Liam Cunningham

A MEMS gravimeter with multi-axis gravitational sensitivity

2022 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL)

A single-axis Microelectromechanical system gravimeter has recently been developed at the Univers... more A single-axis Microelectromechanical system gravimeter has recently been developed at the University of Glasgow. The sensitivity and stability of this device was demonstrated by measuring the Earth tides. The success of this device was enabled in part by its extremely low resonant frequency. This low frequency was achieved with a geometric anti-spring design, fabricated using well-established photolithography and dry etch techniques. Analytical models can be used to calculate the results of these non-linear oscillating systems, but the power of finite element analysis has not been fully utilised to explore the parameter space before now. In this article, the results of previous analytical solutions are replicated using finite element models, before applying the same techniques to optimise the design of the gravimeter. These computer models provide the ability to investigate the effect of the fabrication material of the device: anisotropic <100> crystalline silicon. This is a parameter that is difficult to investigate analytically, but finite element modelling is demonstrated here to provide accurate predictions of real gravimeter behaviour by taking anisotropy into account. The finite element models are then used to demonstrate the design of a three-axis gravimeter enabling the gravity tensor to be measured-a significantly more powerful surveying tool than the original single-axis device.

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Table 8

This paper presents a search for decays of the Higgs boson with a mass of 125 GeV to a pair of ne... more This paper presents a search for decays of the Higgs boson with a mass of 125 GeV to a pair of new spin-0 particles, $H\rightarrow aa$, where one $a$-boson decays to a $b$-quark pair and the other to a muon pair. The search uses 139 fb$^{-1}$ of the LHC proton--proton collision data at a center-of-mass energy of $\sqrt{s}$=13 TeV recorded by the ATLAS experiment between 2015 and 2018. A narrow dimuon resonance is searched for in the invariant mass spectrum between 16 GeV and 62 GeV. The largest excess of events above the Standard Model backgrounds is observed at an invariant dimuon mass of 52 GeV and corresponds to a local (global) significance of $3.3 \sigma$ ($1.7 \sigma$). Upper limits at 95% confidence level are placed on the branching ratio of the Higgs boson to the $bb\mu\mu$ final state, $ \mathcal{B}(H\rightarrow aa\rightarrow bb\mu\mu)$, and are in the range $(0.22-4.0) \times10^{-4}$, depending on the signal mass hypothesis. The events selected for the analysis are require...

Table 1

This paper presents a search for decays of the Higgs boson with a mass of 125 GeV to a pair of ne... more This paper presents a search for decays of the Higgs boson with a mass of 125 GeV to a pair of new spin-0 particles, $H\rightarrow aa$, where one $a$-boson decays to a $b$-quark pair and the other to a muon pair. The search uses 139 fb$^{-1}$ of the LHC proton--proton collision data at a center-of-mass energy of $\sqrt{s}$=13 TeV recorded by the ATLAS experiment between 2015 and 2018. A narrow dimuon resonance is searched for in the invariant mass spectrum between 16 GeV and 62 GeV. The largest excess of events above the Standard Model backgrounds is observed at an invariant dimuon mass of 52 GeV and corresponds to a local (global) significance of $3.3 \sigma$ ($1.7 \sigma$). Upper limits at 95% confidence level are placed on the branching ratio of the Higgs boson to the $bb\mu\mu$ final state, $ \mathcal{B}(H\rightarrow aa\rightarrow bb\mu\mu)$, and are in the range $(0.22-4.0) \times10^{-4}$, depending on the signal mass hypothesis. The events selected for the analysis are require...

Obs limit (+1sig) on (H~, a~) B(N1->Za~) = 100%

Obs limit (+1sig) on (H~, W~), tanb = 10, M2 vs mu

Obs limit (+1sig) on (W~, H~), tanb = 10, M2 vs mu

Obs limit (+1sig) on (W~, H~), tanb = 10, mu>0

Obs limit (+1sig) on (W~, B~) B(N2->ZN1) = 50%

Exp limit (+1sig) on (W~, B~) simplified model (C1N2-WZ)

Obs limit (+1sig) on (W~, B~) simplified model (C1C1-WW)

Obs limit (+1sig) on (H~, B~) B(N2->ZN1) = 50%

$Research paper thumbnail of Search for exotic decays of the Higgs boson into $b\bar{b}$ and missing transverse momentum in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector$

Search for exotic decays of the Higgs boson into $b\bar{b}$ and missing transverse momentum in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

CERN-LHC, ATLAS. A search for the exotic decay of the Higgs boson ($H$) into a $b\bar{b}$ resonan... more CERN-LHC, ATLAS. A search for the exotic decay of the Higgs boson ($H$) into a $b\bar{b}$ resonance plus missing transverse momentum is described. The search is performed with the ATLAS detector at the Large Hadron Collider using $139\; \mathrm{fb}^{-1}$ of $pp$ collisions at $\sqrt{s} = 13$ TeV. The search targets events from $ZH$ production in an NMSSM scenario where $H \rightarrow\tilde{\chi}_{2}^{0}\tilde{\chi}_{1}^{0}$, with $\tilde{\chi}_{2}^{0} \rightarrow a \tilde{\chi}_{1}^{0}$, where $a$ is a light pseudoscalar Higgs boson and $\tilde{\chi}^{0}_{1,2}$ are the two lightest neutralinos. The decay of the $a$ boson into a pair of $b$-quarks results in a peak in the dijet invariant mass distribution. The final-state signature consists of two leptons, two or more jets, at least one of which is identified as originating from a $b$-quark, and missing transverse momentum. Observations are consistent with Standard Model expectations and upper limits are set on the product of cross s...

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Auxiliary figure 2

This paper presents a measurement of the electroweak production of two jets in association with a... more This paper presents a measurement of the electroweak production of two jets in association with a $Z\gamma$ pair, with the $Z$ boson decaying into two neutrinos. It also presents a search for invisible or partially invisible decays of a Higgs boson with a mass of 125 GeV produced through vector-boson fusion with a photon in the final state. These results use data from LHC proton-proton collisions at $\sqrt{s}$ = 13 TeV collected with the ATLAS detector and corresponding to an integrated luminosity of 139 fb$^{-1}$. The event signature, shared by all benchmark processes considered for the measurements and searches, is characterized by a significant amount of unbalanced transverse momentum and a photon in the final state, in addition to a pair of forward jets. Electroweak $Z\gamma$ production in association with two jets is obseved in this final state with a significance of 5.2 (5.1 expected) standard deviations. The measured fiducial cross-section for this process is 1.31 $\pm$ 0.29 ...

Figure 3

This paper presents a measurement of the electroweak production of two jets in association with a... more This paper presents a measurement of the electroweak production of two jets in association with a $Z\gamma$ pair, with the $Z$ boson decaying into two neutrinos. It also presents a search for invisible or partially invisible decays of a Higgs boson with a mass of 125 GeV produced through vector-boson fusion with a photon in the final state. These results use data from LHC proton-proton collisions at $\sqrt{s}$ = 13 TeV collected with the ATLAS detector and corresponding to an integrated luminosity of 139 fb$^{-1}$. The event signature, shared by all benchmark processes considered for the measurements and searches, is characterized by a significant amount of unbalanced transverse momentum and a photon in the final state, in addition to a pair of forward jets. Electroweak $Z\gamma$ production in association with two jets is obseved in this final state with a significance of 5.2 (5.1 expected) standard deviations. The measured fiducial cross-section for this process is 1.31 $\pm$ 0.29 ...

$Research paper thumbnail of Table 76: 2LOS,6j,$\geq$4b CR $H_{T}^{all}$ postfit$

Table 76: 2LOS,6j,$\geq$4b CR $H_{T}^{all}$ postfit

CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with... more CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with single lepton (electron or muon) or an opposite-sign lepton pair, in association with multiple jets in proton-proton collisions at a centre-of-mass energy of 13 TeV with 139 fb^-1 of data. The result is combined with the previous measurement performed by the ATLAS Collaboration in the multilepton final state.

$Research paper thumbnail of Table 66: 1L,8j,$\geq$5b CR $H_{T}^{all}$ postfit$

Table 66: 1L,8j,$\geq$5b CR $H_{T}^{all}$ postfit

CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with... more CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with single lepton (electron or muon) or an opposite-sign lepton pair, in association with multiple jets in proton-proton collisions at a centre-of-mass energy of 13 TeV with 139 fb^-1 of data. The result is combined with the previous measurement performed by the ATLAS Collaboration in the multilepton final state.

$Research paper thumbnail of Table 61: 1L,9j,3bH CR $H_{T}^{all}$ prefit$

Table 61: 1L,9j,3bH CR $H_{T}^{all}$ prefit

CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with... more CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with single lepton (electron or muon) or an opposite-sign lepton pair, in association with multiple jets in proton-proton collisions at a centre-of-mass energy of 13 TeV with 139 fb^-1 of data. The result is combined with the previous measurement performed by the ATLAS Collaboration in the multilepton final state.

$Research paper thumbnail of Table 48: 1L,$\geq$10j,3bV VR BDT score postfit$

Table 48: 1L,$\geq$10j,3bV VR BDT score postfit

CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with... more CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with single lepton (electron or muon) or an opposite-sign lepton pair, in association with multiple jets in proton-proton collisions at a centre-of-mass energy of 13 TeV with 139 fb^-1 of data. The result is combined with the previous measurement performed by the ATLAS Collaboration in the multilepton final state.

$Research paper thumbnail of Table 30: 1L,$\geq$10j,3bH SR BDT score postfit$

Table 30: 1L,$\geq$10j,3bH SR BDT score postfit

CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with... more CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with single lepton (electron or muon) or an opposite-sign lepton pair, in association with multiple jets in proton-proton collisions at a centre-of-mass energy of 13 TeV with 139 fb^-1 of data. The result is combined with the previous measurement performed by the ATLAS Collaboration in the multilepton final state.

$Research paper thumbnail of Table 08: 1L,$\geq$9j,$\geq$3b Sum of b-tag score postfit$

Table 08: 1L,$\geq$9j,$\geq$3b Sum of b-tag score postfit

CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with... more CERN-LHC, ATLAS. Measurements of the of four-top-quark production cross section using events with single lepton (electron or muon) or an opposite-sign lepton pair, in association with multiple jets in proton-proton collisions at a centre-of-mass energy of 13 TeV with 139 fb^-1 of data. The result is combined with the previous measurement performed by the ATLAS Collaboration in the multilepton final state.

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