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, Letnik:
959, Številka:
C
Journal Article
Recenzirano
Odprti dostop
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.
Abstract
Fifty thousand hybrid circuits of five different types will be manufactured for the Phase-2 Upgrade of the CMS Outer Tracker. These circuits must undergo a strict quality control process, ...composed of functional testing and visual inspection, before they can be assembled into modules. The hybrids will be functionally tested first at the manufacturing site. Afterwards, they will be visually inspected and functionally tested again at CERN or at collaborating institutes. Results from these processes will be stored in the CMS production database. This paper presents the software tools developed to carry out these tasks.
The CLAS12 Central Neutron Detector Chatagnon, P.; Bettane, J.; Hoballah, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
959, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The Central Neutron Detector is a scintillator barrel that was designed to detect 0.2-1 GeV neutrons at lab polar angles from 40∘ to 120∘ in the CLAS12 spectrometer in Hall B at Jefferson Laboratory. ...The design is based on three radial layers of paddles read out at the upstream end of the barrel by photomultipliers tubes. Neighboring paddles in each layer are coupled together at the downstream end of the barrel by “U-turn” light guides. The components of this detector are presented and the performance of the detector with the first beam data taken by CLAS12 is reported.
The strong nuclear interaction is probed at short-distance and high-momenta using new measurements of the $^{12}$C$(e,e'p)$ and $^{12}$C$(e,e'pn)$ reactions, at high-$Q^2$ and $x_B>1$. The data span ...a missing-momentum range of 300-850 MeV/c and is predominantly sensitive to the dominant proton-neutron short-range correlated (SRC) pairs and complements previous $^{12}$C$(e,e'pp)$ measurements. The data are well reproduced by theoretical calculations using the Generalized Contact Formalism with both chiral and phenomenological nucleon-nucleon ($NN$) interaction models. This agreement, observed here for the first time, suggests that the measured high missing-momentum protons up to $850$ MeV/c belonged to SRC pairs. The measured $^{12}$C$(e,e'pn)$ / $^{12}$C$(e,e'p)$ ratio is consistent with a decrease in the fraction of proton-neutron SRC pairs with increasing missing-momentum. This confirms the transition from an isospin-dependent tensor $NN$ interaction at $\sim 400$ MeV/c to an isospin-independent scalar interaction at high-momentum around $\sim 800$ MeV/c.
The CLAS12 software framework and event reconstruction Ziegler, V.; Baltzell, N.A.; Bossù, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
959, Številka:
C
Journal Article
Recenzirano
Odprti dostop
We describe offline event reconstruction for the CEBAF Large Acceptance Spectrometer at 12 GeV (CLAS12), including an overview of the offline reconstruction framework and software tools, a ...description of the algorithms developed for the individual detector subsystems, and the overall approach for charged and neutral particle identification. We also present the scheme for data processing and the code management procedures.
Background: Energetic quarks in nuclear DIS propagate through the nuclear medium. Processes that are believed to occur inside nuclei include quark energy loss through medium-stimulated gluon ...bremsstrahlung and intra-nuclear interactions of forming hadrons. More data are required to gain a more complete understanding of these effects. Purpose: To test the theoretical models of parton transport and hadron formation, we compared their predictions for the nuclear and kinematic dependence of pion production in nuclei. Methods: We have measured charged-pion production in semi-inclusive DIS off D, C, Fe, and Pb using the CLAS detector and the CEBAF 5.014 GeV electron beam. We report results on the nuclear-to-deuterium multiplicity ratio for $\pi^{+}$ and $\pi^{-}$ as a function of energy transfer, four-momentum transfer, and pion energy fraction or transverse momentum - the first three-dimensional study of its kind. Results: The $\pi^{+}$ multiplicity ratio is found to depend strongly on the pion fractional energy $z$, and reaches minimum values of $0.67\pm0.03$, $0.43\pm0.02$, and $0.27\pm0.01$ for the C, Fe, and Pb targets, respectively. The $z$ dependences of the multiplicity ratios for $\pi^{+}$ and $\pi^{-}$ are equal within uncertainties for C and Fe targets but show differences at the level of 10$\%$ for the Pb-target data. The results are qualitatively described by the GiBUU transport model, as well as with a model based on hadron absorption, but are in tension with calculations based on nuclear fragmentation functions. Conclusions: These precise results will strongly constrain the kinematic and flavor dependence of nuclear effects in hadron production, probing an unexplored kinematic region. They will help to reveal how the nucleus reacts to a fast quark, thereby shedding light on its color structure, transport properties, and on the mechanisms of the hadronization process.
High precision measurements of the polarized electron beam-spin asymmetry in semi-inclusive deep inelastic scattering (SIDIS) from the proton have been performed using a 10.6 GeV incident electron ...beam and the CLAS12 spectrometer at Jefferson Lab. We report here a high precision multidimensional study of single π^{+} SIDIS data over a large kinematic range in Bjorken x, fractional energy, and transverse momentum of the hadron as well as photon virtualities Q^{2} ranging from 1-7 GeV^{2}. In particular, the structure function ratio F_{LU}^{sinϕ}/F_{UU} has been determined, where F_{LU}^{sinϕ} is a twist-3 quantity that can reveal novel aspects of emergent hadron mass and quark-gluon correlations within the nucleon. The data's impact on the evolving understanding of the underlying reaction mechanisms and their kinematic variation is explored using theoretical models for the different contributing transverse momentum dependent parton distribution functions.
Deeply virtual Compton scattering (DVCS) allows one to probe generalized parton distributions describing the 3D structure of the nucleon. We report the first measurement of the DVCS beam-spin ...asymmetry using the CLAS12 spectrometer with a 10.2 and 10.6 GeV electron beam scattering from unpolarized protons. The results greatly extend the Q^{2} and Bjorken-x phase space beyond the existing data in the valence region and provide 1600 new data points measured with unprecedented statistical uncertainty, setting new, tight constraints for future phenomenological studies.
Here, the single-differential and fully integrated cross sections for quasi-free $π^+π^-$ electroproduction off protons bound in deuterium have been extracted for the first time. The experimental ...data were collected at Jefferson Laboratory with the CLAS detector. The measurements were performed in the kinematic region of the invariant mass W from 1.3 GeV to 1.825 GeV and photon virtuality Q2 from 0.4 GeV2 to 1.0 GeV2. Sufficient experimental statistics allow for narrow binning in all kinematic variables, while maintaining a small statistical uncertainty. The extracted cross sections were compared with the corresponding cross sections off free protons, which allowed us to obtain an estimate of the contribution from events in which interactions between the final-state hadrons and the spectator neutron took place.
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