Measurements of $ep\to e^{\prime }{\pi }^{+}n$ at W = 1.6 - 2.0 GeV and extraction of nucleon resonance electrocouplings at CLAS

Abstract

Differential cross sections of the exclusive process $ep\to e^{\prime }{\pi }^{+}n$ were measured with good precision in the range of the photon virtuality $Q^2=1.8-4.5$ GeV${}^2$, and the invariant mass range of the ${\pi }^{+}n$ final state W = 1.6 - 2.0 GeV using the CEBAF Large Acceptance Spectrometer. Data were collected with nearly complete coverage in the azimuthal and polar angles of the $n{\pi }^{+}$ center-of-mass system. More than 37,000 cross section points were measured. The contributions of the isospin $I=\frac{1}{2}$ resonances $N(1675){\frac{5}{2}}^{-}$, $N(1680){\frac{5}{2}}^{+}$ and $N(1710){\frac{1}{2}}^{+}$ were extracted at different values of $Q^2$ using a single-channel, energy-dependent resonance amplitude analysis. Two different approaches, the unitary isobar model and the fixed-$t$ dispersion relations, were employed in the analysis. We observe significant strength of the $N(1675){\frac{5}{2}}^{-}$ in the $A_{1/2}$ amplitude, which is in strong disagreement with quark models that predict both transverse amplitudes to be strongly suppressed. For the $N(1680){\frac{5}{2}}^{+}$ we observe a slow changeover from the dominance of the $A_{3/2}$ amplitude at the real photon point ($Q^2=0$) to a $Q^2$ where $A_{1/2}$ begins to dominate. The scalar amplitude $S_{1/2}$ drops rapidly with $Q^2$ consistent with quark model prediction. For the $N(1710){\frac{1}{2}}^{+}$ resonance our analysis shows significant strength for the $A_{1/2}$ amplitude at $Q^2<2.5$ GeV${}^2$.

arXiv comment24 pages, 22 figures. arXiv admin note: substantial text overlap with arXiv:0709.1946

References in corpus (51)

• A unitary isobar model for pion photo- and electroproduction on the proton up to 1 GeV
• Unitary Isobar Model - MAID2007
• Excited state baryon spectroscopy from lattice QCD
• Global analysis of proton elastic form factor data with two-photon exchange corrections
• Determination of the Charged Pion Form Factor at Q2=1.60 and 2.45 (GeV/c)2
• Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction
• Dynamical coupled-channel model of meson production reactions in the nucleon resonance region
• Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction
• Electroexcitation of nucleon resonances
• Determination of the pion charge form factor for Q^2=0.60-1.60 GeV^2
• $Q^2$ Dependence of Quadrupole Strength in the ${\gamma }^{\ast }p\to {\Delta }^{+}(1232)\to p{\pi }^0$ Transition
• Dynamical Study of the Delta Excitation in N(e,e' pi) Reactions
• Electromagnetic Meson Production in the Nucleon Resonance Region
• Pion cloud and the $Q^2-$dependence of ${\gamma }^{\ast }N\leftrightarrow \Delta$ transition form factors
• Measurements of the Electric Form Factor of the Neutron up to Q2=3.4 GeV2 using the Reaction He3(e,e'n)pp
• A study of the $P_{11}(1440)$ and $D_{13}(1520)$ resonances from CLAS data on $ep\to e^{\prime }{\pi }^{+}{\pi }^{-}{p}^{\prime }$
• gamma* N -> Delta transition form factors: a new analysis of the JLab data on p(e,e'p)pi0 at Q^2=2.8 and 4.0 (GeV/c)^2
• Empirical transverse charge densities in the nucleon and the nucleon-to-$\Delta$ transition
• The e p -> e' p eta reaction at and above the S11(1535) baryon resonance
• Measurement of the N to Delta(1232) Transition at High Momentum Transfer by pi0 Electroproduction
• A Precise Measurement of the Neutron Magnetic Form Factor GMn in the Few-GeV2 Region
• Q^2 Dependence of the S_{11}(1535) Photocoupling and Evidence for a P-wave resonance in eta electroproduction
• Electroproduction of the S11(1535) Resonance at High Momentum Transfer
• Multipole Amplitudes of Pion Photoproduction on Nucleons up to 2GeV within Dispersion Relations and Unitary Isobar Model
• Dynamical Coupled-Channels Effects on Pion Photoproduction
• Electroexcitation of the P33(1232), P11(1440), D13(1520), S11(1535) at Q^2=0.4 and 0.65(GeV/c)^2
• Electroexcitation of the Roper resonance for 1.7 < Q2 < 4.5 GeV2 in ep -> enpi+
• A chiral bag model approach to delta electroproduction
• A systematic study of longitudinal and transverse helicity amplidutes in the hypercentral Constituent Quark Model
• Nucleon electromagnetic form factors and electroexcitation of low lying nucleon resonances in a light-front relativistic quark model
• Light baryon magnetic moments and N -> Delta gamma transition in a Lorentz covariant chiral quark approach
• Single pi+ Electroproduction on the Proton in the First and Second Resonance Regions at 0.25GeV^2 < Q^2 < 0.65GeV^2 Using CLAS
• Electroexcitation of nucleon resonances at Q^2=0.65 GeV/c^2 from a combined analysis of single- and double-pion electroproduction data
• Recoil Polarization for Delta Excitation in Pion Electroproduction
• Measurement of the Polarized Structure Function ${\sigma }_{L{T}^{\prime }}$ for $p(\vec{e},e^{\prime }p){\pi }^o$ in the $\Delta (1232)$ Resonance Region
• Cross sections and beam asymmetries for $\vev{e}p \to enπ^+$ in the nucleon resonance region for $1.7\le Q^2\le 4.5(GeV{)}^2$
• Lowest Q^2 Measurement of the gamma*p -> Delta Reaction: Probing the Pionic Contribution
• Model Analysis of the $ep\to e{p}^{\prime }{\pi }^{+}{\pi }^{-}$ Electroproduction Reaction on the Proton
• Single Quark Transition Model Analysis of Electromagnetic Nucleon Resonance Transitions in the [70,1-] Supermultiplet
• Valence quark contributions for the gamma N -> P11(1440) form factors
• QED Radiative Corrections in Processes of Exclusive Pion Electroproduction
• Empirical transverse charge densities in the nucleon-to-P11(1440) transition
• A covariant model for the gamma N -> N(1535) transition at high momentum transfer
• Measurement of the Polarized Structure Function ${\sigma }_{L{T}^{\prime }}$ for $p(\vec{e},e^{\prime }{\pi }^{+})n$ in the $\Delta (1232)$ Resonance Region
• Determination of quadrupole strengths in the gamma*p-->Delta(1232) transition at Q2= 0.20 (GeV/c)2
• Electroproduction of p π^{+} π^{-} off protons at 0.2<Q^{2}<0.6 GeV^{2} and 1.3<W<1.57 GeV with CLAS
• Valence quark and meson cloud contributions to the ${\gamma }^{\ast }N\to N^{\ast }(1520)$ form factors
• Separated Structure Functions for Exclusive $K^{+}\Lambda$ and $K^{+}{\Sigma }^0$ Electroproduction at 5.5 GeV with CLAS
• Study of polarized-e polarized-p --> e-prime p pi0 in the Delta(1232) mass region using polarization asymmetries
• Measurement of the R${}_{LT}$ response function for ${\pi }^0$ electroproduction at $Q^2$ = 0.070 (GeV/c)${}^2$ in the $N\to \Delta$ transition}
• First measurement of target and double spin asymmetries for polarized e- polarized p --> e p pi0 in the nucleon resonance region above the Delta(1232)

Cited by in corpus (35)

• Dynamical coupled-channels model for neutrino-induced meson productions in resonance region
• New Results from the Studies of the $N(1440)1/2^{+}$, $N(1520)3/2^{-}$, and $\Delta (1620)1/2^{-}$ Resonances in Exclusive $ep\to e^{\prime }{p}^{\prime }{\pi }^{+}{\pi }^{-}$ Electroproduction with the CLAS Detector
• Nucleon-to-Roper electromagnetic transition form factors at large-$Q^2$
• Strong QCD Insights from Excited Nucleon Structure Studies with CLAS and CLAS12
• Measurements of $ep\to e^{\prime }{\pi }^{+}{\pi }^{-}{p}^{\prime }$ Cross Sections with CLAS at $1.40<W<2.0$ GeV and $2.0<Q^2<5.0$ GeV${}^2$
• Jülich-Bonn-Washington Model for Pion Electroproduction Multipoles
• Electromagnetic Transition Form Factors of Baryon Resonances
• Nucleon resonance contributions to unpolarised inclusive electron scattering
• Transition form factors: ${\gamma }^{\ast }+p\to \Delta (1232)$, $\Delta (1600)$
• Spectrum and structure of octet and decuplet baryons and their positive-parity excitations
• Electroweak pion-production on nuclei within the extended factorization scheme
• Lepton-Nucleus Cross Section Measurements for DUNE with the LDMX Detector
• Nucleon resonances in Compton scattering
• Nucleon resonances with higher spins in soft-wall AdS/QCD
• Electroexcitation of nucleon resonances of the [70,1-] multiplet in a light-front relativistic quark model
• Recent results on the nucleon resonance spectrum and structure from the CLAS detector
• Measurements of the ${\gamma }_{v}p\to p^{\prime }{\pi }^{+}{\pi }^{-}$ cross section with the CLAS detector for $0.4$ GeV${}^2$ $<Q^2<$ $1.0$ GeV${}^2$ and $1.3$ GeV $<W<$ $1.825$ GeV
• Transition form factors and helicity amplitudes for electroexcitation of negative- and positive parity nucleon resonances in a light-front quark model
• Resonant contributions to inclusive nucleon structure functions from exclusive meson electroproduction data
• Exclusive ${\mathbf{\pi }}^0\mathbf{p}$ electroproduction off protons in the resonance region at photon virtualities 0.4~GeV${}^2$ $\le {\mathbf{Q}}^2\le 1$~GeV${}^2$
• Extracting meson-baryon contributions to the electroexcitation of the $N(1675){\frac{5}{2}}^{-}$ nucleon resonance
• Electroexcitation of the Delta(1232)3/2+ and Delta(1600)3/2+ in a light-front relativistic quark model
• N* Experiments and their Impact on Strong QCD Physics
• Nucleon Resonance Physics
• Low-$Q^2$ empirical parametrizations of the $N^{\ast }$ helicity amplitudes
• Resonant contributions to polarized proton structure functions
• Target and Beam-Target Spin Asymmetries in Exclusive Pion Electroproduction for $Q^2>1$ GeV${}^2$. I. $ep\to e{\pi }^{+}n$
• Spectrum and Structure of Excited Baryons with CLAS
• Target and Beam-Target Spin Asymmetries in Exclusive ${\pi }^{+}$ and ${\pi }^{-}$ Electroproduction with 1.6 to 5.7 GeV Electrons
• Evaluation of the inclusive electron scattering observables in the resonance region from the experimental data
• Charged current (anti)neutrino induced eta production off the nucleon
• Modern Dynamical Coupled-Channels Calculations for Extracting and Understanding the Nucleon Spectrum
• Quark model calculations of transition form factors at high photon virtualities
• Polarized proton structure in the resonance region
• A Relativistic Model for the Electromagnetic Structure of Baryons from the 3rd Resonance Region