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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

First observation of γ γ → p p ¯ K + K - and search for exotic baryons in p K systems

The process γ γ → p p ¯ K + K - and its intermediate processes are measured for the first time using a 980 fb - 1 data sample collected with the Belle detector at the KEKB asymmetric-energy e + e - collider. The production of p p ¯ K + K - and a Λ ( 1520 ) 0 ( Λ ¯ ( 1520 ) 0 ) signal in the p K - ( p ¯ K + ) invariant mass spectrum are clearly observed. However, no evidence for an exotic baryon near 1540 MeV / c 2 , denoted as Θ ( 1540 ) 0 ( Θ ¯ ( 1540 ) 0 ) or Θ ( 1540 ) + + ( Θ ( 1540 ) - -- ), is seen in the p K - ( p ¯ K + ) or p K + ( p ¯ K - ) invariant mass spectra. Cross sections for γ γ → p p ¯ K + K - , Λ ( 1520 ) 0 p ¯ K + + c . c . and the products σ ( γ γ → Θ ( 1540 ) 0 p ¯ K + + c . c . ) B ( Θ ( 1540 ) 0 → p K - ) and σ ( γ γ → Θ ( 1540 ) + + p ¯ K - + c . c . ) B ( Θ ( 1540 ) + + → p K + ) are measured. We also determine upper limits on the products of the χ c 0 and χ c 2 two-photon decay widths and their branching fractions to p p ¯ K + K - at the 90% credibility level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Bispectrum as baryon acoustic oscillation interferometer

The galaxy bispectrum, measuring excess clustering of galaxy triplets, offers a probe of dark energy via baryon acoustic oscillations (BAOs). However up to now it has been severely underused due to the combinatorically explosive number of triangles. Here we exploit interference in the bispectrum to identify triangles that amplify BAOs. Here, this approach reduces the computational cost of estimating covariance matrices, offers an improvement in BAO constraints equivalent to lengthening BOSS by 30% and simplifies adding bispectrum BAO information to future large-scale redshift survey analyses.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

First Observation of the Doubly Cabibbo-Suppressed Decay of a Charmed Baryon: Λ c + → p K + π -

We report the first observation of the decay Λ c + → p K + π - using a 980 fb - 1 data sample collected by the Belle detector at the KEKB asymmetric-energy e + e - collider. This is the first observation of a doubly Cabibbo-suppressed decay of a charmed baryon. We measure the branching ratio of this decay with respect to its Cabibbo-favored counterpart to be B ( Λ c + → p K + π - ) / B ( Λ c + → p K - π + ) = ( 2.35 ± 0.27 ± 0.21 ) × 10 - 3 , where the uncertainties are statistical and systematic, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Visible and dark matter from a first-order phase transition in a baryon-symmetric universe

The similar cosmological abundances observed for visible and dark matter suggest a common origin for both. By viewing the dark matter density as a dark-sector asymmetry, mirroring the situation in the visible sector, we show that the visible and dark matter asymmetries may have arisen simultaneously through a first-order phase transition in the early universe. The additional scalar particles in the theory can mix with the standard Higgs boson and provide other striking signatures.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Exploring QCD phase diagram at vanishing baryon density on the lattice

Here, I report on the current status of QCD phase diagram at vanishing baryon density. I focus on the QCD phase diagram with three degenerate quark flavor using Highly Improved Staggered Quarks on NT = 6 lattices. No evidence of a first order phase transition in the pion mass window of 80 $\lesssim$ m π $\lesssim$ 230 MeV is found. The pion mass at the critical point where the chiral first order phase transition ends is estimated to be m π c $\lesssim$ 45 MeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Measuring the Hubble constant and spatial curvature from supernova apparent magnitude, baryon acoustic oscillation, and Hubble parameter data

Cosmic microwave background (CMB) anisotropy (spatial inhomogeneity) data provide the tightest constraints on the Hubble constant, matter density, spatial curvature, and dark energy dynamics. Other data, sensitive to the evolution of only the spatially homogeneous part of the cosmological model, such as Type Ia supernova apparent magnitude, baryon acoustic oscillation distance, and Hubble parameter measurements, can be used in conjunction with the CMB data to more tightly constrain parameters. Recent joint analyses of CMB and such non-CMB data indicate that slightly closed spatial hypersurfaces are favored in nonflat untilted inflation models and that dark energy dynamics cannot be ruled out, and favor a smaller Hubble constant. Here, we show that the constraints that follow from these non-CMB data alone are consistent with those that follow from the CMB data alone and so also consistent with, but weaker than, those that follow from the joint analyses of the CMB and non-CMB data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Search for a hidden strange baryon-meson bound state from Φ production in a nuclear medium

We investigate the hidden strange light baryon-meson system. With the resonating-group method, two bound states, η'-N and Φ-N, are found in the quark delocalization color screening model. Focusing on the Φ-N bound state around 1950 MeV, we obtain the total decay width of about 4 MeV by calculating the phase shifts in the resonance scattering processes. To study the feasibility of an experimental search for the Φ-N bound state, we perform a Monte Carlo simulation of the bound state production with an electron beam and a gold target. In the simulation, we use the CLAS12 detector with the Forward Tagger and the BONUS12 detector in Hall B at Jefferson Lab. Both the signal and the background channels are estimated. We demonstrate that the signal events can be separated from the background with some momentum cuts. Therefore it is feasible to experimentally search for the Φ-N bound state through the near threshold Φ meson production from heavy nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Studies of charmed strange baryons in the Λ D final state at Belle

In this report, we discuss the discovery of Ξ c ( 3055 ) 0 , observed by its decay into the final-state Λ D 0 , and present the first observation and evidence of the decays of Ξ c ( 3055 ) + and Ξ c ( 3080 ) + into Λ D + . Furthermore, we perform a combined analysis of the Λ D + with the Σ c + + K - and Σ c * + + K - decay modes to measure the ratios of branching fractions, masses and widths with improved accuracy. We measure the ratios of branching fractions B ( Ξ c ( 3055 ) + → Λ D + ) / B ( Ξ c ( 3055 ) + → Σ c + + K - ) = 5.09 ± 1.01 ± 0.76 , B ( Ξ c ( 3080 ) + → Λ D + ) / B ( Ξ c ( 3080 ) + → Σ c + + K - ) = 1.29 ± 0.30 ± 0.15 , and B ( Ξ c ( 3080 ) + → Σ c * + + K - ) / B ( Ξ c ( 3080 ) + → Σ c + + K - ) = 1.07 ± 0.27 ± 0.04 , where the uncertainties are statistical and systematic. The analysis is performed using a 980 fb - 1 data sample collected with the Belle detector at the KEKB asymmetric-energy e + e - collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Light Baryon Spectroscopy at Jefferson Lab: What have we learned about excited baryons?

Nucleons are complex systems of confined quarks and gluons and exhibit the characteristic spectra of excited states. These states serve as an excellent probe of quantum chromodynamics (QCD), the fundamental theory of strong interaction. Highly-excited states are sensitive to the details of quark confinement, which is only poorly understood within QCD. This is the regime of non-perturbative QCD and it is one of the key issues in hadronic physics to identify the corresponding relevant degrees of freedom and the effective forces between them. In recent years, lattice-QCD has made significant progress toward understanding the spectra of hadrons. On the experimental side, high-energy electrons and photons are a remarkably clean probe of hadronic matter, providing a microscope for examining atomic nuclei and the strong nuclear force. For more than a decade, laboratories worldwide have accumulated data for such investigations, resulting in a number of surprising discoveries and contributing to our understanding of the nucleon, its underlying quark structure, and the dynamics of the strong interaction. Current experimental efforts utilize highly-polarized frozen-spin (butanol) targets and deuterium targets in combination with polarized photon beams. These are important steps toward so-called complete experiments that will allow us to unambiguously determine the scattering amplitudes in the underlying reactions and to identify resonance contributions. In my talk, I will give an overview of the excited baryon program at Jefferson Lab and I will discuss recent results from (double-)polarization experiments.

Crede, Volker↗
DOE OSTI2017

Impact of baryonic physics on intrinsic alignments

We explore the effects of specific assumptions in the subgrid models of star formation and stellar and AGN feedback on intrinsic alignments of galaxies in cosmological simulations of "MassiveBlack-II" family. Using smaller volume simulations, we explored the parameter space of the subgrid star formation and feedback model and found remarkable robustness of the observable statistical measures to the details of subgrid physics. The one observational probe most sensitive to modeling details is the distribution of misalignment angles. We hypothesize that the amount of angular momentum carried away by the galactic wind is the primary physical quantity that controls the orientation of the stellar distribution. Finally, our results are also consistent with a similar study by the EAGLE simulation team.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Weak Production of Strange and Charmed Ground-State Baryons in Nuclei

We present results for the quasielastic weak production of Λ and Σ hyperons induced by ν¯ scattering off nuclei in the kinematical region of interest for accelerator neutrino experiments. We employ realistic hole spectral functions and we describe the propagation of the hyperons in the nuclear medium by means of a Monte Carlo cascade. The latter strongly modifies the kinematics and the relative production rates of the hyperons, leading to a nonvanishing Σ+ cross section, to a sizable enhancement of the Λ production and to a drastic reduction of the Σ0 and Σ− distributions. We also compute the quasielastic weak Λc production cross section, paying special attention to estimate the uncertainties induced by the model dependence of the vacuum n→Λc weak matrix element. In this regard, the recent BESIII measurements of the branching ratios of Λc→Λl+νl (l=e,μ) are used to benchmark the available theoretical predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗