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Tarik Akan

Publications and source records attributed to Tarik Akan.

5 recordsLinked to original sources

Hybrid Residual Correction of VMC Charmonium Masses with a Screened Funnel Interaction

In this study, we combine residual correction with the physical treatment of charmonium masses within a Quantum Chromodynamics (QCD) motivated potential-model framework via variational Monte Carlo (VMC). The aim is not to propose a new charmonium spectrum, since this sector has already been examined extensively through different potential models. Instead, the main objective is to evaluate how effectively a Machine Learning (ML) correction can improve a VMC baseline when both stages are built on the same screened funnel potential. In this workflow, the screened interaction provides the physical input and determines the underlying mass structure. The proposed run uses the variational method via VMC and deterministic eigenvalue diagonalization in the process of mass calculation. In total, ten charmonium states are calculated, among which seven use the experimental reference masses. The VMC step generates a large set of configurations and local energy estimators that are fed into the neural network (NN) residual corrector at the sample level, while the corrections and experimental uncertainties are collected at the state level. It then learns the residual difference between the raw physics baseline and the internal reference targets. This hybrid procedure reduces the systematic mass offset of the raw calculation across the studied states. For the experimentally verified seven states, the correction reduces the MAE from $438.1~\mathrm{MeV}$ to $24.1~\mathrm{MeV}$, corresponding to a $94.5\%$ reduction. These results show that ML can serve as a residual-correction layer for potential-model spectroscopy.

hep-ph

Spin-averaged $B_c$ Spectrum in a Cornell-type Potential Using VMC Baseline and GFMC Evolution

In this work, the spin-averaged $B_c$ spectrum is computed in a naive Cornell framework, treating the meson as a nonrelativistic system in a spin-independent potential. The Cornell parameters are calibrated directly to the spin-averaged $B_c$ tower by anchoring the $1S$ centroid and scanning a grid in $(\sigma,\kappa)$, with the additive constant $V_0$ fixed at each point by the experimental ground state mass. The spectrum is obtained with a two stage Monte Carlo approach. Variational Monte Carlo (VMC) provides optimized radial trial states with the desired nodal pattern. Fixed node Green's function Monte Carlo (GFMC) then projects the corresponding ground state energies for each $(n,\ell)$ channel. Controlled scans over the GFMC time step, projection time, walker population, and radial grid identify plateau regions where discretization and projection systematics are quantitatively under control. At a representative best point in the low-RMSE valley, the predicted spin-averaged masses agree with the experimental centroids at the level of a few tens of MeV, and the fitted Cornell parameters are consistent with canonical heavy quarkonium analyses.

hep-ph

Charmonium content of $χ_{c1}(3872)$ in light-cone sum rules at twist 3

In this study, we utilize light-cone QCD sum rules at twist-3 accuracy to compute the coupling parameters of the $χ_{c1}(2P)$ state with $D$ and $D^*$ mesons. The analysis reveals that the observed $χ_{c1}(3872)$ meson incorporates significant amounts of both charmonium and molecular components. The interplay between these components highlights the exotic nature of $χ_{c1}(3872)$. Furthermore, implications for a possible mixing between the $χ_{b1}(2P)$ state and a potential $B\bar{B}^*$ molecule is discussed. These findings contribute to the understanding of exotic hadron states and their intricate internal structures.

hep-ph

Semileptonic B_c decays to P-wave charmonia in the light-cone QCDSR

B_c mesons are laboratories for probing heavy quark physics. Furthermore, they decay into charmonia and hence their decays can be used to analyze possible exotic charmonium. In this work, the semileptonic decays of B_c mesons into P wave charmonia are analysed using light cone QCD sum rules (LCSR). The distributions amplitudes for the charmonia are taken from a quark model computation. The obtained decay rates for the ground state and excited charmonia are compared with the results found in the literature.

hep-ph

Finite-volume corrections to the CP-odd nucleon matrix elements of the electromagnetic current from the QCD vacuum angle

Nucleon electric dipole moments originating from strong CP-violation are being calculated by several groups using lattice QCD. We revisit the finite volume corrections to the CP-odd nucleon matrix elements of the electromagnetic current, which can be related to the electric dipole moments in the continuum, in the framework of chiral perturbation theory up to next-to-leading order taking into account the breaking of Lorentz symmetry. A chiral extrapolation of the recent lattice results of both the neutron and proton electric dipole moments is performed, which results in $d_n=(-2.7\pm1.2)\times10^{-16}eθ_0$cm and $d_p=(2.1\pm1.2)\times10^{-16}eθ_0$cm.

hep-ph