188 research outputs found
Search for baryon and lepton number violating decays D →pl
No full textWe search for the baryon and lepton number violating charm decays, D→pl, where D is either a D0 or a D ̄0 and l is a muon or an electron, using a data sample of 921 fb-1 collected by the Belle detector at the KEKB asymmetric energy e+e- collider. In the absence of significant signals, we set upper limits on the branching fractions in the range (5-8)×10-7 at a 90% confidence level, depending on the decay mode
Measurements of the branching fractions B (B ̄0 → D∗+ π-) and B(B ̄0 →D∗+ K-) and tests of QCD factorization
No full textUsing (771.6±10.6)×106 BB ̄ meson pairs recorded by the Belle experiment at the KEKB e+e- collider, we report the branching fractions B(B ̄0→D∗+π-)=(2.62±0.02±0.09)×10-3 and B(B ̄0→D∗+K-)=(2.22±0.06±0.08)×10-4; the quoted uncertainties are statistical and systematic, respectively. A measurement of the ratio of these branching fractions is also presented, RK/π=B(B ̄→D∗+K-)/B(B ̄→D∗+π-)=(8.41±0.24±0.13)×10-2, where systematic uncertainties due to the D∗+ meson reconstruction cancel out. Furthermore, we report a new QCD factorization test based on the measured ratios for B ̄→D∗+h- and B ̄→D∗+l-ν decays at squared momentum transfer values equivalent to the mass of the h=π or K hadron. The parameters |a1(h)| are measured to be |a1(π)|=0.884±0.004±0.003±0.016 and |a1(K)|=0.913±0.019±0.008±0.013, where the last uncertainties account for all external inputs. These values are approximately 15% lower than those expected from theoretical predictions. Subsequently, flavor SU(3) symmetry is tested by measuring the ratios for pions and kaons, |a1(K)|2/|a1(π)|2=1.066±0.042±0.018±0.023, as well as for different particle species. The ratio is consistent with unity and therefore no evidence for SU(3) symmetry breaking effects is found at the 5% precision level
Search for baryon and lepton number violating decays
No full text6 pages, 4 figures, To be submitted in PRD(L)International audienceWe search for the baryon and lepton number violating charm decays, , where is either a or a and is a muon or an electron, using a data sample of collected by the Belle detector at the KEKB asymmetric energy collider. In the absence of significant signals, we set upper limits on the branching fractions in the range at a 90\% confidence level, depending on the decay mode
Test of lepton flavor universality with a measurement of R (D∗) using hadronic B tagging at the Belle II experiment
No full textThe ratio of branching fractions R(D∗)=B(B→D∗τ-ντ)/B(B→D∗-ν), where is an electron or muon, is measured using a Belle II data sample with an integrated luminosity of 189 fb-1 at the SuperKEKB asymmetric-energy e+e-collider. Data is collected at the I(4S) resonance, and one B meson in the I(4S)→BB decay is fully reconstructed in hadronic decay modes. The accompanying signal B meson is reconstructed as B→D∗τ-ντ using leptonic τ decays. The normalization decay, B→D∗-ν, produces the same observable final-state particles. The ratio of branching fractions is extracted in a simultaneous fit to two signal-discriminating variables in both channels and yields R(D∗)=0.262-0.039+0.041(stat)-0.032+0.035(syst). This result is consistent with the current world average and with Standard Model predictions
Measurements of the branching fractions and and tests of QCD factorization
No full text13 pages, 6 figuresInternational audienceUsing meson pairs recorded by the Belle experiment at the KEKB collider, we report the branching fractions and ; the quoted uncertainties are statistical and systematic, respectively. A measurement of the ratio of these branching fractions is also presented, , where systematic uncertainties due to the meson reconstruction cancel out. Furthermore, we report a new QCD factorization test based on the measured ratios for and decays at squared momentum transfer values equivalent to the mass of the or hadron. The parameters are measured to be and , where the last uncertainties account for all external inputs. These values are approximately lower than those expected from theoretical predictions. Subsequently, flavor symmetry is tested by measuring the ratios for pions and kaons, , as well as for different particle species. The ratio is consistent with unity and therefore no evidence for symmetry breaking effects is found at the precision level
XRD and FTIR analysis heat treated lithium bismo-borate glasses doped with 1.0 mol% copper ferrite
No full text
Observation of charmed strange meson pair production in Y(2S) decays and in e+e− annihilation at sqrt(s)=10.52 GeV
No full textWe observe the process Y(2S)→D(*)+s D−sJ and continuum production e+e-→D(*)+s D-sJ at sqrt(s)=10.52 GeV (and their charge conjugates) using the data samples collected by the Belle detector at KEKB, where D-sJ is Ds1(2536)− or D*s2(2573)−. Both D-sJ states are identified through their decay into KD(*). We measure the products of branching fractions B(Y(2S)→D(*)+s D−sJ)B(D-sJ→KD(*)) and the Born cross sections σBorn(e+e-→D(*)+s D-sJ)B(D-sJ→KD(*)), and then compare the ratios R1=B(Y(2S)→D(*)+s D−sJ)/B(Y(2S)→μ+μ−) for Y(2S) decays and R1=σBorn(e+e-→D(*)+s D-sJ)/σBorn(e+e-→μ+μ−) for continuum production. We obtain R1/R2=9.7±2.3±1.1, 6.8±2.1±0.8, 10.2±3.3±2.5, and 3.4±2.1±0.8 for the D+s Ds1(2536)−, D*+s Ds1(2536)−, D+s D*s2(2573)−, and D*+s D*s2(2573)− final states in the D-sJ→K−D(*)0 modes, respectively. The measured R1/R2 values indicate that the strong decay dominates in Y(2S)→D(*)+s D−sJ processes. We also measure the ratios of branching fractions B(Ds1(2536)−→K0SD*(2010)−)/B(Ds1(2536)−→K-D*(2007)0)=0.48±0.07±0.02 and B(D*s2(2573)−→K0SD-)/B(D*s2(2573)−→K-D0)=0.49±0.10±0.02, which are consistent with isospin symmetry. The second ratio is the first measurement of this quantity. Here, the first uncertainties are statistical and the second are systematic
Measurement of the branching fractions of → D(*)K− and → D(*) decays at Belle II
No full textWe present measurements of the branching fractions of eight B0 → D(∗)+K-K(∗)0(S), B- → D(∗)0 K− K(*)0(S) decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Y(4S) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362 fb^−1 . The event yields are extracted from fits to the distributions of the difference between expected and observed B meson energy, and are efficiency-corrected as a function of m(K− K(*)0(S) ) and m(D(∗) K(*)0(S) ) in order to avoid dependence on the decay model. These results include the first observation of B0 → D+ K− K0S , B− → D∗0 K−K0S, and B0 → D∗+ K− K0S decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of the K − K(*)0(S) systems are compatible with quasi-two-body decays via a resonant transition with spin-parity JP = 1− for the K − K0S systems and JP = 1+ for the K− K∗0 systems. We also present measurements of the branching fractions of four B0 → D(∗)+ D-s , B− → D(∗)0 D-s decay channels with a
precision compatible to the current world averages
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