A measurement of the proton spin structure function g1p(x,Q{sup 2}) in deep-inelastic scattering is presented. The data were taken with the 27.6 GeV longitudinally polarised positron beam at HERA ...incident on a longitudinally polarised pure hydrogen gas target internal to the storage ring. The kinematic range is 0.021<x<0.85 and 0.8 GeV{sup 2}<Q{sup 2}<20 GeV{sup 2}.
The CLAS forward electromagnetic calorimeter Amarian, M.; Asryan, G.; Beard, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2001, Letnik:
460, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab utilizes six iron-free superconducting coils to provide an approximately toroidal magnetic field. The six sectors are instrumented ...individually to form six independent spectrometers. The forward region (8°<
θ<45°) of each sector is equipped with a lead–scintillator electromagnetic sampling calorimeter (EC), 16
radiation lengths thick, using a novel triangular geometry with stereo readout. With its good energy and position resolution, the EC is used to provide the primary electron trigger for CLAS. It is also used to reject pions, reconstruct π° and η decays and detect neutrons. This paper treats the design, construction and performance of the calorimeter.
The time-of-flight technique for the HERMES experiment Airapetian, A.; Akopov, N.; Amarian, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2005, Letnik:
540, Številka:
2
Journal Article
Recenzirano
Odprti dostop
This paper describes the use of the time-of-flight (TOF) technique as a particle identification method for the HERMES experiment. The TOF is measured by two
1
×
4
m
2
scintillation hodoscopes that ...initially were designed only for the first-level trigger. However, the suitable time structure of the HERA electron beam allows an extension of their functions to also measure the TOF for low momentum hadron identification. Using only these conventional hodoscopes, good particle identification was achieved for protons and pions in the momentum range up to
2.9
GeV
/
c
and for kaons up to
1.5
GeV
/
c
.
Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel pK0S→pπ+π−. A peak is observed in the pK0S invariant mass spectrum at ...1528±2.6(stat)±2.1(syst) MeV. Depending on the background model, the naive statistical significance of the peak is 4–6 standard deviations and its width may be somewhat larger than the experimental resolution of σ=4.3–6.2 MeV. This state may be interpreted as the predicted S=+1 exotic Θ+(uudds̄) pentaquark baryon. No signal for an hypothetical Θ++ baryon was observed in the pK+ invariant mass distribution. The absence of such a signal indicates that an isotensor Θ is excluded and an isovector Θ is unlikely.
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