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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Transverse Single Spin Asymmetries of Heavy Flavor Electrons and Charged Pions in 200 GeV $p+p^{\uparrow}$ Collisions at Midrapidity

Transverse single spin asymmetries of particles produced in p+p^{\uparrow} p + p ↑ collisions provide insight on the partonic spin and momentum structure of hadrons; heavy flavor electrons provide access to initial state spin-momentum correlations of gluons in the proton, while charged pions provide access to initial and final state transverse spin effects. Charged particles are measured at midrapidity at PHENIX using the silicon vertex detector and central arm spectrometer, made of an electromagnetic calorimeter, a ring-imaging Cherenkov detector, and drift and pad chambers. Recent results for both electron and charged pion measurements from the 2015 running period will be presented.

Fitzgerald, Dillon↗
DOE OSTI2022

Nucleon and pion PDFs: large-x asymptotics meets functional mimicry

We review strategies to unveil the primordial large- x x structure of the nucleons as well as the pion from hard-scattering experiments. Ideas are presented for learning about the x\to 1 x → 1 limit of nonperturbative QCD dynamics at energy scales of order 1 GeV from collider experiments at much higher scales. The behavior of parton distributions at x\to 1 x → 1 predicted by the quark counting rules and other low-energy theoretical approaches is contrasted with phenomenological PDFs. Polynomial mimicry of PDF parametrizations is one of many factors that influence the apparent power of the (1-x) ( 1 − x ) falloff. We discuss implications of the mimicry for the large- x x falloff of the pion PDFs.

Courtoy, Aurore↗
DOE OSTI2015

HARP targets pion production cross section and yield measurements. Implications for MiniBooNE neutrino flux

The prediction of the muon neutrino flux from a 71.0 cm long beryllium target for the MiniBooNE experiment is based on a measured pion production cross section which was taken from a short beryllium target (2.0 cm thick - 5% nuclear interaction length) in the Hadron Production (HARP) experiment at CERN. To verify the extrapolation to our longer target, HARP also measured the pion production from 20.0 cm and 40.0 cm beryllium targets. The measured production yields, d 2 N π± (p; θ )=dpd Ω, on targets of 50% and 100% nuclear interaction lengths in the kinematic rage of momentum from 0.75 GeV/c to 6.5 GeV/c and the range of angle from 30 mrad to 210 mrad are presented along with an update of the short target cross sections. The best fitted extended Sanford-Wang (SW) model parameterization for updated short beryllium target π + production cross section is presented. Yield measurements for all three targets are also compared with that from the Monte Carlo predictions in the MiniBooNE experiment for different SW parameterization. The comparisons of v μ flux predictions for updated SW model is presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Structure of the Pion from First Principles Calculation in Lattice QCD

I describe the recent progress by the HadStruct Collaboration aimed at computing the structure of the pion from first-principles calculation in lattice QCD. I begin by presenting the Pseudo-PDF and Lattice Cross Section approaches, emphasizing that they are formulated in terms of Lorentz invariants with a short-distance scale to admit factorization. I present resent results on the pion PDF using both approaches, and compare with phenomenological determinations and other theoretical approaches. I conclude with plans for future work.

Richards, David↗
DOE OSTI2017

Pion and Kaon Structure on the Lattice

I describe recent progress at understanding the structure of the pion and kaon in lattice QCD, and in particular in the energy region accessible to an electron-ion collider. I begin by outline calculations of the form factors, and in particular at high momentum transfers, before proceeding to the discussion of pion and kaon structure functions.

Richards, David↗
DOE OSTI2017

Lattice calculation of the pion electromagnetic form factor at high momentum transfer

The pion electromagnetic form factor, Fn, is a fundamentally important topic for our understanding of the hadron structure and the transition from perturbative to nonperturbative QCD. JLAB?s experiment E12-06-101 proposes to extend the high quality F? data to Q2=6.0 GeV2 as a part of JLAB?s 12 GeV upgrade. Being motivated by this, we present a lattice QCD calculation of Fn using the method of distillation and the variational approach which significantly reduce the excited state contamination. We study the shape of the vector form factor in the Q2 range from zero to a few GeV2 using Wilson quark formalism on our 203×128 anisotropic lattice configuration with light (up/down) and strange quarks in the sea and 400 MeV pion mass.

Chakraborty, Bipasha↗
DOE OSTI2023

Future Pion Structure Studies with JLab 22 GeV and EIC

One of the most puzzling aspects of the Standard Model is that the overwhelming majority of the mass of hadronic systems arises from massless and nearly massless objects. How this occurs is poorly understood, and remains a major open question of the standard model. From the little that we do understand, we know that mass generation is intricately connected to the internal structure of hadronic systems. Emergent Hadronic Mass is an elemental feature of the Standard Model. It is the origin of a running gluon mass, the source of Dynamical Chiral Symmetry Breaking, and very probably crucial to any explanation of confinement. Somewhat counter intuitively, it is one of the lightest hadronic objects, the charged pion, that may be able to fill in the missing piece of the puzzle. Advancing our understanding of the internal structure of the charged pion is crucial if we are to begin to untangle how this structure emerges from the dynamical nature of the interactions that govern it. Fortuitous

Kay, Stephen↗
DOE OSTI2026

Progress toward double-differential cross-section measurements of single charged-pion production in charged current muon neutrino interactions on argon with SBND

Resonant neutrino–nucleus processes constitute a significant portion of neutrino interactions in the few-GeV energy region. Charged-current interactions with a muon and one single charged pion in the final state (CC1$\pi$) are primarily sensitive to resonant processes, while also receiving contributions from non-resonant processes and being strongly affected by nuclear effects and final-state interactions. A precise understanding of this channel is essential for improving neutrino interaction models and reducing systematic uncertainties in oscillation measurements. The Short-Baseline Near Detector (SBND) at Fermilab has collected the largest neutrino–argon dataset to date, providing an excellent opportunity to study CC1$\pi$ interactions on argon. This analysis aims to improve existing single-differential cross-section measurements by reporting results in a variety of kinematic variables and to perform the first double-differential CC1$\pi$ cross-section measurement on argon, using novel techniques for pion energy reconstruction.

Pelegrina-Gutiérrez, Luis [Granada U.] (ORCID:0000↗
DOE OSTI2026

Charged Pion Production Explorations Using the NOvA Near Detector

The~300T NOvA Near Detector (ND) utilizes segmented liquid scintillator to reconstruct interacting neutrinos arriving from the NuMI Beamline at Fermilab. Given NuMI’s intensity and the ND’s relatively short baseline, NOvA has recorded some of the world’s highest statistics for neutrino interactions around ~2GeV, in great similarity to the forthcoming DUNE experiment. This energy regime is replete with resonant interactions, which will form the plurality of final states in DUNE. NOvA seeks to empower the community with measurements of processes for both semi-exclusive and semi-inclusive charged pion production across muon kinematics and pion angle via single-and multidifferential neutrino scattering cross sections. This poster will review current progress across several related analyses, and look forward to future results.

Roy, Palash K. [Wichita State U.] (ORCID:000000022↗
DOE OSTI2022

Progress in calculation of the fourth Mellin moment of the pion light-cone distribution amplitude using the HOPE method

The pion light-cone distribution amplitude (LCDA) is a central non-perturbative object of interest for the calculation of high-energy exclusive processes in quantum chromodynamics. This article describes the progress in the lattice QCD calculation of the fourth Mellin moment of the pion LCDA using a heavy-quark operator product expansion (HOPE).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

The Unitarity-Limit Expansion for Two Nucleons with Perturbative Pions: Digest and Ideas

Theorists love nontrivial fixed points. In the Unitarity Limit, the NN 𝑆-wave binding energies are zero, the scattering lengths infinite, Physics is universal, i.e. insensitive to details of the interactions, and observables display richer symmetries, namely invariance under both scaling and Wigner’s combined SU(4) transformation of spin and isospin. In “Pionless” EFT, both are explicitly but weakly broken and hence perturbative in the Unitarity Window (phase shifts 45° ≲ δ(k) ≲ 135°, i.e. momenta k≈mπ). This Unitarity Expansion provides strong hints that Nuclear Physics resides indeed in a sweet spot: bound weakly enough to be insensitive to the details of the nuclear interaction; and therefore interacting strongly enough that the NN scattering lengths are perturbatively close to the Unitarity Limit. In this paradigm change, NN details are less important than NNN interactions to explain the complexity and patterns of the nuclear chart. This presentation is a digest of the first quantitative exploration of corrections to this picture when pions are included [1] (see there for a more comprehensive list of references). Since the pion mass and decay constant introduce dimensionful scales in the NN system, they explicitly break the symmetries of the Unitarity fixed point. In χEFT, these symmetries must therefore be hidden and instead be classified as emergent.

Griesshammer, Harald W. [The George Washington Uni↗
DOE OSTI2025

Di-nucleons do not form bound states at heavy pion mass

We perform a high-statistics lattice QCD calculation of the low-energy two-nucleon scattering amplitudes. In order to address discrepancies in the literature, the calculation is performed at a heavy pion mass in the limit that the light quark masses are equal to the physical strange quark mass, $m_π= m_K \simeq 714 $ MeV. Using a state-of-the-art momentum space method, we rule out the presence of a bound di-nucleon in both the isospin 0 (deuteron) and 1 (di-neutron) channels, in contrast with many previous results that made use of compact hexaquark creation operators. In order to diagnose the discrepancy, we add such hexaquark interpolating operators to our basis and find that they do not affect the determination of the two-nucleon finite volume spectrum, and thus they do not couple to deeply bound di-nucleons that are missed by the momentum-space operators. Further, we perform a high-statistics calculation of the HAL QCD potential on the same gauge ensembles and find qualitative agreement with our main results. We conclude that two-nucleons do not form bound states at heavy pion masses and that previous identification of deeply bound di-nucleons must have arisen from a misidentification of the spectrum from off-diagonal elements of a correlation function.

FOS: Physical sciences↗
DOE OSTI2023

Pion Energy Regression in High-Granularity Calorimeter Prototype

The dataset consists of simulations of calibrated reconstructed hits produced by a pion passing through the HGCAL test beam prototype. For the simulations, Monte Carlo method is used to produce the pions with energy ranging from 10 to as high as 500 GeV. The dataset contains the coordinates of the calibrated reconstructed hits in the prototype along with the calibrated energy in units of MIP. The HDF5 files can be extracted from the gzip files.

FAIR4HEP↗
DOE OSTI2017

The Large N Limit with Vanishing Leading Order Condensate for Zero Pion Mass

It is conventionally assumed that the negative mass squared term in the linear sigma model version of the pion Lagrangian is M 2 ~Λ 2 QCD in powers of N c [1]. We consider the case where M 2 ~Λ 2 QCD /N c so that to leading order in N c this symmetry breaking term vanishes. We present some arguments why this might be plausible. One might think that such a radical assumption would contradict lattice Monte Carlo data on QCD as function of N c . We show that the linear sigma model gives a fair description of the data of DeGrand and Liu both for N c = 3, and for variable N c . The values of quark masses considered by DeGrand and Liu, and by Bali et. al. turn out to be too large to resolve the case we consider from that of the conventional large N c limit [2, 3]. We argue that for quark masses m q »Λ QCD /N c 3/2 , both the baryon mass and nucleon size scale as √N c . For m q >> Λ QCD /N c 3/2 the conventional large-N c counting holds. The physical values of quark masses for QCD (N c = 3) correspond to the small quark mass limit. We nd pion nucleon coupling strengths are reduced to order O(1) rather than O(N c ). Under the assumption that in the large Nc limit the sigma meson mass is larger than that of the omega, and that the omega-nucleon coupling constant is larger than that of the sigma, we argue that the nucleon-nucleon large range potential is weakly attractive and admits an interaction energy of order Λ QCD /N c 5/2 ~10 MeV. With these assumptions on coupling and masses, there is no strong long range attractive channel for nucleon-nucleon interactions, so that nuclear matter at densities much smaller than that where nucleons strongly interact is a weakly interacting con guration of nucleons with strongly interacting localized cores. This situation is unlike the case in the conventional large N c limit, where nuclear matter is bound with binding energies of order the nucleon mass and forms a Skyrme crystal.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Chiral-symmetry Breaking and Pion Structure in the Covariant Spectator Theory

We introduce a covariant approach in Minkowski space for the description of quarks and mesons that exhibits both chiral-symmetry breaking and confinement. In a simple model for the interquark interaction the quark mass function is obtained and used in the calculation of the pion form factor. We study the effects of the mass function and of the different quark pole contributions on the pion form factor.

Biernat, E. P.↗