Modelling radiation damage to pixel sensors in the ATLAS detector

Abstract

The ATLAS Collaboration Silicon pixel detectors are at the core of the current and planned upgrade of the ATLAS experiment at the LHC. Given their close proximity to the interaction point, these detectors will be exposed to an unprecedented amount of radiation over their lifetime. The current pixel detector will receive damage from non-ionizing radiation in excess of 10 15 1 MeV n eq /cm 2 , while the pixel detector designed for the high-luminosity LHC must cope with an order of magnitude larger fluence. This paper presents a digitization model incorporating effects of radiation damage to the pixel sensors. The model is described in detail and predictions for the charge collection efficiency and Lorentz angle are compared with collision data collected between 2015 and 2017 (≤ 10 15 1 MeV n eq /cm 2 ).

Measuring relic abundance of minimal dark matter at hadron colliders

“…At the HL-LHC the DM needs to be very light as follows: D1: m χ0 415 GeV, F 7.3%, D2: m χ0 633 GeV, F 5.1%, D3: m χ0 813 GeV, F 3.4%, M1: m χ0 315 GeV, F 2.1%, M2: m χ0 546 GeV, F 1.9%, M3: m χ0 714 GeV, F 1.3%. Note that the parameter space of the D1 model is ruled out by the ATLAS result obtained in the disappearingtrack signature [80]. If we do observe an excess in the mono-jet channel at the HL-LHC, then we reach the conclusion that none of the six MDM models considered in this work can explain the observed relic abundance and extra DM candidates are needed [83].…”

“…Note that the current 13 TeV LHC searches impose a lower bound of 460 GeV for the DM candidate in the D1 model at the 95% C.L. [80] based on the disappearing-track signature and an integrated luminosity of 36.1 fb −1 . The bound is slightly weaker than our result m χ0 544 GeV (assuming an integrated luminosity of 3 ab −1 ).…”

Right-handed neutrino dark matter with radiative neutrino mass in gauged B − L model

“…The corresponding decay length as a function of η ± mass is shown in the left panel plot of figure 13. The right panel plot of figure 13 shows a comparison of the decay length in our model with the ATLAS bound [97]. In figure 14, we show the comparison between the leptonic decay mode and pionic decay mode for different benchmark values of Yukawa couplings.…”

“…Since all the SM fermions are charged under this gauge symmetry, the production of Z B−L gauge boson in proton proton collisions can be significant [54,55,82] Here we have kept fixed the mass splittings as M η 0R − M N 1 =1 GeV and For recent searches of displaced vertex type signatures at the LHC, one may refer to [96,97]. mixing case, please see [98] and [99].…”

“…Such tiny decay width keeps the lifetime of η ± 1 considerably long enough that it can reach the detector before decaying. In fact, the ATLAS experiment at the LHC has already searched for such long-lived charged particles with lifetime ranging from 10 ps to 10 ns, with maximum sensitivity around 1 ns [97]. In the decay η ± → η 0 π ± , the final state pion typically has very low momentum and it is not reconstructed in the detector.…”