John A. J. Matthews

Temperature dependence of the radiation induced change of depletion voltage in silicon PIN detectors

Abstract We present a study of how temperature affects the change in the depletion voltage of silicon PIN detectors damaged by radiation. We study the initial radiation damage and the short-term and long-term annealing of that damage as a function of temperature in the range from −10°C to +50°C, and as a function of 800 MeV proton fluence up to 1.5×10 14 p/cm 2 . We express the pronounced temperature dependences in a simple model in terms of two annealing time constants which depend exponentially on the temperature.

THE SILICON VERTEX DETECTOR OF THE COLLIDER DETECTOR AT FERMILAB

Abstract A silicon microstrip vertex detector has been constructed and installed in the Collider Detector at Fermilab. The device has been designed to operate at a hadron collider. It began collecting data in May of 1992 and has functioned within specification. Technical details are presented on all aspects of the system and its performance.

The CDF SVX: A silicon vertex detector for a hadron collider

Abstract A silicon microstrip vertex detector is being constructed as an upgrade to the CDF detector at the Fermilab Tevatron-1 p p collider. This device, which is designed to operate in the hadron collider environment, should allow the tagging of long-lived heavy flavors produced in p p collisions. The mechanical and electronic design of this device are described in this paper.

BULK RADIATION DAMAGE IN SILICON DETECTORS AND IMPLICATIONS FOR LHC EXPERIMENTS

Abstract Bulk radiation damage to high resistivity n-type silicon detectors was studied with incident π + (190 MeV) and protons (500, 647 or 800 MeV). Silicon bulk damage constants were extracted based on proton fluences, Φ, up to ∼8 × 10 13 cm −2 and for π + fluences up to ∼3 × 10 13 cm −2 . Although the measured damage constants for π + and for proton irradiations were different, a simple empirical relationship was proposed to relate the π + and proton radiation damage data. In addition: (a) Activation time constants for reverse annealing were determined at four temperatures between 0°C and 50°C. (b) 8 silicon detectors were exposed to a second proton fluence of ∼3 × 10 13 cm −2 . The resulting changes in the effective dopant concentration, N eff , were consistent with a model where the bulk radiation effects were purely additive. (c) Following reverse annealing the bulk radiation damage to high resistivity n-type silicon detectors was consistent with the simple functional form: N eff ( Φ ) = N eff (0)e − cΦ − ( g c + g Y ) Φ , with c , g c and g Y damage coefficients measured for π + and proton radiation. The measured damage coefficients were used to provide predictions for the depletion voltage for the innermost pixel and silicon strip layers in the large detectors at the LHC.

The Mark II silicon strip vertex detector

Abstract A silicon strip vertex detector consisting of 36 modules has been built and operated in the Mark II solenoidal detector at the Stanford Linear Collider. The construction of the detector modules, their performance tests, the stability and accuracy of their placement, and the precision alignment of the complete device prior to and after installation are discussed. We also describe the operation of the vertex detector, and we discuss the measurement of impact parameters of charged particle tracks in conjunction with the Mark II wire drift chambers.

Spatial Resolution of the PEP-4 Time Projection Chamber

The spatial resolution and response of the segmented cathode pads of the PEP-4 TPC have been measured with data taken at 8.5 atmospheres of 80% Argon-20% Methane gas with a 4kG magnetic field. The dependence of the spatial resolution and pad response on drift distance and track-anode crossing angle is presented.

Measurement of Ionization Loss in the Relativistic Rise Region with the Time Projection Chamber

We present here some results obtained with the LBL Time Projection Chamber (TPC) regarding the particle identification by the measurement of the ionization losses in the relativistic rise region. This includes the method of calibration using 55Fe sources, the measurement of the resolution using cosmic rays, which shows an equivalent K-¿ separation of 4.8 standard deviations at 3.5 GeV/c, and the preliminary results obtained with multihadronic events from e+e- annihilations.

Inclusive γ and π0 production cross sections and energy fractions ine+e− annihilation at 29 GeV

Inclusive production cross sections for photons and π0s ine+e− annihilation at a center of mass energy of 29 GeV have been measured. The π0 production spectrum agrees with a corresponding measurement for π±. The ratio of the π0 inclusive rate to the average for π± is 0.92±0.14. The fractions of the total energy carried by photons and π0s are 0.244±0.016 and 0.217±0.033, respectively. The fraction of total energy carried by all stable hadrons, prompt leptons and photons is determined to be 0.938±0.045, leaving 0.062±0.045 for neutrinos.

A parameterization of cosmic ray shower profiles based on shower width

Cosmic ray (CR) air showers, detected via the air fluorescence technique, are reconstructed in part using functions that parameterize the longitudinal profile of each shower. The profile parameterization yields the position of shower maximum, Xmax in gm cm−2, which is sensitive to the incident CR particle type: e.g. p, C/N/O, Fe or γ. The integral of the profile is directly related to the shower energy. The Pierre Auger fluorescence reconstruction uses the Gaisser–Hillas (GH) four-parameter form [5]. The HiRes group has used both the Gaisser–Hillas form and a three-parameter Gaussian in age form [7]. Historically analytic shower theory suggested yet other forms; the best known is a three-parameter form popularized by Greisen [6]. Our work now uses the shower full width half-maximum, fwhm, and shower asymmetry parameter, f, to unify the parameterization of all three profile functions. Furthermore, shower profiles expressed in terms of the new parameters: fwhm, f, have correlations greatly reduced over e.g. Gaisser–Hillas parameters X0, λ. This allows shower profile reconstructions to add constraints (if needed) on the mostly uncorrelated parameters fwhm, f.

Power laws and the cosmic ray energy spectrum

Abstract Two separate statistical tests are applied to the AGASA and preliminary Auger cosmic ray energy spectra in an attempt to find deviation from a pure power-law. The first test is constructed from the probability distribution for the maximum event of a sample drawn from a power-law. The second employs the TP-statistic, a function defined to deviate from zero when the sample deviates from the power-law form, regardless of the value of the power index. The AGASA data show no significant deviation from a power-law when subjected to both tests. Applying these tests to the Auger spectrum suggests deviation from a power-law. However, potentially large systematics on the relative energy scale prevent us from drawing definite conclusions at this time.