Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “standard model”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71

Bounds on Lorentz Violation Parameters in the DUNE Experiment

The Standard Model (SM) has been highly successful in describing fundamental interactions, yet phenomena like neutrino oscillations point to physics beyond its framework. Among the proposed extensions, Lorentz invariance violation (LIV) stands out as a compelling possibility. Long-baseline neutrino experiments such as DUNE, with its 1300 km baseline, offer a promising setting to test LIV effects with high precision. In this work, we evaluate DUNE s sensitivity to LIV by analyzing event rates and oscillation probabilities using the GLoBES framework. A custom implementation of LIV parameters was employed to derive bounds on the aa and cc matrices, identifying the parameter values that lead to a 10% deviation from the standard oscillation probability. Our results show partial agreement with previous studies for the aa parameters, while deviations in the cc parameters highlight the impact of differing methodologies and sensitivities. These findings reinforce the relevance of LIV searches and motivate further theoretical and experimental efforts in this direction.

Cruz, Thiago. [Tech. Fed. Parana U.]↗

Quasi-sterile neutrinos from dark sectors. Part I. BSM matter effects in neutrino oscillations and the short-baseline anomalies.

Quasi-sterile neutrinos are a natural consequence of dark sectors interacting with the Standard Model (SM) sector via neutrino- and vector-portals. Essentially, quasi-sterile neutrinos are light dark sector fermions with two generic properties: (i) they mix with the active neutrinos of the SM, and (ii) they are charged under a vector mediator that couples feebly to SM matter. Various interesting phenomenological consequences result from this class of particles. In this article, we investigate one such consequence: new, beyond the SM matter effects that can alter in-medium neutrino oscillations. In particular, for special windows of energy and matter densities, active neutrinos can resonantly oscillate into sterile neutrinos. We take advantage of this feature to build a quasi-sterile neutrino model that can explain the MiniBooNE and LSND anomalies, while remaining compatible with observations from long-baseline reactor- and accelerator-based neutrino experiments. This model is also likely compatible with the recent results reported by the MicroBooNE collaboration (albeit we cannot precisely quantify this claim due to a lack of information in MicroBooNE’s public data releases to date). Implications for solar neutrinos and $ν_e$ disappearance searches are also briefly discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Search for Supersymmetry with a Compressed Mass Spectrum in Events with a Soft $\tau$ Lepton, a Highly Energetic Jet, and Large Missing Transverse Momentum in Proton-Proton Collisions at $\sqrt{s}=$ TeV

The first search for supersymmetry in events with an experimental signature of one soft, hadronically decaying τ lepton, one energetic jet from initial-state radiation, and large transverse momentum imbalance is presented. These event signatures are consistent with direct or indirect production of scalar τ leptons (τ˜) in supersymmetric models that exhibit coannihilation between the τ˜ and the lightest neutralino (χ˜10), and that could generate the observed relic density of dark matter. The data correspond to an integrated luminosity of 77.2 fb-1 of proton-proton collisions at s=13 TeV collected with the CMS detector at the LHC in 2016 and 2017. The results are interpreted in a supersymmetric scenario with a small mass difference (Δm) between the chargino (χ˜1±) or next-to-lightest neutralino (χ˜20), and the χ˜10. The mass of the τ˜ is assumed to be the average of the χ˜1± and χ˜10 masses. The data are consistent with standard model background predictions. Upper limits at 95% confidence level are set on the sum of the χ˜1±, χ˜20, and τ˜ production cross sections for Δm(χ˜1±,χ˜10)=50 GeV, resulting in a lower limit of 290 GeV on the mass of the χ˜1±, which is the most stringent to date and surpasses the bounds from the LEP experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Search for Neutral Heavy Scalars in ttZ Events Using 13 TeV pp Collisions at CMS

This thesis presents a search for a heavy pseudoscalar particle, A, which decays into a lighterscalar, H, and a Z boson within the Two-Higgs-Doublet Model (2HDM). We focus on Zboson decays to leptons, with H decays into a t t ̄ pair. The search uses the Asimov dataset–a theoretical dataset generated to predict the expected results for discovery and exclusion based on conditions from proton-proton collisions at the LHC, atintegrated luminosity of 138f b−1, as recorded by the CMS detector. The analysis focuses on events with three charged leptons, two of which come from the Z boson decay and one from a top quark decay. The expected results suggest the search has high sensitivity, showing discovery potential across much of the 2HDM Type-II parameter space, with possible deviations from the Standard Model background exceeding 5σ significance. The search sets upper limits on the cross-section times branching ratio, assuming narrow particle widths, for A masses up to 2100 GeV and H masses up to 1900 GeV. The results are interpreted in the 2HDM Type-II framework to exclude certain regions of parameter space at the 95% confidence level as a function of particle masses and variables such as tanβ and cos(β−α). The findings highlight the potential reach implications of future search in this parameter region.

Rudrabhatla, Sahithi [Illinois U., Chicago]↗

Technical Report Series on Global Modeling and Data Assimilation: Filtering Techniques on a Stretched Grid General Circulation Model - Volume 16

This report documents the techniques used to filter quantities on a stretched grid general circulation model. Standard high-latitude filtering techniques (e.g., using an FFT (Fast Fourier Transformations) to decompose and filter unstable harmonics at selected latitudes) applied on a stretched grid are shown to produce significant distortions of the prognostic state when used to control instabilities near the pole. A new filtering technique is developed which accurately accounts for the non-uniform grid by computing the eigenvectors and eigenfrequencies associated with the stretching. A filter function, constructed to selectively damp those modes whose associated eigenfrequencies exceed some critical value, is used to construct a set of grid-spaced weights which are shown to effectively filter without distortion. Both offline and GCM (General Circulation Model) experiments are shown using the new filtering technique. Finally, a brief examination is also made on the impact of applying the Shapiro filter on the stretched grid.

Takacs, Lawrence L.↗

Applying Quantum Tomography to Hadronic Interactions

A proper description of inclusive reactions is expressed with density matrices. Quantum tomography reconstructs density matrices from experimental observables. We review recent work that applies quantum tomography to practical experimental data analysis. Almost all field-theoretic formalism and modeling used in a traditional approach is circumvented with great efficiency. Tomographically-determined density matrices can express information about quantum systems which cannot in principle be expressed with distributions defined by classical probability. Topics such as entanglement and von Neumann entropy can be accessed using the same natural language where they are defined. A deep relation exists between separability, as defined in quantum information science, and factorization, as defined in high energy physics. Factorization acquires a non-perturbative definition when expressed in terms of a conditional form of separability. An example illustrates how to go from data for momentum 4-vectors to a density matrix while bypassing almost all the formalism of the Standard Model.

Martens, J. C.↗

Neutrinoless double beta decay via light neutralinos in R-parity violating supersymmetry

We perform a study of neutrinoless double beta (0νββ) decay mediated by the lightest neutralino of arbitrary mass in the minimal supersymmetric Standard Model (MSSM) under the presence of R-parity violating trilinear interactions. In this scenario, the exchange of the lightest neutralino can result in 0νββ decay of either long-range or short-range behaviour, depending on the neutralino mass. Using nuclear matrix elements calculated in the interacting boson model, we use an interpolation between the long- and short-range behaviours with an approximate formula. The non-observation of 0νββ decay is then used to place constraints on the supersymmetry parameter space, compatible with constraints from collider experiments. We compare these constraints to bounds from pion decays, CKM unitarity and big bang nucleosynthesis.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Anatomy of the electroweak phase transition for dark sector induced baryogenesis

We investigate the electroweak phase transition patterns for a recently proposed baryogenesis model with CP violation originated in the dark sector. The model includes a complex scalar singlet-Higgs boson portal, a U(1) l gauge lepton symmetry with a Z ' gauge boson portal and a fermionic dark matter particle. We find a novel thermal history of the scalar sector, featuring a Z 2 breaking singlet vacuum in the early Universe driven by a dark Yukawa coupling, that induces a one-step strongly first order electroweak phase transition. We explore the parameter space that generates the observed matter-antimatter asymmetry and dark matter relic abundance, while being consistent with constraints from electric dipole moment, collider searches, and dark matter direct detection bounds. The complex singlet can be produced via the Higgs portal and decays into Standard Model particles after traveling a certain distance. We explore the reach for long-lived singlet scalars at the 13 TeV Large Hadron Collider with \( \mathcal{L} \) = 139 fb - 1 and show its impact on the parameter space of the model. Setting aside currently unresolved theoretical uncertainties, we estimate the gravitational wave signatures detectable at future observatories.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Long-exposure NuSTAR constraints on decaying dark matter in the Galactic halo

Here, we present two complementary NuSTAR x-ray searches for keV-scale dark matter decaying to monoenergetic photons in the Milky Way halo. In the first, we utilize the known intensity pattern of unfocused stray light across the detector planes—the dominant source of photons from diffuse sources—to separate astrophysical emission from internal instrument backgrounds using ~7- Ms/detector deep blank-sky exposures. In the second, we present an updated parametric model of the full NuSTAR instrument background, allowing us to leverage the statistical power of an independent ~20-Ms/detector stacked exposures spread across the sky. Finding no evidence of anomalous x-ray lines using either method, we set limits on the active-sterile mixing angle sin 2 ⁡(2⁢θ) for sterile-neutrino masses 6–40 keV. The first key result is that we strongly disfavor a ~7-keV sterile neutrino decaying into a 3.5-keV photon. The second is that we derive leading limits on sterile neutrinos with masses ~15–18 keV and ~25–40 keV, reaching or extending below the big bang nucleosynthesis limit. In combination with previous results, the parameter space for the neutrino minimal standard model is now nearly closed.

79 ASTRONOMY AND ASTROPHYSICS↗

Leveraging intermediate resonances to probe CP violation at colliders

We explore the phenomenological impact of interference in tree-level contributions to three-body final states in $2\rightarrow 3$ scattering processes. This work introduces a novel search strategy leveraging asymmetries to enable sensitivity to CP-violating effects in less well-explored regions of phase space. Analytically, we demonstrate the effectiveness of this observable in probing interference between Standard Model charged-current decays and effective left-handed vector interactions, illustrated in a toy model featuring a scalar leptoquark, $S_1 \sim (3, 1, -\,1/3)$. Numerically, we apply this framework to studying the process $pp\rightarrow b \tau \nu $; unlike traditional high-$p_T$ searches or “bump hunts”, this approach utilizes an intermediate energy regime – where new physics is neither light enough to be produced on shell or heavy enough to justify an effective field theory treatment. A proof-of-principle analysis at parton level demonstrates a percent-level asymmetry, with sensitivity also to BSM weak-CP phase. While the specific phase sensitivity is diminished at particle level due to showering and detector effects, a machine learning classifier can recover sensitively to the presence of SM-BSM interference, significantly outperforming standard analysis methods. Notably discrimination between BSM signal and SM background could be achieved at the 2$\sigma $ level for the current LHC dataset and 8$\sigma $ at the High-Luminosity LHC. Moreover, this asymmetry observable as defined can also be more broadly applied to other searches for CP-violation in $2\rightarrow 3$ processes in present and future collider environments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Probing the Neutrino-Mass Scale with the KATRIN Experiment

The absolute mass scale of neutrinos is an intriguing open question in contemporary physics. The as-yet-unknown mass of the lightest and, at the same time, most abundant massive elementary particle species bears fundamental relevance to theoretical particle physics, astrophysics, and cosmology. The most model-independent experimental approach consists of precision measurements of the kinematics of weak decays, notably tritium β decay. With the KATRIN experiment, this direct neutrino-mass measurement has entered the sub-eV domain, recently pushing the upper limit on the electron-based neutrino mass down to 0.8 eV (90% CL) on the basis of first-year data out of ongoing, multiyear operations. Here, we review the experimental apparatus of KATRIN, the progress of data taking, and initial results. While KATRIN is heading toward the target sensitivity of 0.2 eV, other scientific goals are pursued. We discuss the search for light sterile neutrinos and an outlook on future keV-scale sterile-neutrino searches as well as further physics opportunities beyond the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

RLC4CLR (Reinforcement Learning Controller for Critical Load Restoration Problems)

RLC4CLR demonstrates using a reinforcement learning controller (RLC) to solve a critical load restoration (CLR) problem, which improves the grid resilience after a substation outage event. RLC4CLR consists of two parts. (1) RL environment: This environment encapsulates the CLR problem to be solved and provides interfacing functions to follow the standard OpenAI Gym format. A power system simulator, i.e., OpenDSS, is included to provide the power flow solution. Controller inputs and outputs (RL state and action) as well as the reward are defined in this environment as well. In summary, the RL environment is the problem formulation from which the RL agent can learn. (2) RL training script: The training script enables the RL agent to learn its control policy by interacting with the RL environment. For RL training, an open-sourced RL library, i.e., RLlib, is leveraged which is based on a distributed computing framework (Ray). The training script is designed to be able to be run on both local machine or the NREL HPC system. Other components of RLC4CLR include input data, e.g., grid model (standard IEEE test feeders), and other files used for results analysis.

Zhang, Xiangyu↗

Detecting Heavy Neutral SUSY Higgs Bosons Decaying to Sparticles at the High-Luminosity LHC

In supersymmetry (SUSY) models with low electroweak naturalness (natSUSY), which have been suggested to be the most likely version of SUSY to emerge from the string landscape, higgsinos are expected at the few hundred GeV scale, whilst electroweak gauginos inhabit the TeV scale. For TeV-scale heavy neutral SUSY Higgs bosons H and A, as currently required by LHC searches, the dominant decay modes of H,A are gaugino plus higgsino provided these decays are kinematically open. The light higgsinos decay to soft particles, so are largely invisible, whilst the gauginos decay to W, Z or h plus missing transverse energy (ET). Thus, we examine the viability of H,A→W+ET, Z+ET and h+ET signatures at the high luminosity LHC (HL-LHC) in light of large standard model (SM) backgrounds from (mainly) tt¯, VV and Vh production (where V=W,Z). We also examine whether these signal channels can be enhanced over backgrounds by requiring the presence of an additional soft lepton from the decays of the light higgsinos. We find significant regions in the vicinity of mA∼1–2 TeV of the mA vs. tanβ plane, which can be probed at the high luminosity LHC, using these dominant signatures by HL-LHC at 5σ and at the 95% confidence level (CL).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Solar-System Tests of Gravitational Theories

We are engaged in testing gravitational theory, mainly using observations of objects in the solar system and mainly on the interplanetary scale. Our goal is either to detect departures from the standard model (general relativity) - if any exist within the level of sensitivity of our data - or to support this model by placing tighter bounds on any departure from it. For this project, we have analyzed a combination of observational data with our model of the solar system, including planetary radar ranging, lunar laser ranging, and spacecraft tracking, as well as pulsar timing and pulsar VLBI measurements. In the past year, we have added to our data, primarily lunar laser ranging measurements, but also supplementary data concerning the physical properties of solar-system objects, such as the solar quadrupole moment, planetary masses, and asteroid radii. Because the solar quadrupole moment contributes to the classical precession of planetary perihelia, but with a dependence on distance from the Sun that differs from that of the relativistic precession, it is possible to estimate effects simultaneously. However, our interest is mainly in the relativistic effect, and we find that imposing a constraint on the quadrupole moment from helioseismology studies, gives us a dramatic (about ten-fold) decrease in the standard error of our estimate of the relativistic component of the perihelion advance.

Shapiro, Irwin I.↗

Hot bottom burning in asymptotic giant branch stars and its effect on oxygen isotopic abundances

A self-consistent calculation of asymptotic giant branch (AGB) evolution was carried out, including nucleosynthesis at the base of the convective envelope (hot bottom burning). Hot bottom burning was found to occur for stars between approximately 4.5 and approximately 7 solar mass, producing envelopes with O-18/O-16 less than or equal to 10(exp -6) and 10(exp -3) approximately less than or equal O-17/O-16 approximately less than or equal to 10(exp -1). The O-17 abundance depends sensitively on the nuclear O-17-destruction rate; this rate is only loosely constrained by the requirement that first and second dredge-up models match O-isotope observations of red giant branch (RGB) stars (Boothroyd, Sackmann, & Wasserburg 1994). In some cases, high mass-loss rates can terminate hot bottom burning before further O-17 enrichment takes place or even before all O-18 is destroyed. These predictions are in accord with the very limited stellar observations of J type carbon stars on the AGB and with some of the circumstellar Al2O3 grains from meteorites. In contrast, precise data from a number of grains and data from most low-mass S and C AGB stars (approximately less than 1.7 solar mass) lie in a region of the O-18/O-16 versus O-17/O-16 diagram that is not accessible by first and second dredge-up or by hot bottom burning. We conclude that for AGB stars, the standard models of stellar evolution are not in accord with these observations. We surmise that an additional mixing mechanism must exist that transports material from the cool bottom of the stellar convective envelope to a depth at which O-18 is destroyed. This 'cool bottom processing' mechanism on the AGB is similar to extra mixing mechanisms proposed to explain the excess C-13 (and depleted C-12) observed in the earlier RGB stage of evolution and the large Li-7 depletion observed in low-mass main-sequence stars.

Boothroyd, Arnold I.↗

Particle Theory and Cosmology

This project covered theoretical studies in particle physics, particle astrophysics and cosmology, aiming to bridge theoretical models with observable phenomena. The central focus was on exploring innovative mechanisms that could simultaneously address several outstanding puzzles in these areas, including the nature of dark matter, the muon g-2 anomaly, the existence of topologically stable monopoles, the generation of observable gravitational waves from early universe phenomena and high energy cosmic rays. One of the major achievements of this project was the development of models that predict new physics accessible through current and forthcoming experimental setups, both in particle colliders and astrophysical observations. These models have been instrumental in proposing verifiable predictions concerning supersymmetric extensions, the dynamics of cosmic strings and monopoles, and the intricate processes underpinning baryogenesis and reheating post-inflation. In tackling the dark matter conundrum, the project proposed several candidates within extended frameworks, such as light Z' models, pseudo-Goldstone dark matter, and scenarios integrating dark matter with inflationary cosmology. Each model outlined pathways for detection through direct, indirect, and collider search strategies, marking significant strides in the hunt for dark matter. Another cornerstone of the project was the in-depth analysis of inflationary models compliant with the Trans-Planckian Censorship Conjecture, highlighting the compatibility of axion dark matter within such frameworks. This not only provided a coherent picture of early universe cosmology but also delineated clear experimental signatures. The exploration of grand unified theories yielded insights into the potential discovery of monopoles and novel particle configurations at energy scales accessible to current and future colliders. This endeavor expanded the predictive power of these theories, particularly in the context of proton decay and the properties of Higgs-portal dark matter. Throughout the project, significant emphasis was placed on ensuring the theoretical developments were grounded in experimental testability. This led to a series of publications across prestigious journals, each contributing to the vibrant discourse at the intersection of particle physics and cosmology. In summary, this project has elucidated pathways beyond the Standard Model that are ripe for exploration through both ongoing and upcoming experimental efforts. The comprehensive approach adopted herein not only enhances our understanding of the fundamental forces and constituents of the universe but also propels the field towards new frontiers in high-energy physics and cosmology.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Vector boson dark matter from trinification

We show how trinification models based on the gauge group SU(3) C x SU(3) L x SU(3) R realized near the TeV scale can provide naturally a variety of dark matter (DM) candidates. These models contain a discrete T parity which may remain unbroken even after spontaneous symmetry breaking. The lightest T-odd particle, which could be a fermion, a scalar, or a gauge boson, can constitute the dark matter of the universe. This framework naturally admits a doublet-singlet fermionic DM, a singlet scalar DM, or a vector boson DM. Here we develop the vector boson DM scenario wherein the DM couples off-diagonally with the usual fermions and vector-like fermions present in the theory. We show consistency of this framework with dark matter relic abundance and direct detection limits as well as LHC constraints. We derive upper limits of 900 GeV on the vector gauge boson DM mass and 4.5 TeV on the vector-like quark masses. We also show the consistency of spontaneous gauge symmetry breaking down to Standard Model times an extra U(1) while preserving the T-parity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Search for a Dark Photon and an Invisible Dark Higgs Boson in $μ^+ μ^–$ and Missing Energy Final States with the Belle II Experiment

The dark photon $\textit{A'}$ and the dark Higgs boson $\textit{h'}$ are hypothetical particles predicted in many dark sector models. We search for the simultaneous production of A' and h' in the dark Higgsstrahlung process $e^+e^– → A' h'$ with $A' → μ^+μ^–$ and $\textit{h'}$ invisible in electron-positron collisions at a center-of- mass energy of 10.58 GeV in data collected by the Belle II experiment in 2019. With an integrated luminosity of 8.34 fb –1 , we observe no evidence for signal. We obtain exclusion limits at 90% Bayesian credibility in the range of 1.7-5.0 fb on the cross section and in the range of 1.7 × 10 –8 -200 × 10 –8 on the effective coupling $ε^2 × α_D$ for the $\textit{A'}$ mass in the range of 4.0 GeV/$c^2 < M_{A'}$ < 9.7 GeV/$c^2$ and for the $\textit{h'}$ mass $M_{h'} < M_{A'}$, where $\textit{ε}$ is the mixing strength between the standard model and the dark photon and $α_D$ is the coupling of the dark photon to the dark Higgs boson. Our limits are the first in this mass range. Phtysuc

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗