Search for heavy charged long-lived particles in the ATLAS detector in 36.1  fb−1 of proton-proton collision data at

Abstract

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)

Probing multicomponent FIMP scenarios with gamma-ray telescopes

“…For the latter, we require m 1 40 eV to ensure that ψ 1 is always out of thermal equilibrium. In our analysis, we have fixed for concreteness m Σ = 430 GeV, which saturates the current lower limit on the mass of long-lived charged scalar particles, assuming Drell-Yan production [26]. We show as dark gray shaded regions the values of the inverse width excluded by the non-observation of a line in the isotropic gamma-ray flux measured by INTEGRAL [27], COMPTEL [28], EGRET [29] and the Fermi-LAT [30], as calculated in [31] (left) as well as a dedicated line-search by Fermi-LAT [32] (right).…”

Vector-like quarks with non-renormalizable interactions

“…In table 6, we give the values of 1/y above which i) non-perturbative QCD is important (Λ QCD ), ii) displaced vertices can be observed (Λ disp ) and iii) the heavy quark is stable within detector distances (Λ long lived ). As a reference, ATLAS has recently put bounds on the mass of long-lived supersymmetric R-hadrons, using ionization energy loss and time-of-flight information [42]. This search is quite model-independent and can be adapted to the case of vector-like quarks (which are also color-triplets but fermions, rather than scalars).…”

Hypercharged naturalness

“…Searches at the LHC for such type of particles have been carried out at √ s = 13 TeV, the latest analysis from ATLAS with 36.1 fb −1 of data [43]. In Fig.…”