The dark photon A^{'} and the dark Higgs boson h^{'} are hypothetical constituents featured in a number of recently proposed dark sector models. Assuming prompt decays of both dark particles, we ...search for their production in the so-called Higgstrahlung channel e^{+}e^{-}→A^{'}h^{'}, with h^{'}→A^{'}A^{'}. We investigate ten exclusive final states with A^{'}→e^{+}e^{-}, μ^{+}μ^{-}, or π^{+}π^{-} in the mass ranges 0.1 GeV/c^{2} <m_{A^{'}}<3.5 GeV/c^{2} and 0.2 GeV/c^{2} <m_{h^{'}}<10.5 GeV/c^{2}. We also investigate three inclusive final states 2(e^{+}e^{-})X, 2(μ^{+}μ^{-})X, and (e^{+}e^{-})(μ^{+}μ^{-})X, where X denotes a dark photon candidate detected via missing mass, in the mass ranges 1.1 GeV/c^{2} <m_{A^{'}}<3.5 GeV/c^{2} and 2.2 GeV/c^{2} <m_{h^{'}}<10.5 GeV/c^{2}. Using the entire 977 fb^{-1} data set collected by Belle, we observe no significant signal. We obtain individual and combined 90% credibility level upper limits on the branching fraction times the Born cross section, B×σ_{Born}, on the Born cross section σ_{Born}, and on the dark photon coupling to the dark Higgs boson times the kinetic mixing between the standard model photon and the dark photon, α_{D}×ε^{2}. These limits improve upon and cover wider mass ranges than previous experiments. The limits from the final states 3(π^{+}π^{-}) and 2(e^{+}e^{-})X are the first placed by any experiment. For α_{D} equal to 1/137, m_{h^{'}}< 8 GeV/c^{2}, and m_{A^{'}}<1 GeV/c^{2}, we exclude values of the mixing parameter ε above ∼8×10^{-4}.
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We report the first observation of the double strange baryon Ξ(1620)0 in its decay to Ξ−π+ via Ξ+c → Ξ−π+π+ decays based on a 980 fb−1 data sample collected with the Belle detector at the KEKB ...asymmetric-energy e+e− collider. The mass and width are measured to be 1610.4 ± 6.0(stat)+6.1−4.2(syst) MeV /c2 and 59.9 ± 4.8(stat)+2.8−7.1(syst) MeV, respectively. We obtain 4.0σ evidence of the Ξ(1690)0 with the same data sample. These results shed light on the structure of hyperon resonances with strangeness S = −2
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We report on a novel application of computer vision techniques to extract beyond the Standard Model (BSM) parameters directly from high energy physics (HEP) flavor data. We develop a method of ...transforming angular and kinematic distributions into "quasi-images" that can be used to train a convolutional neural network to perform regression tasks, similar to fitting. This contrasts with the usual classification functions performed using ML/AI in HEP. As a proof-of-concept, we train a 34-layer Residual Neural Network to regress on these images and determine the Wilson Coefficient \(C_{9}\) in MC (Monte Carlo) simulations of \(B \rightarrow K^{*}\mu^{+}\mu^{-}\) decays. The technique described here can be generalized and may find applicability across various HEP experiments and elsewhere.
First measurement of the Λc+→ pη′ decay Li, S. X.; Shen, C. P.; Adachi, I. ...
The journal of high energy physics,
03/2022, Volume:
2022, Issue:
3
Journal Article
Peer reviewed
Open access
A
bstract
We present the first measurement of the branching fraction of the singly Cabibbo-suppressed (SCS) decay
Λ
c
+
→ pη
′ with
η
′
→ ηπ
+
π
−
, using a data sample corresponding to an integrated ...luminosity of 981 fb
−
1
, collected by the Belle detector at the KEKB
e
+
e
−
asymmetric-energy collider. A significant
Λ
c
+
→ pη
′ signal is observed for the first time with a signal significance of 5.4
σ
. The relative branching fraction with respect to the normalization mode
Λ
c
+
→ pK
−
π
+
is measured to be
B
Λ
c
+
→
pη
′
B
Λ
c
+
→
pK
−
π
+
=
7.54
±
1.32
±
0.73
×
10
−
3
,
where the uncertainties are statistical and systematic, respectively. Using the world-average value of
B
Λ
c
+
→
pK
−
π
+
= (6
.
28
±
0
.
32)
×
10
−
2
, we obtain
B
Λ
c
+
→
pη
′
=
4.73
±
0.82
±
0.46
±
0.24
×
10
−
4
,
where the uncertainties are statistical, systematic, and from
B
Λ
c
+
→
pK
−
π
+
, respectively.
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