This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2:0 fb À1 of pp collisions recorded at a center-of-mass energy of ffiffi ffi s p ¼ 7 TeV. No event is found in the signal region, leading to an upper limit on the production cross section at 95% confidence level of 1:6= fb for Dirac magnetic monopoles with the minimum unit magnetic charge and with mass between 200 GeV and 1500 GeV, where is the monopole reconstruction efficiency. The efficiency is high and uniform in the fiducial region given by pseudorapidity j j < 1:37 and transverse kinetic energy 600-700 < E kin sin < 1400 GeV. The minimum value of 700 GeV is for monopoles of mass 200 GeV, whereas the minimum value of 600 GeV is applicable for higher mass monopoles. Therefore, the upper limit on the production cross section at 95% confidence level is 2 fb in this fiducial region. Assuming the kinematic distributions from Drell-Yan pair production of spin-1=2 Dirac magnetic monopoles, the efficiency is in the range 1%-10%, leading to an upper limit on the cross section at 95% confidence level that varies from 145 fb to 16 fb for monopoles with mass between 200 GeV and 1200 GeV. This limit is weaker than the fiducial limit because most of these monopoles lie outside the fiducial region.
Search for heavy charged long-lived particles in the ATLAS detector in 36.1 fb −1 of proton-proton collision data at √ s = 13 TeVThe ATLAS Collaboration A search for heavy charged long-lived particles is performed using a data sample of 36.1 fb −1 of proton-proton collisions at √ s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. The search is based on observables related to ionization energy loss and time of flight, which are sensitive to the velocity of heavy charged particles traveling significantly slower than the speed of light. Multiple search strategies for a wide range of lifetimes, corresponding to path lengths of a few meters, are defined as model-independently as possible, by referencing several representative physics cases that yield long-lived particles within supersymmetric models, such as gluinos/squarks (R-hadrons), charginos and staus. No significant deviations from the expected Standard Model background are observed. Upper limits at 95% confidence level are provided on the production cross sections of long-lived R-hadrons as well as directly pair-produced staus and charginos. These results translate into lower limits on the masses of long-lived gluino, sbottom and stop R-hadrons, as well as staus and charginos of 1 ATLAS uses a right-handed coordinate system with its origin at the nominal interaction point (IP) in the center of the detector and the z-axis coinciding with the axis of the beam pipe. The x-axis points from the IP to the center of the LHC ring, and the y-axis points upward. Cylindrical coordinates (r, φ) are used in the transverse plane, φ being the azimuthal angle around the beam pipe. The pseudorapidity is defined in terms of the polar angle θ as η = − ln tan(θ/2). Object distances in the η-φ plane are given by ∆R = (∆η) 2 + (∆φ)
A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy ffiffi ffi s p ¼ 7 TeV is presented. The measurement covers the pseudorapidity ranges j j < 1:37 and 1:52 j j < 1:81 in the transverse energy range 15 E T < 100 GeV. The results are based on an integrated luminosity of 880 nb À1 , collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed distribution of the transverse isolation energy in a narrow cone around the photon candidate. The results are compared to predictions from next-to-leading-order perturbative QCD calculations.
Searches for heavy long-lived charged particles are performed using a data sample of 19.1 fb −1 from proton-proton collisions at a centre-of-mass energy of √ s = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. No excess is observed above the estimated background and limits are placed on the mass of long-lived particles in various supersymmetric models. Long-lived tau sleptons in models with gauge-mediated symmetry breaking are excluded up to masses between 440 and 385 GeV for tan β between 10 and 50, with a 290 GeV limit in the case where only direct tau slepton production is considered. In the context of simplified LeptoSUSY models, where sleptons are stable and have a mass of 300 GeV, squark and gluino masses are excluded up to a mass of 1500 and 1360 GeV, respectively. Directly produced charginos, in simplified models where they are nearly degenerate to the lightest neutralino, are excluded up to a mass of 620 GeV. R-hadrons, composites containing a gluino, bottom squark or top squark, are excluded up to a mass of 1270, 845 and 900 GeV, respectively, using the full detector; and up to a mass of 1260, 835 and 870 GeV using an approach disregarding information from the muon spectrometer.
Measurements are presented of the properties of high transverse momentum jets, produced in protonproton collisions at a center-of-mass energy of ffiffi ffi s p ¼ 7 TeV. The data correspond to an integrated luminosity of 35 pb À1 and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-k t algorithm with distance parameters R ¼ 0:6 and 1.0, with transverse momentum p T > 300 GeV and pseudorapidity jj < 2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions.
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