.
The CLAS and Hall A Collaborations at Jefferson Laboratory have recently released new results for the
e
p
→
e
p
γ
reaction. We analyze these new data within the Generalized Parton Distribution ...formalism. Employing a fitter algorithm introduced and used in earlier works, we are able to extract from these data new constraints on the kinematical dependence of three Compton Form Factors. Based on experimental data, we subsequently extract the dependence of the proton charge radius on the quarks’ longitudinal momentum fraction.
Recent promising results obtained with the Jefferson Lab CLAS detector on deeply virtual exclusive processes and their link to the generalized parton distributions, along with the experimental ...program for studying GPDs at the 12 GeV upgraded JLab using the CLAS12 detector, are discussed here. With its wide acceptance, high luminosity, good resolution and particle identification capabilities, as well as large Q2 and xB coverage (1GeV<Q2<10GeV2, 0.1<xB<0.8), CLAS12 will be the ideal facility to pursue the research on the three-dimensional structure of the nucleon in the valence region.
Measuring DVCS on a neutron target is a necessary step to deepen our understanding of the structure of the nucleon in terms of Generalized Parton Distributions (GPDs). The combination of DVCS ...observables on neutron and proton targets allows to perform a flavor decomposition of the Compton Form Factors (CFFs), which are related to integrals of GPDs. Moreover, neutron-DVCS plays a complementary role to DVCS on a transversely polarized proton target in the determination of the CFF of the GPD
E
, the least known and constrained GPD that enters Ji’s angular momentum sum rule. A measurement of the beam-charge asymmetry (BCA) in the
e
±
d
→
e
±
n
γ
(
p
)
reaction can significantly impact the experimental determination of the real CFFs of the
E
and, to a lesser extent,
H
~
CFFs.
The CLAS12 Geant4 simulation Ungaro, M.; Angelini, G.; Battaglieri, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Volume:
959, Issue:
C
Journal Article
Peer reviewed
Open access
The Geant4 Monte-Carlo (GEMC) package is used to simulate the passage of particles through the various CLAS12 detectors. The geometry is implemented through a database of Geant4 volumes created ...either through the GEMC native API, by the CLAS12 geometry service, or imported from the CAD engineering model. The truth information is digitized with a plugin mechanism by routines specific to each detector and includes the use of the CLAS12 calibration database constants to produce both ADC and TDC response functions. Theoretical models that produce the generated events interface with GEMC through the LUND data format. The merging of simulated data with real random trigger data provides a mechanism to include both beam and electronic background into the simulation of generated events to accurately model beam data from the CLAS12 detector. The performance of simulation is demonstrated by comparison with the experimental data.
The unpolarized and polarized Beam Charge Asymmetries (BCAs) of the
e
→
±
p
→
e
±
p
γ
process off unpolarized hydrogen are discussed. The measurement of BCAs with the CLAS12 spectrometer at the ...Thomas Jefferson National Accelerator Facility, using polarized positron and electron beams at 10.6 GeV is investigated. This experimental configuration allows to measure azimuthal and
t
-dependences of the unpolarized and polarized BCAs over a large
(
x
B
,
Q
2
)
phase space, providing a direct access to the real part of the Compton Form Factor (CFF)
H
. Additionally, these measurements confront the Bethe-Heitler dominance hypothesis and eventual effects beyond leading twist. The impact of potential positron beam data on the determination of CFFs is also investigated within a local fitting approach of experimental observables. Positron data are shown to strongly reduce correlations between CFFs and consequently improve significantly the determination of
R
e
H
.
We report on the first measurement of cross sections for exclusive deeply virtual pion electroproduction off the proton, ep→e′nπ+, above the resonance region at backward pion center-of-mass angles. ...The φπ⁎-dependent cross sections were measured, from which we extracted three combinations of structure functions of the proton. Our results are compatible with calculations based on nucleon-to-pion transition distribution amplitudes (TDAs). These non-perturbative objects are defined as matrix elements of three-quark-light-cone-operators and characterize partonic correlations with a particular emphasis on baryon charge distribution inside a nucleon.
We report the first experimental measurements of the nine 1-fold differential cross sections for the γp→π+π−p reaction, obtained with the CLAS detector at Jefferson Laboratory. The measurements cover ...the invariant mass range of the final state hadrons from 1.6 GeV <W< 2.0 GeV. For the first time the photocouplings of all prominent nucleon resonances in this mass range have been extracted from this exclusive channel. Photoproduction of two charged pions is of particular importance for the evaluation of the photocouplings for the Δ(1620)1/2−, Δ(1700)3/2−, N(1720)3/2+, and Δ(1905)5/2+ resonances, which have dominant decays into the ππN final states rather than the more extensively studied single meson decay channels.
The implementation of a smart-pump continuous quality-improvement (CQI) program across a large health system is described, with an emphasis on key metrics for outcomes analyses and program ...refinement.
Three years ago, the University of Pittsburgh Medical Center health system launched a CQI initiative to help ensure the safe use of 6000 smart pumps in its 14 inpatient facilities. A centralized team led by pharmacists is responsible for the retrieval and interpretation of smart-pump data, which is continuously transmitted to a main server. CQI findings are regularly posted on the health system's interdisciplinary intranet. Monitored metrics include rates of compliance with preprogrammed infusion limits, the top 20 drugs involved in alerts, drugs associated with alert-override rates of ≥90%, numbers of alerts by infusion type, nurse responses to alerts, and alert rate per drug library update. Based on the collected CQI data and site-specific requests, four systemwide updates of the smart-pump drug library were performed during the first 18 months of the program, reducing "nuisance alerts" by about 10% per update cycle and enabling targeted interventions to reduce rapid-infusion errors, other adverse drug events (ADEs), and pump-programming workarounds. Over one 12-month period, bedside alerts prompted nurses to reprogram or cancel continuous infusions an average of 400 times per month, potentially averting i.v. medication ADEs.
A smart-pump CQI program is an effective tool for enhancing the safety of i.v. medication administration. The ongoing refinement of the drug library through the development and implementation of key interventions promotes the growth and sustainability of the smart-pump initiative systemwide.
The cross section for coherent ω-meson photoproduction off the deuteron has been measured for the first time as a function of the momentum transfer t=(Pγ−Pω)2 and photon energy Eγ using the CLAS ...detector at the Thomas Jefferson National Accelerator Facility. The cross sections are measured in the energy range 1.4<Eγ<3.4 GeV. A model based on ω−N rescattering is consistent with the data at low and intermediate momentum transfer, |t|. For 2.8<Eγ<3.4 GeV, the total cross-section of ω−N scattering, based on fits within the framework of the Vector Meson Dominance model, is in the range of 30–40 mb.
The beam spin asymmetry of the exclusive pseudoscalar channel e→p→e′p′η was measured for the first time in the deep-inelastic regime (W>2 GeV/c2 and Q2>1 GeV2/c2) using a longitudinally polarized ...5.78 GeV electron beam at Jefferson Lab with the CEBAF Large Acceptance Spectrometer. The data were accumulated in 144 four-dimensional bins of Q2, xB, −t and ϕ over a wide kinematic range, where ϕ is the azimuthal angle between the lepton and hadron scattering planes, The measured azimuthal dependence with large amplitudes of the sinϕ moments is a clear indication of a substantial contribution to the polarized cross-section from transversely polarized virtual photons. In the framework of generalized parton distributions (GPDs) this contribution is expressed via longitudinal-transverse interference between chiral-even and chiral-odd GPDs. The experimental results are compared to the existing theoretical models demonstrating the sensitivity to the product of chiral-odd and chiral-even GPDs and provide new constraints to the existing GPD parameterizations.
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