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1. Search for long-lived, massive particles in events with displaced vertices and multiple jets in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

   https://doi.org/10.1007/JHEP06(2023)200  

   Aad, G; Abbott, B; Abbott, D C; Abeling, K; Abidi, S H; Aboulhorma, A; Abramowicz, H; Abreu, H; Abulaiti, Y; Abusleme_Hoffman, A C; et al (June 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> A search for long-lived particles decaying into hadrons is presented. The analysis uses 139 fb⁻¹ofppcollision data collected at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV by the ATLAS detector at the LHC using events that contain multiple energetic jets and a displaced vertex. The search employs dedicated reconstruction techniques that significantly increase the sensitivity to long-lived particles decaying in the ATLAS inner detector. Background estimates for Standard Model processes and instrumental effects are extracted from data. The observed event yields are compatible with those expected from background processes. The results are used to set limits at 95% confidence level on model-independent cross sections for processes beyond the Standard Model, and on scenarios with pair-production of supersymmetric particles with long-lived electroweakinos that decay via a smallR-parity-violating coupling. The pair-production of electroweakinos with masses below 1.5 TeV is excluded for mean proper lifetimes in the range from 0.03 ns to 1 ns. When produced in the decay of$$ m\left(\overset{\sim }{g}\right) $$ $m\left(\tilde{g}\right)$= 2.4 TeV gluinos, electroweakinos with$$ m\left({\overset{\sim }{\chi}}_1^0\right) $$ $m\left({\tilde{\chi }}_1^0\right)$= 1.5 TeV are excluded with lifetimes in the range of 0.02 ns to 4 ns. 

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2. Probing bottom-associated production of a TeV scale scalar decaying to a top quark and dark matter at the LHC

   https://doi.org/10.1007/JHEP09(2024)203  

   Kalsi, Amandeep Kaur; Kamon, Teruki; Kim, Seulgi; Lee, Jason_S H; Rathjens, Denis; Roh, Youn Jung; Thompson, Adrian; Watson, Ian James (September 2024, Journal of High Energy Physics)

   JHEP (Ed.)

   A<sc>bstract</sc> A minimal non-thermal dark matter model that can explain both the existence of dark matter and the baryon asymmetry in the universe is studied. It requires two color-triplet, iso-singlet scalars with$$ \mathcal{O}\left(\textrm{TeV}\right) $$ $O\left(\mathrm{TeV}\right)$masses and a singlet Majorana fermion with a mass of$$ \mathcal{O}\left(\textrm{GeV}\right) $$ $O\left(\mathrm{GeV}\right)$. The fermion becomes stable and can play the role of the dark matter candidate. We consider the fermion to interact with a top quark via the exchange of QCD-charged scalar fields coupled dominantly to third generation fermions. The signature of a single top quark production associated with a bottom quark and large missing transverse momentum opens up the possibility to search for this type of model at the LHC in a way complementary to existing monotop searches. 

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3. Searches for additional Higgs bosons and for vector leptoquarks in ττ final states in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP07(2023)073  

   Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Escalante Del Valle, A.; Hussain, P. S.; Jeitler, M.; et al (July 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> Three searches are presented for signatures of physics beyond the standard model (SM) inττfinal states in proton-proton collisions at the LHC, using a data sample collected with the CMS detector at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV, corresponding to an integrated luminosity of 138 fb⁻¹. Upper limits at 95% confidence level (CL) are set on the products of the branching fraction for the decay intoτleptons and the cross sections for the production of a new bosonϕ, in addition to the H(125) boson, via gluon fusion (ggϕ) or in association with b quarks, ranging from$$ \mathcal{O} $$ $O$(10 pb) for a mass of 60 GeV to 0.3 fb for a mass of 3.5 TeV each. The data reveal two excesses for ggϕproduction with localp-values equivalent to about three standard deviations atm_ϕ= 0.1 and 1.2 TeV. In a search fort-channel exchange of a vector leptoquark U₁, 95% CL upper limits are set on the dimensionless U₁leptoquark coupling to quarks andτleptons ranging from 1 for a mass of 1 TeV to 6 for a mass of 5 TeV, depending on the scenario. In the interpretations of the$$ {M}_{\textrm{h}}^{125} $$ $M_h^{125}$and$$ {M}_{\textrm{h},\textrm{EFT}}^{125} $$ $M_{h,\mathrm{EFT}}^{125}$minimal supersymmetric SM benchmark scenarios, additional Higgs bosons with masses below 350 GeV are excluded at 95% CL. 

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4. On the sensitivity reach of $$\textrm{LQ}$$ production with preferential couplings to third generation fermions at the LHC

   https://doi.org/10.1140/epjc/s10052-023-12177-4  

   Flórez, A.; Jones-Pérez, J.; Gurrola, A.; Rodriguez, C.; Peñuela-Parra, J. (November 2023, The European Physical Journal C)

   Abstract Leptoquarks ($$\textrm{LQ}$$ $\text{LQ}$s) are hypothetical particles that appear in various extensions of the Standard Model (SM), that can explain observed differences between SM theory predictions and experimental results. The production of these particles has been widely studied at various experiments, most recently at the Large Hadron Collider (LHC), and stringent bounds have been placed on their masses and couplings, assuming the simplest beyond-SM (BSM) hypotheses. However, the limits are significantly weaker for$$\textrm{LQ}$$ $\text{LQ}$models with family non-universal couplings containing enhanced couplings to third-generation fermions. We present a new study on the production of a$$\textrm{LQ}$$ $\text{LQ}$at the LHC, with preferential couplings to third-generation fermions, considering proton-proton collisions at$$\sqrt{s} = 13 \, \textrm{TeV}$$ $\sqrt{s}=13\text{TeV}$and$$\sqrt{s} = 13.6 \, \textrm{TeV}$$ $\sqrt{s}=13.6\text{TeV}$. Such a hypothesis is well motivated theoretically and it can explain the recent anomalies in the precision measurements of$$\textrm{B}$$ $\text{B}$-meson decay rates, specifically the$$R_{D^{(*)}}$$ $R_{D^{(\ast )}}$ratios. Under a simplified model where the$$\textrm{LQ}$$ $\text{LQ}$masses and couplings are free parameters, we focus on cases where the$$\textrm{LQ}$$ $\text{LQ}$decays to a$$\tau $$ $\tau$lepton and a$$\textrm{b}$$ $\text{b}$quark, and study how the results are affected by different assumptions about chiral currents and interference effects with other BSM processes with the same final states, such as diagrams with a heavy vector boson,$$\textrm{Z}^{\prime }$$ ${\text{Z}}^{\prime }$. The analysis is performed using machine learning techniques, resulting in an increased discovery reach at the LHC, allowing us to probe new physics phase space which addresses the$$\textrm{B}$$ $\text{B}$-meson anomalies, for$$\textrm{LQ}$$ $\text{LQ}$masses up to$$5.00\, \textrm{TeV}$$ $5.00\text{TeV}$, for the high luminosity LHC scenario. 

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5. Search for leptoquark pair production decaying into $$te^- \bar{t}e^+$$ or $$t\mu ^- \bar{t}\mu ^+$$ in multi-lepton final states in pp collisions at $$\sqrt{s} = 13\,\textrm{TeV}$$ with the ATLAS detector

   https://doi.org/10.1140/epjc/s10052-024-12975-4  

   Aad, G; Abbott, B; Abbott, D C; Abeling, K; Abidi, S H; Aboulhorma, A; Abramowicz, H; Abreu, H; Abulaiti, Y; Hoffman, A_C Abusleme; et al (August 2024, The European Physical Journal C)

   Abstract A search for leptoquark pair production decaying into$$te^- \bar{t}e^+$$ $t{e}^{-}\overline{t}{e}^{+}$or$$t\mu ^- \bar{t}\mu ^+$$ $t{\mu }^{-}\overline{t}{\mu }^{+}$in final states with multiple leptons is presented. The search is based on a dataset ofppcollisions at$$\sqrt{s}=13~\text {TeV} $$ $\sqrt{s}=13\text{TeV}$recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb$$^{-1}$$ $_{}^{-1}$. Four signal regions, with the requirement of at least three light leptons (electron or muon) and at least two jets out of which at least one jet is identified as coming from ab-hadron, are considered based on the number of leptons of a given flavour. The main background processes are estimated using dedicated control regions in a simultaneous fit with the signal regions to data. No excess above the Standard Model background prediction is observed and 95% confidence level limits on the production cross section times branching ratio are derived as a function of the leptoquark mass. Under the assumption of exclusive decays into$$te^{-}$$ $t{e}^{-}$($$t\mu ^{-}$$ $t{\mu }^{-}$), the corresponding lower limit on the scalar mixed-generation leptoquark mass$$m_{\textrm{LQ}_{\textrm{mix}}^{\textrm{d}}}$$ $m_{{\text{LQ}}_{\text{mix}}^{\text{d}}}$is at 1.58 (1.59) TeV and on the vector leptoquark mass$$m_{{\tilde{U}}_1}$$ $m_{{\tilde{U}}_1}$at 1.67 (1.67) TeV in the minimal coupling scenario and at 1.95 (1.95) TeV in the Yang–Mills scenario. 

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