4,297 research outputs found

    The CMS Tracker Readout Front End Driver

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    The Front End Driver, FED, is a 9U 400mm VME64x card designed for reading out the Compact Muon Solenoid, CMS, silicon tracker signals transmitted by the APV25 analogue pipeline Application Specific Integrated Circuits. The FED receives the signals via 96 optical fibers at a total input rate of 3.4 GB/sec. The signals are digitized and processed by applying algorithms for pedestal and common mode noise subtraction. Algorithms that search for clusters of hits are used to further reduce the input rate. Only the cluster data along with trigger information of the event are transmitted to the CMS data acquisition system using the S-LINK64 protocol at a maximum rate of 400 MB/sec. All data processing algorithms on the FED are executed in large on-board Field Programmable Gate Arrays. Results on the design, performance, testing and quality control of the FED are presented and discussed

    Hard mtm_t Corrections as a Probe of the Symmetry Breaking Sector

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    Non-decoupling effects related to a large mtm_t affecting non-oblique radiative corrections in vertices (ZbˉbZ\bar{b}b) and boxes (BB-Bˉ\bar{B} mixing and Ï”K\epsilon_K) are very sensitive to the particular mechanism of spontaneous symmetry breaking. We analyze these corrections in the framework of a chiral electroweak standard model and find that there is only one operator in the effective lagrangian which modifies the longitudinal part of the W+W^+ boson without touching the oblique corrections. The inclusion of this operator affects the ZbˉbZ\bar{b}b vertex, the BB-Bˉ\bar{B} mixing and the CP-violating parameter Ï”K\epsilon_K, generating interesting correlations among the hard mt4log⁥mt2m_t^4 \log m_t^2 corrections to these observables, for example, the maximum vertex ZbbˉZ b\bar{b} correction allowed by low energy physics is about one percent.Comment: LaTex, 8 pages, 1 postscript figure include

    Recent Results on the Performance of the CMS Tracker Readout System

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    The CMS Silicon Tracker comprises a complicated set of hardware and software components that have been thoroughly tested at CERN before final integration of the Tracker. A vertical slice of the full readout chain has been operated under near-final conditions. In the absence of the tracker front-end modules, simulated events have been created within the FED (Front End Driver) and used to test the readout reliability and efficiency of the final DAQ (Data Acquisition). The data are sent over the S-Link 64 bit links to the FRL(Fast Readout Link) modules at rates in excess of 200 MBytes/s per FED depending on setup and conditions. The current tracker DAQ is fully based on the CMS communication and acquisition tool XDAQ. This paper discusses setup and results of a vertical slice of the full Tracker final readout system comprising 2 full crates of FEDs, 30 in total, read out through 1 full crate of final FRL modules. This test is to complement previous tests done at Imperial College[3] taking them to the next level in order to prove that a complete crate of FRLs using the final DAQ system, including all subcomponents of the final system both software and hardware with the exception of the detector modules themselves, is capable of sustained readout at the desired rates and occupancy of the CMS Tracker. Simulated data are created with varying hit occupancy (1-10%) and Poisson distributed trigger rates (<200KHz) and the resulting behaviour of the system is recorded. Data illustrating the performance of the system and data readout are presented

    Field screening of biofumigant species for the reduction of potato cyst nematodes (Globodera sp.)

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    Summary Potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis are the most problematic potato pests in the UK. Management of PCN is often reliant on use of nematicides; however, pesticide registration and approval is becoming increasingly stringent and the likelihood of nematicides being retracted from commercial use more probable. Biofumigation represents a potential alternative. The process involves growing a green manure for maceration and incorporation into soil whereby intracellular glucosinolate (GSL) molecules are hydrolyzed to pesticidal volatiles such as isothiocyanate gases. The experiment detailed in this paper represents one of the first studies to investigate biofumigant species and blends for efficacy against PCN in-field, and for varietal suitability to UK conditions. Statistical differences (P&lt;0.001) in PCN egg viability were found between the untreated control and biofumigant treatments, but no difference between biofumigant treatments was recorded. Overall, biofumigation was shown to reduce encysted egg viability by approximately 42%. Additionally, fresh (P=0.008) and dry weight (P=0.044) biomass was found to be variable between biofumigant species and blends. All biofumigants were found to be suitable for UK conditions when grown between September and November

    New Physics at the LHC. A Les Houches Report: Physics at TeV Colliders 2009 - New Physics Working Group

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    We present a collection of signatures for physics beyond the standard model that need to be explored at the LHC. First, are presented various tools developed to measure new particle masses in scenarios where all decays include an unobservable particle. Second, various aspects of supersymmetric models are discussed. Third, some signatures of models of strong electroweak symmetry are discussed. In the fourth part, a special attention is devoted to high mass resonances, as the ones appearing in models with warped extra dimensions. Finally, prospects for models with a hidden sector/valley are presented. Our report, which includes brief experimental and theoretical reviews as well as original results, summarizes the activities of the "New Physics" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 8-26 June, 2009).Comment: 189 page

    Search for CP Violation in the Decay Z -> b (b bar) g

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    About three million hadronic decays of the Z collected by ALEPH in the years 1991-1994 are used to search for anomalous CP violation beyond the Standard Model in the decay Z -> b \bar{b} g. The study is performed by analyzing angular correlations between the two quarks and the gluon in three-jet events and by measuring the differential two-jet rate. No signal of CP violation is found. For the combinations of anomalous CP violating couplings, h^b=h^AbgVb−h^VbgAb{\hat{h}}_b = {\hat{h}}_{Ab}g_{Vb}-{\hat{h}}_{Vb}g_{Ab} and hb∗=h^Vb2+h^Ab2h^{\ast}_b = \sqrt{\hat{h}_{Vb}^{2}+\hat{h}_{Ab}^{2}}, limits of \hat{h}_b < 0.59and and h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st

    Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

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    The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO