A beam physics model server (Art++) has been developed for the Jefferson Lab accelerator. This online model server is a redesign of the ARTEMIS model server. The need arose from an impedance mismatch ...between the current requirements and ARTEMIS capabilities. The purpose of the model server is to grant access to both static (machine lattice parameters) and dynamic (actual machine settings) data using a single programming interface. A set of useful optics calculations (R-matrix, orbit fit, etc.) has also been implemented and can be invoked by clients via the model interface. Clients may also register their own dynamic models in the server. The server interacts with clients using the CDEV protocol and data integrity is guaranteed by a relational database (Oracle8i) accessed through a persistence layer. By providing a centralized repository for both data and optics calculations, the following benefits were achieved: optimal use of network consumption, software reuse, and ease of maintenance.
We present a search at Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling \(\alpha'\) to electrons. Such a particle \(A'\) can be produced in electron-nucleus ...fixed-target scattering and then decay to an \(e^+e^-\) pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175--250 MeV, found no evidence for an \(A'\to e^+e^-\) reaction, and set an upper limit of \(\alpha'/\alpha \simeq 10^{-6}\). Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.
We have measured the ratio ital gsup ital psub 1/ital Fsup ital psub 1 over the range 0.029ltital xlt0.8 and 1.3ltital Qsup 2lt10 (GeV/ital c)sup 2 using deep-inelastic scattering of polarized ...electrons from polarized ammonia. An evaluation of the integral integralital gsup ital psub 1(ital x,ital Qsup 2)ital dx at fixed ital Qsup 2=3 (GeV/ital c)sup 2 yields 0.127plus minus0.004(stat)plus minus0.010(syst), in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160plus minus0.006. In the quark-parton model, this implies Deltaital q=0.27plus minus0.10.
The ratio
g
1
F
1
has been measured over the range 0.03 <
x < 0.6 and 0.3 <
Q
2 < 10 (GeV/
c)
2 using deep-inelastic scattering of polarized electrons from polarized protons and deuterons. We find
g
...1
F
1
to be consistent with no
Q
2-dependence at fixed
x in the deep-inelastic region
Q
2 > 1 (
GeV/
c)
2. A trend is observed for
g
1
F
1
to decrease at lower
Q
2. Fits to world data with and without a possible
Q
2-dependence in
g
1
F
1
are in agreement with the Bjorken sum rule, but
Δ
q
is substantially less than the quark-parton model expectation.
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