Deflection Monitoring Method Using Fiber Bragg Gratings Applied to Tracking Particle Detectors

This paper proposes the use of fiber Bragg gratings (FBGs) for the deflection monitoring of a micromegas (MM) tracking particle detector to be installed at the European Organization for Nuclear Research during a major upgrade of the experiment ATLAS within 2018. MM detectors are designed to reach high spatial and time resolution, even if the design is not yet finalized. One mandatory issue for the MM detector is a precise monitoring of the deflection of the drift and read-out electrodes and/or of the panel hosting the electrodes. To this aim, FBG strain sensors are proposed and experimentally investigated as a sensing solution to monitor the strain state of the detector support panel hosting the drift and read-out electrodes. Finally, simple postprocessing analysis based on classical beam theory considering a rigid body permits calculating the panel deflection. Preliminary experimental results on first prototypes of small and large detector panels are presented and discussed

Study of ordered hadron chains with the ATLAS detector

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A search for resonances decaying into a Higgs boson and a new particle X in the XH→qqbb final state with the ATLAS detector

A search for heavy resonances decaying into a Higgs boson ($H$) and a new particle ($X$) is reported, utilizing 36.1 fb$^{-1}$ of proton-proton collision data at $\sqrt{s} =$ 13 TeV collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. The particle $X$ is assumed to decay to a pair of light quarks, and the fully hadronic final state $XH \rightarrow q\bar q'b\bar b$ is analysed. The search considers the regime of high $XH$ resonance masses, where the $X$ and $H$ bosons are both highly Lorentz-boosted and are each reconstructed using a single jet with large radius parameter. A two-dimensional phase space of $XH$ mass versus $X$ mass is scanned for evidence of a signal, over a range of $XH$ resonance mass values between 1 TeV and 4 TeV, and for $X$ particles with masses from 50 GeV to 1000 GeV. All search results are consistent with the expectations for the background due to Standard Model processes, and 95% CL upper limits are set, as a function of $XH$ and $X$ masses, on the production cross-section of the $XH\rightarrow q\bar q'b\bar b$ resonance

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

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

Instituto de Física La Plat

Standard Model Constraints On

The results reported in this paper are based on data collected during four years of running at LEP, from '90 to '94. A combined set of published and preliminary electroweak results from the four LEP experiments is used to constraint the masses of the top quark and Standard Higgs boson. The fit yelds M Top = 179 \Sigma 9 +17 \Gamma19 GeV (60 ! MH ! 1000 GeV ) in excellent agreement with the recent determination from CDF and D0 at Tevatron. Using also their direct measurement of M Top in the fit we get an upper limit for MHiggs : MHiggs ! 900 GeV at 95% C:L:. XXX th Rencontres de Moriond, QCD and High Energy Hadronic Interactions, Les Arcs,France March 19-26, 1995. 1 Introduction During the last year important progresses have been achieved for both statistical and systematic errors on the electroweak measurements. The statistics was approximately doubled reaching a total amount of data of about ten millions of hadrons and one million of leptons. The calibration of the LEP energy..