142 research outputs found
Search for decays to invisible final states at Belle
We report a search for decays into invisible final states using a
data sample of pairs collected at the
resonance with the Belle detector at the KEKB
collider. The signal is identified by fully reconstructing a hadronic decay of
the accompanying meson and requiring no other particles in the event. No
significant signal is observed, and we obtain an upper limit of at the 90% confidence level for the branching fraction of invisible
decay.Comment: 6 pages, 5 figures (9 figure files
Angular analysis of
We present a measurement of angular observables, , , ,
, in the decay , where
is either or . The analysis is performed on
a data sample corresponding to an integrated luminosity of
containing pairs, collected
at the resonance with the Belle detector at the
asymmetric-energy collider KEKB. Four angular observables,
are extracted in five bins of the invariant mass squared of the
lepton system, . We compare our results for with Standard
Model predictions including the region in which the LHCb collaboration
reported the so-called anomaly.Comment: Conference paper for LHC Ski 2016. SM prediction for
corrected and reference for arXiv:1207.2753 adde
Search for B -> phi pi decays
We report on a search for the charmless decays and
that are strongly suppressed in the Standard Model. The
analysis is based on a data sample of pairs
collected at the resonance with the Belle detector at the KEKB
asymmetric-energy collider. We find no significant signal and set
upper limits of for and for at the 90% confidence level.Comment: submitted to Phys. Rev. D (RC
Belle II Vertex Detector Performance
The Belle II experiment at the SuperKEKB accelerator (KEK, Tsukuba, Japan) collected its first e+e− collision data in the spring 2019. The aim of accumulating a 50 times larger data sample than Belle at KEKB, a first generation B-Factory, presents substantial challenges to both the collider and the detector, requiring not only state-of-the-art hardware, but also modern software algorithms for tracking and alignment.
The broad physics program requires excellent performance of the vertex detector, which is composed of two layers of DEPFET pixels and four layers of double sided-strip sensors. In this contribution, an overview of the vertex detector of Belle II and our methods to ensure its optimal performance, are described, and the first results and experiences from the first physics run are presented
Measurements of the branching fractions for decays at Belle II
This paper reports a study of decays using
fb of data collected during 2019--2020 by the Belle II experiment at the
SuperKEKB asymmetric-energy collider, corresponding to events. We find , ,
, and signal events in the decay modes , ,
, and , respectively. The uncertainties quoted for the
signal yield are statistical only. We report the branching fractions of these
decays: where the first
uncertainty is statistical, and the second is systematic. The results are
consistent with world-average values
- …