Temat: Standard Model - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Search for heavy Higgs bosons with flavour-violating couplings in multi-lepton plus b-jets final states in pp collisions at 13 TeV with the ATLAS detector
Autorzy:: Topolnicki, Kacper
Gil, Damian
Przygoda, Witold
Richter-Wąs, Elżbieta
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2920
Opis:: A search for new heavy scalars with flavour-violating decays in final states with multiple leptons and b-tagged jets is presented. The results are interpreted in terms of a general two-Higgs-doublet model involving an additional scalar with couplings to the top-quark and the three up-type quarks ($\rho_{tt}, \rho_{tc}$ and $\rho_{tu}$). The targeted signals lead to final states with either a same-sign top-quark pair, three top-quarks, or four top-quarks. The search is based on a data sample of proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb$^{−1}$. Events are categorised depending on the multiplicity of light charged leptons (electrons or muons), total lepton charge, and a deep-neural-network output to enhance the purity of each of the signals. Masses of an additional scalar boson m$_{H}$ between 200 − 630 GeV with couplings $\rho_{tt}$ = 0.4, $\rho_{tc}$ = 0.2, and $\rho_{tu}$ = 0.2 are excluded at 95% confidence level. Additional interpretations are provided in models of R-parity violating supersymmetry, motivated by the recent flavour and (g − 2)$_{μ}$ anomalies.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 2.

Tytuł:: Search for magnetic monopoles and stable particles with high electric charges in $\sqrt{s}$ = 13 TeV pp collisions with the ATLAS detector
Autorzy:: Przygoda, Witold
Richter-Wąs, Elżbieta
Topolnicki, Kacper
Gil, Damian
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2935
Opis:: We present a search for magnetic monopoles and high-electric-charge objects using LHC Run 2 $\sqrt{s}$ = 13 TeV proton-proton collisions recorded by the ATLAS detector. A total integrated luminosity of 138 fb$^{−1}$ was collected by a specialized trigger. No highly ionizing particle candidate was observed. Considering the Drell-Yan and photon-fusion pair production mechanisms as benchmark models, cross-section upper limits are presented for spin-0 and spin-1/2 magnetic monopoles of magnetic charge 1$_{g_{D}}$ and 2$_{g_{D}}$ and for high-electric-charge objects of electric charge 20 ≤ |z| ≤ 100, for masses between 200 GeV and 4000 GeV. The search improves by approximately a factor of three the previous cross-section limits on the Drell-Yan production of magnetic monopoles and high-electric charge objects. Also, the first ATLAS limits on the photon-fusion pair production mechanism of magnetic monopoles and high-electric-charge objects are obtained.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 3.

Tytuł:: Search for heavy neutral leptons in decays of W bosons using leptonic and semi-leptonic displaced vertices in $\sqrt{s}$ = 13 TeV pp collisions with the ATLAS detector
Autorzy:: Przygoda, Witold
Volkotrub, Yuriy
Richter-Wąs, Elżbieta
Gil, Damian
Procter, Tomasz
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2907
Opis:: A search is performed for long-lived heavy neutral leptons (HNLs), produced through the decay of a W boson along with a muon or electron. Two channels are explored: a leptonic channel, in which the HNL decays into two leptons and a neutrino, and a semi-leptonic channel, in which the HNL decays into a lepton and a charged pion. The search is performed with 140 fb$^{−1}$ of $\sqrt{s}$ = 13 TeV proton-proton collision data collected by ATLAS during Run 2 of the Large Hadron Collider. No excess of events is observed; Dirac-like and Majorana-like HNLs with masses below 14.5 GeV and mixing coefficients as small as 10$^{−7}$ are excluded at the 95% confidence level. The results are interpreted under different assumptions on the flavour of the leptons from the HNL decays.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 4.

Tytuł:: Exploration at the high-energy frontier : ATLAS Run 2 searches investigating the exotic jungle beyond the Standard Model
Autorzy:: Topolnicki, Kacper
Richter-Wąs, Elżbieta
Przygoda, Witold
Gil, Damian
Volkotrub, Yuriy
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2907
Opis:: This report presents a comprehensive collection of searches for new physics performed by the ATLAS Collaboration during the Run 2 period of data taking at the Large Hadron Collider, from 2015 to 2018, corresponding to about 140 fb$^{−1}$ of $\sqrt{s}$ = 13 TeV proton–proton collision data. These searches cover a variety of beyond-the-standard model topics such as dark matter candidates, new vector bosons, hidden-sector particles, leptoquarks, or vector-like quarks, among others. Searches for supersymmetric particles or extended Higgs sectors are explicitly excluded as these are the subject of separate reports by the Collaboration. For each topic, the most relevant searches are described, focusing on their importance and sensitivity and, when appropriate, highlighting the experimental techniques employed. In addition to the description of each analysis, complementary searches are compared, and the overall sensitivity of the ATLAS experiment to each type of new physics is discussed. Summary plots and statistical combinations of multiple searches are included whenever possible.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 5.

Tytuł:: Search for resonant production of dark quarks in the dijet final state with the ATLAS detector
Autorzy:: Przygoda, Witold
Richter-Wąs, Elżbieta
Topolnicki, Kacper
Gil, Damian
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2946
Opis:: This paper presents a search for a new Z′ resonance decaying into a pair of dark quarks which hadronise into dark hadrons before promptly decaying back as Standard Model particles. This analysis is based on proton-proton collision data recorded at $\sqrt{s}$ = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb$^{−1}$. After selecting events containing large-radius jets with high track multiplicity, the invariant mass distribution of the two highest-transverse-momentum jets is scanned to look for an excess above a data-driven estimate of the Standard Model multijet background. No significant excess of events is observed and the results are thus used to set 95% confidence-level upper limits on the production cross-section times branching ratio of the Z′ to dark quarks as a function of the Z′ mass for various dark-quark scenarios.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 6.

Tytuł:: Search for heavy, long-lived, charged particles with large ionisation energy loss in pp collisions at $\sqrt{s}$ = 13 TeV using the ATLAS experiment and the full Run 2 dataset
Autorzy:: Richter-Wąs, Elżbieta
Pałka, Marek
Gil, Damian
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2852
Opis:: This paper presents a search for hypothetical massive, charged, long-lived particles with the ATLAS detector at the LHC using an integrated luminosity of 139 fb$^{-1}$ of proton–proton collisions at $\sqrt{s}$ = 13 TeV. These particles are expected to move significantly slower than the speed of light and should be identifiable by their high transverse momenta and anomalously large specific ionisation losses, dE/dx. Trajectories reconstructed solely by the inner tracking system and a dE/dx measurement in the pixel detector layers provide sensitivity to particles with lifetimes down to $\mathcal{O}$(1) ns with a mass, measured using the Bethe–Bloch relation, ranging from 100 GeV to 3 TeV. Interpretations for pair-production of R-hadrons, charginos and staus in scenarios of supersymmetry compatible with these particles being long-lived are presented, with mass limits extending considerably beyond those from previous searches in broad ranges of lifetime.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 7.

Tytuł:: Search for neutral long-lived particles that decay into displaced jets in the ATLAS calorimeter in association with leptons or jets using pp collisions at $\sqrt{s}$ = 13 TeV
Autorzy:: Topolnicki, Kacper
Przygoda, Witold
Gil, Damian
Volkotrub, Yuriy
Richter-Wąs, Elżbieta
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2931
Opis:: A search for neutral long-lived particles (LLPs) decaying in the ATLAS hadronic calorimeter using 140 fb$^{−1}$ of proton-proton collisions at $\sqrt{s}$ = 13 TeV delivered by the LHC is presented. The analysis is composed of three channels. The first targets pair-produced LLPs, where at least one LLP is produced with sufficiently low boost that its decay products can be resolved as separate jets. The second and third channels target LLPs respectively produced in association with a W or Z boson that decays leptonically. In each channel, different search regions target different kinematic regimes, to cover a broad range of LLP mass hypotheses and models. No excesses of events relative to the background predictions are observed. Higgs boson branching fractions to pairs of hadronically decaying neutral LLPs larger than 1% are excluded at 95% confidence level for proper decay lengths in the range of 30 cm to 4.5 m depending on the LLP mass, a factor of three improvement on previous searches in the hadronic calorimeter. The production of long-lived dark photons in association with a Z boson with cross-sections above 0.1 pb is excluded for dark photon mean proper decay lengths in the range of 20 cm to 50 m, improving previous ATLAS results by an order of magnitude. Finally, long-lived photo-phobic axion-like particle models are probed for the first time by ATLAS, with production cross-sections above 0.1 pb excluded in the 0.1 mm to 10 m range.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 8.

Tytuł:: Search for single vector-like B quark production and decay via $B \to bH(b\bar{b})$ in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
Autorzy:: Richter-Wąs, Elżbieta
Pałka, Marek
Gil, Damian
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2861
Opis:: A search is presented for single production of a vector-like B quark decaying into a Standard Model b-quark and a Standard Model Higgs boson, which decays into a $b\bar{b}$ pair. The search is carried out in 139 fb$^{−1}$ of $\sqrt{s}$ = 13 TeV proton-proton collision data collected by the ATLAS detector at the LHC between 2015 and 2018. No significant deviation from the Standard Model background prediction is observed, and mass-dependent exclusion limits at the 95% confidence level are set on the resonance production cross-section in several theoretical scenarios determined by the couplings c$_{W}$, c$_{Z}$ and c$_{H}$ between the B quark and the Standard Model W, Z and Higgs bosons, respectively. For a vector-like B occurring as an isospin singlet, the search excludes values of cW greater than 0.45 for a B resonance mass (m$_{B}$) between 1.0 and 1.2 TeV. For 1.2 TeV < m$_{B}$ < 2.0 TeV, c$_{W}$ values larger than 0.50–0.65 are excluded. If the B occurs as part of a (B, Y) doublet, the smallest excluded c$_{Z}$ coupling values range between 0.3 and 0.5 across the investigated resonance mass range 1.0 TeV < m$_{B}$ < 2.0 TeV.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 9.

Tytuł:: Search for dark mesons decaying to top and bottom quarks in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
Autorzy:: Przygoda, Witold
Volkotrub, Yuriy
Richter-Wąs, Elżbieta
Gil, Damian
Topolnicki, Kacper
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2923
Opis:: A search for dark mesons originating from strongly-coupled, SU(2) dark flavor symmetry conserving models and decaying gaugephobically to pure Standard Model final states containing top and bottom quarks is presented. The search targets fully hadronic final states and final states with exactly one electron or muon and multiple jets. The analyzed data sample corresponds to an integrated luminosity of 140 fb$^{−1}$ of proton-proton collisions collected at $\sqrt{s}$ = 13 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess over the Standard Model background expectation is observed and the results are used to set the first direct constraints on this type of model. The two-dimensional signal space of dark pion masses $m_{\pi D}$ and dark rho-meson masses $m_{\rho D}$ is scanned. For $m_{\pi D} / m_{\rho D}$ = 0.45, dark pions with masses $m_{\pi D}$ < 940 GeV are excluded at the 95% CL, while for $m_{\pi D} / m_{\rho D}$ = 0.25 masses $m_{\pi D}$ < 740 GeV are excluded.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 10.

Tytuł:: Search for lepton-flavour violation in high-mass dilepton final states using 139 fb$^{−1}$ of pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
Autorzy:: Przygoda, Witold
Richter-Wąs, Elżbieta
Topolnicki, Kacper
Gil, Damian
Współwytwórcy:: Współautorami artykułu są członkowie ATLAS Collaboration w liczbie 2919
Opis:: A search is performed for a heavy particle decaying into different-flavour, dilepton final states, using 139 fb$^{−1}$ of proton-proton collision data at $\sqrt{s}$ = 13 TeV collected in 2015–2018 by the ATLAS detector at the Large Hadron Collider. Final states with electrons, muons and hadronically decaying tau leptons are considered (eμ, eτ or μτ). No significant excess over the Standard Model predictions is observed. Upper limits on the production cross-section are set as a function of the mass of a Z′ boson, a supersymmetric τ-sneutrino, and a quantum black-hole. The observed 95% CL lower mass limits obtained on a typical benchmark model Z′ boson are 5.0 TeV (eμ), 4.0 TeV (eτ), and 3.9 TeV (μτ), respectively.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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