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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Shallow Bound States and Hints for Broad Resonances with Quark Content b ¯ c ¯ u d in B − D ¯ and B * − D ¯ Scattering from Lattice QCD

We present the first determination of the energy dependence of the B − D ¯ and B * − D ¯ isospin-0, S -wave scattering amplitudes both below and above the thresholds using lattice QCD, which allows us to investigate rigorously whether mixed bottom-charm b ¯ c ¯ u d tetraquarks exist as bound states or resonances. The scattering phase shifts are obtained using Lüscher’s method from the energy spectra in two different volumes. To ensure that no relevant energy level is missed, we use large, symmetric 7 × 7 and 8 × 8 correlation matrices that include, at both source and sink, B ( * ) − D ¯ scattering operators with the lowest three or four possible back-to-back momenta in addition to local b ¯ c ¯ u d operators. We fit the energy dependence of the extracted scattering phase shifts using effective-range expansions. We observe sharp peaks in the B ( * ) − D ¯ scattering rates close to the thresholds, which are associated with shallow bound states, either genuine or virtual, a few MeV or less below the B ( * ) − D ¯ thresholds. In addition, we find hints for resonances with masses of order 100 MeV above the thresholds and decay widths of order 200 MeV. Published by the American Physical Society 2024

Alexandrou, Constantia↗
DOE OSTI2023

First observation of B → $\bar{D}$ 1 (→ $\bar{D}$ π + π - ) $\ell$ + ν $\ell$ and measurement of the B → $\bar{D}$ (*) π$\ell$ + ν $\ell$ and B → $\bar{D}$ (*) π + π - $\ell$+ ν $\ell$ branching fractions with hadronic tagging at Belle

We report measurements of the ratios of branching fractions for B → $\bar{D}$(*) π$\ell$+ v $\ell$ and B → $\bar{D}$(*)π + π - $\ell$ + v $\ell$ relative to B → $\bar{D}$*$\ell$ + v $\ell$ decays with $\ell$ = e, μ. These results are obtained from a data sample that contains 772 × 10 6 $B\bar{B}$ pairs collected near the $\Upsilon$(4S) resonance with the Belle detector at the KEKB asymmetric energy e + e - collider.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Measurement of the branching fraction and CP asymmetry of B 0 →π 0 ⁢π 0 decays using 198×1⁢0 6 $B\overline{B}$ pairs in Belle II data

We report measurements of the branching fraction and C P asymmetry in B 0 → π 0 π 0 decays reconstructed at Belle II in an electron-positron collision sample containing 198 × 10 6 B B ¯ pairs. We measure a branching fraction B ( B 0 → π 0 π 0 ) = ( 1.38 ± 0.27 ± 0.22 ) × 10 - 6 and a C P asymmetry A C P ( B 0 → π 0 π 0 ) = - 0.14 ± 0.46 ± 0.07 , where the first uncertainty is statistical and the second is systematic.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

E × B flow driven electron temperature bifurcation in a closed slot divertor with ion B × ∇ B away from the X-point in the DIII-D tokamak

An electron temperature bifurcation is observed in the small angle slot divertor, which has been developed to enhance neutral cooling across the divertor target by coupling a closed slot structure with appropriate target shaping. Experiments in the DIII-D tokamak and associated SOLPS-ITER modeling with full drifts find a strong interplay between drifts and divertor geometry on divertor dissipation. The coupling of divertor geometry and drift flows can strongly affect the path towards divertor detachment onset as the plasma density is raised. With the strike point on the inner slanted surface and ion B × ∇B away from the magnetic X-point, bifurcative transitions were observed with sharp decrease of T e towards detachment onset both experimentally and computationally. This differs from the situation for the open divertor where the T e cliff was only observed for ion B × ∇B towards the X-point. SOLPS-ITER modeling with full drifts demonstrates that the magnitude of the E × B drift flow is comparable with the main plasma flow. The reversal of both the poloidal and radial E × B flows near the strike point leads to rapid density accumulation right near the separatrix, which results in bifurcative step transition of divertor conditions with cold plasma across the entire divertor target plate. Furthermore, these results indicate that the interplay between geometry and drifts should be fully taken into account in future fusion reactor divertor designs.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

$t\bar{t}b\bar{b}$ at the LHC: on the size of corrections and b -jet definitions

We report on the calculation of the next-to-leading order QCD corrections to the production of a $t\bar t$ pair in association with two heavy-flavour jets. We concentrate on the di-lepton $t\bar t$ decay channel at the LHC with $\sqrt{s}$ = 13 TeV. The computation is based on pp → $e^+ν_eμ^-\bar{ν}_μb\bar{b}b\bar{b}$ matrix elements and includes all resonant and non-resonant diagrams, interferences and off-shell effects of the top quark and the W gauge boson. As it is customary for such studies, results are presented in the form of inclusive and differential fiducial cross sections. We extensively investigate the dependence of our results upon variation of renormalisation and factorisation scales and parton distribution functions in the quest for an accurate estimate of the theoretical uncertainties. We additionally study the impact of the contributions induced by the bottom-quark parton density. Results presented here are particularly relevant for measurements of $t\bar{t}H(H → b\bar{b})$ and the determination of the Higgs coupling to the top quark. In addition, they might be used for precise measurements of the top-quark fiducial cross sections and to investigate top-quark decay modelling at the LHC.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Observation of $Λ^0_b$ → $D^+ρπ^-π^-$ and $Λ^0_b$ → $D^{*+}ρπ^-π^-$ decays

The multihadron decays $Λ^0_b$ → $D+ρπ-π-$ and $Λ^0_b$ → $D^*+ρπ-π-$ are observed in data corresponding to an integrated luminosity of 3 fb -1 , collected in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV by the LHCb detector. Using the decay $Λ^0_b$ → $Λ^+_cπ^+π^-π^-$ as a normalisation channel, the ratio of branching fractions is measured to be $\frac {\mathcal{B} ( Λ^0_b → D^+ρπ^-π^-)} {\mathcal{B} (Λ^0_b → Λ^0_cπ^+π^-π^-)}$ x $\frac{\mathcal{B} (D^+ → K^-π^+π^+)} {\mathcal{B}(Λ^o_c → ρK^-π^-)}$ = (%.35 ± 0.21 ± 0.16)%, where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for the $Λ^0_b$ → $D^{*+}ρπ^-π^-$ and $Λ^0_b$ → $D^+ρπ^-π^-$ decays is found to be $\frac {\mathcal{B} ( Λ^0_b → D^{*+}ρπ^-π^-)} {\mathcal{B} (Λ^0_b → D^+ρπ^-π^-)}$ X ($\mathcal{B} (D^{*+}→ D^+π^0)$ + $\mathcal{B} (D^{*+}→ D^+γ)$) = (61.3 ± 4.3 ± 4.0)%.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Study of ${\mathrm{B}}_{\mathrm{c}}^{+}\to \mathrm{J}/\psi {\mathrm{D}}_{\mathrm{s}}^{+}$ and ${\mathrm{B}}_{\mathrm{c}}^{+}\to \mathrm{J}/\psi {\mathrm{D}}_{\mathrm{s}}^{\ast +}$ decays in pp collisions at $\sqrt{\mathrm{s}}$ = 13 TeV with the ATLAS detector

A study of ${B}_c^{+}\to J/\psi {D}_s^{+}$ and ${B}_c^{+}\to J/\psi {D}_s^{\ast +}$ decays using 139 fb –1 of integrated luminosity collected with the ATLAS detector from $\sqrt{s}$ = 13 TeV pp collisions at the LHC is presented. The ratios of the branching fractions of the two decays to the branching fraction of the ${B}_c^{+}$ → J/ψπ + decay are measured: $\mathcal{B}\left({B}_c^{+}\to J/\psi {D}_s^{+}\right)/\mathcal{B}\left({B}_c^{+}\to J/{\psi \pi}^{+}\right)$ = 2.76 ± 0.47 and $\mathcal{B}\left({B}_c^{+}\to J/\psi {D}_s^{\ast +}\right)/\mathcal{B}\left({B}_c^{+}\to J/{\psi \pi}^{+}\right)$ = 5.33 ± 0.96. The ratio of the branching fractions of the two decays is found to be $\mathcal{B}\left({B}_c^{+}\to J/\psi {D}_s^{\ast +}\right)/\mathcal{B}\left({B}_c^{+}\to J/\psi {D}_s^{\ast +}\right)$ = 1.93 ± 0.26. For the ${B}_c^{+}\to J/\psi {D}_s^{\ast +}$ decay, the transverse polarization fraction, Γ ±± /Γ, is measured to be 0.70 ± 0.11. The reported uncertainties include both the statistical and systematic components added in quadrature. The precision of the measurements exceeds that in all previous studies of these decays. These results supersede those obtained in the earlier ATLAS study of the same decays with $\sqrt{s}$ = 7 and 8 TeV pp collision data. A comparison with available theoretical predictions for the measured quantities is presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Bottom quark energy loss and hadronization with B + and ${\textrm{B}}_{\textrm{s}}^0$ nuclear modification factors using pp and PbPb collisions at $\sqrt{s_{\textrm{NN}}}$ = 5.02 TeV

The production cross sections of $ {\textrm{B}}_{\textrm{s}}^0 $ and B$^{+}$ mesons are reported in proton-proton (pp) collisions recorded by the CMS experiment at the CERN LHC with a center-of-mass energy of 5.02 TeV. The data sample corresponds to an integrated luminosity of 302 pb$^{−1}$. The cross sections are based on measurements of the $ {\textrm{B}}_{\textrm{s}}^0 $→ J/ψ(μ$^{+}$μ$^{−}$)ϕ(1020)(K$^{+}$K$^{−}$) and B$^{+}$→ J/ψ(μ$^{+}$μ$^{−}$)K$^{+}$ decay channels. Results are presented in the transverse momentum (p$_{T}$) range 7–50 GeV/c and the rapidity interval |y| < 2.4 for the B mesons. The measured p$_{T}$-differential cross sections of B$^{+}$ and $ {\textrm{B}}_{\textrm{s}}^0 $ in pp collisions are well described by fixed-order plus next-to-leading logarithm perturbative quantum chromodynamics calculations. Using previous PbPb collision measurements at the same nucleon-nucleon center-of-mass energy, the nuclear modification factors, R$_{AA}$, of the B mesons are determined. For p$_{T}$> 10 GeV/c, both mesons are found to be suppressed in PbPb collisions (with R$_{AA}$ values significantly below unity), with less suppression observed for the $ {\textrm{B}}_{\textrm{s}}^0 $ mesons. In this p$_{T}$ range, the R$_{AA}$ values for the B$^{+}$ mesons are consistent with those for inclusive charged hadrons and D$^{0}$ mesons. Below 10 GeV/c, both B$^{+}$ and $ {\textrm{B}}_{\textrm{s}}^0 $ are found to be less suppressed than either inclusive charged hadrons or D$^{0}$ mesons, with the $ {\textrm{B}}_{\textrm{s}}^0 $R$_{AA}$ value consistent with unity. The R$_{AA}$ values found for the B$^{+}$ and $ {\textrm{B}}_{\textrm{s}}^0 $ are compared to theoretical calculations, providing constraints on the mechanism of bottom quark energy loss and hadronization in the quark-gluon plasma, the hot and dense matter created in ultrarelativistic heavy ion collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the e + e - → $ {B}_s^0{\overline{B}}_s^0X $ cross section in the energy range from 10.63 to 11.02 GeV using inclusive $ {D}_s^{+} $ and D 0 production

We report the first measurement of the inclusive e + e - → $b\bar{b}$ → D$^±_s$ X and e + e - → $b\bar{b}$ → D 0 / $\overline{D}^0$ X cross sections in the energy range from 10.63 to 11.02 GeV. Based on these results, we determine σ(e + e - → ${B}_s^0{\overline{B}}_s^0$ X) and σ(e + e - → $B\overline{B}$ X) in the same energy range. We measure the fraction of ${B}_s^0$ events at Υ(10860) to be f s = (${22.0}_{-2.1}^{+2.0}$)%. We determine also the ratio of the ${B}_s^0$ inclusive branching fractions $\mathcal{B}$(${B}_s^0$ → D 0 / $\overline{D}^0$X)/$\mathcal{B}$(${B}_s^0$ → ${D}_s^{\pm }$X) = 0.416 ± 0.018 ± 0.092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy e + e - collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Production of b b ¯ at forward rapidity in p + p collisions at s = 510 GeV

The cross section of bottom quark-antiquark ( b b ¯ ) production in p + p collisions at s = 510 GeV is measured with the PHENIX detector at the Relativistic Heavy Ion Collider. The results are based on the yield of high mass, like-sign muon pairs measured within the PHENIX muon arm acceptance ( 1.2 < | y | < 2.2 ). The b b ¯ signal is extracted from like-sign dimuons by utilizing the unique properties of neutral B meson oscillation. We report a differential cross section of d σ b b ¯ → μ ± μ ± / d y = 0.16 ± 0.01 ( stat ) ± 0.02 ( syst ) ± 0.02 ( global ) nb for like-sign muons in the rapidity and p T ranges 1.2 < | y | < 2.2 and p T > 1 GeV / c , and dimuon mass of 5 – 10 GeV / c 2 . The extrapolated total cross section at this energy for b b ¯ production is 13.1 ± 0.6 ( stat ) ± 1.5 ( syst ) ± 2.7 ( global ) μ b . The total cross section is compared to a perturbative quantum chromodynamics calculation and is consistent within uncertainties. The azimuthal opening angle between muon pairs from b b ¯ decays and their p T distributions are compared to distributions generated using ps pythia 6, which includes next-to-leading order processes. The azimuthal correlations and pair p T distribution are not very well described by pythia calculations, but are still consistent within uncertainties. Flavor creation and flavor excitation subprocesses are favored over gluon splitting.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Prospects for ${B}_{(s)}^0 $ → π$^0$π$^0$ and ${B}_{(s)}^0 $ → ηη modes and corresponding CP asymmetries at Tera-Z

The physics potential of measuring $B^0_{(s)}$ → $π^0π^0$ and $B^0_{(s)}$ → $ηη$ decays via four-photon final states at Tera-Z phase of CEPC or FCC-ee is investigated in this paper. We propose an electromagnetic calorimeter (ECAL) with both high energy resolution and excellent separation power to efficiently reconstruct $π^0$ and $η$ from hadronic final states with high photon multiplicity. The resulting B-meson mass resolution is approximately 30 MeV, allowing 3 $σ$ separation between B 0 and $B^0_{(s)}$. With the assistance of the b-jet tagging, the relative sensitivities to B 0 → $π^0π^0$, $B^0_{(s)}$ → $π^0π^0$, B 0 → $ηη$, and $B^0_{(s)}$ → $ηη$ signal strengths at Tera-Z are projected as 0.45%, 4.5%, 18%, and 0.95%, respectively. Their dependence on various detector performances is also discussed. In addition, B 0 → $π^0π^0$ and its two isospin-related modes are paid special attention due to their roles in the determination of the CKM angle α (Φ 2 ). The anticipated precisions of their branching-ratio and CP-asymmetry measurements at Tera-Z are evaluated. We show that the measurement of the time-integrated B 0 → $π^0π^0$ CP asymmetry at Tera-Z is complementary to B-factory ones. The precision on α combining Z- and B-factory results reaches 0.4°, lower than the systematic uncertainties attached to isospin breaking.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Lithium and boron isotopic compositions of olivine in chondrules from carbonaceous and ordinary chondrite meteorites: Implications for the origin of solar 11 B/ 10 B ratio

We report the origin of solar 11 B/ 10 B ratio ~4 remains an open question. It has been thought that a significant portion of boron in the Solar System was derived from continuous spallation nucleosynthesis during interactions between Galactic Cosmic Rays and C—N—O nuclei in the interstellar medium. However, because GCR-produced boron is characterized by 11 B/ 10 B ~2.5, an endmember with 11 B/ 10 B > 4 is required to account for the solar 11 B/ 10 B ratio. Two leading hypotheses for the sources of 11 B-rich components include low energy spallation in the Sun’s parental molecular cloud and the neutrino process during the supernova explosions. In this study, lithium and boron elemental and isotopic compositions of seven porphyritic olivine chondrules and one isolated olivine crystal from four meteorites (Allende, Yamato 81020, Asuka 12236, and QUE 97008) were determined in-situ to help constrain which of the two nucleosynthetic mechanisms has most likely supplied the forming Solar System with extra 11 B. Apparent isotopic variations in Li/Si, B/Si, δ 7 Li and δ 11 B were found in chondrule olivine crystals, but only three chondrules exhibit statistically resolved δ 11 B heterogeneities. Using these three chondrules as a basis for discussion, we evaluated the processes that could potentially cause elemental and isotopic variations of Li and B. We argue that the data can be best understood in the context of condensation of lithium-boron-rich material onto chondrule precursors in (an) initially heterogeneous gaseous reservoir(s), which could be realized if the Solar System derived 11 B-rich components from a supernova or supernovae.

58 GEOSCIENCES↗
DOE OSTI2024

Observation of the Ξ b − → ψ ( 2 S ) Ξ − decay and studies of the Ξ b ( 5945 ) 0 baryon in proton-proton collisions at s = 13 TeV

The first observation of the decay Ξ b − → ψ ( 2 S ) Ξ − and measurement of the branching ratio of Ξ b − → ψ ( 2 S ) Ξ − to Ξ b − → J / ψ Ξ − are presented. The J / ψ and ψ ( 2 S ) mesons are reconstructed using their dimuon decay modes. The results are based on proton-proton colliding beam data from the LHC collected by the CMS experiment at s = 13 TeV in 2016–2018, corresponding to an integrated luminosity of 140 fb − 1 . The branching fraction ratio is measured to be B ( Ξ b − → ψ ( 2 S ) Ξ − ) / B ( Ξ b − → J / ψ Ξ − ) = 0.8 4 − 0.19 + 0.21 ( stat ) ± 0.10 ( syst ) ± 0.02 ( B ) , where the last uncertainty comes from the uncertainties in the branching fractions of the charmonium states. New measurements of the Ξ b ( 5945 ) 0 baryon mass and natural width are also presented, using the Ξ b − π + final state, where the Ξ b − baryon is reconstructed through the decays J / ψ Ξ − , ψ ( 2 S ) Ξ − , J / ψ Λ K − , and J / ψ Σ 0 K − . Finally, the fraction of Ξ b − baryons produced from Ξ b ( 5945 ) 0 decays is determined. © 2024 CERN, for the CMS Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Observation of B$^0$$\to$$\psi$(2S)K$^0_\mathrm{S}\pi^+\pi^-$ and B$^0_\mathrm{S}$$\to$$\psi$(2S)K$^0_\mathrm{S}$ decays

Using a data sample of $\sqrt{s} =$ 13 TeV proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of 103 fb$^{-1}$, the B$^0$$\to$$\psi$(2S)K$^0_\mathrm{S}$ and B$^0_\mathrm{S}$$\to$$\psi$(2S)K$^0_\mathrm{S}\pi^+\pi^-$ decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to $\mathcal{B}$(B$^0_\mathrm{S}$$\to$$\psi$(2S)K$^0_\mathrm{S}$) / $\mathcal{B}$(B$^0$$\to$$\psi$(2S)K$^0_\mathrm{S}$) = (3.33 $\pm$ 0.69 (stat) $\pm$ 0.11 (syst) $\pm$ 0.34 ($f_\mathrm{s} / f_\mathrm{d}$)) $\times$ 10$^{-2}$ and $\mathcal{B}$(B$^0$$\to$$\psi$(2S)K$^0_\mathrm{S}\pi^+\pi^-$) / $\mathcal{B}$(B$^0$$\to$$\psi$(2S)K$^0_\mathrm{S}$) = 0.480 $\pm$ 0.013 (stat) $\pm$ 0.032 (syst), where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of B$^0_\mathrm{s}$ and B$^0$ mesons, $f_\mathrm{s} / f_\mathrm{d}$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗