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UC Santa Cruz

Open Access Policy Deposits

This series is automatically populated with publications deposited by UC Santa Cruz Department of Physics researchers in accordance with the University of California’s open access policies. For more information see Open Access Policy Deposits and the UC Publication Management System.

Cover page of Review of Particle Physics*

Review of Particle Physics*

(2026)

The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 3,200 new measurements from 903 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Most of the 118 reviews are updated, including many that are heavily revised. The Review is divided into two volumes. Volume 1 includes the Summary Tables and 96 review articles. Volume 2 consists of the Particle Listings and contains also 22 reviews that address specific aspects of the data presented in the Listings. The complete Review (both volumes) is published online on the website of the Particle Data Group ( pdg.lbl.gov ) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print, as a web version optimized for use on phones, and as an Android app. The PDG API (Application Programming Interface) provides access to the data published in the Review in machine-readable format.

Combined effective field theory interpretation of measurements sensitive to quartic gauge boson couplings in pp collisions at s = 13 TeV with the ATLAS detector

(2026)

A combination of measurements sensitive to anomalous quartic electroweak gauge boson couplings is presented using proton–proton collision data collected by the ATLAS detector at s = 13 TeV at the LHC. Contributing analyses include measurements of vector-boson scattering in numerous final states as well as a tri-boson measurement. The combined measurement is used to constrain anomalous electroweak boson quartic self-couplings that result from dimension-8 operators in the Éboli model using an effective field theory. Results are presented as 68% and 95% confidence level intervals parameterised by one or two Wilson coefficients, both with and without unitarity constraints applied. Theoretical bounds from unitarity and positivity are overlaid where relevant. Confidence intervals obtained from simultaneous profiled fits to all Wilson coefficients are also presented.

A comparison of relative stopping power derived by fast kV‐switching dual‐energy CT, single‐energy CT, and proton CT in phantom and tissue

(2026)

BACKGROUND: The accuracy of relative stopping power (RSP) is a critical aspect for safe treatment planning in proton therapy. Dual-energy CT (DECT) has the ability to estimate RSP more accurately than conventional single-energy CT (SECT) due to its improved material separation. RSP accuracy is commonly determined in homogeneous phantom material as it can be more challenging to determine in heterogeneous biological tissues. Proton CT (pCT) is a modality that directly determines RSP and can be used as a comparative benchmark for evaluating the RSP accuracy of DECT and SECT derived values across homogeneous and heterogeneous material. PURPOSE: In this study, DECT was compared to SECT in both homogeneous phantom inserts of known RSP and heterogeneous tissue samples of unknown RSP using pCT as a quantitative reference. The purpose of this study was to assess the ability of DECT to improve RSP estimation over SECT in unknown RSP of heterogeneous tissues. METHODS: A variety of homogeneous phantom inserts were scanned using pCT, DECT, and SECT. The estimated RSP from each imaging modality was compared to the RSP of each insert directly measured using a multilayer ionization chamber (MLIC). Scans of heterogeneous tissue samples were also acquired using pCT, DECT, and SECT. The images from each modality were registered and a variety of tissue regions of interest were contoured. The percent difference of DECT and SECT derived RSP values compared to pCT was calculated across both homogeneous phantom and heterogeneous tissue regions and compared. RESULTS: The mean absolute percentage error for the inserts compared to the known RSP was 1.6% ± 1.6% in pCT, 1.1% ± 1.6% in DECT, and 4.6% ± 6.2% in SECT. For inserts with relative electron density greater than 0.93 and excluding true water and aluminum, DECT average percent difference compared to pCT was -0.5% ± 0.02% while in SECT it was -1.5% ± 0.07%. In biological tissue, excluding enamel, the average percent difference for DECT compared to pCT was -0.3% ± 1.1%, while for SECT the percent difference compared to pCT was 0.6% ± 3.0%. CONCLUSIONS: Fast kV-switching DECT obtained smaller RSP deviations from pCT compared to SECT in homogeneous tissue-equivalent phantom inserts. In heterogeneous tissue samples, DECT maintained improved RSP accuracy compared to SECT.

Search for emerging jets in pp collisions at s=13TeV with the ATLAS experiment

(2026)

A search is presented for emerging jets using 140fb-1$$140~\textrm{fb}^{-1}$$ of proton–proton collision data at s=13TeV$$\sqrt{s} = 13~\textrm{TeV}$$, collected by the ATLAS experiment between 2015 and 2018. The search looks for the existence of a dark sector with symmetries similar to those in quantum chromodynamics. This dark sector is populated with dark quarks, which undergo showering similar to quarks in the Standard Model, leading to a high multiplicity of long-lived dark hadrons within a dark jet. These dark hadrons subsequently decay to Standard Model particles via a new heavy scalar mediating particle ϕ$$\phi $$. This results in jets which contain multiple displaced vertices, known as emerging jets. This analysis targets four-jet topologies, with two emerging jets and two Standard Model jets, resulting from the decay of pair-produced scalar mediators. No significant excess above the Standard Model background is observed. For dark pion proper decay lengths of 20mm$$20~\textrm{mm}$$, mediator masses are excluded between 1 and 2TeV$$2~\textrm{TeV}$$ assuming a dark pion mass of 20GeV$$20~\textrm{GeV}$$.

Combination of Measurements of CP Properties of Higgs Boson Interactions with Vector Bosons Using Proton-Proton Collisions at s=13 TeV with the ATLAS Detector

(2026)

A combination of measurements of the CP properties of Higgs boson interactions with electroweak gauge bosons is presented, using 140  fb^{-1} of proton-proton collisions at sqrt[s]=13  TeV recorded by the ATLAS detector. Results from vector boson fusion H→ττ/WW^{*}/γγ, inclusive H→ZZ^{*}, and WH,H→bb[over ¯] channels are combined. No evidence of CP violation is observed, and constrains on the CP-violating operators in the Standard Model effective field theory framework (SMEFT) are set in the Warsaw basis. The results from the combination improve by over 40% on previous individual limits on c_{HW[over ˜]} and, for the first time, simultaneous constraints on three coefficients c_{HW[over ˜]}, c_{HB[over ˜]}, and c_{HW[over ˜]B} are set. These limits are the most stringent constraints to date on the relevant Wilson coefficients in the SMEFT framework with minimum model dependence.

Search for long-lived particles using displaced vertices of oppositely charged leptons in 140 fb − 1 of pp collisions at s = 13 TeV with the ATLAS detector

(2026)

A search is presented for long-lived particles decaying into an oppositely charged lepton pair, μ + μ − , e + e − , or e  ±  μ ∓, that form a vertex within the inner tracking system of the ATLAS detector at the Large Hadron Collider, displaced from the primary proton–proton interaction region. The analysis uses the 140 fb − 1 of Run-2 data collected at s = 13 TeV by the ATLAS experiment in 2015–2018. The results of the analysis are interpreted in the context of three benchmark models covering masses from 0.1 to 2.2 TeV and a range of mean proper lifetimes times the speed of light from 1 to 10 000 mm. The first model is a generic Z′ boson pair-produced by a new heavy scalar, with the Z′ decaying into lepton pairs. The remaining two models are R-parity violating supersymmetric models in which the lightest neutralino χ ˜ 1 0 decays into ℓ + ℓ ′ − ν ( ℓ , ℓ ′ = e , μ). The models differ by the mode of production of the χ ˜ 1 0 , which can be produced via the decay of pairs of gluinos or of pairs of charginos and neutralinos ( χ ˜ 1 ± χ ˜ 1 0 , χ ˜ 1 ± χ ˜ 2 0 , or χ ˜ 2 0 χ ˜ 1 0 ). Although each benchmark sample includes pair-produced LLPs, only a single vertex is required to be reconstructed. No dilepton displaced vertex candidate is observed and the results are presented as upper limits on the production cross-sections. This analysis sets leading limits on the production cross-sections for multiple models, including parameter space that has never been directly probed.

Search for massive, long-lived particles in events with displaced vertices and displaced muons in pp collisions at s = 13.6 TeV with the ATLAS experiment

(2026)

A search is presented for massive long-lived particles in events featuring at least one displaced vertex and at least one displaced muon, using proton–proton collision data collected by the ATLAS detector at the Large Hadron Collider from 2022 to 2024 at a centre-of-mass energy of 13.6 TeV. The data sample corresponds to an integrated luminosity of 164 fb − 1 . The analysis targets scenarios in which long-lived particles decay inside the ATLAS inner detector, resulting in a topology of at least one massive, displaced vertex (DV) with multiple associated tracks, and at least one muon with a large transverse impact parameter relative to the primary interaction point. The muon is not required to be associated with the DV. Two signal regions are defined by the transverse distance of the reconstructed DV from the interaction point. Background contributions are estimated by using fully data-driven techniques. No significant excess above the expected background is observed. Upper limits at 95% confidence level are set on the visible cross-section and on the production cross-sections of several benchmark models of R-parity-violating supersymmetry.

Search for electroweak tt¯Wj production in multileptonic final states at s=13 TeV with the ATLAS detector and bounds on effective field theory operators

(2026)

A search is presented for the electroweak production of a top-quark pair in association with a boson and at least one additional jet known as the process. This process has embedded within it a -scattering vertex, which is probed directly for the first time. The collision data were collected with the ATLAS detector during Run 2 of the LHC and correspond to an integrated luminosity of at . The search uses same-charge pairs of electrons and muons together with jets, of which at least one is -tagged. The properties of the most forward jet relative to the rest of the event are used to discriminate the electroweak production process from its strong production counterpart. A measured (expected) 95% CL upper limit on the cross section is set at (230 fb), to be compared with the expected Standard Model (SM) cross section of 47.7 fb. Limits are set on the SM effective field theory (EFT) operators and , which modify the electroweak couplings of the top quark through contributions to the -scattering vertex. The interpretation acts as a case study to emphasize the importance of energy-dependent sensitivity, multiprocess, and multioperator EFT contributions.

Cover page of Search for dimuon resonance in the 35 to 75 GeV mass range using 140 fb−1 of 13 TeV pp collisions with the ATLAS detector

Search for dimuon resonance in the 35 to 75 GeV mass range using 140 fb−1 of 13 TeV pp collisions with the ATLAS detector

(2026)

A model-independent search for low-mass resonances decaying into pairs of oppositely charged muons is presented. The analysis uses proton-proton collision data corresponding to an integrated luminosity of 140 fb−1, recorded by the ATLAS detector at the Large Hadron Collider between 2015 and 2018. The search targets hypothetical dimuon resonances in the invariant mass range from 35 GeV to 75 GeV. The modelling of this mass region is particularly challenging for conventional analytic background parameterisations. To address this, a Gaussian process regression technique is used to model the background. The dimuon mass spectrum is analysed for potential signals, and no statistically significant excess is observed. Upper limits at the 95% confidence level are set on the fiducial production cross-section of new resonances decaying promptly into muons, ranging from 20 fb to 110 fb, depending on the resonance mass. These results are further interpreted in the context of dark-photon and dark-matter-mediator models, leading to new constraints on their parameter spaces.

Cover page of Overview of the Theory of Extremely Correlated Fermi Liquids

Overview of the Theory of Extremely Correlated Fermi Liquids

(2026)

The Extremely Correlated Fermi Liquids (ECFL) theory is reviewed as a framework for understanding the $t$-$J$ model in metallic systems close to the Mott insulating limit. This overview presents the underlying ideas and the resulting equations in a form accessible to nonexperts. We compare theoretical results with all available resistivity data for single-layer High-T$_{c}$ systems, and with some spectral data. The highlighted results include a density dependent quasilinear T-dependence in resistivity, an unusually small quasiparticle weight, and distinct low-temperature emergent scales that dominate transport, thermodynamics and spectral properties of single-layer High T$_c$ systems. Suggestions are made for further experiments to probe the physics of these challenging quantum many-body systems.

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