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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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DOE OSTI2023

Measurement of the CP properties of Higgs boson interactions with $\tau$-leptons with the ATLAS detector

A study of the charge conjugation and parity ($CP$) properties of the interaction between the Higgs boson and $\tau$-leptons is presented. The study is based on a measurement of $CP$-sensitive angular observables defined by the visible decay products of $\tau$-leptons produced in Higgs boson decays. The analysis uses 139 fb -1 of proton–proton collision data recorded at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV with the ATLAS detector at the Large Hadron Collider. Contributions from $\tau$-violating interactions between the Higgs boson and $\tau$-leptons are described by a single mixing angle parameter Φ $\tau$ in the generalised Yukawa interaction. Without constraining the $H$ $\rightarrow$ $\tau$$\tau$ signal strength to its expected value under the Standard Model hypothesis, the mixing angle Φ $\tau$ is measured to be 9° ± 16°, with an expected value of 0° ± 28° at the 68% confidence level. The pure $CP$-odd hypothesis is disfavoured at a level of 3.4 standard deviations. The results are compatible with the predictions for the Higgs boson in the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

A Study of Nuclear Recoil Backgrounds in Dark Matter Detectors

Despite the great success of the Standard Model of particle physics, a preponderance of astrophysical evidence suggests that it cannot explain most of the matter in the universe. This so-called dark matter has eluded direct detection, though many theoretical extensions to the Standard Model predict the existence of particles with a mass on the $1-1000$ GeV scale that interact only via the weak nuclear force. Particles in this class are referred to as Weakly Interacting Massive Particles (WIMPs), and their high masses and low scattering cross sections make them viable dark matter candidates. The rarity of WIMP-nucleus interactions makes them challenging to detect: any background can mask the signal they produce. Background rejection is therefore a major problem in dark matter detection. Many experiments greatly reduce their backgrounds by employing techniques to reject electron recoils. However, nuclear recoil backgrounds, which produce signals similar to what we expect from WIMPs, remain problematic. There are two primary sources of such backgrounds: surface backgrounds and neutron recoils. Surface backgrounds result from radioactivity on the inner surfaces of the detector sending recoiling nuclei into the detector. These backgrounds can be removed with fiducial cuts, at some cost to the experiment's exposure. In this dissertation we briefly discuss a novel technique for rejecting these events based on signals they make in the wavelength shifter coating on the inner surfaces of some detectors. Neutron recoils result from neutrons scattering from nuclei in the detector. These backgrounds may produce a signal identical to what we expect from WIMPs and are extensively discussed here. We additionally present a new tool for calculating ($\alpha$, n)yields in various materials. We introduce the concept of a neutron veto system designed to shield against, measure, and provide an anti-coincidence veto signal for background neutrons. We discuss the research and development that informed the design of the DarkSide-50 boron-loaded liquid scintillator neutron veto. We describe the specific implementation of this veto system in DarkSide-50, including a description of its performance, and show that it can reject neutrons with a high enough e_ciency to allow DarkSide-50 to run background-free for three years.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Combined Dark Matter searches towards dwarf spheroidal galaxies with Fermi-LAT, HAWC, HESS, MAGIC and VERITAS

The search for Dark Matter (DM) has great potential to reveal physics beyond the Standard Model. As such, searches for evidence of DM particles are being carried out using a wide range of techniques, such as direct searches for DM particles, searches for DM produced with colliders, and indirect searches for the Standard Model annihilation products of DM. Dwarf spheroidal galaxies (dSphs) are excellent targets for indirect Dark Matter searches due to their relatively high DM content and negligible expected astrophysical background. A collaboration was formed to maximise the sensitivity of DM searches towards dSphs by combining for the first time dSph data from three imaging air Cherenkov telescope (IACT) arrays: HESS, MAGIC, and VERITAS; the Fermi-LAT satellite, and the water Cherenkov detector HAWC. Due to the diverse nature of the instruments involved, each experiment will analyse their individual datasets from multiple targets and then the results will be combined at the likelihood level. For consistency of the likelihoods across the five experiments, a common approach is used to treat the astrophysical factor (J-Factor) for each target and an agreed set of annihilation channels are considered. We also agree on a com- mon statistical approach and treatment of instrumental systematic uncertainties. The results are presented in terms of constraints on the velocity-weighted cross section for DM self-annihilation as a function of the DM particle mass.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Search for heavy resonances decaying into two Higgs bosons or into a Higgs boson and a W or Z boson in proton-proton collisions at 13 TeV

A search is presented for massive narrow resonances decaying either into two Higgs bosons, or into a Higgs boson and a W or Z boson. The decay channels considered are HH$\to \mathrm{b\overline{b}}\tau^{+}\tau^{-}$ and VH$ \to \mathrm{q\overline{q}}\tau^{+}\tau^{-}$, where H denotes the Higgs boson, and V denotes the W or Z boson. This analysis is based on a data sample of proton-proton collisions collected at a center-of-mass energy of 13 TeV by the CMS Collaboration, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. For the TeV-scale mass resonances considered, substructure techniques provide ways to differentiate among the hadronization products from vector boson decays to quarks, Higgs boson decays to bottom quarks, and quark- or gluon-induced jets. Reconstruction techniques are used that have been specifically optimized to select events in which the tau lepton pair is highly boosted. The observed data are consistent with standard model expectations and upper limits are set at 95% confidence level on the product of cross section and branching fraction for resonance masses between 0.9 and 4.0 TeV. Exclusion limits are set in the context of bulk radion and graviton models: spin-0 radion resonances are excluded below a mass of 2.7 TeV at 95% confidence level. In the spin-1 heavy vector triplet framework, mass-degenerate W' and Z' resonances with dominant couplings to the standard model gauge bosons are excluded below a mass of 2.8 TeV at 95% confidence level. There are the first limits for these decay channels at $\sqrt{s}=$ 13 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Measurements of Higgs bosons decaying to bottom quarks from vector boson fusion production with the ATLAS experiment at $\sqrt{s}=13\,\text {TeV}$

The paper presents a measurement of the Standard Model Higgs Boson decaying to b-quark pairs in the vector boson fusion (VBF) production mode. A sample corresponding to 126 fb –1 of √s = 13TeV proton–proton collision data, collected with the ATLAS experiment at the Large Hadron Collider, is analyzed utilizing an adversarial neural network for event classification. The signal strength, defined as the ratio of the measured signal yield to that predicted by the Standard Model for VBF Higgs production, is measured to be $0.95$ $^{+0.38}_{–0.36}$, corresponding to an observed (expected) significance of 2.6 (2.8) standard deviations from the background only hypothesis. The results are additionally combined with an analysis of Higgs bosons decaying to b-quarks, produced via VBF in association with a photon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Precision gamma-ray constraints for sub-GeV dark matter models

The indirect detection of dark matter particles with mass below the GeV scale has recently received significant attention. Future space-borne gamma-ray telescopes, including All-Sky-ASTROGAM, AMEGO, and GECCO, will probe the MeV gamma-ray sky with unprecedented precision, offering an exciting test of particle dark matter in the MeV-GeV mass range. While it is typically assumed that dark matter annihilates into only one Standard Model final state, this is not the case for realistic dark matter models. Here we analyze existing indirect detection constraints and the discovery reach of future detectors for the well-motivated Higgs and vector-portal models using our publicly-available code Hazma. In particular, we show how to leverage chiral perturbation theory to compute the dark matter self-annihilation cross sections into final states containing mesons, the strongly-interacting Standard Model dynamical degrees of freedom below the GeV scale. We find that future telescopes could probe dark matter self-annihilation cross sections orders of magnitude smaller than those presently constrained by cosmic microwave background, gamma-ray and terrestrial observations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for narrow resonances in dilepton mass spectra in proton-proton collisions at $\sqrt{s}$ = 13 TeV and combination with 8 TeV data

A search for narrow resonances in dielectron and dimuon invariant mass spectra has been performed using data obtained from proton-proton collisions at $ \sqrt{s} = $ 13 TeV collected with the CMS detector. The integrated luminosity for the dielectron sample is 2.7 fb$^{-1}$ and for the dimuon sample 2.9 fb$^{-1}$. The sensitivity of the search is increased by combining these data with a previously analysed set of data obtained at $ \sqrt{s} = $ 8 TeV and corresponding to a luminosity of 20 fb$^{-1}$. No evidence for non-standard-model physics is found, either in the 13 TeV data set alone, or in the combined data set. Upper limits on the product of production cross section and branching fraction have also been calculated in a model-independent manner to enable interpretation in models predicting a narrow dielectron or dimuon resonance structure. Limits are set on the masses of hypothetical particles that could appear in new-physics scenarios. For the $\mathrm{Z}'_{\text{SSM}}$ particle, which arises in the sequential standard model, and for the superstring inspired $\mathrm{Z}'_{\psi}$ particle, 95% confidence level lower mass limits for the combined data sets and combined channels are found to be 3.37 and 2.82 TeV, respectively. The corresponding limits for Kaluza-Klein gravitons arising in the Randall-Sundrum model of extra dimensions with coupling parameters 0.01 and 0.10 are 1.46 and 3.11 TeV, respectively. Lastly, these results significantly extend previous limits.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Study of $WW\gamma $ and $WZ\gamma $ production in $pp$ collisions at $\sqrt{s} = {8} \,{\text {TeV}}$ and search for anomalous quartic gauge couplings with the ATLAS experiment

This paper presents a study of WWγ and WZγ triboson production using events from proton–proton collisions at a centre-of-mass energy of √s = 8 TeV recorded with the ATLAS detector at the LHC and corresponding to an integrated luminosity of 20.2 fb –1 . The WWγ production cross-section is determined using a final state containing an electron, a muon, a photon, and neutrinos (eνμνγ). Upper limits on the production cross-section of the eνμνγ final state and the WWγ and WZγ final states containing an electron or a muon, two jets, a photon, and a neutrino (eνjjγ or μνjjγ) are also derived. The results are compared to the cross-sections predicted by the Standard Model at next-to-leading order in the strong-coupling constant. In addition, upper limits on the production cross-sections are derived in a fiducial region optimised for a search for new physics beyond the Standard Model. The results are interpreted in the context of anomalous quartic gauge couplings using an effective field theory. Confidence intervals at 95% confidence level are derived for the 14 coupling coefficients to which WWγ and WZγ production are sensitive.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Gravitational waves from first-order phase transition in a simple axion-like particle model

We consider a gauge-singlet complex scalar field Φ with a global U(1) symmetry that is spontaneously broken at some high energy scale ƒ a . As a result, the angular part of the Φ-field becomes an axion-like particle (ALP). We show that if the Φ-field has a nonzero coupling κ to the Standard Model Higgs boson, there exists a certain region in the (ƒ a , κ) parameter space where the global U(1) symmetry-breaking induces a strongly first order phase transition, thereby producing stochastic gravitational waves that are potentially observable in current and future gravitational-wave detectors. In particular, we find that future gravitational-wave experiments such as TianQin, BBO and Cosmic Explorer could probe a broad range of the energy scale 10 3 GeV ≳ ƒ a ≳ 108 GeV, independent of the ALP mass. Since all the ALP couplings to the Standard Model particles are proportional to inverse powers of the energy scale ƒ a (up to model-dependent O (1) coefficients), the gravitationalwave detection prospects are largely complementary to the current laboratory, astrophysical and cosmological probes of the ALP scenarios.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Search for top-squark pair production in final states with one lepton, jets, and missing transverse momentum using 36 fb − 1 of s = 13 TeV pp collision data with the ATLAS detector

CERN-LHC. The results of a search for the direct pair production of stops, the supersymmetric partner of the top-quark, in final states with one isolated electron or muon, several energetic jets, and missing transverse momentum are reported. The search uses data from pp collisions delivered by the Large Hadron Collider in 2015 and 2016 at a center-of-mass energy of 13 TeV and recorded by the ATLAS detector, corresponding to an integrated luminosity of 36.1/fb. A wide range of signal scenarios with different mass splittings between the stop, the lightest neutralino and possible intermediate gauginos or higgsinos is considered, including cases where the W-bosons or the top-quarks are off-shell. The analysis also targets the production of dark matter in association with a pair of top-quarks using the same final state. No significant excess over the Standard Model prediction is observed. The null results are used to set exclusion limits at 95% confidence level in several benchmark models, which reach up to a stop mass of 940 GeV. Stringent exclusion limits are also derived for all other considered stop decay scenarios, and upper limits are set on the visible cross-section for processes beyond the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Study of direct photon production with heavy flavor jets in $p\overline{p}$ collisions at $\sqrt{s}=1.96$ TeV with DZero detector

In hadronic collisions, photons ($\gamma$) with high energies emerge unaltered from the hard parton-parton interaction and therefore provide a clean probe of the underlying hard-scattering dynamics. Photons produced in these interactions (called direct or prompt) in association with one or more bottom ($b$)-quark jets provide an important test of perturbative Quantum Chromodynamics (QCD) predictions at large hard-scattering scales $Q$ and over a wide range of parton momentum fractions. In addition, the study of these processes also provides information about the parton density functions of $b$ quarks and gluons ($g$), which still have substantial uncertainties. In $p\bar{p}$ collisions, \gb-jet events are produced primarily through the Compton process $gb\to \gamma b$, which dominates for low and moderate photon transverse momenta ($\Ptg$), and through quark-antiquark anni hilation followed by $g \to b\bar{b}$ gluon splitting $q\bar{q}\to \gamma g \to \gamma b\bar{b}$, which dominates at high $\Ptg$. The final state with $b$-quark pair production, $p\bar{p} \rightarrow \gamma+b\bar{b}$, is mainly produced via $q\bar{q}\to \gamma b\bar{b}$ and $gg\to \gamma b\bar{b}$ scatterings. The $\gamma+2~b$-jet process is a crucial component of background in measurements of, for example, $t\bar{t} \gamma$ coupling and in some searches for new phenomena.\\ This thesis presents the first measurements of the differential cross section ${\rm d}\sigma/{\rm d}\Ptg$ for the production of an isolated photon in association with at least two $b$-quark jets. The ratio of differential production cross sections for $\gamma+2~b$-jets to $\gamma+b$-jet as a function of \ptg is also presented. The measurement of the ratio of cross sections leads to cancellation of various experimental and theoretical uncertainties, allowing a more precise comparison with the theoretical predictions. The results are based on the proton-antiproton ! collision data corresponding to an integrated luminosity of $8.7$~fb$^{-1}$ at $\sqrt{s}=$1.96~\TeV collected with the \DO detector at the Fermilab Tevatron Collider. %In this measurement, we follow an inclusive approach by allowing the final state with any additional jet(s) on top of the studied $b$-quark jets. Inclusive $\gamma+2~b$-jet production may also originate from partonic subprocesses involving parton fragmentation into a photon. However, photon isolation requirements significantly reduces the contributions from such processes. The large data sample and use of advanced photon and $b$-jet identification tools enable us to measure the $\gamma+2~b$-jet production cross section differentially as a function of $\Ptg$. This allows for probing the dynamics of the production process over a wide kinematic range not studied before in other measurements of a vector boson + $b$-jet final state. The measured cross sections and their ratios are compared to the NLO perturbative Q CD calculations as well as predictions based on the $k_{\rm T}$-factorization approach and those from the {\sc sherpa} and {\sc pythia} Monte Carlo event generators. We also measure the ratio of cross sections, $\sigma(p\bar{p}\rightarrow Z+2~b~\text{jets})$/$\sigma(p\bar{p}\rightarrow Z+\text{2~jets})$, for associated production of a $Z$ boson with at least two jets. This measurement uses data corresponding to an integrated luminosity of 9.7 fb$^{-1}$ collected by the \DO experiment. The measured integrated ratio is in agreement with predictions from NLO perturbative QCD and the Monte Carlo event generators {\sc alpgen} and {\sc pythia}. A good theoretical description of this process is essential since it forms a major background for a variety of physics processes, including standard model Higgs boson production in association with a $Z$ boson, $ZH(H\rightarrow b\bar{b})$, and searches for supersymmetric partners of the $b$ quark. These results will improve our theoretical understanding as we search for phenomena beyond the standard! model us! ing the data from similar collider experiments in the case where the final states of the interaction involved the production of vector bosons in association with two $b$-quark jets.\\ This work has been done in collaboration with \DO experiment but the analyses and results presented in this thesis are my contribution.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

A cross-frontier quest to reveal the origin of the Universe [Slides]

The Standard Model is one of the most well-tested theories in Particle Physics. The particle content was completed by the discovery of the Higgs boson. However, it does not explain the complete picture. This report discusses physics beyond the Standard Model (BSM Physics).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Geometry of the scalar sector

The S-matrix of a quantum field theory is unchanged by field redefinitions, and so it only depends on geometric quantities such as the curvature of field space. Whether the Higgs multiplet transforms linearly or non-linearly under electroweak symmetry is a subtle question since one can make a coordinate change to convert a field that transforms linearly into one that transforms non-linearly. Renormalizability of the Standard Model (SM) does not depend on the choice of scalar fields or whether the scalar fields transform linearly or non-linearly under the gauge group, but only on the geometric requirement that the scalar field manifold M is flat. Standard Model Effective Field Theory (SMEFT) and Higgs Effective Field Theory (HEFT) have curved M, since they parametrize deviations from the flat SM case. We show that the HEFT Lagrangian can be written in SMEFT form if and only ifMhas a SU(2) L U(1) Y invariant fixed point. Experimental observables in HEFT depend on local geometric invariants of M such as sectional curvatures, which are of order 1/Λ 2 , where Λ is the EFT scale. We give explicit expressions for these quantities in terms of the structure constants for a general G → H symmetry breaking pattern. The one-loop radiative correction in HEFT is determined using a covariant expansion which preserves manifest invariance of M under coordinate redefinitions. The formula for the radiative correction is simple when written in terms of the curvature of M and the gauge curvature field strengths. We also extend the CCWZ formalism to non-compact groups, and generalize the HEFT curvature computation to the case of multiple singlet scalar fields.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for triple Higgs boson production in the 6⁢𝑏 final state using 𝑝⁢𝑝 collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search for the production of three Higgs bosons (𝐻⁡𝐻⁡𝐻) in the $b\bar{b}b\bar{b}b\bar{b}$ final state is presented. The search uses 126 fb −1 of proton-proton collision data at $\sqrt{s}$ =13 TeV collected with the ATLAS detector at the Large Hadron Collider. The analysis targets both nonresonant and resonant production of 𝐻⁡𝐻⁡𝐻. The resonant interpretations primarily consider a cascade decay topology of 𝑋 →𝑆⁢𝐻 → 𝐻⁡𝐻⁡𝐻 with masses of the new scalars 𝑋 and 𝑆 up to 1.5 and 1 TeV, respectively. In addition to scenarios where 𝑆 is off-shell, the nonresonant interpretation includes a search for Standard Model 𝐻⁡𝐻⁡𝐻 production, with limits on the trilinear and quartic Higgs self-coupling set. No evidence for 𝐻⁡𝐻⁡𝐻 production is observed. An upper limit of 59 fb is set, at the 95% confidence level, on the cross section for Standard Model 𝐻⁡𝐻⁡𝐻 production.

Artificial neural networks↗
DOE OSTI2025

Search for heavy neutral resonances decaying to tau lepton pairs in proton-proton collisions at $\sqrt{s}$=13 TeV

A search for heavy neutral gauge bosons (𝑍′) decaying into a pair of tau leptons is performed in proton-proton collisions at $\sqrt{s}$ =13 TeV at the CERN LHC. The data were collected with the CMS detector and correspond to an integrated luminosity of 138 fb −1 . The observations are found to be in agreement with the expectation from standard model processes. Limits at 95% confidence level are set on the product of the 𝑍′ production cross section and its branching fraction to tau lepton pairs for a range of 𝑍′ boson masses. For a narrow resonance in the sequential standard model scenario, a 𝑍′ boson with a mass below 3.5 TeV is excluded. This is the most stringent limit to date from this type of search.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for associated production of a Z boson with a single top quark and for tZ flavour-changing interactions in pp collisions at $ \sqrt{s}=8 $ TeV

A search for the production of a single top quark in association with a Z boson is presented, both to identify the expected standard model process and to search for flavour-changing neutral current interactions. The data sample corresponds to an integrated luminosity of 19.7 fb$^{−1}$ recorded by the CMS experiment at the LHC in proton-proton collisions at $ \sqrt{s}=8 $ TeV. Final states with three leptons (electrons or muons) and at least one jet are investigated. An events yield compatible with tZq standard model production is observed, and the corresponding cross section is measured to be σ(pp → tZq → ℓνbℓ$^{+}$ ℓ$^{−}$q) = 10$_{− 7}^{+ 8}$ fb with a significance of 2.4 standard deviations. No presence of flavour-changing neutral current production of tZq is observed. Exclusion limits at 95% confidence level on the branching fractions of a top quark decaying to a Z boson and an up or a charm quark are found to be ℬ(t → Zu) < 0.022% and ℬ(t → Zc) < 0.049%.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Constraints on fifth forces and ultralight dark matter from OSIRIS-REx target asteroid Bennu

It is important to test the possible existence of fifth forces, as ultralight bosons that would mediate these are predicted to exist in several well-motivated extensions of the Standard Model. Recent work indicated asteroids as promising probes, but applications to real data are lacking so far. Here we use the OSIRIS-REx mission and ground-based tracking data for the asteroid Bennu to derive constraints on fifth forces. Our limits are strongest for mediator masses m ~ (10 -18 -10 -17 ) eV, where we currently achieve the tightest bounds. These can be translated to a wide class of models leading to Yukawa-type fifth forces, and we demonstrate how they apply to U(1) B dark photons and baryon-coupled scalars. Our results demonstrate the potential of asteroid tracking in probing well-motivated extensions of the Standard Model and ultralight bosons near the fuzzy dark matter range.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

High-Sensitivity Nuclear-Structure Studies of Rare Isotopes and Few-Electron Systems

This final technical report presents the work that was completed during the award period for DE-SC0017649 related to the structure of nuclei for both astrophysics and tests of the Standard Model, namely: Using trapped bare (and few-electron) radioactive ions to probe the nature of elec- troweak decay modes under extreme conditions for structure and astrophysics, Providing experimental nuclear structure guidance to nuclear theory in systems relevant for testing the Standard Model, and Working with the HPGe sub-group of the FRIB decay station collaboration, which includes the technical development of a next-generation γ-ray spectrometer.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗