The semileptonic $B$ meson decays of the type $B \to X_u \ell ν$ are important for measuring the magnitude of the CKM matrix element $V_{ub}$. Recent measurements of inclusive $B \to X_u e ν_e$ and hadronically tagged $B^0 \to π^- \ell^+ ν$ from the Belle II experiment are presented. The results are obtained using the data collected at Belle II between March 2019 and March 2020, with a total integrated luminosity of 37.8 ${\rm fb}^{-1}$. These preliminary measurements are used to validate the detector and reconstruction software performance. The measured preliminary branching fraction of $B^0 \to π^- \ell^+ ν$ decays is $(1.58 \pm 0.43_{\textrm{stat}} \pm 0.07_{\textrm{sys}})\cdot 10^{-4}$, which is in agreement with the world average, $(1.50 \pm 0.06)\cdot 10^{-4}$.
Evidence for the inclusive $B \to X_s \ell^+ \ell^-$ decay has been presented based on 41.8 fb-1 data sample collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric e+e- collider. A preliminary result for the branching fraction is B($B \to X_s \ell^+ \ell^-$) = (7.1 +- 1.6 (stat.) + 1.4 - 1.2(syst.)) \times 10^-6.
We discuss the latest results and future prospects of the Belle experiment on the electroweak and radiative processes b --> s ell+ ell-, b --> s gamma and b --> d gamma. In particular, the first measurement of the inclusive rate for B --> X(s) ell+ ell- provides a new constraint on the physics beyond the Standard Model. The yet to be measured decay B --> rho gamma is expected to provide a new constraint on the CKM matrix element |V(td)| in the near future.
We present a search for the B-> pi e^+ e^- and B-> pi μ^+ μ^- decays, with a data sample of 657 million BBbar pairs collected with the Belle detector at the KEKB $e^+e^-$ collider. Signal events are reconstructed from a charged or a neutral pion candidate and a pair of oppositely charged electrons or muons. No significant signal is observed and we set the upper limit on the isospin-averaged branching fraction BF(B -> π\ell^+\ell^-) < 6.2x10^-8 at the 90% confidence level.
We report on the measurement of inclusive charmless semileptonic B decays $B \to X_{u} \ell ν$. The analysis makes use of hadronic tagging and is performed on the full data set of the Belle experiment comprising 772 million $B\bar{B}$ pairs. In the proceedings, the preliminary results of measurements of partial branching fractions and the CKM matrix element $|V_{ub}|$ are presented.
We report on the results of penguin-mediated B decays at the Belle experiment. The analyses were based on approximately 32 million $B\bar{B}$ events collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ storage ring. The $b \to s γ$ transition was studied through exclusive decays: $B \to K^{*} γ$, $B^0 \to K_{2}^{*}(1430)^0 γ$, $B^+ \to K^+π^-π^- γ$, $B^+ \to K^{*0} π^+ γ$ and $B^+ \to K^+ρ^0 γ$. The $b \to s \ell^+ \ell^-$ transition was searched through both exclusive decays, $B \to K^{(*)} \ell^+ \ell^-$, and inclusive decay, $B \to X_{s} \ell^+ \ell^-$. We observe…
We have searched for neutrinoless $τ$ lepton decays into $\ell$ and $V^0$, where $\ell$ stands for an electron or muon, and $V^0$ for a vector meson ($ϕ$, $ω$, $K^{*0}$, $\bar{K}^{*0}$ or $ρ^0$), using 543 fb$^{-1}$ of data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No excess of signal events over the expected background has been observed, and we set upper limits on the branching fractions in the range $(5.9-18) \times 10^{-8}$ at the 90% confidence level. These upper limits include the first results for the $\ell ω$ mode as well as new limits that are s…
We report a preliminary study of the branching fractions and $q^2$ distributions of exclusive charmless semileptonic B decays, using events tagged by fully reconstructing one of the $B$ mesons in a hadronic decay mode. These results are obtained from a data sample that contains 535 $\times 10^6\ B\bar{B}$ pairs, collected near the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+ e^-$ collider.
We have searched for neutrinoless $τ$ lepton decays into $\ell$ and $V^0$, where $\ell$ stands for an electron or muon, and $V^0$ for a vector meson ($ϕ$, $ω$, $K^{*0}$ or $\bar{K}^{*0}$), using 543 fb$^{-1}$ of data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No excess of signal events over the expected background is observed, and we set upper limits on the branching fractions in the range $(0.7 - 1.8) \times 10^{-7}$ at the 90% confidence level. These upper limits include the first results for $\ell ω$ as well as new limits that are $3.6 - 9.6$ times mo…
The Belle~II Collaboration presents four new analyses: The measurement of $V_{ub}$ from $B \to πe ν_e$ decays with a fit to the differential $q^2$ spectrum, the determination of $V_{cb}$ using a fit to the differential $w$ distribution from $B^0 \to D^{\ast -} \ell^+ ν_\ell$ decays, and the measurement of $q^2$ moments in inclusive $B \to X_c \ell ν_\ell$ decays. In all these analyses tag-side $B$ meson is reconstructed in a fully hadronic decay chain. The last result are branching fraction measurement of $B \to K^\ast \ell^+ \ell^-$ decays using an untagged approach.
We are reporting on a search for flavour-changing neutral current decays $D^0 \to μ^+ μ^-$ and $D^0 \to e^+ e^-$, and for lepton-flavour violating decays $D^0 \to e^\pm μ^\mp$, the measurement of $D^+_{(s)} \to K_S^0 π^+$ and $D^+_{(s)}\to K_S^0 K^+$ branching fractions, and the search for CP violation in $D^+_{(s)} \to K_S^0 π^+$ and $D^+_{(s)} \to K_S^0 K^+$ decays. The analyses are based on 600 fb$^{-1}$ to 700 fb$^{-1}$ of data collected in $e^+e^-$ collisions at the centre-of-mass (CM) energy of the $Υ(4S)$ resonance and 60 MeV below by the Belle detector at the KEKB collider.
Radiative and electroweak penguin mediated decays of $B$ mesons are a great probe for physics beyond the Standard Model of particle physics. Furthermore, recently anomalies on exclusive $b \rightarrow s \ell^{+} \ell^{-}$ processes, which may imply lepton flavor universality violation, have been observed. Belle II experiment sheds light on the anomalies with the measurement of an inclusive analysis in this mode. Thanks to smaller hadronic uncertainties compared with exclusive modes, complementary information can be provided. Belle II is also a unique experiment to search for processes involvin…
We present measurements of the first to fourth moments of the lepton mass squared $q^2$ of \mbox{$B \to X_c \, \ell\, \bar ν_{\ell}$} decays for $\ell = e, μ$ and with $X_c$ a hadronic system containing a charm quark. These results use a sample of electron-positron collisions at the $Υ(4S)$ resonance corresponding to $62.8 \, \mathrm{fb}^{-1}$ of integrated luminosity and collected by the Belle II experiment in 2019 and 2020. To identify the $X_c$ system and reconstruct $q^2$, one of the $B$ mesons from an $Υ(4S) \to B \kern 0.18em\overline{\kern -0.18em B}$ decay is fully reconstructed in a h…
Rare and flavour-changing neutral current decays of the B meson are an important probe in the search for physics beyond the Standard Model. There have recently been several anomalies in rare B decays, and lepton-universality measurements, specifically involving the $b\to s\ell^+\ell^-$ quark transition. These results tend towards a non-Standard-Model interpretation. The Belle II experiment is a next-generation b physics experiment located at SuperKEKB, an upgraded B factory $e^+e^-$ collider, in Tsukuba, Japan. The first collisions are expected in early 2018 with full physics data expected in …
With the first data being recorded at Belle II, we are at the brink of a new era in quark flavour physics. The many exciting new opportunities for Belle~II include a full angular analysis of inclusive ${\bar B \to X_{s} \, \ell^+\ell^-}$ which has the potential to reveal new physics, in particular by its interplay with the exclusive $b \to s \ell^+\ell^-$ counterparts studied extensively at LHCb. In this paper, we present fully updated Standard Model predictions for all angular observables necessary for this endeavour. These predictions are tailored to Belle II and include an elaborate study o…
We report a measurement of the branching fraction of inclusive semileptonic $B$ meson decays $B\to X_c\ellν\ell$ in $Υ(4S)\to B\bar B$~data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy $e^+e^-$ collider and corresponding to 62.8 fb$^{-1}$ of integrated luminosity. Only a charged lepton (electon or muon) is reconstructed and the signal yield is determined from a fit to the lepton momentum distribution in the center-of-mass frame of the colliding beams. Averaging the result in the electron and muon channels, we find ${\cal B}(B\to X_c\ellν_\ell) = (9.75\pm 0.03(\text{st…
The $b \rightarrow s γ$, $b \rightarrow d γ$ and $b \rightarrow s \ell^+ \ell^-$ processes are allowed at higher order via the electroweak loop or box diagrams in the Standard model. It is sensitive probe to search for new physics beyond the Standard model because new particles might enter in the loop. We present preliminary results of branching fraction of the $\bar{B} \rightarrow X_s γ$, $CP$ asymmetry in the $\bar{B} \rightarrow X_{s+d} γ$, and the forward-backward asymmetry in the $\bar{B} \rightarrow X_s \ell^+ \ell^-$. The results are based on a data sample containing $772 \times 10^6 B\…
The decays $\bar{B} \rightarrow D^{(*)} τ^- \barν_τ$ are good probes to new physics beyond the Standard Model. The ratios of branching fractions $R(D^{(*)}) \equiv \mathit{BF}(\bar{B} \rightarrow D^{(*)} τ^- \barν_τ) / \mathit{BF}(\bar{B} \rightarrow D^{(*)} \ell^- \barν_\ell)$ (where $\ell^- = e^-, μ^-$) measured by Belle, BaBar and LHCb show 3.9$σ$ deviation from the SM expectations as of 2015. In 2016, the Belle collaboration has shown two new measurements for the $\bar{B} \rightarrow D^{(*)} τ^- \barν_τ$ decay. These include the first application of the semileptonic tagging to the $R(D^*)$…
In this paper, we briefly review results on rare decays of $B$ mesons from the Belle experiment, based on 10.4 fb$^{-1}$ data collected on the $Υ$(4S) resonance. The topics include measurements of Cabibbo suppressed decays $B \to D^{(*)} K^{(*)}$, charmless two-body decays $B \to ππ$, $Kπ$, $KK$ and $B \to η^{'} h (h = K^+, π^+, K^0)$, and a search for flavor changing neutral current decays $B \to K^{(*)} \ell^{+} \ell^{-}$.
We present the measurement of the first to fourth order moments of the four-momentum transfer squared, $q^{2}$, of inclusive $B \rightarrow X_{c} \ell ν$ decays using the full Belle data set consisting of $711~\rm fb^{-1}$ of integrated luminosity at the $Υ(4S)$ resonance for $\ell = e, μ$. The measured moments are crucial experimental inputs for a novel, data-driven approach to determine inclusive $|V_{cb}|$, which we implement in order to extract a preliminary value of $|V_{cb}| \times 10^{3} = 41.7 \pm 1.2$.
The Belle experiment has measured the CKM angle $γ$ in a variety of ways. In this paper, we focused on the recent progress of time-dependent $γ$ analysis and the related measurements in Belle.
This proceeding summarizes the recent measurements of semileptonic $b\to u$ decays from the Belle experiment. These analyses use the full data set collected at the $Υ(4S)$ resonance at KEKB accelerator complex with a center-of-mass energy of $\sqrt{s} = 10.58$ GeV, which contains an integrated luminosity of 711 fb$^{-1}$ and corresponds to 772 million $Υ(4S) \to B\bar{B}$ events. In the sector of inclusive decay, the partial branching fraction of $B \to X_{u} \ell ν$ decays and the CKM matrix element $|V_{ub}|$ are measured with hadronic tagging. The first measurement of differential branching…
We report on the first Belle II measurements of branching fractions and CP-violating charge asymmetries in charmless $B$ decays. We use 34.6 fb$^{-1}$ from electron-positron collisions collected in 2019 and 2020 at the $Υ(4S)$ resonance. The results are compatible with known values and show performance already comparable with Belle.
We report recent measurements of the CKM angle phi_1/beta using large data samples collected by the Belle and BaBar experiments at the e^+ e^- asymmetric-energy colliders.
We report recent measurements of the Unitarity triangle angles phi_1 and phi_2 using large data samples collected with Belle and BaBar detectors at e+e- asymmetric-energy colliders.
Results on two inclusive Vub measurements at Belle are presented. We also present a new measurement of the branching fraction for Ds->phi pi. A data sample of 78.1fb^-1 accumulated using the Belle detector at the KEKB asymmetric e^+e^- collider operating at the Upsilon(4S) resonance is used. All results are preliminary.
We report recent results on $ϕ_3$ measurement at the Belle collaboration. The analyses reported here are based on a large data sample that contains 657 million $B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider at the $Υ(4S)$ resonance.
In this review recent studies on $CP$ violation and related hadronic $B$ decays by the Belle experiment, in particular measurements of CKM angles $ϕ_1$ and $ϕ_2$ are reported.
The Belle II collaboration operates a substantially upgraded Belle detector at the SuperKEKB energy-asymmetric e+ e- collider. Belle II will start recording collisions at the Upsilon(4S) energy in 2018, aiming to collect by 2025 50 ab^{-1} of data, 50 times more than the Belle experiment. We report prospects for measuring quantities associated with charge-parity violation, with special emphasis on the Cabibbo-Kobayashi-Maskawa angle phi_3 (gamma) and observables in semileptonic B meson decays associated with the quark-mixing matrix element Vub.
We report on absolute lifetime measurements of charmed hadrons using the data collected by the Belle II experiment between 2019 and 2021. The measured lifetimes of $D^0$, $D^+$, and $Λ_c^+$ are the most precise to date and consistent with previous measurements. Our result indicates that $Ω_c^0$ is not the shortest-living singly charmed baryon.
In this paper, we report on the results of the |Vcb| and |Vub| measurements obtained from studies of inclusive and exclusive semileptonic decays using 30fb^-1 of e^+e^- collision data collected by the Belle detector at KEKB.
Upgrades at the Belle II experiment and the SuperKEKB asymmetric-energy electron-positron collider enable precise measurements of particle decays. Even with early data, Belle II has made several world-leading measurements of particle lifetimes, which are useful as tests of effective models used in searches for physics beyond the standard model. Especially for charm hadrons, these effective models depend on careful consideration of non-perturbative effects to give an adequate description of lifetimes. Recent measurements at other experiments have stimulated particular interest in charm baryons,…
We report the recent measurements of $B^0\to J/ψπ^0$ and other CP violation modes based on the data collected by the Belle experiment at the KEKB collider. The CP asymmetry parameters for the decay $B^0\to J/ψπ^0$ have previously been measured by BaBar and Belle experiments, but the results of mixing induced CP asymmetry $[S=-η_f\sin(2ϕ_1)]$ were not in good agreement with each other. Furthermore, the BaBar result lies outside the physically allowed region. Previous Belle measurements were based on $535\times10^6$ $B\bar{B}$ pairs. We updated the measurements using the final Belle data set of …
We present measurements of time-dependent asymmetries in decays of neutral B mesons to the final states B0 -> rho+ pi-. Measurements are based on a 140 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
The Belle II experiment at the SuperKEKB energy-asymmetric $e^+ e^-$ collider is a substantial upgrade of the B factory facility, Belle, at the Japanese KEK laboratory. The main operation of SuperKEKB has started in March 2019, and collisions ran until July 2019, achieving a peak luminosity of $5.5\times 10^{33}$ cm$^{-2}$s$^{-1}$. The results presented here were obtained from a subset of collected data of 0.41 fb$^{-1}$. In the poster presented at the conference the first results from studying semileptonic $\textit{B}$-meson decays were shown. The performance of the Full Event Interpretation …
We report on preliminary measurements of branching fractions, charge-parity-violating asymmetries, and longitudinal polarization fractions in charmless bottom-meson decays from the Belle~II experiment. We use samples of electron-positron collisions collected in 2019 and 2020 at the $Υ(4S)$ resonance, corresponding to integrated luminosities of up to 62.8 ${\rm fb^{-1}}$. The results are compatible with known values, indicating good understanding of early detector performance.
We report the measurements of the leptonic decays B->lnu obtained at the Belle experiment. The results are consistent with the Standard Model expectations, and provide stringent constraints on new physics models including charged Higgs bosons. We also report an outlook of the measurements of B->lnu for the Belle II experiment.
High precision flavor physics measurements are an essential complement to the direct searches for new physics at the LHC. Such measurements will be performed using the upgraded Belle II detector and upgraded KEKB accelerator. The status of the Belle II detector and proposed role of the US Belle II collaborators are presented in this article.
We report measurements of the CKM angles beta/phi_1 and alpha/phi_2 done by the BABAR and Belle experiments. Both experiments have collected large data samples, corresponding to a total of more than 1 billion of BBbar pairs, at the e^+e^- asymmetric-energy colliders PEP-II (SLAC) and KEK-B (KEK), respectively.
The Belle experiment, running at the KEKB e^+ e^- asymmetric energy collider during the first decade of the century, has recorded 770 fb^-1 of data at the Upsilon(4S) resonance. A combination of recent Belle results obtained with this sample is used to perform a measurement of the CKM angle gamma. We use B^+- -> DK^+- and B^+- -> D^*K^+- decays where the D meson decays into K_S^0pi+pi-, Kpi, KK, pipi, K_S^0 pi^0 and K_S^0 eta final states and D^* decays into Dpi^0 and Dgamma. Belle obtains the most precise gamma measurement to date, gamma = (68^{+15}_{-14}) degree.
The Belle II experiment is under construction at the KEK laboratory in Japan. Belle II will study e+e- collisions at or near the Upsilon(4S) resonance with the goal of collecting 50 ab-1 of data, which is a large increase over that recorded by the Belle and BaBar experiments. This data will provide a large sample of charm meson decays. In this report we present the expected sensitivity of Belle II for measuring time-dependent mixing and CP violation in the D0-D0bar system. We focus on measurements of D0-> K+ pi-, D0-> K+ pi- pi0, and D0-> K0_S pi+ pi- decays.
We present measurements of time-dependent CP violation parameters in B0 --> K0 PI0, B0 --> Ks Pi+ Pi- and B0 --> Ks K+ K- decays. The latter two are extracted using time-dependent Dalitz plot analyses. These results are obtained from a large data sample that contains 657 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
A study of CP violation in $B\to J/ψK^*(K_S^0π^0)$ decays by time dependent angular analysis is discussed. Status of time independent analyses for other $B\to VV$ decays is also reported. The data used for the analyses are taken with the Belle detector at KEK.
We report an improved measurement of D0-D0bar mixing and a search for CP violation in D0 decays to CP-even final states K+K- and pi+pi-. The measurement is based on the final Belle data sample of 976/fb. The results are y_CP=(1.11 +- 0.22 +- 0.09)% and A_Gamma=(-0.03 +- 0.20 +- 0.07)%, where the first uncertainty is statistical and the second is systematic.
We report on new results on $B \to K^* γ$ and recent studies on $B \to K^* \ell^+ \ell^-$ and $B \to h ν\barν$ at Belle at KEKB accelerator. All the analyses used full data sample of 711~fb${}^{-1}$ taken on $Υ(4S)$ resonance.
We report the measurements of electroweak penguin processes b->d,s gamma and b->sl+l- at the Belle experiment. The analyses are based on 152 million BB-bar events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- asymmetric-energy collider. The b->d gamma transition is studied through exclusive decays: B0->rho0 gamma, B0->omega gamma and B+ ->rho+ gamma. We apply fully inclusive and semi-inclusive reconstruction to b->s gamma and b->sl+l- processes, respectively. The results on the exclusive b->d gamma and semi-inclusive b->sl+l- measurements are preliminary.
The semitauonic decay $\bar{B} \rightarrow D^* τ^- \barν_τ$ is sensitive to new physics beyond the Standard Model (SM) that has an enhanced coupling to the $τ$ lepton. In the ratio of branching fractions $R(D^*) = \mathcal{B}(\bar{B} \rightarrow D^* τ^- \barν_τ) / \mathcal{B}(\bar{B} \rightarrow D^* \ell^- \barν_\ell)$, where $\ell^- = e^-$ or $μ^-$, a 3.3$σ$ anomaly was observed. In order to investigate the anomaly further, Belle performed a new $R(D^*)$ measurement using one-prong hadronic $τ$ decays, which was statistically independent of the previous two measurements. This measurement incl…
