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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 451 records · Page 25
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DOE OSTI2021

Search for singly and pair-produced leptoquarks coupling to third-generation fermions in proton-proton collisions at $ \sqrt{s}$=13 TeV

A search for leptoquarks produced singly and in pairs in proton-proton collisions is presented. We consider the leptoquark (LQ) to be a scalar particle of charge -1/3e coupling to a top quark plus a tau lepton ( t τ ) or a bottom quark plus a neutrino ( b ν ), or a vector particle of charge +2/3e, coupling to t ν or b τ . These choices are motivated by models that can explain a series of anomalies observed in the measurement of B meson decays. In this analysis the signatures t τ ν b and t τ ν are probed, using data recorded by the CMS experiment at the CERN LHC at s = 13 TeV and that correspond to an integrated luminosity of 137 fb -1 . These signatures have not been previously explored in a dedicated search. The data are found to be in agreement with the standard model prediction. Lower limits at 95% confidence level are set on the LQ mass in the range 0.98–1.73 TeV, depending on the LQ spin and its coupling λ to a lepton and a quark, and assuming equal couplings for the two LQ decay modes considered. These are the most stringent constraints to date on the existence of leptoquarks in this scenario.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Coupled-channel J − − meson resonances from lattice QCD

We extend an earlier calculation within lattice QCD of excited light meson resonances with J P C = 1 − − , 2 − − , 3 − − at the S U ( 3 ) flavor point in the representation, by considering the representation. In this case the resonances appear in coupled-channel amplitudes, which we determine, establishing the relative strength of pseudoscalar-pseudoscalar to pseudoscalar-vector decays. Combining the new octet results with the prior results for the singlet, we perform a plausible extrapolation to the physical quark mass, and compare to experimental ρ J ⋆ , K J ⋆ , ω J ⋆ and ϕ J ⋆ resonances. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for emerging jets in pp collisions at $\sqrt{s} = 13.6$ TeV with the ATLAS experiment

A search for emerging jets is presented using 51.8 fb −1 of proton–proton collision data at $\sqrt{s} = 13.6$ TeV, collected by the ATLAS experiment during 2022 and 2023. The search explores a hypothetical dark sector featuring ‘dark quarks’ that are charged under a confining gauge group and couple to the standard model (SM) via a new mediator particle. These dark quarks undergo showering and hadronisation within the dark sector, forming long-lived dark mesons that decay back into SM particles. This results in jets that contain multiple displaced vertices known as emerging jets. The analysis targets events with pairs of emerging jets, produced either through a vector mediator, Z′, in the s-channel, or a scalar mediator, Φ, in the t-channel. No significant excess over the SM background is observed. Assuming a dark pion proper decay length between 5 mm and 50 mm, Z′ mediator masses between 600 GeV and 2550 GeV are excluded for quark and dark quark coupling values of 0.01 and 0.1, respectively. For a quark dark-quark coupling of 0.1, Φ mediator masses between 600 GeV and 1375 GeV are excluded. These results represent the first direct search targeting emerging jet pair production via a Z′ mediator, as well as the first study of emerging jet production mediated by a scalar particle exchanged in the t-channel.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Beam Spin Asymmetry Measurements for Two Pion Photoproduction at CLAS

The overarching goal of this analysis, and many like it, is to develop our understanding of the strong force interactions within the nucleon by examining the nature of their excitation spectra. As the resonances of these spectra have very short lifetimes (tau = 1x10 -23 s) and often have very similar masses, it is often impossible to directly observe resonances in the excitation spectra of nucleons. Polarization observables allow us to study the resonances by looking at how they affect the spin state of final state particles. The beam asymmetry is a polarization observable that allows us to detect the sensitivity of these resonances, and other transition mechanisms, to the electric vector orientation of incident photons. Presented in this thesis are first measurements of the beam asymmetries in the resonant region for the reaction channel pgamma p --> p π + π - focusing on the intermediate mesonic states rho^0 and f^0, and the final state pions. The analysis used data from the g8b experiment undertaken at the Thomas Jefferson National Accelerator Facility (JLab), the first experiment at JLab to use a linearly polarized photon beam. Using the coherent Bremsstrahlung facility and the CLAS detector of Hall B at JLab allowed for many multi-channel reactions to be detected and the first measurements of many polarization observables including those presented here. A brief overview of the theoretical framework used to undertake this analysis is given, followed by a description of the experimental details of the facilities used, then a description of the calibration of the Bremsstrahlung tagging facility which the author undertook, and finally the analysis is presented and the resulting measurements.

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 OSTI2015

B -meson decay constants from 2 + 1 -flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

We calculate the B-meson decay constants f B , f B s , and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ≈ 0.11, 0.086 fm with unitary pion masses as light as M π ≈ 290 MeV; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also improve the lattice heavy-light current through O(α s a). We extrapolate our results to the physical light-quark masses and continuum using SU(2) heavy-meson chiral perturbation theory, and provide a complete systematic error budget. We obtain f B 0 = 199.5(12.6) MeV, f B + =195.6(14.9) MeV, f B s =235.4(12.2) MeV, f B s /f B 0 =1.197(50), and f B s /f B + =1.223(71), where the errors are statistical and total systematic added in quadrature. Finally, these results are in good agreement with other published results and provide an important independent cross-check of other three-flavor determinations of B-meson decay constants using staggered light quarks.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Weak η production off the nucleon

The weak η-meson production off the nucleon induced by (anti)neutrinos is studied at low and intermediate energies, the range of interest for several ongoing and future neutrino experiments. We consider Born diagrams and the excitation of N{sup *} (1535)S{sub 11} and N{sup *} (1650)S{sub 11} resonances. The vector part of the N-S{sub 11} transition form factors has been obtained from the MAID helicity amplitudes while the poorly known axial part is constrained with the help of the partial conservation of the axial current (PCAC) and assuming the pion-pole dominance of the pseudoscalar form factor.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Polarization effects in radiative decay of a polarized τ lepton

The polarization effects in the one-meson radiative decay of a polarized τ lepton, τ → π{sup −}γν{sub τ}, are investigated. The inner bremsstrahlung and structural amplitudes are taken into account. The asymmetry of the differential decay width caused by the τ-lepton polarization and the Stokes parameters of the emitted photon itself are calculated depending on the polarization of the decaying τ lepton. These physical quantities are estimated numerically for an arbitrary direction of the τ lepton polarization 3-vector in the rest frame. The vector and axial-vector form factors describing the structure-dependent part of the decay amplitude are determined using the chiral effective theory with resonances (RχT)

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Probing an MeV-scale scalar boson in association with a TeV-Scale top-quark partner at the LHC

Searches for new low-mass matter and mediator particles have actively been pursued at fixed target experiments and at e + e - colliders. It is challenging at the CERN LHC, but they have been searched for in Higgs boson decays and in B meson decays by the ATLAS and CMS Collaborations, as well as in a low transverse momentum phenomena from forward scattering processes (e.g., FASER). We propose a search for a new scalar particle in association with a heavy vector-like quark. We consider the scenario in which the top quark (t) couples to a light scalar φ' and a heavy vector-like top quark T. We examine single and pair production of T in pp collisions, resulting in a final state with a top quark that decays purely hadronically, a T which decays semileptonically (T → W + b → ℓ ν b), and a φ' that is very boosted and decays to a pair of collimated photons which can be identified as a merged photon system. The proposed search is expected to achieve a discovery reach with signal significance greater than 5σ (3σ) for m(T) as large as 1.8 (2) TeV and m(φ') as small as 1 MeV, assuming an integrated luminosity of 3000 fb -1 . This search can expand the reach of T, and demonstrates that the LHC can probe low-mass, MeV-scale particles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Exploring the hidden valley at MATHUSLA

Hidden valley models naturally predict numerous long-lived particles, the distinctive signatures of which would be compelling evidence for a hidden valley scenario. As these are typically low-energy particles, they pose a challenge in terms of passing energy triggers in traditional searches at the Large Hadron Collider. The MATHUSLA (MAssive Timing Hodoscope for Ultra-Stable neutraL pArticles) experiment is specifically designed for the purpose of detecting long-lived particles. It also has the capability of detecting lower energy particles relative to ATLAS and CMS. In this paper, we assess MATHUSLA's potential for effectively probing hidden valley models. As a benchmark, we assume the hidden valley sector communicates with Standard Model sectors via a heavy vector propagator that couples to Standard Model quarks as well as hidden valley quarks. We model the showering and hadronization in the hidden valley sector using PYTHIA and study the detector acceptance as a function of the hidden valley meson's lifetime. We find that MATHUSLA possesses significant capabilities to explore previously uncharted parameter space within hidden valley models.

Hidden sector↗
DOE OSTI2022

Study of the doubly charmed tetraquark $\mathrm{T}$ $^+_{cc}$

Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D 0 D 0 π + mass spectrum just below the D *+ D 0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar T$^{+}_{cc}$ tetraquark with a quark content of cc$\bar{u}\bar{d}$ and spin-parity quantum numbers J P = 1 + . Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D *+ mesons is consistent with the observed D 0 π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector T$^{+}_{cc}$ state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the T$^{+}_{cc}$ state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Measurement of beam asymmetry for π – Δ ++ photoproduction on the proton at E γ = 8.5 GeV

We report a measurement of the $\pi^-$ photoproduction beam asymmetry for the reaction $\vec{\gamma} p \rightarrow \pi^- \Delta^{++}$ using data from the GlueX experiment in the photon beam energy range 8.2--8.8 GeV. The asymmetry $\Sigma$ is measured as a function of four-momentum transfer $t$ to the $\Delta^{++}$ and compared to phenomenological models. We find that $\Sigma$ varies as a function of $t$: negative at smaller values and positive at higher values of $|t|$. The reaction can be described theoretically by $t$-channel particle exchange requiring pseudoscalar, vector, and tensor intermediaries. In particular, this reaction requires charge exchange, allowing us to probe pion exchange and the significance of higher-order corrections to one-pion exchange at low momentum transfer. Constraining production mechanisms of conventional mesons may aid in the search for and study of unconventional mesons. Furthermore, this is the first measurement of the process at this energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

A theory of R(D*, D) anomaly with right-handed currents

We present an ultraviolet complete theory for the R ( D * ) and R ( D ) anomaly in terms of a low mass W ± R gauge boson of a class of left-right symmetric models. These models, which are based on the gauge symmetry SU(3) c × SU(2) L × SU(2) R × U(1) B - L , utilize vector-like fermions to generate quark and lepton masses via a universal seesaw mechanism. A parity symmetric version as well as an asymmetric version are studied. A light sterile neutrino emerges naturally in this setup, which allows for new decay modes of B -meson via right-handed currents. We show that these models can explain R ( D * ) and R ( D ) anomaly while being consistent with LHC and LEP data as well as low energy flavor constraints arising from \( {K}_L-{K}_S,\kern0.5em {B}_{d,s}-{\overline{B}}_{d,s},\kern0.5em D-\overline{D} \) mixing, etc., but only for a limited range of the W R mass: 1.2 (1.8) TeV ≤ \( {M}_{W_R} \) ≤ 3 TeV for parity asymmetric (symmetric) Yukawa sectors. The ratio R ( D )/ R ( D * ) is predicted to be ≃ 1.16, which is the same as in the Standard Model. The light sterile neutrinos predicted by the model may be relevant for explaining the MiniBoone and LSND neutrino oscillation results. The parity symmetric version of the model provides a simple solution to the strong CP problem without relying on the axion. It also predicts an isospin singlet top partner with a mass M T = (1.5 - 2.5) TeV.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Large N-ightmare dark matter

A dark QCD sector is a relatively minimal extension of the Standard Model (SM) that admits Dark Matter (DM) candidates, but requires no portal to the visible sector beyond gravitational interactions: a "nightmare scenario" for DM detection. Here, we consider a secluded dark sector containing a single flavor of light, vector-like dark quark gauged under (N). In the large-N limit, this single-flavor theory becomes highly predictive, generating two DM candidates whose masses and dynamics are described by few parameters: a light quark-antiquark bound state, the dark analog of the η' meson, and a heavy bound state of N quarks, the dark analog of the Δ ++ baryon. We show that the latter may freeze-in with an abundance independent of the confinement scale, forming DM-like relics for N ≲ 10, while the former may generate DM via cannibalization and freeze-out. We study the interplay of this two-component DM system, and determine the characteristic ranges of the confinement scale, dark-visible sector temperature ratio, and N that admit non-excluded DM, once effects of self-interaction constraints and bounds on effective degrees of freedom at the BBN and CMB epochs are included.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Amplitude Analysis of $\omega\pi^0$ Photoproduction at GlueX

Excited meson states can often lie hidden within mass spectra beneath more dominant resonances, making it difficult to extract their physical properties. We can unveil these states through amplitude analysis, which disentangles the overlapping states via fits to their unique production and decay angular distributions. Understanding the light-meson spectrum is essential for confirming Lattice QCD predictions, especially in regards to the search for possible hybrid mesons. The Gluonic Excitation (GlueX) experiment at Jefferson Lab aids this search by studying the production of excited light mesons in $\gamma p$ interactions in the 8.2 - 8.8 GeV photon-beam energy range. We show in these proceedings preliminary results of an amplitude analysis of a large $\omega\pi^0$ dataset, concentrating on measuring the interference between the $b_1(1235)$ and an excited $J^{PC}=1^{--}$ vector resonance.

Scheuer, Kevin↗
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 OSTI2020

Light dark sectors through the Fermion portal

Pairs of Standard Model fermions form dimension-3 singlet operators that can couple to new dark sector states. This “fermion portal” is to be contrasted with the lower-dimensional Higgs, vector and neutrino singlet portals. We characterise its distinct phenomenology and place effective field theory bounds on this framework, focusing on the case of fermion portals to a pair of light dark sector fermions. We obtain current and projected limits on the dimension-6 effective operator scale from a variety of meson decay experiments, missing energy and long-lived particle searches at colliders, as well as astrophysical and cosmological bounds. The DarkEFT public code is made available for recasting these limits, which we illustrate with various examples including an integrated- out heavy dark photon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗