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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Modern Muon Physics: Selected Issues

The muon was discovered almost hundred years ago, but still remains largely a mystery. For a long time, the only difference between a muon and an electron was the approximately 200 times greater mass of the muon. However, with the later discovery of the charm quantum number, the muon played a decisive role in the formulation of the Standard Model of elementary particles, determining together with muon neutrino and the strange s and the charm c quarks the second generation of particles of this model. The equality of the reaction constant of muon decay with the constant of the vector interaction of beta-decay played a decisive role in the formulation of the conservation of the vector current (CVC) of the weak interaction of elementary particles. Processes involving muons testified in favor of the partial conservation of the axial current of weak interaction (PCAC), that is, one pion exchange in the interaction of the lepton and hadron currents. It was the muon that gave a rise to hopes of creating an alternative energy source within the framework of Muon Catalyzed Fusion (μCF). The possible realization of this process in the future as the intensity of muon beams increases can revolutionired energy supply. Nuclear fission by muons and the study of heavy-nucleus mesoatoms introduced muon physics into several separate branches of physical research.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Semileptonic tau decays beyond the Standard Model

Hadronic τ decays are studied as probe of new physics. We determine the dependence of several inclusive and exclusive τ observables on the Wilson coefficients of the low-energy effective theory describing charged-current interactions between light quarks and leptons. The analysis includes both strange and non-strange decay channels. The main result is the likelihood function for the Wilson coefficients in the tau sector, based on the up-to-date experimental measurements and state-of-the-art theoretical techniques. The likelihood can be readily combined with inputs from other low-energy precision observables. We discuss a combination with nuclear beta, baryon, pion, and kaon decay data. In particular, we provide a comprehensive and model-independent description of the new physics hints in the combined dataset, which are known under the name of the Cabibbo anomaly.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Hidden-strangeness tetraquarks in the dynamical diquark model

The dynamical diquark model describes multiquark exotic hadrons in terms of diquark components nucleated by heavy quarks and successfully explains multiple features of hidden-charm and hidden-bottom exotics. Here, we apply the model to the marginally heavy case of hidden-strange states to probe whether mesons near 2 GeV with peculiar properties, such as 𝜙⁡(2170), 𝑓 2 ⁡(2340), and 𝑋⁡(2370), are possible tetraquark candidates. We calculate spin-multiplet average masses using potentials obtained through lattice simulations and quark models, and we also describe the detailed spectra of the expected multiplets as a diagnostic to discern the nature of future hadrons likely to be discovered in this mass region by experiments at facilities such as BESIII, JLab, and the EIC.

Bound states↗
DOE OSTI2026

Final Technical Report for U.S.-Japan Hadronic Physics Exchange Program for Studies of Hadron Structure and QCD

Nuclear physics explores the fundamental properties of matter -- how protons and neutrons emerge as quantum systems of elementary particles, how they form the atomic nuclei, and how they give rise to the wide variety of phenomena and applications at biological, technical, and astronomical scales. It is a global scientific effort centered around large-scale experimental user facilities (particle accelerators and detectors), advanced theoretical methods and concepts, and computational techniques and resources. Exchange of knowledge and ideas, scientific collaboration, and workforce development on a global scale are essential for the future of the field. The nuclear physics program envisaged in the 2023 DOE/NSF NSAC Long-Range Plan and pursued at the U.S. National Labs has strong synergies with programs at other facilities worldwide and will realize significant benefits from international collaboration. Nuclear physics is also recognized for promoting international cooperation in the broadest sense through joint construction and operation of experimental equipment, personal contacts between scientists, and education and training. The U.S.-Japan Hadronic Physics Exchange Program (USJPHE) supported collaborative scientific research in hadronic physics and quantum chromodynamics. USJHPE focused on subject areas related to the programs at current and future experimental facilities in the U.S.\ and Japan and supported both experimental and theoretical studies. USJHPE particularly aimed to realize synergies between the hadronic physics programs at Jefferson Lab 12 GeV and J-PARC resulting from the complementarity of electromagnetic and hadronic probes in the multi-GeV energy range. Subject areas of common interest included the quark-gluon structure of hadrons and nuclei, meson and baryon spectroscopy, strangeness and hypernuclear physics, and other related topics. USJHPE also supported research in hadronic physics and nuclear-physics-enabled tests of fundamental symmetries related to the programs at Brookhaven National Lab, Fermilab, KEK, Spring-8, and university-based facilities in the U.S. and Japan. USJHPE especially promoted collaboration between the U.S. and Japanese nuclear physics communities in developing the physics program and instrumentation for the future Electron-Ion Collider. USJHPE was intended to provide travel grants to U.S.-based scientists (primary institutional affiliation with a U.S.\ university, national laboratory, or other research center) to visit Japanese institutions and conduct collaborative research there. The program supported senior researchers, postdoctoral fellows, and students. Continuing the setup of the preceding grant period, J-PARC served as the Japanese “hub” for U.S. physicists for short- and long-term visits, and JLab served as the corresponding U.S. “hub”. The program was officially managed through the U. of Connecticut in Storrs, CT. Support for Japanese physicists visiting the U.S. was provided through funds from Japanese funding agencies. The USJHPE program promoted the scientific exchange and the collaborative spirit in hadronic physics between the two countries.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Shear viscosity from perturbative quantum chromodynamics to the hadron resonance gas at finite baryon, strangeness, and electric charge densities

Through model-to-data comparisons from heavy-ion collisions, it has been shown that the quark gluon plasma has an extremely small shear viscosity at vanishing densities. At large baryon densities, significantly less is known about the nature of the shear viscosity from quantum chromodynamics (QCD). Within heavy-ion collisions, there are three conserved charges: baryon number (B), strangeness (S), and electric charge (Q). Here we calculate the shear viscosity in two limits using perturbative QCD (pQCD) and an excluded-volume hadron resonance gas at finite BSQ densities. We then develop a framework that interpolates between these two limits such that shear viscosity is possible to calculate across a wide range of finite BSQ densities. We find that the pQCD and hadron resonance gas calculations have different BSQ density dependencies such that a rather nontrivial shear viscosity appears at finite densities.

Phenomenology↗
DOE OSTI2025

Charged-hadron and identified-hadron (𝐾$^{0}_{𝑆}$, Λ, $Ξ$ − ) yield measurements in photonuclear Pb + Pb and 𝑝 + Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with ATLAS

This paper presents the measurement of charged-hadron and identified-hadron (𝐾$^{0}_{𝑆}$, Λ, $Ξ$ − ) yields in photonuclear collisions using 1.7nb −1 of $\sqrt{s_{NN}}$ = 5.02 TeV Pb + Pb data collected in 2018 with the ATLAS detector at the Large Hadron Collider. Candidate photonuclear events are selected using a combination of tracking and calorimeter information, including the zero-degree calorimeter. The yields as a function of transverse momentum and rapidity are measured in these photonuclear collisions as a function of charged-particle multiplicity. These photonuclear results are compared with 0.1 nb −1 of $\sqrt{s_{NN}}$ = 5.02 TeV p + Pb data collected in 2016 by ATLAS using similar charged-particle multiplicity selections. These photonuclear measurements shed light on potential quark-gluon plasma formation in photonuclear collisions via observables sensitive to radial flow, enhanced baryon-to-meson ratios, and strangeness enhancement. The results are also compared with the Monte Carlo generator and hydrodynamic calculations to test whether such photonuclear collisions may produce small droplets of quark-gluon plasma that flow collectively.

H & He induced nuclear reactions↗
DOE OSTI2023

CMS PYTHIA 8 colour reconnection tunes based on underlying-event data

New sets of parameter tunes for two of the colour reconnection models, quantum chromodynamics-inspired and gluon-move, implemented in the PYTHIA 8 event generator, are obtained based on the default CMS PYTHIA 8 underlying-event tune, CP5. Measurements sensitive to the underlying event performed by the CMS experiment at centre-of-mass energies $\sqrt{s}=$7 and 13 TeV, and by the CDF experiment at 1.96 TeV are used to constrain the parameters of colour reconnection models and multiple-parton interactions simultaneously. The new colour reconnection tunes are compared with various measurements at 1.96, 7, 8, and 13 TeV including measurements of the underlying-event, strange-particle multiplicities, jet substructure observables, jet shapes, and colour flow in top quark pair ($t\bar{t}$) events. The new tunes are also used to estimate the uncertainty related to colour reconnection modelling in the top quark mass measurement using the decay products of $t\bar{t}$ events in the semileptonic channel at 13 TeV .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1985

Heavy flavours production in quark-gluon plasma formed in high energy nuclear reactions

Results on compression and temperatures of nuclear fireballs and on relative yield of strange and charmed hadrons are given . The results show that temperatures above 300 MeV and large compressions are unlikely achieved in average heavy ion collision. In consequence, thermal production of charm is low. Strange particle production is, however, substantial and indicates clear temperature - threshold behavior.

Kloskinski, J.↗
DOE OSTI2025

Measurement of f1(1285) production in pp collisions at $\sqrt{s}$ = 13 TeV

This study presents the first measurement of the f 1 (1285) resonance using the ALICE detector in inelastic proton–proton collisions at a center-of-mass energy of 13 TeV. The resonance is reconstructed at midrapidity (|y| < 0.5) through the hadronic decay channel f 1 (1285)→ K$^0_S$K ± π ± . Key measurements include the determination of its mass, transverse-momentum integrated yield, and average transverse momentum. Additionally, the ratio of the transverse-momentum integrated yield of f 1 (1285) to pion is compared with calculations from the canonical statistical hadronization model. The model calculation, assuming a zero total strangeness content for f 1 (1285), reproduces the data within 1σ deviation, shedding light on the quark composition of f 1 (1285).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Light quark Yukawas in triboson final states

Triple heavy vector boson production, pp → VVV (V = W, Z), has recently been observed for the first time. We propose that precision measurements of this process provide an excellent probe of the first generation light quark Yukawa couplings. Modified quark interactions with the off-shell Higgs in this process lead to a rapid growth of the partonic cross sections with energy, which manifests in an enhanced p T distribution of the final state leptons and quarks. We quantify this effect and estimate the present and future 2σ sensitivity to the up, down, and strange Yukawas. In particular, we find that HL-LHC can reach $\mathscr{O}$(400) sensitivity to the down Yukawa relative to the Standard Model value, improving the current sensitivity in this process by a factor of 10, and which can be further improved to $\mathscr{O}$(30) at FCC-hh. This is competitive with and complementary to constraints from global fits and other on-shell probes of the first generation Yukawas. The triboson sensitivity at HL-LHC corresponds to probing dimension-6 SMEFT operators suppressed by an $\mathscr{O}$(1) TeV scale, similarly to other LHC Higgs probes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Strangeness-changing rates and hyperonic bulk viscosity in neutron star mergers

In this paper we present a computation of the rates of strangeness-changing processes and the resultant bulk viscosity in matter at the densities and temperatures typical of neutron star mergers. To deal with the high temperature in this environment we go beyond the Fermi surface approximation in our rate calculations and numerically evaluate the full phase space integral. Here, we include processes where quarks move between baryons via meson exchange: these have generally been omitted in previous analyses but provide the dominant contribution to the rates of strangeness-changing processes and the bulk viscosity. The calculation of these rates is an essential step towards any calculation of dissipation mechanisms in hyperonic matter in mergers. As one application, we calculate the dissipation times for density oscillations at the frequencies seen in merger simulations. We find that hyperon bulk viscosity for temperatures in the MeV regime can probably be neglected in this context, but becomes highly relevant for keV-range temperatures.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Probing quantum entanglement with generalized parton distributions at the Electron-Ion Collider

Within the collinear factorization framework based on generalized parton distributions, we calculate the spin density matrix of exclusively produced quark and antiquark pairs $𝑢\bar{𝑢}$, $𝑑⁢\bar{d}$, $𝑠⁢\bar{𝑠}$, $𝑐\bar{⁢𝑐}$, $𝑏\bar{𝑏}$ in electron-proton scattering. The presence of both real and imaginary parts in the scattering amplitudes leads to a rich pattern of entanglement between the quark and the antiquark. We map out kinematical regions where the pairs exhibit entanglement, Bell nonlocality, and nonstabilizerness. We also predict that massive quarks and antiquarks are transversely polarized, similar to the well-known transverse hyperon polarization in unpolarized collisions. In strangeness, charm, and bottom productions, the polarization can reach 50%–80% in certain kinematic regions in the low-energy runs of the Electron-Ion Collider.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1988

On the formation of black holes

The paper explores the consequences of the existence of a burning process beyond ordinary nuclear processes (which stop at iron), involving the 'strange' particles. In effect, this idea has already had considerable discussion within the high energy physics community in terms of 'quark' matter. A possible consequence is that neutron stars may explode rather than collapse to black holes. It should be evident that such a possibility suggests radically new scenarios for activity in galactic nuclei and gamma ray burst sources.

Michel, F. Curtis↗
DOE OSTI2022

Test of lepton universality in beauty-quark decays

The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Monte Carlo event generator for initial conditions of conserved charges in nuclear geometry

At top collider energies where baryon stopping is negligible, the initial state of heavy-ion collisions is overall charge neutral and predominantly composed of gluons. Nevertheless, there can also be significant local fluctuations of the baryon number, strangeness, and electric charge densities about zero, perturbatively corresponding to the production of quark/antiquark pairs. These previously ignored local charge fluctuations can permit the study of charge diffusion in the quark-gluon plasma (QGP), even at top collider energies. In this paper we present a new model denoted ICCING (initial conserved charges in nuclear geometry) which can reconstruct the initial conditions of conserved charges in the QGP by sampling a (g→q¯q) splitting probability over the initial energy density. We find that the new charge distributions generally differ from the bulk energy density; in particular, the strangeness distribution is significantly more eccentric than standard bulk observables and appears to be associated with the geometry of hot spots in the initial state. The new information provided by these conserved charges opens the door to studying a wealth of new charge- and flavor-dependent correlations in the initial state and ultimately the charge transport parameters of the QGP.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Baseline predictions of elliptic flow and fluctuations for the RHIC Beam Energy Scan using response coefficients

Currently the RHIC Beam Energy Scan is exploring a new region of the Quantum Chromodynamic phase diagram at large baryon densities that approaches nuclear astrophysics regimes. This provides an opportunity to study relativistic hydrodynamics in a regime where the net conserved charges of baryon number, strangeness, and electric charge play a role, which will significantly change the theoretical approach to simulating the baryon-dense Quark-Gluon Plasma. In this work, we detail many of the important changes needed to adapt both initial conditions and the medium to baryon-rich matter. Then, we make baseline predictions for the elliptical flow and fluctuations based on extrapolating the physics at LHC and top RHIC energies to support future analyses of where and how the new baryon-dense physics causes these extrapolations to break down. First we compare eccentricities across beam energies, exploring their underlying assumptions; we find the the extrapolated initial state is predicted to be nearly identical to that at AuAu $\sqrt{s_{NN}}$ = 200 GeV. Then the final flow harmonic predictions are based on linear+cubic response. We discuss preliminary STAR results in order to determine the implications that they have for linear+cubic response coefficients at the lowest beam energy of AuAu $\sqrt{s_{NN}}$ = 7 GeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Partial Wave Analysis of Strange Mesons Decaying to K+p+p- in the Reaction ¿p ¿ K+p+p-¿(1520) and the Commissioning of the GlueX DIRC Detector

Hadron spectroscopy is a cornerstone of our understanding of the strong nuclear interactions. Studying the hadron spectrum led to the postulation of quarks and gluons, and the development of Quantum Chromodynamics (QCD), the theory of the strong nuclear force. Today hadron spectroscopy provides an important test of QCD, particularly in the non-perturbative energy regime. One such test is the existence of hybrid hadrons that have gluonic degrees of freedom, e.g. q ?qg states, that are allowed by QCD but have remained elusive in experimental searches. The GlueX experiment located at Thomas Jefferson National Accelerator Facility, is designed to map the light meson spectrum, including hybrid mesons, produced by a linearly polarized photon beam that is scattered off of a liquid hydrogen target. This dissertation concerns the installation and commissioning of the GlueX DIRC upgrade and the analysis of three reactions measured by the GlueX experiment. The GlueX DIRC is a particle identification detector installed as an upgrade to the GlueX experiment in 2019 to improve the experiment?s ability to distinguish pions and kaons. The DIRC uses Cherenkov photons radiated by charged particles that travel faster than the speed of light in the detector medium to determine the velocity of said particles. The velocity measurement is used in conjunction with momentum measurements from other detectors to determine the mass of the particle. The DIRC will be essential to the future of strange meson spectroscopy in GlueX. The reactions ?p ? K+K??+??p, ?p ? K+K??0?0p, ?p ? K+K??0?p were initially chosen for this analysis to search for the hybrid meson candidate ?(2170) and related resonances. The ?(2170) has been observed in e+e? collider experiments decaying to K+K??+?? and K+K??0?0, among other final states. The ?(2170) was not observed in this analysis. The reaction ?p ? K+?+???(1520), a subset of the ?p ? K+K??+??p reaction, was analyzed with a Partial Wave Analysis (PWA) in order to study strange mesons that decay to K+?+??. In the PWA, a useful model for the angular distributions was found but no significant structures could be observed due to statistical limitations.

Hurley, Andrew↗
DOE OSTI2021

Low-energy Scattering and Effective Interactions of Two Baryons at $m_{\pi}\sim$ 450 MeV from Lattice Quantum Chromodynamics

The interactions between two octet baryons are studied at low energies using lattice QCD (LQCD) with larger-than-physical quark masses corresponding to a pion mass of $m_{\pi}\sim 450$ MeV and a kaon mass of $m_{K}\sim 596$ MeV. The two-baryon systems that are analyzed range from strangeness $S=0$ to $S=-4$ and include the spin-singlet and triplet $NN$, $\Sigma N$ ($I=3/2$), and $\Xi\Xi$ states, the spin-singlet $\Sigma\Sigma$ ($I=2$) and $\Xi\Sigma$ ($I=3/2$) states, and the spin-triplet $\Xi N$ ($I=0$) state. The $s$-wave scattering phase shifts, low-energy scattering parameters, and binding energies when applicable, are extracted using L\"uscher's formalism. While the results are consistent with most of the systems being bound at this pion mass, the interactions in the spin-triplet $\Sigma N$ and $\Xi\Xi$ channels are found to be repulsive and do not support bound states. Using results from previous studies at a larger pion mass, an extrapolation of the binding energies to the physical point is performed and is compared with experimental values and phenomenological predictions. The low-energy coefficients in pionless EFT relevant for two-baryon interactions, including those responsible for $SU(3)$ flavor-symmetry breaking, are constrained. The $SU(3)$ symmetry is observed to hold approximately at the chosen values of the quark masses, as well as the $SU(6)$ spin-flavor symmetry, predicted at large $N_c$. A remnant of an accidental $SU(16)$ symmetry found previously at a larger pion mass is further observed. The $SU(6)$-symmetric EFT constrained by these LQCD calculations is used to make predictions for two-baryon systems for which the low-energy scattering parameters could not be determined with LQCD directly in this study, and to constrain the coefficients of all leading $SU(3)$ flavor-symmetric interactions, demonstrating the predictive power of two-baryon EFTs matched to LQCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗