8 research outputs found
Study Of The Decay B^± → K^0_s Π^± Π^0 At The Belle Experiment
Belle is a particle physics experiment based at the KEK laboratory in Tsukuba Japanwhich ran from 1999 to 2010 and collected 1ab−1 of data. The Belle experiment is focused on studying the properties of particles called B mesons which are produced by accelerating and colliding electron and positron beams. These B mesons show the biggest differences between the properties of matter and anti-matter of any known particles. One of the main goals of the Belle experiments is to understand the differences between matter and anti-matter, specifically violations of charge-parity symmetry (CP violation) and how anti-matter vanished and we come to live in a matter dominated universe. In this dissertation, I explore the charmless B decay B± → Ks0π±π0 with the Belle full Monti-Carlo (full MC) simulation and Belle data corresponding to 571f b−1 of luminosity and measure the decay’s branching fraction(BF). Charmless transitions can proceed by a b → u transition via a tree level diagram or b → s or d transition via the so-called penguin diagram. Both decay types are highly suppressed compared to the b → c transition and we expect a small branching fraction, smaller than 10−5. Penguin processes are important in B-meson charmless decays, thus it is possible to have contributions of unknown particles in the loop process leading to CP-violation contribution from Beyond Standard Model. Charmless B decays are sensitive to the angle γ (aka ϕ3) in the unitary triangle and open a new window to analyze the CP violation process.
I use the innovative Belle II software (basf2) for the initial reconstruction process. Thechallenge in observing the B± → Ks0π±π0 decay is to suppress backgrounds from continuum events, which do not contain b quarks, and background from other B meson decays. I use direct selections such as beam-energy constrained mass (Mbc), energy difference (∆E), probability of the vertex fit result (ChiProb), and others, on several variables to remove background from B± → Ks0π±π0 events. I find such an approach is insufficient. I found it was necessary to use a multi-variate analysis (MVA) machine learning/artificial intelligence technique called a boosted decision tree (BDT) to reduce the backgrounds to the level to allow me to clearly observe the decay and measure the BF. I compare my results with unpublished results from the BaBar experiment. Additionally I use the Dalitz plot (DP) technique to study the intermediate resonance contributions in this decay. I use the Laura++ software to generate and fit toy Monte Carlo(toy MC), full Monte Carlo simulated data, and, based on the techniques developed on these simulations, the experimental data to study the resonance sub-structure of this decay
Measurement of the branching fractions for Cabibbo-suppressed decays and at Belle
International audienceWe present measurements of the branching fractions for the singly Cabibbo-suppressed decays and , and the doubly Cabibbo-suppressed decay , based on 980 of data recorded by the Belle experiment at the KEKB collider. We measure these modes relative to the Cabibbo-favored modes and . Our results for the ratios of branching fractions are , , and , where the uncertainties are statistical and systematic, respectively. The second value corresponds to , where is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for and yields , , and , where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction
Measurement of the production ratio in collisions at the resonance using decays at Belle
We measure the ratio of branching fractions for the decays to and using and samples, where stands for ( or ), with fb of data collected at the resonance with the Belle detector. We find the decay rate ratio of over to be , which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is systematic due to the assumption of isospin symmetry in
Measurement of branching fractions of and at Belle
We present a study of a singly Cabibbo-suppressed decay and a Cabibbo-favored decay based on 980 of data collected by the Belle detector, operating at the KEKB energy-asymmetric collider. We measure their branching fractions relative to : and . Combining with the world average , we have the absolute branching fractions: and . The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the uncertainty on . The mode is observed for the first time and has a statistical significance of . The branching fraction of has been measured with a threefold improvement in precision over previous results and is found to be consistent with the world average
Measurement of the lifetime at Belle II
We report on a measurement of the lifetime using decays reconstructed in data collected by the Belle II experiment and corresponding to of integrated luminosity. The result, , agrees with recent measurements indicating that the is not the shortest-lived weakly decaying charmed baryon
Measurement of the lifetime at Belle II
We report on a measurement of the lifetime using decays reconstructed in data collected by the Belle II experiment and corresponding to of integrated luminosity. The result, , agrees with recent measurements indicating that the is not the shortest-lived weakly decaying charmed baryon
Measurement of the lifetime at Belle II
We report on a measurement of the lifetime using decays reconstructed in data collected by the Belle II experiment and corresponding to of integrated luminosity. The result, , agrees with recent measurements indicating that the is not the shortest-lived weakly decaying charmed baryon
Test of light-lepton universality in decays with the Belle II experiment
International audienceWe present a measurement of the ratio of branching fractions of the lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB collider. The sample has an integrated luminosity of 362 fb at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, , where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the boson in decays of , in agreement with the standard model expectation of unity