Branching fraction measurement of the decay $B^+ \to ψ(2S) φ(1020) K^+$ (2503.02711v2)

Abstract: The branching fraction of the decay $B^+\to \psi(2S)\phi(1020)K^+$, relative to the topologically similar decay $B^+\to J/\psi \phi(1020) K^+$, is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of $9\,\mathrm{fb}^{-1}$. The ratio is found to be $0.061 \pm 0.004 \pm 0.009$, where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for $B^+ \to J/\psi \phi(1020) K^+$, the branching fraction for the decay $B^+\to \psi(2S) \phi(1020) K^+$ is found to be $ (3.0 \pm 0.2 \pm 0.5 \pm 0.2) \times 10^{-6}$, where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel.

Branching Fraction Measurement of the Decay $B^+ \to \psi(2S)\phi(1020)K^+$

This paper presents a detailed paper on the branching fraction measurement of the decay $B^+ \to \psi(2S)\phi(1020)K^+$, performed by the LHCb collaboration. Utilizing proton-proton collision data collected at the LHCb detector across different center-of-mass energies (7, 8, and 13 TeV), the analysis engages a dataset corresponding to an integrated luminosity of 9 fb$^-1$.

Experimental Context and Objectives

The decay processes involved are mediated through the $b \to c\bar{c}s$ transition, which shares topological similarities with the decay $B^+ \to J/\psi\phi(1020)K^+$. Notably, exotic mesonic states such as $\chi_{c1}(4140)$ and $T_{c\bar{c}\bar{s}1}(4000)$ have been observed in the $J/\psi$ counterpart decay. The current paper aims to measure the branching fraction for $\psi(2S)\phi(1020)K^+$, providing insights into potentially observable high-mass resonant contributions.

Methodology and Data Analysis

The analysis employs the ratio of the branching fractions to the normalization decay $B^+ \to J/\psi\phi(1020)K^+$. The ratio $\mathcal{R}_{\text{BF}}$ is derived using the formula:

$$\mathcal{R}_{\text{BF}} = \frac{\ BR(B^+ \to \psi(2S)\phi(1020)K^+)\ }{\ BR(B^+ \to J/\psi\phi(1020)K^+)\ } = \frac{N_\text{Signal}}{N_\text{Norm}} \frac{F_\text{Signal}}{F_\text{Norm}} \frac{\epsilon_\text{Norm}}{\epsilon_\text{Signal}}$$

where $N$, $F$, and $\epsilon$ denote the yields, fractions of $\phi$ contributions, and efficiency for the signal and normalization channels, respectively.

The paper employs a double-sided Crystal Ball function to model signal peak characteristics and utilizes efficiency estimates from simulation data and calibration datasets for particle identification. Systematic uncertainties are meticulously addressed, including those arising from modeling, efficiency calculations, and external branching fraction inputs.

Results and Implications

The result for the branching fraction ratio is calculated as $$\mathcal{R}_{\text{BF}} = 0.061 \pm 0.004 \pm 0.009$$, leading to a branching fraction for the decay $B^+ \to \psi(2S)\phi(1020)K^+$ of $(3.0 \pm 0.2 \pm 0.5 \pm 0.2) \times 10^{-6}$. These results align with earlier CMS measurements, confirming their robustness and indicating a larger amplitude squared in the $\psi(2S)$ decay path compared to $J/\psi$. This significant finding implies enhancements due to resonant states, signifying a promising avenue for further exploration and amplitude analyses in decay processes involving $B^+$ mesons.

This measurement and subsequent analysis offer a refined understanding of the resonance structures within heavy meson decays, holding potential implications for advanced particle physics models that describe subatomic particle interactions. Future research, with increased data samples, may extend these findings, providing a deeper exploration of the mass spectra and exotic state contributions in similar decay systems.