1,808 research outputs found

    Supersymmetry searches with ATLAS detector at LHC

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    In this paper a brief overview of the principal strategies for Supersymmetry searches with ATLAS detector at LHC is presented. The aim is to evaluate the ATLAS discovery potential within mSUGRA parameter space of Supersymmetry, both in inclusive and exclusive channels, and to estimate the achievable precision in SUSY parameters in relation to the integrated luminosity available at LHC

    Perspectives for the detection and measurement of Supersymmetry in the focus point region of mSUGRA models with the ATLAS detector at LHC

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    This paper discusses the ATLAS potential to study Supersymmetry for the "Focus-Point" region of the parameter space of mSUGRA models. The potential to discovery a deviation from Standard Model expectations with the first few fb1{fb}^{-1} of LHC data was studied using the parametrized simulation of the ATLAS detector. Several signatures were considered, involving hard jets, large missing energy, and either bb-tagged jets, opposite-sign isolated electron or muon pairs, or top quarks reconstructed exploiting their fully hadronic decays. With only 1 fb1{fb}^{-1} of data each of these signatures may allow to observe an excess of events over Standard Model expectation with a statistical significance exceeding 5 standard deviations. An analytical expression was derived for the shape of the distribution of the dilepton invariant mass arising from the three-body leptonic decay of the neutralinos under the hypothesis of heavy scalars, which is appropriate for the focus-point scenario. The resulting function was used to fit the distribution of the dilepton invariant mass obtained with simulated LHC data, and to extract the value of two kinematic endpoints measuring the χ~20χ~10\tilde \chi^0_2 - \tilde \chi^0_1 and the χ~30χ~10\tilde \chi^0_3 - \tilde \chi^0_1 mass differences. This information was used to constrain the MSSM parameter space compatible with the data

    Does the `Higgs' have Spin Zero?

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    The Higgs boson is predicted to have spin zero. The ATLAS and CMS experiments have recently reported of an excess of events with mass ~ 125 GeV that has some of the characteristics expected for a Higgs boson. We address the questions whether there is already any evidence that this excess has spin zero, and how this possibility could be confirmed in the near future. The excess observed in the gamma gamma final state could not have spin one, leaving zero and two as open possibilities. We calculate the angular distribution of gamma gamma pairs from the decays of a spin-two boson produced in gluon-gluon collisions, showing that is unique and distinct from the spin-zero case. We also calculate the distributions for lepton pairs that would be produced in the W W* decays of a spin-two boson, which are very different from those in Higgs decays, and note that the kinematics of the event selection used to produce the excess observed in the W W* final state have reduced efficiency for spin two.Comment: 22 pages, 22 figures, Version accepted for publication in JHEP, includes additional plots of dilepton mass distribution

    A Fast Track towards the `Higgs' Spin and Parity

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    The LHC experiments ATLAS and CMS have discovered a new boson that resembles the long-sought Higgs boson: it cannot have spin one, and has couplings to other particles that increase with their masses, but the spin and parity remain to be determined. We show here that the `Higgs' + gauge boson invariant-mass distribution in `Higgs'-strahlung events at the Tevatron or the LHC would be very different under the J^P = 0+, 0- and 2+ hypotheses, and could provide a fast-track indicator of the `Higgs' spin and parity. Our analysis is based on simulations of the experimental event selections and cuts using PYTHIA and Delphes, and incorporates statistical samples of `toy' experiments.Comment: 18 pages, 9 pdf figure

    Visible Color and Photometry of Bright Materials on Vesta

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    The Dawn Framing Camera (FC) collected images of the surface of Vesta at a pixel scale of ~70 m in the High Altitude Mapping Orbit (HAMO) phase through its clear and seven color filters spanning from 430 nm to 980 nm. The surface of Vesta displays a large diversity in its brightness and colors, evidently related to the diverse geology [1] and mineralogy [2]. Here we report a detailed investigation of the visible colors and photometric properties of the apparently bright materials on Vesta in order to study their origin. The global distribution and the spectroscopy of bright materials are discussed in companion papers [3, 4], and the synthesis results about the origin of Vestan bright materials are reported in [5]