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CERN-LHC. Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. This analysis uses a data sample of proton-proton collisions at $\sqrt{s}$ = 8 TeV corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split supersymmetry, and gauge mediation. In some of the search channels, the trigger and search strategy are based only on the decay products of individual long-lived particles, irrespective of the rest of the event. In these cases, the provided limits can easily be reinterpreted in different scenarios. Upper limits (95% CL) from the DV+$E_T^{miss}$ channel on the production cross-section and the corresponding event-level efficiencies (from Auxiliary Figure 9a) for two GGM SUSY models as a function of the $\tilde{\chi}_1^0$ proper decay distance $c\tau$. The models consider gluino pair production, with $\tilde{g}\to qq[\tilde{\chi}_1^0\to Z\tilde{G}]$ decays, $m(\tilde{g})$ = 1100 GeV and a $\tilde{\chi}_1^0$ mass in GeV as indicated. For comparison, the production cross-section for $m(\tilde{g})$ = 1100 GeV is $7.6\pm2.8$ fb.

CERN-LHC, ATLAS. A search for vector-like quarks is presented, which targets their decay into a $Z$ boson and a third-generation Standard Model quark. In the case of a vector-like quark $T$ ($B$) with charge $+2/3e$ ($-1/3e$), the decay searched for is $T \rightarrow Zt$ ($B \rightarrow Zb$). Data for this analysis were taken during 2015 and 2016 with the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 36.1 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}=13$ TeV. The final state used is characterized by the presence of $b$-tagged jets, as well as a $Z$ boson with high transverse momentum, which is reconstructed from a pair of opposite-sign same-flavor leptons. Pair- and single-production of vector-like quarks are both taken into account and are each searched for using optimized dileptonic exclusive and trileptonic inclusive event selections. In these selections, the high scalar sum of jet transverse momenta, the presence of high-transverse-momentum large-radius jets, as well as - in the case of the single-production selections - the presence of forward jets are used. No significant excess over the background-only hypothesis is found and exclusion limits at 95% confidence level allow masses of vector-like quarks of $m_T > 1030$ GeV ($m_T > 1210$ GeV) and $m_B > 1010$ GeV ($m_B > 1140$ GeV) in the singlet (doublet) model. In the case of 100% branching ratio for $T\rightarrow Zt$ ($B\rightarrow Zb$), the limits are $m_T > 1340$ GeV ($m_B > 1220$ GeV). Limits at 95% confidence level are also set on the coupling to Standard Model quarks for given vector-like quark masses. Signal cutflows for the $B\bar B$ process in the singlet model in the PP $2\ell$ $0-1$J channel in the 1-large-$R$ jet SR. Only statistical uncertainties are shown.

CERN-LHC. Search for the pair production of photon-jets---collimated groupings of photons---with the ATLAS detector. Highly collimated photon-jets can arise from the decay of new, highly boosted particles that can decay to multiple photons collimated enought to be identified in the electromagnetic calorimeter as a single, photon-like energy cluster. Data from proton–proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 36.7 fb$^{-1}$, were collected in 2015 and 2016. Upper limits are placed on $\sigma\times \mathcal{B}(X\rightarrow aa)\times \mathcal{B}(a\rightarrow\gamma\gamma)^2$ and $\sigma\times \mathcal{B}(X\rightarrow aa)\times \mathcal{B}(a\rightarrow 3\pi^0)^2$ for 200 GeV < $m_X$ < 2TeV and $m_a$ < 10 GeV. Tables 8 to 35 are provided to allow the recasting of the cross-section upper limits to different signal models predicting final states with photon-jets. These tables present the selection efficiency (before categorisation) $\varepsilon_{\gamma_R}(E_\mathrm{T},\eta)$ for reconstructed photons originating from a photon-jet, and the fraction $f_{\gamma_R}(E_\mathrm{T},\eta)$ of reconstructed photons with a value of the shower shape variable $\Delta E$ lower than the threshold. The fiducial region is defined as: - $E_\mathrm{T,1}>0.4\times m_X$ - $E_\mathrm{T,2}>0.3\times m_X$ - $|\eta_i| < 2.37 (i=1,2)$ (excluding $1.37 < |\eta_i| <1.52$) where $E_\mathrm{T,1}, \eta_1$ ($E_\mathrm{T,2}, \eta_2$) are the transverse energy and the pseudorapidity of the $a$ particle with the higher (the lower) transverse energy, respectively. For a resonance particle $X$ decaying into a pair of photon-jets via $X\rightarrow aa$, the total selection efficiency, $\varepsilon$, and the fraction of events in the low-$\Delta E$ category, $f$, can be computed by integrating over the p.d.f. of $(E_\mathrm{T,1},\eta_1,E_\mathrm{T,2},\eta_2)$ with the following procedure: - apply the fiducial cuts to the two $a$ particles - compute $\varepsilon$ from the integration of $\varepsilon_{\gamma_R}(E_\mathrm{T,1},\eta_1) \cdot \varepsilon_{\gamma_R}(E_\mathrm{T,2},\eta_2)$ - compute $f$ from the integration of $\varepsilon_{\gamma_R}(E_\mathrm{T,1},\eta_1) \cdot \varepsilon_{\gamma_R}(E_\mathrm{T,2},\eta_2) \cdot f_{\gamma_R}(E_\mathrm{T,1},\eta_1) \cdot f_{\gamma_R}(E_\mathrm{T,2},\eta_2)$ divided by $\varepsilon$ With the resulting value of $f$ for a given value of $m_X$, the 95% CL observed upper limit on the visible cross-section (i.e. $\sigma\times \mathcal{B}\times\varepsilon$) can be taken from Table 7, which is considered to be model-independent. The corresponding upper limit on the cross-section times branching ratios, $\sigma \times \mathcal{B}$, can be computed by dividing the obtained visible cross-section by $\varepsilon$. The estimation procedure described above is validated by comparing the results for the benchmark signal scenario decaying via $X\rightarrow aa\rightarrow 4\gamma$ with the results presented in the paper (i.e. Table 3). It is found that the two results agree within 20%, and the result with the estimation procedure described above gives lower values. The main difference is found for large values of the mass ratio, $0.005 The expected upper limits on the production cross-section times the product of branching ratios for the benchmark signal scenario involving a scalar particle $X$ with narrow width decaying via $X\rightarrow aa\rightarrow 4\gamma$, $\sigma_X\times B(X\rightarrow aa)\times B(a\rightarrow\gamma\gamma)^2$. The limits for $m_{a}$ = 5 GeV and 10 GeV do not cover as large a range as the other mass points, since the region of interest is limited to $ m_{a} < 0.01 \times m_{X}$. Additionally, the expected limits are not provided for a small number of points, indicated with a hyphen, because of a technical failure with the computation.

This paper presents results of searches for electroweak production of supersymmetric particles in models with compressed mass spectra. The searches use 139/fb of sqrt(s) = 13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider. Events with missing transverse momentum and two same-flavor, oppositely charged, low transverse momentum leptons are selected, and are further categorized by the presence of hadronic activity from initial-state radiation or a topology compatible with vector-boson fusion processes. The data are found to be consistent with predictions from the Standard Model. The results are interpreted using simplified models of R-parity-conserving supersymmetry in which the lightest supersymmetric partner is a neutralino with a mass similar to the lightest chargino, the second-to-lightest neutralino or the slepton. Lower limits on the masses of charginos in different simplified models range from 193 GeV to 240 GeV for moderate mass splittings, and extend down to mass splittings of 1.5 GeV to 2.4 GeV at the LEP chargino bounds (92.4 GeV). Similar lower limits on degenerate light-flavor sleptons extend up to masses of 251 GeV and down to mass splittings of 550 MeV. Constraints on vector-boson fusion production of electroweak SUSY states are also presented. Efficiency for the N2C1m VBF higgsino process in the SR-VBF-high region. Truth dilepton invariant mass is constrained to be within the range [1,40] GeV.

for Pb+Pb, pT>0.2GeV, 40<=Nch<60, wo SRC, opposite pairs No data abstract available.

CERN-LHC, ATLAS. A search for a right-handed gauge boson WR, decaying into a boosted right-handed heavy neutrino NR, in the framework of Left-Right Symmetric Models is presented. It is based on data from proton-proton collisions with a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015, 2016 and 2017, corresponding to an integrated luminosity of 80 fb−1. The search is performed separately for electrons and muons in the final state. A distinguishing feature of the search is the use of large-radius jets containing electrons. Selections based on the signal topology result in smaller background compared with to expected signal. No significant deviation from the Standard Model prediction is observed and lower limits are set in the WR and NR mass plane. Mass values of the WR smaller than 3.8-5 TeV are excluded for NR in the mass range 0.1-1.8 TeV. Expected 95% CL exclusion contours in the $(m_{N_R}, m_{W_R})$ plane in the electron channel.

CERN-LHC. A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded in 2015 and 2016 by the ATLAS experiment in $\sqrt{s}=13\mathrm{\ Te\kern -0.1em V}$ proton--proton collisions at the Large Hadron Collider, corresponding to an integrated luminosity of 36.1 fb$^{-1}$. The results are interpreted in the context of various models where squarks and gluinos are pair-produced and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.03$\mathrm{\ Te\kern -0.1em V}$ for a simplified model incorporating only a gluino and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.55$\mathrm{\ Te\kern -0.1em V}$ are excluded if the lightest neutralino is massless. These limits substantially extend the region of supersymmetric parameter space previously excluded by searches with the ATLAS detector. Observed and expected background and signal effective mass distributions for SR2j-2000. For signal, a squark direct decay model where squarks have mass of 1200 GeV and the neutralino1 has mass of 0 GeV is shown.

Exclusion curve for the simplified model of $\tilde\chi^{\pm}_{1}\tilde\chi^{\mp}_{1} + \tilde\chi^{0}_{1}\tilde\chi^{0}_{1}$ pair-production as a function of $\tilde\chi^{\pm}_{1}/\tilde\chi^{0}_{1}$ branching fraction to $Z$ and Higgs bosons. Results are shown for the charged-lepton decays of $\tilde\chi^{\pm}_{1}/\tilde\chi^{0}_{1}$ into muons only for a mass of 700 GeV. The expected 95% CL exclusion (dashed black line) is shown with $\pm1~\sigma_{\mathrm{exp}}$ (yellow band) from systematic and statistical uncertainties on the expected yields. The observed 95% CL exclusion (solid red line) is shown with the $\pm1~\sigma_{\mathrm{theory}}^{\mathrm{SUSY}}$ (dotted red line) from signal cross section uncertainties on the signal models. The phase-space excluded by the search is shown in the shaded color. No data abstract available.

The measured fiducial cross section P P --> WW --> $e^\pm \mu^\mp$. No description provided.

CERN-LHC. This paper presents measurements of $W^\pm Z$ production in $pp$ collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and muons. The data were collected in 2012 by the ATLAS experiment at the Large Hadron Collider, and correspond to an integrated luminosity of 20.3 fb$^{-1}$. The measured inclusive cross section in the detector fiducial region is $\sigma_{W^\pm Z \rightarrow \ell^{'} \nu\ \ell \ell} = 35.1 \pm$ 0.9 (stat.) $\pm 0.8$ (sys.) $\pm 0.8$ (lumi.) fb, for one leptonic decay channel. In comparison, the next-to-leading-order Standard Model expectation is 30.0 $\pm$ 2.1 fb. Cross sections for $W^+Z$ and $W^-Z$ production and their ratio are presented as well as differential cross sections for several kinematic observables. Limits on anomalous triple gauge boson couplings are derived from the transverse mass spectrum of the $W^\pm Z$ system. From the analysis of events with a $W$ and a $Z$ boson associated with two or more forward jets an upper limit at 95% confidence level on the $W^\pm Z$ scattering cross section of 0.63 fb, for each leptonic decay channel, is established, while the Standard Model prediction at next-to-leading order is 0.13 fb. Limits on anomalous quartic gauge boson couplings are also extracted The cross sections are measured in a fiducial phase space reflecting the detector acceptance, defined below. Fiducial phase space definition: - $p_{\mathrm{T}}$ of electrons and muons from Z0 decays > 15 GeV - $p_{\mathrm{T}}$ of electrons and muons from the $W^{\pm}$ decays > 20 GeV - $|\eta|$ of muons and electrons < 2.5 - Leptons from the Z0 boson are separated by $\Delta R(\ell,\ell) > 0.2$ from each other - Leptons from the Z0 and W bosons are separated by $\Delta R(\ell,\ell) > 0.3$ from each other - |dilepton mass - Z0 mass| < 10 GeV - $m_{\mathrm{T}}$ of $W^{\pm}$ > 30 GeV. At particle level, the kinematics of final-state prompt electrons and muons is computed including the contributions from final-state radiated photons within a distance in the ($\eta,\phi$) plane of $\Delta R = \sqrt{(\Delta\eta)^2 + (\Delta\phi)^2} = 0.1$ around the direction of the charged lepton. These dressed leptons and the final-state neutrinos that do not originate from hadron or $\tau$ decays are associated with the $W$ and $Z$ boson decay products with an algorithmic approach, called ``resonant shape''. This algorithm is based on the value of an estimator expressing the product of the nominal line shapes of the $W$ and $Z$ resonances $P = \left| \frac{1}{ m^2_{(\ell^+,\ell^-)} - \left(m_Z^{\textrm{PDG}}\right)^2 + i \; \Gamma_Z^{\textrm{PDG}} \; m_Z^{\textrm{PDG}} } \right|^2 \times \; \left| \frac {1} { m^2_{(\ell',\nu_{\ell'})} - \left(m_W^{\textrm{PDG}}\right)^2 + i \; \Gamma_W^{\textrm{PDG}} \; m_W^{\textrm{PDG}} } \right|^2$ where $m_Z^{\textrm{PDG}}$ ($m_W^{\textrm{PDG}}$) and $\Gamma_Z^{\textrm{PDG}}$ ($\Gamma_W^{\textrm{PDG}}$) are the world average mass and total width of the $Z$ ($W$) boson, respectively, as reported by the Particle Data Group~\cite{Agashe:2014kda}. The input to the estimator is the invariant mass $m$ of all possible pairs ($\ell^+,\ell^-$) and ($\ell',\nu_{\ell'}$) satisfying the fiducial selection requirements defined in the next paragraph. The final choice of which leptons are assigned to the $W$ or $Z$ bosons corresponds to the configuration exhibiting the highest value of the estimator. The inclusive cross section is also extrapolated to the total phase space and all W and Z boson decay modes. This result is model-dependent and includes phase space that was not experimentally accessible, so it should be used with caution. Whenever possible, the fiducial cross sections should be used instead, since they are only minimally model-dependent. Fiducial phase space for VBS measurement: additional criteria to the above Fiducial phase space definition - at least 2 jets - $p_{\mathrm{T}}$ of jets > 30 GeV - $|\eta|$ of jets < 4.5 - invariant mass of the 2 leading jets > 500 GeV - leptons and jets separated by $\Delta R(\ell,jet) > 0.3$ where jets are particle level jets with anti-kt R=0.4. Fiducial phase space for aQGC measurement: additional criteria to the above VBS phase space definition - difference in azimuthal angle between W and Z bosons directions $|\Delta \phi(W,Z)| > 2$ - scalar sum of the transverse momenta of the three charged leptons associated with W and Z bosons $\sum |p_{\mathrm{T}}^{\ell}| > 250$ GeV. Measured fiducial cross section in all $\ell'^\pm \nu \ell^+ \ell'^-$ channels combined, where $\ell, \ell' = e, \mu$. The first systematic uncertainty is the combined systematic uncertainty excluding theory and luminosity uncertainties, the second is the luminosity uncertainty. The last bin is a cross section for all events above the lower end of the bin.