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Boschetti, A. (ORCID:0000000160303087)

Publications and source records attributed to Boschetti, A. (ORCID:0000000160303087).

28 records Β· Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Measurement of the time-integrated 𝐢⁒𝑃 asymmetry in 𝐷 0 β†’ πœ‹ 0 β’πœ‹ 0 decays at Belle II

We measure the time-integrated 𝐢⁒𝑃 asymmetry, 𝐴 𝐢⁒𝑃 , in 𝐷 0 β†’ πœ‹ 0 β’πœ‹ 0 decays reconstructed in 𝑒 + ⁒𝑒 βˆ’ β†’ $𝑐⁒\bar{𝑐}$ events collected by Belle II during 2019–2022. The data corresponds to an integrated luminosity of 428 fb βˆ’1 . The 𝐷 0 decays are required to originate from the flavor-conserving 𝐷 *+ β†’ 𝐷 0 β’πœ‹ + decay to determine the charm flavor at production time. Control samples of 𝐷 0 β†’ 𝐾 βˆ’ β’πœ‹ + decays, with or without an associated pion from a 𝐷 *+ decay, are used to correct for detection asymmetries. The result, 𝐴 𝐢⁒𝑃 ⁑(𝐷 0 β†’ πœ‹ 0 β’πœ‹ 0 ) = (0.30 Β± 0.72 Β± 0.20)%, where the first uncertainty is statistical and the second systematic, is consistent with 𝐢⁒𝑃 symmetry.

CP violation↗
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 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 OSTI2025

Observation of time-dependent C P violation and measurement of the branching fraction of B 0 β†’ J / ψ Ο€ 0 decays

We present a measurement of the branching fraction and time-dependent charge-parity ( C P ) decay-rate asymmetries in B 0 β†’ J / ψ Ο€ 0 decays. The data sample was collected with the Belle II detector at the SuperKEKB asymmetric e + e βˆ’ collider in 2019–2022 and contains ( 387 Β± 6 ) Γ— 10 6 B B Β― meson pairs from Ο’ ( 4 S ) decays. We reconstruct 392 Β± 24 signal decays and fit the C P parameters from the distribution of the proper-decay-time difference of the two B mesons. We measure the branching fraction to be ( B 0 β†’ J / ψ Ο€ 0 ) = ( 2.00 Β± 0.12 Β± 0.09 ) Γ— 10 βˆ’ 5 and the direct and mixing-induced C P asymmetries to be C C P = 0.13 Β± 0.12 Β± 0.03 and S C P = βˆ’ 0.88 Β± 0.17 Β± 0.03 , respectively, where the first uncertainties are statistical and the second are systematic. We observe mixing-induced C P violation with a significance of 5.0 standard deviations for the first time in this mode. 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 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

Measurement of the branching fraction of the decay B βˆ’ β†’ D 0 ρ ( 770 ) βˆ’ at Belle II

We measure the branching fraction of the decay B βˆ’ β†’ D 0 ρ ( 770 ) βˆ’ using data collected with the Belle II detector. The data contain 387 million B B Β― pairs produced in e + e βˆ’ collisions at the Ο’ ( 4 S ) resonance. We reconstruct 8360 Β± 180 decays from an analysis of the distributions of the B βˆ’ energy and the ρ ( 770 ) βˆ’ helicity angle. We determine the branching fraction to be ( 0.939 Β± 0.021 ( stat ) Β± 0.050 ( syst ) ) % , in agreement with previous results. Our measurement improves the relative precision of the world average by more than a factor of two. Published by the American Physical Society 2024

Astronomy & Astrophysics↗