F. J. Wickens

First measurement of efficiency and precision of CCD detectors for high energy physics

Abstract It has been known for some time that a 2-dimensional charge-coupled device (CCD) might be used for detecting high energy particles with high precision and excellent 2-track resolution. Such detectors could be used to distinguish between prompt tracks and decay products in events producing short-lived particles (heavy leptons, charm, beauty etc.). We now present results in which (for the first time) a telescope of CCD detectors has been operated in a beam of high energy particles. The main results are that even these early detectors have excellent performance characteristics, namely efficiency for track detection of 98±2% per plane, spatial resolution of 4.3 μm and 6.1 μm in two orthogonal directions and 2-track resolution of 40 μm in space.

Diffractive Production of Strange Mesons at 63-{GeV}

Abstract Nearly 200 000 examples of the diffractive process K − p → K − π − π + p at 63 GeV have been obtained using a two magnet spectrometer equipped with Cerenkov counters for secondary particle identification. In addition some 2000 examples of the process K − p → ω K − p have been obtained. The K ππ data have been subjected to partial-wave analysis. The dominant J P = 1 + system couples to K ∗ π , in both S and D waves, ϱ K, κπ and e K. The data confirm the existence of two J P = 1 + Q mesons and their masses, widths and branching ratios are given. The ifωK data show that the couplings of the Q mesons to ω K are approximately equal to the couplings to ϱ 0 K. The two 1 + nonets expected in the quark model are discussed in the light of this and other recent experiments. There is strong evidence for a broad J P = 0 − resonance at about 1.46 GeV. At higher masses, structure in the J P = 2 − partial waves establishes the existence of at least one J P = 2 − L meson.

Diffractive production of 3π states at 63 and 94 GeV

Diffractive production of the 3π system has been studied at 63 and 94 GeV using a two magnet spectrometer with high, uniform acceptance. The total number of events used in the analysis is ∼600 000. The A2 meson is shown to be diffractively produced. The existence of a resonant component in both the 1+ and 2− enhancements is established and resonance parameters for the corresponding A1 and A3 mesons are given. There are several indications in the data of states which would correspond to radial excitations in the quark model.

Measurement of the mass and width of the charmed meson D∗+ (2010)

Abstract Using a high-resolution silicon vertex detector we have observed a very clean signal of 127 D∗+. After a careful study of the experimental resolution of our apparatus we have measured m( D ∗++ )−m( D 0 ) = 145.39±0.06±0.03 MeV . We have also obtained a 90% CL upper limit to γ(D∗+) of 131 keV.

Charge-coupled devices for particle detection with high spatial resolution

It is expected that the 1980s will see an intensive study of particles with higher flavours (charm, beauty, etc). There is consequently interest in detectors with good spatial resolution which can distinguish between tracks emerging from the primary vertex and those from secondary vertices due to the decay of these short lived particles. In this paper, we consider the possible application of a thin microelectronic device (the charge-coupled device) for this purpose. We conclude that a modest development of existing CCDs could yield a detector with the following characteristics: a) 2-dimensional spatial measurement in orthogonal directions with precision ~ 3 µm. b) 2-track resolution of ~ 60 µm, with no confusion from tracks which overlap in only one projection. c) time resolution ~ 500 nsec. d) readout time ~ 4 msec. e) radiation hardness ~ 3 × 105 rads, equivalent to 1 year of operation in a typical hadron beam of 106 particles per burst.

Inclusive φ-meson production in 93 and 63 GeV hadron interactions

Abstract The inclusive reactions h+p→φ+X, (h=π±,,K±,p±), are studied for 0⪅xF⪅0.3 and p⊥ ⩽ 1 GeV at 93 and and 63 GeV incident momentum. Differential cross sections dσ/dp⊥2 anddσ/dxF are presented and are compared with predictions of the naive parton model.

Radiation damage in silicon strip detectors

Abstract Silicon strip detectors with 5 μm spatial resolution have been used during 1982–1985 in the ACCMOR spectrometer at CERN. After a local beam flux of about 1014 minimum ionizing particles per cm2 we observe a significant increase in dark current and systematic distortions in the measured coordinates which are explained in terms of a decrease in the effective donor concentration.

Production of the charmed baryon Λ+c in π−Cu and K−Cu interactions at 230 GeV

Abstract We present results from the NA32 experiment at CERN on the production characteristics of the charmed baryon Λ + c in 230 GeV π − Cu and K − Cu interactions. A high resolution vertex detector consisting of change-coupled devices and silicon microstrip detectors allowed the selection of a very clean sample of 154 Λ + c → pK − π + (and charge conjugate) decays. Results on differential and integrated cross sections are given.

Measurement of the lifetime of the charmed baryon Λc

Abstract We present results on a sample of Λc decays obtained in the NA32 experiment in 1985 using charge-coupled devices for vertex reconstruction and a trigger on Λc→pK−π+ (and charge conjugate). We observe a distinct peak at the Λc mass on zero background. The lifetime of the Λc is determined to be (1.4±0.30.5±0.3)x10−13 s based on a sample of 14 events.

Experimental proof of the existence of the A1 meson

Abstract In partial wave analyses of the ( π − π − π + ) system, substantial shape changes of the 1 + S ( ϱπ ) intensity as a function of t , and relative phase changes of ≈ 90°, provide compelling evidence for a resonant A 1 of mass ≈ 1280 MeV and width ≈ 300 MeV.