170 research outputs found

    Rare t-quark decays tclj+lkt \to c l_j^{+} l_k^{-}, tcνj~νkt \to c \tilde{\nu_j} \nu_k in the minimal four color symmetry model

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    The rare t-quark decays tclj+lkt \to c l_j^{+} l_k^{-}, tcνj~νkt \to c \tilde{\nu_j} \nu_k via the scalar leptoquark doublets are investigated in the minimal four color symmetry model with the Higgs mechanism of the quark-lepton mass splitting. The partial widths of these decays are calculated and the total width of the charged lepton mode Γ(tcl+l)=j,kΓ(tclj+lk) \Gamma(t \to c {l^{+}}' l^{-})= \sum_{j,k} \Gamma(t \to c l_{j}^{+} l_{k}^{-}) and the total width of the neutrino mode Γ(tcν~ν)=j,kΓ(tcνj~νk) \Gamma(t \to c \tilde{\nu}' \nu)= \sum_{j,k} \Gamma(t \to c \tilde{\nu_{j}} \nu_{k}) are found. The corresponding branching ratios are shown to be Br(tcl+l)(3.50.4)105, Br(t \to c {l^{+}}' l^{-}) \approx (3.5 - 0.4) 10^{-5}, Br(tcν~ν)(7.10.8)105 Br(t \to c {\tilde{\nu}}' \nu) \approx (7.1 - 0.8) 10^{-5} for the scalar leptoquark masses mS=180250GeV m_{S}= 180 - 250 GeV and for the appropriate values (sinβ0.2) (\sin{\beta} \approx 0.2) of the mixing angle of the model. The search for such decays at LHC may be of interest.Comment: 18 pages, 2 figures, 1 table, to be published in Modern Physics Letters A; corrected typo

    Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

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    A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN

    Performance of the CMS Cathode Strip Chambers with Cosmic Rays

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    The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns

    Development of Cheaper Embryo Vitrification Device Using the Minimum Volume Method

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    [EN] This study was designed to compare the efficiency of the Cryotop and Calibrated plastic inoculation loop (CPIL) devices for vitrification of rabbit embryos on in vitro development and implantation rate, offspring rate at birth and embryonic and fetal losses. CPIL is a simple tool used mainly by microbiologists to retrieve an inoculum from a culture of microorganisms. In experiment 1, embryos were vitrified using a Cryotop device and a CPIL device. There were no significant differences in hatched/hatching blastocyst stage rates after 48 h of culture among the vitrified groups (62±4.7% and 62±4.9%, respectively); however, the rates were significantly lower (P<0.05) than those of the fresh group (95±3.4%). In experiment 2, vitrified embryos were transferred using laparoscopic technique. The number of implanted embryos was estimated by laparoscopy as number of implantation sites at day 14 of gestation. At birth, total offspring were recorded. Embryonic and fetal losses were calculated as the difference between implanted embryos and embryos transferred and total born at birth and implanted embryos, respectively. The rate of implantation and development to term was similar between both vitrification devices (56±7.2% and 50±6.8% for implantation rate and 40±7.1% and 35±6.5% for offspring rate at birth); but significantly lower than in the fresh group (78±6.6% for implantation rate and 70±7.2% for offspring rate at birth, P<0.05). Likewise, embryonic losses were similar between both vitrification devices (44±7.2% and 50±6.8%), but significantly higher than in the fresh group (23±6.6%, P < 0.05). However, fetal losses were similar between groups (10±4.4%, 15±4.8% and 8±4.2%, for vitrified, Cryotop or CPIL and fresh, respectively). These results indicate that the CPIL device is as effective as the Cryotop device for vitrification of rabbit embryos, but at a cost of 0.05 per device.This research was supported by the projects Spanish Research project AGL2014-53405-C2-1-P Comision Interministerial de Ciencia y Tecnologia (FMJ, JSV) and Generalitat Valenciana research program (Prometeo II 2014/036, JSV, FMJ).Marco Jiménez, F.; Jiménez Trigos, ME.; Almela-Miralles, V.; Vicente Antón, JS. (2016). Development of Cheaper Embryo Vitrification Device Using the Minimum Volume Method. PLoS ONE. 11(2):1-9. https://doi.org/10.1371/journal.pone.0148661S1911

    Performance and Operation of the CMS Electromagnetic Calorimeter

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    The operation and general performance of the CMS electromagnetic calorimeter using cosmic-ray muons are described. These muons were recorded after the closure of the CMS detector in late 2008. The calorimeter is made of lead tungstate crystals and the overall status of the 75848 channels corresponding to the barrel and endcap detectors is reported. The stability of crucial operational parameters, such as high voltage, temperature and electronic noise, is summarised and the performance of the light monitoring system is presented

    The CARMENES search for exoplanets around M dwarfs High-resolution optical and near-infrared spectroscopy of 324 survey stars

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    The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520–1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700–900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s−1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3–4 m s−1

    Gliese 49: activity evolution and detection of a super-Earth A HADES and CARMENES collaboration

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    Small planets around low-mass stars often show orbital periods in a range that corresponds to the temperate zones of their host stars which are therefore of prime interest for planet searches. Surface phenomena such as spots and faculae create periodic signals in radial velocities and in observational activity tracers in the same range, so they can mimic or hide true planetary signals. We aim to detect Doppler signals corresponding to planetary companions, determine their most probable orbital configurations, and understand the stellar activity and its impact on different datasets. We analyze 22 years of data of the M1.5V-type star Gl49 (BD+61 195) including HARPS-N and CARMENES spectrographs, complemented by APT2 and SNO photometry. Activity indices are calculated from the observed spectra, and all datasets are analyzed with periodograms and noise models. We investigate how the variation of stellar activity imprints on our datasets. We further test the origin of the signals and investigate phase shifts between the different sets. To search for the best-fit model we maximize the likelihood function in a Markov Chain Monte Carlo approach. As a result of this study, we are able to detect the super-Earth Gl49b with a minimum mass of 5.6 Ms. It orbits its host star with a period of 13.85d at a semi-major axis of 0.090 au and we calculate an equilibrium temperature of 350 K and a transit probability of 2.0%. The contribution from the spot-dominated host star to the different datasets is complex, and includes signals from the stellar rotation at 18.86d, evolutionary time-scales of activity phenomena at 40-80d, and a long-term variation of at least four years

    Calibration of the CMS Drift Tube Chambers and Measurement of the Drift Velocity with Cosmic Rays

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    CMS physics technical design report : Addendum on high density QCD with heavy ions

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