Measurements of top-quark pair to $Z$-boson cross-section ratios at $\sqrt s = 13, 8, 7$TeV with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
JHEP 02 (2017) 117, 2017.
Inspire Record 1502921 DOI 10.17182/hepdata.75536

Ratios of top-quark pair to $Z$-boson cross sections measured from proton--proton collisions at the LHC centre-of-mass energies of $\sqrt s=13$TeV, 8TeV, and 7TeV are presented by the ATLAS Collaboration. Single ratios, at a given $\sqrt s$ for the two processes and at different $\sqrt s$ for each process, as well as double ratios of the two processes at different $\sqrt s$, are evaluated. The ratios are constructed using previously published ATLAS measurements of the $t\overline{t}$ and $Z$-boson production cross sections, corrected to a common phase space where required, and a new analysis of $Z \rightarrow \ell^+ \ell^-$ where $\ell=e,\mu$ at $\sqrt s=13$TeV performed with data collected in 2015 with an integrated luminosity of $3.2$fb$^{-1}$. Correlations of systematic uncertainties are taken into account when evaluating the uncertainties in the ratios. The correlation model is also used to evaluate the combined cross section of the $Z\rightarrow e^+e^-$ and the $Z\rightarrow \mu^+ \mu^-$ channels for each $\sqrt s$ value. The results are compared to calculations performed at next-to-next-to-leading-order accuracy using recent sets of parton distribution functions. The data demonstrate significant power to constrain the gluon distribution function for the Bjorken-$x$ values near 0.1 and the light-quark sea for $x<0.02$.

11 data tables

Measured fiducial cross section times leptonic branching ratio for Z/gamma* production in the Z/gamma* -> e+e- final state at 13TeV.

Measured fiducial cross section times leptonic branching ratio for Z/gamma* production in the Z/gamma* -> mu+ mu- final state at 13TeV.

Breakdown of systematic uncertainties in percent for the measured fiducial cross section times leptonic branching ratio for Z/gamma* production in the Z/gamma* -> e+e- final state at 13TeV.

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Measurement of the cross section for inclusive isolated-photon production in $pp$ collisions at $\sqrt s=13$ TeV using the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Phys.Lett.B 770 (2017) 473-493, 2017.
Inspire Record 1510441 DOI 10.17182/hepdata.79798

Inclusive isolated-photon production in $pp$ collisions at a centre-of-mass energy of 13 TeV is studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 3.2 fb$^{-1}$. The cross section is measured as a function of the photon transverse energy above 125 GeV in different regions of photon pseudorapidity. Next-to-leading-order perturbative QCD and Monte Carlo event-generator predictions are compared to the cross-section measurements and provide an adequate description of the data.

8 data tables

Measured cross sections for inclusive isolated-photon production as a function of $E_{\rm T}^{\gamma}$ for $|\eta^{\gamma}|<0.6$.

Measured cross sections for inclusive isolated-photon production as a function of $E_{\rm T}^{\gamma}$ for $0.6<|\eta^{\gamma}|<1.37$.

Measured cross sections for inclusive isolated-photon production as a function of $E_{\rm T}^{\gamma}$ for $1.56<|\eta^{\gamma}|<1.81$.

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Version 2
Search for new phenomena in dijet events using 37 fb$^{-1}$ of $pp$ collision data collected at $\sqrt{s}=$13 TeV with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Phys.Rev.D 96 (2017) 052004, 2017.
Inspire Record 1519428 DOI 10.17182/hepdata.77265

Dijet events are studied in the proton--proton collision dataset recorded at $\sqrt{s}=$13 TeV with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to integrated luminosities of 3.5 fb$^{-1}$ and 33.5 fb$^{-1}$ respectively. Invariant mass and angular distributions are compared to background predictions and no significant deviation is observed. For resonance searches, a new method for fitting the background component of the invariant mass distribution is employed. The dataset is then used to set upper limits at a 95% confidence level on a range of new physics scenarios. Excited quarks with masses below 6.0 TeV are excluded, and limits are set on quantum black holes, heavy W' bosons, W* bosons, and a range of masses and couplings in a Z' dark matter mediator model. Model-independent limits on signals with a Gaussian shape are also set, using a new approach allowing factorization of physics and detector effects. From the angular distributions, a scale of new physics in contact interaction models is excluded for scenarios with either constructive or destructive interference. These results represent a substantial improvement over those obtained previously with lower integrated luminosity.

18 data tables

The number of events as a function of the dijet invariant mass, compared to background prediction from fit and corresponding uncertainties, in the region defined by |y*|<0.6

The number of events as a function of the dijet invariant mass, compared to background prediction from fit and corresponding uncertainties, in the region defined by |y*|<0.6

The number of events as a function of the dijet invariant mass, compared to background prediction from fit and corresponding uncertainties, in the region defined by |y*|<1.2 optimized for the W* search.

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Search for dark matter at $\sqrt{s}=13$ TeV in final states containing an energetic photon and large missing transverse momentum with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Eur.Phys.J.C 77 (2017) 393, 2017.
Inspire Record 1591328 DOI 10.17182/hepdata.77382

Results of a search for physics beyond the Standard Model in events containing an energetic photon and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. As the number of events observed in data, corresponding to an integrated luminosity of 36.1 $\textrm fb^{-1}$ of proton-proton collisions at a centre-of-mass energy of 13 TeV, is in agreement with the Standard Model expectations, exclusion limits in models where dark-matter candidates are pair-produced are determined. For dark-matter production via an axial-vector or a vector mediator in the s-channel, this search excludes mediator masses below 750-1200 GeV for dark-matter candidate masses below 230-480 GeV at 95% confidence level, depending on the couplings. In an effective theory of dark-matter production, the limits restrict the value of the suppression scale $M_{*}$ to be above 790 GeV at 95% confidence level. A limit is also reported on the production of a high-mass scalar resonance by processes beyond the Standard Model, in which the resonance decays to $Z\gamma$ and the Z boson subsequently decays into neutrinos.

24 data tables

Observed event yields in 36.1 fb$^{-1}$ of data compared to expected yields from SM backgrounds in all signal regions, as predicted from the simultaneous fit to their respective CRs. The first three lines report the yields obtained from the inclusive-SR fit, while the two last lines report the yields obtained from the multiple-bin fit. The uncertainty includes both the statistical and systematic uncertainties.

The observed 95% CL exclusion contour for a simplified model of dark-matter production involving an axial-vector operator, Dirac DM and couplings $g_{q}$ = 0.25, $g_{\chi}$ = 1 and $g_{l}$ = 0 as a function of the dark-matter mass $m_{\chi}$ and the mediator mass $m_{\mathrm{med}}$. The plane under the limit curve is excluded.

The expected 95% CL exclusion contour (+1$\sigma$) for a simplified model of dark-matter production involving an axial-vector operator, Dirac DM and couplings $g_{q}$ = 0.25, $g_{\chi}$ = 1 and $g_{l}$ = 0 as a function of the dark-matter mass $m_{\chi}$ and the mediator mass $m_{\mathrm{med}}$. The plane under the limit curve is excluded.

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Version 3
Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using $\sqrt{s}$ = 13 Tev proton-proton collision data

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
JHEP 09 (2017) 088, 2017.
Inspire Record 1597123 DOI 10.17182/hepdata.77491

A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton (electron or muon) and either zero or at least three $b$-tagged jets is presented. The search uses 36.1 fb$^{-1}$ of $\sqrt{s}$ = 13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the $b$-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits are extracted constraining four simplified models of $R$-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1 TeV in gluino mass and 1.2 TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model $t\bar{t}t\bar{t}$ production of 60 fb (6.5 $\times$ the Standard Model prediction) at 95% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields.

129 data tables

The expected background and observed data with five jets in the different b-tag multiplicity bins for the 40 GeV jet pT threshold. The background shown is estimated by including all bins in the fit.

The expected background and observed data with five jets in the different b-tag multiplicity bins for the 40 GeV jet pT threshold. The background shown is estimated by including all bins in the fit.

The expected background and observed data with five jets in the different b-tag multiplicity bins for the 40 GeV jet pT threshold. The background shown is estimated by including all bins in the fit.

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Measurement of multi-particle azimuthal correlations in $pp$, $p$+Pb and low-multiplicity Pb+Pb collisions with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Eur.Phys.J.C 77 (2017) 428, 2017.
Inspire Record 1599077 DOI 10.17182/hepdata.77996

Multi-particle cumulants and corresponding Fourier harmonics are measured for azimuthal angle distributions of charged particles in $pp$ collisions at $\sqrt{s}$ = 5.02 and 13 TeV and in $p$+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, and compared to the results obtained for low-multiplicity Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. These measurements aim to assess the collective nature of particle production. The measurements of multi-particle cumulants confirm the evidence for collective phenomena in $p$+Pb and low-multiplicity Pb+Pb collisions. On the other hand, the $pp$ results for four-particle cumulants do not demonstrate collective behaviour, indicating that they may be biased by contributions from non-flow correlations. A comparison of multi-particle cumulants and derived Fourier harmonics across different collision systems is presented as a function of the charged-particle multiplicity. For a given multiplicity, the measured Fourier harmonics are largest in Pb+Pb, smaller in $p$+Pb and smallest in $pp$ collisions. The $pp$ results show no dependence on the collision energy, nor on the multiplicity.

95 data tables

$c_2\{4\}$ cumulants for reference particles with 0.3 $< p_T <$ 3.0 GeV selected according to $M_{ref}$ (EvSel_$M_{ref}$) for pp collisions at $\sqrt{s}$= 5.02 TeV.

$c_2\{4\}$ cumulants for reference particles with 0.3 $< p_T <$ 3.0 GeV selected according to $M_{ref}$ (EvSel_$M_{ref}$) for pp collisions at $\sqrt{s}$= 13 TeV.

$c_2\{4\}$ cumulants for reference particles with 0.3 $< p_T <$ 3.0 GeV selected according to $M_{ref}$ (EvSel_$M_{ref}$) for pPb collisions at $\sqrt{ s_{NN} }$= 5.02 TeV.

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Search for the dimuon decay of the Higgs boson in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Phys.Rev.Lett. 119 (2017) 051802, 2017.
Inspire Record 1599399 DOI 10.17182/hepdata.78379

A search for the dimuon decay of the Higgs boson was performed using data corresponding to an integrated luminosity of 36.1 fb$^{-1}$ collected with the ATLAS detector in $pp$ collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider. No significant excess is observed above the expected background. The observed (expected) upper limit on the cross section times branching ratio is 3.0 (3.1) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125 GeV. When combined with the $pp$ collision data at $\sqrt{s}=7$ TeV and $\sqrt{s}=8$ TeV, the observed (expected) upper limit is 2.8 (2.9) times the Standard Model prediction.

3 data tables

Measurement of signal strength

Event yields for the expected signal (S) and background (B) processes, and numbers of the observed data events in different categories. The full widths at half maximum (FWHM) of the signal $m_{μμ}$ distributions are also shown. In each category, the event yields are counted within an $m_{μμ}$ interval, which is centered at the simulated signal peak and contains 90% of the expected signal events. The expected signal event yields are normalized to $36.1 fb^-1$. The background in each category is normalized to the observed data yield, while the relative fractions between the different processes are fixed to the SM predictions.

The 95% CL upper limit on signal strength


Search for pair production of vector-like top quarks in events with one lepton, jets, and missing transverse momentum in $\sqrt{s} = 13$ TeV pp collisions with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
JHEP 08 (2017) 052, 2017.
Inspire Record 1601647 DOI 10.17182/hepdata.77266

The results of a search for vector-like top quarks using events with exactly one lepton, at least four jets, and large missing transverse momentum are reported. The search is optimised for pair production of vector-like top quarks in the $Z(\rightarrow \! \! \nu \nu) \, t + X$ decay channel. LHC pp collision data at a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector in 2015 and 2016 are used, corresponding to an integrated luminosity of 36.1 $\mathrm{fb}^{-1}$. No significant excess over the Standard Model expectation is seen and upper limits on the production cross-section of a vector-like $T$ quark pair as a function of the $T$ quark mass are derived. The observed (expected) 95% CL lower limits on the $T$ mass are 870 GeV (890 GeV) for the weak-isospin singlet model, 1.05 TeV (1.06 TeV) for the weak-isospin doublet model and 1.16 TeV (1.17 TeV) for the pure $Zt$ decay mode. Limits are also set on the mass as a function of the decay branching ratios, excluding large parts of the parameter space for masses below 1 TeV.

5 data tables

Expected and observed 95% CL upper limit on the cross-section times branching ratio for VLQ $T$ pair production as a function of the $T$ mass for BR($T \rightarrow Zt$) = 100%.

Expected and observed 95% CL upper limit on the cross-section times branching ratio for VLQ $T$ pair production as a function of the $T$ mass for branching ratios according to the singlet model.

Expected and observed 95% CL upper limit on the cross-section times branching ratio for VLQ $T$ pair production as a function of the $T$ mass for branching ratios according to the doublet model. Contributions from the $X$ or $B$ quark in the $(X^{5/3}, T)$ or $(T, B)$ doublet models are neglected, leading to very conservative limits.

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Version 2
Search for supersymmetry in final states with two same-sign or three leptons and jets using 36 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
JHEP 09 (2017) 084, 2017.
Inspire Record 1604276 DOI 10.17182/hepdata.77719

A search for strongly produced supersymmetric particles using signatures involving multiple energetic jets and either two isolated same-sign leptons ($e$ or $\mu$), or at least three isolated leptons, is presented. The analysis relies on the identification of $b$-jets and high missing transverse momentum to achieve good sensitivity. A data sample of proton--proton collisions at $\sqrt{s}= 13$ TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to a total integrated luminosity of 36.1 fb$^{-1}$, is used for the search. No significant excess over the Standard Model prediction is observed. The results are interpreted in several simplified supersymmetric models featuring $R$-parity conservation or $R$-parity violation, extending the exclusion limits from previous searches. In models considering gluino pair production, gluino masses are excluded up to 1.87 TeV at 95% confidence level. When bottom squarks are pair-produced and decay to a chargino and a top quark, models with bottom squark masses below 700 GeV and light neutralinos are excluded at 95% confidence level. In addition, model-independent limits are set on a possible contribution of new phenomena to the signal region yields.

90 data tables

Observed 95% CL exclusion contours on the gluino and lightest neutralino masses in a SUSY scenario where gluinos are produced in pairs and decay directly into the lightest neutralino via an offshell top squark, $\tilde g\to t\bar{t}\tilde{\chi}_1^0$.

Observed 95% CL exclusion contours on the gluino and lightest neutralino masses in a SUSY scenario where gluinos are produced in pairs and decay directly into the lightest neutralino via an offshell top squark, $\tilde g\to t\bar{t}\tilde{\chi}_1^0$.

Expected 95% CL exclusion contours on the gluino and lightest neutralino masses in a SUSY scenario where gluinos are produced in pairs and decay directly into the lightest neutralino via an offshell top squark, $\tilde g\to t\bar{t}\tilde{\chi}_1^0$.

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Version 2
Search for a new heavy gauge boson resonance decaying into a lepton and missing transverse momentum in 36 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} =$ 13 TeV with the ATLAS experiment

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Eur.Phys.J.C 78 (2018) 401, 2018.
Inspire Record 1605396 DOI 10.17182/hepdata.77273

The results of a search for new heavy $W^\prime$ bosons decaying to an electron or muon and a neutrino using proton-proton collision data at a centre-of-mass energy of $\sqrt{s} = 13$ TeV are presented. The dataset was collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb$^{-1}$. As no excess of events above the Standard Model prediction is observed, the results are used to set upper limits on the $W^\prime$ boson cross-section times branching ratio to an electron or muon and a neutrino as a function of the $W^\prime$ mass. Assuming a $W^\prime$ boson with the same couplings as the Standard Model $W$ boson, $W^\prime$ masses below 5.1 TeV are excluded at the 95% confidence level.

12 data tables

Transverse mass distribution for events satisfying all selection criteria in the electron channel.

Transverse mass distribution for events satisfying all selection criteria in the electron channel.

Transverse mass distribution for events satisfying all selection criteria in the muon channel.

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