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K. Azizi

Publications and source records attributed to K. Azizi.

At least 271 records · Page 15Linked to original sources
arXiv2012

Comparative analysis of the semileptonic $Λ_b \rightarrow Λ\ell^+ \ell^-$ transition in SM and different SUSY scenarios using form factors from full QCD

We work out the semileptonic $Λ_b\rightarrow Λ\ell^+ \ell^-$ transition in standard as well as different supersymmetric models. In particular, considering the parametrization of the matrix elements entered the low energy effective Hamiltonian in terms of form factors in full QCD, we calculate the amplitude and differential decay rate responsible for this decay channel in supersymmetric models. We then use the form factors calculated via light cone QCD sum rules in full theory to analyze the differential branching ratio and lepton forward-backward asymmetry of this decay channel in different supersymmetric models and compare the obtained results with those of the standard model. We also discuss how the results of different supersymmetric models deviate from the standard model predictions and which SUSY scenarios are favored.

hep-ph↗
arXiv2012

Doubly heavy spin--1/2 baryon spectrum in QCD

We calculate the mass and residue of the heavy spin--1/2 baryons containing two heavy b or c quarks in the framework of QCD sum rules. We use the most general form of the interpolating current in its symmetric and anti-symmetric forms with respect to the exchange of heavy quarks, to calculate the two-point correlation functions describing the baryons under consideration. A comparison of the obtained results with existing predictions from various approaches is also made.

hep-ph↗
arXiv2012

Semileptonic transition of P wave bottomonium $χ_{b0}(1P)$ to $B_{c}$ meson

Taking into account the two-gluon condensate contributions, the transition form factors enrolled to the low energy effective Hamiltonian describing the semileptonic $χ_{b0}\rightarrow B_{c}\ell\barν, (\ell=(e,μ,τ))$ decay channel are calculated within three-point QCD sum rules. The fit function of the form factors then are used to estimate the decay width of the decay mode under consideration.

hep-ph↗
arXiv2012

Mixing angle of doubly heavy baryons in QCD

We calculate the mixing angles between the spin--1/2, $Ξ_{bc}$--$Ξ^\prime_{bc}$ and $Ω_{bc}$--$Ω^\prime_{bc}$ states of doubly heavy baryons within the QCD sum rules method. It is found that the mixing angles are large and have the values $φ_{Ξ_{bc}} = 16^0 \pm 5^0$ and $φ_{Ω_{bc}} = 18^0 \pm 6^0$, respectively. The mixing angles are slightly smaller compared to the predictions of the non--relativistic quark model, $φ_{Ξ_{bc}} = 25.5^0$ and $φ_{Ω_{bc}} = 25.9^0$.

hep-ph↗
arXiv2012

Spectrum of the heavy axial vector χ_b1(1P) and χ_c1(1P) mesons in thermal QCD

Using the additional operators coming up at finite temperature, we calculate the masses and decay constants of the P wave heavy axial-vector χ_b1 and χ_c1 quarkonia in the framework of thermal QCD sum rules. In the calculations, we take into account the perturbative two loop order alpha_s corrections and nonperturbative effects up to the dimension four condensates. It is observed that the masses and decay constants almost remain unchanged with respect to the variation of the temperature up to T \simeq 100 MeV, however after this point, the decay constants decrease sharply and approach approximately to zero at critical temperature. The decreasing in values of the masses is also considerable after T \simeq 100 MeV .

hep-ph↗
arXiv2012

Constraint on compactification scale via recently observed baryonic $Λ_b\rightarrow Λ\ell^+ \ell^-$ channel and analysis of the $Σ_b \rightarrow Σ\ell^+ \ell^-$ transition in SM and UED scenario

We obtain a lower limit on the compactification scale of extra dimension via comparison of the branching ratio in the baryonic $Λ_b\rightarrow Λμ^+ μ^-$ decay channel recently measured by CDF collaboration and our previous theoretical study. We also use the newly available form factors calculated via light cone QCD sum rules in full theory to analyze the flavour changing neutral current process of the $Σ_b \rightarrow Σ\ell^+ \ell^-$ in universal extra dimension scenario in the presence of a single extra compact dimension. We calculate various physical quantities like branching ratio, forward-backward asymmetry, baryon polarizations and double lepton polarization asymmetries defining the decay channel under consideration. We also compare the obtained predictions with those of the standard model.

hep-ph↗
arXiv2012

Double-Lepton Polarization Asymmetries and Branching Ratio of the $B\rar γl^+ l^- $ transition in Universal Extra Dimension

We study the radiative dileptonic $B \rar γl^+ l^- $ transition in the presence of a universal extra dimension in the Applequist-Cheng-Dobrescu model. In particular, using the corresponding form factors calculated via light cone QCD sum rules, we analyze the branching ratio and double lepton polarization asymmetries related to this channel and compare the results with the predictions of the standard model. We show how the results deviate from predictions of the standard model at lower values of the compactification factor ($1/R $) of extra dimension.

hep-ph↗
arXiv2011

Systematic analysis of the $ B_s\rightarrow f_0 \ell^+\ell^- $ in the universal extra dimension

Using form factors enrolled to the transition matrix elements and calculated via light-cone QCD sum rules including next-to-leading order corrections in the strong coupling constant, we provide a systematic analysis of the $ B_s\rightarrow f_0 (980)\ell^+\ell^- $ both in the standard and universal extra dimension models. In particular, we discuss sensitivity of the differential branching ratio and various double lepton polarization asymmetries on the compactification factor of extra dimension and show how the results of the extra dimension model deviate from the standard model predictions. The order of branching ratio makes this decay mode possible to be checked at LHCb in near future.

hep-ph↗
arXiv2011

Analysis of $Λ_b \rar Λ\ell^+ \ell^-$ transition in SM4 using form factors from Full QCD

Using the responsible form factors calculated via full QCD, we analyze the $Λ_{b}\rightarrow Λ\ell^{+}\ell^{-}$ transition in the standard model containing fourth generation quarks (SM4). We discuss effects of the presence of $t'$ fourth family quark on related observables like branching ratio, forward-backward asymmetry, baryon polarization as well as double lepton polarization asymmetries. We also compare our results with those obtained in the SM as well as with predictions of the SM4 but using form factors calculated within heavy quark effective theory. The obtained results on branching ratio indicate that the $Λ_{b}\rightarrow Λ\ell^{+}\ell^{-}$ transition is more probable in full QCD comparing to the heavy quark effective theory. It is also shown that the results on all considered observables in SM4 deviate considerably from the SM predictions when $m_{t'}\geq 400 GeV$.

hep-ph↗
arXiv2011

Semileptonic transition of $Σ_{b}$ to $Σ$ in Light Cone QCD Sum Rules

We use distribution amplitudes of the light $Σ$ baryon and the most general form of the interpolating current for heavy $Σ_b$ baryon to investigate the semileptonic $Σ_b\rightarrow Σl^+l^-$ transition in light cone QCD sum rules. We calculate all twelve form factors responsible for this transition and use them to evaluate the branching ratio of the considered channel. The order of branching fraction shows that this channel can be detected at LHC.

hep-ph↗
arXiv2011

Light cone QCD sum rules study of the semileptonic heavy $Ξ_{Q}$ and $Ξ'_{Q}$ transitions to $Ξ$ and $Σ$ baryons

The semileptonic decays of heavy spin--1/2, $Ξ_{b(c)}$ and $Ξ'_{b(c)}$ baryons to the light spin-- 1/2, $Ξ$ and $Σ$ baryons are investigated in the framework of the light cone QCD sum rules. In particular, using the most general form of the interpolating currents for the heavy baryons as well as the distribution amplitudes of the $Ξ$ and $Σ$ baryons, we calculate all form factors entering the matrix elements of the corresponding effective Hamiltonians in full QCD. Having calculated the responsible form factors, we evaluate the decay rates and branching fractions of the related transitions.

hep-ph↗
arXiv2011

Investigation of heavy-heavy pseudoscalar mesons in thermal QCD Sum Rules

We investigate the mass and decay constant of the heavy-heavy pseudoscalar, $B_c$, $η_c$ and $η_b$ mesons in the framework of finite temperature QCD sum rules. The annihilation and scattering parts of spectral density are calculated in the lowest order of perturbation theory. Taking into account the additional operators arising at finite temperature, the nonperturbative corrections are also evaluated. The masses and decay constants remain unchanged under $T\cong 100 ~MeV$, but after this point, they start to diminish with increasing the temperature. At critical or deconfinement temperature, the decay constants reach approximately to 35% of their values in the vacuum, while the masses are decreased about 7%, 12% and 2% for $B_c$, $η_c$ and $η_b$ states, respectively. The results at zero temperature are in a good consistency with the existing experimental values as well as predictions of the other nonperturbative approaches.

hep-ph↗
arXiv2011

Strong coupling constants of heavy spin--3/2 baryons with light pseudoscalar mesons

The strong coupling constants among members of the heavy spin--3/2 baryons containing single heavy quark with light pseudoscalar mesons are calculated in the framework of the light cone QCD sum rules. Using symmetry arguments, the structure independent relations among different correlation functions are obtained. It is shown that all possible transitions can be described in terms of one universal invariant function whose explicit expression is Lorenz structure dependent.

hep-ph↗
arXiv2011

Masses and decay constants of bound states containing fourth family quarks from QCD sum rules

The heavy fourth generation of quarks that have sufficiently small mixing with the three known SM families form hadrons. In the present work, we calculate the masses and decay constants of mesons containing either both quarks from the fourth generation or one from fourth family and the other from known third family SM quarks in the framework of the QCD sum rules. In the calculations, we take into account two gluon condensate diagrams as nonperturbative contributions. The obtained results reduce to the known masses and decay constants of the $\bar b b$ and $\bar c c$ quarkonia when the fourth family quark is replaced by the bottom or charm quark.

hep-ph↗
arXiv2011

Vertices of the heavy spin-3/2 sextet baryons with light vector mesons in QCD

All transitions among the heavy spin--3/2 sextet baryons with participation of the light vector mesons $(B_Q^* B_Q V)$ are investigated in the framework of the light cone sum rules. These vertices are described by four coupling constants. The corresponding sum rules are derived for each coupling constant. It is shown that the correlation functions of different transitions can be described by only one invariant function.

hep-ph↗
arXiv2011

B to strange tensor meson transition in a model with one universal extra dimension

We analyze the semileptonic $B\to K_2^*(1430)l^+l^-$ transition in universal extra dimension model. In particular, we present the sensitivity of related observables such as branching ratio, polarization distribution and forward-backward asymmetry to the compactification factor (1/R) of extra dimension. The obtained results from extra dimension model show overall a considerable deviation from the standard model predictions for small values of the compactification factor. This can be considered as an indication for existence of extra dimensions.

hep-ph↗
arXiv2011

Exclusive $D_{s} \to (η,η^{\prime}) l ν$ decays in light cone QCD

Probing the $\bar ss$ content of the $η$ and $η'$ mesons and considering mixing between these states as well as gluonic contributions, the form factors responsible for semileptonic $D_s \to (η, η') l ν$ transitions are calculated via light cone QCD sum rules. Corresponding branching fractions and their ratio for different mixing angles are also obtained. Our results are in a good consistency with experimental data as well as predictions of other nonperturbative approaches.

hep-ph↗