107 research outputs found
Hadron shower decomposition in the highly granular CALICE analogue hadron calorimeter
The spatial development of hadronic showers in the CALICE scintillator-steel
analogue hadron calorimeter is studied using test beam data collected at CERN
and FNAL for single positive pions and protons with initial momenta in the
range from 10 to 80 GeV/c. Both longitudinal and radial development of hadron
showers are parametrised with two-component functions. The parametrisation is
fit to test beam data and simulations using the QGSP_BERT and FTFP_BERT physics
lists from Geant4 version 9.6. The parameters extracted from data and simulated
samples are compared for the two types of hadrons. The response to pions and
the ratio of the non-electromagnetic to the electromagnetic calorimeter
response, h/e, are estimated using the extrapolation and decomposition of the
longitudinal profiles.Comment: 38 pages, 19 figures, 5 tables; author list changed; submitted to
JINS
B-flavor tagging at Belle II
We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom ( ) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb−1
, collected at the resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be
εeff=(30.0±1.2(stat)±0.4(syst))%
for a category-based algorithm and
εeff=(28.8±1.2(stat)±0.4(syst))%
for a deep-learning-based algorithm
Observation of decays using the 2019-2022 Belle II data sample
We present a measurement of the branching fractions of four decay modes. The measurement is based on data from
SuperKEKB electron-positron collisions at the resonance
collected with the Belle II detector and corresponding to an integrated
luminosity of . The event yields are extracted from fits
to the distributions of the difference between expected and observed meson
energy to separate signal and background, and are efficiency-corrected as a
function of the invariant mass of the system. We find the branching
fractions to be: where the first uncertainty is statistical and
the second systematic. These results include the first observation of
, , and decays and a significant improvement in the precision
of compared to previous measurements
Measurement of the integrated luminosity of the Phase 2 data of the Belle II experiment
From April to July 2018, a data sample at the peak energy of the γ(4S) resonance was collected with the Belle II detector at the SuperKEKB electron-positron collider. This is the first data sample of the Belle II experiment. Using Bhabha and digamma events, we measure the integrated luminosity of the data sample to be (496.3 ± 0.3 ± 3.0) pb-1, where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle II
Reconstruction of decays identified using hadronic decays of the recoil meson in 2019 -- 2021 Belle II data
We present results on the semileptonic decays and in a sample corresponding to
189.9/fb of Belle II data at the SuperKEKB collider. Signal decays
are identified using full reconstruction of the recoil meson in hadronic
final states. We determine the total branching fractions via fits to the
distributions of the square of the "missing" mass in the event and the dipion
mass in the signal candidate and find and where the dominant
systematic uncertainty comes from modeling the nonresonant contribution
Precise Measurement of the D and D Lifetimes at Belle II
We report a measurement of the D and D lifetimes using D→Kπ and D→Kππ decays reconstructed in ee→ data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy ee collider. The data, collected at center-of-mass energies at or near the Υ(4S) resonance, correspond to an integrated luminosity of 72 fb. The results, τ(D)=410.5±1.1(stat)±0.8(syst) fs and τ(D)=1030.4±4.7(stat)±3.1(syst) fs, are the most precise to date and are consistent with previous determinations
Measurements of the branching fractions for decays at Belle II
This paper reports a study of decays using
fb of data collected during 2019--2020 by the Belle II experiment at the
SuperKEKB asymmetric-energy collider, corresponding to events. We find , ,
, and signal events in the decay modes , ,
, and , respectively. The uncertainties quoted for the
signal yield are statistical only. We report the branching fractions of these
decays: where the first
uncertainty is statistical, and the second is systematic. The results are
consistent with world-average values
Determination of from untagged decays using 2019-2021 Belle II data
We present an analysis of the charmless semileptonic decay , where , from 198.0 million pairs of
mesons recorded by the Belle II detector at the SuperKEKB
electron-positron collider. The decay is reconstructed without identifying the
partner meson. The partial branching fractions are measured independently
for and as functions of
(momentum transfer squared), using 3896 and
5466 decays. The total branching fraction is
found to be for decays, where the uncertainties are statistical and
systematic, respectively. By fitting the measured partial branching fractions
as functions of , together with constraints on the nonperturbative
hadronic contribution from lattice QCD calculations, the magnitude of the
Cabibbo-Kobayashi-Maskawa matrix element , , is extracted. Here, the first uncertainty is
statistical, the second is systematic and the third is theoretical
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