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Dossett, D. (ORCID:0000000256705582)

Publications and source records attributed to Dossett, D. (ORCID:0000000256705582).

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Search for B 0 β†’ K *0 𝜏 + ⁒𝜏 βˆ’ Decays at the Belle II Experiment

We present a search for the rare flavor-changing neutral-current decay 𝐡 0 →𝐾 *0 ⁒𝜏 + ⁒𝜏 βˆ’ with data collected by the Belle II experiment at the SuperKEKB electron-positron collider. The analysis uses a 365 fb βˆ’1 data sample recorded at the center-of-mass energy of the ϒ⁑(4⁒𝑆) resonance. One of the 𝐡 mesons produced in the ϒ⁑(4⁒𝑆)→𝐡 0 $⁒\overline{𝐡}$ 0 process is fully reconstructed in a hadronic decay mode, while its companion 𝐡 meson is required to decay into a 𝐾 *0 and two 𝜏 leptons of opposite charge. The 𝜏 leptons are reconstructed in final states with a single electron, muon, charged pion or charged 𝜌 meson, and additional neutrinos. We set an upper limit on the branching fraction of ℬ⁑(𝐡 0 →𝐾 *0 ⁒𝜏 + ⁒𝜏 βˆ’ )<1.8Γ—10 βˆ’3 at the 90% confidence level, which is the most stringent constraint reported to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for a Dark Higgs Boson Produced in Association with Inelastic Dark Matter at the Belle II Experiment

Inelastic dark matter models that have two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limits. The mass splitting between the two dark matter particles πœ’ 1 and πœ’ 2 , with π‘šβ‘(πœ’ 2 ) >π‘šβ‘(πœ’ 1 ), is induced by a dark Higgs field and a corresponding dark Higgs boson β„Žβ€². We present a search for dark matter in events with two vertices, at least one of which must be displaced from the interaction region, and missing energy. Using a 365 fb βˆ’1 data sample collected at Belle II, which operates at the SuperKEKB 𝑒 + ⁒𝑒 βˆ’ collider, we observe no evidence for a signal. We set upper limits on the product of the production cross section 𝜎⁑(𝑒 + ⁒𝑒 βˆ’ β†’ β„Žβ€²β‘πœ’ 1 β’πœ’ 2 ), and the product of branching fractions ℬ⁑(πœ’ 2 β†’ πœ’ 1⁒ 𝑒 + ⁒𝑒 βˆ’ ) ×ℬ⁑(β„Žβ€² β†’ π‘₯ + ⁒π‘₯ βˆ’ ), where π‘₯ + ⁒π‘₯ βˆ’ indicates πœ‡ + β’πœ‡ βˆ’ , πœ‹ + β’πœ‹ βˆ’ , or 𝐾 + ⁒𝐾 βˆ’ , as functions of β„Žβ€² mass and lifetime at the level of 10 βˆ’1 fb. We set model-dependent upper limits on the dark Higgs mixing angle at the level of 10 βˆ’5 and on the dark photon kinetic mixing parameter at the level of 10 βˆ’3 . This is the first search for dark Higgs bosons in association with inelastic dark matter.

dark matter↗
DOE OSTI2025

Test of lepton flavor universality with measurements of 𝑅⁑(𝐷 + ) and 𝑅⁑(𝐷* + ) using semileptonic 𝐡 tagging at the Belle II experiment

We report measurements of the ratios of branching fractions ℛ⁑(𝐷 (*)+ ) = ℬ⁑($\bar{𝐡}$ 0 β†’ 𝐷 (*)+ ⁒𝜏 βˆ’β’ $\bar{𝜈}$ 𝜏 )/ℬ⁑($\bar{𝐡}$ 0 β†’ 𝐷 (*)+ ⁒ℓ βˆ’ $\bar{𝜈}$ β„“ ), where β„“ denotes either an electron or a muon. These ratios test the universality of the charged-current weak interaction. The results are based on a 365 fb βˆ’1 data sample collected with the Belle II detector at the SuperKEKB 𝑒 + ⁒𝑒 βˆ’ collider, which operates at a center-of-mass energy corresponding to the ϒ⁑(4⁒𝑆) resonance, just above the threshold for $𝐡\bar{𝐡}$ production. Signal candidates are reconstructed by selecting events in which the companion 𝐡 meson from the ϒ⁑(4⁒𝑆) β†’ $𝐡\bar{𝐡}$ decay is identified in semileptonic modes. The 𝜏 lepton is reconstructed via its leptonic decays. We obtain ℛ⁑(𝐷 + ) = 0.418$^{+0.075}_{βˆ’0.073}$⁒(stat)$^{+0.049}_{βˆ’0.056}$⁒(syst) and ℛ⁑(𝐷 *+ ) = 0.306$^{+0.035}_{βˆ’0.033}$⁒(stat)$^{+0.016}_{βˆ’0.018⁒}$(syst), which are consistent with world average values. Accounting for the correlation between them, these values differ from the Standard Model expectation by a collective significance of 1.7 standard deviations.

bottom quark↗
DOE OSTI2025

Search for Lepton-Flavor-Violating Decay Modes 𝐡 0 →𝐾$^0_𝑆$⁒𝜏 Β± ⁒ℓ βˆ“ with Hadronic 𝐡 Tagging at Belle and Belle II

We present the first search for the lepton-flavor-violating decay modes 𝐡 0 →𝐾$^0_𝑆$⁒𝜏 Β± ⁒ℓ βˆ“ (β„“=πœ‡,𝑒) using the 711 and 365 fb βˆ’1 data samples recorded by the Belle and Belle II detectors, respectively. We use a hadronic 𝐡-tagging technique to fully reconstruct a 𝐡 meson and search for signal decays in the system recoiling against the tagged meson, considering 𝜏 decays to either light leptons, one charged hadron, or one charged hadron and a neutral pion. We find no evidence for 𝐡 0 →𝐾$^0_𝑆$⁒𝜏 Β± ⁒ℓ βˆ“ decays and set 90% confidence level upper limits on the branching fractions in the range of [0.8,3.6] Γ—10 βˆ’5 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for 𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 and 𝑃 𝑐$\overline{𝑐}$𝑠 (4338) 0 in Ο’(1𝑆,2𝑆) Inclusive Decays at Belle

Using data samples of 102 million ϒ⁑(1⁒𝑆) events and 158 million ϒ⁑(2⁒𝑆) events collected by the Belle detector at the KEKB asymmetric-energy 𝑒+β’π‘’βˆ’ collider, we search for [𝑒⁒𝑑⁒𝑠⁒𝑐$\overline{𝑐}$ ] pentaquark states decaying to 𝐽/πœ“β’Ξ›. Using the first observations of ϒ⁑(1⁒𝑆,2⁒𝑆) inclusive decays to 𝐽/πœ“β’Ξ›, we find evidence of the 𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 state with a local significance of 3.3 standard deviations, including statistical and systematic uncertainties. We measure the mass and width of the 𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 to be (4471.7Β±4.8Β±0.6) MeV/𝑐 2 and (22 Β±13 Β±3) MeV, respectively. The branching fractions for 𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 production are measured to be ℬ⁑[ϒ⁑(1⁒𝑆)→𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459)0/ $\overline{𝑃}$ 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 +anything]=(3.5Β±2.0Β±0.2)Γ—10 βˆ’6 and ℬ⁑[ϒ⁑(2⁒𝑆)→𝑃 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 /$\overline{𝑃}$ 𝑐$\overline{𝑐}$𝑠 ⁒(4459) 0 +anything]=(2.9Β±1.7Β±0.4)Γ—10 βˆ’6 . The inclusive branching fractions of ϒ⁑(1⁒𝑆,2⁒𝑆) →𝐽/πœ“β’Ξ›/$\overline{Ξ›}$ are measured to be ℬ⁑[ϒ⁑(1⁒𝑆) →𝐽/πœ“β’Ξ›/$\overline{Ξ›}$ +anything] =(36.9 Β±5.3 Β±2.4) Γ—10 βˆ’6 and ℬ⁑[ϒ⁑(2⁒𝑆) →𝐽/πœ“β’Ξ›/$\overline{Ξ›}$ +anything] =(22.3 Β±5.7 Β±3.1) Γ—10 βˆ’6 . We measure the visible cross section 𝜎⁑(𝑒+β’π‘’βˆ’β†’π½/πœ“β’Ξ›/ $\overline{Ξ›}$ +anything)=(90Β±14Β±6) fb for the continuum production at βˆšπ‘  =10.52 GeV. In all cases, the first uncertainties are statistical and the second are systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of the branching fraction of Ξ› + 𝑐 →𝑝⁒𝐾 0 𝑆⁒ πœ‹ 0 at Belle

We report a precise measurement of the ratio of branching fractions ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾$^0_𝑆$β’πœ‹ 0 )/ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾 βˆ’ β’πœ‹ + ) using 980 fb βˆ’1 of 𝑒 + ⁒𝑒 βˆ’ data from the Belle experiment. We obtain a value of ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾$^0_𝑆$β’πœ‹ 0 )/ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾 βˆ’ β’πœ‹ + ) =0.339 Β±0.002 Β±0.009, where the first and second uncertainties are statistical and systematic, respectively. This Belle result is consistent with the previous measurement from the CLEO experiment but has a fivefold improvement in precision. By combining our result with the world average ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾 βˆ’ β’πœ‹ + ), we obtain the absolute branching fraction ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾$^0_𝑆$β’πœ‹ 0 ) =(2.12 Β± 0.01 Β±0.05 Β±0.10)%, where the uncertainties are statistical, systematic, and the uncertainty in the absolute branching fraction scale ℬ⁑(Ξ›$^+_𝑐$ β†’ 𝑝⁒𝐾 βˆ’ β’πœ‹ + ), respectively. This measurement can shed light on hadronic decay mechanisms in charmed baryon decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Model-independent measurement of 𝐷 0 βˆ’$\overline{D}$ 0 mixing parameters in 𝐷 0 β†’ 𝐾$^{0}_{𝑆}$β’πœ‹ + β’πœ‹ βˆ’ decays at Belle and Belle II

We perform a model-independent measurement of the 𝐷 0 βˆ’$\overline{D}$ 0 mixing parameters using samples of 𝑒 + ⁒𝑒 βˆ’ -collision data collected by the Belle and Belle II experiments that have integrated luminosities of 951 fb βˆ’1 and 408 fb βˆ’1 , respectively. Approximately 2.05 Γ— 10 6 neutral 𝐷 mesons are reconstructed in the 𝐷 0 β†’ 𝐾$^{0}_{S}$β’πœ‹ + β’πœ‹ βˆ’ channel, with the neutral 𝐷 flavor tagged by the charge of the pion in the 𝐷* + β†’ 𝐷 0⁒ πœ‹ + decay. Assuming charge-parity symmetry, the mixing parameters are measured to be π‘₯ = (4.0 Β±1.7 Β±0.4) Γ— 10 βˆ’3 and 𝑦 = (2.9 Β±1.4 Β±0.3) Γ— 10 βˆ’3 , where the first uncertainties are statistical and the second systematic. The results are consistent with previous determinations.

Charmed mesons↗
DOE OSTI2025

Measurement of the branching fraction, polarization, and time-dependent C P asymmetry in B 0 β†’ ρ + ρ βˆ’ decays and constraint on the CKM angle Ο• 2

We present a measurement of the branching fraction and fraction of longitudinal polarization of B 0 β†’ ρ + ρ βˆ’ decays, which have two Ο€ 0 ’s in the final state. We also measure time-dependent C P violation parameters for decays into longitudinally polarized ρ + ρ βˆ’ pairs. This analysis is based on a data sample containing ( 387 Β± 6 ) Γ— 10 6 Ο’ ( 4 S ) mesons collected with the Belle II detector at the SuperKEKB asymmetric-energy e + e βˆ’ collider in 2019–2022. We obtain B ( B 0 β†’ ρ + ρ βˆ’ ) = ( 2.8 9 βˆ’ 0.22 + 0.23 βˆ’ 0.27 + 0.29 ) Γ— 10 βˆ’ 5 , f L = 0.92 1 βˆ’ 0.025 + 0.024 βˆ’ 0.015 + 0.017 , S = βˆ’ 0.26 Β± 0.19 Β± 0.08 , and C = βˆ’ 0.02 Β± 0.1 2 βˆ’ 0.05 + 0.06 , where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysis to constrain the Cabibbo-Kobayashi-Maskawa angle Ο• 2 and obtain two solutions; the result consistent with other Standard Model constraints is Ο• 2 = ( 92.6 βˆ’ 4.7 + 4.5 ) Β° . Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)β†—
DOE OSTI2025

Measurement of branching fractions, C P asymmetry, and isospin asymmetry for B β†’ ρ Ξ³ decays using Belle and Belle II data

We present measurements of B + β†’ ρ + Ξ³ and B 0 β†’ ρ 0 Ξ³ decays using a combined data sample of 772 Γ— 10 6 B B Β― pairs collected by the Belle experiment and 387 Γ— 10 6 B B Β― pairs collected by the Belle II experiment in e + e βˆ’ collisions at the Ο’ ( 4 S ) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II datasets yields 114 Β± 12 B + β†’ ρ + Ξ³ and 99 Β± 12 B 0 β†’ ρ 0 Ξ³ decays. The measured branching fractions are ( 13.1 βˆ’ 1.9 βˆ’ 1.2 + 2.0 + 1.3 ) Γ— 10 βˆ’ 7 and ( 7.6 Β± 1.3 βˆ’ 0.8 + 1.0 ) Γ— 10 βˆ’ 7 for B + β†’ ρ + Ξ³ and B 0 β†’ ρ 0 Ξ³ decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry A I ( B β†’ ρ Ξ³ ) = ( 10.9 βˆ’ 11.7 βˆ’ 7.3 + 11.2 + 7.8 ) % and the direct C P asymmetry A C P ( B + β†’ ρ + Ξ³ ) = ( βˆ’ 8.2 Β± 15.2 βˆ’ 1.3 + 2.0 ) % . Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)β†—
DOE OSTI2025

Production cross sections of light and charmed mesons in 𝑒 + ⁒𝑒 βˆ’ annihilation near 10.58 GeV

We report measurements of production cross sections for 𝜌 + , 𝜌 0 , πœ”, 𝐾* + , 𝐾* 0 , πœ™, πœ‚, 𝐾$^0_𝑆$, 𝑓 0 ⁑(980), 𝐷 + , 𝐷 0 , 𝐷$^+_𝑠$, 𝐷* + , 𝐷* 0 , and 𝐷*$^+_𝑠$ in 𝑒 + ⁒𝑒 βˆ’ collisions at a center-of-mass energy near 10.58 GeV. The data were recorded by the Belle experiment, consisting of 571 fb βˆ’1 at 10.58 GeV and 74 fb βˆ’1 at 10.52 GeV. Production cross sections are extracted as a function of the fractional hadron momentum π‘₯ 𝑝 . The measurements are compared to pythia Monte Carlo generator predictions with various fragmentation settings, including those that have increased fragmentation into vector mesons over pseudoscalar mesons. The cross sections measured for light hadrons are consistent with no additional increase of vector over pseudoscalar mesons. The charmed-meson cross sections are compared to earlier measurementsβ€”when availableβ€”including older Belle results, which they supersede. They are in agreement before application of an improved initial-state radiation correction procedure that causes slight changes in their π‘₯ 𝑝 shapes.

fragmentation functions↗
DOE OSTI2025

Measurement of the time-integrated C P asymmetry in D 0 β†’ K S 0 K S 0 decays using Belle and Belle II data

We measure the time-integrated C P asymmetry in D 0 β†’ K S 0 K S 0 decays reconstructed in e + e βˆ’ β†’ c c Β― events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and 428 fb βˆ’ 1 , respectively. The D 0 decays are required to originate from the D * + β†’ D 0 Ο€ + decay, which determines the charm flavor at production time. A control sample of D 0 β†’ K + K βˆ’ decays is used to correct for production and detection asymmetries. The result, ( βˆ’ 1.4 Β± 1.3 ( stat ) Β± 0.1 ( syst ) ) % , is consistent with previous determinations and with C P symmetry. Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)β†—
DOE OSTI2024

Search for the baryon number and lepton number violating decays Ο„ βˆ’ β†’ Ξ› Ο€ βˆ’ and Ο„ βˆ’ β†’ Ξ› Β― Ο€ βˆ’ at Belle II

We present a search for the baryon number B and lepton number L violating decays Ο„ βˆ’ β†’ Ξ› Ο€ βˆ’ and Ο„ βˆ’ β†’ Ξ› Β― Ο€ βˆ’ produced from the e + e βˆ’ β†’ Ο„ + Ο„ βˆ’ process, using a 364 fb βˆ’ 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 | Ξ” ( B βˆ’ L ) | equal to 2 and 0, respectively. Upper limits at 90% credibility level on the branching fractions of Ο„ βˆ’ β†’ Ξ› Ο€ βˆ’ and Ο„ βˆ’ β†’ Ξ› Β― Ο€ βˆ’ are determined to be 4.7 Γ— 10 βˆ’ 8 and 4.3 Γ— 10 βˆ’ 8 , respectively. Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)β†—
DOE OSTI2024

Search for lepton-flavor-violating Ο„ – β†’ ΞΌ – ΞΌ + ΞΌ – decays at Belle II

We present the result of a search for the charged-lepton-flavor violating decay Ο„ – β†’ ΞΌ – ΞΌ + ΞΌ – using a 424 fb –1 sample of data recorded by the Belle II experiment at the SuperKEKB e + e – collider. The selection of e + e – β†’ Ο„ + Ο„ – events is based on an inclusive reconstruction of the non-signal tau decay, and on a boosted decision tree to suppress background. We observe one signal candidate, which is compatible with the expectation from background processes. We set a 90% confidence level upper limit of 1.9 Γ— 10 –8 on the branching fraction of the Ο„ – β†’ ΞΌ – ΞΌ + ΞΌ – decay, which is the most stringent bound to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for Rare b β†’ d β„“ + β„“ βˆ’ Transitions at Belle

We present the results of a search for the b β†’ d β„“ + β„“ βˆ’ flavor-changing neutral-current rare decays B + , 0 β†’ ( Ξ· , Ο‰ , Ο€ + , 0 , ρ + , 0 ) e + e βˆ’ and B + , 0 β†’ ( Ξ· , Ο‰ , Ο€ 0 , ρ + ) ΞΌ + ΞΌ βˆ’ using a 711 fb βˆ’ 1 data sample that contains 772 Γ— 10 6 B B Β― events. The data were collected at the Ο’ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e βˆ’ collider. We find no evidence for signal and set upper limits on branching fractions at the 90% confidence level in the range ( 3.8 – 47 ) Γ— 10 βˆ’ 8 depending on the decay channel. The obtained limits are the world’s best results. This is the first search for the channels B + , 0 β†’ ( Ο‰ , ρ + , 0 ) e + e βˆ’ and B + , 0 β†’ ( Ο‰ , ρ + ) ΞΌ + ΞΌ βˆ’ . Published by the American Physical Society 2024

Physics↗
DOE OSTI2024

Search for the decay B 0 β†’ Ξ³ Ξ³ using Belle and Belle II data

We report the result of a search for the rare decay B 0 β†’ Ξ³ Ξ³ using a combined dataset of 753 Γ— 10 6 B B Β― pairs collected by the Belle experiment and 387 Γ— 10 6 B B Β― pairs collected by the Belle II experiment from decays of the Ο’ ( 4 S ) resonance produced in e + e βˆ’ collisions. A simultaneous fit to the Belle and Belle II data sets yields 11.0 βˆ’ 5.5 + 6.5 signal events, corresponding to a 2.5 Οƒ significance. We determine the branching fraction B ( B 0 β†’ Ξ³ Ξ³ ) = ( 3.7 βˆ’ 1.8 + 2.2 ( stat ) Β± 0.5 ( syst ) ) Γ— 10 βˆ’ 8 and set a 90% credibility level upper limit of B ( B 0 β†’ Ξ³ Ξ³ ) < 6.4 Γ— 10 βˆ’ 8 . Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)β†—
DOE OSTI2024

Measurement of the branching fractions of $$ \overline{B} $$ β†’ D(*)Kβˆ’$$ {K}_{(S)}^{\left(\ast \right)0} $$ and $$ \overline{B} $$ β†’ D(*)$$ {D}_s^{-} $$ decays at Belle II

Abstract We present measurements of the branching fractions of eight$$ {\overline{B}}^0 $$ B Β― 0 β†’D (*)+ K βˆ’ $$ {K}_{(S)}^{\left(\ast \right)0} $$ K S βˆ— 0 ,B βˆ’ β†’D (*)0 K βˆ’ $$ {K}_{(S)}^{\left(\ast \right)0} $$ K S βˆ— 0 decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Ξ₯(4S) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362 fb βˆ’1 . The event yields are extracted from fits to the distributions of the difference between expected and observedBmeson energy, and are efficiency-corrected as a function ofm(K βˆ’ $$ {K}_{(S)}^{\left(\ast \right)0} $$ K S βˆ— 0 ) andm(D (*) $$ {K}_{(S)}^{\left(\ast \right)0} $$ K S βˆ— 0 ) in order to avoid dependence on the decay model. These results include the first observation of$$ {\overline{B}}^0 $$ B Β― 0 β†’D + K βˆ’ $$ {K}_S^0 $$ K S 0 ,B βˆ’ β†’D* 0 K βˆ’ $$ {K}_S^0 $$ K S 0 , and$$ {\overline{B}}^0 $$ B Β― 0 β†’D* + K βˆ’ $$ {K}_S^0 $$ K S 0 decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of theK βˆ’ $$ {K}_{(S)}^{\left(\ast \right)0} $$ K S βˆ— 0 systems are compatible with quasi-two-body decays via a resonant transition with spin-parityJ P = 1 βˆ’ for theK βˆ’ $$ {K}_S^0 $$ K S 0 systems andJ P = 1 + for theK βˆ’ K* 0 systems. We also present measurements of the branching fractions of four$$ {\overline{B}}^0 $$ B Β― 0 β†’D (*)+ $$ {D}_s^{-} $$ D s βˆ’ ,B βˆ’ β†’D (*)0 $$ {D}_s^{-} $$ D s βˆ’ decay channels with a precision compatible to the current world averages.

Physics↗
DOE OSTI2024

New graph-neural-network flavor tagger for Belle II and measurement of sin 2β’πœ™ 1 in 𝐡 0 β†’ 𝐽/πœ“β’πΎ$^0_ S$ decays

We present GFlaT, a new algorithm that uses a graph-neural-network to determine the flavor of neutral 𝐡 mesons produced in ϒ⁑(4⁒𝑆) decays. It improves previous algorithms by using the information from all charged final-state particles and the relations between them. We evaluate its performance using 𝐡 decays to flavor-specific hadronic final states reconstructed in a 362 fb βˆ’1 sample of electron-positron collisions collected at the ϒ⁑(4⁒𝑆) resonance with the Belle II detector at the SuperKEKB collider. We achieve an effective tagging efficiency of (37.40 Β± 0.43 Β± 0.36%), where the first uncertainty is statistical and the second systematic, which is 18% better than the previous Belle II algorithm. Demonstrating the algorithm, we use 𝐡 0 →𝐽/πœ“β’πΎ$^0_ S$ decays to measure the mixing-induced and direct 𝐢⁒𝑃 violation parameters, 𝑆 = (0.724 Β± 0.035 Β± 0.009) and 𝐢 = (βˆ’0.035 Β± 0.026 Β± 0.029).

CP violation↗
DOE OSTI2024

Measurement of C P asymmetries in B 0 β†’ K S 0 K S 0 K S 0 decays at Belle II

We report a measurement of decay-time-dependent charge-parity ( C P ) asymmetries in B 0 β†’ K S 0 K S 0 K S 0 decays. We use 387 Γ— 10 6 B B Β― pairs collected at the Ο’ ( 4 S ) resonance with the Belle II detector at the SuperKEKB asymmetric-energy electron-positron collider. We reconstruct 220 signal events and extract the C P -violating parameters S and C from a fit to the distribution of the decay-time difference between the two B mesons. The resulting confidence region is consistent with previous measurements in B 0 β†’ K S 0 K S 0 K S 0 and B 0 β†’ ( c c Β― ) K 0 decays and with predictions based on the standard model. Published by the American Physical Society 2024

Astronomy & Astrophysics↗