Test beam performance measurements for the Phase I upgrade of the CMS pixel detector

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is (99.95 ± 0.05) %, while the intrinsic spatial resolutions are (4.80 ± 0.25) μm and (7.99 ± 0.21) μm along the 100 μm and 150 μm pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.Peer reviewe

THE ISOLATION OF PROTOPLASTS FROM BACILLUS MEGATERIUM BY CONTROLLED TREATMENT WITH LYSOZYME

Certain bacteria are killed and rapidly lysed following exposure to the enzyme lysozyme. Lysozyme sensitivity resulting in extensive lysis occurs in a relatively restricted number of species: notably Micrococcus lysodeikticus, Sarcina lutea, and certain Bacillus spp. It was shown some years ago (Epstein and Chain, 1940; Meyer and Hahnel, 1946) that a mucopolysac-charide extractable from the cells of M. lyso-deikticus could be depolymerized by the enzyme with liberation of reducing sugars. More recently, Salton (1952) has found that the isolated cell walls of M. lysodeikticus can be rapidly and completely dissolved by treatment with lysozyme. Tomesik and Guex-Holzer (1952), working with a Bacillus sp, have given cytological evidence for the specific action of lysozyme on the bacterial cell wall. It appears, therefore, that lysozyme is a polysaccharase and that its action on suscep-tible bacteria consists of a specific destruction of the fabric of the cell wall. This interpretation is supported by recent chemical analyses (Salton, 1953) on the isolated cell walls of a number of bacteria; the walls of lysozyme sensitive organ-isms are closely similar in composition and markedly different from the walls of lysozyme resistant species. Hence the treatment of suscep-tible bacteria with lysozyme should constitute a method of unrivalled specificity and gentleness for the isolation of the structural elements within the cells-a method which avoids the wholesale disorganization of cellular components which results from cell breakage by mechanical abrasion or sonic treatment. It will be shown in this paper that it is possible to isolate the bacterial protoplast as an entity I This investigation was supported in part by a grant-in-aid made to Dr. R. Y. Stanier by the American Cancer Society on recommendation of the Committee on Growth of the Nationa