166 research outputs found
Separated structure functions for the exclusive electroproduction of K+Λ and K+Σ0 final states
We report measurements of the exclusive electroproduction of K+Λ and K+Σ0 final states from a proton target using the Continuous Electron Beam Accelerator Facility (CEBAF) large-acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions σT,σL,σTT, and σLT were extracted from the Φ- and ε-dependent differential cross sections taken with electron beam energies of 2.567, 4.056, and 4.247 GeV. This analysis represents the first σL/σT separation with the CLAS detector, and the first measurement of the kaon electroproduction structure functions away from parallel kinematics. The data span a broad range of momentum transfers from 0.
Gerasimov-Drell-Hearn Sum Rule and the Discrepancy between the New CLAS and SAPHIR Data
Contribution of the K^+\Lambda channel to the Gerasimov-Drell-Hearn (GDH) sum
rule has been calculated by using the models that fit the recent SAPHIR or CLAS
differential cross section data. It is shown that the two data sets yield quite
different contributions. Contribution of this channel to the forward spin
polarizability of the proton has been also calculated. It is also shown that
the inclusion of the recent CLAS C_x and C_z data in the fitting data base does
not significantly change the result of the present calculation. Results of the
fit, however, reveal the role of the S_{11}(1650), P_{11}(1710), P_{13}(1720),
and P_{13}(1900) resonances for the description of the C_x and C_z data. A
brief discussion on the importance of these resonances is given. Measurements
of the polarized total cross section \sigma_{TT'} by the CLAS, LEPS, and MAMI
collaborations are expected to verify this finding.Comment: 15 pages, 8 figure
Electroproduction of kaons from the proton in a Regge-plus-resonance approach
We present a Regge-plus-resonance (RPR) description of the p(e,e'K^+)Y
processes (Y=\Lambda,\Sigma^0) in the resonance region. The background
contributions to the RPR amplitude are constrained by the high-energy p(\gamma,
K^+)Y data. As a result, the number of free model parameters in the resonance
region is considerably reduced compared to typical effective-Lagrangian
approaches. We compare a selection of RPR model variants, originally
constructed to describe photoproduction, with the world electroproduction
database. The electromagnetic form factors of the intermediate N^*s and
$\Delta^*s are computed in the Bonn constituent-quark model. With this input,
we find a reasonable description of the p(e,e'K^+)Y data without adding or
readjusting any parameters. It is demonstrated that the electroproduction
response functions are extremely useful for fine-tuning both the background and
resonant contributions to the reaction dynamics.Comment: 14 pages, 7 figures; added discussion on double counting in the RPR
model; accepted for publication in Phys. Lett.
Machine Learning-Based Event Generator for Electron-Proton Scattering
We present a new machine learning-based Monte Carlo event generator using generative adversarial networks (GANs) that can be trained with calibrated detector simulations to construct a vertex-level event generator free of theoretical assumptions about femtometer scale physics. Our framework includes a GAN-based detector folding as a fast-surrogate model that mimics detector simulators. The framework is tested and validated on simulated inclusive deep-inelastic scattering data along with existing parametrizations for detector simulation, with uncertainty quantification based on a statistical bootstrapping technique. Our results provide for the first time a realistic proof of concept to mitigate theory bias in inferring vertex-level event distributions needed to reconstruct physical observables
AI-based Monte Carlo event generator for electron-proton scattering
We present a new strategy using artificial intelligence (AI) to build the
first AI-based Monte Carlo event generator (MCEG) capable of faithfully
generating final state particle phase space in lepton-hadron scattering. We
show a blueprint for integrating machine learning strategies with calibrated
detector simulations to build a vertex-level, AI-based MCEG, free of
theoretical assumptions about femtometer scale physics. As the first steps
towards this goal, we present a case study for inclusive electron-proton
scattering using synthetic data from the PYTHIA MCEG for testing and validation
purposes. Our quantitative results validate our proof of concept and
demonstrate the predictive power of the trained models. The work suggests new
venues for data preservation to enable future QCD studies of hadrons structure,
and the developed technology can boost the science output of physics programs
at facilities such as Jefferson Lab and the future Electron-Ion Collider.Comment: 4 pages, 4 figures. arXiv admin note: text overlap with
arXiv:2001.1110
Probing the nucleon structure with CLAS
An overview of recent results with CLAS is presented with emphasis on nucleon
resonance studies, nucleon spin structure, and generalized parton
distributions.Comment: Plenary talk presented at NSTAR 2007, Bonn, German
Exclusive electroproduction of K+ Lambda and K+ Sigma^0 final states at Q^2 = 0.030-0.055 (GeV/c)^2
Cross section measurements of the exclusive p(e,e'K+)Lambda,Sigma^0
electroproduction reactions have been performed at the Mainz Microtron MAMI in
the A1 spectrometer facility using for the first time the Kaos spectrometer for
kaon detection. These processes were studied in a kinematical region not
covered by any previous experiment. The nucleon was probed in its third
resonance region with virtual photons of low four-momenta, Q^2= 0.030-0.055
(GeV/c)^2. The MAMI data indicate a smooth transition in Q^2 from
photoproduction to electroproduction cross sections. Comparison with
predictions of effective Lagrangian models based on the isobar approach reveal
that strong longitudinal couplings of the virtual photon to the N* resonances
can be excluded from these models.Comment: 16 pages, 7 figure
Probing the high momentum component of the deuteron at high Q^2
The d(e,e'p) cross section at a momentum transfer of 3.5 (GeV/c)^2 was
measured over a kinematical range that made it possible to study this reaction
for a set of fixed missing momenta as a function of the neutron recoil angle
theta_nq and to extract missing momentum distributions for fixed values of
theta_nq up to 0.55 GeV/c. In the region of 35 (deg) <= theta_nq <= 45 (deg)
recent calculations, which predict that final state interactions are small,
agree reasonably well with the experimental data. Therefore these experimental
reduced cross sections provide direct access to the high momentum component of
the deuteron momentum distribution in exclusive deuteron
electro-disintegration.Comment: 5 pages, 2 figure
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