121886810
Experimental Results in DIS, SIDIS and DES from Jefferson Lab
Jefferson Lab’s electron accelerator in its present incarnation, with a maximum beam energy slightly above 6 GeV, has already enabled a large number of experiments expanding our knowledge of nucleon and nuclear structure (especially in Deep Inelastic Scattering—DIS—at moderately high x, and in the resonance region). Several pioneering experiments have yielded first results on Deeply Virtual Compton Scattering (DVCS) and other Deep Exclusive Processes (DES), and the exploration of the rich landscape of transverse momentum‐dependent (TMD) structure functions using Semi‐Inclusive electron scattering (SIDIS) has begun. With the upgrade of CEBAF to 12 GeV now underway, a significantly larger kinematic space will become available. The 12 GeV program taking shape will complete a detailed mapping of inclusive, TMD and generalized distribution functions for quarks, antiquarks and gluons in the valence region and beyond.
43786315
Multinucleon effects in muon capture on 3He at high energy transfer.
Energy spectra of both protons and deuterons emitted following the capture of negative muons by [sup 3]He nuclei have been measured for energies above 15 MeV. A limited number of proton-neutron pairs emitted in coincidence were also observed. A simple plane wave impulse approximation (PWIA) model calculation yields fair agreement with the measured proton energy spectra, but underpredicts the measured rate of deuteron production above our energy threshold by a large factor. A more sophisticated PWIA calculation for the two-body breakup channel, based on a realistic three-body wave function for the initial state, is closer to the deuteron data at moderate energies, but still is significantly lower near the kinematic end point. The proton-neutron coincidence data also point to the presence of significant strength involving more than one nucleon in the capture process at high energy transfer. These results indicate that additional terms in the capture matrix element beyond the impulse approximation contribution may be required to explain the experimental data. Specifically, the inclusion of nucleon-nucleon correlations in the initial or final state and meson exchange current contributions could bring calculations into better agreement with our data. A fully microscopic calculation would thus open the possibility for a quantitative testmore » of multinucleon effects in the weak interaction.« less
55178975
Measurement of the x- and Q(2)-dependence of the asymmetry A(1) on the nucleon
We report results for the virtual photon asymmetry A{sub 1} on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton ({sup 15}NH{sub 3}) and deuteron ({sup 15}ND{sub 3}) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present paper, we concentrate on our results for A{sub 1}(x,Q{sup 2}) and the related ratio g{sub 1}/F{sub 1}(x,Q{sup 2}) in the resonance and the deep inelastic regions for our lowest and highest beam energies, covering a range in momentum transfer Q{sup 2} from 0.05 to 5.0 GeV{sup 2} and in final-state invariant mass W up to about 3 GeV. Our data show detailed structure in the resonance region, which leads to a strong Q{sup 2}--dependence of A{sub 1}(x,Q{sup 2}) for W below 2 GeV. At higher W, a smooth approach to the scaling limit, established by earlier experiments, can be seen, but A{sub 1}(x,Q{sup 2}) is not strictly Q{sup 2}--independent. We add significantly to the world data set at high x, up to x = 0.6. Our data exceed the SU(6)-symmetric quark model expectation for both the proton and the deuteron whilemore » being consistent with a negative d-quark polarization up to our highest x. This data set should improve next-to-leading order (NLO) pQCD fits of the parton polarization distributions.« less
36168504
Measurements of cross sections relevant to gamma -ray line astronomy.
120397395
Measurement of the Helicity Asymmetry of the gamma-p Cross Section Between 2.5 and 5.3 GeV
We report a measurement of the helicity asymmetry of a substantial fraction of the gamma-p total cross section at photon energies between 2.5 and 5.3 GeV in Hall B of Jefferson Lab. The preliminary analysis uses only events with at least one charged particle between approximately 8 and 45 degrees. Assuming that the measured asymmetry applies also to the undetected portion of the cross section, we compare our preliminary result with the results of the Regge parameterization of Bianchi and Thomas.
126279241
Measurement of spin structure functions at moderate Q2 using CLAS
Abstract Spin structure functions of the nucleon in the region of large ξ and small to moderate Q 2 continue to be of high current interest. Among the topics one can study in this kinematic regime are spin-dependent resonance transition amplitudes and their interference with each other and the non-resonant background, the behavior of the asymmetry A 1 at large ξ, and the presence or absence of local duality in spin structure functions. The first moment of the spin structure function g 1 goes through a rapid transition from the photon point ( Q 2 = 0), where it is constrained by the Gerasimov-Drell-Hearn sum rule, to the deep inelastic limit where it is sensitive to the nucleon spin fraction carried by quarks. This opens up the possibility to study the transition from hadronic to quark degrees of freedom over the whole range of Q 2 . Recently, we concluded a large experimental program to measure these observables with polarized proton and deuteron targets at Jefferson Lab. A highly polarized electron beam, solid polarized NH 3 and ND 3 targets and the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B were used to accumulate over 23 billion events with 4 different beam energies of 1.6, 2.5, 4.2 and 5.7 GeV. We present an overview of the experiment, its kinematic coverage and its statistical power. We show final results from the first run at 2.5 GeV and 4 GeV and preliminary results from the 5.7 GeV and the 1.6 GeV data sets.
41938556
Short Strips for the sLHC: A P-Type Silicon Microstrip Detector in 3-D Technology
The luminosity upgrade of the Large Hadron Collider (LHC), the sLHC, will constitute an extremely challenging radiation environment for tracking detectors. With respect to the LHC, large improvements in radiation hardness are required. In this paper, we investigated the expected radiation hardness of the 3-D-design, where rows of 3-D-columns are etched in substrate material and joined together to form strips. To investigate the feasibility of 3-D silicon strip detectors (SSD) for the sLHC, we have built prototype modules using 3-D single type column (3-D-STC) strip detectors with short strips and front-end electronics from the present ATLAS SemiConductor Tracker (SCT). The modules were tested with a beta source setup before and after irradiation to sLHC fluences with 26 MeV protons. We report on the performance of these 3-D-modules, compare it to the results prior to irradiation, and draw conclusions about options for using 3-D SSD detectors for tracking at the sLHC.
26356337
Investigation of 3D silicon microstrip detectors for the sLHC
An increase of the luminosity of the Large Hadron Collider (LHC) at CERN is foreseen around 2017 by about an order of magnitude. This will translate into a largely increased radiation dose, with which the present trackers can not cope. The development of radiation-hard silicon detectors is required for the innermost tracking layers. One option for radiation-hard silicon sensors is the 3D technology, where columnar electrodes are etched, perpendicular to the surface, into the silicon bulk. In this paper we investigated 3D single type columns (3D-STC) detectors which were irradiated with 26 MeV protons to fluences up to 2.5×10 15 1-MeV equivalent neutrons(Neq)/cm 2 which corresponds to fluences expected at the inner tracking layers of the sLHC. Before and after irradiations the sensors were tested with a beta-source setup to measure and quantify the radiation induced damage.
25295548
Short strips for the SLHC: A P-Type Silicon microstrip detector in 3D-technology
The luminosity upgrade of the Large Hadron Collider (LHC), the sLHC, will constitute an extremely challenging radiation environment for tracking detectors. With respect to the LHC, massive improvements in radiation hardness are required. In this paper we investigate the superior radiation hardness of the 3D-design, where rows of 3D-columns are etched in substrate material and joined together to form strips. To demonstrate the feasibility of 3D silicon strip detectors (SSDs) for the sLHC, we have built prototype modules using 3D single type column (3D-STC) strip detectors with short strips and front-end electronics from the present ATLAS SemiConductor Tracker (SCT). The modules were tested with a beta source setup before and after irradiation to sLHC fluences with 26 MeV protons. We report on the performance of these 3D-modules, compare it to the results prior to irradiation, and draw conclusions about options for using 3D SSDs for tracking at the sLHC.