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Li Gioi, L. (ORCID:0000000320245649)

Publications and source records attributed to Li Gioi, L. (ORCID:0000000320245649).

At least 19 records
All sourcesNASA NTRSDOE OSTI
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 OSTI2024

Evidence of h b ( 2 P ) β†’ Ο’ ( 1 S ) Ξ· Decay and Search for h b ( 1 P , 2 P ) β†’ Ο’ ( 1 S ) Ο€ 0 with the Belle Detector

We report the first evidence for the h b ( 2 P ) β†’ Ο’ ( 1 S ) Ξ· transition with a significance of 3.5 standard deviations. The decay branching fraction is measured to be B [ h b ( 2 P ) β†’ Ο’ ( 1 S ) Ξ· ] = ( 7.1 βˆ’ 3.2 + 3.7 Β± 0.8 ) Γ— 10 βˆ’ 3 , which is noticeably smaller than expected. We also set upper limits on Ο€ 0 transitions of B [ h b ( 2 P ) β†’ Ο’ ( 1 S ) Ο€ 0 ] < 1.8 Γ— 10 βˆ’ 3 , and B [ h b ( 1 P ) β†’ Ο’ ( 1 S ) Ο€ 0 ] < 1.8 Γ— 10 βˆ’ 3 , at the 90% confidence level. These results are obtained with a 131.4 fb βˆ’ 1 data sample collected near the Ο’ ( 5 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e βˆ’ collider. Published by the American Physical Society 2024

Kovalenko, E. (ORCID:0000000180841931)β†—
DOE OSTI2024

Angular analysis of B β†’ K * e + e βˆ’ in the low- q 2 region with new electron identification at Belle

We perform an angular analysis of the B β†’ K * e + e βˆ’ decay for the dielectron mass squared, q 2 , range of 0.0008 – 1.1200 GeV 2 / c 4 using the full Belle dataset in the K * 0 β†’ K + Ο€ βˆ’ and K * + β†’ K S 0 Ο€ + channels, incorporating new methods of electron identification to improve the statistical power of the dataset. This analysis is sensitive to contributions from right-handed currents from physics beyond the Standard Model by constraining the Wilson coefficients C 7 ( β€² ) . We perform a fit to the B β†’ K * e + e βˆ’ differential decay rate and measure the imaginary component of the transversality amplitude to be A T Im = βˆ’ 1.27 Β± 0.52 Β± 0.12 , and the K * transverse asymmetry to be A T ( 2 ) = 0.52 Β± 0.53 Β± 0.11 , with F L and A T Re fixed to the Standard Model values. The resulting constraints on the value of C 7 β€² are consistent with the Standard Model within a 2 Οƒ confidence interval. Published by the American Physical Society 2024

Ferlewicz, D. (ORCID:0000000243741234)β†—
DOE OSTI2024

Measurement of Angular Coefficients of B Β― β†’ D * β„“ Ξ½ Β― β„“ : Implications for | V c b | and Tests of Lepton Flavor Universality

We measure the complete set of angular coefficients J i for exclusive B Β― β†’ D * β„“ Ξ½ Β― β„“ decays ( β„“ = e , ΞΌ ). Our analysis uses the full 711 fb βˆ’ 1 Belle dataset with hadronic tag-side reconstruction. The results allow us to extract the form factors describing the B Β― β†’ D * transition and the Cabibbo-Kobayashi-Maskawa matrix element | V cb | . Using recent lattice QCD calculations for the hadronic form factors, we find | V cb | = ( 40.7 Β± 0.7 ) Γ— 10 βˆ’ 3 using the Boyd-Grinstein-Lebed parametrization, compatible with determinations from inclusive semileptonic decays. We search for lepton flavor universality violation as a function of the hadronic recoil parameter w and investigate the differences of the electron and muon angular distributions. We find no deviation from standard model expectations. Published by the American Physical Society 2024

Physics↗
DOE OSTI2024

Measurements of the Branching Fraction, Polarization, and C P Asymmetry for the Decay B 0 β†’ Ο‰ Ο‰

We present a comprehensive study of B 0 β†’ Ο‰ Ο‰ decays using 772 Γ— 10 6 B B Β― pairs collected with the Belle detector at the KEKB e + e βˆ’ collider. This process is a suppressed charmless decay into two vector mesons and can exhibit interesting polarization and C P violation. The decay is observed for the first time with a significance of 7.9 standard deviations. We measure a branching fraction B = ( 1.53 Β± 0.29 Β± 0.17 ) Γ— 10 βˆ’ 6 , a fraction of longitudinal polarization f L = 0.87 Β± 0.13 Β± 0.13 , and a time-integrated C P asymmetry A C P = βˆ’ 0.44 Β± 0.43 Β± 0.11 , where the first uncertainties listed are statistical and the second are systematic. This is the first observation of B 0 β†’ Ο‰ Ο‰ and the first measurements of f L and A C P for this decay. Published by the American Physical Society 2024

Physics↗
DOE OSTI2024

Search for Baryon-Number-Violating Processes in B βˆ’ Decays to the Ξ Β― c 0 Ξ› Β― c βˆ’ Final State

We report the results of the first search for B βˆ’ decays to the Ξ Β― c 0 Ξ› Β― c βˆ’ final state using 711 fb βˆ’ 1 of data collected at the Ο’ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e βˆ’ collider. The results are interpreted in terms of both direct baryon-number-violating B βˆ’ decay and Ξ c 0 βˆ’ Ξ Β― c 0 oscillations which follow the standard model decay B βˆ’ β†’ Ξ c 0 Ξ› Β― c βˆ’ . We observe no evidence for baryon number violation and set the 95% confidence-level upper limits on the ratio of baryon-number-violating and standard model branching fractions B ( B βˆ’ β†’ Ξ Β― c 0 Ξ› Β― c βˆ’ ) / B ( B βˆ’ β†’ Ξ c 0 Ξ› Β― c βˆ’ ) to be < 2.7 % and on the effective angular frequency of mixing Ο‰ in Ξ c 0 βˆ’ Ξ Β― c 0 oscillations to be < 0.76 ps βˆ’ 1 (equivalent to Ο„ mix > 1.3 ps ). Published by the American Physical Society 2024

Physics↗
DOE OSTI2024

Search for two-body B meson decays to Ξ› 0 and Ξ© c ( * ) 0

We report the results of the first search for Standard Model and baryon-number-violating two-body decays of the neutral B mesons to Ξ› 0 and Ξ© c ( * ) 0 using 711 fb βˆ’ 1 of data collected at the Ο’ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e βˆ’ collider. We observe no evidence of signal from any such decays and set 95% confidence-level upper limits on the products of B 0 and B Β― 0 branching fractions for these two-body decays with B ( Ξ© c 0 β†’ Ο€ + Ξ© βˆ’ ) in the range between 9.5 Γ— 10 βˆ’ 8 and 31.2 Γ— 10 βˆ’ 8 . Published by the American Physical Society 2024

Savinov, V. (ORCID:0000000291842830)β†—
DOE OSTI2024

Search for a heavy neutral lepton that mixes predominantly with the tau neutrino

We report a search for a heavy neutral lepton (HNL) that mixes predominantly with Ξ½ Ο„ . The search utilizes data collected with the Belle detector at the KEKB asymmetric energy e + e βˆ’ collider. The data sample was collected at and just below the center-of-mass energies of the Ο’ ( 4 S ) and Ο’ ( 5 S ) resonances and has an integrated luminosity of 915 fb βˆ’ 1 , corresponding to ( 836 Β± 12 ) Γ— 10 6 e + e βˆ’ β†’ Ο„ + Ο„ βˆ’ events. We search for production of the HNL (denoted N ) in the decay Ο„ βˆ’ β†’ Ο€ βˆ’ N followed by its decay via N β†’ ΞΌ + ΞΌ βˆ’ Ξ½ Ο„ . The search focuses on the parameter-space region in which the HNL is long-lived, so that the ΞΌ + ΞΌ βˆ’ originate from a common vertex that is significantly displaced from the collision point of the KEKB beams. Consistent with the expected background yield, one event is observed in the data sample after application of all the event-selection criteria. We report limits on the mixing parameter of the HNL with the Ο„ neutrino as a function of the HNL mass. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Search for the semileptonic decays Ξ c 0 β†’ Ξ 0 β„“ + β„“ βˆ’ at Belle

Using the full data sample of 980 fb βˆ’ 1 collected with the Belle detector at the KEKB asymmetric energy electron-positron collider, we report the results of the first search for the rare semileptonic decays Ξ c 0 β†’ Ξ 0 β„“ + β„“ βˆ’ ( β„“ = e or ΞΌ ). No significant signals are observed in the Ξ 0 β„“ + β„“ βˆ’ invariant-mass distributions. Taking the decay Ξ c 0 β†’ Ξ βˆ’ Ο€ + as the normalization mode, we report 90% credibility upper limits on the branching fraction ratios B ( Ξ c 0 β†’ Ξ 0 e + e βˆ’ ) / B ( Ξ c 0 β†’ Ξ βˆ’ Ο€ + ) < 6.7 Γ— 10 βˆ’ 3 and B ( Ξ c 0 β†’ Ξ 0 ΞΌ + ΞΌ βˆ’ ) / B ( Ξ c 0 β†’ Ξ βˆ’ Ο€ + ) < 4.3 Γ— 10 βˆ’ 3 based on the phase-space assumption for signal decays. The 90% credibility upper limits on the absolute branching fractions of B ( Ξ c 0 β†’ Ξ 0 e + e βˆ’ ) and B ( Ξ c 0 β†’ Ξ 0 ΞΌ + ΞΌ βˆ’ ) are found to be 9.9 Γ— 10 βˆ’ 5 and 6.5 Γ— 10 βˆ’ 5 , respectively. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Search for the decay B s 0 β†’ J / ψ Ο€ 0 at Belle experiment

We have analyzed 121.4 fb βˆ’ 1 of data collected at the Ο’ ( 5 S ) resonance by the Belle experiment using the KEKB asymmetric-energy e + e βˆ’ collider to search for the decay B s 0 β†’ J / ψ Ο€ 0 . We observe no signal and report an upper limit on the branching fraction B ( B s 0 β†’ J / ψ Ο€ 0 ) of 1.21 Γ— 10 βˆ’ 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 a dark leptophilic scalar produced in association with Ο„ + Ο„ βˆ’ pair in e + e βˆ’ annihilation at center-of-mass energies near 10.58 GeV

A dark leptophilic scalar ( Ο• L ) is a hypothetical particle that couples only to leptons rather than quarks. We report on a search for Ο• L in the e + e βˆ’ β†’ Ο„ + Ο„ βˆ’ Ο• L , Ο• L β†’ β„“ + β„“ βˆ’ ( β„“ = e , ΞΌ ) process using 626 fb βˆ’ 1 of data collected by the Belle experiment near the Ο’ ( 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 Ο• 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 Ο• 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)β†—
DOE OSTI2024

Search for baryon and lepton number violating decays D β†’ p β„“

We search for the baryon and lepton number violating charm decays, D β†’ p β„“ , where D is either a D 0 or a D Β― 0 and β„“ is a muon or an electron, using a data sample of 921 fb βˆ’ 1 collected by the Belle detector at the KEKB asymmetric energy e + e βˆ’ collider. In the absence of significant signals, we set upper limits on the branching fractions in the range ( 5 – 8 ) Γ— 10 βˆ’ 7 at a 90% confidence level, depending on the decay mode. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2023

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

We measure the branching fraction for the Cabibbo-suppressed decay D 0 β†’ 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 β†’ K $^{0}_{S}$ ⁒π + ⁒π - ; the result is $\mathscr{B}$⁑( D 0 β†’ K $^{0}_{S}$ K $^{0}_{S}$ ⁒π + ⁒π - )=[4.79Β±0.08⁒(stat)Β±0.10⁒(syst)Β±0.31⁒(norm)]Γ—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 =[-2.51Β±1.44⁒(stat)$^{+0.11}_{-0.10}$⁒(syst)]%, and a$^{T}_{CP}$=[-1.95Β±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

Measurement of the mass and width of the Ξ› c ⁒(2625) + charmed baryon and the branching ratios of Ξ› c ⁒(2625) + β†’ Ξ£$^{0}_{c}$Ο€ + and Ξ› c ⁒(2625) + β†’ Ξ£$^{++}_{c}$Ο€ -

Using the entire data sample of 980 fb -1 collected at or near the Y⁑(4⁒S) resonance with the Belle detector operating at the KEKB asymmetric-energy e + ⁒e - collider, we report the measurement of the mass, width, and the branching ratios of the Ξ› c (2625) + charmed baryon. The mass difference between Ξ› c ⁒(2625) + and Ξ›$^{+}_{c}$ is measured to be M⁑(Ξ› c ⁒(2625) + )-M⁑(Ξ›$^{+}_{c}$)=341.518Β±0.006Β±0.049 MeV/c 2 . The upper limit on the width is measured to be Γ⁑(Ξ› c ⁒(2625) + )<0.52 MeV/c 2 at 90% confidence level. Based on a full Dalitz plot fit, branching ratios with respect to the mode Ξ› c⁒ (2625) + β†’Ξ›$^{+}_{c}$Ο€ + ⁒π - are measured to be $\frac{\mathscr{B}⁑(Ξ›_c(2625)^+ β†’ Ξ£^{0}_{c}Ο€^+)} {\mathscr{B}⁑(Ξ›_c(2625)^+ β†’ ^{+}_{c}⁒π^+⁒π^-)}$ = (5.19Β±0.23Β±0.40)% and $\frac{\mathscr{B}(Ξ›_c (2625)^+ β†’ Ξ£{_c^+}^+ Ο€^-)}{\mathscr{B}(Ξ›_c (2625)^+ β†’ Ξ›{_c^+} Ο€^+Ο€^-)}$ = (5.13Β±0.26Β±0.32)%, where the first and second uncertainties are statistical and systematic, respectively. These measurements can be used to further constrain the parameters of the underlying theoretical models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the branching fraction of Ξ c 0 β†’ Ξ› c + Ο€ - at Belle

Based on a data sample of 983 fb -1 collected with the Belle detector at the KEKB asymmetric-energy e + ⁒e - collider, we present the study of the heavy-flavor-conserving decay Ξ$^{0}_{c}$ β†’ Ξ›$^{+}_{c}$⁒π - with Ξ›$^{+}_{c}$ reconstructed via its p⁒K - Ο€ + decay mode. The branching fraction ratio $\mathscr{B}$⁑(Ξ$^{0}_{c}$ β†’ Ξ›$^{+}_{c}$⁒π - )/$\mathscr{B}$⁑(Ξ$^{0}_{c}$ β†’ Ξ - Ο€ + ) is measured to be 0.38 Β±0.04 Β±0.04. Combining with the world average value of $\mathscr{B}$(Ξ$^{0}_{c}$ β†’ Ξ - Ο€ + ), the branching fraction $\mathscr{B}$⁑(Ξ$^{0}_{c}$ β†’ Ξ›$^{+}_{c}$⁒π - ) is deduced to be (0.54 Β±0.05 Β±0.05 Β±0.12)%. Here, the uncertainties above are statistical, systematic, and from $\mathscr{B}$⁑(Ξ$^{0}_{c}$ β†’ Ξ - Ο€ + ), respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurements of branching fractions of Ξ›$^{+}_{c}$ β†’ Ξ£ + ⁒η and Ξ›$^{+}_{c}$ β†’ Ξ£ + ⁒η' and asymmetry parameters of Ξ›$^{+}_{c}$ β†’ Ξ£ + ⁒π 0 , Ξ›$^{+}_{c}$ β†’ Ξ£ + ⁒η, and Ξ›$^{+}_{c}$ β†’ Ξ£ + ⁒η'

We report a study of Ξ› c + β†’ Ξ£ + Ο€ 0 , Ξ› c + β†’ Ξ£ + Ξ· , and Ξ› c + β†’ Ξ£ + Ξ· ' using the data sample corresponding to an integrated luminosity of 980 fb - 1 collected with the Belle detector at the KEKB asymmetric-energy e + e - collider. The branching fractions relative to Ξ› c + β†’ Ξ£ + Ο€ 0 are measured as B Ξ› c + β†’ Ξ£ + Ξ· / B Ξ› c + β†’ Ξ£ + Ο€ 0 = 0.25 Β± 0.03 Β± 0.01 and B Ξ› c + β†’ Ξ£ + Ξ· ' / B Ξ› c + β†’ Ξ£ + Ο€ 0 = 0.33 Β± 0.06 Β± 0.02 . Using B Ξ› c + β†’ Ξ£ + Ο€ 0 = ( 1.25 Β± 0.10 ) % , we obtain B Ξ› c + β†’ Ξ£ + Ξ· = ( 3.14 Β± 0.35 Β± 0.17 Β± 0.25 ) Γ— 10 - 3 and B Ξ› c + β†’ Ξ£ + Ξ· ' = ( 4.16 Β± 0.75 Β± 0.25 Β± 0.33 ) Γ— 10 - 3 . Here the uncertainties are statistical, systematic, and from B Ξ› c + β†’ Ξ£ + Ο€ 0 , respectively. The ratio of the branching fraction of Ξ› c + β†’ Ξ£ + Ξ· ' with respect to that of Ξ› c + β†’ Ξ£ + Ξ· is measured to be B Ξ› c + β†’ Ξ£ + Ξ· ' / B Ξ› c + β†’ Ξ£ + Ξ· = 1.34 Β± 0.28 Β± 0.08 . We update the asymmetry parameter of Ξ› c + β†’ Ξ£ + Ο€ 0 , Ξ± Ξ£ + Ο€ 0 = - 0.48 Β± 0.02 Β± 0.02 , with a considerably improved precision. The asymmetry parameters of Ξ› c + β†’ Ξ£ + Ξ· and Ξ› c + β†’ Ξ£ + Ξ· ' are measured to be Ξ± Ξ£ + Ξ· = - 0.99 Β± 0.03 Β± 0.05 and Ξ± Ξ£ + Ξ· ' = - 0.46 Β± 0.06 Β± 0.03 for the first time.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗