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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Higher-order cumulants and correlation functions of proton multiplicity distributions in s N N = 3 GeV Au + Au collisions at the RHIC STAR experiment

Here, we report a measurement of cumulants and correlation functions of event-by-event proton multiplicity distributions from fixed-target Au+Au collisions at $\sqrt{s_\text{NN}}$ = 3 GeV measured by the STAR experiment. Protons are identified within the rapidity (y) and transverse momentum ($p_T$) region –0:9 < $\textit{y}$ < 0 and 0:4 < pT < 2:0 GeV/c in the center-of-mass frame. A systematic analysis of the proton cumulants and correlation functions up to sixth-order as well as the corresponding ratios as a function of the collision centrality, $p_T$, and $\textit{y}$ are presented. The effect of pileup and initial volume fluctuations on these observables and the respective corrections are discussed in detail. The results are compared to calculations from the hadronic transport UrQMD model as well as a hydrodynamic model. In the most central 5% collisions, the value of proton cumulant ratio $C_4 = C_2$ is negative, drastically different from the values observed in Au+Au collisions at higher energies. Compared to model calculations including Lattice QCD, a hadronic transport model, and a hydrodynamic model, the strong suppression in the ratio of $C_4/C_2$ at 3 GeV Au+Au collisions indicates an energy regime dominated by hadronic interactions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Sensitivity of Au + Au collisions to the symmetric nuclear matter equation of state at 2–5 nuclear saturation densities

We demonstrate that proton and pion flow measurements in heavy-ion collisions at incident energies ranging from 1 to 20 GeV per nucleon in the fixed target frame can be used for an accurate determination of the symmetric nuclear matter equation of state at baryon densities equal 2–4 times nuclear saturation density n 0 . We simulate Au + Au collisions at these energies using a hadronic transport model with an adjustable vector mean-field potential dependent on baryon density n B . Here, we show that the mean field can be parametrized to reproduce a given density dependence of the speed of sound at zero temperature $c$$^{2}_{s}$ (n B , T = 0), which we vary independently in multiple density intervals to probe the differential sensitivity of heavy-ion observables to the equation of state at these specific densities. Recent flow data from the STAR experiment at the center-of-mass energies √ s NN = {3.0, 4.5} GeV can be described by our model, and a Bayesian analysis of these data indicates a hard equation of state at n B ϵ (2, 3)n 0 and a possible phase transition at n B ϵ (3, 4)n 0 . More data at √ s NN = 2–5 GeV, as well as a more thorough analysis of the model systematic uncertainties will be necessary for a more precise conclusion.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Vortex rings in event-by-event relativistic heavy-ion collisions

We present event-by-event simulations for central asymmetric light+heavy and Au +Au collisions to investigate the formation and evolution of vortex-ring structures in the longitudinal flow velocity profile. The production-plane polarization of Λ hyperons, defined with respect to the Λ momentum and the beam, can track the “vortex-ring” feature in the event, a characteristic vortical structure generated by longitudinal flow gradients. We make comprehensive model predictions for the rapidity-dependent vortex-ring observables for different collision system sizes at √s NN = 200 and 72 GeV. Furthermore, our predictions at the latter energy can be explored in the future LHCb fixed-target experiment at the Large Hadron Collider.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Measurement of the mass-changing, charge-changing, and production cross sections of 11 C, 11 B, and 10 B nuclei in 12 C + p interactions at 13.5 GeV/𝑐 per nucleon

A good knowledge of nuclear fragmentation cross sections is important to interpret the fluxes of secondary cosmic rays from the Galaxy. Here we report new measurements of nuclear fragmentation with the NA61/SHINE experiment at the CERN SPS. The specific focus is on cross sections important for the production of boron in the Galaxy from the interactions of 12 C nuclei with hydrogen in the interstellar medium, including the contribution from the decay of the short-lived 11 C fragments. The data were taken with the secondary 12 C beam at beam momentum of 13.5 GeV/𝑐per nucleon and two fixed targets, polyethylene (CH 2 ) and graphite (C), from which we derive the cross sections of carbon on hydrogen. We present the measurement of the fragmentation cross sections of 11 C, 11 B, and 10 B as well as the mass- and charge-changing cross sections.

nuclear fragmentation↗
DOE OSTI2021

Characterizing dark matter signals with missing momentum experiments

Fixed target missing-momentum experiments such as LDMX and M 3 are powerful probes of light dark matter and other light, weakly coupled particles beyond the Standard Model (SM). Such experiments involve ~10 GeV beam particles whose energy and momentum are individually measured before and after passing through a suitably thin target. If new states are radiatively produced in the target, the recoiling beam particle loses a large fraction of its initial momentum, and no SM particles are observed in a downstream veto detector. We explore how such experiments can use kinematic variables and experimental parameters, such as beam energy and polarization, to measure properties of the radiated particles and discriminate between models if a signal is discovered. In particular, the transverse momentum of recoiling particles is shown to be a powerful tool to measure the masses of new radiated states, offering significantly better discriminating ability compared to the recoil energy alone. We further illustrate how variations in beam energy, polarization, and lepton flavor (i.e., electron or muon) can be used to disentangle the possible the Lorentz structure of the new interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Tomography of pions and protons via transverse momentum dependent distributions

We perform the first simultaneous extraction of parton collinear and transverse degrees of freedom from low-energy fixed-target Drell-Yan data in order to compare the transverse momentum dependent (TMD) parton distribution functions (PDFs) of the pion and proton. We demonstrate that the transverse separation of the quark field encoded in TMDs of the pion is more than 4⁢𝜎 smaller than that of the proton. Additionally, we find the transverse separation of the quark field decreases as its longitudinal momentum fraction decreases. In studying the nuclear modification of TMDs, we find clear evidence for a transverse EMC effect. We comment on possible explanations for these intriguing behaviors, which call for a deeper examination of tomography in a variety of strongly interacting quark-gluon systems.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Longer-lived mediators from charged mesons and photons at neutrino experiments

Since many of the dark-sector particles interact with Standard Model (SM) particles in multiple ways, they can appear in experimental facilities where SM particles appear in abundance. In this study, we explore a particular class of longer-lived mediators that are dominantly produced from photons and charged mesons that arise in proton-beam fixed-target-type neutrino experiments. This class of mediators encompasses light scalars that appear in theories like extended Higgs sectors, muon(electro)philic scalars, etc. We evaluate the sensitivities of these mediators at beam-based neutrino experiments such as the finished ArgoNeuT, ongoing MicroBooNE, SBND, ICARUS, and the upcoming DUNE experiment. We find that muonphilic scalars are more enhanced while produced from three-body decay of charged mesons. The above-mentioned experiments can probe unexplored regions of parameter space that can explain the current discrepancy in the anomalous magnetic moment of muons. We further find that Compton-like scattering of photons is the largest source of electrophilic scalars. By utilizing this, the DUNE Near Detector can explore new regions in the sensitivity space of electrophilic scalars. We also show that Bethe-Heitler scattering processes can be used to probe flavor-specific lepton final states even for the mediator masses below twice the lepton mass. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Improving resbos for the precision needs of the LHC

The resummation calculation (esos) is a widely used tool for the simulation of single vector boson production at colliders. In this work, we develop a significant improvement over the esos code by increasing the accuracy from NNLL + NLO to N 3 LL + NNLO and release the esos v2.0 code. Furthermore, we propose a new nonperturbative function that includes information about the rapidity of the system (IFY). The IFY functional form was fitted to data from fixed target experiments, the Tevatron, and the LHC. We find that the nonperturbative function has mild rapidity dependence based on the results of the fit. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Exotic particles at the DUNE near detector from charged pion scattering

Fixed-target proton-beam experiments produce a multitude of charged pions that rescatter in the beam dump. These charged pion scattering events can be an additional irreducible source of exotic particles which couple to photons or hadrons. We analyze the sensitivity of the DUNE near detector complex to millicharged particles (MCPs) and heavy axionlike particles (ALPs) with low-energy couplings to gluons. Using the framework of chiral perturbation theory, we demonstrate regimes of parameter space where the charged pion production channel dominates over previously considered production mechanisms for both MCPs and ALPs, thereby improving the sensitivity of DUNE to these new particles compared to previous studies. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Final state interactions for high energy scattering off atomic electrons

We consider the scattering of high energy leptons off bound atomic electrons focusing primarily on final state interactions between the outgoing energetic electron, and the heavy residual charged “debris” in the final state. These effects are inherently absent from calculations for a free electron at rest. Coulomb exchanges are enhanced by the large number of electrons in the atomic debris, and are unsuppressed by nonrelativistic velocities in the debris. We find that these exchanges can be resummed using operator methods, and cancel at the level of the cross section until at least 𝑂⁡(𝛼 3 ). Furthermore, we argue that both final and initial state Coulomb exchanges (enhanced by the number of electrons in the atom) do not affect the cross section until at least 𝑂⁡(𝛼 3 ). Transverse photon couplings to nonrelativistic electrons are proportional to their small velocities, and rotational invariance suppresses their contribution to 𝑂⁡(𝛼 3 ). Our results are relevant for precision experiments involving neutrinos, electrons, positrons, and muons scattering off of atomic electrons in a fixed target.

Atoms↗
DOE OSTI2024

Renormalization-group running of dimension-8 four-fermion operators in the SMEFT

We compute the renormalization-group equations governing the evolution of dimension-8 four-fermion operators in the Standard Model effective field theory (SMEFT). We describe the calculation and present analytic results for both the full flavor structure of the SMEFT and with the assumption of minimal flavor violation. We present numerical results for the renormalization-group evolution of the coefficients, and study their impact on fits of the Large Hadron Collider (LHC) Drell-Yan data. The effects of running on the dimension-8 coefficients can reach 50% or more when evolving from 10 TeV scale down to few-GeV energies relevant for the analysis of fixed-target data. However, the impact of the dimension-8 running on the analysis of Drell-Yan data from the LHC is minimal.

effective field theory↗
DOE OSTI2025

Energy-scaling behavior of intrinsic transverse-momentum parameters in Drell-Yan simulation

An analysis is presented based on models of the intrinsic transverse momentum (intrinsic 𝑘 T ) of partons in nucleons by studying the dilepton transverse momentum in Drell-Yan events. Using parameter tuning in event generators and existing data from fixed-target experiments and from hadron colliders, our investigation spans 3 orders of magnitude in center-of-mass energy and 2 orders of magnitude in dilepton invariant mass. The results show an energy-scaling behavior of the intrinsic 𝑘 T parameters, independent of the dilepton invariant mass at a given center-of-mass energy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Measurements of Proton High-Order Cumulants in s N N = 3 GeV Au + Au Collisions and Implications for the QCD Critical Point

We report cumulants of the proton multiplicity distribution from dedicated fixed-target Au + Au collisions at $\sqrt{s_{NN}}$ = 3.0 GeV , measured by the STAR experiment in the kinematic acceptance of rapidity ( y ) and transverse momentum ( p T ) within - 0.5 < y < 0 and 0.4 < pT < 2.0 GeV / c . In the most central 0%–5% collisions, a proton cumulant ratio is measured to be C 4 / C 2 = - 0.85 ± 0.09 ( stat ) ± 0.82 ( syst ) , which is 2 σ below the Poisson baseline with respect to both the statistical and systematic uncertainties. The hadronic transport UrQMD model reproduces our C 4 / C 2 in the measured acceptance. Compared to higher energy results and the transport model calculations, the suppression in C 4 / C 2 is consistent with fluctuations driven by baryon number conservation and indicates an energy regime dominated by hadronic interactions. These data imply that the QCD critical region, if created in heavy-ion collisions, could only exist at energies higher than 3 GeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Heavy Neutral Leptons via Axionlike Particles at Neutrino Facilities

Heavy neutral leptons (HNLs) are often among the hypothetical ingredients behind nonzero neutrino masses. If sufficiently light, they can be produced and detected in fixed-target-like experiments. We show that if the HNLs belong to a richer—but rather generic—dark sector, their production mechanism can deviate dramatically from expectations associated with the standard-model weak interactions. In more detail, we postulate that the dark sector contains an axionlike particle (ALP) that naturally decays into HNLs. Since ALPs mix with the pseudoscalar hadrons, the HNL flux might be predominantly associated with the production of neutral mesons (e.g., π 0 , η ) as opposed to charge hadrons (e.g., π ± , K ± ). In this case, the physics responsible for HNL production and decay are not directly related and experiments like DUNE might be sensitive to HNLs that are too weakly coupled to the standard model to be produced via weak interactions, as is generically the case of HNLs that play a direct role in the type-I seesaw mechanism. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Window Observables for Benchmarking Parton Distribution Functions

Global analysis of collider and fixed-target experimental data and calculations from lattice quantum chromodynamics (QCD) are used to gain complementary information on the structure of hadrons. We propose novel “window observables” that allow for higher precision cross-validation between the different approaches, a critical step for studies that wish to combine the datasets. Global analyses are limited by the kinematic regions accessible to experiment, particularly in a range of Bjorken-𝑥, and lattice QCD calculations also have limitations requiring extrapolations to obtain the parton distributions. We provide two different window observables that can be defined within a region of 𝑥 where extrapolations and interpolations in global analyses remain reliable and where lattice QCD results retain sensitivity and precision.

lattice QCD↗
DOE OSTI2020

Measurement of $\phi $ meson production in $p + p$ interactions at 40, 80 and $158 \, \hbox {GeV}/c$ with the NA61/SHINE spectrometer at the CERN SPS

Results on $\phi$ meson production in inelastic p+p collisions at CERN SPS energies are presented. They are derived from data collected by the NA61/SHINE fixed target experiment, by means of invariant mass spectra fits in the $\phi \to K^+K^-$ decay channel. They include the first ever measured double differential spectra of $\phi$ mesons as a function of rapidity $y$ and transverse momentum $p_T$ for proton beam momenta of 80 GeV/c and 158 GeV/c, as well as single differential spectra of $y$ or $p_T$ for beam momentum of 40 GeV/c. The corresponding total $\phi$ yields per inelastic p+p event are obtained. These results are compared with existing data on $\phi$ meson production in p+p collisions. The comparison shows consistency but superior accuracy of the present measurements. The emission of $\phi$ mesons in p+p reactions is confronted with that occurring in Pb+Pb collisions, and the experimental results are compared with model predictions. It appears that none of the considered models can properly describe all the experimental observables.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Measurements of ${\Xi }{^-}$ and $\overline{\Xi }{^+}$ production in proton–proton interactions at $\sqrt{s_{NN}}$ = 17.3 $\hbox {Ge}\hbox {V}$ in the NA61/SHINE experiment

The production of $\Xi (1321)^{-}$ and $\overline{\Xi }(1321)^{+}$ hyperons in inelastic $p+p$ interactions is studied in a fixed target experiment at a beam momentum of 158 $\hbox {Ge}\hbox {V}\!/\!c$. Double differential distributions in rapidity ${y}$ and transverse momentum $p_{T}$ are obtained from a sample of 33M inelastic events. They allow to extrapolate the spectra to full phase space and to determine the mean multiplicity of both ${\Xi }{^-}$ and $\overline{\Xi }{^+} $. The rapidity and transverse momentum spectra are compared to transport model predictions. The ${\Xi }{^-} $ mean multiplicity in inelastic $p+p$ interactions at 158 $\hbox {Ge}\hbox {V}\!/\!c$ is used to quantify the strangeness enhancement in A+A collisions at the same centre-of-mass energy per nucleon pair.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Feebly-interacting particles: FIPs 2020 workshop report

With the establishment and maturation of the experimental programs searching for new physics with sizeable couplings at the LHC, there is an increasing interest in the broader particle and astrophysics community for exploring the physics of light and feebly-interacting particles as a paradigm complementary to a New Physics sector at the TeV scale and beyond. FIPs 2020 has been the first workshop fully dedicated to the physics of feebly-interacting particles and was held virtually from 31 August to 4 September 2020. The workshop has gathered together experts from collider, beam dump, fixed target experiments, as well as from astrophysics, axions/ALPs searches, current/future neutrino experiments, and dark matter direct detection communities to discuss progress in experimental searches and underlying theory models for FIPs physics, and to enhance the cross-fertilisation across different fields. FIPs 2020 has been complemented by the topical workshop “Physics Beyond Colliders meets theory”, held at CERN from 7 June to 9 June 2020. This document presents the summary of the talks presented at the workshops and the outcome of the subsequent discussions held immediately after. It aims to provide a clear picture of this blooming field and proposes a few recommendations for the next round of experimental results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗