91 research outputs found
Study of the process in the energy range \sqrt{s} = \mbox{1.05-2.00} GeV with the SND detector
The process is studied in the center-of-mass
energy range 1.05-2.00 GeV using data with an integrated luminosity of 94.5
pb collected by the SND detector at the VEPP-2000 collider. The
cross section is measured for the first time. It is
shown that the dominant mechanism of this reaction is the transition through
the intermediate state. The measured cross section of the
subprocess is consistent with previous
measurements in the mode. It is found, with a
significance of 5.6, that the process is not
completely described by hadronic vector-pseudoscalar intermediate states. The
cross section of this missing contribution, which can originate from radiation
processes, e. g. , is measured. It is found to be
15-20 pb in the wide energy range from 1.3 to 1.9 GeV.Comment: 10 pages, 6 figures, to be submitted to European Physical Journal
Study of dynamics of the process in the energy range 1.15--2.00 GeV
The dynamics of the process is studied in the
energy region from 1.15 to 2.00 GeV using data accumulated with the SND
detector at the VEPP-2000 collider. The Dalitz plot distribution and
mass spectrum are analyzed in a model including the intermediate
states , , and . As a result, the
energy dependences of the and cross sections and
the relative phases between the amplitude and the and amplitudes are obtained. The cross section
has a peak in the energy region of the resonance (1.55-1.75
GeV). In this energy range the contributions of the and
states are of the same order of magnitude. No resonance
structure near 1.65 GeV is observed in the cross section. We
conclude that the intermediate state gives a significant
contribution to the decay of , whereas the
mechanism dominates in the decay
.Comment: 9 pages, 7 figures, 3 table
Study of e⁺e⁻ → Υ(1S, 2S)η and e⁺e⁻ → Υ(1S)η′ at √s = 10.866 GeV with the Belle detector
We report the first observation of the processes e+e−→Υ(1S,2S)η at √s=10.866 GeV, with significance exceeding 10σ for both processes. The measured Born cross sections are σ(e+e−→Υ(2S)η)=2.07±0.21±0.19 pb, and σ(e+e−→Υ(1S)η)=0.42±0.08±0.04 pb. We also set the upper limit on the cross section of the process e+e−→Υ(1S)η′ to be σ(e+e−→Υ(1S)η′)<0.037 pb at 90% C.L. The results are obtained with the data sample collected with the Belle detector at the KEKB asymmetric-energy e+e− collider in the energy range from 10.63 to 11.02 GeV
First measurement of the Michel parameter in the decay at Belle
We report the first measurement of the Michel parameter in the
decay with a new method proposed just
recently. The measurement is based on the reconstruction of the
events with subsequent muon
decay-in-flight in the Belle central drift chamber. The analyzed data sample of
collected by the Belle detector corresponds to
approximately pairs. We measure
, which is in
agreement with the Standard Model prediction of . Statistical
uncertainty dominates in this study, being a limiting factor, while systematic
uncertainty is well under control. Our analysis proved the practicability of
this promising method and its prospects for further precise measurement in
future experiments.Comment: 6 pages, 4 figures, submitted to Phys. Rev. Let
Measurement of Differential Distributions of and Implications on
We present a measurement of the differential shapes of exclusive ( and ) decays with
hadronic tag-side reconstruction for the full Belle data set of
integrated luminosity. We extract the
Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) form factor
parameters and use an external input for the absolute branching fractions to
determine the Cabibbo-Kobayashi-Maskawa matrix element and find
and with the zero-recoil lattice QCD point
. We also perform a study of the impact of
preliminary beyond zero-recoil lattice QCD calculations on the
determinations. Additionally, we present the lepton flavor universality ratio
, the electron and muon
forward-backward asymmetry and their difference , and the electron and muon longitudinal polarization fraction and
their difference . The
uncertainties quoted correspond to the statistical and systematic
uncertainties, respectively
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
Combined analysis of Belle and Belle II data to determine the CKM angle ϕ3 using B+ → D(K0S h+h−)h+ decays
Measurements of branching fraction and direct CP asymmetry in B → KKK and a search for B → KKπ
Erratum to: Combined analysis of Belle and Belle II data to determine the CKM angle ϕ3 using B+ → D(K0Sh+h−)h+ decays
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