Study of the material of the ATLAS inner detector for Run 2 of the LHC

Abstract

JINST 12 P120098 Results and discussion 33 8.1 Transverse impact parameter resolution 33 Conclusion 39The ATLAS collaboration 43 JINST 12 P12009energy larger than 4 GeV, and the Bertini-style cascade for hadrons below 5 GeV [25]. In the energy region where these two models overlap, one model is randomly selected to simulate a given interaction, with a probability weight which changes linearly as a function of kinetic energy. Simulated descriptions of the inner detectorSimulated pp collision events generated by P 8 and E were processed through the ATLAS detector simulation [26], based on G 4, and are reconstructed by the same software as used to process the data. The ATLAS detector is described within G 4 by a collection of geometry models, each describing the sub-detectors that constitute the full detector. The geometry model for the inner detector describes both the active elements of the detectors (e.g. the silicon pixel sensors) and the passive material (e.g. support structures and cables). The measurements presented in this paper make use of several alternative ID geometry models, summarised below:Original -This ID geometry model represents the nominal geometry model used to generate MC simulation samples produced in 2015. The studies presented in this paper identified a number of missing components in the simulated description of the IBL.Updated -A modified version of the original geometry model which was created for this study. In this model, several additional components are added to the simulated description of the IBL reflecting the observations which are described in section 6. These additional components include flex buses and a number of surface-mounted devices on the front-end of the modules. Small modifications to the positioning of each IBL stave and the material densities of the IBL support structures were also made.

Showcasing HH production: Benchmarks for the LHC and HL-LHC

“…[125] and we rescale these results taking into account the cross section differences between 13 TeV and 8 TeV using the results provided by the Higgs cross section working group [126]. For h → bb we consider extrapolations based on V h production [127], tth production [128] as well as weak boson fusion [129]. h → τ τ is based on [130], which agrees with the ECFA results of [29] upon projecting to 3 ab −1 .…”

Production and Hadronic Decays of Higgs Bosons in Heavy-Ion Collisions

“…We expect the sensitivity can be further improved for example by using multi-variate analysis and by including Z decays into neutrinos and W H production as demonstrated in Ref. [22]. Taken together they may bring down the needed luminosity by a factor of two.…”

“…For comparison, cross sections for production in pp collisions are also listed in Table I. We focus on decays of the Higgs boson to bottom quarks for which the associated production with a Z boson and its subsequent leptonic decay gives the strongest sensitivity [22,23], albeit with a relatively small cross section. The dominant backgrounds in this case are Z plus bottom-quark pair production and top-quark pair production with leptonic decays.…”

“…The analysis so far follows Ref. [22]. As mentioned earlier, different quenching properties of the signal and backgrounds lead to further separation in certain variables.…”

Higgs and Z assisted stop searches at hadron colliders

“…Among various new physics beyond the Standard Model, Supersymmetry There are many ongoing searches for the stops by the ATLAS and CMS groups [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and most of the searches focus on the following decay modes:t 1 → tχ 0 1 andt 1 → bχ ± 1 → bW χ 0 1 , assuming a 100% decay branching fraction into those two channels. The current experimental search limits from those two channels exclude the stop mass up to 1120 GeV for a very light Lightest Supersymmetric Particle (LSP) χ 0 1 [4][5][6][7][8][9][10][11][12][13]. In cases where the mass spliting between the stops and the LSP is very small, the stop mass up to about 580 GeV is excluded [4,[14][15][16][17] for decay channels oft 1 → cχ 0 1 andt 1 → bf f ′ χ 0 1 .…”