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

Search for the Flavor-Changing Neutral Current, t->qgamma, in Top Pair Events Using the Atlas Detector

This dissertation presents the search for flavor-changing neutral currents in processes with top pairs where one top decays through the flavor-changing neutral current decay mode (to an up-type quark and a photon) and the other decays through the most common Standard Model mode to a b-quark and a W boson. The W boson then decays leptonically, dening the channels (electron+jets and muon+jets) searched for. This search uses the entire Run-2 dataset of sqrt(s) = 13 TeV data collected using the ATLAS experiment between 2015 and 2018, corresponding to a total integrated luminosity of 139 fb^-1. Observation of the flavor-changing neutral current decays in top quarks would be an unambiguous sign of physics beyond the Standard Model. A neural network was developed to separate signal and background events using both low-level kinematic variables as well as physics-guided high-level variable combinations as inputs. The candidate signal events contain an isolated very high pT photon, a lepton (either an electron or muon), a b-tagged jet, at least one more light jet, and missing transverse energy. Various data-driven techniques were used to estimate contributions to the background from events with a hard scatter photon or a photon faked by either a jet or an electron. As there is no sensitivity for observation of the Standard Model flavor-changing neutral current process, upper limits on the observed (expected) branching ratio and cross section of these processes are set: BR(t -> q gamma) tt -> bWq) < 50(60)fb. This dissertation includes previously unpublished co-authored material

How storytelling can help drive system change...

&lt;blockquote type="cite"&gt;&lt;b&gt;From: &lt;/b&gt;Gabriele Bammer &lt;&lt;a href="mailto:[email protected]"&gt;[email protected]&lt;/a&gt;&gt;&lt;br /&gt; &lt;br /&gt; &lt;b&gt;Subject: &lt;/b&gt;&lt;b&gt;How storytelling can help drive system change&lt;/b&gt;&lt;br /&gt; &lt;br /&gt; &lt;b&gt;Date: &lt;/b&gt;February 6, 2023 at 3:32:24 PM EST&lt;br /&gt; &lt;br /&gt; &lt;b&gt;To: &lt;/b&gt;"&lt;a href="mailto:[email protected]"&gt;[email protected]&lt;/a&gt;" &lt;&lt;a href="mailto:[email protected]"&gt;[email protected]&lt;/a&gt;&gt;&lt;/blockquote&gt; &lt;br /&gt; &lt;br /&gt; &lt;img alt="" height="120" src="https://secure.gravatar.com/avatar/1664c181992a71b874c2f38248bf88a3.jpg?s=120&amp;amp;d=mm&amp;amp;r=g" width="120" /&gt;&lt;br /&gt;  &lt;br /&gt; &lt;a href="https://sciencelistserv.org/hyperkitty/users/5c6bde19ab78479db157b1ef3fecd420/" title="See the profile for Gabriele Bammer"&gt;Gabriele Bammer&lt;/a&gt;&lt;br /&gt;  6 Feb 2023 &lt;br /&gt; 3:32 p.m.&lt;br /&gt; How storytelling can help drive system change is described by Thea Snow, David Murikumthara, Teya Dusseldorp, Rachel Fyfe, Lila Wolff &amp; Jane McCracken in &lt;a href="https://i2insights.org/2023/02/07/storytelling-and-systems-change/" rel="nofollow"&gt;https://i2insights.org/2023/02/07/storytelling-and-systems-change/&lt;/a&gt;. Stories change systems by supporting individuals to change how they see themselves, their communities &amp; their broader context including by building empathy &amp; shifting mindsets. Good stories are authentic, honour the voice of person or community whose story is being told &amp; use language &amp; voice of community; they capture the heart &amp; go deeper than data. Good stories resist bending themselves to fit a pre-existing narrative, instead they challenge the dominant narrative to help dislodge that narrative, thus helping change systems. 6 issues making it hard to tell stories about work involved in systems change: 1) power &amp; trust 2) complexity 3) resources &amp; capability 4) receiver readiness 5) limits of language 6) biases. =================================================== Professor Gabriele Bammer National Centre for Epidemiology and Population Health ANU College of Health and Medicine The Australian National University 62 Mills Road Acton ACT 2601 Australia +61 2 6125 0716 [email protected]&lt;mailto:[email protected]&gt; @GabrieleBammer &lt;a href="http://i2s.anu.edu.au&amp;lt;http://www.anu.edu.au/iisn%3E" rel="nofollow"&gt;http://i2s.anu.edu.au&lt;http: iisn="" www.anu.edu.au=""&gt;&lt;/http:&gt;&lt;/a&gt; &lt;a href="http://i2Insights.org&amp;lt;http://i2insights.org/%3E" rel="nofollow"&gt;http://i2Insights.org&lt;http: i2insights.org=""&gt;&lt;/http:&gt;&lt;/a&gt; TEQSA Provider ID: PRV12002 (Australian University) | CRICOS Provider Code: 00120C ABN: 52 234 063 906 ===================================================&lt;br /&gt; &lt;br /&gt; &lt;a href="https://sciencelistserv.org/hyperkitty/list/[email protected]/thread/P5VOIXOXJ643I4SXUURSHCQA6Y5RC2H7/"&gt;https://sciencelistserv.org/hyperkitty/list/[email protected]/thread/P5VOIXOXJ643I4SXUURSHCQA6Y5RC2H7/&lt;/a&gt;&lt;/mailto:[email protected]&gt;</jats:p

Search for the Flavor-Changing Neutral Current, tt →\rightarrow to qqγ\gamma, in Top Pair Events Using the ATLAS Detector

This dissertation presents the search for flavor-changing neutral currents in processes with top pairs where one top decays through the flavor-changing neutral current decay mode (to an up-type quark and a photon) and the other decays through the most common Standard Model mode to a b-quark and a W boson. The W boson then decays leptonically, defining the channels (electron+jets and muon+jets) searched for. This search uses the entire Run-2 dataset of √s = 13 TeV data collected using the ATLAS experiment between 2015 and 2018, corresponding to a total integrated luminosity of 139 fb$^{−1}$. Observation of the flavor-changing neutral current decays in top quarks would be an unambiguous sign of physics beyond the Standard Model. A neural network was developed to separate signal and background events using both low-level kinematic variables as well as physics-guided high-level variable combinations as inputs. The candidate signal events contain an isolated very high $_{pT}$ photon, a lepton (either an electron or muon), a b-tagged jet, at least one more light jet, and missing transverse energy. Various data-driven techniques were used to estimate contributions to the background from events with a hard scatter photon or a photon faked by either a jet or an electron. As there is no sensitivity for observation of the Standard Model flavor-changing neutral current process, upper limits on the observed (expected) branching ratio and cross section of these processes are set: BR($t$ → $q$$\gamma$)< 9.6 × 10$^{−5}$(11.0 × 10$^{−5}$) and σ($pp$ → $t$$\bar{t}$ → $bWq$$\gamma$) < 50(60)fb. This dissertation includes previously unpublished co-authored material