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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Precision measurement of forward $\mathrm{Z}$ boson production in proton-proton collisions at $ \sqrt{s}$ = 13 TeV

A precision measurement of the Z boson production cross-section at $\sqrt{s}$ = 13 TeV in the forward region is presented, using pp collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb –1 The production cross-section is measured using $\mathrm{Z}$ →$μ^+μ^-$ events within the fiducial region defined as pseudorapidity 2.0 < η < 4.5 and transverse momentum p T > 20 GeV/c for both muons and dimuon invariant mass 60 , M $_{μμ}$ < 120 GeV/c 2 . The integrated cross-section is determined to be $σ(Z → μ^+μ^-)$ = 196.4 ± 0.2 ± 1.6 ± 3.9 pb, where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measured results are in agreement with theoretical predictions within uncertainties.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Measurements of W + W − production cross-sections in pp collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Measurements of W + W − → e ± νμ ∓ ν production cross-sections are presented, providing a test of the predictions of perturbative quantum chromodynamics and the electroweak theory. The measurements are based on data from pp collisions at $\sqrt{s}$ = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider in 2015–2018, corresponding to an integrated luminosity of 140 fb −1 . The number of events due to top-quark pair production, the largest background, is reduced by rejecting events containing jets with b-hadron decays. An improved methodology for estimating the remaining top-quark background enables a precise measurement of W + W − cross-sections with no additional requirements on jets. The fiducial W + W − cross-section is determined in a maximum-likelihood fit with an uncertainty of 3.1%. The measurement is extrapolated to the full phase space, resulting in a total W + W − cross-section of 127 ± 4 pb. Differential cross-sections are measured as a function of twelve observables that comprehensively describe the kinematics of W + W − events. The measurements are compared with state-of-the-art theory calculations and excellent agreement with predictions is observed. A charge asymmetry in the lepton rapidity is observed as a function of the dilepton invariant mass, in agreement with the Standard Model expectation. A CP-odd observable is measured to be consistent with no CP violation. Limits on Standard Model effective field theory Wilson coefficients in the Warsaw basis are obtained from the differential cross-sections.

Accelerator Physics↗
DOE OSTI2020

Z-boson production in p-Pb collisions at $ \sqrt{s_{\mathrm{NN}}} $ = 8.16 TeV and Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}} $ = 5.02 TeV

Measurement of Z-boson production in p-Pb collisions at $ \sqrt{s_{\mathrm{NN}}} $ = 8 . 16 TeV and Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}} $ = 5 . 02 TeV is reported. It is performed in the dimuon decay channel, through the detection of muons with pseudorapidity - 4 < η μ < - 2 . 5 and transverse momentum $ {p}_{\mathrm{T}}^{\mu } $ > 20 GeV/ c in the laboratory frame. The invariant yield and nuclear modification factor are measured for opposite-sign dimuons with invariant mass 60 < m μμ < 120 GeV/ c 2 and rapidity 2 . 5 < $ {y}_{\mathrm{cms}}^{\mu \mu} $ < 4. They are presented as a function of rapidity and, for the Pb-Pb collisions, of centrality as well. The results are compared with theoretical calculations, both with and without nuclear modifications to the Parton Distribution Functions (PDFs). In p-Pb collisions the center-of-mass frame is boosted with respect to the laboratory frame, and the measurements cover the backward ( - 4 . 46 < $ {y}_{\mathrm{cms}}^{\mu \mu} $ < - 2 . 96) and forward (2 . 03 < $ {y}_{\mathrm{cms}}^{\mu \mu} $ < 3 . 53) rapidity regions. For the p-Pb collisions, the results are consistent within experimental and theoretical uncertainties with calculations that include both free-nucleon and nuclear-modified PDFs. For the Pb-Pb collisions, a 3 . 4 σ deviation is seen in the integrated yield between the data and calculations based on the free-nucleon PDFs, while good agreement is found once nuclear modifications are considered.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of branching fractions of ${\Lambda}_{\textrm{c}}^{+}$ decays to Σ⁺K⁺K⁻, Σ⁺Φ and Σ⁺K⁺π⁻(π 0 )

Based on 4.5 fb - 1 data taken at seven center-of-mass energies ranging from 4.600 to 4.699 GeV with the BESIII detector at the BEPCII collider, we measure the branching fractions of \( {\Lambda}_c^{+} \) → Σ + + hadrons relative to \( {\Lambda}_c^{+} \) → Σ + π + π - . Combining with the world average branching fraction of \( {\Lambda}_c^{+} \) → Σ + π + π - , their branching fractions are measured to be (0 . 377 ± 0 . 042 ± 0 . 020 ± 0 . 021)% for \( {\Lambda}_c^{+} \) → Σ + K + K - , (0 . 200 ± 0 . 023 ± 0 . 011 ± 0 . 011)% for \( {\Lambda}_c^{+} \) → Σ + K + π - , (0 . 414 ± 0 . 080 ± 0 . 030 ± 0 . 023)% for \( {\Lambda}_c^{+} \) → Σ + Φ and (0 . 197 ± 0 . 036 ± 0 . 009 ± 0 . 011)% for \( {\Lambda}_c^{+} \) → Σ + K + K - (non- Φ ). In all the above results, the first uncertainties are statistical, the second are systematic and the third are from external input of the branching fraction of \( {\Lambda}_c^{+} \) → Σ + π + π - . Since no signal for \( {\Lambda}_c^{+} \) → Σ + K + π - π 0 is observed, the upper limit of its branching fraction is determined to be 0.13% at the 90% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Evidence of pair production of longitudinally polarised vector bosons and study of CP properties in ZZ → 4ℓ events with the ATLAS detector at $ \sqrt{s} $ = 13 TeV

A study of the polarisation and CP properties in ZZ production is presented. The used data set corresponds to an integrated luminosity of 140 fb –1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The ZZ candidate events are reconstructed using two same-flavour opposite-charge electron or muon pairs. The production of two longitudinally polarised Z bosons is measured with a significance of 4.3 standard deviations, and its cross-section is measured in a fiducial phase space to be 2.45 ± 0.60 fb, consistent with the next-to-leading-order Standard Model prediction. The inclusive differential cross-section as a function of a CP-sensitive angular observable is also measured. The results are used to constrain anomalous CP-odd neutral triple gauge couplings.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurement of the effective leptonic weak mixing angle

Using pp collision data at $\sqrt{s}$ = 13 TeV, recorded by the LHCb experiment between 2016 and 2018 and corresponding to an integrated luminosity of 5.4 fb −1 , the forward-backward asymmetry in the pp → Z/γ* → μ + μ − process is measured. The measurement is carried out in ten intervals of the difference between the muon pseudorapidities, within a fiducial region covering dimuon masses between 66 and 116 GeV, muon pseudorapidities between 2.0 and 4.5 and muon transverse momenta above 20 GeV. These forward-backward asymmetries are compared with predictions, at next-to-leading order in the strong and electroweak couplings. The measured effective leptonic weak mixing angle is ${\sin}^2{\theta}_{\textrm{eff}}^{\ell }=0.23147\pm 0.00044\pm 0.00005\pm 0.00023,$ where the first uncertainty is statistical, the second arises from systematic uncertainties associated with the asymmetry measurement, and the third arises from uncertainties in the fit model used to extract ${\sin}^2{\theta}_{\textrm{eff}}^{\ell }$ from the asymmetry measurement. This result is based on an arithmetic average of results using the CT18, MSHT20, and NNPDF31 parameterisations of the proton internal structure, and is consistent with previous measurements and with predictions from the global electroweak fit.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Resonance contributions to radiative corrections in charged-current elastic (anti)neutrino-nucleon scattering at GeV energies

We present the first evaluation of virtual resonance contributions to the charged-current elastic (anti)neutrino-nucleon scattering at GeV energies, focusing on the dominant Δ(1232) resonance. We approximate the vector part of the N → Δ transition by the leading magnetic dipole term. Our results for the cross-section corrections at fixed neutrino energy indicate the permille-level contribution of resonance intermediate states to the elastic and radiative scattering cross sections. This calculation exhibits the expected infrared behavior of the invariant amplitudes and unpolarized cross sections. Our findings provide important insights into inelastic excitations in the charged-current elastic (anti)neutrino-nucleon scattering at GeV energies.

Electroweak interaction↗
DOE OSTI2025

Lepton flavor violation by three units

The conservation of lepton flavor is a prediction of the Standard Model and is still an excellent approximate symmetry despite our observation of neutrino oscillations. Lepton flavor violation by one or two units has been discussed for decades, with several dedicated experiments exploring the vast model landscape but no discoveries so far. Here, we explore operators and processes that violate at least one lepton flavor by three units and identify testable signatures. In the Standard Model effective field theory, such operators already arise at mass dimension 7 and can be tested through their contributions to Michel parameters in leptonic decays. True neutrinoless charged-lepton flavor violation arises at mass dimension 10 and can realistically only be seen in the tau decay channels 𝜏 → $𝑒⁢𝑒⁢𝑒⁢\bar{𝜇}⁢\bar{𝜇}$ or 𝜏 → $𝜇⁢𝜇⁢𝜇\bar{𝑒}\bar{𝑒}$, for example in Belle II. Testable rates for these tau decays require light new particles and subsequently predict an avalanche of remarkably clean but so-far unconstrained collider signatures.

Feynman diagrams↗
DOE OSTI2025

Weak-charge radius of 40 Ar: From CREX constraints to CE⁢𝜈⁢NS sensitivity

Despite significant theoretical efforts, the CREX-PREX dilemma remains unresolved, preventing the reliable prediction of neutron (or weak-charge) radii that, besides their intrinsic nuclear-structure interest, often serve to quantify the impact of nuclear uncertainties in searches for new physics. Coherent elastic neutrino-nucleus scattering is a clean and attractive portal to new physics, whose sensitivity may be impacted by such nuclear uncertainties. In this paper I use CREX as the basis, together with a strong calcium-argon correlation, to provide a robust baseline for the weak radius of 40 Ar : 𝑅$^{40}_{wk}$ = 3.452 ± 0.028 (stat) ± 0.022 (syst) fm. Here, the weak radius of argon is an observable, highly relevant to ongoing and future liquid-argon campaigns, that encodes the loss of coherence at small momentum transfers.

39 ≤ A ≤ 58↗
DOE OSTI2025

Beyond leading twist: 𝜌 meson decay constants and distribution amplitudes in a self-consistent light-front quark model

In this study, we present a comprehensive analysis of decay constants and chiral-even and chiral-odd distribution amplitudes (DAs) up to twist 4 for the 𝜌 meson in the standard light-front quark model (LFQM) based on the Bakamjian-Thomas (BT) construction. For the 𝜌 meson, which possesses both longitudinal (ℎ=0) and transverse (ℎ =±1) polarizations, two types of decay constants, 𝑓$^{∥}_{𝜌}$ and 𝑓$^{⊥}_{𝜌}$, arises accordingly. We demonstrate that these decay constants can be self-consistently extracted from both local (𝑧𝜇 =0) and nonlocal (𝑧𝜇 ≠0) matrix elements ⟨0⁢|$\overline{𝑞}$(𝑧)⁢Γ⁢𝑞⁡(−𝑧)|⁢𝜌⁡(𝑃,ℎ)⟩, with Γ=(𝛾 𝜇 ,𝜎 𝜇⁢𝜈 ,𝛾 𝜇 ⁢𝛾 5 ,𝟏), in a manner independent of current components, polarizations, and reference frames. In particular, we emphasize the role of nonlocal matrix elements involving axial-vector and scalar currents, where mixing between 𝑓$^{∥}_{𝜌}$ and 𝑓$^{⊥}_{𝜌}$ occurs. We show that this mixing is consistently resolved through the BT construction, ensuring the proper extraction of these decay constants.

Electroweak interaction↗
DOE OSTI2026

Quantum Monte Carlo calculation of 𝛿 NS in 10 C using an effective field theory approach

Here, we compute radiative corrections to the superallowed 𝛽 decay of 10 C in an effective field theory approach using nuclear matrix elements obtained from quantum Monte Carlo calculations. These corrections are an important ingredient in the extraction of the Cabibbo-Kobayashi-Masakawa quark mixing matrix element 𝑉 𝑢⁢𝑑 , and the role of this work is to illuminate the uncertainties arising from nuclear structure. Our results provide good agreement with both the traditional extraction of 𝑉 𝑢⁢𝑑 , as well as with a more recent evaluation performed using the no-core shell model and a dispersion formalism. The dominant uncertainty in this approach is the presence of two unknown low-energy constants that enter into the relevant nuclear matrix elements. Future determinations of these low-energy constants—either from QCD or modeling them with two nucleon amplitudes—would improve the precision of the extraction in this formalism.

beta decay↗
DOE OSTI2025

One- and two-body current contributions to lepton-nucleus scattering

Modeling lepton-nucleus scattering with the accuracy required to extract neutrino-oscillation parameters from long- and short-baseline experiments necessitates retaining most quantum-mechanical effects. One such effect is the interference between one- and two-body current operators in the transition currents, which has been known to enhance the cross sections, especially in transverse kinematics. Here, we incorporate such interference in the spectral function formalism, which combines relativistic currents and kinematics with an accurate description of the initial target state. Our analysis of lepton-scattering off 12 C demonstrates that interference effects appreciably enhance the transverse electromagnetic response functions and the flux-folded neutrino-nucleus cross section, in both cases, improving the agreement with experimental data. We discuss the impact on the neutrino-oscillation program and the determination of nucleon axial form factors.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Measurement of the 𝐷 0 →𝐾 − ⁢𝜋 + ⁢𝑒 + ⁢𝑒 − branching fraction and search for 𝐷 0 → 𝜋 + ⁢𝜋 − ⁢𝑒 + ⁢𝑒 − and 𝐷 0 →𝐾 + ⁢𝐾 − ⁢𝑒 + ⁢𝑒 − decays at Belle

We present a study of the rare charm meson decays 𝐷 0 →𝐾 + ⁢𝐾 − ⁢𝑒 + ⁢𝑒 − , 𝜋 + ⁢𝜋 − ⁢𝑒 + ⁢𝑒 − , and 𝐾 − ⁢𝜋 + ⁢𝑒 + ⁢𝑒 − using a 942 fb −1 dataset collected by the Belle detector at the KEKB asymmetric-energy 𝑒 + ⁢𝑒 − collider. We identify 𝐷 0 candidates via the charge of the pion from 𝐷* + →𝐷 0 ⁢𝜋 + decays and normalize the branching fractions to 𝐷 0 → 𝐾 − ⁢𝜋 + ⁢𝜋 − ⁢𝜋 + decays. The branching fraction for decay 𝐷 0 → 𝐾 − ⁢𝜋 + ⁢𝑒 + ⁢𝑒 − is measured to be (39.6 ± 4.5 (stat) ± 2.9 (syst)) × 10 −7 , with the dielectron mass in the 𝜌/𝜔 mass region 675 < 𝑚 𝑒⁢𝑒 < 875 MeV/⁢𝑐 2 . We also search for 𝐷 0 → ℎ − ⁡ℎ (′)+ ⁡𝑒 + ⁢𝑒 − (ℎ (′) = 𝐾, 𝜋) decays with the dielectron mass near the 𝜂 and 𝜙 resonances, and away from these resonances for the 𝐾 + ⁢𝐾 − ⁢𝑒 + ⁢𝑒 − and 𝜋 + ⁢𝜋 − ⁢𝑒 + ⁢𝑒 − modes. For these modes, we find no significant signals and set 90% confidence level upper limits on their branching fractions at the 𝒪⁡(10 −7 ) level.

branching fraction↗
DOE OSTI2021

Passive Low-Energy Nuclear-Recoil Detection with Color Centers

Crystal-damage events such as tracks and point defects have been used to record and detect radiation for a long time and recently they have been proposed as a means for dark-matter detection. Color centers can be read out optically and we propose a scheme based on selective plane illumination microscopy for micrometer-scale imaging of large volumes corresponding to kilogram mass detectors. This class of detectors would be passive and would operate at room temperature and we call this the passive low-energy optical color-center nuclear-recoil (PALEOCCENE) detection method. We apply these concepts to the detection of reactor neutrinos using coherent elastic neutrino nucleus scattering (CE ν NS). Crystal-damage formation energies are intrinsically on the order of 25 eV, resulting in similarly low nuclear-recoil thresholds. Furthermore, this would enable the observation of reactor-neutrino CE ν NS with detectors as small as 10 g. Additionally, a competitive search for spin-dependent dark-matter scattering down to a dark-matter mass of 0.3 GeV could be possible. Passive crystal detectors might also be attractive for nuclear-nonproliferation safeguards if used to monitor reactor power and to put limits on plutonium production. The passive nature and small footprint of the proposed detectors implies that these might fit well within accepted reactor-safeguards operations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Improved limits on Fierz interference using asymmetry measurements from the Ultracold Neutron Asymmetry (UCNA) experiment

The Ultracold Neutron Asymmetry (UCNA) experiment was designed to measure the β-decay asymmetry parameter, A 0 , for free neutron decay. In the experiment, polarized ultracold neutrons are transported into a decay trap, and their β-decay electrons are detected with ≈4π acceptance into two detector packages which provide position and energy reconstruction. The experiment also has sensitivity to b n , the Fierz interference term in the neutron β-decay rate. In this work, we determine bn from the energy dependence of A 0 using the data taken during the UCNA 2011–2013 run. In addition, we present the same type of analysis using the earlier 2010 A dataset. Furthermore, motivated by improved statistics and comparable systematic errors compared to the 2010 data-taking run, we present a new b n measurement using the weighted average of our asymmetry dataset fits, to obtain b n = 0.066 ± 0.041 stat ± 0.024 syst which corresponds to a limit of -0.012 < b n < 0.144 at the 90% confidence level.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Interference effects for 0 ν β β decay in the left-right symmetric model

Various mechanisms may contribute to neutrinoless double beta decay in the left-right symmetric model. The interference between these mechanisms also contribute to the overall decay rate. The analysis of the contributions of these interference terms is important for disentangling different mechanisms. Here, we study interference effects contributing to the decay rate for neutrinoless double-β decay in the left-right symmetric model. The numerical values for maximum interference for several nuclides are calculated. It is observed that, for most of the interference terms, the contribution is smaller than 20% for all the nuclei considered in the study. However, the interference between the mass mechanisms (light and heavy) and η mechanism is observed to be in the range 30%–50%. The variation of the interference effect with the Q values is also studied.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

K-shell internal conversion coefficient for M4 decay of the 30.8 keV isomer in 93 Nb

The 30.8 keV (1/2) – isomeric state in $^{93}_{41}$Nb decays by an M4 transition to the (9/2) + ground state. Here, we have measured the K-shell internal conversion coefficient α K for this transition in order to test the validity of current methods of calculation for a case with relatively low atomic number, low transition energy, and a high value of α K . Taking the fluorescence yield of niobium to be 0.751(4), we obtain α K = 2.56(9) × 10 4 , a result that agrees with the Dirac-Fock calculations that take into account the presence of a K vacancy in the final state, and disagrees by 1.7 standard deviations with calculations that ignore the vacancy. We also determine the energy of the isomeric state to be 30.760(5) keV, a fourfold improvement in precision over the currently accepted value.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗