arXiv subjects

Guray Erkol

Publications and source records attributed to Guray Erkol.

12 recordsLinked to original sources

arXiv2020

Charmed baryon spectrum from lattice QCD near the physical point

We calculate the low-lying spectrum of charmed baryons in lattice QCD on the $32^3\times64$, $N_f=2+1$ PACS-CS gauge configurations at the almost physical pion mass of $\sim 156$ MeV/c$^2$. By employing a set of interpolating operators with different Dirac structures and quark-field smearings for the variational analysis, we extract the ground and first few excited states of the spin-$1/2$ and spin-$3/2$, singly-, doubly-, and triply-charmed baryons. Additionally, we study the $Ξ_c$-$Ξ_c^\prime$ mixing and the operator dependence of the excited states in a variational approach. We identify several states that lie close to the experimentally observed excited states of the $Σ_c$, $Ξ_c$ and $Ω_c$ baryons, including some of the $Ξ_c$ states recently reported by LHCb. Our results for the doubly- and triply-charmed baryons are suggestive for future experiments.

hep-lat↗

arXiv2011

Tensor form factors of nucleon in QCD

We extract the isovector tensor nucleon form factors, which play an important role in understanding the transverse spin structure of the nucleon when related to the quark helicity-flip generalized parton distributions via their first moments. We employ the light-cone QCD sum rules to leading order in QCD and include distribution amplitudes up to twist 6 in order to calculate the three tensor form factors $H_T$, $E_T$ and $\tilde{H}_T$. Our results agree well with those from other approaches in the low and high momentum-transfer regions.

hep-ph↗

arXiv2011

Isovector axial-vector form factors of octet baryons in QCD

We compute the diagonal isovector axial-vector as well as induced pseudoscalar form factors of nucleon, $Σ$ and $Ξ$ baryons by employing the light-cone QCD sum rules to leading order in QCD and including distribution amplitudes up to twist 6. Extrapolating our sum-rules results to low-momentum transfers, we make a comparison with experimental and lattice-QCD results where we can achieve a nice qualitative and quantitative agreement.

hep-ph↗

arXiv2009

Pseudoscalar-Meson Octet-Baryon Coupling Constants from two-flavor Lattice QCD

We evaluate the pseudoscalar-meson octet-baryon coupling constants and the corresponding axial charges in eight channels ($πN\N$, $πΣΣ$, $πΛΣ$, $KΛN$, $K ΣN $, $πΞΞ$, $KΛΞ$ and $KΣΞ$) in lattice QCD with two flavors of dynamical quarks. The parameter $α\equiv F/(F+D)$ representing the SU(3)-flavor symmetry is computed at each u,d-quark hopping parameter and at the flavor-SU(3) symmetric point where the three quark flavors are degenerate at the physical $s$-quark mass. In particular, we obtain $α=0.395(6)$ at the SU(3) symmetric limit. The quark-mass dependences of the coupling constants are obtained by changing the $u$- and the $d$-quark masses and we find that the SU(3)-flavor symmetry is broken by only a few percent at each quark-mass we employ.

hep-lat↗

arXiv2005

CP violation in polarized B-> pi ell+ ell- and B-> rho ell+ ell- decays

We study the decay rate and the CP violating asymmetry of the exclusive B-> pi ell+ ell- and B-> rho ell+ ell- decays in the case where one of the final leptons is polarized. We calculate the contributions coming from the individual polarization states in order to identify a so-called wrong sign decay, which is a decay with a given polarization, whose width and CP asymmetry are smaller as compared to the unpolarized one. The results are presented for electron and tau leptons. We observe that in particular decay channels, one can identify a wrong sign decay which is more sensitive to new physics beyond the Standard Model.

hep-ph↗

arXiv2003

The analysis of $B_{d} -> (η, η^{\prime}) \ell^+ \ell^-$ decays in the standard model

We study the differential branching ratio, branching ratio and the CP-violating asymmetry for the exclusive $B_{d}->(η, η^{\prime}) \ell^+ \ell^-$ decays in the standard model. We deduce the $B_{d}->(η, η^{\prime})$ form factors from the form factors of $B -> π$ available in the literature, by using the $SU(3)_F$ symmetry. We observe that these decay modes, which are within the reach of forthcoming B-factories, are very promising to observe CP-violation.

hep-ph↗

arXiv2002

CP violation in the radiative dileptonic B-meson decays

We investigate the CP violating asymmetry, the forward backward asymmetry and the CP violating asymmetry in the forward-backward asymmetry for the radiative dileptonic B-meson decays $B_{d}\to γ\ell^+ \ell^-$ for the $\ell= e, μ, τ$ channels. It is observed that these asymmetries are quite sizable and $B_{d}\to γ\ell^+ \ell^-$ decays seem promising for investigating CP violation.

hep-ph↗

arXiv2002

The exclusive $B_s->ϕ\ell^+ \ell^-$ decay in the two Higgs doublet models

We study the differential branching ratio, branching ratio and the forward-backward asymmetry for the exclusive $B_s->ϕ\ell^+ \ell^-$ decay in the two Higgs doublet model. We analyze the dependencies of these quantities on the model parameters and show that these observables are highly sensitive to new physics and hence may provide powerful probe of the SM and beyond.

hep-ph↗

arXiv2002

The exclusive $B -> (K, K^*) \ell^+ \ell^-$ decays in a CP softly broken two Higgs doublet model

We study the differential branching ratio, forward-backward asymmetry, CP-violating asymmetry, CP-violating asymmetry in the forward-backward asymmetry and polarization asymmetries in the $B -> K \ell^+ \ell^-$ and $B -> K^* \ell^+ \ell^-$ decays in the context of a CP softly broken two Higgs doublet model. We analyze the dependencies of these observables on the model parameters by paying a special attention to the effects of neutral Higgs boson (NHB) exchanges and possible CP violating effects. We find that NHB effects are quite significant for both decays. A combined analysis of above-mentioned observables seems to be very promising as a testing ground for new physics beyond the SM, especially for the existence of the CP-violating phase in the theory.

hep-ph↗

arXiv2002

The exclusive $B\to π\ell^+ \ell^-$ and $B\to ρ\ell^+ \ell^-$ decays in the general two Higgs doublet model

We study the differential branching ratio, branching ratio and the forward-backward asymmetry for the exclusive $B \to π\ell^+ \ell^-$ and $B \to ρ\ell^+ \ell^-$ decays in the general two Higgs doublet model including the neutral Higgs boson effects. We analyze the dependencies of these quantities on the neutral Higgs boson contributions and the other model parameters. We observe that two Higgs doublet model with the neutral Higgs boson exchanges gives quite sizable contributions to these observables for both channels we consider. Since the neutral Higgs boson exchanges are the only source of the forward-backward asymmetry for $B \to πτ^+ τ^-$ decay, which is at the order of magnitude $1-10%$, measurement of this observable is promising to determine the neutral Higgs boson effects.

hep-ph↗

arXiv2001

Radiative dileptonic decays of B-meson in the general two Higgs doublet model

We investigate the exclusive $B\to γ\ell^+ \ell^- $ decay in the general two Higgs doublet model (model III) including the neutral Higgs boson effects with an emphasis on possible CP-violating effects. For this decay, we analyse the dependencies of the forward-backward asymmetry of the lepton pair, $A_{FB}$, CP-violating asymmetry, $A_{CP}$, and the CP-violating asymmetry in forward-backward asymmetry, $A_{CP}(A_{FB})$, on the model parameters and also on the neutral Higgs boson effects. We have found that $A_{FB}\sim 10^{-1}, 10^{-2}$, $A_{CP}\sim 10^{-2}, 10^{-1}$ and $A_{CP}(A_{FB}) \sim 10^{-2}, 10^{-1}$ depending on the relative magnitude of the Yukawa couplings $\barξ_{N,tt}^{U}$ and $\barξ_{N,bb}^{D}$ in the model III. We also observe that these physical quantities are sensitive to the model parameters and neutral Higgs boson effects are quite sizable for some values of the coupling $\barξ_{N,ττ}^{D}$.

hep-ph↗

arXiv2001

$B\to τ^+ τ^- γ$ decay in the general two Higgs doublet model including the neutral Higgs boson effects

We investigate the differential branching ratio, branching ratio, differential forward-backward asymmetry, the forward-backward asymmetry of the lepton pair and the lepton polarization asymmetry of the exclusive $B\to τ^+ τ^- γ$ decay in the general two Higgs doublet model including the neutral Higgs boson effects. We analyse the dependencies of these quantities on the model parameters and also on the neutral Higgs boson effects. We found that they get considerable enhancement from the two Higgs doublet model compared to the standard model and neutral Higgs boson effects are quite sizable.

hep-ph↗