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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Multidifferential study of identified charged hadron distributions in Z -tagged jets in proton-proton collisions at $\sqrt{s} =13$ TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a Z boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 < p T < 100 GeV and in the pseudorapidity range 2.5 < η <4. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb –1 . Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Long-lived particles and the quiet Sun

The nuclear reaction network within the interior of the Sun is an efficient MeV physics factory and can produce long-lived particles generic to dark sector models. In this work we consider the sensitivity of satellite instruments, primarily the RHESSI spectrometer, that observe the quiet Sun in the MeV regime where backgrounds are low. We find that quiet Sun observations offer a powerful and complementary probe in regions of parameter space, where the long-lived particle decay length is longer than the radius of the Sun and shorter than the distance between the Sun and Earth. We comment on connections to recent model-building work on heavy neutral leptons coupled to neutrinos and high-quality axions from mirror symmetries.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Mutually elusive: Vectorlike antileptons and leptoquarks

We study the properties of vectorlike fermions that have the same gauge charges as the Standard Model lepton doublets, but opposite lepton number. These antileptons undergo decays mediated by heavier scalar leptoquarks, while the symmetries of this renormalizable model protect the vectorlike fermions and the leptoquarks from standard decays probed so far at colliders. We derive upper limits on the new Yukawa couplings imposed by flavor-changing processes, including 𝐵 → 𝐾⁢$v\bar{v}$ and $𝐵_𝑠$ − $\bar{𝐵}_𝑠$ mixing, and show that they are compatible with prompt antilepton decays at the LHC for wide parameter ranges. If the new particles couple predominantly to second-generation quarks, then their collider probes involve multiple jets and two taus or neutrinos, and are hampered by large backgrounds. If couplings to third-generation quarks are large, then the collider signals involve top quarks, and can be probed more efficiently at the LHC. Even in that case, both the vectorlike fermion doublet and the leptoquarks remain more elusive than in models with standard decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Global quark spin correlations in relativistic heavy ion collisions

The observation of the vector meson’s global spin alignment by the STAR Collaboration reveals that strong spin correlations may exist for quarks and antiquarks in relativistic heavy-ion collisions in the normal direction of the reaction plane. We propose a systematic method to describe such correlations in the quark matter. We classify them as local and long range quark spin correlations in the system. We show in particular that the effective quark spin correlations contain the genuine spin correlations originated directly from the dynamical process as well as those induced by averaging over other degrees of freedom. We also show that such correlations can be studied by measuring the vector meson’s spin density matrix and hyperon-hyperon and hyperon-anti-hyperon spin correlations. We present the relationships between these measurable quantities and spin correlations of quarks and antiquarks. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Top quark electroweak dipole moment at a high energy muon collider

We study the sensitivity reach to probe the electroweak dipole operators associated with a top quark at a multi-TeV lepton collider. Studying the electroweak dipole operators is strongly motivated by precision physics. The operators exhibit unique chiral structure and can be enhanced with respect to others in theories beyond the Standard Model. We illustrate this point in a strongly coupled composite Higgs model. We find that a high energy μ + ⁢μ – collider may offer a unique opportunity to probe the electroweak dipole operators beyond the coverage by the LHC and future hadron colliders. The significant sensitivity is achieved by the leading channel μ + ⁢μ – → $t$$\overline{t}$ near the threshold, and substantially improved by the novel channel μ + ⁢μ – → $t$$\overline{t}$⁢ℎ at high energies. We may be able to reach a new physics scale well above the collider energy for moderate couplings of the Wilson coefficients. Our main conclusions are applicable to future e + ⁢e – colliders.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Intrinsic charm and the 𝐷 + − 𝐷 − asymmetry produced in proton-proton collisions

We investigate the contribution of the charm-anticharm (𝑐⁢$\overline{𝑐}$) asymmetry of the proton eigenstate obtained from QCD lattice gauge to the asymmetry of 𝐷 + , 𝐷 − and 𝐷 0 , $\overline{𝐷}$ 0 mesons produced in 𝑝⁢𝑝 collisions at large Feynman variables 𝑥. It is shown that an important tool for establishing the intrinsic charm (IC) content of the proton is the charm hadron-antihadron asymmetry formed in 𝑝⁢𝑝 collisions. Predictions for the asymmetry as a function of 𝑥 for different IC probabilities are presented. We show that the interference of the intrinsic |𝑢⁢𝑢⁢𝑑⁢𝑐⁢$\overline{𝑐}$⟩ Fock state with the standard contribution from the perturbative QCD evolution leads to a large 𝐷 + ⁢𝐷 − asymmetry at large Feynman 𝑥.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

First Measurement of Λ c Baryon Production in Au + Au Collisions at s N N = 200 GeV

Herein we report on the first measurement of the charmed baryon Λ c ± production at midrapidity ( | y | < 1 ) in Au + Au collisions at s NN = 200 GeV collected by the STAR experiment at the Relativistic Heavy Ion Collider. The Λ c / D 0 [denoting ( Λ c + + Λ c - ) / ( D 0 + D ¯ 0 ) ] yield ratio is measured to be 1.08 ± 0.16 ( stat ) ± 0.26 ( sys ) in the 0%–20% most central Au + Au collisions for the transverse momentum ( p T ) range 3 < p T < 6 GeV / c . This is significantly larger than the pythia model calculations for p + p collisions. The measured Λ c / D 0 ratio, as a function of p T and collision centrality, is comparable to the baryon-to-meson ratios for light and strange hadrons in Au + Au collisions. Model calculations including coalescence hadronization for charmed baryon and meson formation reproduce the features of our measured Λ c / D 0 ratio.

13000 GeV-cms/nucleon↗