Recoil detection at future QCD facilities van Beuzekom, M.G.; van der Steenhoven, G.; Steijger, J.J.M.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2003, Volume:
513, Issue:
1
Journal Article
Peer reviewed
Fixed target experiments at future deep-inelastic scattering facilities, such as the proposed TESLA-N and EVELIN projects, require the detection of particles at larger angles than will be covered by ...the forward-angle spectrometers, typically foreseen in such high-luminosity experiments. The large-angle particles mostly correspond to recoil protons that can be used to identify exclusive processes, which currently are of high interest as they give access to the Generalized Parton Distributions. For this purpose a large-angle detector needs to be developed. The resolution and particle identification capability that can be achieved with a small detector consisting of a few silicon layers has been investigated. The detector is assumed to perform multiple sampling of the ionization tracks caused by high momentum (<2
GeV
c
−1) pions, kaons, and protons in the silicon. Realistic models for the noise of the read-out electronics and segmentation of the detectors are used. The result of the study which is based on Monte Carlo simulations and—partly—calibrated by data, is a conceptual detector design with π, p, K separation up to 1.3
GeV
c
−1.
The exclusive electroproduction of π+ mesons was studied with the HERMES spectrometer at the DESY laboratory by scattering 27.6 GeV positron and electron beams off an internal hydrogen gas target. ...The virtual-photon cross sections were measured as a function of the Mandelstam variable t and the squared four momentum −Q2 of the exchanged virtual photon. A model calculation based on Generalized Parton Distributions is in fair agreement with the data at low values of |t| if power corrections are included. A model calculation based on the Regge formalism gives a good description of the magnitude and the t and Q2 dependences of the cross section.
Design and performance of a silicon test counter for HERMES Visser, J; van Beuzekom, M.G; Blouw, J ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2004, Volume:
521, Issue:
2
Journal Article
Peer reviewed
A small silicon-detector array has been designed and constructed to investigate the prospects for large-angle tracking and detection of recoiling target fragments for the HERMES experiment at DESY in ...Hamburg, Germany. The array consists of a two-layered double-sided Silicon Test Counter (STC), which is used to study the feasibility of this technique. The STC has been installed below the center of the HERMES internal storage cell target inside the vacuum chamber, and is thus located in the vicinity of the high-intensity lepton beam of HERA. For the readout, a local front-end with 64-channel Analog Pipeline Chips (APC) has been employed. The large dynamic range of the APC allows for the identification and tracking of protons with momenta ranging from 100 to
600
MeV/c
. The feasibility of the detector concept is shown, thus demonstrating that a multilayer silicon system can be used for the observation of recoiling protons produced in Deep Inelastic Scattering (DIS).
A measurement of the beam-spin asymmetry in the azimuthal distribution of pions produced in semi-inclusive deep-inelastic scattering off protons is presented. The measurement was performed using the ...HERMES spectrometer with a hydrogen gas target and the longitudinally polarized 27.6 GeV positron beam of HERA. The sinusoidal amplitude of the dependence of the asymmetry on the angle ϕ of the hadron production plane around the virtual photon direction relative to the lepton scattering plane was measured for π+, π− and π0 mesons. The dependence of this amplitude on the Bjorken scaling variable and on the pion fractional energy and transverse momentum is presented. The results are compared to theoretical model calculations.
Single-spin asymmetries for semi-inclusive pion production in deep-inelastic scattering have been measured for the first time. A significant target-spin asymmetry of the distribution in the azimuthal ...angle straight phi of the pion relative to the lepton scattering plane was formed for pi(+) electroproduction on a longitudinally polarized hydrogen target. The corresponding analyzing power in the sinstraight phi moment of the cross section is 0.022+/-0.005+/-0.003. This result can be interpreted as the effect of terms in the cross section involving chiral-odd spin distribution functions in combination with a chiral-odd fragmentation function that is sensitive to the transverse polarization of the fragmenting quark.
The Hermes experiment has investigated the tensor spin structure of the deuteron using the 27.6 GeV/c positron beam of DESY HERA. The use of a tensor-polarized deuteron gas target with only a ...negligible residual vector polarization enabled the first measurement of the tensor asymmetry A(d)zz and the tensor structure function b(d)1 for average values of the Bjorken variable 0.01< <0.45 and of the negative of the squared four-momentum transfer 0.5 GeV2 < <5 GeV2. The quantities A(d)zz and b(d)1 are found to be nonzero. The rise of b(d)1 for decreasing values of x can be interpreted to originate from the same mechanism that leads to nuclear shadowing in unpolarized scattering.
In 2005, the ANTARES Collaboration deployed and operated at a depth of 2500m a so-called Mini Instrumentation Line equipped with Optical Modules (MILOM) at the ANTARES site. The various data acquired ...during the continuous operation from April to December 2005 of the MILOM confirm the satisfactory performance of the Optical Modules, their front-end electronics and readout system, as well as the calibration devices of the detector. The in situ measurement of the Optical Module time response yields a resolution better than 0.5ns. The performance of the acoustic positioning system, which enables the spatial reconstruction of the ANTARES detector with a precision of about 10cm, is verified. These results demonstrate that with the full ANTARES neutrino telescope the design angular resolution of better than 0.3° can be realistically achieved.
The HERMES hydrogen and deuterium nuclear-polarized gas targets have been in use since 1996 with the polarized electron beam of HERA at DESY to study the spin structure of the nucleon. Polarized ...atoms from a Stern–Gerlach Atomic Beam Source are injected into a storage cell internal to the HERA electron ring. Atoms diffusing from the center of the storage cell into a side tube are analyzed to determine the atomic fraction and the atomic polarizations. The atoms have a nuclear polarization, the axis of which is defined by an external magnetic holding field. The holding field was longitudinal during 1996–2000, and was changed to transverse in 2001. The design of the target is described, the method for analyzing the target polarization is outlined, and the performance of the target in the various running periods is presented.
The ANTARES optical beacon system Aguilar, J.A.; Ameli, F.; Ardellier-Desages, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2007, Volume:
578, Issue:
3
Journal Article
Peer reviewed
ANTARES is a neutrino telescope being deployed in the Mediterranean Sea. It consists of a three-dimensional array of photomultiplier tubes that can detect the Cherenkov light induced by charged ...particles produced in the interactions of neutrinos with the surrounding medium. High angular resolution can be achieved, in particular, when a muon is produced, provided that the Cherenkov photons are detected with sufficient timing precision. Considerations of the intrinsic time uncertainties stemming from the transit time spread in the photomultiplier tubes and the mechanism of transmission of light in sea water lead to the conclusion that a relative time accuracy of the order of 0.5
ns is desirable. Accordingly, different time calibration systems have been developed for the ANTARES telescope. In this article, a system based on Optical Beacons, a set of external and well-controlled pulsed light sources located throughout the detector, is described. This calibration system takes into account the optical properties of sea water, which is used as the detection volume of the ANTARES telescope. The design, tests, construction and first results of the two types of beacons, LED and laser-based, are presented.
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