We measure the spin-density matrix elements (SDMEs) of the Delta(++)(1232) in the photoproduction reaction gamma p -> pi(-) Delta(++)(1232) with the GlueX experiment in Hall D at Jefferson Lab. The measurement uses a linearly-polarized photon beam with energies from 8.2 to 8.8GeV and the statistical precision of the SDMEs exceeds the previous measurement by three orders of magnitude for the momentum transfer squared region below 1.4GeV(2). The data are sensitive to the previously undetermined relative sign between couplings in existing Regge-exchange models. Linear combinations of the extracted SDMEs allow for a decomposition into natural and unnatural-exchange amplitudes. We find that the unnatural exchange plays an important role in the low momentum transfer region.

We report on the first measurement of J/ψ photoproduction from nuclei in the photon energy range of 7 to 10.8 GeV, extending above and below the photoproduction threshold in the free proton of ∼8.2  GeV. The experiment used a tagged photon beam incident on deuterium, helium, and carbon, and the GlueX detector at Jefferson Lab to measure the semi-inclusive A(γ,e^{+}e^{-}p) reaction with a dilepton invariant mass M(e^{+}e^{-})∼m_{J/ψ}=3.1  GeV. The incoherent J/ψ photoproduction cross sections in the measured nuclei are extracted as a function of the incident photon energy, momentum transfer, and proton-reconstructed missing light-cone momentum fraction. Comparisons with theoretical predictions assuming a dipole form factor allow for extracting a gluonic radius for bound protons of sqrt[⟨r^{2}⟩]=0.85±0.14  fm. The data also suggest an excess of the measured cross section for subthreshold production and for interactions with high missing light-cone momentum fraction protons. The measured enhancement can be explained by modified gluon structure for high-virtuality bound protons.

The spin-exotic hybrid meson π_{1}(1600) is predicted to have a large decay rate to the ωππ final state. Using 76.6  pb^{-1} of data collected with the GlueX detector, we measure the cross sections for the reactions γp→ωπ^{+}π^{-}p, γp→ωπ^{0}π^{0}p, and γp→ωπ^{-}π^{0}Δ^{++} in the range E_{γ}=8-10  GeV. Using isospin conservation, we set the first upper limits on the photoproduction cross sections of the π_{1}^{0}(1600) and π_{1}^{-}(1600). We combine these limits with lattice calculations of decay widths and find that photoproduction of η^{'}π is the most sensitive two-body system to search for the π_{1}(1600).

The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized 8.5 GeV photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson rho(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. We confirm a high degree of s-channel helicity conservation at small squared four-momentum transfer t and are able to extract the t dependence of natural and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full t range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced rho(770) differ by two units are negligible for -t < 0.5 GeV2/c(2).

We report the total and differential cross sections for J/& psi; photoproduction with the large acceptance GlueX spectrometer for photon beam energies from the threshold at 8.2 GeV up to 11.44 GeV and over the full kinematic range of momentum transfer squared, t. Such coverage facilitates the extrapolation of the differential cross sections to the forward (t = 0) point beyond the physical region. The forward cross section is used by many theoretical models and plays an important role in understanding J/& psi; photoproduction and its relation to the J/& psi;-proton interaction. These measurements of J/& psi; photoproduction near threshold are also crucial inputs to theoretical models that are used to study important aspects of the gluon structure of the proton, such as the gluon generalized parton distribution of the proton, the mass radius of the proton, and the trace anomaly contribution to the proton mass. We observe possible structures in the total cross section energy dependence and find evidence for contributions beyond gluon exchange in the differential cross section close to threshold, both of which are consistent with contributions from open-charm intermediate states.

S. Adhikari, C. S. Akondi, M. Albrecht, A. Ali, M. Amaryan, A. Asaturyan, A. Austregesilo, Z. Baldwin, F. Barbosa, J. Barlow, E. Barriga, R. Barsotti, T. D. Beattie, V. V. Berdnikov, T. Black, W. Boeglin, W. J. Briscoe, T. Britton, W. K. Brooks, E. Chudakov, S. Cole, P. L. Cole, O. Cortes, V. Crede, M. M. Dalton, T. Daniels, A. Deur, S. Dobbs, A. Dolgolenko, R. Dotel, M. Dugger, R. Dzhygadlo, H. Egiyan, T. Erbora, A. Ernst, P. Eugenio, C. Fanelli, S. Fegan, ∗ J. Fitches, A. M. Foda, S. Furletov, L. Gan, H. Gao, A. Gasparian, C. Gleason, 28 K. Goetzen, V. S. Goryachev, L. Guo, M. Hagen, H. Hakobyan, A. Hamdi, J. Hernandez, N. D. Hoffman, G. Hou, G. M. Huber, A. Hurley, D. G. Ireland, M. M. Ito, I. Jaegle, N. S. Jarvis, R. T. Jones, V. Kakoyan, G. Kalicy, M. Kamel, V. Khachatryan, M. Khatchatryan, C. Kourkoumelis, S. Kuleshov, A. LaDuke, I. Larin, 14 D. Lawrence, D. I. Lersch, H. Li, W. B. Li, B. Liu, K. Livingston, G. J. Lolos, K. Luckas, V. Lyubovitskij, D. Mack, A. Mahmood, H. Marukyan, V. Matveev, M. McCaughan, M. McCracken, 29 C. A. Meyer, R. Miskimen, R. E. Mitchell, K. Mizutani, V. Neelamana, F. Nerling, L. Ng, A. I. Ostrovidov, Z. Papandreou, C. Paudel, P. Pauli, † R. Pedroni, L. Pentchev, K. J. Peters, J. Reinhold, B. G. Ritchie, J. Ritman, 15 G. Rodriguez, D. Romanov, C. Romero, K. Saldana, C. Salgado, S. Schadmand, A. M. Schertz, A. Schick, A. Schmidt, R. A. Schumacher, J. Schwiening, P. Sharp, X. Shen, M. R. Shepherd, A. Smith, E. S. Smith, D. I. Sober, A. Somov, S. Somov, O. Soto, J. R. Stevens, I. I. Strakovsky, B. Sumner, K. Suresh, V. V. Tarasov, S. Taylor, A. Teymurazyan, A. Thiel, G. Vasileiadis, T. Viducic, T. Whitlatch, N. Wickramaarachchi, M. Williams, Y. Yang, J. Zarling, Z. Zhang, Z. Zhao, J. Zhou, X. Zhou, Q. Zhou, and B. Zihlmann

We report on the measurement of spin density matrix elements of the (cid:2) (1520) in the photoproduction reaction γ p → (cid:2) (1520) K + , via its subsequent decay to K − p . The measurement was performed as part of the GlueX experimental program in Hall D at Jefferson Laboratory using a linearly polarized photon beam with E γ = 8 . 2 GeV–8 . 8 GeV. These are the first such measurements in this photon energy range. Results are presented in bins of momentum transfer squared, − ( t − t 0 ). We compare the results with a Reggeon exchange model and determine that natural exchange amplitudes are dominant in (cid:2) (1520) photoproduction.

We present a search for axion-like particles, a , produced in photon-proton collisions at a center-of-mass energy of approximately 4 GeV, focusing on the scenario where the a -gluon coupling is dominant. The search uses a → γγ and a → π + π − π 0 decays, and a data sample corresponding to an integrated luminosity of 168 pb − 1 collected with the GlueX detector. The search for a → γγ decays is performed in the mass range of 180 < m a < 480 MeV, while the search for a → π + π − π 0 decays explores the 600 < m a < 720 MeV region. No evidence for a signal is found, and 90% confidence-level exclusion limits are placed on the a -gluon coupling strength. These constraints are the most stringent to date over much of the mass ranges considered.

The GLUEX experiment at Jefferson Lab has been designed to study photoproduction reactions with a 9-GeV linearly polarized photon beam. The energy and arrival time of beam photons are tagged using a scintillator hodoscope and a scintillating fiber array. The photon flux is determined using a pair spectrometer, while the linear polarization of the photon beam is determined using a polarimeter based on triplet photoproduction. Charged-particle tracks from interactions in the central target are analyzed in a solenoidal field using a central straw-tube drift chamber and six packages of planar chambers with cathode strips and drift wires. Electromagnetic showers are reconstructed in a cylindrical scintillating fiber calorimeter inside the magnet and a lead-glass array downstream. Charged particle identification is achieved by measuring energy loss in the wire chambers and using the flight time of particles between the target and detectors outside the magnet. The signals from all detectors are recorded with flash ADCs and/or pipeline TDCs into memories allowing trigger decisions with a latency of 3.3 mu s. The detector operates routinely at trigger rates of 40 kHz and data rates of 600 megabytes per second. We describe the photon beam, the GLUEX detector components, electronics, data-acquisition and monitoring systems, and the performance of the experiment during the first three years of operation.

We report a measurement of the pi(-) photoproduction beam asymmetry for the reaction (gamma) over right arrowp -> pi(-)Delta(++) using data from the GLUEX experiment in the photon beam energy range 8.2-8.8 GeV. The asymmetry Sigma is measured as a function of four-momentum transfer t to the Delta(++) and compared to phenomenological models. We find that Sigma varies as a function of t : negative at smaller values and positive at higher values of vertical bar t vertical bar. The reaction can be described theoretically by t-channel particle exchange requiring pseudoscalar, vector, and tensor intermediaries. In particular, this reaction requires charge exchange, allowing us to probe pion exchange and the significance of higher-order corrections to one-pion exchange at low momentum transfer. Constraining production mechanisms of conventional mesons may aid in the search for and study of unconventional mesons. This is the first measurement of the process at this energy.

We propose to create a secondary beam of neutral kaons in Hall D at Jefferson Lab to be used with the GlueX experimental setup for strange hadron spectroscopy. The superior CEBAF electron beam will enable a flux on the order of 1× 10^4 K_L/sec, which exceeds the flux of that previously attained at SLAC by three orders of magnitude. The use of a deuteron target will provide first measurements ever with neutral kaons on neutrons. The experiment will measure both differential cross sections and self-analyzed polarizations of the produced Λ, Σ, Ξ, and Ω hyperons using the GlueX detector at the Jefferson Lab Hall D. The measurements will span CM cosθ from -0.95 to 0.95 in the range W = 1490 MeV to 2500 MeV. The new data will significantly constrain the partial wave analyses and reduce model-dependent uncertainties in the extraction of the properties and pole positions of the strange hyperon resonances, and establish the orbitally excited multiplets in the spectra of the Ξ and Ω hyperons. Comparison with the corresponding multiplets in the spectra of the charm and bottom hyperons will provide insight into he accuracy of QCD-based calculations over a large range of masses. The proposed facility will have a defining impact in the strange meson sector through measurements of the final state Kπ system up to 2 GeV invariant mass. This will allow the determination of pole positions and widths of all relevant K^∗(Kπ) S-,P-,D-,F-, and G-wave resonances, settle the question of the existence or nonexistence of scalar meson κ/K_0^∗(700) and improve the constrains on their pole parameters. Subsequently improving our knowledge of the low-lying scalar nonet in general.

The past few years has seen tremendous progress in our understanding of short-range correlated (SRC) pairing of nucleons within nuclei, much of it coming from electron scattering experiments leading to the break-up of an SRC pair. The interpretation of these experiments rests on assumptions about the mechanism of the reaction. These assumptions can be directly tested by studying SRC pairs using alternate probes, such as real photons. We propose a 30-day experiment using the Hall D photon beam, nuclear targets, and the GlueX detector in its standard configuration to study short-range correlations with photon-induced reactions. Several different reaction channels are possible, and we project sensitivity in most channels to equal or exceed the 6 GeV-era SRC experiments from Halls A and B. The proposed experiment will therefore decisively test the phenomena of np dominance, the short-distance NN interaction, and reaction theory, while also providing new insight into bound nucleon structure and the onset of color transparency.

We report measurements of the photon beam asymmetry $\mathrm{\ensuremath{\Sigma}}$ for the reaction $\stackrel{P\vec}{\ensuremath{\gamma}}p\ensuremath{\rightarrow}{K}^{+}{\mathrm{\ensuremath{\Sigma}}}^{0}$(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected by using a linearly polarized photon beam in the energy range of 8.2--8.8 GeV incident on a liquid hydrogen target. The beam asymmetry $\mathrm{\ensuremath{\Sigma}}$ was measured as a function of the Mandelstam variable $t$, and a single value of $\mathrm{\ensuremath{\Sigma}}$ was extracted for events produced in the $u$ channel. These are the first exclusive measurements of the photon beam asymmetry $\mathrm{\ensuremath{\Sigma}}$ for the reaction in this energy range. For the $t$ channel, the measured beam asymmetry is close to unity over the $t$ range studied, $\ensuremath{-}t=(0.1--1.4)\phantom{\rule{3.33333pt}{0ex}}$($\mathrm{GeV}/{c)}^{2}$, with an average value of $\mathrm{\ensuremath{\Sigma}}=1.00\ifmmode\pm\else\textpm\fi{}0.05$. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the ${K}^{*}$(892) Regge trajectory. A value of $\mathrm{\ensuremath{\Sigma}}=0.41\ifmmode\pm\else\textpm\fi{}\phantom{\rule{3.33333pt}{0ex}}0.09$ is obtained for the $u$ channel integrated up to $\ensuremath{-}u=2.0$ ($\mathrm{GeV}/{c)}^{2}$.

We report measurements of the photon beam asymmetry Σ for the reaction γp→K+Σ0 (1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected by using a linearly polarized photon beam in the energy range of 8.2–8.8 GeV incident on a liquid hydrogen target. The beam asymmetry Σ was measured as a function of the Mandelstam variable t , and a single value of Σ was extracted for events produced in the u channel. These are the first exclusive measurements of the photon beam asymmetry Σ for the reaction in this energy range. For the t channel, the measured beam asymmetry is close to unity over the t range studied, − t = ( 0.1 – 1.4 ) ( GeV / c ) 2 , with an average value of Σ = 1.00 ± 0.05 . This agrees with theoretical models that describe the reaction via the natural-parity exchange of the K ∗ (892) Regge trajectory. A value of Σ = 0.41 ± 0.09 is obtained for the u channel integrated up to − u = 2.0 ( GeV / c ) 2 .

We report measurements of the photon beam asymmetry Sigma for the reaction (gamma) over right arrowp -> K+Sigma(0) (1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected by using a linearly polarized photon beam in the energy range of 8.2-8.8 GeV incident on a liquid hydrogen target. The beam asymmetry Sigma was measured as a function of the Mandelstam variable t, and a single value of Sigma was extracted for events produced in the u channel. These are the first exclusive measurements of the photon beam asymmetry Sigma for the reaction in this energy range. For the t channel, the measured beam asymmetry is close to unity over the t range studied, -t = (0 .1-1 .4) (GeV/c)(2) , with an average value of Sigma = 1 .00 +/- 0 .05. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the K*(892) Regge trajectory. A value of Sigma = 0 .41 +/- 0 .09 is obtained for the u channel integrated up to -u = 2 .0 (GeV/c)(2).

We report measurements of the photon beam asymmetry Σ for the reaction γ⃗ p→ K^+Σ^0(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected using a linearly polarized photon beam in the energy range of 8.2-8.8 GeV incident on a liquid hydrogen target. The beam asymmetry Σ was measured as a function of the Mandelstam variable t, and a single value of Σ was extracted for events produced in the u-channel. These are the first exclusive measurements of the photon beam asymmetry Σ for the reaction in this energy range. For the t-channel, the measured beam asymmetry is close to unity over the t-range studied, -t=(0.1-1.4)(GeV/c)^2, with an average value of Σ = 1.00± 0.05. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the K^*(892) Regge trajectory. A value of Σ = 0.41 ± 0.09 is obtained for the u-channel integrated up to -u=2.0 (GeV/c)^2.

We report on the measurement of the beam asymmetry Sigma for the reactions (gamma) over right arrowp -> p eta and (gamma) over right arrowp -> p eta' from the GlueX experiment using an 8.2-8.8-GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Laboratory. These measurements are made as a function of momentum transfer -t with significantly higher statistical precision than our earlier. measurements and are the first measurements of eta' in this energy range. We compare the results to theoretical predictions based on t-channel quasiparticle exchange. We also compare the ratio of Sigma(eta) to Sigma(eta)' to these models as this ratio is predicted to be sensitive to the amount of s (s) over bar exchange in the production. We find that photoproduction of both eta and eta' is dominated by natural parity exchange with little dependence on -t.

A. Ali, M. Amaryan, E. G. Anassontzis, A. Austregesilo, M. Baalouch, F. Barbosa, J. Barlow, A. Barnes, E. Barriga, T. D. Beattie, V. V. Berdnikov, T. Black, W. Boeglin, M. Boer, W. J. Briscoe, T. Britton, W. K. Brooks, B. E. Cannon, N. Cao, E. Chudakov, S. Cole, O. Cortes, V. Crede, M. M. Dalton, T. Daniels, A. Deur, S. Dobbs, A. Dolgolenko, R. Dotel, M. Dugger, R. Dzhygadlo, H. Egiyan, A. Ernst, P. Eugenio, C. Fanelli, S. Fegan, A. M. Foda, J. Foote, J. Frye, S. Furletov, L. Gan, A. Gasparian, V. Gauzshtein, 26 N. Gevorgyan, C. Gleason, K. Goetzen, A. Goncalves, V. S. Goryachev, L. Guo, H. Hakobyan, A. Hamdi, S. Han, J. Hardin, G. M. Huber, A. Hurley, D. G. Ireland, M. M. Ito, N. S. Jarvis, R. T. Jones, V. Kakoyan, G. Kalicy, M. Kamel, C. Kourkoumeli, S. Kuleshov, I. Kuznetsov, 26 I. Larin, D. Lawrence, D. I. Lersch, H. Li, W. Li, B. Liu, K. Livingston, G. J. Lolos, V. Lyubovitskij, 26 D. Mack, H. Marukyan, V. Matveev, M. McCaughan, M. McCracken, W. McGinley, J. McIntyre, C. A. Meyer, R. Miskimen, R. E. Mitchell, F. Mokaya, F. Nerling, L. Ng, A. I. Ostrovidov, Z. Papandreou, M. Patsyuk, P. Pauli, R. Pedroni, L. Pentchev, K. J. Peters, W. Phelps, E. Pooser, N. Qin, J. Reinhold, B. G. Ritchie, L. Robison, D. Romanov, C. Romero, C. Salgado, A. M. Schertz, R. A. Schumacher, J. Schwiening, K. K. Seth, X. Shen, M. R. Shepherd, E. S. Smith, D. I. Sober, A. Somov, S. Somov, O. Soto, J. R. Stevens, I. I. Strakovsky, V. Tarasov, S. Taylor, A. Teymurazyan, A. Thiel, G. Vasileiadis, D. Werthmüller, T. Whitlatch, N. Wickramaarachchi, M. Williams, T. Xiao, Y. Yang, J. Zarling, Z. Zhang, G. Zhao, Q. Zhou, X. Zhou, and B. Zihlmann

Neutron interferometry at the National Institute of Standards and Technology is a well-established program that performs experiments in a wide range of areas including materials science, quantum information, precision measurements of coherent and incoherent scattering lengths, and dark energy/fifth force searches. Central to the continued success of this program is the further understanding and elimination of instabilities and coherence-losses whether they are from thermal, vibrational, or dynamical sources. We have spent considerable effort in fabricating new interferometer crystals which have higher maximum fringe visibilities and that can be tailored to specific experiments. We describe the current facilities and a new post-machining fabrication process of crystal annealing.