Polarization and cross section of midrapidity J / ψ production in p + p collisions at s = 510 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
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J / ψ and ψ ( 2 S ) production at forward rapidity in p + p collisions at s = 510 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Improving constraints on gluon spin-momentum correlations in transversely polarized protons via midrapidity open-heavy-flavor electrons in p ↑ + p collisions at s = 200 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurement of Direct-Photon Cross Section and Double-Helicity Asymmetry at s = 510 GeV in p → + p → Collisions
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Transverse single-spin asymmetries of midrapidity π 0 and η mesons in polarized p + p collisions at s = 200 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized p + p collisions at s = 510 GeV
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for Scalar Leptoquarks Produced via τ -Lepton–Quark Scattering in p p Collisions at s = 13 TeV
The first search for scalar leptoquarks produced in τ -lepton–quark collisions is presented. It is based on a set of proton-proton collision data recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb − 1 . The reconstructed final state consists of a jet, significant missing transverse momentum, and a τ lepton reconstructed through its hadronic or leptonic decays. Limits are set on the product of the leptoquark production cross section and branching fraction and interpreted as exclusions in the plane of the leptoquark mass and the leptoquark- τ -quark coupling strength. © 2024 CERN, for the CMS Collaboration 2024 CERN
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Transverse-single-spin asymmetries of charged pions at midrapidity in transversely polarized p + p collisions at s = 200 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Transverse momentum dependent forward neutron single spin asymmetries in transversely polarized p + p collisions at s = 200 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Observation of Enhanced Long-Range Elliptic Anisotropies Inside High-Multiplicity Jets in p p Collisions at s = 13 TeV
A search for collective effects inside jets produced in proton-proton collisions is performed via correlation measurements of charged particles using the CMS detector at the CERN LHC. The analysis uses data collected at a center-of-mass energy of s = 13 TeV , corresponding to an integrated luminosity of 138 fb − 1 . Jets are reconstructed with the anti- k T algorithm with a distance parameter of 0.8 and are required to have transverse momentum greater than 550 GeV and pseudorapidity | η jet | < 1.6 . Two-particle correlations among the charged particles within the jets are studied as functions of the particles’ azimuthal angle and pseudorapidity separations ( Δ ϕ * and Δ η * ) in a jet coordinate basis, where particles’ η * , ϕ * are defined relative to the direction of the jet. The correlation functions are studied in classes of in-jet charged-particle multiplicity up to N ch j ≈ 100 . Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for | Δ η * | > 2 . For low- N ch j jets, the long-range elliptic anisotropic harmonic, v 2 * , is observed to decrease with N ch j . This trend is well described by Monte Carlo event generators. However, a rising trend for v 2 * emerges at N ch j ≳ 80 , hinting at a possible onset of collective behavior, which is not reproduced by the models tested. This observation yields new insights into the dynamics of jet evolution in the vacuum. © 2024 CERN, for the CMS Collaboration 2024 CERN
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for resonant pair production of Higgs bosons in the b b ¯ b b ¯ final state using p p collisions at s = 13 TeV with the ATLAS detector
A search for resonant Higgs boson pair production in the bb¯bb¯ final state is presented. The analysis uses 126 fb -1 -139 fb -1 of pp collision data at √s=13 TeV collected with the ATLAS detector at the Large Hadron Collider. The analysis is divided into two channels, targeting Higgs boson decays which are reconstructed as pairs of small-radius jets or as individual large-radius jets. Spin-0 and spin-2 benchmark signal models are considered, both of which correspond to resonant HH production via gluon-gluon fusion. The data are consistent with Standard Model predictions. Upper limits are set on the production cross section times branching ratio to Higgs boson pairs of a new resonance in the mass range from 251 GeV to 5 TeV.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for pair-produced vectorlike quarks coupling to light quarks in the lepton plus jets final state using 13 TeV p p collisions with the ATLAS detector
A search is presented for the pair production of heavy vectorlike quarks (VLQs) that each decay into a W boson and a light quark. This study focuses on events where one W boson decays into leptons and the other into hadrons. The search analyzed 140 fb -1 of pp collision data with $\sqrt{s}$ = 13 TeV, recorded by the ATLAS detector from 2015 to 2018 during run 2 of the Large Hadron Collider. The final state is characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum, multiple small-radius jets, and a single large-radius jet identified as originating from the hadronic decay of a boosted W boson. With higher center-of-mass energy and integrated luminosity than in the run 1 search, and improved analysis tools, this analysis excludes VLQs (Q) with masses below 1530 GeV at 95% confidence level for the branching ratio $\mathscr{B}$(Q →Wq) =1, an improvement of 840 GeV on the previous ATLAS limit.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for R -parity violating supersymmetric decays of the top squark to a b -jet and a lepton in s = 13 TeV p p collisions with the ATLAS detector
A search is presented for direct pair production of the stop, the supersymmetric partner of the top quark, in a decay through an R-parity violating coupling to a charged lepton and a b-quark. The dataset corresponds to an integrated luminosity of 140 fb -1 of proton-proton collisions at a center-of-mass energy of $\sqrt{s}$=13 TeV collected between 2015 and 2018 by the ATLAS detector at the LHC. The final state has two charged leptons (electrons or muons) and two b-jets. The results of the search are interpreted in the context of a Minimal Supersymmetric Standard Model with an additional B -L gauge symmetry that is spontaneously broken. No significant excess is observed over the Standard Model background, and exclusion limits on stop pair production are set at 95% confidence level. The corresponding lower limits on the stop mass for 100% branching ratios to a b-quark and an electron, muon, or tau-lepton are 1.9 TeV, 1.8 TeV and 800 GeV, respectively, extending the reach of previous LHC searches.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for long-lived neutral particles produced in pp collisions at root s=13 TeV decaying into displaced hadronic jets in the ATLAS inner detector and muon spectrometer
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Measurements of angular distance and momentum ratio distributions in three-jet and $${\text {Z}}$$ + two-jet final states in $${\text {p}}{\text {p}}$$ collisions
Collinear (small-angle) and large-angle, as well as soft and hard radiations are investigated in three-jet and Z + two-jet events collected in proton-proton collisions at the LHC. The normalized production cross sections are measured as a function of the ratio of transverse momenta of two jets and their angular separation. The measurements in the three-jet and Z + two-jet events are based on data collected at a center-of-mass energy of 8TeV, corresponding to an integrated luminosity of 19.8fb -1 . The Z + two-jet events are reconstructed in the dimuon decay channel of the Z boson. The three-jet measurement is extended to include $\sqrt {s}$=13TeV data corresponding to an integrated luminosity of 2.3fb -1 . The results are compared to predictions from event generators that include parton showers, multiple parton interactions, and hadronization. The collinear and soft regions are in general well described by parton showers, whereas the regions of large angular separation are often best described by calculations using higher-order matrix elements.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for vector-boson resonances decaying into a top quark and a bottom quark using $p p$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
A search for a new massive charged gauge boson, $W'$, is performed with the ATLAS detector at the LHC. The dataset used in this analysis was collected from proton–proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV, and corresponds to an integrated luminosity of 139 fb -1 . The reconstructed tb invariant mass is used to search for a $W'$ boson decaying into a top quark and a bottom quark. The result is interpreted in terms of a $W'$ boson with purely right-handed or left-handed chirality in a mass range of 0.5–6 TeV. Different values for the coupling of the $W'$ boson to the top and bottom quarks are considered, taking into account interference with single-top-quark production in the $s$-channel. No significant deviation from the background prediction is observed. The results are expressed as upper limits on the $W'$ → $tb$ production cross-section times branching ratio as a function of the $W'$-boson mass and in the plane of the coupling vs the $W'$-boson mass.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Measurement of differential t t ¯ production cross sections using top quarks at large transverse momenta in p p collisions at s = 13 TeV
A measurement is reported of differential top quark pair (${t\bar{t}}$) production cross sections, where top quarks are produced at large transverse momenta. The data collected with the CMS detector at the LHC are from pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The measurement uses events where at least one top quark decays as t$ \to $Wb $ \to q\bar{q}'b$ and is reconstructed as a large-radius jet with transverse momentum in excess of 400 GeV. The second top quark is required to decay either in a similar way, or leptonically, as inferred from a reconstructed electron or muon, a bottom quark jet, and a missing transverse momentum due to the undetected neutrino. The cross section is extracted as a function of kinematic variables of individual top quarks or of the ${t\bar{t}}$ system. The results are presented at the particle level, within a region of phase space close to that of the experimental acceptance, and at the parton level, and are compared to various theoretical models. In both decay channels the observed absolute cross sections are significantly lower than the predictions from theory, while the normalized differential measurements are well described.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for Dark Matter Produced in Association with a Dark Higgs Boson in the b b ¯ Final State Using p p Collisions at s = 13 TeV with the ATLAS Detector
A search is performed for dark matter particles produced in association with a resonantly produced pair of b -quarks with 30 < m b b < 150 GeV using 140 fb − 1 of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the LHC. This signature is expected in extensions of the standard model predicting the production of dark matter particles, in particular those containing a dark Higgs boson s that decays into b b ¯ . The highly boosted s → b b ¯ topology is reconstructed using jet reclustering and a new identification algorithm. This search places stringent constraints across regions of the dark Higgs model parameter space that satisfy the observed relic density, excluding dark Higgs bosons with masses between 30 and 150 GeV in benchmark scenarios with Z ′ mediator masses up to 4.8 TeV at 95% confidence level. © 2025 CERN, for the ATLAS Collaboration 2025 CERN
Aad, G. (ORCID:0000000266654934)↗