A study of CP violation in the decays B±→[K+K-π+π-]Dh± (h= K, π) and B±→[π+π-π+π-]Dh±

The first study of CP violation in the decay mode B±→[K+K-π+π-]Dh± , with h= K, π , is presented, exploiting a data sample of proton–proton collisions collected by the LHCb experiment that corresponds to an integrated luminosity of 9 \,fb - 1 . The analysis is performed in bins of phase space, which are optimised for sensitivity to local CP asymmetries. CP -violating observables that are sensitive to the angle γ of the Unitarity Triangle are determined. The analysis requires external information on charm-decay parameters, which are currently taken from an amplitude analysis of LHCb data, but can be updated in the future when direct measurements become available. Measurements are also performed of phase-space integrated observables for B±→[K+K-π+π-]Dh± and B±→[π+π-π+π-]Dh± decays

Measurement of antiproton production from antihyperon decays in pHe collisions at √sNN=110GeV

The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and 110GeV\!/c . The dominant antihyperon contribution, namely Λ¯ → p¯ π+ decays from promptly produced Λ¯ particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models

Measurement of τL using the Bs0 →J/ψη decay mode

Using a proton–proton collision data sample collected by the LHCb detector and corresponding to an integrated luminosity of 5.7fb-1 , the lifetime of the light Bs0 mass eigenstate, τL , is measured using the Bs0→J/ψη decay mode to be τL=1.445±0.016(stat)±0.008(syst)ps. A combination of this result with a previous LHCb analysis using an independent dataset corresponding to 3 fb - 1 of integrated luminosity gives τL=1.452±0.014±0.007±0.002ps, where the first uncertainty is statistical, the second due to the uncorrelated part of the systematic uncertainty and the third due to the correlated part of the systematic uncertainty

First observation of the B+→Ds+Ds−K+B^+ \rightarrow D_s^+ D_s^- K^+ decay

The $B^+ \rightarrow D_s^+ D_s^- K^+$ decay is observed for the first time using proton-proton collision data collected by the LHCb detector at centre-of-mass energies of $7$, $8$ and $13\, \text{TeV}$, corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$. Its branching fraction relative to that of the $B^{+} \rightarrow D^{+} D^{-} K^{+}$ decay is measured to be $$\frac{B\left(B^{+} \rightarrow D_s^{+} D_s^{-} K^{+}\right)}{B\left(B^{+} \rightarrow D^{+} D^{-} K^{+}\right)}=0.525 \pm 0.033 \pm 0.027 \pm 0.034,$$ where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the $D_s^{\pm} \rightarrow K^{\mp} K^{\pm} \pi^{\pm}$ and $D^{\pm} \rightarrow K^{\mp} \pi^{\pm} \pi^{\pm}$ decays. This measurement fills an experimental gap in the knowledge of the family of Cabibbo$-$favoured $\bar{b} \rightarrow \bar{c} c \bar{s}$ transitions and opens the path for unique studies of spectroscopy in future.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-019.html (LHCb public pages

Charmonium production in pNe collisions at √sNN=68.5 GeV

The measurement of charmonium states produced in proton-neon (pNe) collisions by the LHCb experiment in its fixed-target configuration is presented. The production of J/ψ and ψ(2 S) mesons is studied with a beam of 2.5 TeV protons colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy sNN=68.5GeV . The data sample corresponds to an integrated luminosity of 21.7 ± 1.4 nb - 1 . The J/ψ and ψ(2 S) hadrons are reconstructed in μ+μ- final states. The J/ψ production cross-section per target nucleon in the centre-of-mass rapidity range y⋆∈ [- 2.29 , 0] is found to be 506±8±46nb/nucleon . The ratio of J/ψ and D cross-sections is evaluated to (1.06 ± 0.02 ± 0.09) % . The ψ(2 S) to J/ψ relative production rate is found to be (1.67 ± 0.27 ± 0.10) % in good agreement with other measurements involving beam and target nuclei of similar sizes

Study of charmonium decays to KS0KπK^0_S K \pi in the B→(KS0Kπ)KB \to (K^0_S K \pi) K channels

A study of the $B^+\to K^0_SK^+K^-\pi^+$ and $B^+\to K^0_SK^+K^+\pi^-$ decays is performed using proton-proton collisions at center-of-mass energies of 7, 8 and 13 TeV at the LHCb experiment. The $K^0_SK \pi$ invariant mass spectra from both decay modes reveal a rich content of charmonium resonances. New precise measurements of the $\eta_c$ and $\eta_c(2S)$ resonance parameters are performed and branching fraction measurements are obtained for $B^+$ decays to $\eta_c$, $J/\psi$, $\eta_c(2S)$ and $\chi_{c1}$ resonances. In particular, the first observation and branching fraction measurement of $B^+ \to \chi_{c0} K^0 \pi^+$ is reported as well as first measurements of the $B^+\to K^0K^+K^-\pi^+$ and $B^+\to K^0K^+K^+\pi^-$ branching fractions. Dalitz plot analyses of $\eta_c \to K^0_SK\pi$ and $\eta_c(2S) \to K^0_SK\pi$ decays are performed. A new measurement of the amplitude and phase of the $K \pi$ $S$-wave as functions of the $K \pi$ mass is performed, together with measurements of the $K^*_0(1430)$, $K^*_0(1950)$ and $a_0(1700)$ parameters. Finally, the branching fractions of $\chi_{c1}$ decays to $K^*$ resonances are also measured.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-051.html (LHCb public pages

Search for D∗(2007)0→μ+μ−D^{*}(2007)^0\to\mu^+\mu^- in B−→π−μ+μ−B^-\to\pi^-\mu^+\mu^- decays

The very rare $D^{*}(2007)^0\to\mu^+\mu^-$ decay is searched for by analysing $B^-\to\pi^-\mu^+\mu^-$ 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 fb$^{-1}$. The signal signature corresponds to simultaneous peaks in the $\mu^+\mu^-$ and $\pi^-\mu^+\mu^-$ 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 ${\cal B}(D^{*}(2007)^0\to\mu^+\mu^-) < 2.6\times 10^{-8}$ at $90\%$ confidence level. This is the first limit on the branching fraction of $D^{*}(2007)^0\to\mu^+\mu^-$ decays and the most stringent limit on $D^{*}(2007)^0$ decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-004.html (LHCb public pages

Measurement of the CKM angle γ\gamma in the B0→DK∗0B^0 \to DK^{*0} channel using self-conjugate D→KS0h+h−D \to K_S^0 h^+ h^- decays

A model-independent study of CP violation in $B^0 \to DK^{*0}$ decays is presented using data corresponding to an integrated luminosity of 9fb$^{-1}$ collected by the LHCb experiment at centre-of-mass energies of $\sqrt{s}=7, \, 8$ and $13$TeV. The CKM angle $\gamma$ is determined by examining the distributions of signal decays in phase-space bins of the self-conjugate $D \to K_S^0 h^+ h^-$ decays, where $h = \pi, K$. Observables related to CP violation are measured and the angle $\gamma$ is determined to be $\gamma=(49^{+ 23}_{-18})^\circ$. Measurements of the amplitude ratio and strong-phase difference between the favoured and suppressed $B^0$ decays are also presented.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-009.html (LHCb public pages

Search for CPCP violation in the phase space of D0→π−π+π0D^0 \to \pi^-\pi^+\pi^0 decays with the energy test

A search for $CP$ violation in $D^0 \to \pi^-\pi^+\pi^0$ decays is reported, using $pp$ collision data collected by the LHCb experiment from 2015 to 2018 corresponding to an integrated luminosity of 6$fb^{-1}$. An unbinned model-independent approach provides sensitivity to local $CP$ violation within the two-dimensional phase space of the decay. The method is validated using the Cabibbo-favoured channel \D^0 \to \K^-\pi^+\pi^0 and background regions of the signal mode. The results are consistent with $CP$ symmetry in this decay.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-005.html (LHCb public pages

Observation of the Bs0 ⁣→D∗+D∗−B^0_s\!\to D^{*+}D^{*-} decay

The first observation of the $B^0_s\!\to D^{*+}D^{*-}$ decay and the measurement of its branching ratio relative to the $B^0\!\to D^{*+}D^{*-}$ decay are presented. The data sample used corresponds to an integrated luminosity of 9$\,\text{fb}^{-1}$ of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13$\,\text{TeV}$ between 2011 and 2018. The decay is observed with a very high significance and the ratio of branching fractions is determined to be \begin{align*} \frac{\mathcal{B}(B^0_s\!\to D^{*+}D^{*-})}{\mathcal{B}(B^0\!\to D^{*+}D^{*-})} = 0.269 \pm 0.032 \pm 0.011 \pm 0.008\, , \end{align*} where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio $f_s/f_d$. The $B^0_s\!\to D^{*+}D^{*-}$ branching fraction is calculated to be \begin{align*} \mathcal{B}(B^0_s\!\to D^{*+}D^{*-}) = (2.15 \pm 0.26 \pm 0.09 \pm 0.06 \pm 0.16)\times 10^{-4} \,, \end{align*} where the fourth uncertainty is due to the $B^0\!\to D^{*+}D^{*-}$ branching fraction.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-023.html (LHCb public pages