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DOE OSTI2013

HYPERACCRETING BLACK HOLE AS GAMMA-RAY BURST CENTRAL ENGINE. I. BARYON LOADING IN GAMMA-RAY BURST JETS

A hyperaccreting stellar-mass black hole has been long speculated as the best candidate for the central engine of gamma-ray bursts (GRBs). Recent rich observations of GRBs by space missions such as Swift and Fermi pose new constraints on GRB central engine models. In this paper, we study the baryon-loading processes of a GRB jet launched from a black hole central engine. We consider a relativistic jet powered by {nu} {nu}-bar -annihilation or by the Blandford-Znajek (BZ) mechanism. We consider baryon loading from a neutrino-driven wind launched from a neutrino-cooling-dominated accretion flow. For a magnetically dominated BZ jet, we consider neutron drifting from the magnetic wall surrounding the jet and subsequent positron capture and proton-neutron inelastic collisions. The minimum baryon loads in both types of jet are calculated. We find that in both cases a more luminous jet tends to be more baryon poor. A neutrino-driven ''fireball'' is typically ''dirtier'' than a magnetically dominated jet, while a magnetically dominated jet can be much cleaner. Both models have the right scaling to interpret the empirical {Gamma}-L{sub iso} relation discovered recently. Since some neutrino-driven jets have too much baryon loading as compared with the data, we suggest that at least a good fraction of GRBs should have a magnetically dominated central engine.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2018

A gradient based method for modeling baryons and matter in halos of fast simulations

Fast N-body PM simulations with a small number of time steps such as FastPM or COLA have been remarkably successful in modeling the galaxy statistics, but their lack of small scale force resolution and long time steps cannot give accurate halo matter profiles or matter power spectrum. High resolution N-body simulations can improve on this, but lack baryonic effects, which can only be properly included in hydro simulations. Here we present a scheme to calibrate the fast simulations to mimic the precision of the hydrodynamic simulations or high resolution N-body simulations. The scheme is based on a gradient descent of either effective gravitational potential, which mimics the short range force, or of effective enthalpy, which mimics gas hydrodynamics and feedback. The scheme is fast and differentiable, and can be incorporated as a post-processing step into any simulation. It gives very good results for the matter power spectrum for several of the baryonic feedback and dark matter simulations, and also gives improved dark matter halo profiles. The scheme is even able to find the large subhalos, and increase the correlation coefficient between the fast simulations and the high resolution N-body or hydro simulations. It can also be used to add baryonic effects to the high resolution N-body simulations. While the method has free parameters that can be calibrated on various simulations, they can also be viewed as astrophysical nuisance parameters describing baryonic effects that can be marginalized over during the data analysis. In this view these parameters can be viewed as an efficient parametrization of baryonic effects.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

Search for the doubly heavy baryons $ {{{{\varOmega}_{bc}^{0}}}} $ and $ {{{{\varXi}_{bc}^{0}}}} $ decaying to $ {{{{\varLambda}^+_c}}} {{{{\pi}^-}}} $ and $ {{{{\varXi}^+_c}}} {{{{\pi}^-}}} $ *

The first search for the doubly heavy $ {{{{\varOmega}_{bc}^{0}}}} $ baryon and a search for the $ {{{{\varXi}_{bc}^{0}}}} $ baryon are performed using $ pp $ collision data collected via the $ {\rm{LHCb}} $ experiment from 2016 to 2018 at a centre-of-mass energy of $ 13 \;{\rm{TeV}} $, corresponding to an integrated luminosity of 5.2 $ \;{\rm{f}}{{\rm{b}}^{ - 1}} $. The baryons are reconstructed via their decays to $ {{{{\varLambda}^+_c}}} {{{{\pi}^-}}} $ and $ {{{{\varXi}^+_c}}} {{{{\pi}^-}}} $. No significant excess is found for invariant masses between 6700 and 7300 $ \;{\rm{MeV}}/{c^2} $, in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 $ \;{\rm{MeV}}/{c} $. Upper limits are set on the ratio of the $ {{{{\varOmega}_{bc}^{0}}}} $ and $ {{{{\varXi}_{bc}^{0}}}} $ production cross-section times the branching fraction to $ {{{{\varLambda}^+_c}}}{{{{\pi}^-}}} $ ( $ {{{{\varXi}^+_c}}}{{{{\pi}^-}}} $) relative to that of the $ {{{{\varLambda}^0_b}}} $ ( $ {{{{\varXi}_{b}^{0}}}} $) baryon, for different lifetime hypotheses, at 95% confidence level. The upper limits range from $ 0.5\times10^{-4} $ to $ 2.5\times10^{-4} $ for the $ {{{{{{{{\varOmega}_{bc}^{0}}}}{{\rightarrow }}{{{{\varLambda}^+_c}}}{{{{\pi}^-}}}}}}} $ ( $ {{{{{{{{\varXi}_{bc}^{0}}}}{{\rightarrow }}{{{{\varLambda}^+_c}}}{{{{\pi}^-}}}}}}} $) decay, and from $ 1.4\times10^{-3} $ to $ 6.9\times10^{-3} $ for the $ {{{{{{{{\varOmega}_{bc}^{0}}}}{{\rightarrow }}{{{{\varXi}^+_c}}}{{{{\pi}^-}}}}}}} $ ( $ {{{{{{{{\varXi}_{bc}^{0}}}}{{\rightarrow }}{{{{\varXi}^+_c}}}{{{{\pi}^-}}}}}}} $) decay, depending on the considered mass and lifetime of the $ {{{{\varOmega}_{bc}^{0}}}} $ ( $ {{{{\varXi}_{bc}^{0}}}} $) baryon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

The impact of baryonic discs on the shapes and profiles of self-interacting dark matter haloes

We employ isolated N-body simulations to study the response of self-interacting dark matter (SIDM) haloes in the presence of the baryonic potentials. Dark matter self-interactions lead to kinematic thermalization in the inner halo, resulting in a tight correlation between the dark matter and baryon distributions. A deep baryonic potential shortens the phase of SIDM core expansion and triggers core contraction. This effect can be further enhanced by a large self-scattering cross-section. We find the final SIDM density profile is sensitive to the baryonic concentration and the strength of dark matter self-interactions. Assuming a spherical initial halo, we also study evolution of the SIDM halo shape together with the density profile. The halo shape at later epochs deviates from spherical symmetry due to the influence of the non-spherical disc potential, and its significance depends on the baryonic contribution to the total gravitational potential, relative to the dark matter one. In addition, we construct a multicomponent model for the Milky Way, including an SIDM halo, a stellar disc, and a bulge, and show it is consistent with observations from stellar kinematics and streams.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Excluded-volume model for quarkyonic matter. II. Three-flavor shell-like distribution of baryons in phase space

We extend the excluded-volume model of isospin symmetric two-flavor dense quarkyonic matter [Phys. Rev. C 101, 035201 (2020)] including strange particles and address its implications for neutron stars. The effective sizes of baryons are defined from the diverging hard-core potentials in the short interdistance regime. Around the hard-core density, the repulsive core between baryons at short distances leads to a saturation in the number density of baryons and generates perturbative quarks from the lower phase space, which leads to the shell-like distribution of baryons by the Pauli exclusion principle. The strange-quark Fermi sea always appears at high densities but the Λ hyperon shell only appears when the effective size of the Λ hyperon is smaller than the effective size of nucleons. We find that the pressure of strange quarkyonic matter can be large enough to support neutron stars with two times solar mass and can have a large sound speed, $c^2_s ≃ 0.7$. Finally, the fraction of the baryon number carried by perturbative quarks is about 30% at the inner core of most massive neutron stars.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Probing initial baryon stopping and equation of state with rapidity-dependent directed flow of identified particles

In this work, using a (3 + 1)-dimensional hybrid framework with parametric initial conditions, we study the rapidity-dependent directed flow $v_1 (y)$ of identified particles, including pions, kaons, protons, and lambdas in heavy-ion collisions. Cases involving Au + Au collisions are considered, performed at $\sqrt {^SNN}$ ranging from 7.7 to 200 GeV. The dynamics in the beam direction is constrained using the measured pseudo-rapidity distribution of charged particles and the net proton rapidity distribution. Within this framework, the directed flow of mesons is driven by the sideward pressure gradient from the tilted source, and that of baryons mainly due to the initial asymmetric baryon distribution with respect to the beam axis driven by the transverse expansion. Our approach successfully reproduces the rapidity- and beam energy-dependence of $v_1$ for both mesons and baryons. We find that the $v_1 (y)$ of baryons has strong constraining power on the initial baryon stopping, and together with that of mesons, the directed flow probes the equation of state of the dense nuclear matter at finite chemical potentials.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Composite octet baryons in a relativistic mean field description of nuclear and neutron star matter

Here, we examine the properties of composite octet baryons in the nuclear medium and neutron-star matter. The internal quark-diquark structure of the octet baryons and the equations of state of nuclear matter and neutron-star matter in the mean field approximation are described by using the three-flavor Nambu-Jona-Lasinio (NJL) model as an effective quark theory of quantum chromodynamics. After introducing our model, we first discuss the properties of single baryons and their effective meson exchange interactions in symmetric nuclear matter by using concepts of Fermi-liquid theory. Several model-independent implications of this description are derived and illustrated by numerical results obtained in our model. Second, we extend the model description to high baryon densities and investigate the equation of state of neutron-star matter and the resulting star masses. We find that the so-called hyperon puzzle persists also for the case of composite hadrons. To get more information on this point, we also investigate the role of 6-Fermi and 8-Fermi interactions, in addition to the standard 4-Fermi interactions. The strengths of those higher-order Fermi interactions is determined so as not to spoil the saturation properties of nuclear matter. Among them, an interaction characterized by a product of four-quark current operators plays a special role to stabilize the stars over a large region of central baryon densities, although it has little effect on the maximum star masses.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Mixed-species charge and baryon balance functions studies with PYTHIA

Mixed species charge and baryon balance functions are computed based on proton-proton ( p p ) collisions simulated with the PYTHIA8 model. Simulations are performed with selected values of the collision energy s and the Monash tune and the ropes and shoving modes of PYTHIA8 to explore whether such measurements provide useful new information and constraints on mechanisms of particle production in p p collisions. Charge balance functions are studied based on mixed pairs of pions, kaons, and protons, whereas baryon balance functions are computed for mixed low mass strange and nonstrange baryons. Both charge and baryon balance functions of mixed particle pairs feature shapes and amplitudes that sensitively depend on the particle considered owing largely to the particle production mechanisms implemented in PYTHIA. The evolution of balance functions integrals with the longitudinal width of the acceptance are presented and one finds that sums of such integrals for a given reference particle obey expected sum rules for both charge and baryon balance functions. Additionally, both types of balance functions are found to evolve in shape and amplitude with increasing collision energy s and the PYTHIA tunes considered. Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

Measurement of the fraction of jet longitudinal momentum carried by Λ c + baryons in p p collisions

Recent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried by Λ c + baryons, z ∥ ch , in hadronic collisions. The results are obtained in proton-proton ( p p ) collisions at s = 13 TeV at the LHC, with Λ c + baryons and charged (track-based) jets reconstructed in the transverse momentum intervals of 3 ≤ p T Λ c + < 15 GeV / c and 7 ≤ p T jet ch < 15 GeV / c , respectively. The z ∥ ch distribution is compared to a measurement of D 0 -tagged charged jets in p p collisions as well as to 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronization models which include color correlations beyond leading-color in the string formation. © 2024 CERN, for the ALICE Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Impact of baryonic feedback on HSC-Y1 weak lensing non-Gaussian statistics

Baryonic feedback is a major systematic in weak lensing cosmology. Its most studied effect is the suppression of the lensing power spectrum, a second-order statistic, on small scales. Motivated by the growing interest in statistics beyond the second order, we investigate the effect of baryons on lensing non-Gaussian statistics and the resulting biases in the matter clustering amplitude S 8 = σ 8 Ω m / 0.3 . We focus on the Subaru Hyper Suprime-Cam Year 1 (HSC-Y1) data which, with its high source number density, closely resembles those expected from the upcoming Euclid and Rubin Legacy Survey of Space and Time. We study four non-Gaussian statistics of convergence maps—peak counts, minimum counts, the probability distribution function, and the scattering transform coefficients—in addition to the usual power spectrum. We first estimate the biases in S 8 using mock observations built from the IllustrisTNG and BAHAMAS hydrodynamical simulations and theoretical models built from dark-matter-only simulations. We find up to 1 σ bias in S 8 when the smallest scales (2 arcmin) and the highest feedback level are considered. We then analyze the HSC-Y1 data and compare the S 8 obtained for each statistic with different smoothing scales or scale cuts. As we expect that baryons mostly affect the small scales, comparing the results obtained from including and excluding small scales can indicate the level of impact from baryons. With HSC data, we find only minor ( ≤ 0.5 σ ) differences in S 8 for all statistics, even when considering very small scales (2 arcmin). Our results suggest that the effect of baryons is insignificant at the level of HSC-Y1 down to 2 arcmin for all statistics examined here, or it is canceled by other scale-dependent systematics.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

Hybrid baryons in QCD

In this study, we present the first comprehensive study of hybrid baryons using lattice QCD methods. Using a large basis of composite QCD interpolating fields we extract an extensive spectrum of baryon states and isolate those of hybrid character using their relatively large overlap onto operators which sample gluonic excitations. We consider the spectrum of Nucleon and Delta states at several quark masses finding a set of positive parity hybrid baryons with quantum numbers $N_{1/2^+},\,N_{1/2^+},\,N_{3/2^+},\, N_{3/2^+},\,N_{5/2^+},\,$ and $\Delta_{1/2^+},\, \Delta_{3/2^+}$ at an energy scale above the first band of `conventional' excited positive parity baryons. This pattern of states is compatible with a color octet gluonic excitation having $J^{P}=1^{+}$ as previously reported in the hybrid meson sector and with a comparable energy scale for the excitation, suggesting a common bound-state construction for hybrid mesons and baryons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Baryon properties in the relativistic quark model

Properties of heavy and strange baryons are investigated in the framework of the relativistic quark-diquark picture. It is based on the relativistic quark model of hadrons, which was previously successfully applied for the calculation of meson properties. It is assumed that two quarks in a baryon form a diquark and baryon is considered as the bound quark-diquark system. The relativistic effects and diquark internal structure are consistently taken into account. Calculations are performed up to rather high orbital and radial excitations of heavy and strange baryons. On this basis the Regge trajectories are constructed. The rates of semileptonic decays of heavy baryons are calculated. The obtained results agree well with available experimental data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2019

Constraints on Cosmology and Baryonic Feedback with the Deep Lens Survey Using Galaxy–Galaxy and Galaxy–Mass Power Spectra

We present cosmological parameter measurements from the Deep Lens Survey (DLS) using galaxy–mass and galaxy–galaxy power spectra in the multipole range ℓ = 250–2000. We measure galaxy–galaxy power spectra from two lens bins centered at z ~ 0.27 and 0.54 and galaxy–mass power spectra by cross-correlating the positions of galaxies in these two lens bins with galaxy shapes in two source bins centered at z ~ 0.64 and 1.1. We marginalize over a baryonic feedback process using a single-parameter representation and a sum of neutrino masses, as well as photometric redshift and shear calibration systematic uncertainties. For a flat ΛCDM cosmology, we determine ${S}_{8}\equiv {\sigma }_{8}\sqrt{{{\rm{\Omega }}}_{m}/0.3}={0.810}_{-0.031}^{+0.039}$, in good agreement with our previous DLS cosmic shear and the Planck cosmic microwave background (CMB) measurements. Without the baryonic feedback marginalization, S 8 decreases by $\sim 0.05$ because the dark-matter-only power spectrum lacks the suppression at the highest ℓ values owing to active galactic nucleus (AGN) feedback. Together with the Planck CMB measurements, we constrain the baryonic feedback parameter to ${A}_{\mathrm{baryon}}={1.07}_{-0.39}^{+0.31}$, which suggests an interesting possibility that the actual AGN feedback might be stronger than the recipe used in the OverWhelmingly Large cosmological hydrodynamical Simulations. The interpretation is limited by the validity of the baryonic feedback simulation and the one-parameter representation of the effect.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

Cosmic Reionization on Computers: Baryonic Effects on Halo Concentrations during the Epoch of Reionization

Baryons both increase halo concentration through adiabatic contraction and expel mass through feedback processes. However, it is not well understood how the radiation fields prevalent during the epoch of reionization affect the evolution of concentration in dark matter halos. We investigate how baryonic physics during the epoch of reionization modify the structure of dark matter halos in the Cosmic Reionization On Computers (CROC) simulations. We use two different measures of halo concentration to quantify the effects. We compare concentrations of halos matched between full-physics simulations and dark-matter-only simulations with identical initial conditions between 5 ≤ z ≤ 9. Baryons in full-physics simulations do pull matter toward the center, increasing the maximum circular velocity compared to dark-matter-only simulations. However, their overall effects are much less than if all the baryons were simply centrally concentrated indicating that heating processes efficiently counteract cooling effects. Finally, we show that the baryonic effects on halo concentrations at z ≈ 5 are relatively insensitive to environmental variations of reionization history. These results are pertinent to models of galaxy–halo connection during the epoch of reionization.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2026

Galaxy Size and Rotation Curve Diversity in ΛCDM with Baryons

The observed rotation curves of dwarf galaxies exhibit significant diversity at fixed halo mass, challenging galaxy formation within the cold dark matter (CDM) model. Previous cosmological galaxy formation simulations with baryonic physics fail to reproduce the full diversity of rotation curves, suggesting that there is a flaw in baryonic feedback models, observational bias, or that an alternative to CDM must be invoked. In this work, we use the Marvelous Massive Dwarf zoom-in simulations, a suite of high-resolution dwarf simulations with M 200 ∼ 10 10 –10 11 M ⊙ and M * ∼ 10 7 –10 9 M ⊙ , designed to target the mass range where the galaxy rotation curve diversity is maximized, i.e., between and 100 km s −1 . We add to this a set of low-mass galaxies from the Marvel Dwarf Zoom Volumes to extend the galaxy mass range to lower values. Our fiducial star formation and feedback models produce simulated dwarfs with a broader range of rotation curve shapes, similar to observations. These simulations both create dark matter cores via baryonic feedback, reproducing the slower-rising rotation curves, while also allowing for compact galaxies and steeply rising rotation curves. Our simulated dwarfs also reproduce the observed size–M * relation, including scatter, producing both extended and compact dwarfs for the first time in simulated field dwarfs. However, the slowly rising and high baryon mass fraction, as well as the steeply rising and low baryon mass fraction, remain missing. We explore star formation and feedback models and conclude that previous simulations may have had feedback that was too strong to produce compact dwarfs.

Cruz, Akaxia [Flatiron Institute, New York, NY (Un↗

NASA NTRS1971

Properties of hadron matter. II - Dense baryon matter and neutron stars.

In this article we have provided certain details of a nuclear-matter computation, based on the Brueckner-Bethe-Goldstone theory of nuclear reaction, which leads to an equation of state for matter in the density region of 10 to 500 trillion g/cu cm. We also explore the possibilities that at very high baryon densities or for very short baryon separations, the net baryon-baryon interaction may be negligible so that the results of dynamical models, like the statistical bootstrap model and the dual-resonance model, may be applicable to the study of dense baryon matter. Several plausible equations of state are constructed, and their effect on the limiting mass of the neutron star is examined.

Leung, Y. C.↗

DOE OSTI2013

Analysis of Lattice Baryon Masses in 1/Nc expansion

The 1/Nc expansion of QCD is a perturbative and successful framework for the phenomenology of ground state and excited state baryons. As proposed in [1], it is a systematic expansion in powers of 1/Nc and a good approximation, qualitatively and quantitatively, when Nc=3. The 1/Nc expansion has been applied to the ground state baryons including studies of SU(6) spin-flavor symmetry in [2]. A framework was suggested in [3] for excited baryons based on the 1/Nc expansion was implemented and analyzed with the physical masses from the Particle Data Group. And a successful calculation of the spin identified spectrum of Nucleons and Deltas has been carried out in lattice QCD [4]. Using mass operators organized according to the 1/Nc expansion, the analysis of lattice baryon masses has been completed for the negative parity baryons in the multiplet [70,1]? of the SU(6)×O(3) representation, and results for that multiplet and the rest of the multiplets will be presented in this talk.\\[4pt] [1] G. 'tHooft Nucl.Phys.B72, 461(1974).\\[0pt] [2] R.F. Dashen, E.E. Jenkins, and A.V. Manohar Phys.Rev.D51 (1995).\\[0pt] [3] C.E. Carlson, C.D. Carone, J.L. Goity, R.F. Lebed Phys.Rev.D59 (1999).\\[0pt] [4] R.G. Edwards, J.J. Dudek, D.G. Richards, S.J. Wallace Phys.Rev.D84 (2011).

Fernando, Ishara↗

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↗