We report on the design, construction and performance of a prototype for a high-granularity tile hadronic calorimeter for a future international linear collider detector. Scintillating tiles are read ...out via wavelength-shifting fibers that guide the scintillation light to a novel photodetector, the silicon photomultiplier. A prototype has been tested using a positron test beam at DESY. The results are compared with a reference prototype calorimeter equipped with multichannel vacuum photomultipliers. Detector calibration, noise, linearity and stability are discussed, and the energy response in a 1–6
GeV positron beam is compared with simulations. The present results demonstrate that the silicon photomultiplier is well-suited as photodetectors in calorimeters and thus has been selected for the construction of a
1
m
3
calorimeter prototype to operate in hadron beams.
Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The ...asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.
The luminosity monitor of the HERMES experiment at DESY Benisch, Th; Bernreuther, S.; Devitsin, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2001, Letnik:
471, Številka:
3
Journal Article
Recenzirano
A detector is described which measures the luminosity of the HERMES experiment at DESY. It is based on the coincident detection of electron–positron and photon pairs, or electron pairs, originating ...from the interaction of the beam positrons, or electrons, with the electrons of the atomic gas target. It consists of two calorimeters with radiation hard NaBi(WO
4)
2 crystals. Properties of the monitor, investigated in an electron test beam, and its performance in the experiment are presented.
Light yield, light pulse shape due to /spl gamma/-rays and /spl alpha/-particles, energy and time resolutions for three different samples of the LSO scintillator were studied using an XP2020Q ...photomultiplier and an S3590-03 photodiode. Light yields of 4200/spl plusmn/200 phe/MeV and 18500/spl plusmn/900 e-h pair/MeV were measured for the PM tube and the photodiode, respectively. The light pulse shape exhibits a pure exponential decay with a time constant of 47.2/spl plusmn/1.3 ns for both /spl gamma/-rays and /spl alpha/-particles. Energy resolutions of 10% and 14.6% for the 662 keV /spl gamma/-rays from a /sup 137/Cs source were obtained for the photomultiplier and the photodiode readout, respectively. A time resolution of 180 ns was observed for /sup 60/Co /spl gamma/-rays at 1 MeV threshold and 400 ps for 100 keV threshold. The study confirmed a number of advantages of the LSO scintillator for nuclear physics experiments, however, for small size samples. For larger volumes the natural radioactivity of the LSO, about 300 counts/s/cm/sup 3/, may limit possible applications. The high number of e-h pairs produced in the photodiodes makes LSO very attractive for small compact scintillation probes.< >
The performance of prototype vacuum phototriodes is presented from the first full sized supercrystal array for the CMS ECAL endcaps. The array was exposed to high-energy electrons and tested in ...magnetic fields of up to 3T, in the CERN North area, in July and August 1999. The mean VPT electron yield, normalised to a naked crystal light yield of 8photoelectrons/MeV into an HPMT, was found to be 25electrons/MeV at 3T for devices from Research Institute Electron, 35electrons/MeV for devices from Hamamatsu and 18/23electrons/MeV from Electron Tubes.
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.
Tests of a prototype for the electromagnetic calorimeter (ECAL) of the compact muon solenoid experiment (CMS) at the large hadron collider are described. The basic unit for the endcap ECAL in CMS is ...a “supercrystal” of 25 lead tungstate crystals. Results are presented from tests of the first full-sized supercrystal in electron beams and in a 3
T magnetic field. The supercrystal was exposed to electron beams with energies from 25 to 180
GeV. An energy resolution (
σ
E/
E) of (0.48±0.01)% was measured at 180
GeV.
The influence of fluorination of a batch mixture on the scintillation properties of fluorohafnate glasses in the HfF4-BaF2-CeF3-AlF3-NaF-InF3 system was studied. A new technique of batch treatment, ...comprising additional fluorination by chlorine trifluoride and Xe difluoride in gaseous phase at the elevated temperatures was proposed. Transmission spectra before and after gamma-irradiation as well as light yield of the glasses were studied. The radiation hardness of glasses increases as a result of the fluorination treatment. The presence of reduced Hf3+ ions and O impurities should cause the formation of radiation colouring centres and decrease the radiation hardness of scintillating HfF4-based glasses, doped with Ce3+. 11 refs.
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.
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