Ph. Demierre

Apparatus for the measurement of spin dependent observables in np and pp elastic and quasi-elastic scattering

Abstract The present article describes an apparatus used for the measurement of spin dependent observables at SATURNE II. Observables for np elastic and quasi-elastic scattering were measured between 0.31 and 1.1 GeV, those for pp elastic scattering between 1.94 and 2.24 GeV. Measurements of pn and pp observables with an unpolarized 6LiD and 7LiH targets around 2 GeV were also carried out. Fast electronics, on-line data acquisition, event selection and off-line analysis are presented.

Spin-dependent neutron-proton total cross section differences ΔσL and ΔσT from 140 to 590 MeV

Abstract A polarized neutron beam at PSI has been used to measure the spin-dependent neutron-proton total cross sections Δσ L and Δσ T from 140 to 590 MeV. The results are compared with recent phase-shift calculations.

Angular dependence of analyzing power in np elastic scattering between 0.312 and 1.10 GeV

Abstract We present a total of 427 np analyzing power data points in a large angular interval at 12 energies between 0.312 and 1.10 GeV. The SATURNE II polarized beam of free monochromatic neutrons was scattered either on the Saclay frozen-spin polarized proton target or on CH2 and C targets. Present results are compared with existing elastic and quasieleastic data.

Observation of a narrow structure in the pp elastic scattering observable Aoonn at Tkin=2.11 GeV

Abstract The angular dependece of the pp elastic scattering spin correlation parameter was measured in the angular range from 60° to 97° CM at 14 energies between 1.96 and 2.23 GeV. A rapid decrease of the energy dependence of this observable at 90° CM is observed around 2.11 GeV kinetic energy. This agrees with the behavior of A oonn predicted on the basis of an exotic six-quark structure. The A oonn (90° CM ), together with the known differential cross section, allows the determination of the absolute value of the pure spin-singlet amplitude. The energy dependence of this amplitude shows a shoulder centered at 2.11 GeV, corresponding to a total mass of 2.735 GeV and an estimated width of 17 MeV.

Angular dependence of the beam and target analyzing powers Aoono and Aooon in np elastic scattering between 0.477 and 0.940 GeV

Abstract We present a total of 273 independent data points of the analyzing powers A oono (nP) and A ooon (nP) in a large angular interval at four energies between 0.477 and 0.940 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. Part of the data was obtained with a CH 2 target. A comparison of the two measured observables allows one to determine the polarization of the neutron beam. The present results provide an important contribution to any future theoretical or phenomenological analysis.

ATLAS beam test results

Abstract Many different configurations of electronics and semiconductor strip detectors were studied in 1995 using the ATLAS tracking detector test area at the H8 beam-line of the CERN SPS. A significant fraction of these investigations are presented elsewhere in this volume and this paper will concentrate on the results with silicon strip detectors read out with electronics preserving the pulse height information. Data has been collected with the ADAM, APV5 and FElix read-out chips on a number of different detectors. The first results are presented for read out with LHC electronics of detectors to the ATLAS-A specification of 112.5 μm pitch, employing n-strips in n-type silicon, capacitive coupling and intermediate strips. It is demonstrated that with adequate signal/noise, a spatial resolution of ⋍13 μm is attainable with these detectors.

The pp elastic scattering analyzing power measured with the polarized beam and the unpolarized target between 1.98 and 2.80 GeV

Abstract A polarized proton beam extracted from SATURNE II was scattered on an unpolarized CH2 target. The angular distribution of the beam analyzing power Aoono was measured at large angles from 1.98 to 2.8 GeV and at 0.80 GeV nominal beam kinetic energy. The same observable was determined at the fixed mean laboratory angle of 13.9° in the same energy range. Both measurements are by-products of an experiment measuring the spin correlation parameter Aoon.

Dependence of proton beam polarization on ion source transition configurations

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.

Test results on silicon micro-strip detectors for ATLAS

We report results from beam tests on silicon microstrip detectors using a binary readout system for ATLAS. The data were collected during the H8 beam test at CERN in August/September 1995 and the KEK test in February 1996. The binary modules tested had been assembled from silicon microstrip detectors of different layout and from front-end electronics chips of different architecture. The efficiency, noise occupancy and position resolution were determined as a function of the threshold setting for various bias voltages and angles of incidence for both irradiated and non-irradiated detectors. In particular, the high spatial resolution of the beam telescope allowed the evaluation of the performance as a function of the track location in between detector strips.

Monitoring the performance of silicon detectors with binary readout in the ATLAS beam test

The monitoring of the performance of silicon strip systems with binary readout is discussed. Due to the fact that neither pulse height nor noise level are recorded, the system is monitored with the efficiency and noise occupancy. As an example, on-line monitoring of the binary silicon strip system at the ATLAS H8 beam test at CERN is described.