Measurement of the cross sections for inclusive electron scattering in the E12-14-012 experiment at Jefferson Lab
M. Murphy, H. Dai, L. Gu, D. Abrams, A. M. Ankowski, B. Aljawrneh, S. Alsalmi, J. Bane, S. Barcus, O. Benhar, V. Bellini, J. Bericic, D. Biswas, A. Camsonne, J.… 展开作者
M. Murphy, H. Dai, L. Gu, D. Abrams, A. M. Ankowski, B. Aljawrneh, S. Alsalmi, J. Bane, S. Barcus, O. Benhar, V. Bellini, J. Bericic, D. Biswas, A. Camsonne, J. Castellanos, J. -P. Chen, M. E. Christy, K. Craycraft, R. Cruz-Torres, D. Day, S. -C. Dusa, E. Fuchey, T. Gautam, C. Giusti, J. Gomez, C. Gu, T. Hague, J. -O. Hansen, F. Hauenstein, D. W. Higinbotham, C. Hyde, C. M. Jen, C. Keppel, S. Li, R. Lindgren, H. Liu, C. Mariani, R. E. McClellan, D. Meekins, R. Michaels, M. Mihovilovic, D. Nguyen, M. Nycz, L. Ou, B. Pandey, V. Pandey, K. Park, G. Perera, A. J. R. Puckett, S. N. Santiesteban, S. Širca, T. Su, L. Tang, Y. Tian, N. Ton, B. Wojtsekhowski, S. Wood, Z. Ye, J. Zhang
The E12-14-012 experiment performed at Jefferson Lab Hall A has collected inclusive electron-scattering data for different targets at the kinematics corresponding to beam energy 2.222 GeV and scattering angle 15.54 deg. Here we present a comprehensive analysis of the collected data and compare the double-differential cross sections for inclusive scattering of electrons, extracted using solid targets (aluminum, carbon, and titanium) and a closed argon-gas cell. The data extend over broad range of energy transfer, where quasielastic interaction, Delta-resonance excitation, and inelastic scattering yield contributions to the cross section. The double-differential cross sections are reported with high precision (~3%) for all targets over the covered kinematic range.
This white paper summarizes the scientific opportunities for utilization of the upgraded 12 GeV Continuous Electron Beam Accelerator Facility (CEBAF) and associated experimental equipment at Jefferson Lab. It is based on the 52 proposals recommended for approval by the Jefferson Lab Program Advisory Committee.The upgraded facility will enable a new experimental program with substantial discovery potential to address important topics in nuclear, hadronic, and electroweak physics.
The Jefferson Lab facilities have undergone a substantial upgrade, both of accelerator, CEBAF, and of the experimental installations. We will discuss the progress to completion of these facilities, the status of accelerator commissioning, and the recent first operations for physics. We will then flesh out the anticipated exciting physics program of the next several years.
We comment on the important phenomenological aspects of the recent high-statistics and wide-angle coverage $ϕ$ photoproduction data from CLAS at Jefferson Lab. The most prominent feature is a localized structure at a center-of-mass (c.m) energy $\sqrt{s} \sim 2.2$ GeV that is not expected in a simple $t$-channel Pomeron-exchange model. The structure exists only at the forward production angles that almost rules out any resonance contribution. Strong rescattering effects between the $p ϕ$ and $K^+Λ(1520)$ channels could be possible explanations. The analyses of both charged- ($ϕ\to K^+ K^-$) an…
Over the past decade measurements of unpolarized structure functions at Jefferson Lab with unprecedented precision have significantly advanced our knowledge of nucleon structure. These have for the first time allowed quantitative tests of the phenomenon of quark-hadron duality, and provided a deeper understanding of the transition from hadron to quark degrees of freedom in inclusive scattering. Dedicated Rosenbluth-separation experiments have yielded high-precision transverse and longitudinal structure functions in regions previously unexplored, and new techniques have enabled the first glimps…
For the first time, baryon-antibaryon photoproduction in the reaction $γp \to Λ\barΛ p$ has been observed at photon energies from threshold near 4.9 GeV to 11.6 GeV. The measurements are in progress with the GlueX spectrometer in Hall D at Jefferson Lab. We describe here the apparatus and methods used to make these measurements and outline the physics goals of the work. Some of the newly-seen reaction phenomenology is presented.
The cross section of the exclusive $π^0$ and $η$ electroproduction reaction $ep\to e^\prime p^\prime π^0/η$ was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4σ/dtdQ^2dx_Bdϕ$ and structure functions $σ_T+εσ_L, σ_{TT}$ and $σ_{LT}$ as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. The data are compared with the GPD based theoretical models. Analyses find that a large dominance of transverse processes is necessary to explain the experimental results. Generalized form factors of the transversity GPDs $H_T^{π,η}$…
The Continuous Electron Beam Accelerator Facility (CEBAF) and associated experimental equipment at Jefferson Lab comprise a unique facility for experimental nuclear physics. This facility is presently being upgraded, which will enable a new experimental program with substantial discovery potential to address important topics in nuclear, hadronic, and electroweak physics. Further in the future, it is envisioned that the Laboratory will evolve into an electron-ion colliding beam facility.
The Continuous Electron Beam Accelerator Facility (CEBAF) and associated experimental equipment at Jefferson Lab comprise a unique facility for experimental nuclear physics. This facility is presently being upgraded, which will enable a new experimental program with substantial discovery potential to address important topics in nuclear, hadronic, and electroweak physics. Further in the future, it is envisioned that the Laboratory will evolve into an electron-ion colliding beam facility.
It has recently been demonstrated that a program of parasitic electron-beam fixed-target experiments would have powerful discovery potential for dark matter and other new weakly-coupled particles in the MeV-GeV mass range. The first stage of this program can be realized at Jefferson Laboratory using an existing plastic-scintillator detector downstream of the Hall D electron beam dump. This paper studies the physics potential of such an experiment and highlights its unique sensitivity to inelastic "exciting" dark matter and leptophilic dark matter scenarios. The first of these is kinematically …
Construction of the 12 GeV upgrade to the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility is presently underway. This upgrade includes doubling the energy of the electron beam to 12 GeV, the addition of a new fourth experimental hall, and the construction of upgraded detector hardware. An overview of this upgrade project is presented, along with highlights of the anticipated experimental program.
This paper reports the measurement of polarized and unpolarized cross sections for the ep -> e'p' reaction, which is comprised of Deeply Virtual Compton Scattering (DVCS) and Bethe-Heitler (BH) processes, at an electron beam energy of 5.88 GeV at the Thomas Jefferson National Accelerator Facility using the Large Acceptance Spectrometer CLAS. The unpolarized cross sections and polarized cross section differences have been measured over broad kinematics, 0.10 < x_B < 0.58, 1.0 < Q^2 < 4.8 GeV^2, and 0.09 < -t < 2.00 GeV^2. The results are found to be consistent with previous CLAS data, and these…
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 $t = (P_γ-P_ω)^2$ and photon energy $E_γ$ using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cross sections are measured in the energy range $1.4 < E_γ < 3.4$ GeV. A model based on $ω-N$ rescattering is consistent with the data at low and intermediate momentum transfer, $|t|$. For $2.8 < E_γ < 3.4$ GeV, the total cross-section of $ω-N$ scattering, based on fits within the framework of the Vector Meson Dominance mod…
APEX is an experiment at Thomas Jefferson National Accelerator Facility (JLab) in Virginia, USA, that searches for a new gauge boson ($A^\prime$) with sub-GeV mass and coupling to ordinary matter of $g^\prime \sim (10^{-6} - 10^{-2}) e$. Electrons impinge upon a fixed target of high-Z material. An $A^\prime$ is produced via a process analogous to photon bremsstrahlung, decaying to an $e^+ e^-$ pair. A test run was held in July of 2010, covering $m_{A^\prime}$ = 175 to 250 MeV and couplings $g^\prime/e \; \textgreater \; 10^{-3}$. A full run is approved and will cover $m_{A^\prime} \sim$ 65 to …
The Jupiter Electron Scattering Program at Jefferson Lab
JUPITER（Jlab Unified Program to Investigate Nuclear Targets and Electroproduction of Resonances）是核物理电子散射和高能物理中微子散射社区之间的一项新合作，旨在用电子和中微子束研究核子和核的结构。JUPITER的第一阶段是Hall C实验E04-001，关于核目标的包容性电子散射。E04-001的首次数据运行目前计划于2005年1月进行。
Future experiments at the Jefferson Lab 12 GeV upgrade, in particular, the Solenoidal Large Intensity Device (SoLID), aim at a very precise data set in the region where the partonic structure of the nucleon is dominated by the valence quarks. One of the main goals is to constrain the quark transversity distributions. We apply recent theoretical advances of the global QCD extraction of the transversity distributions to study the impact of future experimental data from the SoLID experiments. Especially, we develop a simple strategy based on the Hessian matrix analysis that allows one to estimate…
Measurement of the semi-inclusive pi+ electroproduction off the proton, performed with CLAS detector at Jefferson Lab, has been presented. The obtained fully-differential cross sections, including the azimuthal angle between hadronic and leptonic planes, phi, allowed us to separate the phi-dependent terms. While, the phi-independent part of the cross section was found to be in good agreement with current fragmentation pQCD calculations.
The $π_1(1600)$, a $J^{PC} = 1^{-+}$ exotic meson has been observed by experiments using pion beams. Theorists predict that photon beams could produce gluonic hybrid mesons, of which the $π_1(1600)$ is a candidate, at enhanced levels relative to pion beams. The g12 rungroup at Jefferson Lab's CEBAF Large Acceptance Spectrometer (CLAS) has recently acquired a large photoproduction dataset, using a liquid hydrogen target and tagged photons from a 5.71 GeV electron beam. A partial-wave analysis of 502K $γp \to π^+π^+π^-n$ events selected from the g12 dataset has been performed, and preliminary fi…
The Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility provides CW electron beams with high intensity, remarkable stability, and a high degree of polarization. These capabilities offer new and unique opportunities to search for novel particles and forces that would require extension of the standard model. CEBAF is presently undergoing an upgrade that includes doubling the energy of the electron beam to 12 GeV and enhancements to the experimental equipment. This upgraded facility will provide increased capability to address new physics be…
The COMPASS collaboration published precise data on production cross section of charged hadrons in lepton-hadron semi-inclusive deep inelastic scattering, showing almost an order of magnitude larger than next-to-leading order QCD calculations when $P_{h_T}$ and $z_h$ are sufficiently large. We explore the role of power corrections to the theoretical calculations, and quantitatively demonstrate that the power corrections are extremely important for these data when the final-state multiplicity is low and the production kinematics is near the edge of phase space. Our finding motivates more detail…
A wide range of nucleon and nuclear structure experiments in Jefferson Lab's Hall A require precise, continuous measurements of the polarization of the electron beam. In our Compton polarimeter, electrons are scattered off photons in a Fabry-Perot cavity; by measuring an asymmetry in the integrated signal of the scattered photons detected in a GSO crystal, we can make non-invasive, continuous measurements of the beam polarization. Our goal is to achieve 1% statistical error within two hours of running. We discuss the design and commissioning of an upgrade to this apparatus, and report prelimin…
The Heavy Photon Search experiment (HPS) at Jefferson Laboratory will search for a new $U(1)$ massive gauge boson, or "heavy-photon," mediator of a new fundamental interaction, called "dark-force," that couples to ordinary photons trough kinetic mixing. HPS has sensitivity in the mass range 20 MeV - 1 GeV and coupling $\varepsilon^2$ between 10$^{-5}$ and 10$^{-10}$. The HPS experiment will search for the $e^+e^-$ decay of the heavy photon, by resonance search and detached vertexing, in an electron beam fixed target experiment. HPS will use a compact forward spectrometer, which employs silicon…
The Heavy Photon Search (HPS) is a new experiment at Jefferson Lab that will search for heavy U(1) vector bosons (heavy photons or dark photons) in the mass range of 20 MeV/c$^2$ to 1 GeV/c$^2$. Dark photons in this mass range are theoretically favorable and may mediate dark matter interactions. The dark photon couples to electric charge through kinetic mixing with the photon, allowing its production through a process analogous to bremsstrahlung radiation. HPS will utilize this production mechanism to probe dark photons with relative couplings of $ε^2 = α'/α$ ~ $10^{-5}$ to $10^{-10}$ and sear…
We introduce a new phenomenological tool based on momentum region indicators to guide the analysis and interpretation of semi-inclusive deep-inelastic scattering measurements. The new tool, referred to as "affinity", is devised to help visualize and quantify the proximity of any experimental kinematic bin to a particular hadron production region, such as that associated with transverse momentum dependent factorization. We apply the affinity estimator to existing HERMES and COMPASS data and expected data from Jefferson Lab and the future Electron-Ion Collider. We also provide an interactive not…
Recent experimental and theoretical ideas are laying the ground for a new era in the knowledge of the parton structure of nuclei. We report on two promising directions beyond inclusive deep inelastic scattering experiments, aimed at, among other goals, unveiling the three dimensional structure of the bound nucleon. The 3D structure in coordinate space can be accessed through deep exclusive processes, whose non-perturbative content is parametrized in terms of generalized parton distributions. In this way the distribution of partons in the transverse plane will be obtained, providing a pictorial…
We perform a combined analysis of inclusive electron scattering data from $A=3$ nuclei in the deep-inelastic and quasielastic scattering regions, using Monte Carlo analysis methods and the nuclear weak binding approximation to establish the range over which the data can be described within the same theoretical framework. Comparison with quasielastic $^3$He cross sections from SLAC and Jefferson Lab suggests that most features of the $x \gtrsim 1$ data can be reasonably well described in the impulse approximation with finite-$Q^2$ nuclear smearing functions for momentum transfers $Q^2 \gtrsim 1…
We present the complete cross-section for the production of unpolarized hadrons in semi-inclusive deep-inelastic scattering up to power-suppressed ${\cal O}(1/Q^2)$ terms in the Wandzura--Wilczek-type approximation which consists in systematically assuming that $\bar{q}gq$--terms are much smaller than $\bar{q}q$--correlators. We compute all twist-2 and twist-3 structure functions and the corresponding asymmetries, and discuss the applicability of the Wandzura--Wilczek-type approximations on the basis of available data. We make predictions that can be tested by data from Jefferson Lab, COMPASS,…
The worm-gear transverse momentum dependent (TMD) function $g_{1T}$ is one of the eight leading-twist TMDs and has the probabilistic interpretation of finding a longitudinally polarized quark inside a transversely polarized hadron. In this work, we present the first simultaneous extraction of $g_{1T}$ from all the available experimental measurements. The study involves the analysis of COMPASS, HERMES, and Jefferson Lab data on semi-inclusive deep-inelastic scattering using Monte Carlo techniques. We also compare $g_{1T}$ obtained from this experimental data with different theoretical approache…
We provide the first rigorous numerical analysis of the longitudinal-transverse double-spin asymmetry $A_{LT}$ in electron-nucleon and proton-proton collisions for the case where only a single pion, jet, or photon is detected in the final state. Given recent extractions of certain, previously unknown, non-perturbative functions, we are able to compute contributions from all terms relevant for $A_{LT}$ and make realistic predictions for the observable at Jefferson Lab (JLab) 12 GeV, COMPASS, the future Electron-Ion Collider, and the Relativistic Heavy Ion Collider. We also compare our results t…
We have measured the moment $A_{LU}^{\sinϕ}$ corresponding to the polarized electron beam-spin asymmetry in SIDIS. $A_{LU}^{\sinϕ}$ is a twist-3 quantity providing information about quark-gluon correlations. Data were taken with the CLAS Spectrometer at Jefferson Lab using a 5.498 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. All three pion channels ($π^+$, $π^0$ and $π^-$) were measured simultaneously over a large range of kinematics within the virtuality range $Q^2 \approx$ 1.0-4.5 GeV$^2$. The observable was measured with better than 1% statistical pr…
The success of the ambitious programs of both long- and short-baseline neutrino-oscillation experiments employing liquid-argon time-projection chambers will greatly rely on the precision with which the weak response of the argon nucleus can be estimated. In the E12-14-012 experiment at Jefferson Lab Hall A, we have studied the properties of the argon nucleus by scattering a high-quality electron beam off a high-pressure gaseous argon target. Here, we present the measured $^{40}$Ar$(e,e^{\prime})$ double differential cross section at incident electron energy $E=2.222$~GeV and scattering angle $…
This report presents a brief summary of the science opportunities and program of a polarized medium energy electron-ion collider at Jefferson Lab and a comprehensive description of the conceptual design of such a collider based on the CEBAF electron accelerator facility.
