J. A. Fleming

University of Edinburgh

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N. Zachariou

University of York

A. D’Angelo

University of Rome Tor Vergata

M. Battaglieri

Istituto Nazionale di Fisica Nucleare

D. P. Watts

University of York

R. A. Schumacher

Carnegie Mellon University

D. G. Ireland

University of Glasgow

P. L. Cole

Thomas Jefferson National Accelerator Facility

W. J. Briscoe

George Washington University

A. Celentano

Istituto Nazionale di Fisica Nucleare, Sezione di Genova

E. Voutier

Institut National de Physique Nucléaire et de Physique des Particules

Cooperative Institutions

Thomas Jefferson National Accelerator Facility

260

Campbell Collaboration

162

Argonne National Laboratory

140

University of York

126

Istituto Nazionale di Fisica Nucleare, Sezione di Genova

Old Dominion University

Institut de Physique

University of America

Catholic University of America

George Washington University

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Beam-target helicity asymmetry E in K0Λ and K0Σ0

Physical review. C (2018)

Dao H. Ho R. A. Schumacher A. D’Angelo A. Deur J. A. Fleming

We report the first measurements of the E beam-target helicity asymmetry for the →γ→n→K0Λ and K0Σ0 channels in the energy range 1.70≤W≤2.34 GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees is used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin I=0 and I=1 photocoupling transition amplitudes in pseudoscalar meson photoproduction.2 MoreReceived 16 May 2018DOI:https://doi.org/10.1103/PhysRevC.98.045205©2018 American Physical SocietyPhysics Subject Headings (PhySH)PolarizationPropertiesParticle propertiesPolarizationPropertiesAtomic PropertiesPolarizationResearch AreasPhotonuclear reactionsPhysical SystemsHyperonsKaonsStrange quarkPropertiesPolarizationTechniquesMachine learningOptical, coupled-channel & distorted wave modelsNuclear PhysicsParticles & Fields

Helicity

10.1103/physrevc.98.045205

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Citations (9)

Cross Sections for the Exclusive Photon Electroproduction on the Proton and Generalized Parton Distributions

Physical Review Letters (2015)

H. S. Jo F. X. Girod H. Avakian V. D. Burkert M. Garçon

Unpolarized and beam-polarized fourfold cross sections (d^{4}σ/dQ^{2}dx_{B}dtdϕ) for the ep→e^{'}p^{'}γ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 (Q^{2},x_{B},t) bins over the widest phase space ever explored in the valence-quark region. Several models of generalized parton distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD H, expected to be the dominant contributor to these observables. Through a leading-twist extraction of Compton form factors, these results support the model predictions of a larger nucleon size at lower quark-momentum fraction x_{B}.

10.1103/physrevlett.115.212003

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Citations (92)

The Beam-Target Helicity Asymmetry for $\vec{\gamma} \vec{n} \rightarrow \pi^- p$ in the {\bf{$N^*$} Resonance Region

arXiv (Cornell University) (2017)

D. Ho P. Peng C.D. Bass P. Collins A. D’Angelo

We report the first beam-target double-polarization asymmetries in the $\gamma + n(p) \rightarrow \pi^- + p(p)$ reaction spanning the nucleon resonance region from invariant mass $W$= $1500$ to $2300$ MeV. Circularly polarized photons and longitudinally polarized deuterons in $H\!D$ have been used with the CLAS detector at Jefferson Lab. The exclusive final state has been extracted using three very different analyses that show excellent agreement, and these have been used to deduce the {\it{E}} polarization observable for an effective neutron target. These results have been incorporated into new partial wave analyses, and have led to significant revisions for several $\gamma nN^*$ resonance photo-couplings.

Helicity

Invariant mass

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First Exclusive Measurement of Deeply Virtual Compton Scattering off He4 : Toward the 3D Tomography of Nuclei

Physical Review Letters (2017)

M. Hattawy N. A. Baltzell R. Dupré K. Hafidi S. Stepanyan

We report on the first measurement of the beam-spin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment uses the 6 GeV electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator at Jefferson Lab incident on a pressurized ^{4}He gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron is detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber is used to detect the recoiling ^{4}He nuclei. We measure beam-spin asymmetries larger than those observed on the free proton in the same kinematic domain. From these, we are able to extract, in a model-independent way, the real and imaginary parts of the only ^{4}He Compton form factor, H_{A}. This first measurement of coherent deeply virtual Compton scattering on the ^{4}He nucleus, with a fully exclusive final state via nuclear recoil tagging, leads the way toward 3D imaging of the partonic structure of nuclei.

Recoil

10.1103/physrevlett.119.202004

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Citations (37)

Precision measurements ofg1of the proton and of the deuteron with 6 GeV electrons

Physical Review C (2014)

Y. Prok P. Bosted N. D. Kvaltine K. P. Adhikari D. Adikaram

The inclusive polarized structure functions of the proton and deuteron, g1p and g1d, were measured with high statistical precision using polarized 6 GeV electrons incident on a polarized ammonia target in Hall B at Jefferson Laboratory. Electrons scattered at lab angles between 18 and 45 degrees were detected using the CEBAF Large Acceptance Spectrometer (CLAS). For the usual DIS kinematics, Q^2>1 GeV^2 and the final-state invariant mass W>2 GeV, the ratio of polarized to unpolarized structure functions g1/F1 is found to be nearly independent of Q^2 at fixed x. Significant resonant structure is apparent at values of W up to 2.3 GeV. In the framework of perturbative QCD, the high-W results can be used to better constrain the polarization of quarks and gluons in the nucleon, as well as high-twist contributions.

10.1103/physrevc.90.025212

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Citations (46)

Measurement of the differential and total cross sections of the γd→K0Λ(p) reaction within the resonance region

Physical review. C (2017)

N. Compton C. Taylor K. Hicks P. L. Cole N. Zachariou

We report the first measurement of differential and total cross sections for the $\ensuremath{\gamma}d\ensuremath{\rightarrow}{K}^{0}\mathrm{\ensuremath{\Lambda}}(p)$ reaction, using data from the CLAS detector at the Thomas Jefferson National Accelerator Facility. Data collected during two separate experimental runs were studied with photon-energy coverage 0.8--3.6 GeV and 0.5-- 2.6 GeV, respectively. The two measurements are consistent giving confidence in the method and determination of systematic uncertainties. The cross sections are compared with predictions from the KAON-MAID theoretical model (without kaon exchange), which deviate from the data at higher $W$ and at forward kaon angles. These data, along with previously published cross sections for ${K}^{+}\mathrm{\ensuremath{\Lambda}}$ photoproduction, provide essential constraints on the nucleon resonance spectrum. A first partial wave analysis was performed that describes the data without the introduction of new resonances.

10.1103/physrevc.96.065201

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Citations (28)

Erratum: Simultaneous trapping of two different atomic species in a vapor-cell magneto-optical trap

Physical Review A (1996)

M. S. Santos P. Nussenzveig Luís Gustavo Marcassa Kristian Helmerson J. A. Fleming

Magneto-optical trap

Trap (plumbing)

10.1103/physreva.54.1739

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Citations (2)

Measurement of theΣπphotoproduction line shapes near theΛ(1405)

Physical Review C (2013)

K. Moriya R. A. Schumacher K. P. Adhikari D. Adikaram M. Aghasyan

The reaction gamma + p -> K+ + Sigma + pi was used to determine the invariant mass distributions or "line shapes" of the Sigma+ pi-, Sigma- pi+ and Sigma0 pi0 final states, from threshold at 1328 MeV/c^2 through the mass range of the Lambda(1405) and the Lambda(1520). The measurements were made with the CLAS system at Jefferson Lab using tagged real photons, for center-of-mass energies 1.95 < W < 2.85 GeV. The three mass distributions differ strongly in the vicinity of the I=0 \Lambda(1405), indicating the presence of substantial I=1 strength in the reaction. Background contributions to the data from the Sigma0(1385) and from K^* Sigma production were studied and shown to have negligible influence. To separate the isospin amplitudes, Breit-Wigner model fits were made that included channel-coupling distortions due to the NKbar threshold. A best fit to all the data was obtained after including a phenomenological I=1, J^P = 1/2^- amplitude with a centroid at 1394\pm20 MeV/c^2 and a second I=1 amplitude at 1413\pm10 MeV/c^2. The centroid of the I=0 Lambda(1405) strength was found at the Sigma pi threshold, with the observed shape determined largely by channel-coupling, leading to an apparent overall peak near 1405 MeV/c^2.

Sigma

10.1103/physrevc.87.035206

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Citations (130)

Beam asymmetryΣforπ+andπ0photoproduction on the proton for photon energies from 1.102 to 1.862 GeV

Physical Review C (2013)

M. Dugger B. G. Ritchie P. Collins E. Pasyuk W. J. Briscoe

Beam asymmetries for the reactions gamma p -> p pi0 and gamma p -> n pi+ have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged, linearly polarized photon beam with energies from 1.102 to 1.862 GeV. A Fourier moment technique for extracting beam asymmetries from experimental data is described. The results reported here possess greater precision and finer energy resolution than previous measurements. Our data for both pion reactions appear to favor the SAID and Bonn-Gatchina scattering analyses over the older Mainz MAID predictions. After incorporating the present set of beam asymmetries into the world database, exploratory fits made with the SAID analysis indicate that the largest changes from previous fits are for properties of the Delta(1700) 3/2- and Delta(1905) 5/2+ states.

10.1103/physrevc.88.065203

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Citations (43)

Beam–target helicity asymmetry E in K+Σ− photoproduction on the neutron

Physics Letters B (2020)

N. Zachariou D. P. Watts J. A. Fleming A. Sarantsev V. A. Nikonov

We report a measurement of a beam–target double-polarisation observable (E) for the γ→n→(p)→K+Σ−(p) reaction. The data were obtained impinging the circularly-polarised energy-tagged photon beam of Hall B at Jefferson Lab on a longitudinally-polarised frozen-spin hydrogen deuteride (HD) nuclear target. The E observable for an effective neutron target was determined for centre-of-mass energies 1.70≤W≤2.30 GeV, with reaction products detected over a wide angular acceptance by the CLAS spectrometer. These new double-polarisation data give unique constraints on the strange decays of excited neutron states. Inclusion of the new data within the Bonn-Gatchina theoretical model results in significant changes for the extracted photocouplings of a number of established nucleon resonances. Possible improvements in the PWA description of the experimental data with additional "missing" resonance states, including the N(2120)3/2− resonance, are also quantified.

Helicity

10.1016/j.physletb.2020.135662

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Citations (8)