A Hadron Blind Detector for PHENIX Aidala, C.; Azmoun, B.; Fraenkel, Z. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2003, Volume:
502, Issue:
1
Journal Article
Peer reviewed
A Hadron Blind Detector (HBD) is proposed as upgrade of the PHENIX detector at RHIC, BNL. The HBD will allow the measurement of low-mass e+e− pairs from the decay of the light vector mesons ρ,ω,φ and ...the low-mass continuum- in Au–Au collisions at sNN=200GeV. From general considerations, the HBD has to identify electrons with a high efficiency (>90%) and with a double hit resolution better than 90%, it must have a pion rejection factor of at least 200 and a radiation budget of the order of 1% of a radiation length. The choice that emerges is a windowless Cherenkov detector, operated with a CF4 based gas mixture in a special proximity focus configuration with a CsI cathode evaporated on GEMs.
The direct reconstruction of the isospin I = 0 amplitudes is discussed under the assumption that the I = 1 amplitudes are known and that a sufficient number of independent np observables have been ...measured at a centre-of-mass angle θ. We show that at least one observable measured at angle π — θ is necessary in order to determine the I = 0 amplitudes, including the phase relative to the I = 1 amplitudes. Special cases at θ = 0, π/2 and π are also discussed.
A polarized proton beam from SATURNE II, the Saclay polarized targets with \(^6\)Li compounds, and an unpolarized \(\mathrm{CH}_2\) target were used to measure spin-dependent observables for protons ...scattered on bound nucleons. The beam and target polarizations were oriented vertically. The analyzing power \(A_{\mathrm{oono}}\) and the depolarization \(D_{\mathrm{nono}}\) were determined at seven energies between 1.1 and 2.4 GeV. The spin correlation parameter \(A_{\mathrm{oonn}}\) was measured at only 1.1 and 1.6 GeV. Measurements with the \(\mathrm{CH}_2\) target at 1.1 GeV provided \(A_{\mathrm{oono}}\) data for scattering of polarized protons on neutrons in carbon. The quasi-elastic observables are compared with previous elastic scattering measurements and at 1.1 GeV with predictions of phase shift analyses.
A SATURNE polarized target has been used for nucleon-nucleon elastic scattering and transmission experiments for 15 years. Continuous improvements resulted in a flexible and reliable facility for ...spin physics. The polarized proton target was a 70 cm
3 cartridge loaded with pentanol-2, a promising material according to the results obtained. The new acquisition system and data processing was based on the LabView/PC software and increased the accuracy of polarization measurements. For a polarized neutron target, two cartridges loaded with
6LiD and
6LiH were set in the refrigerator and could be quickly inserted in the beam. Results from the the first experiments using
6Li materials in quasielastic pp or pn analyzing power measurements are compared with the same observables measured in free nucleon-nucleon scattering using polarized proton targets. The angular resolution distributions for
θ
CM determination and azimuthal coplanarity are shown for different targets in nucleon-nucleon scattering. A comparison of analyzing power results for elastic and quasielastic scattering suggests that the contribution of inelastic processes to quasielastic pn scattering may be suppressed by additional constraints.
The polarization of extracted SATURNE II proton beam as a function of different ion source configurations was studied. Two distinct experiments were necessary for this purpose. In the first one, the ...LEFT-RIGHT instrumental asymmetry of the beam polarimeter was determined using an unpolarized beam. In the second one this correction factor was applied to asymmetries measured with the beam from the polarized ion source in all polarization states. The measurements were carried out at the proton beam kinetic energy 0.80 GeV, where the pp-elastic scattering analyzing power is near its maximum. The results confirmed that the two so-called “unpolarized states” of the source were polarized to several percent, whereas the absolute values of the beam polarizations in the so-called “polarized states” were equal and opposite. It was observed that the hexapole lens of the ion source produced beam polarization in the absence of any transition. The beam polarization as a function of hexapole current, transition field attenuation, and spin rotation solenoid current was measured. It was also shown how to obtain a strictly unpolarized beam using the polarized source only. The results obtained with the SATURNE II ion source HYPERION may also be relevant to similar sources at other accelerators.
A polarized proton beam extracted from SATURNE II, the Saclay polarized target with \(^6\)Li compounds, and a \(\mathrm{CH}_2\) target were used to measure elastic and quasi-elastic pp spin-dependent ...observables in the angular region \(60^{\circ} < \theta_{\mathrm{CM}} < 105^{\circ}\). The beam and/or target polarizations were oriented vertically. Accurate pp data for the analyzing power \(A_{\mathrm{oono}}\), spin-correlation parameter \(A_{\mathrm{oonn}}\), and the polarization transfer \(K_{\mathrm{onno}}\) were measured at 1.1 GeV. The observables \(A_{\mathrm{oono}}\) and \(K_{\mathrm{onno}}\) were determined at six other energies between 1.6 and 2.4 GeV. At 1.6 GeV, \(A_{\mathrm{oonn}}\) was also obtained. The individual contributions from H, \(^6\)Li, and \(^6\)LiD were deduced. The \(\mathrm{CH}_2\) target provided \(A_{\mathrm{oono}}(\mathrm{pp})\) results on free hydrogen and on protons in carbon. The elastic and quasi-elastic observables are compared with existing data and with phase-shift analysis predictions.
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