Search for Muon Catalyzed 3Hed Fusion Fotev, V. D.; Ganzha, V. A.; Ivshin, K. A. ...
Physics of particles and nuclei,
06/2024, Letnik:
55, Številka:
3
Journal Article
Recenzirano
—This report presents the results of an experiment aimed at observation of the muon catalyzed
3
He
d
fusion reaction
3
He +
(3.66 MeV) +
p
(14.64 MeV) + μ which might occur after a negative muon stop ...in the D
2
+
3
He gas mixture. The basic element of the experimental setup is a Time Projection Chamber (TPC) which can detect the incoming muons and the products of the fusion reaction. The TPC operated with the D
2
+
3
He (5%) gas mixture at 31 K temperature. About
3
Heμ
d
molecules were produced with only 2 registered candidates for the muon catalyzed
3
He
d
fusion with the expected background
events. This gives an upper limit for the probability of the fusion decay of the
3
Heμ
d
molecule
at 90% C.L. Also presented are the measured formation rate of the
3
Heμ
d
molecule
and the probability of the fast muon transfer from the excited to the ground state of the
atom
. The obtained results are compared with the previously published data.
Abstract A search for radiative decay of B s 0 $$ {B}_s^0 $$ mesons to orbitally excited K + K − states is performed using proton proton collisions recorded by the LHCb experiment, corresponding to ...an integrated luminosity of 9 fb −1. The dikaon spectrum in the mass range m KK < 2400 MeV/c 2 is dominated by the ϕ(1020) resonance that accounts for almost 70% of the decay rate. Considering the possible contributions of f 2(1270), f 2 ′ $$ {f}_2^{\prime } $$ (1525) and f 2(2010) meson states, the overall tensor contribution to the amplitude is measured to be F f 2 = 16.8 ± 0.5 stat . ± 0.7 syst . % , $$ {\mathcal{F}}_{\left\{{f}_2\right\}}=16.8\pm 0.5\left(\textrm{stat}.\right)\pm 0.7\left(\textrm{syst}.\right)\%, $$ mostly dominated by the f 2 ′ $$ {f}_2^{\prime } $$ (1525) state. Several statistically equivalent solutions are obtained for the detailed resonant structure depending on whether the smaller amplitudes interfere destructively or constructively with the dominant amplitude. The preferred solution that corresponds to the lowest values of the fit fractions along with constructive interference leads to the relative branching ratio measurement B B s 0 → f 2 ′ γ B B s 0 → ϕγ = 19.4 − 0.8 + 0.9 stat . − 0.5 + 1.4 syst . ± 0.5 B % , $$ \frac{\mathcal{B}\left({B}_s^0\to {f}_2^{\prime}\gamma \right)}{\mathcal{B}\left({B}_s^0\to \phi \gamma \right)}={19.4}_{-0.8}^{+0.9}{\left(\textrm{stat}.\right)}_{-0.5}^{+1.4}\left(\textrm{syst}.\right)\pm 0.5\left(\mathcal{B}\right)\%, $$ where the last uncertainty is due to the ratio of measured branching fractions to the K + K − final state. This result represents the first observation of the radiative B s 0 → f 2 ′ 1525 γ $$ {B}_s^0\to {f}_2^{\prime }(1525)\gamma $$ decay, which is the second radiative transition observed in the B s 0 $$ {B}_s^0 $$ sector.
Abstract Decays of Ξ b − $$ {\Xi}_b^{-} $$ and Ω b − $$ {\Omega}_b^{-} $$ baryons to Λ c + h − h ′ − $$ {\Lambda}_c^{+}{h}^{-}{h}^{\prime -} $$ final states, with h − h ′− being π − π − , K − π − and ...K − K − meson pairs, are searched for using data collected with the LHCb detector. The data sample studied corresponds to an integrated luminosity of 8.7 fb −1 of pp collisions collected at centre-of-mass energies s $$ \sqrt{s} $$ = 7, 8 and 13 TeV. The products of the relative branching fractions and fragmentation fractions for each signal mode, relative to the B − → Λ c + p ¯ π − $$ {B}^{-}\to {\Lambda}_c^{+}\overline{p}{\pi}^{-} $$ mode, are measured, with Ξ b − → Λ c + K − π − $$ {\Xi}_b^{-}\to {\Lambda}_c^{+}{K}^{-}{\pi}^{-} $$ , Ξ b − → Λ c + K − K − $$ {\Xi}_b^{-}\to {\Lambda}_c^{+}{K}^{-}{K}^{-} $$ and Ω b − → Λ c + K − K − $$ {\varOmega}_b^{-}\to {\Lambda}_c^{+}{K}^{-}{K}^{-} $$ decays being observed at over 5 σ significance. The Ξ b − → Λ c + K − π − $$ {\Xi}_b^{-}\to {\Lambda}_c^{+}{K}^{-}{\pi}^{-} $$ mode is also used to measure the Ξ b − $$ {\Xi}_b^{-} $$ production asymmetry, which is found to be consistent with zero. In addition, the B − → Λ c + p ¯ K − $$ {B}^{-}\to {\Lambda}_c^{+}\overline{p}{K}^{-} $$ decay is observed for the first time, and its branching fraction is measured relative to that of the B − → Λ c + p ¯ π − $$ {B}^{-}\to {\Lambda}_c^{+}\overline{p}{\pi}^{-} $$ mode.
Abstract The decays of the B + meson to the final state D ∗ − D s + π + $$ {D}^{\ast -}{D}_s^{+}{\pi}^{+} $$ are studied in proton-proton collision data collected with the LHCb detector at ...centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb −1. The ratio of branching fractions of the B + → D ∗ − D s + π + $$ {B}^{+}\to {D}^{\ast -}{D}_s^{+}{\pi}^{+} $$ and B 0 → D ∗ − D s + $$ {B}^0\to {D}^{\ast -}{D}_s^{+} $$ decays is measured to be 0.173 ± 0.006 ± 0.010, where the first uncertainty is statistical and the second is systematic. Using partially reconstructed D s ∗ + → D s + γ $$ {D}_s^{\ast +}\to {D}_s^{+}\gamma $$ and D s + π 0 $$ {D}_s^{+}{\pi}^0 $$ decays, the ratio of branching fractions between the B + → D ∗ − D s ∗ + π + $$ {B}^{+}\to {D}^{\ast -}{D}_s^{\ast +}{\pi}^{+} $$ and B + → D ∗ − D s + π + $$ {B}^{+}\to {D}^{\ast -}{D}_s^{+}{\pi}^{+} $$ decays is determined as 1.31 ± 0.07 ± 0.14. An amplitude analysis of the B + → D ∗ − D s + π + $$ {B}^{+}\to {D}^{\ast -}{D}_s^{+}{\pi}^{+} $$ decay is performed for the first time, revealing dominant contributions from known excited charm resonances decaying to the D *− π + final state. No significant evidence of exotic contributions in the D s + π + $$ {D}_s^{+}{\pi}^{+} $$ or D ∗ − D s + $$ {D}^{\ast -}{D}_s^{+} $$ channels is found. The fit fraction of the scalar state T c s ¯ 0 ∗ 2900 + + $$ {T}_{c\overline{s}0}^{\ast }{(2900)}^{++} $$ observed in the B + → D − D s + π + $$ {B}^{+}\to {D}^{-}{D}_s^{+}{\pi}^{+} $$ decay is determined to be less than 2.3% at a 90% confidence level.
Abstract The Λ b 0 $$ {\Lambda}_b^0 $$ → D + D − Λ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, ...corresponding to an integrated luminosity of 5.3 fb −1. Using the B 0 → D + D − K S 0 $$ {D}^{+}{D}^{-}{K}_S^0 $$ decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be R = σ Λ b 0 σ B 0 = B Λ b 0 → D + D − Λ B B 0 → D + D − K S 0 = 0.179 ± 0.022 ± 0.014 , $$ \mathcal{R}=\frac{\sigma_{\Lambda_b^0}}{\sigma_{B^0}}=\frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)}{\mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right)}=0.179\pm 0.022\pm 0.014, $$ where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, B B 0 → D + D − K S 0 $$ \mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right) $$ , and the cross-section ratio, σ Λ b 0 / σ B 0 $$ {\sigma}_{\Lambda_b^0}/{\sigma}_{B^0} $$ , previously measured by LHCb are used to derive the branching fraction of the Λ b 0 $$ {\Lambda}_b^0 $$ → D + D − Λ decay B Λ b 0 → D + D − Λ = 1.24 ± 0.15 ± 0.10 ± 0.28 ± 0.11 × 10 − 4 , $$ \mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)=\left(1.24\pm 0.15\pm 0.10\pm 0.28\pm 0.11\right)\times {10}^{-4}, $$ where the third and fourth contributions are due to uncertainties of B B 0 → D + D − K S 0 $$ \mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right) $$ and σ Λ b 0 / σ B 0 $$ {\sigma}_{\Lambda_b^0}/{\sigma}_{B^0} $$ , respectively. Inspection of the D +Λ and D + D − invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Λ b 0 $$ {\Lambda}_b^0 $$ → D *+ D − Λ decay is also observed for the first time as a partially reconstructed component in the D + D − Λ invariant mass spectrum.
Abstract A search for the fully reconstructed B s 0 $$ {B}_s^0 $$ → μ + μ − γ decay is performed at the LHCb experiment using proton-proton collisions at s $$ \sqrt{s} $$ = 13 TeV corresponding to an ...integrated luminosity of 5.4 fb −1. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B B s 0 → μ + μ − γ < 4.2 × 10 − 8 , m μ + μ − ∈ 2 m μ 1.70 GeV / c 2 , B B s 0 → μ + μ − γ < 7.7 × 10 − 8 , m μ + μ − ∈ 1.70, 2.88 GeV / c 2 , B B s 0 → μ + μ − γ < 4.2 × 10 − 8 , m μ + μ − ∈ 3.92 m B s 0 GeV / c 2 , $$ {\displaystyle \begin{array}{cc}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left2{m}_{\mu },1.70\right\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<7.7\times {10}^{-8},&\ m\left({\mu}^{+}{\mu}^{-}\right)\in \left\textrm{1.70,2.88}\right\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left3.92,{m}_{B_s^0}\right\textrm{GeV}/{c}^2,\end{array}} $$ at 95% confidence level. Additionally, upper limits are set on the branching fraction in the 2m μ , 1.70 GeV/c 2 dimuon mass region excluding the contribution from the intermediate ϕ(1020) meson, and in the region combining all dimuon-mass intervals.
Abstract The resonant structure of the radiative decay Λ b 0 → pK − γ $$ {\Lambda}_b^0\to {pK}^{-}\gamma $$ in the region of proton-kaon invariant-mass up to 2.5 GeV/c 2 is studied using ...proton-proton collision data recorded at centre-of-mass energies of 7, 8, and 13 TeV collected with the LHCb detector, corresponding to a total integrated luminosity of 9 fb −1. Results are given in terms of fit and interference fractions between the different components contributing to this final state. Only Λ resonances decaying to pK − are found to be relevant, where the largest contributions stem from the Λ(1520), Λ(1600), Λ(1800), and Λ(1890) states.
Abstract The first search for nonresonant $${{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-} $$ B c + → π + μ + μ - decays is reported. The analysis uses proton–proton collision data collected ...with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 $$\,\text {fb} ^{-1}$$ fb - 1 . No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio $${\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} ) < 2.1\times 10^{-4}$$ B ( B c + → π + μ + μ - ) / B ( B c + → J / ψ π + ) < 2.1 × 10 - 4 at $$90\%$$ 90 % confidence level. Additionally, an updated measurement of the ratio of the $${{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+} $$ B c + → ψ ( 2 S ) π + and $${{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} $$ B c + → J / ψ π + branching fractions is reported. The ratio $${\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} )$$ B ( B c + → ψ ( 2 S ) π + ) / B ( B c + → J / ψ π + ) is measured to be $$0.254\pm 0.018 \pm 0.003 \pm 0.005$$ 0.254 ± 0.018 ± 0.003 ± 0.005 , where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ and $$\psi {(2S)}$$ ψ ( 2 S ) decays. This measurement is the most precise to date and is consistent with previous LHCb results.
Abstract Measurements of the branching fraction ratio B ϕ → μ + μ − / B ϕ → e + e − $$ \mathcal{B}\left(\phi \to {\mu}^{+}{\mu}^{-}\right)/\mathcal{B}\left(\phi \to {e}^{+}{e}^{-}\right) $$ with D s ...+ → π + ϕ $$ {D}_s^{+}\to {\pi}^{+}\phi $$ and D + → π + ϕ decays, denoted R ϕπ s $$ {R}_{\phi \pi}^s $$ and R ϕπ d $$ {R}_{\phi \pi}^d $$ , are presented. The analysis is performed using a dataset corresponding to an integrated luminosity of 5.4 fb −1 of pp collision data collected with the LHCb experiment. The branching fractions are normalised with respect to the B + → K + J/ψ(→ e + e − ) and B + → K + J/ψ(→ μ + μ − ) decay modes. The combination of the results yields R ϕπ = 1.022 ± 0.012 stat ± 0.048 syst . $$ {R}_{\phi \pi}=1.022\pm 0.012\left(\textrm{stat}\right)\pm 0.048\left(\textrm{syst}\right). $$ The result is compatible with previous measurements of the ϕ → ℓ + ℓ − branching fractions and predictions based on the Standard Model.
