SEARCH · Engineering Papers

Results for “ISOSPIN”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20

All sources NASA NTRS DOE OSTI

DOE OSTI2016

Measurement of the decay B → D ℓ ν ℓ in fully reconstructed events and determination of the Cabibbo-Kobayashi-Maskawa matrix element | V c b |

We present a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| using the decay B → Dℓν ℓ (ℓ = e,μ) based on 711 fb –1 of e + e – → Υ(4S) data recorded by the Belle detector and containing 772 × 10 6 BB¯ pairs. Here, one B meson in the event is fully reconstructed in a hadronic decay mode, while the other, on the signal side, is partially reconstructed from a charged lepton and either a D + or D 0 meson in a total of 23 hadronic decay modes. The isospin-averaged branching fraction of the decay B → Dℓν ℓ is found to be B(B 0 → D – ℓ + ν ℓ ) = (2.31 ± 0.03(stat) ± 0.11(syst))%. Analyzing the differential decay rate as a function of the hadronic recoil with the parametrization of Caprini, Lellouch, and Neubert and using the form-factor prediction G(1) = 1.0541 ± 0.0083 calculated by FNAL/MILC, we obtain η EW |V cb | = (40.12 ± 1.34) × 10 –3 , where ηEW is the electroweak correction factor. Alternatively, assuming the model-independent form-factor parametrization of Boyd, Grinstein, and Lebed and using lattice QCD data from the FNAL/MILC and HPQCD collaborations, we find η EW |V cb | = (41.10 ± 1.14) × 10 –3 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Neutrino masses and scalar singlet dark matter

Here We propose a simple extension of the Standard Model (SM) which has a viable dark matter (DM) candidate and can explain the generation of tiny neutrino masses. The DM is an electroweak (EW) singlet scalar S, odd under an imposed exact Z 2 symmetry, that interacts with the SM through the “Higgs portal” coupling, while all other particles are even under Z 2 . The model also has an EW isospin 3/2 scalar Δ and a pair of EW isospin vectors Σ and $\bar{Σ}$, which are responsible for generating tiny neutrino mass via the effective dimension-seven operator. Thanks to the additional interactions with Δ, the scalar singlet DM S survives a large region of parameter space by relic density constraints from WMAP/Planck and direct search bounds from updated LUX data. Constraints on the model from the LHC are also discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2019

Searching for Flavor Dependence in Nuclear Quark Behavior

The observed correlation between the EMC effect and the contribution of short-range correlations (SRCs) in nuclei suggests that the modification of the quark distributions of bound protons and neutrons might occur within SRCs. This raises the possibility that the EMC effect may have an isospin dependence arising from the np dominance of SRCs. We discuss previous attempts to test this possibility and perform a new analysis of existing data. We find no experimental support for the observation of an isospin dependence of the EMC effect.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

First Observation of a Doubly Charged Tetraquark and Its Neutral Partner

A combined amplitude analysis is performed for the decays $B^0$ → $\overline{D}$ 0 $D_s^+$$π^–$ and $B^+$ → $D^–$$D_s^+$$π^+$, which are related by isospin symmetry. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV. The full data sample corresponds to an integrated luminosity of 9 fb –1 . Two new resonant states with masses of 2.908 ± 0.011 ± 0.020 GeV and widths of 0.136 ± 0.023 ± 0.013 GeV are observed, which decay to $D_s^+$$π^+$ and $D_s^+$$π^–$ respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content [c$\overline{s}$u$\overline{d}$], and the latter state is a neutral tetraquark composed of [c$\overline{s}$$\overline{u}$d] quarks. Both states are found to have spin-parity of 0 + , and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Evidence of a $J/$$\psi$$K_S^0$ Structure in $B^0$ → $J/$$\psi$$\phi$$K_S^0$

An amplitude analysis of $B^0$ → $J/$$\psi$$\phi$$K_S^0$ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 9 fb –1 , collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. Evidence with a significance of 4.0 standard deviations of a structure in the $J/$$\psi$$K_S^0$ system, named $T_{ψs1}^{θ}$⁢⁢(4000) 0 , is seen, with its mass and width measured to be 3991$_{–10 –17}^{+12 +9}$ MeV/⁢c 2 and 105$_{–25 –23}^{+29 +17}$ MeV, respectively, where the first uncertainty is statistical and the second systematic. The $T_{ψs1}^{θ}$⁢⁢(4000) 0 state is likely to be the isospin partner of the $T_{ψs1}^{θ}$⁢⁢(4000) + state, previously observed in the $J/ψK^+$ system of the $B^+$→$J/ψ$$\phi$$K^+$ decay. When isospin symmetry for the charged and neutral $T_{ψs1}^{θ}$⁢⁢(4000) states is assumed, the signal significance increases to 5.4 standard deviations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Electrical Control of Spin and Valley in Spin-Orbit Coupled Graphene Multilayers

Electrical control of magnetism has been a major technological pursuit of the spintronics community, owing to its far-reaching implications for data storage and transmission. Here, in this study, we propose and analyze a new mechanism for electrical switching of isospin, using chiral-stacked graphene multilayers, such as Bernal bilayer graphene or rhombohedral trilayer graphene, encapsulated by transition metal dichalcogenide (TMD) substrates. Leveraging the proximity-induced spin-orbit coupling from the TMD, we demonstrate electrical switching of correlation-induced spin and/or valley polarization, by reversing a perpendicular displacement field or the chemical potential. We substantiate our proposal with both analytical arguments and self-consistent Hartree-Fock numerics. Finally, we illustrate how the relative alignment of the TMDs, together with the top and bottom gate voltages, can be used to selectively switch distinct isospin flavors, putting forward correlated Van der Waals heterostructures as a promising platform for spintronics and valleytronics.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Precision Mass Measurement of the Proton Dripline Halo Candidate 22 Al

Here, we report the first mass measurement of the proton-halo candidate 22 Al performed with the low energy beam ion trap facility’s 9.4 T Penning trap mass spectrometer at facility for rare isotope beams. This measurement completes the mass information for the lightest remaining proton-dripline nucleus achievable with Penning traps. 22 Al has been the subject of recent interest regarding a possible halo structure from the observation of an exceptionally large isospin asymmetry [J. Lee et al ., Large isospin asymmetry in Si22/O22 Mirror Gamow-Teller transitions reveals the halo structure of 22 Al , Phys. Rev. Lett. 125, 192503 (2020).]. The measured mass excess value of ME=18 092.5⁢(3) keV, corresponding to an exceptionally small proton separation energy of 𝑆𝑝=100.4⁢(8) keV, is compatible with the suggested halo structure. Our result agrees well with predictions from 𝑠⁢𝑑-shell USD Hamiltonians. While USD Hamiltonians predict deformation in the 22 Al ground state with minimal 1⁢𝑠 1/2 occupation in the proton shell, a particle-plus-rotor model in the continuum suggests that a proton halo could form at large quadrupole deformation. These results emphasize the need for a charge radius measurement to conclusively determine the halo nature.

binding energy↗

DOE OSTI2025

Long-Distance Window of the Hadronic Vacuum Polarization for the Muon g − 2

We provide the first calculation of the Euclidean long-distance window of the isospin-symmetric light-quark connected contribution to the hadronic vacuum polarization for the muon g − 2 and find a μ LD , iso , conn , ud = 411.4 ( 4.3 ) ( 2.4 ) × 10 − 10 . We also provide the currently most precise calculation of the total isospin-symmetric light-quark connected contribution, a μ iso , conn , ud = 666.2 ( 4.3 ) ( 2.5 ) × 10 − 10 in the BMW20 world, which is more than 4 σ larger compared to the data-driven estimates of Boito [] and 1.7 σ larger compared to the lattice QCD result of BMW20. Published by the American Physical Society 2025

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Comparison between ūu and d̄d productions by the γp → π{sup −}Δ{sup ++} and π{sup +}Δ{sup 0} reactions at forward π angles at E{sub γ} = 1.5–3.0 GeV

Photoproduction reactions are dominated by isospin rules. In the case of πΔ photoproduction on the proton at forward π angles, the exchange of isospin = 1 meson(π or ρ) in the t-channel is the most dominant reaction mechanism, which is considered to give a cross section ratio σ(π{sup +}Δ{sup 0})/σ(π{sup −}Δ{sup ++}) of 1/3. The cross section ratio has not been measured precisely experimentally. We present preliminary results for the cross section ratio at E{sub γ} = 1.5–3.0 GeV. Larger ratios than 1/3 measured by our experiment at LEPS/SPring-8 suggest that the d̄d productions are enhanced compared with the ūu productions in the photoproduction reactions on the proton.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Wigner SU(4) symmetry, clustering, and the spectrum of $$^{12}$$C

Abstract We present lattice calculations of the low-lying spectrum of $$^{12}$$ 12 C using a simple nucleon–nucleon interaction that is independent of spin and isospin and therefore invariant under Wigner’s SU(4) symmetry. We find strong signals for all excited states up to $$\sim 15$$ ∼ 15 MeV above the ground state, and explore the structure of each state using a large variety of $$\alpha $$ α cluster and harmonic oscillator trial states, projected onto given irreducible representations of the cubic group. We are able to verify earlier findings for the $$\alpha $$ α clustering in the Hoyle state and the second $$2^+$$ 2 + state of $$^{12}$$ 12 C. The success of these calculations to describe the full low-lying energy spectrum using spin-independent interactions suggest that either the spin-orbit interactions are somewhat weak in the $$^{12}$$ 12 C system, or the effects of $$\alpha $$ α clustering are diminishing their influence. This is in agreement with previous findings from ab initio shell model calculations.

Shen, Shihang (ORCID:0000000280516466)↗

DOE OSTI2023

The Jefferson Lab tritium program of nucleon and nuclear structure measurements

In this work a series of experiments were performed in Hall A of Jefferson Lab in 2018 that used a novel tritium and helium-3 target system. These experiments took advantage of the isospin symmetry of these mirror nuclei to make precise measurements of isospin dependence in both nucleon and nuclear structure. We summarize here the design and properties of these cells, the physics measurements that have been published, and results currently under analysis from this program.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Searching for three-nucleon short-range correlations

Electron scattering measurements from high-momentum nucleons in nuclei at SLAC and Jefferson Lab (JLab) have shown that these nucleons are generally associated with two-nucleon short-range correlations (2N-SRCs). These SRCs are formed when two nucleons in the nucleus interact at short distance via the strong tensor attraction or repulsive core of the NN potential. A series of measurements at JLab have mapped out the A dependence and isospin dependence of 2N-SRCs, and have begun to map out their momentum structure. However, we do not yet know if 3N-SRCs, similar high-momentum configurations of three nucleons, play an important role in nuclei. Here, we summarize here previous attempts to isolate 3N-SRCs, go over the limitations of these previous attempts, and discuss the present and near-term prospects for searching for 3N-SRCs, mapping out their A dependence in nuclei, and constraining their isospin and momentum structure.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Measurement of Excited Hyperons in Photoproduction at CLAS

Measurement results of photoproduced excited hyperon states using the CLAS detector at Jefferson Lab are shown. The invariant mass distribution of the {Lambda}(1405) has recently been shown to be different for each of the three Sigma pi channels that it decays to, showing that there is prominent interference between the isospin I=0 and I=1 isospin amplitudes. Measurements of the differential and total cross sections of the three hyperons {Lambda}(1405), {Sigma}{sup 0}(1385), and Lambda(1520) are presented and compared. Prospects of future studies using a 12 GeV beam with the GlueX detector are briefly given.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Halo-Independent Comparison of Direct Dark Matter Detection Data

We review the halo-independent formalism that allows comparing data from different direct dark matter detection experiments without making assumptions on the properties of the dark matter halo. We apply this method to spin-independent WIMP-nuclei interactions, for both isospin-conserving and isospin-violating couplings, and to WIMPs interacting through an anomalous magnetic moment.

Del Nobile, Eugenio↗

DOE OSTI2019

Deep inelastic scattering from A = 3 nuclei: Nucleon structure and the EMC effect

The MARATHON experiment ran at Jefferson Laboratory in 2018, measuring deep inelastic scattering of 10.6 GeV electrons from the proton (p), deuterium (D), tritium ( 3 H), and helium-3 ( 3 He). MARATHON's experimental observables are cross section ratios, most notably 3 H/ 3 He. This ratio of mirror nuclei is used for a novel extraction of the nucleon structure function ratio $F^n_2$ /$F^p_2$ with minimal nuclear corrections. Determining leading-order $F^n_2$ /$F^p_2$ at high x provides important constrains on the ratio of nucleon valence quark distributions d/u. The ratios 3 H/D and 3 He/D allow a determination of the EMC effect in the lightest nuclei sensitive to possible isospin dependence of nuclear effects. Lastly, the D/p ratio allows a comparison of the MARATHON experiment to SLAC measurements, and provides data to which the A = 3 ratios can be renormalized. The MARATHON results provide new constraints on d/u. Additionally, the results emphasize the importance of higher-order effects in extracting $F^n_2$ /$F^p_2$ from DIS measurements, and can help constrain said effects. In the renormalization scheme applied in the MARATHON analysis, no significant isospin dependence of the EMC effect is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2015

Exclusive Single Pion off the Proton: Results from CLAS

Exclusive meson electroproduction off protons is a powerful tool to probe the effective degrees of freedom in excited nucleon states at the varying distance scale where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance. During the past decade, the CLAS collaboration has executed a broad experimental program to study the excited states of the proton using polarized electron beam and both polarized and unpolarized proton targets. The measurements covered a broad kinematic range in the invariant mass $W$ and photon virtuality $Q^2$ with nearly full coverage in polar and azimuthal angles in the hadronic CM system. As results, several low-lying nucleon resonance states in particular from pion threshold to $W < 1.6$ GeV have been explored. These include $\Delta$(1232)$\frac{3}{2}^+$, $N(1440)\frac{1}{2}^+$, $N(1520)\frac{3}{2}^-$, and $N(1535)\frac{1}{2}^-$ states. In addition, we recently published the differential cross sections and helicity amplitudes of the reaction $\gamma^*p\to n\pi^+$ at higher $W$ (1.6 to 2.0 GeV) which are the $N(1675)\frac{5}{2}^-$, $N(1680)\frac{5}{2}^+$, and $N(1710)\frac{1}{2}^+$ states. These excited states with isospin $1/2$ and with masses near 1.7 GeV can be accessed in single $n\pi^+$ production as there are no isospin $3/2$ states present in this mass range with the same spin-parity assignments. As a result, I will briefly discuss these states from CLAS results of the single charged pion electroproduction data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2013

Hadron Scattering Amplitudes From Lattice QCD

Lattice QCD offers a controlled computation approach to non-perturbative calculations in QCD. It should be possible to compute hadron-hadron scattering at the quark-gluon level, however as calculations must be performed in a finite Euclidean volume, it is not obvious that there is the required continuum of scattering states. I will give a pedagogic introduction to the relationship between the discrete spectrum in a finite-volume quantum theory and the infinite-volume scattering amplitudes. I will show recent results on elastic $\pi\pi$ scattering in the repulsive isospin=2 and resonant isospin=1 channels and discuss ongoing work to deal with inelastic scattering processes.

Dudek, Jozef↗

DOE OSTI2013

Baryon spectroscopy with CLAS

Klein, Franz↗