46 research outputs found
Operation and performance of CMS silicon tracking detector
No full textThe experiments now operating at the CERN Large Hadron Collider all include large, state of the art silicon detector systems for measuring the trajectories of charged particles from the proton-proton collisions. The CMS silicon tracking detector is the largest silicon tracking detector every built, with almost 10 million microstrip sensor elements and 66 million pixels. It has been operating very successfully since collisions began in late 2009 and the performance is very consistent with the design goals. Results from the early operation will be shown and comments made on the challenges of designing and constructing such systems
CMS Tracker Commissioning using cosmic muon data
No full textMany physics channels, and in particular events containing top quarks, produce b jets in the final state which need to be distinguished from more copious backgrounds containing only light flavored jets. Tagging of b-jets, mainly relies upon relatively distinct properties of b-hadrons such as large proper lifetime, large mass, decays to final states with high charged track multiplicities. Precise spatial reconstruction close to the interaction point and efficient track reconstruction are key ingredients for all b-tagging algorithms. These rely on stable, low noise, low occupancy and highly efficient tracking detectors. This is a short review of the results of the studies on the CMS tracker performances carried out with cosmics at the CERN Tracker Integration Facility from march to july 2007, in order to show how this performance is in line with the requirement of the CMS community for a good b-tagging
The CMS Silicon Tracker: From the Performance Study in Cosmic Runs to the Measurement of the Momentum Resolution from the Z Line-Shape in Early Data
No full textHIV incidence estimate combining HIV/AIDS surveillance, testing history information and HIV test to identify recent infections in Lazio, Italy
No full textAbstract Background The application of serological methods in HIV/AIDS routine surveillance systems to identify persons with recently acquired HIV infection has been proposed as a tool which may provide an accurate description of the current transmission patterns of HIV. Using the information about recent infection it is possible to estimate HIV incidence, according to the model proposed by Karon et al. in 2008, that accounts for the effect of testing practices on the number of persons detected as recently infected. Methods We used data from HIV/AIDS surveillance in the period 2004-2008 to identify newly diagnosed persons. These were classified with recent/non-recent infection on the basis of an avidity index result, or laboratory evidence of recently acquired infection (i.e., previous documented negative HIV test within 6 months; or presence of HIV RNA or p24 antigen with simultaneous negative/indeterminate HIV antibody test). Multiple imputation was used to impute missing information. The incidence estimate was obtained as the number of persons detected as recently infected divided by the estimated probability of detection. Estimates were stratified by calendar year, transmission category, gender and nationality. Results During the period considered 3,633 new HIV diagnoses were reported to the regional surveillance system. Applying the model, we estimated that in 2004-2008 there were 5,465 new infections (95%CI: 4,538-6,461); stratifying by transmission category, the estimated number of infections was 2,599 among heterosexual contacts, 2,208 among men-who-have-sex-with-men, and 763 among injecting-drug-users. In 2008 there were 952 (625-1,229) new HIV infections (incidence of 19.9 per 100,000 person-years). In 2008, for men-who-have-sex-with-men (691 per 100,000 person-years) and injecting drug users (577 per 100,000 person-years) the incidence remained comparatively high with respect to the general population, although a decreasing pattern during 2004-2008 was observed for injecting-drug-users. Conclusions These estimates suggest that the transmission of HIV infection in Lazio remains frequent and men-who-have-sex-with men and injecting-drug-users are still greatly affected although the majority of new infections occurs among heterosexual individuals.</p
Stand-alone cosmic muon reconstruction before installation of the CMS silicon strip tracker
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Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at root s=0.9 and 2.36 TeV
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