To meet the high radiation challenge for detectors in future high-energy physics, a novel 3D 4H-SiC detector was investigated. Three-dimensional 4H-SiC detectors could potentially operate in a harsh radiation and room-temperature environment because of its high thermal conductivity and high atomic displacement threshold energy. Its 3D structure, which decouples the thickness and the distance between electrodes, further improves the timing performance and the radiation hardness of the detector. We developed a simulation software—RASER (RAdiation SEmiconductoR)—to simulate the time resolution of planar and 3D 4H-SiC detectors with different parameters and structures, and the reliability of the software was verified by comparing the simulated and measured time-resolution results of the same detector. The rough time resolution of the 3D 4H-SiC detector was estimated, and the simulation parameters could be used as guideline to 3D 4H-SiC detector design and optimization.
The B+ → Jψη′K+ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb−1. The branching fraction of this decay is measured relative to the known branching fraction of the B+ → ψ(2S)K+ decay and found to be$$ \frac{\mathcal{B}\left({B}^{+}\to {J\psi \eta}^{\prime }{K}^{+}\right)}{\mathcal{B}\left({B}^{+}\to \psi (2S){K}^{+}\right)}=\left(4.91\pm 0.47\pm 0.29\pm 0.07\right)\times {10}^{-2}, $$ B B + → Jψη ′ K + B B + → ψ 2 S K + = 4.91 ± 0.47 ± 0.29 ± 0.07 × 10 − 2 , where the first uncertainty is statistical, the second is systematic and the third is related to external branching fractions. A first look at the J/ψη′ mass distribution is performed and no signal of intermediate resonances is observed.
The very rare $${{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} $$ D ∗ ( 2007 ) 0 → μ + μ - decay is searched for by analysing $${{{B} ^-}} \!\rightarrow {{\pi } ^-} {\mu ^+\mu ^-} $$ B - → π - μ + μ - decays. The analysis uses a sample of beauty mesons produced in proton–proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9$$\text {\,fb} ^{-1}$$ \,fb - 1 . The signal signature corresponds to simultaneous peaks in the $${\mu ^+\mu ^-} $$ μ + μ - and $${{\pi } ^-} {\mu ^+\mu ^-} $$ π - μ + μ - invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at $$\mathcal{B}({{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} ) < 2.6\times 10^{-8}$$ B ( D ∗ ( 2007 ) 0 → μ + μ - ) < 2.6 × 10 - 8 at $$90\%$$ 90 % confidence level. This is the first limit on the branching fraction of $${{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} $$ D ∗ ( 2007 ) 0 → μ + μ - decays and the most stringent limit on $${{D} ^*} (2007)^0$$ D ∗ ( 2007 ) 0 decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.
The polarimeter vector field for multibody decays of a spin-half baryon is introduced as a generalisation of the baryon asymmetry parameters. Using a recent amplitude analysis of the $$ {\Lambda}_c^{+} $$ Λ c + → pK−π+ decay performed at the LHCb experiment, we compute the distribution of the kinematic-dependent polarimeter vector for this process in the space of Mandelstam variables to express the polarised decay rate in a model-agnostic form. The obtained representation can facilitate polarisation measurements of the $$ {\Lambda}_c^{+} $$ Λ c + baryon and eases inclusion of the $$ {\Lambda}_c^{+} $$ Λ c + → pK−π+ decay mode in hadronic amplitude analyses.
The first observation of the $$ {B}_s^0 $$ B s 0 → (χc1(3872) → J/ψπ+π−)π+π− decay is reported using proton-proton collision data, corresponding to integrated luminosities of 1, 2 and 6 fb−1, collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ratio of branching fractions relative to the $$ {B}_s^0 $$ B s 0 → (ψ(2S) → J/ψπ+π−)π+π− decay is measured to be$$ \frac{\mathcal{B}\left({B}_s^0\to {\chi}_{c1}(3872){\pi}^{+}{\pi}^{-}\right)\times \mathcal{B}\left({\chi}_{c1}(3872)\to J/\psi {\pi}^{+}{\pi}^{-}\right)}{\mathcal{B}\left({B}_s^0\to \psi (2S){\pi}^{+}{\pi}^{-}\right)\times \mathcal{B}\left(\psi (2S)\to J/\psi {\pi}^{+}{\pi}^{-}\right)}=\left(6.8\pm 1.1\pm 0.2\right)\times {10}^{-2}, $$ B B s 0 → χ c 1 3872 π + π − × B χ c 1 3872 → J / ψ π + π − B B s 0 → ψ 2 S π + π − × B ψ 2 S → J / ψ π + π − = 6.8 ± 1.1 ± 0.2 × 10 − 2 , where the first uncertainty is statistical and the second systematic. The mass spectrum of the π+π− system recoiling against the χc1(3872) meson exhibits a large contribution from $$ {B}_s^0 $$ B s 0 → χc1(3872) (f0(980) → π+π−) decays.
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