Browsing by Subject "CERN"
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Item Oral history interview with Gérard Le Lann by Andrew L. Russell(Charles Babbage Institute, 2012-04-03) Le Lann, GérardGérard Le Lann describes his first experiences with computers in the 1960s, and his work on the Cyclades project in France and the Arpanet in the United States in the 1970s. He explains how the field of distributed computing came into being in the 1970s, the conflict between the respective advocates of “datagrams” and “virtual circuits,” and his collaboration with Vint Cerf and Arpanet designers at Stanford University. The interview concludes with some reflections on the management of innovation in France and the United States. This set of nine interviews conducted with Tilly Bayard-Richard, Najah Naffah, Louis Pouzin, Marc E. Levilion, Michel Gien, Jean-Louis Grangé, Gérard Le Lann, Rémi Després, and André Danthine was funded by the ACM History Committee with a fellowship on “European Contributions to Computer Networks: An Oral History Project.”Item Search for heavy stable charged particles at the CMS experiment(2012-10) Cooper, Seth Isaacmethod of searching for Heavy Stable Charged Particles (HSCP) using dE/dx and momentum measurements from the CMS inner tracking system is presented. The shape of the dE/dx distribution is used to distinguish background from signal, in combination with slicing the data into bins of pseudorapidity and number of dE/dx measurements, which together extend and improve on a previous analysis conducted as a counting experiment. In particular, the expected minimum cross section to make a discovery of 5-sigma significance is reduced, and expected upper limits are more restrictive. The data are consistent with the background-only hypothesis and are used to set upper limits on the production cross section as a function of mass for several different HSCP models. The data sample used was collected by the CMS detector in 2011 pp collisions at sqrt(s) = 7 TeV, corresponding to approximately 5/fb.Item Search for Long-Lived Neutral Particles in Final States with Delayed Photon and Missing Transverse Energy from Proton-Proton Collisions Using the CMS detector.(2015-11) Tambe Ebai, NorbertWe perform a search for long-lived neutral particles in final state with delayed photons and large missing transverse energy produced in LHC proton-proton collisions at center-of-mass energy, $\sqrt{s} = 8$TeV. Capitalizing on the excellent timing resolution of the CMS Electromagnetic Calorimeter the search uses photon time measurements made by the Electromagnetic Calorimeter as the main search quantity. We found a single event consistent with our background expectations from the Standard Model and set a model-independent upper limit of 4.37 on number of signal events. We also interpret our results in the context of the SPS8 benchmark GMSB model and show that neutralinos with mean lifetime, $\tau_{\PSneutralinoOne} \leq 45$ns, and mass, $m_{\PSneutralinoOne} \leq 300$GeV/c^{2}, or effective Supersymmetry breaking energy scale, $\Lambda \leq 220TeV$, are ruled out of existence at 95\% $CL_{S}$ confidence level. The exclusion limit on the product of the production cross-section and branching ratio of the neutralino to photon and gravitino decay channel, $\sigma_{(\PSneutralinoOne \rightarrow \gamma + \tilde{G})}\times BR$, for different lifetimes and masses is derived. Our results confirm for the first time that the CMS Electromagnetic Calorimeter provides good sensitivity to search for long-lived neutral particles with lifetimes up to $40$ns and masses up to $300$GeV/c^{2}using only timing measurements.