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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Electroweak Symmetry Restoration and Radiation Amplitude Zeros

In high-energy collisions far above the electroweak scale, the effects of electroweak symmetry breaking are expected to become parametrically small 𝛿∼𝑀 𝑊 /𝐸. This defines the extent to which the electroweak gauge symmetry is restored: (i) the physics of the transverse gauge bosons and fermions is described by a massless theory in the unbroken phase; (ii) the longitudinal gauge bosons behave like the Goldstone bosons and join the Higgs boson to restore the unbroken O(4) symmetry in the original Higgs sector. Using the unique feature of the radiation amplitude zeros in gauge theory, we propose to study the electroweak symmetry restoration quantitatively by examining the processes for the gauge boson pair production 𝑊 ± ⁢𝛾,𝑊 ± ⁢𝑍, and 𝑊 ±⁢ 𝐻 at the LHC and muon colliders.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Model for the curvature response of the CDF II drift chamber

The CDF II experiment at the Fermilab Tevatron used a drift chamber to measure the momenta of charged particles. We present a model for the response of the drift chamber to the curvature of a charged particle's trajectory. Constraints on the model parameters are obtained from cosmic-ray data and from information published by CDF in the context of the W boson mass measurement. Implications for the calibration of the drift chamber measurement of momentum are discussed. The robustness of the CDF calibration procedure is demonstrated. The model provides a framework for the analysis of precision magnetic trackers of high-momentum particles. Published by the American Physical Society 2025

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Measurement of the inclusive isolated-photon production cross section in pp and Pb–Pb collisions at $\mathbf {\sqrt{\textit{s}_{NN }} = 5.02}$ TeV

The ALICE Collaboration at the CERN LHC has measured the inclusive production cross section of isolated photons at midrapidity as a function of the photon transverse momentum (p$^{γ}_{T}$), in Pb–Pb collisions in different centrality intervals, and in pp collisions, at centre-of-momentum energy per nucleon pair of $\sqrt{s_{NN}}$ = 5.02 TeV. The photon transverse momentum range is between 10–14 and 40–140 GeV/c, depending on the collision system and on the Pb–Pb centrality class. The result extends to lower p$^{γ}_{T}$ than previously published results by the ATLAS and CMS experiments at the same collision energy. The covered pseudorapidity range is |η γ | < 0.67. The isolation selection is based on a charged particle isolation momentum threshold p$^{iso, ch}_{T}$ GeV/c within a cone of radii R = 0.2 and 0.4. The nuclear modification factor is calculated and found to be consistent with unity in all centrality classes, and also consistent with the HG-PYTHIA model, which describes the event selection and geometry biases that affect the centrality determination in peripheral Pb–Pb collisions. The measurement is compared to next-to-leading order perturbative QCD calculations and to the measurements of isolated photons and Z 0 bosons from the CMS experiment, which are all found to be in agreement.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Improving resbos for the precision needs of the LHC

The resummation calculation (esos) is a widely used tool for the simulation of single vector boson production at colliders. In this work, we develop a significant improvement over the esos code by increasing the accuracy from NNLL + NLO to N 3 LL + NNLO and release the esos v2.0 code. Furthermore, we propose a new nonperturbative function that includes information about the rapidity of the system (IFY). The IFY functional form was fitted to data from fixed target experiments, the Tevatron, and the LHC. We find that the nonperturbative function has mild rapidity dependence based on the results of the fit. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Modelling and computational improvements to the simulation of single vector-boson plus jet processes for the ATLAS experiment

This paper presents updated Monte Carlo configurations used to model the production of single electroweak vector bosons (W, Z/γ$^{∗}$) in association with jets in proton-proton collisions for the ATLAS experiment at the Large Hadron Collider. Improvements pertaining to the electroweak input scheme, parton-shower splitting kernels and scale-setting scheme are shown for multi-jet merged configurations accurate to next-to-leading order in the strong and electroweak couplings. The computational resources required for these set-ups are assessed, and approximations are introduced resulting in a factor three reduction of the per-event CPU time without affecting the physics modelling performance. Continuous statistical enhancement techniques are introduced by ATLAS in order to populate low cross-section regions of phase space and are shown to match or exceed the generated effective luminosity. This, together with the lower per-event CPU time, results in a 50% reduction in the required computing resources compared to a legacy set-up previously used by the ATLAS collaboration. The set-ups described in this paper will be used for future ATLAS analyses and lay the foundation for the next generation of Monte Carlo predictions for single vector-boson plus jets production.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Study of the normalized transverse momentum distribution of W bosons produced in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV

We present a study of the normalized transverse momentum distribution of W bosons produced in $p\bar{p}$ collisions, using data corresponding to an integrated luminosity of 4.35 fb -1 collected with the D0 detector at the Fermilab Tevatron collider at $\sqrt{s}$ = 1.96 TeV. The measurement focuses on the transverse momentum region below 15 GeV, which is of special interest for electroweak precision measurements; it relies on the same detector calibration methods which were used for the precision measurement of the W boson mass. The measured distribution is compared to different QCD predictions and a procedure is given to allow the comparison of any further theoretical models to the D0 data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Evidence for Longitudinally Polarized 𝑊 Bosons in the Electroweak Production of Same-Sign 𝑊 Boson Pairs in Association with Two Jets in 𝑝⁢𝑝 Collisions at $\sqrt{𝑠}$ = 13 TeV with the ATLAS Detector

This Letter reports the first evidence of electroweak production of same-sign 𝑊 boson pairs where at least one of the 𝑊 bosons is longitudinally polarized and the most stringent constraint to date for the production of two longitudinally polarized same-sign 𝑊 bosons. The dataset used corresponds to an integrated luminosity of 140 fb −1 of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the ATLAS detector during run 2 of the Large Hadron Collider. The study is performed in final states including two same-sign leptons (electrons or muons), missing transverse momentum, and at least two jets with a large invariant mass and a large rapidity difference. Two independent fits are performed targeting the production of same-sign 𝑊 bosons with at least one, or two longitudinally polarized 𝑊 bosons. The observed (expected) significance of the production with at least one longitudinally polarized 𝑊 boson is 3.3 (4.0) standard deviations. An observed (expected) 95% confidence level upper limit of 0.45 (0.70) fb is reported on the fiducial production cross section of two longitudinally polarized same-sign 𝑊 bosons.

W & Z bosons↗
DOE OSTI2024

Search for singly produced vectorlike top partners in multilepton final states with 139 fb −1 of 𝑝⁢𝑝 collision data at √𝑠 =13 TeV with the ATLAS detector

A search for the single production of a vectorlike top partner (𝑇) with mass greater than 1 TeV decaying into a 𝑍 boson and a top quark is presented, using the full Run 2 dataset corresponding to 139 fb −1 of 𝑝⁢𝑝 collisions at √𝑠 =13 TeV, collected in 2015–2018 with the ATLAS detector at the Large Hadron Collider. The targeted final state is characterized by the presence of a pair of electrons or muons with opposite-sign charges which form a 𝑍-boson candidate, as well as by the presence of 𝑏-tagged jets and forward jets. Events with exactly two or at least three leptons are categorized into two independently optimized analysis channels. No significant excess above the background expectation is observed and the results from the two channels are statistically combined to set exclusion limits at 95% confidence level on the masses and couplings of 𝑇. The results are interpreted in several benchmark scenarios to set limits on the mass and universal coupling strength (𝜅) of the vectorlike quark. For singlet 𝑇 quarks, 𝜅 values between 0.22 and 0.64 are excluded for masses between 1000 and 1975 GeV. For 𝑇 quarks in the doublet scenario, where the production cross section is much lower, 𝜅 values between 0.54 and 0.88 are excluded for masses between 1000 and 1425 GeV.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Measurement of the production of a $W$ boson in association with a charmed hadron in $pp$ collisions at $\sqrt{s}$ = $\mathrm{13 TeV}$ with the ATLAS detector

The production of a $W$ boson in association with a single charm quark is studied using 140 fb –1 of $\sqrt{s}$ = $13$ $\mathrm{TeV}$ proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The charm quark is tagged by the presence of a charmed hadron reconstructed with a secondary-vertex fit. The $W$ boson is reconstructed from the decay to either an electron or a muon and the missing transverse momentum present in the event. The charmed mesons reconstructed are D + → K – π + π + and D *+ → D 0 π + → (K – π + ) π + and the charge conjugate decays in the fiducial regions where $p$ T ($e,μ$) > 30 GeV, |$η(e,μ)$| < 2.5, $p$ T (D (*) ) > 8 GeV, and |$η$(D (*) )| < 2.2. The integrated and normalized differential cross sections as a function of the pseudorapidity of the lepton from the $W$ boson decay, and of the transverse momentum of the charmed hadron, are extracted from the data using a profile likelihood fit. The measured total fiducial cross sections are ${σ}_{fid}^{OS – SS}$ (W – + D + ) = 50.2 ± 0.2 ${(stat)}_{–2.3}^{+2.4}$(syst) pb, ${σ}_{fid}^{OS – SS}$ (W + + D – ) = 48.5 ± 0.2 ${(stat)}_{–2.2}^{+2.3}$(syst) pb, ${σ}_{fid}^{OS – SS}$ (W – + D *+ ) = 51.1 ± 0.4 ${(stat)}_{–1.8}^{+1.9}$(syst) pb, ${σ}_{fid}^{OS – SS}$ (W + + D *– ) = 50.0 ± 0.4 ${(stat)}_{–1.8}^{+1.9}$(syst) pb. Results are compared with the predictions of next-to-leading-order quantum chromodynamics calculations performed using state-of-the-art parton distribution functions. Additionally, the ratio of charm to anticharm production cross sections is studied to probe the $s$-$\bar{s}$ quark asymmetry. The ratio is found to be ${R}_{c}^{±}$= 0.971 ± 0.006 (stat) ± 0.011 (syst). The ratio and cross-section measurements are consistent with the predictions obtained with parton distribution function sets that have a symmetric $s$-$\bar{s}$ sea, indicating that any $s$-$\bar{s}$ asymmetry in the Bjorken-x region relevant for this measurement is small.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

W$^+$W$^-$ boson pair production in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A measurement of the W+W- boson pair production cross section in proton-proton collisions at s=13 TeV is presented. The data used in this study are collected with the CMS detector at the CERN LHC and correspond to an integrated luminosity of 35.9 fb-1. The W+W- candidate events are selected by requiring two oppositely charged leptons (electrons or muons). Two methods for reducing background contributions are employed. In the first one, a sequence of requirements on kinematic quantities is applied allowing a measurement of the total production cross section, 117.6±6.8 pb, which agrees well with the theoretical prediction. Fiducial cross sections are also reported for events with zero or one jet, and the change in the zero-jet fiducial cross section with the jet transverse momentum threshold is measured. Normalized differential cross sections are reported within the fiducial region. A second method for suppressing background contributions employs two random forest classifiers. The analysis based on this method includes a measurement of the total production cross section and also a measurement of the normalized jet multiplicity distribution in W+W- events. Finally, a dilepton invariant mass distribution is used to probe for physics beyond the standard model in the context of an effective field theory, and constraints on the presence of dimension-6 operators are derived.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗