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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 163 records · Page 9
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DOE OSTI2022

Measurements of jet observables sensitive to $\textit{b}$-quark fragmentation in $t\bar{t}$ events at the LHC with the ATLAS detector

Several observables sensitive to the fragmentation of $\textit{b}$ quarks into $\textit{b}$ hadrons are measured using 36 fb -1 of $\sqrt{s}$ = 13 TeV proton-proton collision data collected with the ATLAS detector at the LHC. Jets containing b hadrons are obtained from a sample of dileptonic $t\bar{t}$ events, and the associated set of charged-particle tracks is separated into those from the primary $\textit{pp}$ interaction vertex and those from the displaced b-decay secondary vertex. This division is used to construct observables that characterize the longitudinal and transverse momentum distributions of the $\textit{b}$ hadron within the jet. The measurements have been corrected for detector effects and provide a test of heavy-quark-fragmentation modeling at the LHC in a system where the top-quark decay products are color connected to the proton beam remnants. The unfolded distributions are compared with the predictions of several modern Monte Carlo parton-shower generators and generator tunes, and a wide range of agreement with the data is observed, with $\textit{p}$ values varying from 5 × 10 -4 to 0.98. These measurements complement similar measurements from $e^+e^-$ collider experiments in which the $\textit{b}$ quarks originate from a color singlet $Z/γ^{\ast}$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurements of the branching fractions B ( B ¯ 0 → D * + π - ) and B ( B ¯ 0 → D * + K - ) and tests of QCD factorization

Using (771.6 ± 10.6) × 10 6 $B\overline{B}$ meson pairs recorded by the Belle experiment at the KEKB e + e - collider, we report the branching fractions $\mathscr{B}$($\overline{B}$ 0 → D* + π - ) = (2.62 ± 0.02 ± 0.09 X 10 -3 and $\mathscr{B}$($\overline{B}$ 0 → D* + K - ) = (2.22 ± 0.06 ± 0.08) × 10 -4 ; the quoted uncertainties are statistical and systematic, respectively. A measurement of the ratio of these branching fractions is also presented, R K/π = $\mathscr{B}$($\overline{B}$ → D* + K - )/ $\mathscr{B}$($\overline{B}$ → D* + π - ) = (8.41 ± 0.24 ± 0.13) × 10 -2 , where systematic uncertainties due to the D* + meson reconstruction cancel out. Furthermore, we report a new QCD factorization test based on the measured ratios for $\overline{B}$ → D* + h - and $\overline{B}$ → D* + ℓ - $v$ decays at squared momentum transfer values equivalent to the mass of the h = π or K hadron. The parameters |a 1 (h)| are measured to be |a 1 (π)| = 0.884 ± 0.004 ± 0.003 ± 0.016 and |a 1 (K)| = 0.913 ± 0.019 ± 0.008 ± 0.013, where the last uncertainties account for all external inputs. These values are approximately 15% lower than those expected from theoretical predictions. Subsequently, flavor SU(3) symmetry is tested by measuring the ratios for pions and kaons, |a 1 (K)| 2 /|a 1 (π) 2 | = 1.066 ± 0.042 ± 0.018 ± 0.023, as well as for different particle species. The ratio is consistent with unity and therefore no evidence for SU(3) symmetry breaking effects is found at the 5% precision level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Determination of the titanium spectral function from ($e,e'p$) data

The E12-14-012 experiment, performed in Jefferson Lab Hall A, has measured the (e, e'p) cross section in parallel kinematics using a natural titanium target. In this paper, we report the analysis of the dataset obtained in different kinematics for our solid natural titanium target. Data were obtained in a range of missing momentum and missing energy between 15 ≲ p m ≲ 250 MeV / c and 12 ≲ E m ≲ 80 MeV, respectively, and using an electron beam energy of 2.2 GeV. We measured the reduced cross section with ~7% accuracy as a function of both missing momentum and missing energy. Furthermore, our Monte Carlo simulation, including both a model spectral function and the effects of final-state interactions, satisfactorily reproduces the data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the branching fractions for Cabibbo-suppressed decays D + → K + K - π + π 0 and D ( s ) + → K + π - π + π 0 at Belle

We present measurements of the branching fractions for the singly Cabibbo-suppressed decays and , and the doubly Cabibbo-suppressed decay , based on of data recorded by the Belle experiment at the KEKB e + ⁢e - collider. We measure these modes relative to the Cabibbo-favored modes D + → K - ⁢π + ⁢π + ⁢π 0 and D$^{+}_{s}$ → K + ⁢K -⁢ π + ⁢π 0 . Our results for the ratios of branching fractions are $\mathscr{B}$⁡(D + →K + ⁢K -⁢ π + ⁢π 0 )/$\mathscr{B}$⁡(D + → K - ⁢π + ⁢π + ⁢π 0 ) =(11.32±0.13±0.26)%, $\mathscr{B}$⁡(D + →K + π - ⁢π + ⁢π 0 )/$\mathscr{B}$(D + →K -⁢ π + ⁢π + ⁢π 0 ) =(1.68±0.11±0.03)%, and $\mathscr{B}$⁡(D$^{+}_{s}$ → K + ⁢π - π + ⁢π 0 )/$\mathscr{B}$⁡(D$^{+}_{s}$ → K + ⁢K - π + π 0 ) =(17.13±0.62±0.51)%, where the uncertainties are statistical and systematic, respectively. The second value corresponds to (5.83 ±0.42) ×tan 4 ⁡θ C , where θ C is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for $\mathscr{B}$⁡(D + → K - ⁢π + ⁢π + ⁢π 0 ) and $\mathscr{B}$⁡(D$^{+}_{s}$ → K + ⁢K - π + π 0 ) yields $\mathscr{B}$( + →K + ⁢K -⁢ π + ⁢π 0 ) = (7.08±0.08±0.16±0.20)×10 -3 , $\mathscr{B}$⁡(D + → K +⁢ π - π + ⁢π 0 ) =(1.05±0.07±0.02±0.03)×10 -3 , and $\mathscr{B}$⁡(D$^{+}_{s}$ → K + ⁢π - π + ⁢π 0 ) =(9.44±0.34±0.28±0.32)×10 -3 , where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the branching fraction and search for CP violation in D 0 → K $^{0}_{S}$ K $^{0}_{S}$ ⁢π + ⁢π - decays at Belle

We measure the branching fraction for the Cabibbo-suppressed decay D 0 → K $^{0}_{S}$ K $^{0}_{S}$ ⁢π + ⁢π - and search for CP violation via a measurement of the CP asymmetry A CP as well as the T-odd triple-product asymmetry a$^{T}_{CP}$. We use 922 fb -1 of data recorded by the Belle experiment, which ran at the KEKB asymmetric-energy e + ⁢e - collider. The branching fraction is measured relative to the Cabibbo-favored normalization channel D 0 → K $^{0}_{S}$ ⁢π + ⁢π - ; the result is $\mathscr{B}$⁡( D 0 → K $^{0}_{S}$ K $^{0}_{S}$ ⁢π + ⁢π - )=[4.79±0.08⁢(stat)±0.10⁢(syst)±0.31⁢(norm)]×10 -4 , where the first uncertainty is statistical, the second is systematic, and the third is from uncertainty in the normalization channel. We also measure A CP =[-2.51±1.44⁢(stat)$^{+0.11}_{-0.10}$⁢(syst)]%, and a$^{T}_{CP}$=[-1.95±1.42⁢(stat)$^{+0.14}_{-0.12}⁢$(syst)]%. These results show no evidence of CP violation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Novel method for the identification of the production flavor of neutral charmed mesons

We propose a new algorithm for the identification of the production flavor of neutral D mesons in the Belle II experiment. The algorithm exploits the correlation between the flavor of a reconstructed neutral D meson (signal D meson) and the electric charges of particles reconstructed in the rest of the e + e – →$c\bar{c}$ event. These include those originating from the decay of the other charm hadron produced in the event, as well as those possibly produced in association with the signal D meson. We develop the algorithm using simulation and calibrate it in data using decay modes that identify the flavor of the decaying neutral D meson. We use a data sample of e + e – collisions, corresponding to 362 fb –1 of integrated luminosity, collected by Belle II at center-of-mass energies near the Υ(4S) mass. The effective tagging efficiency in data is (47.91±0.07 (stat) ±0.51 (syst)) %, independent of the neutral-D-meson decay mode. This charm flavor tagger will approximately double the effective sample size of many CP-violation and charm-mixing measurements that so far have exclusively relied on neutral D mesons originating from D* ± decays. While developed for Belle II, the basic principles underlying the charm flavor tagger can be used in other experiments, including those at hadron colliders.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the $Ω_c^0$ lifetime at Belle II

We report on a measurement of the $Ω_c^0$ lifetime using $Ω_c^0$ → Ω-π + decays reconstructed in c data collected by the Belle II experiment and corresponding to 207 fb -1 of integrated e + e - → c luminosity. The result, τ ($Ω_c^0$) = 243 ± 48 (stat) ± 11 (syst) fs, agrees with recent measurements indicating that the $Ω_c^0$ is not the shortest-lived weakly decaying charmed baryon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the B 0 lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019–2021 Belle II data

We measure the B0 lifetime and flavor-oscillation frequency using B 0 → D(*) – π + decays collected by the Belle II experiment in asymmetric-energy e + ⁢e – collisions produced by the SuperKEKB collider operating at the Υ⁡(4⁢S) resonance. We fit the decay-time distribution of signal decays, where the initial flavor is determined by identifying the flavor of the other B meson in the event. The results, based on 33000 signal decays reconstructed in a data sample corresponding to 190 fb –1 , are τ B 0 = (1.499 ± 0.013 ± 0.008) ps, Δ⁢m d = (0.516 ± 0.008 ± 0.005) ps –1 , where the first uncertainties are statistical and the second are systematic. These results are consistent with the world-average values.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Measurement of the τ -lepton mass with the Belle II experiment

We present a measurement of the τ-lepton mass using a sample of about 175 million $e^+$$e^-$ → ${{\tau}}^+{{\tau}}^-$ events collected with the Belle II detector at the SuperKEKB $e^+$$e^-$ collider at a center-of-mass energy of 10.579GeV. This sample corresponds to an integrated luminosity of $190$ $\mathrm{fb}$$^{-1}$. We use the kinematic edge of the ${{\tau}}$ pseudomass distribution in the decay ${{\tau}}^-$ → $π^-π^+π^-ν_τ$ and measure the ${{\tau}}$ mass to be $1777.09±0.08±0.11$ $\mathrm{MeV}$ $/{c^2}$, where the first uncertainty is statistical and the second systematic. This result is the most precise to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for a dark leptophilic scalar produced in association with τ + τ − pair in e + e − annihilation at center-of-mass energies near 10.58 GeV

A dark leptophilic scalar ( ϕ L ) is a hypothetical particle that couples only to leptons rather than quarks. We report on a search for ϕ L in the e + e − → τ + τ − ϕ L , ϕ L → ℓ + ℓ − ( ℓ = e , μ ) process using 626 fb − 1 of data collected by the Belle experiment near the ϒ ( 4 S ) resonance. We validate the backgrounds with multiple control regions in data, using a novel multiclass multivariate event classifier. In absence of a signal, we quote upper limits at the 90% confidence level on the coupling between ϕ L and leptons. Our bounds, obtained in a blinded approach, are 19% more constraining than the previous limits, averaged over the mass range 0.04 ≤ m ϕ L ≤ 6.5 GeV . We exclude the parameter space below 4 GeV favored by measurement of the anomalous magnetic moment of the muon. Published by the American Physical Society 2024

Biswas, D. (ORCID:0000000275433471)↗
DOE OSTI2024

Search for the decay B s 0 → J / ψ π 0 at Belle experiment

We have analyzed 121.4 fb − 1 of data collected at the ϒ ( 5 S ) resonance by the Belle experiment using the KEKB asymmetric-energy e + e − collider to search for the decay B s 0 → J / ψ π 0 . We observe no signal and report an upper limit on the branching fraction B ( B s 0 → J / ψ π 0 ) of 1.21 × 10 − 5 at 90% confidence level. This result is the most stringent, improving the previous bound by 2 orders of magnitude. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Search for the e + e − → η b ( 1 S ) ω and e + e − → χ b 0 ( 1 P ) ω processes at s = 10.745 GeV

We search for the e + e − → η b ( 1 S ) ω and e + e − → χ b 0 ( 1 P ) ω processes at a center-of-mass energy of 10.745 GeV, which is close to the peak of the ϒ ( 10753 ) state. We use data collected by the Belle II experiment during a special run, corresponding to an integrated luminosity of 9.8 fb − 1 . We reconstruct ω → π + π − π 0 decays and use the ω meson’s recoil mass to search for the signals. We do not find evidence for either process, and set upper limits on the corresponding Born-level cross sections of 2.5 pb and 7.8 pb, respectively, at the 90% confidence level. The χ b 0 ( 1 P ) ω limit is the result of a combination of this analysis and a previous search using full reconstruction. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

New constraints on ultraheavy dark matter from the LZ experiment

Searches for dark matter with liquid xenon time projection chamber experiments have traditionally focused on the region of the parameter space that is characteristic of weakly interacting massive particles, ranging from a few GeV / c 2 to a few TeV / c 2 . Models of dark matter with a mass much heavier than this are well motivated by early production mechanisms different from the standard thermal freeze-out, but they have generally been less explored experimentally. In this work, we present a reanalysis of the first science run of the LZ experiment, with an exposure of 0.9 tonne × yr , to search for ultraheavy particle dark matter. The signal topology consists of multiple energy deposits in the active region of the detector forming a straight line, from which the velocity of the incoming particle can be reconstructed on an event-by-event basis. Zero events with this topology were observed after applying the data selection calibrated on a simulated sample of signal-like events. New experimental constraints are derived, which rule out previously unexplored regions of the dark matter parameter space of spin-independent interactions beyond a mass of 10 17 GeV / c 2 . Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for a μ + μ − resonance in four-muon final states at Belle II

We report on a search for a resonance X decaying to a pair of muons in e + e − → μ + μ − X events in the 0.212 – 9.000 GeV / c 2 mass range, using 178 fb − 1 of data collected by the Belle II experiment at the SuperKEKB collider at a center of mass energy of 10.58 GeV. The analysis probes two different models of X beyond the standard model: a Z ′ vector boson in the L μ − L τ model and a muonphilic scalar. We observe no evidence for a signal and set exclusion limits at the 90% confidence level on the products of cross section and branching fraction for these processes, ranging from 0.046 fb to 0.97 fb for the L μ − L τ model and from 0.055 fb to 1.3 fb for the muonphilic scalar model. For masses below 6 GeV / c 2 , the corresponding constraints on the couplings of these processes to the standard model range from 0.0008 to 0.039 for the L μ − L τ model and from 0.0018 to 0.040 for the muonphilic scalar model. These are the first constraints on the muonphilic scalar from a dedicated search. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Test of lepton flavor universality with a measurement of R ( D * ) using hadronic B tagging at the Belle II experiment

The ratio of branching fractions R ( D * ) = B ( B ¯ → D * τ − ν ¯ τ ) / B ( B ¯ → D * ℓ − ν ¯ ℓ ) , where ℓ is an electron or muon, is measured using a Belle II data sample with an integrated luminosity of 189 fb − 1 at the SuperKEKB asymmetric-energy e + e − collider. Data is collected at the ϒ ( 4 S ) resonance, and one B meson in the ϒ ( 4 S ) → B B ¯ decay is fully reconstructed in hadronic decay modes. The accompanying signal B meson is reconstructed as B ¯ → D * τ − ν ¯ τ using leptonic τ decays. The normalization decay, B ¯ → D * ℓ − ν ¯ ℓ , produces the same observable final-state particles. The ratio of branching fractions is extracted in a simultaneous fit to two signal-discriminating variables in both channels and yields R ( D * ) = 0.262 − 0.039 + 0.041 ( stat ) − 0.032 + 0.035 ( syst ) . This result is consistent with the current world average and with Standard Model predictions. Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)↗
DOE OSTI2024

Search for the baryon number and lepton number violating decays τ − → Λ π − and τ − → Λ ¯ π − at Belle II

We present a search for the baryon number B and lepton number L violating decays τ − → Λ π − and τ − → Λ ¯ π − produced from the e + e − → τ + τ − process, using a 364 fb − 1 data sample collected by the Belle II experiment at the SuperKEKB collider. No evidence of signal is found in either decay mode, which have | Δ ( B − L ) | equal to 2 and 0, respectively. Upper limits at 90% credibility level on the branching fractions of τ − → Λ π − and τ − → Λ ¯ π − are determined to be 4.7 × 10 − 8 and 4.3 × 10 − 8 , respectively. Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)↗
DOE OSTI2024

Model-independent determination of the strong-phase difference between D 0 and D ¯ 0 → π + π − π + π − decays

Measurements of the strong-phase difference between D 0 and D ¯ 0 → π + π − π + π − are performed in bins of phase space. The study exploits a sample of quantum-correlated D D ¯ mesons collected by the BESIII experiment in e + e − collisions at a center-of-mass energy of 3.773 GeV, corresponding to an integrated luminosity of 2.93 fb − 1 . Here, D denotes a neutral charm meson in a superposition of flavor eigenstates. The reported results are valuable for measurements of the C P -violating phase γ (also denoted ϕ 3 ) in B ± → D K ± , D → π + π − π + π − decays, and the binning schemes are designed to provide good statistical sensitivity to this parameter. The expected uncertainty on γ arising from the precision of the strong-phase measurements, when applied to very large samples of B -meson decays, is around 1.5° or 2°, depending on the binning scheme. The binned strong-phase parameters are combined to give a value of F + 4 π = 0.746 ± 0.010 ± 0.004 for the C P -even fraction of D 0 → π + π − π + π − decays, which is around 30% more precise than the previous best measurement of this quantity. Published by the American Physical Society 2024

Ablikim, M.↗