667 research outputs found
Search for a Light C P -odd Higgs Boson and Low-Mass Dark Matter at the Belle Experiment
No full textObservation 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
Observation of e+e- → ωχbJ (1P) and Search for Xb → ω Υ (1S) at s near 10.75 GeV
No full textWe study the processes e+e-→ωχbJ(1P) (J=0, 1, or 2) using samples at center-of-mass energies s=10.701, 10.745, and 10.805 GeV, corresponding to 1.6, 9.8, and 4.7 fb-1 of integrated luminosity, respectively. These data were collected with the Belle II detector during special operations of the SuperKEKB collider above the Υ(4S) resonance. We report the first observation of ωχbJ(1P) signals at s=10.745 GeV. By combining Belle II data with Belle results at s=10.867 GeV, we find energy dependencies of the Born cross sections for e+e-→ωχb1,b2(1P) to be consistent with the shape of the Υ(10753) state. These data indicate that the internal structures of the Υ(10753) and Υ(10860) states may differ. Including data at s=10.653 GeV, we also search for the bottomonium equivalent of the X(3872) state decaying into ωΥ(1S). No significant signal is observed for masses between 10.45 and 10.65 GeV/c2
Observation of and search for at near 10.75 GeV
No full textWe study the processes ( = 0, 1, or 2) using samples at center-of-mass energies = 10.701, 10.745, and 10.805 GeV, corresponding to 1.6, 9.8, and 4.7 fb of integrated luminosity, respectively. These data were collected with the Belle II detector during a special run of the SuperKEKB collider above the resonance. We report the first observation of signals at = 10.745 GeV. By combining Belle II data with Belle results at = 10.867 GeV, we find energy dependencies of the Born cross sections for to be consistent with the shape of the state. Including data at = 10.653 GeV, we also search for the bottomonium equivalent of the state decaying into . No significant signal is observed for masses between 10.45 and 10.65 GeV/
Search for violation in decays and observation of the Cabibbo-suppressed decay
No full textWe search for violation by measuring a -odd asymmetry in the
Cabibbo-suppressed decay, and
in the Cabibbo-favored and
decays. We use 980 of data collected by the Belle detector running at the KEKB
asymmetric-energy collider. The -violating -odd parameter
is measured to be
and
where the first
uncertainty is statistical and the second is systematic. We also report the
first observation of the Cabibbo-suppressed decay . The branching fraction is measured relative to
that of the analogous Cabibbo-favored decay :
Search for the in at near 10.6 GeV at Belle
No full textInternational audienceFor the first time we search for the in at = 10.52, 10.58, and 10.867 GeV with data samples of 89.5 fb, 711 fb, and 121.4 fb, respectively, accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant signal is observed in the mass range between 3.8 and 3.88 GeV/. The upper limit at 90% confidence level on the product of the Born cross section for and branching fraction for is determined to be 4.9 fb at near 10.6 GeV
Observation of charmed strange meson pair production in decays and in annihilation at
No full textWe observe the process and continuum
production at GeV (and
their charge conjugates) using the data samples collected by the Belle detector
at KEKB, where is or . Both
states are identified through their decay into
. We measure the products of branching fractions and the Born cross sections , and then
compare the ratios for decays and
for continuum production. We obtain , , , and for the , ,
, and final states
in the modes, respectively. Therefore, the
strong decay is expected to dominate in the processes. We also measure the ratios of branching
fractions and , 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
Search for a long-lived spin-0 mediator in b →s transitions at the Belle II experiment
No full textAdditional spin-0 particles appear in many extensions of the standard model. We search for long-lived spin-0 particles S in B-meson decays mediated by a b→s quark transition in e+e- collisions at the δ(4S) resonance at the Belle II experiment. Based on a sample corresponding to an integrated luminosity of 189 fb-1, we observe no evidence for signal. We set model-independent upper limits on the product of branching fractions B(B0→K∗(892)0(→K+π-)S)×B(S→x+x-) and B(B+→K+S)×B(S→x+x-), where x+x- indicates e+e-,μ+μ-,π+π-, or K+K-, as functions of S mass and lifetime at the level of 10-7
Search for a long-lived spin-0 mediator in b→s transitions at the Belle II experiment
No full textAdditional spin-0 particles appear in many extensions of the standard model. We search for long-lived spin-0 particles S in B-meson decays mediated by a b→s quark transition in e+e− collisions at the Υ(4S) resonance at the Belle II experiment. Based on a sample corresponding to an integrated luminosity of 189 fb−1, we observe no evidence for signal. We set model-independent upper limits on the product of branching fractions B(B0→K∗(892)0(→K+π−)S)×B(S→x+x−) and B(B+→K+S)×B(S→x+x−), where x+x− indicates e+e−,μ+μ−,π+π−, or K+K−, as functions of S mass and lifetime at the level of 10−7
Measurement of the time-integrated CP asymmetry in decays using Belle and Belle II data
No full textWe measure the time-integrated CP asymmetry in decays reconstructed in events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 fb and 428 fb, respectively. The decays are required to originate from the decay, which determines the charm flavor at production time. A control sample of decays is used to correct for production and detection asymmetries. The result, , is consistent with previous determinations and with CP symmetry
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