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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Proton Spin from Small-x With Constraints from the Valence Quark Model

We apply the valence quark model to constrain the non-perturbative initial condition for the small-x helicity evolution. The remaining free parameters are constrained by performing a global analysis to the available polarized small-x deep inelastic scattering data. A good description of the world data is obtained with only 8 free parameters. The model parameters are tightly constrained by the data, allowing us to predict the proton polarized structure-function to be negative at small x. Furthermore, we obtain the small-x quark and gluon spins, depending on the applied running coupling prescription.

Adamiak, Daniel [Thomas Jefferson National Acceler↗
DOE OSTI2025

Proton spin from small-x with constraints from the valence quark model

We apply the valence quark model [1] to constrain the non-perturbative initial condition for the small-x helicity evolution. The remaining free parameters are constrained by performing a global analysis akin to [2] to the available polarized small-x deep inelastic scattering data. A good description of the world data is obtained with only 8 free parameters. The model parameters are tightly constrained by the data, allowing us to predict the proton polarized structure function $g^p_1$ to be negative at small x. Furthermore, we obtain the small-x quark and gluon spins to give a contribution $\int^{0.1}_{10^{-5}} dx (\frac{1}{2}\Delta\Sigma + \Delta{G}) = 0.63 ± 0.10$ or $1.35 ± 0.16$ (or to the proton spin, depending on the applied running coupling prescription.

Color-class condensate↗
DOE OSTI2025

Bottomonium meson spectrum with quenched and unquenched quark models

An open question in hadronic phenomenology concerns the “unquenching” effects of higher Fock space components on the leading Fock space description of hadrons. Here, we address this by making a comparison of the bottomonium spectrum as computed with the relativized Godfrey–Isgur quark model and an unquenched coupled channel model driven by the “$^3P_0$” mechanism of hadronic decay. Our results show that both models can describe the spectrum well, indicating that the influence of coupled channel effects can be largely absorbed into the parameters of the quenched quark model. This conclusion is reinforced by a perturbative calculation that shows that the spin-dependence of mass splittings due to mixing with the continuum recapitulates quenched quark model spin-dependent interactions. We also show that softening of the quark-antiquark wavefunction due to continuum mixing improves the description of vector bottomonium decay constants. Together, these results illustrate and substantiate the surprising robustness of simple constituent quark model descriptions of hadrons.

Sultan, M. Atif [Nankai Univ., Tianjin (China); Un↗
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 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 OSTI2024

Beam energy dependence of net-hyperon yield and its implication on baryon transport mechanism

In the constituent quark model, each quark inside a baryon carries 1/3 unit of the baryon number. An alternative picture exists where the center of a Y-shaped topology of gluon fields, called the baryon junction, carries a unit baryon number. Studying baryon transport over a large rapidity gap (δy) in nuclear collisions provides a possible tool to distinguish these two pictures. A recent analysis of global data on net-proton yield at mid-rapidity in Au+Au collisions showed an exponential dependence on δy and the exponential slope does not vary with event centrality, favoring the baryon junction picture. Since junctions are flavor blind, hyperons – baryons containing valence strange quarks – are expected to exhibit a similar behavior as the proton. This study aims to test this prediction by analyzing hyperon yields in Au+Au collisions at various energies. We observe that net-hyperon yields, after correcting for the strangeness production suppression, adhere to the expected exponential form. The extracted slope parameters for net-Λ, net-$Ξ$ and net-Ω are consistent with each other and with those of net-proton within uncertainties, and exhibit no centrality dependence. Various implementations of the PYTHIA event generator, primarily based on valence quarks for baryon transport, are unable to simultaneously describe the slope parameters for all baryons.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

The impact of $γN$ and $γ^∗N$ interactions on our understanding of nucleon excitations

We review recent progress in our understanding of the nucleon excitation spectrum. Thanks to dedicated efforts at facilities such as ELSA, MAMI and Jefferson Lab, several new nucleon resonances have been discovered, and evidence for previously elusive states has been significantly improved. Numerous decay channels have been observed for the first time, and resonance properties are being extracted from these data by several groups through coupled-channel analyses of varying complexity. Electroproduction experiments have provided further insights into the internal structure of light baryon resonances – for example, the long-debated Roper resonance N (1440) is observed as a three-quark state with a significant meson-cloud component. While the non-relativistic quark model remains a valuable tool for organizing the spectrum of nucleon and Δ resonances, a variety of theoretical frameworks have emerged to offer deeper understanding, including phenomenological quark models, holographic QCD, functional methods, effective field theories, and lattice QCD. We examine the interplay between these approaches, highlight their respective strengths and explore how they complement each other in shaping our knowledge of light baryon resonances. We address several open questions in baryon spectroscopy, including the nature of the enigmatic Λ (1405), ongoing searches for exotic states such as hybrid baryons and pentaquarks, and the dichotomy between microscopic descriptions of baryons in terms of quarks and gluons versus effective hadronic descriptions based on meson-baryon dynamics.

Baryon resonances↗
DOE OSTI2025

PHOTOPRODUCTION OF np^0 BY DOUBLE-REGGE EXCHANGE

The GlueX experiment is a photoproduction experiment based at Jeferson Lab in Newport News, Virginia. A major aim of GlueX is to look for hybrid mesons, which are a quark and an anti-quark bound by an excited gluonic field that contributes to the quantum numbers. The reaction ¿p ¿ ¿e0p is of particular interest since ¿e is a potential decay mode of states with exotic quantum numbers JPC =1¿+, which are forbidden in the constituent quark model. Finding such a resonance would be a clear sign of non-quark model physics. In concert with the Joint Physics Analysis Center we have developed a model for double-Regge interactions in this channel. These non-resonant processes generate asymmetries in the distributions of decay angles, which could be falsely attributed to the interference between exotic odd partial waves and even partial waves. In previous searches for light exotics we have seen evidence for the necessity of accounting for the presence of these non-resonant productions. We present a double-Regge model for photoproduction of ¿e0 and the application of it by measuring the asymmetry of ¿e0 production in the double Regge limit, as well as a comparison of the measured results to current theoretical predictions.

Barsotti, Rebecca [Indiana Univ. Southeast, New Al↗
DOE OSTI2026

The Roper Resonance and Kin

The properties of the Roper resonance N(1440) 1/ 2 + are reviewed. Quark models have long struggled to reproduce its mass relative to its negative parity partner N(1535) 1/ 2 − . This discrepancy motivated interpretations of the Roper as a dynamically generated meson–baryon state. Including its isospin partners ∆(1600) 3/ 2 + and ∆(1700) 3/ 2 − further accentuates the tension between quark-model predictions and experiment. Recent develop ments based on AdS/QCD and functional methods achieve much improved agreement, identifying the Roper as an ordinary three-quark excitation. Electroproduction experiments at Jefferson Lab have now resolved this long-standing question, revealing the Roper as a qqq core dressed by a substantial meson cloud. The Roper resonance belongs to a family of four N ∗ states with J P = 1/ 2 + ; the highest-mass member, N(2100) 1/ 2 + , likely represents a Roper-like excitation in the fourth shell.

Burkert, Volker [Thomas Jefferson National Acceler↗
DOE OSTI2025

Quantum entanglement correlations in double quark PDFs

Methods from Quantum Information Theory are used to scrutinize quantum correlations encoded in the two-quark density matrix over light-cone momentum fractions x 1 and x 2 . A nonperturbative three quark model light-cone wavefunction predicts significant nonclassical correlations associated with the “entanglement negativity” measure for asymmetric and small quark momentum fractions. We perform one step of QCD scale evolution of the entire density matrix, not just its diagonal (dPDF), by computing collinearly divergent corrections due to the emission of a gluon. Finally, we present first qualitative numerical results for single-step scale evolution of quantum entanglement correlations in double quark PDFs. At a higher Q 2 scale, the nonclassical correlations manifest in the dPDF for nearly symmetric momentum fractions.

Entanglement in field theory↗
DOE OSTI2025

Noble dark matter: Surprising elusiveness of dark baryons

Dark matter could be a baryonic composite of stronglyc upled constituents transforming under SU⁡(2) 𝐿 . We classify the SU⁡(2) 𝐿 representations of baryons in a class of simple confining dark sectors and find that the lightest state can be a pure singlet or a singlet that mixes with other neutral components of SU⁡(2) 𝐿 representations, which strongly suppresses the dark matter candidate’s interactions with the Standard Model. We focus on models with a confining SU⁡(𝑁 𝑐 ) and heavy dark quarks constituting vectorlike 𝑁 𝑓 -plet of SU⁢(2) 𝐿 . For benchmark 𝑁 𝑐 and 𝑁 𝑓 , we calculate baryon mass spectra, incorporating electroweak gauge boson exchange in the nonrelativistic quark model, and demonstrate that above TeV mass scales, dark matter is dominantly a singlet state. The combination of this singlet nature with the recently discovered ℋ-parity results in an inert state analogous to noble gases, hence we coin the term noble dark matter. Our results can be understood in the nonrelativistic effective theory that treats the dark baryons as elementary states, where we find singlets accompanying triplets, 5-plets, or more exotic representations. This generalization of WIMP-like theories is more difficult to find or rule out than dark matter models that include only a single SU⁡(2) 𝐿 multiplet (such as a wino), motivating new searches in colliders and a reanalysis of direct and indirect detection prospects in astrophysical observations.

dark matter direct detection↗
DOE OSTI2025

Determination of the spin and parity of all-charm tetraquarks

The traditional quark model accounts for the existence of baryons, such as protons and neutrons, which consist of three quarks, as well as mesons, composed of a quark–antiquark pair. Only recently has substantial evidence started to accumulate for exotic states composed of four or five quarks and antiquarks. The exact nature of their internal structure remains uncertain. Here we report the first measurement of quantum numbers of the recently discovered family of three all-charm tetraquarks, using data collected by the CMS experiment at the Large Hadron Collider from 2016 to 2018 . The angular analysis techniques developed for the discovery and characterization of the Higgs boson have been applied to the new exotic states. Here we show that the quantum numbers for parity P and charge conjugation C symmetries are found to be +1. The spin J of these exotic states is determined to be consistent with 2ħ, while 0ħ and 1ħ are excluded at 95% and 99% confidence levels, respectively. The J PC = 2 ++ assignment implies particular configurations of constituent spins and orbital angular momenta, which constrain the possible internal structure of these tetraquarks.

Physics↗
DOE OSTI2025

Exploring Photoproduced $\eta^{(}{'^{)}} \pi^{0}$ Systems in the Search for Exotic Hadrons at GlueX

Physicists have long been captivated by the spectrum of hadrons, aiming to better comprehend the fundamental building blocks of matter. While various experiments have laid the foundation for this spectrum, Lattice Quantum Chromodynamics has revealed new states with forbidden JPC values. This has challenged the constituent quark model, suggesting spin-exotic hybrid mesons that could reshape our understanding of hadronic structure and quark-gluon interactions through gluonic excitations. The GlueX experiment at Jefferson Lab has played a pivotal role in this pursuit, with its efforts centered on analyzing photoproduction data. In order to investigate the lightest predicted exotic state with JPC=1−+ , known as the π1(1600) meson, significant attention has been directed towards both ηπ0 and η′π0 systems. Detailed ongoing amplitude analysis studies of γp→η(′)π0p , leveraging the polarization of the photon beam at the GlueX experiment will be highlighted. Furthermore, first studies on the moments of angular distributions for these channels will also be shown, along with the differential cross section results for the a2(1320) meson. These results aid in identifying the dominant production mechanisms and offer valuable insights into complex hadronic interactions. Ultimately, this contributes to the ongoing search for and future identification of exotic hybrid meson candidates.

Baldwin, Zachary↗
DOE OSTI2025

Framework for phase transitions between the Maxwell and Gibbs constructions at finite temperature

The characteristics of the hadron-to-quark first-order phase transition differ depending on whether charge neutrality is locally or globally fulfilled. In 𝛽-equilibrated matter, these two possibilities correspond to the Maxwell and Gibbs constructions. Recently, we presented a new framework in which a continuously varying parameter allows one to describe a first-order phase transition in intermediate scenarios to the two extremes of fully local and fully global charge neutrality. In this work, we extend the previous framework to finite temperatures and out-of-𝛽 equilibrium conditions, making it available for simulations of core-collapse supernovae and binary neutron star mergers. We investigate its impact on key thermodynamic quantities across a range of baryon densities, temperatures, and electron fractions. We find that when matter is not in 𝛽 equilibrium, the pressure in the mixed phase is not constant even for the case of fully local charge neutrality. Moreover, we compute the thermal index using three different approaches, demonstrating that the finite-temperature extension of an equation of state using a constant thermal index can be ill defined when applied to the mixed phase.

QCD phase transitions↗
DOE OSTI2025

DOUBLY-STRANGE BARYON SPECTROSCOPY WITH THE GLUEX EXPERIMENT: GROUND STATE ¿(1320) PHOTOPRODUCTION CROSS SECTION AND PROPERTIES

In the light-quark sector, traditional quark models and, more recently, lattice QCD calculations have predicted many more baryon states than have been experimentally observed. The hyperons, baryons with strange-quark content, in particular abundantly lack these observed states, and past observations are statistically limited. For multi-strange hyperons the matter is much worse and the production mechanisms of these states in photoproduction are very poorly understood. By capitalizing on the narrow peaks, as compared to the broad and overlapping N* and ¿* states, characteristic of the lowest lying ¿ resonances, the systematic aspects of the spectrum can be analyzed. In addition, we can measure experimental observables such as the production cross section to study the production mechanisms of the ¿ resonances. By accumulating various experimental observables, this goal could be accomplished through Partial Wave Analysis (PWA). The main body of work presented in this dissertation is the physics analysis and systematic study of the production cross section for the doubly strange octet ground state baryon (¿(1320)) in the exclusive t-channel photoproduction reaction ¿p ¿ K+Y* ¿ K+(K+¿-)Y* where ¿- ¿ ¿p- and ¿ ¿ pp-. The spin quantum number of ¿(1320) is also extracted and discussed. A preliminary result to extract the mass of ¿(1320) is also explored as a result of the statistical limitations of current measurements. Furthermore, the spectrum of the excited ¿* baryons are explored and discussed in the ¿*- ¿ K-¿ decay channel. The studies on the ground state and excited ¿ baryon are performed using the GlueX Phase-I (GlueX-I) data set. We have extracted differential cross sections from seven beam photon energy bins for E¿ ¿ [6.4,11.4] GeV1 and for -t < 2.4 GeV2 in the production of K+Y*. 1Natural units (c = 1) are used for the entire body of work.

Hernandez, Jesse [Florida State Univ., Tallahassee↗
DOE OSTI2024

Search for baryon junctions in e+A collisions at the electron ion collider

Constituent quarks in a nucleon are the essential elements in the standard “quark model” associated with the electric charge, spin, mass, and baryon number of a nucleon. Quantum chromodynamics (QCD) describes nucleon as a composite object containing current quarks (valence quarks and sea (anti-)quarks) and gluons. These subatomic elements and their interactions are known to contribute in complex ways to the overall nucleon spin and mass. In the early development of QCD theory in the 1970s, an alternative hypothesis postulated that the baryon number might manifest itself through a non-perturbative configuration of gluon fields forming a Y-shaped topology known as the gluon junction. In this work, we propose to test such hypothesis by measuring (i) the Regge intercept of the net-baryon distributions for e+(p)Au collisions, (ii) baryon and charge transport in the isobaric ratio between e+Ru and e+Zr collisions, and (iii) target flavor dependence of proton and antiproton yields at large rapidity, transported from the hydrogen and deuterium targets in e+p(d) collisions. Our study indicates that these measurements at the EIC can help determine what carries the baryon number.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

A Thermal Relic Encyclopedia: Dark Matter Candidates Coupled to Quarks

Thermal freeze-out is a compelling framework for naturally generating the dark matter abundance. We systematically study a broad range of dark matter and mediator particle combinations that can viably realize thermal freeze-out, focusing on models in which the mediator couples to Standard Model quarks. In each case, we calculate the relic density and consider existing constraints from accelerators, cosmology, direct detection, and indirect detection over the full range of dark matter and mediator masses. We present an encyclopedic catalog of matrix elements, cross sections, and decay rates which can be used as a reference for future studies of dark matter phenomenology.

Hooper, Dan [Fermilab; Chicago U., EFI; Chicago U.↗
DOE OSTI2025

Search for boosted low-mass resonances decaying into hadrons produced in association with a photon in pp collisions at $ \sqrt{s}$ = 13 TeV with the ATLAS detector

Many extensions of the Standard Model, including those with dark matter particles, propose new mediator particles that decay into hadrons. This paper presents a search for such low mass narrow resonances decaying into hadrons using 140 fb −1 of proton-proton collision data recorded with the ATLAS detector at a centre-of-mass energy of 13 TeV. The resonances are searched for in the invariant mass spectrum of large-radius jets with two-pronged substructure that are recoiling against an energetic photon from initial state radiation, which is used as a trigger to circumvent limitations on the maximum data recording rate. This technique enables the search for boosted hadronically decaying resonances in the mass range 20–100 GeV hitherto unprobed by the ATLAS Collaboration. The observed data are found to agree with Standard Model predictions and 95% confidence level upper limits are set on the coupling of a hypothetical new spin-1 Z′ resonance with Standard Model quarks as a function of the assumed Z′-boson mass in the range between 20 and 200 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗