arXiv subjects

Ilia Belov

Publications and source records attributed to Ilia Belov.

4 recordsLinked to original sources

arXiv2026

Search for $\boldsymbol{π_1(1600)}$ in a three-pion system at GlueX

The GlueX experiment in Hall D at Jefferson Lab enables studies of the light meson spectrum in $γp$ interactions with a linearly polarized photon beam. GlueX aims in particular to search for hybrid mesons that have exotic quantum numbers and therefore cannot be classified as conventional hadrons. We present the search for the $π_1(1600)$ meson by means of a partial-wave analysis of the $π^{+}π^{-}π^{-}$ system produced off the $Δ^{++}$-baryon. Data with the selected three-pion final state are fitted in bins of $m_{3π}$ as coherent sums of partial-wave amplitudes defined in the reflectivity basis. The properties of $a_{2}^{-}(1320)$ production are investigated through the extracted signal in the $ρ\,π^{-}$ $D$-waves. In this analysis, the overall $m_{3π}$ lineshape will be extracted for each of the model contributions. The main interest lies in establishing the existence of a resonant $1^{-+}$ contribution in the $ρ\,π^{-}$ $P$-wave configuration.

hep-ex↗

arXiv2024

Fully charmed tetraquark production at the LHC experiments

We develop the formalism for production of a fully heavy tetraquark and apply it to the calculation of $pp\to T_{4c}+X$ cross-sections. We demonstrate that the production cross-section of a fully heavy tetraquark, even if it is a diquark-antidiquark cluster, can be obtained in the meson-like basis, for which the spin-color projection technique is well established. Prompted by the recent LHCb, ATLAS and CMS data, we perform a pQCD calculation of ${\cal O}(α_s^5)$ short-distance factors in the dominant channel of gluon fusion, and match these to the four-body $T_{4c}$ wave functions in order to obtain the unpolarized $T_{4c}(0^{++},1^{+-},2^{++})$ cross-sections. The novelty in comparison with the recently published article~\cite{Feng:2023agq} lies in the fact that we predict the absolute values as well as the $dσ/dp_T$ spectra in the kinematic ranges accessible at the ongoing LHC experiments. From the comparison with the signal yield at LHCb we derive the constraints on the $Φ\cdot\text{Br}(J/ψ\,J/ψ)$ (reduced wave function times branching) product for the $T_{4c}$ candidates for $X(6900)$ and observe that $X(6900)$ is compatible with a $2^{++}(2S)$ state.

hep-ph↗

arXiv2024

Nonfactorizable charming-loop contribution to FCNC $B_s\to γl^+l^-$ decay

We present the first theoretical calculation of nonfactorizable charm-quark loop contributions to the $B_s\to γl^+l^-$ amplitude. We calculate the relevant form factors, $H_{A,V}^{\rm NF}(k'^2,k^2)$, and provide convenient parametrizations of our results in the form of fit functions of two variables, $k'^2$ and $k^2$, applicable in the region below hadron resonances, $k'^2 < M_{J/ψ}^2$ and $k^2 < M_ϕ^2$. We report that factorizable and nonfactorizable charm contributions to the $B_s\toγl^+l^-$ amplitude have opposite signs. To compare the charm and the top contributions, it is convenient to express the NF charming loop contribution as a non-universal (i.e., dependent on the reaction) $q^2$-dependent correction $Δ^{\rm NF}C_7(q^2)$ to the Wilson coefficient $C_7$. For the $B_s\toγl^+l^-$ amplitude, the correction is found to be positive, $Δ^{\rm NF} C_7(q^2)/C_7 > 0$.

hep-ph↗

arXiv2023

Charming-loop contribution to $B_s\to γγ$ decay

We present a detailed theoretical study of nonfactorizable contributions of the charm-quark loop to the amplitude of the $B_s\to γ\,γ$ decay. This contribution involves the $B$-meson three-particle Bethe-Salpeter amplitude, $\langle 0|\bar s(y)G_{μν}(x)b(0)|\bar B_s(p)\rangle$, for which we take into account constraints from analyticity and continuity. The charming-loop contribution of interest may be described as a correction to the Wilson coefficient $C_{7γ}$, $C_{7γ}\to C_{7γ}(1+δC_{7γ})$. We calculate an explicit dependence of $δC_{7γ}$ on the parameter $λ_{B_s}$. Taking into account all theoretical uncertainties, $δC_{7γ}$ may be predicted with better than 10\% accuracy for any given value of $λ_{B_s}$. For our benchmark point $λ_{B_s}=0.45$ GeV, we obtain $δC_{7γ}=0.045\pm 0.004$. Presently, $λ_{B_s}$ is not known with high accuracy, but its value is expected to lie in the range $0.3\le λ_{B_s}({\rm GeV})\le 0.6$. The corresponding range of $δC_{7γ}$ is found to be $0.02\le δC_{7γ}\le 0.1$. One therefore expects the correction given by charming loops at the level of at least a few percent.

hep-ph↗