This paper presents a study of the production of $WW$ or $WZ$ boson pairs, with one $W$ boson decaying to $e\nu$ or $\mu\nu$ and one $W$ or $Z$ boson decaying hadronically. The analysis uses 20.2 fb$^{-1}$ of $\sqrt{s}=8$ TeV $pp$ collision data, collected by the ATLAS detector at the Large Hadron Collider. Cross-sections for $WW/WZ$ production are measured in high-$p_{T}$ fiducial regions defined close to the experimental event selection. The cross-section is measured for the case where the hadronically decaying boson is reconstructed as two resolved jets, and the case where it is reconstructed as a single jet. The transverse momentum distribution of the hadronically decaying boson is used to search for new physics. Observations are consistent with the Standard Model predictions, and $95\%$ confidence intervals are calculated for parameters describing anomalous triple gauge-boson couplings.

A measurement of the $ZZ$ production in the $\ell^{-}\ell^{+}\ell^{\prime -}\ell^{\prime +}$ and $\ell^{-}\ell^{+}\nu\bar{\nu}$ channels $(\ell = e, \mu)$ in proton--proton collisions at $\sqrt{s} = 8$ TeV at the Large Hadron Collider at CERN, using data corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected by the ATLAS experiment in 2012 is presented. The fiducial cross sections for $ZZ\to\ell^{-}\ell^{+}\ell^{\prime -}\ell^{\prime +}$ and $ZZ\to \ell^{-}\ell^{+}\nu\bar{\nu}$ are measured in selected phase-space regions. The total cross section for $ZZ$ events produced with both $Z$ bosons in the mass range 66 to 116 GeV is measured from the combination of the two channels to be $7.3\pm0.4\textrm{(stat)}\pm0.3\textrm{(syst)}\pm0.2\textrm{(lumi)}$ pb, which is consistent with the Standard Model prediction of $6.6^{+0.7}_{-0.6}$ pb. The differential cross sections in bins of various kinematic variables are presented. The differential event yield as a function of the transverse momentum of the leading $Z$ boson is used to set limits on anomalous neutral triple gauge boson couplings in $ZZ$ production.

The inclusive cross-section for jet production in association with a Z boson decaying into an electron-positron pair is measured as a function of the transverse momentum and the absolute rapidity of jets using 19.9 fb$^{-1}$ of $\sqrt s = 8$ TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The measured Z + jets cross-section is unfolded to the particle level. The cross-section is compared with state-of-the-art Standard Model calculations, including the next-to-leading-order and next-to-next-to-leading-order perturbative QCD calculations, corrected for non-perturbative and QED radiation effects. The results of the measurements cover final-state jets with transverse momenta up to 1 TeV, and show good agreement with fixed-order calculations.

The ratio of the cross sections for inclusive isolated-photon production in $pp$ collisions at centre-of-mass energies of 13 and 8 TeV is measured using the ATLAS detector at the LHC. The integrated luminosities of the 13 TeV and 8 TeV datasets are 3.2 fb$^{-1}$ and 20.2 fb$^{-1}$, respectively. The ratio is measured as a function of the photon transverse energy in different regions of the photon pseudorapidity. The predictions from next-to-leading-order perturbative QCD calculations are compared with the measured ratio. The experimental systematic uncertainties as well as the uncertainties affecting the predictions are evaluated taking into account the correlations between the two centre-of-mass energies, resulting in a reduction of up to a factor of $2.5$ ($5$) in the experimental (theoretical) systematic uncertainties. The predictions based on several parameterisations of the proton parton distribution functions agree with the data within the reduced experimental and theoretical uncertainties. In addition, this ratio to that of the fiducial cross sections for $Z$ boson production at 13 and 8 TeV using the decay channels $Z \rightarrow e^+e^-$ and $Z \rightarrow \mu^+\mu^-$ is made and compared with the theoretical predictions. In this double ratio, a further reduction of the experimental uncertainty is obtained because the uncertainties arising from the luminosity measurement cancel out. The predictions describe the measurements of the double ratio within the theoretical and experimental uncertainties.

The inclusive and fiducial $t\bar{t}$ production cross-sections are measured in the lepton+jets channel using 20.2 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. Major systematic uncertainties due to the modelling of the jet energy scale and $b$-tagging efficiency are constrained by separating selected events into three disjoint regions. In order to reduce systematic uncertainties in the most important background, the W+jets process is modelled using Z+jets events in a data-driven approach. The inclusive $t\bar{t}$ cross-section is measured with a precision of 5.7% to be $\sigma_{\text{inc}}(t\bar{t})$ = 248.3 $\pm$ 0.7 (stat.) $\pm$ 13.4 (syst.) $\pm$ 4.7 (lumi.) pb, assuming a top-quark mass of 172.5 GeV. The result is in agreement with the Standard Model prediction. The cross-section is also measured in a phase space close to that of the selected data. The fiducial cross-section is $\sigma_{\text{fid}}(t\bar{t})$ = 48.8 $\pm$ 0.1 (stat.) $\pm$ 2.0 (syst.) $\pm$ 0.9 (lumi.) pb with a precision of 4.5%.

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of $20.2~\mbox{fb$^{-1}$}$. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.

This paper presents single lepton and dilepton kinematic distributions measured in dileptonic $t\bar{t}$ events produced in 20.2 fb$^{-1}$ of $\sqrt{s}=8$ TeV $pp$ collisions recorded by the ATLAS experiment at the LHC. Both absolute and normalised differential cross-sections are measured, using events with an opposite-charge $e\mu$ pair and one or two $b$-tagged jets. The cross-sections are measured in a fiducial region corresponding to the detector acceptance for leptons, and are compared to the predictions from a variety of Monte Carlo event generators, as well as fixed-order QCD calculations, exploring the sensitivity of the cross-sections to the gluon parton distribution function. Some of the distributions are also sensitive to the top quark pole mass; a combined fit of NLO fixed-order predictions to all the measured distributions yields a top quark mass value of $m_t^{\rm pole}=173.2\pm 0.9\pm0.8\pm1.2$ GeV, where the three uncertainties arise from data statistics, experimental systematics, and theoretical sources.

Searches for exclusively produced $W$ boson pairs in the process $pp(\gamma\gamma) \rightarrow pW^+W^-p$ and exclusively produced Higgs boson in the process $pp(gg) \rightarrow pHp$ have been performed using $e^{\pm}\mu^{\mp}$ final states. These measurements use 20.2 fb$^{-1}$ of $pp$ collisions collected by the ATLAS experiment at a center-of-mass energy $\sqrt{s}=8$ TeV at the LHC. Exclusive production of $W^+W^-$ consistent with the Standard Model prediction is found with 3.0$\sigma$ significance. The exclusive $W^+W^-$ production cross-section is determined to be $\sigma (\gamma\gamma\rightarrow W^{+}W^{-}\rightarrow e^{\pm}\mu^{\mp} X) = 6.9 \pm 2.2 (\mathrm{stat.}) \pm 1.4 (\mathrm{sys.})$ fb, in agreement with the Standard Model prediction. Limits on anomalous quartic gauge couplings are set at 95\% confidence-level as $-1.7 \times 10^{-6} < a_0^W/\Lambda^2 < 1.7 \times 10^{-6}$ GeV$^{-2}$and $-6.4 \times 10^{-6} < a_C^W/\Lambda^2 < 6.3 \times 10^{-6}$ GeV$^{-2}$. A 95\% confidence-level upper limit on the total production cross-section for exclusive Higgs boson is set to 1.2 pb.

This paper presents a study of $WW\gamma$ and $WZ\gamma$ triboson production using events from proton--proton collisions at a centre-of-mass energy of $\sqrt{s} = 8$ TeV recorded with the ATLAS detector at the LHC and corresponding to an integrated luminosity of 20.2 fb$^{-1}$. The $WW\gamma$ production cross-section is determined using a final state containing an electron, a muon, a photon, and neutrinos ($e\nu\mu\nu\gamma$). Upper limits on the production cross-section of the $e\nu\mu\nu\gamma$ final state and the $WW\gamma$ and $WZ\gamma$ final states containing an electron or a muon, two jets, a photon, and a neutrino ($e\nu jj\gamma$ or $\mu\nu jj\gamma$) are also derived. The results are compared to the cross-sections predicted by the Standard Model at next-to-leading order in the strong-coupling constant. In addition, upper limits on the production cross-sections are derived in a fiducial region optimised for a search for new physics beyond the Standard Model. The results are interpreted in the context of anomalous quartic gauge couplings using an effective field theory. Confidence intervals at 95% confidence level are derived for the 14 coupling coefficients to which $WW\gamma$ and $WZ\gamma$ production are sensitive.

The production rates of prompt and non-prompt $J/\psi$ and $\psi(2\mathrm{S})$ mesons are measured using 2.1 $fb^{-1}$ and 11.4 $fb^{-1}$ of data collected with the ATLAS experiment at the LHC, in proton-proton collisions at $\sqrt{s}=7$ and 8 TeV respectively. Production cross-sections for both prompt and non-prompt production sources, ratios of $\psi(2\mathrm{S})$ to $J/\psi$ production, and fractions of non-prompt to inclusive production for $J/\psi$ and $\psi(2\mathrm{S})$ are measured double-differentially as a function of meson $p_{T}$ and rapidity. These measurements are made in a restricted fiducial volume and also corrected for geometrical acceptance after which they are compared to a variety of theoretical predictions.

Results of a search for the electroweak associated production of charginos and next-to-lightest neutralinos, pairs of charginos or pairs of tau sleptons are presented. These processes are characterised by final states with at least two hadronically decaying tau leptons, missing transverse momentum and low jet activity. The analysis is based on an integrated luminosity of 20.3 fb$^{-1}$ of proton--proton collisions at $\sqrt{s}=8$ TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess is observed with respect to the predictions from Standard Model processes. Limits are set at 95% confidence level on the masses of the lighter chargino and next-to-lightest neutralino for various hypotheses for the lightest neutralino mass in simplified models. In the scenario of direct production of chargino pairs, with each chargino decaying into the lightest neutralino via an intermediate tau slepton, chargino masses up to 345 GeV are excluded for a massless lightest neutralino. For associated production of mass-degenerate charginos and next-to-lightest neutralinos, both decaying into the lightest neutralino via an intermediate tau slepton, masses up to 410 GeV are excluded for a massless lightest neutralino.

A measurement of the splitting scales occuring in the $k_\mathrm{t}$ jet-clustering algorithm is presented for final states containing a $Z$ boson. The measurement is done using 20.2 fb$^{-1}$ of proton-proton collision data collected at a centre-of-mass energy of $\sqrt{s} = 8$ TeV by the ATLAS experiment at the LHC in 2012. The measurement is based on charged-particle track information, which is measured with excellent precision in the $p_\mathrm{T}$ region relevant for the transition between the perturbative and the non-perturbative regimes. The data distributions are corrected for detector effects, and are found to deviate from state-of-the-art predictions in various regions of the observables.

Detailed measurements of $t$-channel single top-quark production are presented. They use 20.2 fb$^{-1}$ of data collected by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of 8 TeV at the LHC. Total, fiducial and differential cross-sections are measured for both top-quark and top-antiquark production. The fiducial cross-section is measured with a precision of 5.8 % (top quark) and 7.8 % (top antiquark), respectively. The total cross-sections are measured to be $\sigma_{\mathrm{tot}}(tq) = 56.7^{+4.3}_{-3.8}\;$pb for top-quark production and $\sigma_{\mathrm{tot}}(\bar{t}q) = 32.9^{+3.0}_{-2.7}\;$pb for top-antiquark production, in agreement with the Standard Model prediction. In addition, the ratio of top-quark to top-antiquark production cross-sections is determined to be $R_t=1.72 \pm 0.09$, with an improved relative precision of 4.9 % since several systematic uncertainties cancel in the ratio. The differential cross-sections as a function of the transverse momentum and rapidity of both the top quark and the top antiquark are measured at both the parton and particle levels. The transverse momentum and rapidity differential cross-sections of the accompanying jet from the $t$-channel scattering are measured at particle level. All measurements are compared to various Monte Carlo predictions as well as to fixed-order QCD calculations where available.

This Letter presents the measurement of differential cross sections of isolated prompt photons produced in association with a b-jet or a c-jet. These final states provide sensitivity to the heavy-flavour content of the proton and aspects related to the modelling of heavy-flavour quarks in perturbative QCD. The measurement uses proton-proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of up to 20.2 fb$^{-1}$. The differential cross sections are measured for each jet flavour with respect to the transverse energy of the leading photon in two photon pseudorapidity regions: $|\eta^\gamma|<1.37$ and $1.56<|\eta^\gamma|<2.37$. The measurement covers photon transverse energies $25 < E_\textrm{T}^\gamma<400$ GeV and $25 < E_\textrm{T}^\gamma<350$ GeV respectively for the two $|\eta^\gamma|$ regions. For each jet flavour, the ratio of the cross sections in the two $|\eta^\gamma|$ regions is also measured. The measurement is corrected for detector effects and compared to leading-order and next-to-leading-order perturbative QCD calculations, based on various treatments and assumptions about the heavy-flavour content of the proton. Overall, the predictions agree well with the measurement, but some deviations are observed at high photon transverse energies. The total uncertainty in the measurement ranges between 13% and 66%, while the central $\gamma+b$ measurement exhibits the smallest uncertainty, ranging from 13% to 27%, which is comparable to the precision of the theoretical predictions.

The production of $W$ boson pairs in proton-proton collisions at $\sqrt{s}=$ 8 TeV is studied using data corresponding to 20.3 fb$^{-1}$ of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The $W$ bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 $WW$ candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the $W$ branching fractions to leptons in order to obtain the total $WW$ production cross section, which is found to be 71.1$\pm1.1$(stat)$^{+5.7}_{-5.0}$(syst)$\pm1.4$ pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63.2$^{+1.6}_{-1.4}$(scale)$\pm1.2$(PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. The distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.

The production of opposite-charge $W$-boson pairs in proton-proton collisions at $\sqrt{s}$ = 13 TeV is measured using data corresponding to 3.16 fb$^{-1}$ of integrated luminosity collected by the ATLAS detector at the CERN Large Hadron Collider in 2015. Candidate $W$-boson pairs are selected by identifying their leptonic decays into an electron, a muon and neutrinos. Events with reconstructed jets are not included in the candidate event sample. The cross-section measurement is performed in a fiducial phase space close to the experimental acceptance and is compared to theoretical predictions. Agreement is found between the measurement and the most accurate calculations available.

The production of a $Z$ boson in association with a $J/\psi$ meson in proton-proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and allows studies of multiple parton scattering. Using $20.3\, \mathrm{fb^{-1}}$ of data collected with the ATLAS experiment at the LHC in $pp$ collisions at $\sqrt{s}=8\, \mathrm{TeV}$, the first measurement of associated $Z + J/\psi$ production is presented for both prompt and non-prompt $J/\psi$ production, with both signatures having a significance in excess of $5\sigma$. The inclusive production cross-sections for $Z$ boson production (analysed in $\mu^+\mu^-$ or $e^+e^-$ decay modes) in association with prompt and non-prompt $J/\psi(\to\mu^+\mu^-)$ are measured relative to the inclusive production rate of $Z$ bosons in the same fiducial volume to be $(36.8\pm 6.7\pm 2.5) \times 10^{-7}$ and $(65.8\pm 9.2\pm 4.2) \times 10^{-7}$ respectively. Normalised differential production cross-section ratios are also determined as a function of the $J/\psi$ transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of $5.3\ (3.7)\, \mathrm{mb}$ at $68\ (95)$% confidence level is placed on the effective cross-section regulating double parton interactions.

A search is presented for pair production of a new heavy quark ($Q$) that decays into a $W$ boson and a light quark ($q$) in the final state where one $W$ boson decays leptonically (to an electron or muon plus a neutrino) and the other $W$ boson decays hadronically. The analysis is performed using an integrated luminosity of 20.3 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 8$ TeV collected by the ATLAS detector at the LHC. No evidence of $Q\bar{Q}$ production is observed. New chiral quarks with masses below 690 GeV are excluded at 95% confidence level, assuming BR$(Q\to Wq)=1$. Results are also interpreted in the context of vectorlike quark models, resulting in the limits on the mass of a vectorlike quark in the two-dimensional plane of BR$(Q\to Wq)$ versus BR$(Q\to Hq)$.

Measurements of fiducial cross sections for the electroweak production of two jets in association with a Z-boson are presented. The measurements are performed using 20.3 inverse femtobarns of proton-proton collision data collected at a centre-of-mass energy of sqrt(s)=8 TeV by the ATLAS experiment at the Large Hadron Collider. The electroweak component is extracted by a fit to the dijet invariant mass distribution in a fiducial region chosen to enhance the electroweak contribution over the dominant background in which the jets are produced via the strong interaction. The electroweak cross sections measured in two fiducial regions are in good agreement with the Standard Model expectations and the background-only hypothesis is rejected with significance above the 5 sigma level. The electroweak process includes the vector boson fusion production of a Z-boson and the data are used to place limits on anomalous triple gauge boson couplings. In addition, measurements of cross sections and differential distributions for inclusive Z-boson-plus-dijet production are performed in five fiducial regions, each with different sensitivity to the electroweak contribution. The results are corrected for detector effects and compared to predictions from the SHERPA and POWHEG event generators.

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.

A measurement of the production cross section for two isolated photons in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=8$ TeV is presented. The results are based on an integrated luminosity of 20.2 fb$^{-1}$ recorded by the ATLAS detector at the Large Hadron Collider. The measurement considers photons with pseudorapidities satisfying $|\eta^{\gamma}|<1.37$ or ${1.56<|\eta^{\gamma}|<2.37}$ and transverse energies of respectively $E_{\mathrm{T,1}}^{\gamma}>40$ GeV and $E_{\mathrm{T,2}}^{\gamma}>30$ GeV for the two leading photons ordered in transverse energy produced in the interaction.The background due to hadronic jets and electrons is subtracted using data-driven techniques. The fiducial cross sections are corrected for detector effects and measured differentially as a function of six kinematic observables. The measured cross section integrated within the fiducial volume is $16.8 \pm 0.8$ pb. The data are compared to fixed-order QCD calculations at next-to-leading-order and next-to-next-to-leading-order accuracy as well as next-to-leading-order computations including resummation of initial-state gluon radiation at next-to-next-to-leading logarithm or matched to a parton shower, with relative uncertainties varying from 5% to 20%.

This paper reports the results of a search for strong production of supersymmetric particles in 20.1 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of 8 TeV using the ATLAS detector at the LHC. The search is performed separately in events with either zero or at least one high $p_\mathrm{T}$ lepton (electron or muon), large missing transverse momentum, high jet multiplicity and at least three jets identified as originated from the fragmentation of a b-quark. No excess is observed with respect to the Standard Model predictions. The results are interpreted in the context of several supersymmetric models involving gluinos and scalar top and bottom quarks, as well as a mSUGRA/CMSSM model. Gluino masses up to 1340 GeV are excluded, depending on the model, significantly extending the previous ATLAS limits.

Differential cross sections are presented for the prompt and non-prompt production of the hidden-charm states $X(3872)$ and $\psi(2S)$, in the decay mode $J/\psi \pi^+\pi^-$, measured using 11.4 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 8$ TeV by the ATLAS detector at the LHC. The ratio of cross-sections $X(3872)/\psi(2S)$ is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of $X(3872)$ and $\psi(2S)$. Assuming independent single effective lifetimes for non-prompt $X(3872)$ and $\psi(2S)$ production gives $R_B = \frac{\mathcal{B}(B \rightarrow X(3872)\textrm{ + any}) \mathcal{B}(X(3872 \rightarrow J/\psi\pi^+\pi^-)}{\mathcal{B}(B \rightarrow \psi(2S)\textrm{ + any}) \mathcal{B}(\psi(2S) \rightarrow J/\psi\pi^+\pi^-)} = (3.95 \pm 0.32 \mathrm{(stat)} \pm 0.08\mathrm{(sys)}) \times 10^{-2}$, while separating short- and long-lived contributions, assuming that the short-lived component is due to $B_c$ decays, gives $R_B = (3.57 \pm 0.33\mathrm{(stat)} \pm 0.11\mathrm{(sys)}) \times 10^{-2}$, with the fraction of non-prompt $X(3872)$ produced via $B_c$ decays for $p_\mathrm{T}(X(3872)) > 10$ GeV being $(25 \pm 13\mathrm{(stat)} \pm 2\mathrm{(sys)} \pm 5\mathrm{(spin)})\%$. The distributions of the dipion invariant mass in the $X(3872)$ and $\psi(2S)$ decays are also measured and compared to theoretical predictions.

The differential cross-section for pair production of top quarks with high transverse momentum is measured in 20.3 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 8 TeV. The measurement is performed for $t\bar{t}$ events in the lepton+jets channel. The cross-section is reported as a function of the hadronically decaying top quark transverse momentum for values above 300 GeV. The hadronically decaying top quark is reconstructed as an anti-$k_t$ jet with radius parameter $R=1.0$ and identified with jet substructure techniques. The observed yield is corrected for detector effects to obtain a cross-section at particle level in a fiducial region close to the event selection. A parton-level cross-section extrapolated to the full phase space is also reported for top quarks with transverse momentum above 300 GeV. The predictions of a majority of next-to-leading-order and leading-order matrix-element Monte Carlo generators are found to agree with the measured cross-sections.

The production of a $Z$ boson and a photon in association with a high-mass dijet system is studied using 20.2fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV recorded with the ATLAS detector in 2012 at the Large Hadron Collider. Final states with a photon and a Z boson decaying into a pair of either electrons, muons, or neutrinos are analysed. Electroweak and total $pp \to Z\gamma j j$ cross-sections are extracted in two fiducial regions with different sensitivities to electroweak production processes. Quartic couplings of vector bosons are studied in regions of phase space with an enhanced contribution from pure electroweak production, sensitive to vector-boson scattering processes $VV \to Z\gamma$. No deviations from Standard Model predictions are observed and constraints are placed on anomalous couplings parameterized by higher-dimensional operators using effective field theory.