Engineering topics

Kaliyar, A. B. (ORCID:000000022211619X)

Publications and source records attributed to Kaliyar, A. B. (ORCID:000000022211619X).

At least 19 records

DOE OSTI2025

Production cross sections of light and charmed mesons in 𝑒 + ⁢𝑒 − annihilation near 10.58 GeV

We report measurements of production cross sections for 𝜌 + , 𝜌 0 , 𝜔, 𝐾* + , 𝐾* 0 , 𝜙, 𝜂, 𝐾$^0_𝑆$, 𝑓 0 ⁡(980), 𝐷 + , 𝐷 0 , 𝐷$^+_𝑠$, 𝐷* + , 𝐷* 0 , and 𝐷*$^+_𝑠$ in 𝑒 + ⁢𝑒 − collisions at a center-of-mass energy near 10.58 GeV. The data were recorded by the Belle experiment, consisting of 571 fb −1 at 10.58 GeV and 74 fb −1 at 10.52 GeV. Production cross sections are extracted as a function of the fractional hadron momentum 𝑥 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 measurements—when available—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 𝑥 𝑝 shapes.

fragmentation functions↗

DOE OSTI2024

Angular analysis of B → K * e + e − in the low- q 2 region with new electron identification at Belle

We perform an angular analysis of the B → K * e + e − 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 → K + π − and K * + → K S 0 π + 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 ( ′ ) . We perform a fit to the B → K * e + e − differential decay rate and measure the imaginary component of the transversality amplitude to be A T Im = − 1.27 ± 0.52 ± 0.12 , and the K * transverse asymmetry to be A T ( 2 ) = 0.52 ± 0.53 ± 0.11 , with F L and A T Re fixed to the Standard Model values. The resulting constraints on the value of C 7 ′ are consistent with the Standard Model within a 2 σ confidence interval. Published by the American Physical Society 2024

Ferlewicz, D. (ORCID:0000000243741234)↗

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 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 OSTI2023

Evidence for B 0 → p Σ ¯ 0 π - at Belle

We search for the B 0 → p$\overline{Σ}$ 0 π - decay with $\overline{Σ}$ 0 → $\overline{Λ}$ γ, where the γ is not measured, using a data sample corresponding to an integrated luminosity of 711 fb -1 which contains 772 × 10 6 B$\overline{B}$ pairs, collected around the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. We measure for the first time the B 0 → p$\overline{Σ}$ 0 π - branching fraction to be $\mathscr{B}$(B 0 → p$\overline{Σ}$ 0 π - ) = $({1.17}_{-0.40}^{+0.43} (stat) ± 0.07(syst))$ X 10 -6 with a significance of 3.0σ. We simultaneously measure the branching fraction for the related channel B 0 → p$\overline{Λ}$ π - with much improved precision.

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 OSTI2023

Search for the double-charmonium state with ηcJ/ψ at Belle

We measure the cross section of e + e - → ηcJ/ψ at the Υ(nS)(n = 1–5) on-resonance and 10.52 GeV off-resonance energy points using the full data sample collected by the Belle detector with an integrated luminosity of 955 fb -1 . We also search for double charmonium production in e + e - → ηcJ/ψ via initial state radiation near the ηcJ/ψ threshold. No evident signal of the double charmonium state is found, but evidence for the e + e - → ηcJ/ψ process is found with a statistical significance greater than 3.3σ near the ηcJ/ψ threshold. The average cross section near the threshold is measured and upper limits of cross sections are set for other regions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Study of the muon decay-in-flight in the τ - → μ - ν ¯ μ ν τ decay to measure the Michel parameter ξ '

We present the first measurement of the Michel parameter ξ' in the $\tau$ - → μ¯ $\overline{v}$ μ v $\tau$ decay using the full data sample of 988 fb -1 collected by the Belle detector operating at the KEKB asymmetric energy e + ⁢e - collider. The method is based on the reconstruction of the μ¯ → e⁢¯$\overline{v}$ e v μ decay-in-flight in the Belle central drift chamber and relies on the correlation between muon spin and its daughter electron momentum. We study the main sources of the background that can imitate the signal decay, such as kaon and pion decays-in-flight and charged particle scattering on the detector material. Highly efficient methods of their suppression are developed and applied to select 165 signal-candidate events. We obtain ξ' = 0.22±0.94±0.42 where the first uncertainty is statistical, and the second one is systematic. The result is in agreement with the Standard Model prediction of ξ' = 1.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

First measurement of the Q 2 distribution of X⁡(3915) single-tag two-photon production

We report the first measurement of the Q 2 distribution of X⁡(3915) produced by single-tag two-photon interactions. The decay mode used is X⁡(3915) →J/Ψ⁢ω. The covered Q 2 region is from 1.5 (GeV/c) 2 to 10.0 (GeV/c) 2 . We observe 7.9 ± 3.1⁢(stat) ± 1.5⁢(syst) events, where we expect 4.1 ± 0.7 events based on the Q 2 = 0 result from the no-tag two-photon process, extrapolated to higher Q 2 region using the $c\bar{c}$ model of Schuler, Berends, and van Gulik. The shape of the distribution is also consistent with this model; we note that statistical uncertainties are large

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

First Measurement of the Michel Parameter ξ ' in the τ - → μ - ν ¯ μ ν τ Decay at Belle

We report the first measurement of the Michel parameter ξ' in the $\tau$ - →μ - ⁢ $\overline{v}$ μ ⁢v $\tau$ decay with a new method proposed just recently. The measurement is based on the reconstruction of the $\tau$ - →μ -⁢ $\overline{v}$ μ v $\tau$ events with subsequent muon decay in flight in the Belle central drift chamber. The analyzed data sample of 988 fb -1 collected by the Belle detector corresponds to approximately 912×10 6 $\tau$ + ⁢$\tau$ - pairs. We measure ξ'=0.22±0.94⁢(stat)±0.42⁢(syst), which is in agreement with the standard model prediction of ξ' =1. Statistical uncertainty dominates in this study, being a limiting factor, while systematic uncertainty is well under control. Our analysis proved the practicability of this promising method and its prospects for further precise measurement in future experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Measurement of differential distributions of B → D*$\ell\bar{v}_{\ell}$ and implications on | V cb |

We present a measurement of the differential shapes of exclusive B → D*$\ell\bar{v}_{\ell}$ (B = B - , $\bar{B}$ 0 and $\ell$ = e, μ) decays with hadronic tag-side reconstruction for the full 711 fb -1 Belle dataset. We extract the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) form factor parameters and use an external input for the absolute branching fractions to determine the Cabibbo-Kobayashi-Maskawa matrix element and find |V cb | CLN = (40.2 ± 0.9) x 10 -3 and |V cb | BGL = (40.7 ± 1.0) x 10 -3 with the zero-recoil lattice QCD point $\mathcal{F}$(1) = 0.906 ± 0.013. We also perform a study of the impact of beyond zero-recoil lattice QCD calculations on the |V cb | determinations. Additionally, we present the lepton-flavor universality ratio R eμ = $\mathcal{B}$(B → D*e$\bar{v}$ e )/$\mathcal{B}$(B → D*μ$\bar{v}$ μ ) = 0.993 ± 0.023 ± 0.023, the electron and muon forwardbackward asymmetry and their difference ΔA FB = 0.028 ± 0.028 ± 0.008, and the electron and muon D* longitudinal polarization fraction and their difference ΔF$^{D*}_L$ = 0.030 ± 0.025 ± 0.007. The uncertainties quoted correspond to the statistical and systematic uncertainties, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

Search for the Lepton Flavor Violating Decays B + → K + τ ± ℓ ∓ ( ℓ = e , μ ) at Belle

We present a search for the lepton flavor violating decays B + → K + ⁢$\tau$ ±⁢ ℓ ∓ , with ℓ = (e,μ), using the full data sample of 772×10 6 B$\overline{B}$ pairs recorded by the Belle detector at the KEKB asymmetric-energy e + ⁢e - collider. We use events in which one B meson is fully reconstructed in a hadronic decay mode. We find no evidence for B ± → K ±⁢ $\tau$⁢ℓ decays and set upper limits on their branching fractions at the 90% confidence level in the (1 - 3) × 10 -5 range. The obtained limits are the world’s best results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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

First Measurement of the B + → π + π 0 π 0 Branching Fraction and C P Asymmetry

We study B + → π + π 0 π 0 using 711 fb -1 of data collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. Here we measure an inclusive branching fraction of (19.0 ±1.5 ±1.4)×10 -6 and an inclusive CP asymmetry of (9.2 ±6.8 ±0.7)%, where the first uncertainties are statistical and the second are systematic, and a B + → ρ(770) + π 0 branching fraction of (11.2 ± 1.1 ± 0.9 $^{+0.8}_{-1.6}$)× 10 -6 , where the third uncertainty is due to possible interference with B + → ρ(1450) + π 0 . We present the first observation of a structure around 1 GeV/c 2 in the π 0 π 0 mass spectrum, with a significance of 6.4σ, and measure a branching fraction to be (6.9 ±0.9 ±0.6) × 10 -6 . We also report a measurement of local CP asymmetry in this structure.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Study of e + e - → Σ 0 Σ ¯ 0 and Σ + Σ ¯ - by initial state radiation method at Belle

The processes e + ⁢e - →Σ 0 ⁢$\overline{Σ}$ 0 and e + ⁢e - →Σ + ⁢$\overline{Σ}$ - are studied using initial-state-radiation events in a sample of 980 fb -1 collected with the Belle detector at the KEKB asymmetric-energy e + ⁢e - collider. The cross sections from the mass threshold to 3 GeV/c 2 and the effective form factors of Σ 0 and Σ + are measured. In the charmonium region, we observe the decays J/ψ →Σ 0 ⁢$\overline{Σ}$ 0 and J/ψ →Σ + ⁢$\overline{Σ}$ - and determine the respective branching fractions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

First Observation of Λπ + and Λπ - Signals near the $\bar{K}$N⁡(I=1) Mass Threshold in Λ$^+_c$ → Λ⁢π + ⁢π + π - Decay

Using the data sample of 980 fb -1 collected with the Belle detector operating at the KEKB asymmetric-energy e + ⁢e - collider, we present the results of an investigation of the Λ⁢π + and Λ⁢π - invariant mass distributions looking for substructure in the decay Λ$^+_c$ → Λ⁢π + π + π - . We find a significant signal in each mass distribution. When interpreted as resonances, we find for the Λπ + (Λ⁢π - ) combination a mass of 1434.3 ± 0.6⁢(stat) ± 0.9⁢(syst) MeV/c 2 [1438.5 ± 0.9⁢(stat) ± 2.5⁢(syst) MeV/c 2 ], an intrinsic width of 11.5 ± 2.8⁢(stat) ± 5.3⁢(syst) MeV/c 2 [33.0 ± 7.5⁢(stat) ± 23.6⁢(syst) MeV/c 2 ] with a significance of 7.5⁢σ (6.2⁢σ). As these two signals are very close to the $\bar{K}N$ threshold, we also investigate the possibility of a $\bar{K}N$ cusp, and find that we cannot discriminate between these two interpretations due to the limited size of the data sample.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Search for the decay B s 0 → π 0 π 0 at Belle

We report the results of the first search for the decay B$^{0}_{s}$ → π 0 ⁢π 0 using 121.4 fb -1 of data collected at the Y⁡(5⁢S) resonance with the Belle detector at the KEKB asymmetric-energy e + ⁢e - collider. We observe no signal and set a 90% confidence level upper limit of 7.7 ×10 -6 on the B$^{0}_{s}$ → π 0 π 0 decay branching fraction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Angular analysis of the low K + K – invariant mass enhancement in B + →K + K – π + decays

We study the decay B + →K + K – π + and investigate the angular distribution of K + K – pairs with invariant mass below 1.1 GeV / c 2 . This region exhibits both a strong enhancement in signal and very large direct CP violation. We construct a coherent sum model for the angular distribution of the S- and P-wave, and report the ratio of their amplitudes, the relative phase and the forward-backward asymmetry. We also report absolute differential branching fractions and direct CP asymmetry for the decay in bins of M K+K– and the differential branching fractions in bins of M K+π– . The results are based on a data sample that contains 772 × 10 6 $B\bar{B}$ pairs collected at the $Υ$(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e – collider. The result favors the presence of S- and D-waves in low M K+K– region to the detriment of a P-wave.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗