: Reaction Models analysis Unitarized Isobar Model (JM)  Coupled-Channel Approaches: EBAC ⇒ Argonne-Osaka JAW ⇒ Jülich-Athens-Washington ⇒ JüBo Data BoGa ⇒ Bonn-Gatchina Hadronic Electromagnetic Int. J. Mod. Phys. E, Vol. 22, 1330015 (2013) 1-99 production production 19 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Electrocouplings of N(1440)P 11 History 10 -3 GeV -1/2  Lowest mass hybrid baryon should be J P =1/2 + as Roper.  In 2002 Roper A 1/2 results were consistent with a hybrid state. 20 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Transition Form Factors and QCD Models Roper resonance P 11 (1440) PDG 2013 update nrQM + q³g MAID LC QM + q³qq + N-Meson - q 2 q + … or q 3 G - … … all have distinctively different Q 2 dependencies  A 1/2 has zero-crossing near Q 2 =0.5 and becomes dominant amplitude at high Q 2 .  Consistent with radial excitation at high Q 2 and large meson-baryon coupling at small Q 2 .  Eliminates gluonic excitation (q 3 G) as a dominant contribution. Nick Tyler closes the 1-2 GeV 2 gap for single pion production. 21 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Transition Form Factors and QCD Models Roper resonance P 11 (1440) I.T. Obukhovsky nrQM MAID LC QM q 3 +Nσ q 3 G  A 1/2 has zero-crossing near Q 2 =0.5 and becomes dominant amplitude at high Q 2 .  Consistent with radial excitation at high Q 2 and large meson-baryon coupling at small Q 2 .  Eliminates gluonic excitation (q 3 G) as a dominant contribution. Nick Tyler closes the 1-2 GeV 2 gap for single pion production. 22 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Transition Form Factors and QCD Models Roper resonance P 11 (1440) G. Ramalho CSQM LF Holography  A 1/2 has zero-crossing near Q 2 =0.5 and becomes dominant amplitude at high Q 2 .  Consistent with radial excitation at high Q 2 and large meson-baryon coupling at small Q 2 .  Eliminates gluonic excitation (q 3 G) as a dominant contribution. Nick Tyler closes the 1-2 GeV 2 gap for single pion production. 23 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019

Roper Transition Form Factors in DSE Approach N(1440)P 11 J. Segovia et al., Phys. Rev. Lett. 115 , 171801 CLAS Data CLAS Data DSE Contact Radial excitation … DSE Realistic longer tail … r R /r p =1.8 Inferred meson-cloud contribution … color must be screened … greater Anticipated complete result need for a meson- baryon cloud! Importantly, the existence of a zero in F 2 is not influenced by meson-cloud effects, although its precise location is. 24 Ralf W. Gothe ECT* 2019, Trento, Italy September 23-27, 2019