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 13 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Dale ; et al.
CERN-EP-2023-087, 2023.
Inspire Record 2673386 DOI 10.17182/hepdata.150507

A search for leptoquark pair production decaying into $te^- \bar{t}e^+$ or $t\mu^- \bar{t}\mu^+$ in final states with multiple leptons is presented. The search is based on a dataset of $pp$ 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 selected with two or more light leptons (electron or muon) and at least two jets out of which at least one jet is identified as coming from a $b$-hadron. Four signal regions, with the requirement of at least three light leptons, 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 $te^{-}$ ($t\mu^{-}$), the corresponding lower limit on the scalar mixed-generation leptoquark mass $m_{\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}}$ is at 1.58 (1.59) TeV and on the vector leptoquark mass $m_{\tilde{U}_1}$ at 1.67 (1.67) TeV in the minimal coupling scenario and at 1.95 (1.95) TeV in the Yang-Mills scenario.

8 data tables

Selection efficiency times acceptance summed over two signal regions for the scalar leptoquark signals as a function of $m_{\mathrm{LQ}_{mix}^{\mathrm{d}}}$, assuming B = 1.

Selection efficiency times acceptance summed over two signal regions for the vector leptoquark signals as a function of $m_{\tilde{U}_{1}}$, assuming B = 1 and Yang-Mills coupling scenario.

Summary of the observed and expected 95% CL upper limits on the cross section for $\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}$ pair production as a function of $m_{\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}}$ under the assumptions of B(LQ$\rightarrow te$)=1.

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Version 2
Measurement of detector-corrected observables sensitive to the anomalous production of events with jets and large missing transverse momentum in $pp$ collisions at $\sqrt{s} = 13$ TeV using the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Eur.Phys.J.C 77 (2017) 765, 2017.
Inspire Record 1609448 DOI 10.17182/hepdata.78366

Observables sensitive to the anomalous production of events containing hadronic jets and missing momentum in the plane transverse to the proton beams at the Large Hadron Collider are presented. The observables are defined as a ratio of cross sections, for events containing jets and large missing transverse momentum to events containing jets and a pair of charged leptons from the decay of a $Z/\gamma^\ast$ boson. This definition minimises experimental and theoretical systematic uncertainties in the measurements. This ratio is measured differentially with respect to a number of kinematic properties of the hadronic system in two phase-space regions; one inclusive single-jet region and one region sensitive to vector-boson-fusion topologies. The data are found to be in agreement with the Standard Model predictions and used to constrain a variety of theoretical models for dark-matter production, including simplified models, effective field theory models, and invisible decays of the Higgs boson. The measurements use 3.2 fb$^{-1}$ of proton--proton collision data recorded by the ATLAS experiment at a centre-of-mass energy of 13 TeV and are fully corrected for detector effects, meaning that the data can be used to constrain new-physics models beyond those shown in this paper.

14 data tables

Measured and expected $R^\text{miss}$ as a function of $p_\text{T}^\text{miss}$ in the $\geq 1$ jet phase space. The fiducial SM predictions for the numerator and the denominator are also given.

Measured and expected $R^\text{miss}$ as a function of $p_\text{T}^\text{miss}$ in the $\geq 1$ jet phase space. The fiducial SM predictions for the numerator and the denominator are also given.

Measured and expected $R^\text{miss}$ as a function of $p_\text{T}^\text{miss}$ in the VBF jet phase space. The fiducial SM predictions for the numerator and the denominator are also given.

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Exclusive dimuon production in ultraperipheral Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV with ATLAS

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Brad ; et al.
Phys.Rev.C 104 (2021) 024906, 2021.
Inspire Record 1832628 DOI 10.17182/hepdata.104407

Exclusive dimuon production in ultraperipheral collisions (UPC), resulting from photon-photon interactions in the strong electromagnetic fields of colliding high-energy lead nuclei, $\mathrm{PbPb}(\gamma\gamma) \rightarrow \mu^+\mu^- (\mathrm{Pb}^{(\star)}\mathrm{Pb}^{(\star)} )$, is studied using $\mathcal{L}_{\mathrm{int}} = 0.48$ nb$^{-1}$ of $\sqrt{s_\mathrm{NN}}=5.02$ TeV lead-lead collision data at the LHC with the ATLAS detector. Dimuon pairs are measured in the fiducial region $p_{\mathrm{T}\mu} > 4$ GeV, $|\eta_{\mu}| < 2.4$, invariant mass $m_{\mu\mu} > 10$ GeV, and $p_{\mathrm{T,\mu\mu}} < 2$ GeV. The primary background from single-dissociative processes is extracted from the data using a template fitting technique. Differential cross sections are presented as a function of $m_{\mu\mu}$, absolute pair rapidity ($|y_{\mu\mu}|$), scattering angle in the dimuon rest frame ($|\cos \vartheta^{\star}_{\mu\mu}|$) and the colliding photon energies. The total cross section of the UPC $\gamma \gamma \rightarrow \mu^{+}\mu^{-}$ process in the fiducial volume is measured to be $\sigma_{\mathrm{fid}}^{\mu\mu} = 34.1 \! \pm \! 0.3 \mathrm{(stat.)} \! \pm \! 0.7 \mathrm{(syst.)}$ $\mu\mathrm{b}$. Generally good agreement is found with calculations from STARlight, which incorporate the leading-order Breit-Wheeler process with no final-state effects, albeit differences between the measurements and theoretical expectations are observed. In particular, the measured cross sections at larger $|y_{\mu\mu}|$ are found to be about 10-20% larger in data than in the calculations, suggesting the presence of larger fluxes of photons in the initial state. Modification of the dimuon cross sections in the presence of forward and/or backward neutron production is also studied and is found to be associated with a harder incoming photon spectrum, consistent with expectations.

41 data tables

Differential UPC dimuon cross sections shown as a function of $|y_{\mu\mu}|$ in the interval $10 < |m_{\mu\mu}| < 20$ GeV.

Differential UPC dimuon cross sections shown as a function of $|y_{\mu\mu}|$ in the interval $20 < |m_{\mu\mu}| < 40$ GeV.

Differential UPC dimuon cross sections shown as a function of $|y_{\mu\mu}|$ in the interval $40 < |m_{\mu\mu}| < 80$ GeV.

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Measurement of light-by-light scattering and search for axion-like particles with 2.2 nb$^{-1}$ of Pb+Pb data with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
JHEP 11 (2021) 050, 2021.
Inspire Record 1811464 DOI 10.17182/hepdata.95747

This paper describes a measurement of light-by-light scattering based on Pb+Pb collision data recorded by the ATLAS experiment during Run 2 of the LHC. The study uses $2.2$ nb$^{-1}$ of integrated luminosity collected in 2015 and 2018 at $\sqrt{s_\mathrm{NN}}=5.02$ TeV. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy $E_{\mathrm{T}}^{\gamma} > 2.5$ GeV, pseudorapidity $|\eta_{\gamma}| < 2.37$, diphoton invariant mass $m_{\gamma\gamma} > 5$ GeV, and with small diphoton transverse momentum and diphoton acoplanarity. The integrated and differential fiducial cross sections are measured and compared with theoretical predictions. The diphoton invariant mass distribution is used to set limits on the production of axion-like particles. This result provides the most stringent limits to date on axion-like particle production for masses in the range 6-100 GeV. Cross sections above 2 to 70 nb are excluded at the 95% CL in that mass interval.

11 data tables

Measured differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for diphoton invariant mass are shown as points with error bars giving the statistical uncertainty and grey bands indicating the size of the total uncertainty. The results are compared with the prediction from the SuperChic v3.0 MC generator (solid line) with bands denoting the theoretical uncertainty.

Measured normalised differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for diphoton invariant mass are shown as points with error bars giving the statistical uncertainty and grey bands indicating the size of the total uncertainty. The results are compared with the prediction from the SuperChic v3.0 MC generator (solid line).

Measured differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for diphoton $|cos(\theta*)|$ are shown as points with error bars giving the statistical uncertainty and grey bands indicating the size of the total uncertainty. The results are compared with the prediction from the SuperChic v3.0 MC generator (solid line) with bands denoting the theoretical uncertainty.

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Azimuthal decorrelations and multiple parton interactions in photon+2 jet and photon+3 jet events in ppbar collisions at sqrt{s}=1.96 TeV

The D0 collaboration Abazov, Victor Mukhamedovich ; Abbott, Braden Keim ; Acharya, Bannanje Sripath ; et al.
Phys.Rev.D 83 (2011) 052008, 2011.
Inspire Record 883664 DOI 10.17182/hepdata.63845

Samples of inclusive photon+2 jet and photon+3 jet events collected by the D0 experiment with an integrated luminosity of about 1fb^-1 in ppbar collisions at sqrt{s}=1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (pT) of the photon+leading jet system (jets are ordered in pT) and pT of the other jet for photon+2 jet, or pT sum of the two other jets for photon+3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well described by predictions provided by the PYTHIA MPI models with pT-ordered showers and by SHERPA with the default MPI model. The photon+2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet pT.

4 data tables

The normalised differential cross section of the azmiuthal decorrelation variable DELTA for the GAMMA+3JET sample for the PT of the second jet in the range 15 TO 30 GeV.

The normalised differential cross section of the azmiuthal decorrelation variable DELTA for the GAMMA+2JET sample for the PT of the second jet in the range 15 TO 20 GeV.

The normalised differential cross section of the azmiuthal decorrelation variable DELTA for the GAMMA+2JET sample for the PT of the second jet in the range 20 TO 25 GeV.

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Measurement of three-jet differential cross sections d sigma-3jet / d M-3jet in p anti-p collisions at sqrt(s)=1.96 TeV

The D0 collaboration Abazov, Victor Mukhamedovich ; Abbott, Braden Keim ; Acharya, Bannanje Sripath ; et al.
Phys.Lett.B 704 (2011) 434-441, 2011.
Inspire Record 895662 DOI 10.17182/hepdata.58856

We present the first measurement of the inclusive three-jet differential cross section as a function of the invariant mass of the three jets with the largest transverse momenta in an event in p anti-p collisions at sqrt(s) = 1.96 TeV. The measurement is made in different rapidity regions and for different jet transverse momentum requirements and is based on a data set corresponding to an integrated luminosity of 0.7 fb^{-1} collected with the D0 detector at the Fermilab Tevatron Collider. The results are used to test the three-jet matrix elements in perturbative QCD calculations at next-to-leading order in the strong coupling constant. The data allow discrimination between parametrizations of the parton distribution functions of the proton.

5 data tables

The measured 3-jet differential cross section for |y|<0.8 and pT>40 GeV.

The measured 3-jet differential cross section for |y|<1.6 and pT>40 GeV.

The measured 3-jet differential cross section for |y|<2.4 and pT>40 GeV.

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Measurement of the normalized Z/gamma*->mu+mu- transverse momentum distribution in p\bar{p} collisions at sqrt{s}=1.96 TeV

The D0 collaboration Abazov, Victor Mukhamedovich ; Abbott, Braden Keim ; Abolins, Maris A. ; et al.
Phys.Lett.B 693 (2010) 522-530, 2010.
Inspire Record 856972 DOI 10.17182/hepdata.55457

We present a new measurement of the Z/gamma* transverse momentum distribution in the range 0 - 330GeV, in proton-antiproton collisions at sqrt{s}=1.96 TeV. The measurement uses 0.97 fb-1 of integrated luminosity recorded by the D0 experiment and is the first using the Z/gamma*->mu+mu- + X channel at this center-of-mass energy. This is also the first measurement of the Z/gamma* transverse momentum distribution that presents the result at the level of particles entering the detector, minimizing dependence on theoretical models. As any momentum of the Z/gamma* in the plane transverse to the incoming beams must be balanced by some recoiling system, primarily the result of QCD radiation in the initial state, this variable is an excellent probe of the underlying process. Tests of the predictions of QCD calculations and current event generators show they have varied success in describing the data. Using this measurement as an input to theoretical predictions will allow for a better description of hadron collider data and hence it will increase experimental sensitivity to rare signals.

2 data tables

Normalized differential cross section.

Absolute differential cross section produced by multiplying by the measuredtotal cross section (118 pb).


Measurement of $Z / \gamma^\ast +jet+X$ angular distributions in $p \bar{p}$ collisions at $\sqrt{s}=1.96$ TeV

The D0 collaboration Abazov, Victor Mukhamedovich ; Abbott, Braden Keim ; Abolins, Maris A. ; et al.
Phys.Lett.B 682 (2010) 370-380, 2010.
Inspire Record 826756 DOI 10.17182/hepdata.52513

We present the first measurements at a hadron collider of differential cross sections for Z+jet+X production in delta phi(Z, jet), |delta y(Z, jet)| and |y_boost(Z, jet)|. Vector boson production in association with jets is an excellent probe of QCD and constitutes the main background to many small cross section processes, such as associated Higgs production. These measurements are crucial tests of the predictions of perturbative QCD and current event generators, which have varied success in describing the data. Using these measurements as inputs in tuning event generators will increase the experimental sensitivity to rare signals.

12 data tables

Differential cross section in bins of PHI(P=3)-PHI(P=4) for Z/GAMMA* transverse momentum > 25 GeV.

Differential cross section in bins of PHI(P=3)-PHI(P=4) for Z/GAMMA* transverse momentum > 45 GeV.

Differential cross section in bins of ABS(YRAP(P=3)-YRAP(P=4)) for Z/GAMMA* transverse momentum > 25 GeV.

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Precise study of the Z/gamma* boson transverse momentum distribution in ppbar collisions using a novel technique

The D0 collaboration Abazov, Victor Mukhamedovich ; Abbott, Braden Keim ; Abolins, Maris A. ; et al.
Phys.Rev.Lett. 106 (2011) 122001, 2011.
Inspire Record 871787 DOI 10.17182/hepdata.56732

Using 7.3 pb-1 of ppbar collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable \phistar, which probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the \phistar distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.

2 data tables

The measured PHI* distributions for the dielectron events corrected back to the particle level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.

The measured PHI* distributions for the dimuon events corrected back to the particle level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.