Evidence for Direct CP Violation in B±→ηh±B^\pm \to \eta h^\pm and Observation of B0→ηK0B^0 \to \eta K^0

We report measurements of the branching fractions and CP asymmetries for B^+- -> eta h^+- (h = K or pi) and the observation of the decay B^0 -> eta K^0 from the final data sample of 772x10^6 BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. The measured branching fractions are Br(B^+- -> eta K^+-) = (2.12 +- 0.23 +- 0.11)x10^-6}, Br(B^+- -> eta pi^+-) = (4.07 +- 0.26 +- 0.21)x10^{-6} and Br(B^0 -> eta K^0) = (1.27^{+0.33}_{-0.29} +- 0.08)x10^-6, where the last decay is observed for the first time with a significance of 5.4 standard deviations (\sigma). We also find evidence for CP violation in the charged B modes, A_{CP}(B^+- -> eta K^+-) = -0.38 +- 0.11 +- 0.01 and A_{CP}(B^+- -> eta pi^+- = -0.19 +- 0.06 +- 0.01 with significances of 3.8 sigma and 3.0 sigma, respectively. For all measurements, the first and second uncertainties are statistical and systematic, respectively.Comment: 6 pages, 3 figures, 1 tabl

Study of the decays B->D_s1(2536)+ anti-D(*)

We report a study of the decays B -> D_s1(2536)+ anti-D(*), where anti-D(*) is anti-D0, D- or D*-, using a sample of 657 x 10^6 B anti-B pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The branching fractions of the decays B+ -> D_s1(2536)+ anti-D0, B0 -> D_s1(2536)+ D- and B0 -> D_s1(2536)+ D*- multiplied by that of D_s1(2536)+ -> (D*0K+ + D*+K0) are found to be (3.97+-0.85+-0.56) x 10^-4, (2.75+-0.62+-0.36) x 10^-4 and (5.01+-1.21+-0.70) x 10^-4, respectively.Comment: 6 pages, 2 figues, submitted to PRD (RC

Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma

Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma is measured using 232 fb-1 of data collected with the BABAR detector at center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial and final state radiation. The asymmetry is determined as afunction of the invariant mass of the final-state tracks from production threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e- --> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order FSR production is consistent with the QED expectation for e+ e- --> mu+ mu- gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.

Observation of an Excited Bc+ State

Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date

Belle II Technical Design Report

The Belle detector at the KEKB electron-positron collider has collected almost 1 billion Y(4S) events in its decade of operation. Super-KEKB, an upgrade of KEKB is under construction, to increase the luminosity by two orders of magnitude during a three-year shutdown, with an ultimate goal of 8E35 /cm^2 /s luminosity. To exploit the increased luminosity, an upgrade of the Belle detector has been proposed. A new international collaboration Belle-II, is being formed. The Technical Design Report presents physics motivation, basic methods of the accelerator upgrade, as well as key improvements of the detector.Comment: Edited by: Z. Dole\v{z}al and S. Un

Search for B_{s}^{0}->hh Decays at the Υ(5S)\Upsilon(5S) Resonance

We have searched for B_{s}^{0}->hh decays, where h stands for a charged or neutral kaon, or a charged pion. These results are based on a 23.6 fb^{-1} data sample collected with the Belle detector on the \Upsilon(5S) resonance at the KEKB asymmetric-energy e^{+}e^{-} collider, containing 1.25x10^6 B_{s}^{(*)}\bar{B}_{s}^{(*)} events. We observe the decay B_{s}^{0}->K^{+}K^{-} and measure its branching fraction, \mathcal{B}(B_{s}^{0}->K^{+}K^{-}) = [3.8_{-0.9}^{+1.0}(\mathrm{stat})\pm 0.5(\mathrm{syst})\pm 0.5(f_s)] \times 10^{-5}. The first error is statistical, the second is systematic, and the third error is due to the uncertainty in the B^0_s production fraction in $e^+e^-\to b\bar{b}$ events. No significant signals are seen in other decay modes, and we set upper limits at 90% confidence level: \mathcal{B}(B_{s}^{0}->K^-\pi^{+})< 2.6 \times 10^{-5}, \mathcal{B}(B_{s}^{0}->\pi^{+}\pi^{-})< 1.2 \times 10^{-5} and \mathcal{B}(B_{s}^{0}->K^0\bar{K}^0) < 6.6\times 10^{-5}.Comment: 6 pages, 2 figure, two table

Measurement of branching fractions for B J / K decays and search for a narrow resonance in the J / final state

We report an observation of the and decays using pairs collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider. We obtain the branching fractions and . We search for a new narrow charmonium(-like) state in the mass spectrum and find no significant excess. We set upper limits on the product of branching fractions, , at where a -odd partner of may exist, at and assuming their known mass and width, and over a range from 3.8 to . The obtained upper limits at 90 confidence level for , , and are , , and , respectivel

Measurement of Branching Fractions and CP Asymmetries in B -> wK Decays and First Evidence of CP Violation in B0 -> wKS0

We present a measurement of the branching fractions and charge-parity-(CP-) violating parameters in B -> omega K decays. The results are obtained from the final data sample containing 772 x 10^(6) BBbar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We obtain the branching fractions B(B0 -> omega K0) = (4.5 +/- 0.4 (stat) +/- 0.3 (syst)) x 10^(-6), B(B- -> omega K-) = (6.8 +/- 0.4 (stat) +/- 0.4 (syst)) x 10^(-6), which are in agreement with their respective current world averages. For the CP violating parameters, we obtain A(B0 -> omega KS) = -0.36 +/- 0.19 (stat) +/- 0.05 (syst), S(B0 -> omega KS) = +0.91 +/- 0.32 (stat) +/- 0.05 (syst), A(B- -> omega K-) = -0.03 +/- 0.04 (stat) +/- 0.01 syst), where A and S represent the direct and mixing-induced CP asymmetry, respectively. We find no evidence of CP violation in the decay channel B-->omega K-; however, we obtain the first evidence of CP violation in the B0 -> omega KS decay channel at the level of 3.1 standard deviations.Comment: 25 pages, 5 figures, Submitted to PR

Search for Lepton-number-violating B+->D-l+l'+ Decays

We perform the first search for lepton-number-violating B+->D-l+l'+ decays, where l and l' stand for e or mu, using 772 x 10^6 BB-bar pairs accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB e^+e^- collider. No evidence for these decays has been found. Assuming uniform three-body phase space distributions for the D-l+l+ decays, we set the following upper limits on the branching fractions at 90% confidence level: Br(B+ -> D-e+e+) < 2.6x10^-6, Br(B+ -> D-e+mu+) D-mu+mu+) < 1.0x10^-6.Comment: 7 pages, 2 figure