16 research outputs found
Transition nucleon resonance electrocouplings from CLAS data on electroproduction off protons
Electrocouplings of excited proton states with masses less than 1.8 GeV were
determined for the first time from the CLAS data on
electroproduction at photon virtualities 1.5 GeV.
Electrocouplings were obtained from a combined fit of all available observables
within the framework of a phenomenological reaction model.Comment: 4 pages, 3 figures, 1 table, CLAS Collaboratio
Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS
Studies of the nucleon resonance electroexcitation amplitudes in a wide range
of photon virtualities offer unique information on many facets of strong QCD
behind the generation of all prominent excited nucleon states. Advances in the
evaluation of resonance electroexcitation amplitudes from the data measured
with the CLAS detector and the future extension of these studies with the
CLAS12 detector at Jefferson Lab are presented. For the first time, analyses of
, , , and electroproduction off proton
channels have provided electroexcitation amplitudes of most resonances in the
mass range up to 1.8 GeV and at photon virtualities ~GeV.Studies
of the resonance electroexcitation amplitudes revealed the structure as a
complex interplay between the inner core of three dressed quarks and the
external meson-baryon cloud. The successful description of the
and electrocouplings achieved within the
Dyson-Schwinger Equation approach under a traceable connection to the QCD
Lagrangian and supported by the novel light front quark model demonstrated the
relevance of dressed quarks with dynamically generated masses as an active
structural component in baryons. Future experiments with the CLAS12 detector
will offer insight into the structure of all prominent resonances at the
highest photon virtualities, ~GeV, ever achieved in exclusive
reactions, thus addressing the most challenging problems of the Standard Model
on the nature of hadron mass, quark-gluon confinement, and the emergence of
nucleon resonance structures from QCD. A search for new states of hadronic
matter, the so-called hybrid-baryons with glue as a structural component, will
complete the long term efforts on the resonance spectrum exploration.Comment: 16 pages, 5 figure
Two Pion Photo- and Electroproduction with CLAS
Exclusive photo- and electroproduction data from CLAS have
considerably extended the information on the spectrum and structure of nucleon
resonances. The data from the and channels have provided
results on the electrocouplings of most resonances in the mass region up to 1.8
GeV and at photon virtualities up to 5.0 GeV. The recent CLAS data on
photoproduction have improved knowledge on the photocouplings of
nucleon resonances in the mass range of 1.6 GeV 2.0 GeV and
on their decays to the and final hadron states. For the
first time, the electrocouplings of the and
excited states have become available from data at 2.0 GeV
5.0 GeV. Analyses of the combined photo- and
electroproduction data have revealed evidence for the candidate-state
. The new results on the nucleon resonance spectrum,
electroexcitation amplitudes from analysis of the CLAS photo- and
electroproduction data, and their impact on the exploration of strong QCD are
presented
Towards a combined analysis of inclusive/exclusive electroproduction
In view of the major advances achieved by the CLAS experiments in studying
the N* electroexcitation amplitudes, as well as further extension of these
studies in the experiments with CLAS12, we present an approach for the
evaluation of the resonant contributions to inclusive electron scattering off
protons. For the first time, the resonant contributions are determined from the
experimental results on N* electrocouplings available from the data analyses of
exclusive meson electroproduction off protons. This is a useful benchmark for
future endeavours on understanding the transition region between low and
high-energy regions, strongly related to tests on quark-hadron duality.Comment: NSTAR2019 conference proceeding
Studying the Pc(4450) resonance in J/psi photoproduction off protons
The LHCb has reported the observation of a resonancelike structure, the
Pc(4450), in the J/psi p invariant masses. In our work, we discuss the
feasibility of detecting this structure in J/psi photoproduction, e.g. in the
measurements that have been approved for the experiments in Hall A/C and in
Hall B with CLAS12 at JLab. Also the GlueX Collaboration has already reported
preliminary results. We take into account the experimental resolution effects,
and perform a global fit to world J/psi photoproduction data in order to study
the possibility of observing the Pc(4450) signal in future JLab data. We
present a first estimate of the upper limit for the branching ratio of the
Pc(4450) into the J/psi p channel, and we study the angular distributions of
the differential cross sections. This will shed light on the nature and
couplings of the Pc(4450) structure in the future photoproduction experiments.Comment: NSTAR 2017 conference proceeding
Double Polarization Observables in Pentaquark Photoproduction
We investigate the properties of the hidden charm pentaquark-like resonances
first observed by LHCb in 2015, by measuring the polarization transfer KLL
between the incident photon and the outgoing proton in the exclusive
photoproduction of J/psi near threshold. We present a first estimate of the
sensitivity of this observable to the pentaquark photocouplings and hadronic
branching ratios, and extend our predictions to the case of initial state
helicity correlation ALL, using a polarized target. These results serve as a
benchmark for the SBS experiment at Jefferson Lab, which proposes to measure
for the first time the helicity correlations ALL and KLL in J/psi exclusive
photoproduction, in order to determine the pentaquark photocouplings and
branching ratios.Comment: 9 pages, 7 figures, 2 tables, Version published in PR
Two Pion Photo- and Electroproduction with CLAS
Exclusive π+π-p photo- and electroproduction data from CLAS have considerably extended the information on the spectrum and structure of nucleon resonances. The data from the π+π-p and Nπ channels have provided results on the electrocouplings of most resonances in the mass region up to 1.8 GeV and at photon virtualities up to 5.0 GeV2. The recent CLAS data on π+π-p photoproduction have improved knowledge on the photocouplings of nucleon resonances in the mass range of 1.6 GeV < MN* < 2.0 GeV and on their decays to the πΔ and ρp final hadron states. Analyses of the combined π+π-p photo- and electroproduction data have revealed evidence for the candidate-state N’(1720)3/2+. The new results on the nucleon resonance spectrum, electroexcitation amplitudes from analysis of the CLAS π+π-p photo- and electroproduction data, and their impact on the exploration of strong QCD are presented
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Nucleon Resonance Electrocouplings from the CLAS Data on Exclusive Meson Electroproduction off Protons
{gamma}{sub v}NN* transition helicity amplitudes (electrocouplings) of several prominent excited proton states are determined for the first time in independent analyses of {pi}{sup +}n, {pi}{sup 0}p, and {pi}{sup +}{pi}{sup -}p electroproduction off protons. Consistent results on resonance electrocouplings obtained from major meson electroproduction channels offer an evidence for reliable extraction of these fundamental quantities. Analysis of {pi}{sup +}{pi}{sup -}p electroproduction has extended considerably information on electrocouplings of high lying N* states, which decay preferentially to the N{pi}{pi} final states