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A. J. Schwartz

Publications and source records attributed to A. J. Schwartz.

At least 37 records · Page 2Linked to original sources
arXiv2018

Measurement of the branching fraction and time-dependent $CP$ asymmetry for $B^0\to J/ψπ^0$ decays

We measure the branching fraction and time-dependent $CP$-violating asymmetry for $B^0\to J/ψπ^0$ decays using a data sample of 711 ${\rm fb^{-1}}$ collected on the $Υ(4S)$ resonance by the Belle experiment running at the KEKB $e^+e^-$ collider. The branching fraction is measured to be $\mathcal{B}(B^0\to J/ψπ^0) = [1.62\,\pm 0.11~({\rm stat}) \pm0.07~({\rm syst})]\times 10^{-5}$, which is the most precise measurement to date. The measured $CP$ asymmetry parameters are $\mathcal{S} = -0.59\,\pm 0.19~({\rm stat}) \pm 0.03~({\rm syst})$ and $\mathcal{A} = -0.15\,\pm 0.14~({\rm stat})\,^{+0.04}_{-0.03}~({\rm syst})$. The mixing-induced $CP$ asymmetry ($\mathcal{S}$) differs from the case of no $CP$ violation by 3.0 standard deviations, and the direct $CP$ asymmetry ($\mathcal{A}$) is consistent with zero.

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arXiv2018

HFLAV input to the update of the European Strategy for Particle Physics

The Heavy Flavor Averaging Group provides with this document input to the European Strategy for Particle Physics. Research in heavy-flavor physics is an essential component of the particle-physics program, both within and beyond the Standard Model. To fully realize the potential of the field, we believe the strategy should include strong support for the ongoing experimental and theoretical heavy-flavor research, future upgrades of existing facilities, and significant heavy-flavor capabilities at future colliders, including dedicated experiments.

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arXiv2018

Search for the lepton-flavor-violating decay $B^{0}\to K^{\ast 0} μ^{\pm} e^{\mp}$

We have searched for the lepton-flavor-violating decay $B^{0}\to K^{\ast 0} μ^{\pm} e^{\mp}$ using a data sample of 711 $fb^{-1}$ that contains $772 \times 10^{6}$ $B\bar{B}$ pairs. The data were collected near the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. No signals were observed, and we set 90% confidence level upper limits on the branching fractions of ${\cal B}(B^{0}\to K^{\ast 0} μ^{+} e^{-})< 1.2\times 10^{-7}$, ${\cal B}(B^{0}\to K^{\ast 0} μ^{-} e^{+})< 1.6\times 10^{-7}$, and, for both decays combined, ${\cal B}(B^{0}\to K^{\ast 0} μ^{\pm} e^{\mp}) < 1.8\times 10^{-7}$. These are the most stringent limits on these decays to date.

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arXiv2018

Charm Physics: another route towards New Physics

We summarize recent results for charm physics. These results span several categories: charm mixing, indirect (time-dependent) CP violation, direct (time-integrated) CP violation, T violation, semileptonic and leptonic decays, and decays of charm baryons.

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arXiv2018

Averages of $b$-hadron, $c$-hadron, and $τ$-lepton properties as of summer 2016

This article reports world averages of measurements of $b$-hadron, $c$-hadron, and $τ$-lepton properties obtained by the Heavy Flavor Averaging Group using results available through summer 2016. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, \CP~violation parameters, parameters of semileptonic decays and CKM matrix elements.

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arXiv2017

Search for $Λ_c^+\toϕp π^0$ and branching fraction measurement of $Λ_c^+\to K^-π^+ p π^0$

We have searched for the Cabibbo-suppressed decay $Λ_c^+\toϕpπ^0$ in $e^+e^-$ collisions using a data sample corresponding to an integrated luminosity of 915 $\rm fb^{-1}$. The data were collected by the Belle experiment at the KEKB $e^+e^-$ asymmetric-energy collider running at or near the $Υ(4S)$ and $Υ(5S)$ resonances. No significant signal is observed, and we set an upper limit on the branching fraction of $\mathcal{B}(Λ_c^+\to ϕpπ^0) <15.3\times10^{-5}$ at 90% confidence level. The contribution for nonresonant $Λ_c^+\to K^+K^- pπ^0$ decays is found to be consistent with zero and the corresponding upper limit on its branching fraction is set to be $\mathcal{B}(Λ_c^+\to K^+K^-pπ^0)_{\rm NR} <6.3\times10^{-5} $ at 90% confidence level. We also measure the branching fraction for the Cabibbo-favored decay $Λ_c^+\to K^-π^+pπ^0$; the result is $\mathcal{B}(Λ_c^+\to K^-π^+pπ^0)= (4.42\pm0.05\, (\rm stat.) \pm 0.12\, (\rm syst.) \pm 0.16\, (\mathcal{B}_{\rm Norm}))\%$, which is the most precise measurement to date. Finally, we have searched for an intermediate hidden-strangeness pentaquark decay $P^+_s\toϕp$. We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of ${\cal B}(Λ_c^+\to P^+_s π^0)\times {\cal B}(P^+_s\toϕp) <8.3\times 10^{-5}$ at 90% confidence level.

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arXiv2017

Prospects for time-dependent mixing and CP-violation measurements at Belle II

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.

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arXiv2017

Charm Physics Prospects at Belle II

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, and Belle II will have a very active charm physics program. Here we discuss some highlights of this program, focusing on measurements of mixing, CP violation, and leptonic decays.

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arXiv2016

Recent results from the Belle experiment

We review recent results from the Belle experiment, which took data at the KEKB asymmetric-energy e+e- collider in Japan. The experiment recorded about 1000 fb^{-1} of data running mainly at the Υ(4S) and Υ(5S) resonances. The results presented here are obtained from the full data set.

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arXiv2016

Observation of the decay $B_s^0\rightarrow K^0\overline{K}^0$

We measure the decay $B_s^0\rightarrow K^0\overline{K}^0$ using data collected at the $Υ(5S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. The data sample used corresponds to an integrated luminosity of 121.4 ${\rm fb^{-1}}$. We measure a branching fraction $\mathcal{B}(B_s^0\rightarrow K^0\overline{K}^0) = [19.6\,^{+5.8}_{-5.1}({\rm stat.})\,\pm1.0({\rm sys.})\,\pm 2.0(N^{}_{B_s^0\overline{B}_s^0})]\times 10^{-6}$ with a significance of 5.1 standard deviations. This measurement constitutes the first observation of this decay.

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arXiv2016

Search for the decay B0 -> phi gamma

We have searched for the decay B0 -> phi gamma using the full Belle data set of 772 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- collider. No signal is observed, and we set an upper limit on the branching fraction of B(B0 -> phi gamma) < 1.0 x 10^{-7} at 90% confidence level. This is the most stringent limit on this decay mode to date.

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arXiv2015

CHARM 2015 Experimental Summary: Step-by-Step Towards New Physics

The experimental program of the Seventh International Workshop on Charm Physics (CHARM 2015) is summarized. Highlights of the workshop include results from heavy flavor production, quarkonium and exotic states, hadronic decays and Dalitz analyses, semileptonic and leptonic decays, rare and radiative decays, charm mixing, and CP and T violation.

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arXiv2015

The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C. Please note that version 3 on the archive is the auxiliary version of the Physics of the B Factories book. This uses the notation alpha, beta, gamma for the angles of the Unitarity Triangle. The nominal version uses the notation phi_1, phi_2 and phi_3. Please cite this work as Eur. Phys. J. C74 (2014) 3026.

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arXiv2015

Evidence for the decay B0->eta pi^0

We report a search for the charmless hadronic decay $B^0\toηπ^0$ with a data sample corresponding to an integrated luminosity of 694 $\rm fb^{-1}$ containing $753\times10^6$ $B\bar{B}$ pairs. The data were collected by the Belle experiment running on the $Υ(4S)$ resonance at the KEKB $e^+e^-$ collider. We measure a branching fraction $\mathcal{B}(B^0\toηπ^0)=(4.1^{+1.7+0.5}_{-1.5-0.7})\times 10^{-7}$, where the first uncertainty is statistical and the second is systematic. Our measurement gives an upper limit of $\mathcal{B}(B^0\toηπ^0)<6.5\times 10^{-7}$ at 90\% confidence level. The signal has a significance of $3.0$ standard deviations and constitutes the first evidence for this decay mode.

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arXiv2014

Averages of $b$-hadron, $c$-hadron, and $τ$-lepton properties as of summer 2014

This article reports world averages of measurements of $b$-hadron, $c$-hadron, and $τ$-lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results available through summer 2014. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, $CP$ violation parameters, parameters of semileptonic decays and CKM matrix elements.

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arXiv2013

Averages of b-hadron, c-hadron, and tau-lepton properties as of early 2012

This article reports world averages of measurements of b-hadron, c-hadron, and tau-lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results available through the end of 2011. In some cases results available in the early part of 2012 are included. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, parameters of semileptonic decays and CKM matrix elements.

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