ATLAS reports an 8+ sigma excess in ttbar production near threshold, consistent with NRQCD quasi-bound states and measuring 9.3 pb.
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Parton distributions for the LHC Run II
Mixed citation behavior. Most common role is background (33%).
abstract
We present NNPDF3.0, the first set of parton distribution functions (PDFs) determined with a methodology validated by a closure test. NNPDF3.0 uses a global dataset including HERA-II deep-inelastic inclusive cross-sections, the combined HERA charm data, jet production from ATLAS and CMS, vector boson rapidity and transverse momentum distributions from ATLAS, CMS and LHCb, W+c data from CMS and top quark pair production total cross sections from ATLAS and CMS. Results are based on LO, NLO and NNLO QCD theory and also include electroweak corrections. To validate our methodology, we show that PDFs determined from pseudo-data generated from a known underlying law correctly reproduce the statistical distributions expected on the basis of the assumed experimental uncertainties. This closure test ensures that our methodological uncertainties are negligible in comparison to the generic theoretical and experimental uncertainties of PDF determination. This enables us to determine with confidence PDFs at different perturbative orders and using a variety of experimental datasets ranging from HERA-only up to a global set including the latest LHC results, all using precisely the same validated methodology. We explore some of the phenomenological implications of our results for the upcoming 13 TeV Run of the LHC, in particular for Higgs production cross-sections.
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representative citing papers
CMS provides first evidence for electroweak ZZjj production in the ℓℓννjj final state with measured cross section 0.37 fb agreeing with SM prediction 0.39 fb at 3.1σ (5.0σ combined), plus limits on anomalous quartic gauge couplings.
CMS measures Υ(1S,2S,3S) → τ⁺τ⁻ with 5.8σ significance and cross section 3.5 ± 0.7 (stat) ± 0.7 (syst) nb while setting 95% CL upper limits of 40-400 pb on spin-zero resonance production to ττ with no observed excess in 61.9 fb⁻¹ of 13.6 TeV data.
CMS measures soft-drop groomed radius and momentum balance plus a charged fragmentation function for b jets, observing dead-cone suppression compared to inclusive jets.
A framework based on linear response and influence functions maps data sensitivities in global QCD analyses to show how experiments determine central values, uncertainties, and correlations of non-perturbative functions.
N³LO QCD predictions for photon-pair production are presented, demonstrating perturbative convergence.
A physics-guided neural network embedding AdS5 Dirac equation and holographic Pomeron fits SLAC proton F2 data with chi-squared per degree of freedom of 0.91 and identifies a kinematic crossover at x approximately 0.19 while recovering Pomeron intercept of 1.0786.
No significant excess observed in search for SUEP signatures with muons; exclusion limits set on mediator cross section times branching fraction down to 0.05 fb at 750 GeV.
Top quark mass measured at 172.17 ± 1.56 GeV via unbinned maximum-likelihood fit to m(ℓ μ⁺μ⁻) in ATLAS Run 2 data using J/ψ decays.
ATLAS reports the observation of W⁺W⁻γ triboson production with 5.9σ significance and derives constraints on anomalous quartic gauge-boson couplings via effective field theory.
ATLAS reports a new measurement of the Higgs signal strength in the VBF plus photon channel with H to bb decay, obtaining 0.2 ± 0.7 using an improved neural-network-based analysis on 133 fb^{-1} of data.
Electroweak diboson plus high-mass dijet production observed at 7.4 sigma with signal strength 1.28, plus first semileptonic-channel limits on S02, T0 and M0 Wilson coefficients.
Continuous normalizing flows improve unweighting efficiency in Monte Carlo event generation for high-jet-multiplicity collider processes by factors up to 184, with wall-time gains of about ten when combined with coupling-layer flows.
No statistically significant excess is observed in the search for Higgs decays to two neutral scalars with unequal masses, setting 95% CL upper limits between 0.9 and 36.8 pb depending on mass and decay scenario.
No significant excess found; new exclusion limits reach m_H = 108 GeV for m_H - m_A = 78 GeV in the Inert Doublet Model.
ATLAS reports the first measurement of the complete angular coefficients and pT-differential cross sections for W+ and W- bosons in full lepton phase space at 13 TeV, finding agreement with QCD predictions up to order α_S².
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Loop-induced CS and selected CO SPS contributions to prompt J/ψ pairs are too small or kinematically limited to account for LHC data or affect DPS control regions.
A neural network trained solely on integral observables from a known GPD model recovers the main features of the underlying distributions in a closure test.
Fiducial cross-section for W+b-jets at 13 TeV measured as 16.6±1.9 pb, consistent with NLO QCD prediction of 16.8±2.3 pb with twice the previous precision.
Updated constraints from the full Run 2 dataset show no evidence for anomalous Higgs couplings in gluon fusion, vector boson fusion, and associated production modes decaying to two photons.
No evidence for charginos and neutralinos in R-parity violating Higgs-decay channels; masses 150-1100 GeV excluded at 95% CL assuming equal lepton branching fractions.
CMS deployed ML-based high-level triggers for hadronic tau leptons with high efficiency and low compute cost, validated on 62 fb^{-1} of 2022-2023 data.
No significant excess observed in search for X → S(bb)H(γγ); 95% CL limits on σ×BR set from 9 fb to 0.06 fb over m_X 170-1000 GeV and m_S 15-500 GeV in 199 fb^{-1} of ATLAS data.
citing papers explorer
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Observation of a cross-section enhancement near the $t\bar{t}$ production threshold in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
ATLAS reports an 8+ sigma excess in ttbar production near threshold, consistent with NRQCD quasi-bound states and measuring 9.3 pb.
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Observation of electroweak production of pairs of Z bosons in proton-proton collisions at 13 TeV
CMS provides first evidence for electroweak ZZjj production in the ℓℓννjj final state with measured cross section 0.37 fb agreeing with SM prediction 0.39 fb at 3.1σ (5.0σ combined), plus limits on anomalous quartic gauge couplings.
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Search for low-mass resonances decaying to $\tau\tau$ and measurement of the $\Upsilon$ $\to$ $\tau\tau$ decay in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV
CMS measures Υ(1S,2S,3S) → τ⁺τ⁻ with 5.8σ significance and cross section 3.5 ± 0.7 (stat) ± 0.7 (syst) nb while setting 95% CL upper limits of 40-400 pb on spin-zero resonance production to ττ with no observed excess in 61.9 fb⁻¹ of 13.6 TeV data.
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Jet fragmentation function and groomed substructure of bottom quark jets in proton-proton collisions at 5.02 TeV
CMS measures soft-drop groomed radius and momentum balance plus a charged fragmentation function for b jets, observing dead-cone suppression compared to inclusive jets.
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Mapping data sensitivities in global QCD analysis with linear response and influence functions
A framework based on linear response and influence functions maps data sensitivities in global QCD analyses to show how experiments determine central values, uncertainties, and correlations of non-perturbative functions.
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Next-to-next-to-next-to-leading order QCD corrections to photon-pair production
N³LO QCD predictions for photon-pair production are presented, demonstrating perturbative convergence.
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Probing Proton Structure via Physics-Guided Neural Networks in Holographic QCD
A physics-guided neural network embedding AdS5 Dirac equation and holographic Pomeron fits SLAC proton F2 data with chi-squared per degree of freedom of 0.91 and identifies a kinematic crossover at x approximately 0.19 while recovering Pomeron intercept of 1.0786.
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Search for soft unclustered energy patterns containing muons in the final state in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
No significant excess observed in search for SUEP signatures with muons; exclusion limits set on mediator cross section times branching fraction down to 0.05 fb at 750 GeV.
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Observation of $W^{+}W^{-}\gamma$ production in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector and constraints on anomalous quartic gauge-boson couplings
ATLAS reports the observation of W⁺W⁻γ triboson production with 5.9σ significance and derives constraints on anomalous quartic gauge-boson couplings via effective field theory.
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Search for Higgs boson decays into two neutral scalars with unequal masses in final states with b quarks and tau leptons in proton-proton collisions at $\sqrt{s}$ = 13 TeV
No statistically significant excess is observed in the search for Higgs decays to two neutral scalars with unequal masses, setting 95% CL upper limits between 0.9 and 36.8 pb depending on mass and decay scenario.
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On the ratio of $t\bar{t}\gamma$ and $t\bar{t}$ cross sections at the LHC
Computes the ratio of ttgamma/tt cross sections at LHC Run II with NLO QCD including off-shell effects, quantifying reduced theoretical uncertainties from correlations.
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Prompt ${J/\psi}$-pair production at the LHC: impact of loop-induced contributions and of the colour-octet mechanism
Loop-induced CS and selected CO SPS contributions to prompt J/ψ pairs are too small or kinematically limited to account for LHC data or affect DPS control regions.
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Neural Network Representation of Generalized Parton Distributions (NNGPD)
A neural network trained solely on integral observables from a known GPD model recovers the main features of the underlying distributions in a closure test.
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Measurement of the cross-section for the production of a $W$ boson in association with $b$-jets in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
Fiducial cross-section for W+b-jets at 13 TeV measured as 16.6±1.9 pb, consistent with NLO QCD prediction of 16.8±2.3 pb with twice the previous precision.
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Constraints on anomalous Higgs boson couplings to vector bosons and fermions using the $\gamma\gamma$ final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV
Updated constraints from the full Run 2 dataset show no evidence for anomalous Higgs couplings in gluon fusion, vector boson fusion, and associated production modes decaying to two photons.
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High-level hadronic tau lepton triggers of the CMS experiment in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV
CMS deployed ML-based high-level triggers for hadronic tau leptons with high efficiency and low compute cost, validated on 62 fb^{-1} of 2022-2023 data.
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Measurement of high-mass $t\bar{t}\ell^{+}\ell^{-}$ production and lepton flavour universality-inspired effective field theory interpretations at $\sqrt{s}=13$ TeV with the ATLAS detector
ATLAS reports a measurement of high-mass ttbar ll production with no observed deviation from the Standard Model and derives EFT constraints on four-fermion operators from 140 fb^{-1} of Run 2 data.
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Combined effective field theory interpretation of Higgs boson, electroweak vector boson, top quark, and multi-jet measurements
CMS performs a combined SMEFT fit to multiple LHC measurements and precision data, yielding individual constraints on 64 Wilson coefficients and 43 linear combinations.
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Study of $t\bar{t}$ threshold effects in $e\mu$ differential distributions measured in $\sqrt{s}=13$\,TeV $pp$ collisions with the ATLAS detector
ATLAS data on eμ invariant mass and angle distributions in 13 TeV collisions are better described by ttbar models that include color-singlet quasi-bound states near threshold, with fits showing over 3 sigma evidence and a cross-section matching dedicated threshold studies.
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Signals of New Resonances from Di-Lepton Non-Universality in the Bottomonium Mass Region at the Large Hadron Collider
Narrow spin-zero bosons with chirality-violating couplings can produce large di-tau non-universality in the bottomonium mass region at the LHC while preserving universality at e+e- colliders.
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Search for pair-produced vector-like $T$-quarks decaying into $Ht$ final states in the lepton-plus-jets channel in $pp$ collisions at $\sqrt{s}$=13 TeV with the ATLAS detector
No excess observed in search for vector-like T-quarks in Ht channel; 95% CL mass limits set at 1.40 TeV (SU(2) singlet), 1.56 TeV (doublet), and 1.66 TeV (100% BR to Ht).
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Studies of Z $\to$ 4$\ell$ decays in proton-proton collisions at $\sqrt{s}$ = 8 and 13 TeV
Measured inclusive B(Z → 4ℓ) = 4.67 ± 0.21 × 10^{-6} with individual modes, differential distributions, and triple-product asymmetry limits.
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Search for new physics in triple boson production in proton-proton collisions at $\sqrt{s}$ = 13 TeV using the effective field theory approach
No excess in VVV production; bounds set on c_W/Λ² (-0.13 to 0.12 TeV^{-2}) and c_Hq3/Λ² (-0.24 to 0.21 TeV^{-2}) at 95% CL.
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Threshold Top-Quark Pair-Production: Cross Sections and Key Uncertainties
Near-threshold top-quark pair production cross section at 13 TeV LHC is 11.67 pb with +1.43/-1.47 pb uncertainty, including NRQCD Green's function effects and comparison to POWHEG-BOX.
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Some Inverse Problems in Particle Physics
Lectures reviewing three established numerical methods for inverse problems in extracting PDFs and spectral functions from lattice QCD and experimental data.
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VBSCan Thessaloniki 2018 Workshop Summary
The document reports the first year of activity of the VBSCan COST Action network on vector-boson scattering phenomenology and experiments from a 2018 workshop.