6,126 research outputs found

    Can the sneutrino be the lightest supersymmetric particle ?

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    Within the framework of the constrained Minimal Supersymmetric extension of the Standard Model we show that recent LEP I limits on the invisible Z width exclude the possibility that the lightest sparticle is the sneutrino

    Study of Pair-Produced Doubly Charged Higgs Bosons with a Four Muon Final State at the CMS Detector

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    An analysis of the discovery potential of pairproduced doubly charged Higgs bosons at the CMS detector is presented in this note. Investigated are doubly charged Higgs bosons pairproduced by the Drell-Yan process. A branching ratio of 100% into muon pairs is assumed. The pure muonic decay channel yields a clear signal which is almost free of background. Doubly charged Higgs bosons with masses in the range 100 to 800 GeV are studied, for a low luminosity scenario of L = 2x10^33cm^-2s^-1. The full detector simulation is used. Doubly charged Higgs bosons in this production and decay channel with mass m(H^pm pm) le 650~GeV are expected to be observable at CMS with a significance exceeding 5 sigma at 1 fb^-1 of integrated luminosity. If no signal will be detected for this integrated luminosity, the existence of a doubly charged Higgs Boson with m((H^pm pm) le 760~GeV can be excluded with 95% Confidence level. This exceeds the current exclusion limit for this channel mH^pm pm) le 136~GeV, set by CDF at Tevatron Run II, by 624~GeV

    Simulation of Cosmic Muons and Comparison with Data from the Cosmic Challenge using Drift Tube Chambers

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    The reconstruction of cosmic muons is important for the commissioning phase and alignment of the Compact Muon Solenoid experiment (CMS), in particular during the early phases of operation with physics collisions. In this context the Magnet Test/Cosmic Challenge (MTCC) with its comprehensive cosmic data taking periods including the presence of the magnetic field has been like a dress rehearsal of detector hardware and software for the upcoming startup of the CMS detector. In addition to data taking also the comparison with simulated events is a crucial part of physics analyses. This study introduces a new cosmic muon generator, CMSCGEN, and it presents its validation by comparing with data from MTCC. As an example results from a reconstruction study using the barrel Muon System are shown, comparing data and Monte Carlo prediction at the level of single chambers up to reconstructed tracks including momentum measurements

    Detection of New Heavy Charged Gauge Bosons in the Muon plus Neutrino Channel

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    This note presents a feasibility study of the search for a new heavy charged gauge boson with the CMS detector at the Large Hadron Collider LHC. The model assumes the existence of a heavy carbon copy of the Standard Model W (Reference Model by Altarelli) generically denoted as Wprime. Such a boson has been investigated in the decay channel Wprime --> \mu \nu using the full detector simulation including minimum bias events (pile-up) according to the expected first years of luminosity. All relevant Standard Model backgrounds have been considered. Such a new boson is expected to be discovered, if existant, with a mass of 0.1-4.6 TeV for an integrated luminosity of 10 fb^-1. The range can be expanded to 6.1 TeV with an integrated luminosity of 300 fb^-1. If no signs for a Wprime boson appear 95% CL exclusion limits of 4.7 TeV and 6.2 TeV can be set respectively

    Entfernungsbestimmung mit der Cepheiden-Methode am Beispiel des Sternhaufens M5

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    Die Messung der Entfernungen zu Planeten, Sternen und Galaxien ist gleichzeitig fundamental und schwierig. Im Bereich von einigen Hundert bis zu vielen Tausend Lichtjahren hat sich in den letzten Jahrzehnten die Cepheiden-Methode etabliert. Diese nutzt aus, dass es für eine bestimmte Klasse von veränderlichen Sternen, den Cepheiden, einen Zusammenhang zwischen der relativ leicht messbaren Periode der Helligkeitsschwankungen und der absoluten Helligkeit gibt. Misst man die Periode und gleichzeitig auch die scheinbare Helligkeit des Sterns, so kann man sofort den Abstand zur Erde ausrechnen. Die Entfernung des Kugelsternhaufens M5 kann man anhand des veränderlichen Sterns V42 mit einem kleineren Teleskop und einfacher Datenauswertung auf etwa 10% genau bestimmen. Diese Distanzmessung eignet sich gut für ein schulisches oder universitäres Astronomieprojekt.

    Entfernungsbestimmung mit der Cepheiden-Methode am Beispiel des Sternhaufens M5

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    Die Messung der Entfernungen zu Planeten, Sternen und Galaxien ist gleichzeitig fundamental und schwierig. Im Bereich von einigen Hundert bis zu vielen Tausend Lichtjahren hat sich in den letzten Jahrzehnten die Cepheiden-Methode etabliert. Diese nutzt aus, dass es für eine bestimmte Klasse von veränderlichen Sternen, den Cepheiden, einen Zusammenhang zwischen der relativ leicht messbaren Periode der Helligkeitsschwankungen und der absoluten Helligkeit gibt. Misst man die Periode und gleichzeitig auch die scheinbare Helligkeit des Sterns, so kann man sofort den Abstand zur Erde ausrechnen. Die Entfernung des Kugelsternhaufens M5 kann man anhand des veränderlichen Sterns V42 mit einem kleineren Teleskop und einfacher Datenauswertung auf etwa 10% genau bestimmen. Diese Distanzmessung eignet sich gut für ein schulisches oder universitäres Astronomieprojekt.

    Model Unspecific Search in CMS

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    We present the results of a model independent analysis, which systematically scans the data taken by CMS for deviations from the Standard Model predictions. Due to the minimal theoretical bias this approach is sensitive to a variety of models for new physics. Events with at least one electron or muon are classified according to their content of reconstructed objects (muons, electrons, photons, jets and missing transverse energy). A broad scan of three kinematic distributions in those classes is performed by identifying deviations from Standard Model expectations, accounting for systematic uncertainties.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011), Paris, France, November 14-18 2011, 2 pages, 3 figur

    A phenomenological model of the muon density profile on the ground of very inclined air showers

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    Ultra-high energy cosmic rays generate extensive air showers in Earth's atmosphere. A standard approach to reconstruct the energy of an ultra-high energy cosmic rays is to sample the lateral profile of the particle density on the ground of the air shower with an array of surface detectors. For cosmic rays with large inclinations, this reconstruction is based on a model of the lateral profile of the muon density observed on the ground, which is fitted to the observed muon densities in individual surface detectors. The best models for this task are derived from detailed Monte-Carlo simulations of the air shower development. We present a phenomenological parametrization scheme which allows to derive a model of the average lateral profile of the muon density directly from a fit to a set of individual Monte-Carlo simulated air showers. The model reproduces the detailed simulations with a high precision. As an example, we generate a muon density model which is valid in the energy range 1e18 eV < E < 1e20 eV and the zenith angle range 60 deg < theta < 90 deg. We will further demonstrate a way to speed up the simulation of such muon profiles by three orders of magnitude, if only the muons in the shower are of interest.Comment: Corresponding author: Hans Dembinsk
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