GPU-based optical photon simulation for the LHCb RICH 1 Detector

We present the investigation of the use of Opticks, a GPU-accelerated optical photon interface with the LHCb detector simulation, to improve computation time of optical photon propagation. The hybrid workflow, combining the particle simulation package Geant4 and Opticks, offloads optical photon propagation to GPUs, thereby accelerating the overall simulation process. The consistency of the results obtained from Geant4 and Opticks simulations is verified with a simplified LHCb RICH 1 detector geometry, demonstrating the feasibility of the proposed approach. In addition, the ongoing transition to the NVIDIA OptiX 7 API and re-structuring of Opticks code is discussed within the context of HEP simulation workflows, with caveats explored

Gpu-based optical photon simulation for the LHCb RICH 1 detector

We present the investigation of the use of Optick

Study of the rare decay J ⁣/ψ→μ+μ−μ+μ−J\mskip -3mu/\mskip -2mu\psi \to \mu^+\mu^-\mu^+\mu^-

The rare electromagnetic $J\mskip -3mu/\mskip -2mu\psi \to \mu^+\mu^-\mu^+\mu^-$ decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016--2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4\,\text{fb}^{-1}$. The rate of this decay is measured relative to that of the $J\mskip -3mu/\mskip -2mu\psi \to \mu^+\mu^-$ mode. Using the QED model for the four-muon decay in the efficiency estimation, its branching fraction is determined to be \begin{equation*} {\mathcal{B}}(J\mskip -3mu/\mskip -2mu\psi \to \mu^+\mu^-\mu^+\mu^-) = (1.13\pm0.10\pm0.05\pm0.01)\times 10^{-6}, \end{equation*} where the uncertainties are statistical, systematic and due to the uncertainty on the branching fraction of the $J\mskip -3mu/\mskip -2mu\psi \to \mu^+\mu^-$ decay.The rare electromagnetic $J/\psi \to \mu^+\mu^-\mu^+\mu^-$ decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016-2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4\,\text{fb}^{-1}$. The rate of this decay is measured relative to that of the $J/\psi \to \mu^+\mu^-$ mode. Using the QED model for the four-muon decay in the efficiency estimation, its branching fraction is determined to be \begin{equation*} {\mathcal{B}}(J/\psi \to \mu^+\mu^-\mu^+\mu^-) = (1.13\pm0.10\pm0.05\pm0.01)\times 10^{-6}, \end{equation*} where the uncertainties are statistical, systematic and due to the uncertainty on the branching fraction of the $J/\psi \to \mu^+\mu^-$ decay

Probing the nature of the χc1(3872)\chi_{c1}(3872) state using radiative decays

International audienceThe radiative decays $\chi_{c1}(3872)\rightarrow\psi(2S)\gamma$ and $\chi_{c1}(3872)\rightarrow J/\psi\gamma$ are used to probe the~nature of the~$\chi_{c1}(3872)$ state using proton-proton collision data collected with the LHCb detector, corresponding to an~integrated luminosity of~9fb$^{-1}$. Using the~$B^+\rightarrow \chi_{c1}(3872)K^+$decay, the $\chi_{c1}(3872)\rightarrow \psi(2S)\gamma$ process is observed for the first time and the ratio of its partial width to that of the $\chi_{c1}(3872)\rightarrow J/\psi\gamma$ decay is measured to be $$\frac{\Gamma_{\chi_{c1}(3872)\rightarrow \psi(2S)\gamma}} {\Gamma_{\chi_{c1}(3872)\rightarrow J/\psi\gamma}} = 1.67 \pm 0.21 \pm 0.12 \pm0.04 ,$$ where the first uncertainty is statistical, the second systematic and the third is due to the uncertainties on the branching fractions of the $\psi(2S)$ and $J/\psi$ mesons. The measured ratio makes the interpretation of the $\chi_{c1}(3872)$ state as a~pure $D^0\bar{D}^{*0}+\bar{D}^0D^{*0}$ molecule questionable and strongly indicates a sizeable compact charmonium or tetraquark component within the $\chi_{c1}(3872)$ state

Amplitude analysis of B+→ψ(2S)K+π+π−B^+ \to \psi(2S) K^+ \pi^+ \pi^- decays

International audienceThe first full amplitude analysis of $B^+ \to \psi(2S) K^+ \pi^+ \pi^-$ decays is performed using proton-proton collision data corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$ recorded with the LHCb detector. The rich $K^+ \pi^+ \pi^-$ spectrum is studied and the branching fractions of the resonant substructure associated with the prominent $K_1(1270)^+$ contribution are measured. The data cannot be described by conventional strange and charmonium resonances only. An amplitude model with 53 components is developed comprising 11 hidden-charm exotic hadrons. New production mechanisms for charged charmonium-like states are observed. Significant resonant activity with spin-parity $J^P = 1^+$ in the $\psi(2S) \pi^+$ system is confirmed and a multi-pole structure is demonstrated. The spectral decomposition of the $\psi(2S) \pi^+ \pi^-$ invariant-mass structure, dominated by $X^0 \to \psi(2S) \rho(770)^0$ decays, broadly resembles the $J/\psi \phi$ spectrum observed in $B^+ \to J/\psi \phi K^+$ decays. Exotic $\psi(2S) K^+ \pi^-$ resonances are observed for the first time

Probing the nature of the χc1(3872)\chi_{c1}(3872) state using radiative decays

International audienceThe radiative decays $\chi_{c1}(3872)\rightarrow\psi(2S)\gamma$ and $\chi_{c1}(3872)\rightarrow J/\psi\gamma$ are used to probe the~nature of the~$\chi_{c1}(3872)$ state using proton-proton collision data collected with the LHCb detector, corresponding to an~integrated luminosity of~9fb$^{-1}$. Using the~$B^+\rightarrow \chi_{c1}(3872)K^+$decay, the $\chi_{c1}(3872)\rightarrow \psi(2S)\gamma$ process is observed for the first time and the ratio of its partial width to that of the $\chi_{c1}(3872)\rightarrow J/\psi\gamma$ decay is measured to be $$\frac{\Gamma_{\chi_{c1}(3872)\rightarrow \psi(2S)\gamma}} {\Gamma_{\chi_{c1}(3872)\rightarrow J/\psi\gamma}} = 1.67 \pm 0.21 \pm 0.12 \pm0.04 ,$$ where the first uncertainty is statistical, the second systematic and the third is due to the uncertainties on the branching fractions of the $\psi(2S)$ and $J/\psi$ mesons. The measured ratio makes the interpretation of the $\chi_{c1}(3872)$ state as a~pure $D^0\bar{D}^{*0}+\bar{D}^0D^{*0}$ molecule questionable and strongly indicates a sizeable compact charmonium or tetraquark component within the $\chi_{c1}(3872)$ state

Study of the rare decay J/ψ→μ+μ−μ+μ−J/\psi \to \mu^+\mu^-\mu^+\mu^-

International audienceThe rare electromagnetic $J/\psi \to \mu^+\mu^-\mu^+\mu^-$ decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016-2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4\,\text{fb}^{-1}$. The rate of this decay is measured relative to that of the $J/\psi \to \mu^+\mu^-$ mode. Using the QED model for the four-muon decay in the efficiency estimation, its branching fraction is determined to be \begin{equation*} {\mathcal{B}}(J/\psi \to \mu^+\mu^-\mu^+\mu^-) = (1.13\pm0.10\pm0.05\pm0.01)\times 10^{-6}, \end{equation*} where the uncertainties are statistical, systematic and due to the uncertainty on the branching fraction of the $J/\psi \to \mu^+\mu^-$ decay

Amplitude analysis of B+→ψ(2S)K+π+π−B^+ \to \psi(2S) K^+ \pi^+ \pi^- decays

International audienceThe first full amplitude analysis of $B^+ \to \psi(2S) K^+ \pi^+ \pi^-$ decays is performed using proton-proton collision data corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$ recorded with the LHCb detector. The rich $K^+ \pi^+ \pi^-$ spectrum is studied and the branching fractions of the resonant substructure associated with the prominent $K_1(1270)^+$ contribution are measured. The data cannot be described by conventional strange and charmonium resonances only. An amplitude model with 53 components is developed comprising 11 hidden-charm exotic hadrons. New production mechanisms for charged charmonium-like states are observed. Significant resonant activity with spin-parity $J^P = 1^+$ in the $\psi(2S) \pi^+$ system is confirmed and a multi-pole structure is demonstrated. The spectral decomposition of the $\psi(2S) \pi^+ \pi^-$ invariant-mass structure, dominated by $X^0 \to \psi(2S) \rho(770)^0$ decays, broadly resembles the $J/\psi \phi$ spectrum observed in $B^+ \to J/\psi \phi K^+$ decays. Exotic $\psi(2S) K^+ \pi^-$ resonances are observed for the first time

Study of the rare decay J/ψ→μ+μ−μ+μ−J/\psi \to \mu^+\mu^-\mu^+\mu^-

International audienceThe rare electromagnetic $J/\psi \to \mu^+\mu^-\mu^+\mu^-$ decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016-2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4\,\text{fb}^{-1}$. The rate of this decay is measured relative to that of the $J/\psi \to \mu^+\mu^-$ mode. Using the QED model for the four-muon decay in the efficiency estimation, its branching fraction is determined to be \begin{equation*} {\mathcal{B}}(J/\psi \to \mu^+\mu^-\mu^+\mu^-) = (1.13\pm0.10\pm0.05\pm0.01)\times 10^{-6}, \end{equation*} where the uncertainties are statistical, systematic and due to the uncertainty on the branching fraction of the $J/\psi \to \mu^+\mu^-$ decay

Amplitude analysis of B+→ψ(2S)K+π+π−B^+ \to \psi(2S) K^+ \pi^+ \pi^- decays

International audienceThe first full amplitude analysis of $B^+ \to \psi(2S) K^+ \pi^+ \pi^-$ decays is performed using proton-proton collision data corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$ recorded with the LHCb detector. The rich $K^+ \pi^+ \pi^-$ spectrum is studied and the branching fractions of the resonant substructure associated with the prominent $K_1(1270)^+$ contribution are measured. The data cannot be described by conventional strange and charmonium resonances only. An amplitude model with 53 components is developed comprising 11 hidden-charm exotic hadrons. New production mechanisms for charged charmonium-like states are observed. Significant resonant activity with spin-parity $J^P = 1^+$ in the $\psi(2S) \pi^+$ system is confirmed and a multi-pole structure is demonstrated. The spectral decomposition of the $\psi(2S) \pi^+ \pi^-$ invariant-mass structure, dominated by $X^0 \to \psi(2S) \rho(770)^0$ decays, broadly resembles the $J/\psi \phi$ spectrum observed in $B^+ \to J/\psi \phi K^+$ decays. Exotic $\psi(2S) K^+ \pi^-$ resonances are observed for the first time