SNO+

Abstract:

We present the status of the development of the readout electronics for the large area silicon tracker of the ATLAS experiment at the LHC, carried out by the CERN RD2 project. Our basic readout concept is to integrate a fast amplifier, analog memory, sparse data scan circuit and analog-to-digital convertor (ADC) on a single VLSI chip. This architecture will provide full analog information of charged particle hits associated unambiguously to one LHC beam crossing, which is expected to be at a frequency of 40 MHz. The expected low occupancy of the ATLAS inner silicon detectors allows us to use a low speed (5 MHz) on-chip ADC with a multiplexing scheme. The functionality of the fast amplifier and analog memory have been demonstrated with various prototype chips. Most recently we have successfully tested improved versions of the amplifier and the analog memory. A piecewise linear ADC has been fabricated and performed satisfactorily up to 5 MHz. A new chip including amplifier, analog memory, memory controller, ADC, and data buffer has been designed and submitted for fabrication and will be tested on a prototype of the ATLAS silicon tracker module with realistic electrical and mechanical constraints.

Abstract:

Charge asymmetry has been measured using 19 039 W decays recorded by the Collider Detector at Fermilab during the 1992-93 run of the Tevatron Collider. The asymmetry is sensitive to the ratio of d and u quark distributions to x<0.01 at Q2MW2, where nonperturbative effects are minimal. It is found that of the two current sets of parton distributions, those of Martin, Roberts, and Stirling are favored over the sets most recently produced by the CTEQ Collaboration. The W asymmetry data provide stronger constraints on du ratio than the recent measurements of F2μnF2μp which are limited by uncertainties originating from deuteron corrections. © 1995 The American Physical Society.

Abstract:

This Letter describes a direct measurement of the W boson decay width, Γ(W), using the high-mass tail of the transverse mass spectrum of W→eν decays recorded by the Collider Detector at Fermilab. We findΓ(W)=2.11±0.28(stat)±0.16(syst) GeV and compare this direct measurement with indirect means of obtaining the width. © 1995 The American Physical Society.

Abstract:

We have used a kinematic technique to distinguish top quark pair production from background in pp collisions at s=1.8 TeV, applied to 67 pb-1 of data. We define a sample of W+3 jet events in which the jets are produced at large angles relative to the incident beams. In this sample, we find an excess of events with large jet transverse energies relative to expectations from background. The excess is consistent with top quark production; a large fraction of events in this kinematic region contains b jets. We interpret these results as evidence that most of the selected events are from tt decay.