arXiv subjects

K. Azizi

Publications and source records attributed to K. Azizi.

At least 217 records · Page 12Linked to original sources

arXiv2017

Interpretation of the new $Ω_c^{0}$ states via their mass and width

The mass and pole residue of the ground and first radially excited $ Ω_c^{0}$ states with spin-parities $J^{P}=1/2^{+},\,3/2^{+}$, as well as P-wave $Ω_c^{0}$ with $J^{P}=1/2^{-},\,3/2^{-}$ are calculated by means of the two-point QCD sum rules. The strong decays of $Ω_c^{0}$ baryons are also studied and width of these decay channels are computed. The relevant computations are performed in the context of the full QCD sum rules on the light-cone. Obtained results for the masses and widths are confronted with recent experimental data of LHCb Collaboration, which allow us to interpret $Ω_c(3000)^{0}$, $Ω_c(3050)^{0}$, and $ Ω_c(3119)^{0} $ as the excited $css$ baryons with the quantum numbers $ (1P,\,1/2^{-})$, $(1P,\,3/2^{-})$, and $(2S,\,3/2^{+})$, respectively. The $ (2S,\,1/2^{+})$ state can be assigned either to $Ω_c(3066)^{0}$ state or $Ω_c(3090)^{0}$ excited baryon.

hep-ph↗

arXiv2017

Analysis of $P_c^+(4380)$ and $P_c^+(4450)$ as pentaquark states in the molecular picture with QCD sum rules

To better understand the nature and internal structure of the exotic states discovered by many collaborations, more information on their electromagnetic properties and their strong and weak interactions with other hadrons is needed. The residue or current coupling constant of these states together with their mass are the main inputs in determinations of such properties. We perform QCD sum rules analyses on the hidden-charm pentaquark states with spin-parities $ J^{P}= \frac{3}{2}^{\pm}$ and $ J^{P}= \frac{5}{2}^{\pm}$ to calculate their residue and mass. In the calculations, we adopt a molecular picture for $ J^{P}= \frac{3}{2}^{\pm}$ states and a mixed current in a molecular form for $ J^{P}= \frac{5}{2}^{\pm}$. Our analyses show that the $P_c^+(4380)$ and $P_c^+(4450)$, observed by LHCb Collaboration, can be considered as hidden-charm pentaquark states with $ J^{P}= \frac{3}{2}^{-}$ and $ J^{P}= \frac{5}{2}^{+}$, respectively.

hep-ph↗

arXiv2017

On the nature of the newly discovered $Ω_c^{0}$ states

The masses and residues of the radially excited heavy $Ω_c^{0}$ and $ Ω_b^{-}$ baryons with spin-parity $J^{P}=\frac{1}{2}^{+}$ and $J^{P}= \frac{3}{2}^{+}$ are calculated by means of QCD two-point sum rule method using the general form of their interpolating currents. In calculations the quark, gluon and mixed vacuum condensates up to ten dimensions are taken into account. In $Ω_c^{0}$ channel a comparison is made with the narrow excited states recently observed by the LHCb Collaboration.

hep-ph↗

arXiv2017

Scalar and vector self-energies of heavy baryons in nuclear medium

The in-medium sum rules are employed to calculate the shifts in the mass and residue as well as the scalar and vector self-energies of the heavy $Λ_Q, Σ_Q$ and $Ξ_Q$ baryons, with Q being $b$ or $c$ quark. The maximum shift in mass due to nuclear matter belongs to the $Σ_c$ baryon and it is found to be $Δm_{Σ_{c}}=-936 ~ MeV$. In the case of residue, it is obtained that the residue of $Σ_b$ baryon is maximally affected by the nuclear medium with the shift $Δλ_{Σ_b} = -0.014 ~ GeV^3 $. The scalar and vector self-energies are found to be $Σ^{S}_{Λ_b} = 653 ~ MeV$, $Σ^{S}_{Σ_b} = -614 ~ MeV $, $Σ^{S}_{Ξ_b} = -17 ~ MeV $, $Σ^{S}_{Λ_c} = 272 ~ MeV $, $Σ^{S}_{Σ_c} = -936 ~ MeV $, $Σ^{S}_{Ξ_c} = -5 ~ MeV $ and $Σ^ν_{Λ_b} = 436 \pm 148 ~ MeV $, $Σ^ν_{Σ_b} = 382 \pm 129 ~MeV $, $Σ^ν_{Ξ_b} =15 \pm 5 ~ MeV$, $Σ^ν_{Λ_c} = 151 \pm 45 ~ MeV $, $Σ^ν_{Σ_c} = 486 \pm 144 ~ MeV $ and $Σ^ν_{Ξ_c} = 1.391 \pm 0.529 ~ MeV $.

hep-ph↗

arXiv2017

Radial Excitations of the Decuplet Baryons

The ground and first excited states of the decuplet baryons are studied using the two-point QCD sum rule approach. The mass and residue of these states are computed and compared with the existing experimental data and other theoretical predictions. The results for the masses of the ground state particles as well as the excited $ Δ$ and $ Σ^{*} $ states are in good consistency with experimental data. Our results on the excited $ Ξ^{*} $ and $ Ω^{-} $ states reveal that the experimentally poorly known $ Ξ(1950) $ and $ Ω^{-}(2250) $ can be assigned as the first excited states in $ Ξ^{*} $ and $ Ω^{-} $ channels, respectively.

hep-ph↗

arXiv2017

Application of the QCD light cone sum rule to tetraquarks: the strong vertices $X_bX_bρ$ and $X_cX_cρ$

The full version of QCD light-cone sum rule method is applied to tetraquarks containing a single heavy $b$ or $c$ quark. To this end, investigations of the strong vertices $X_{b}X_{b}ρ$ and $X_{c}X_{c}ρ$ are performed, where $X_b=[su][\bar b\bar d]$ and $X_c=[su][\bar c\bar d]$ are the exotic states built of four quarks of different flavors. The strong coupling constants $G_{X_{b}X_{b}ρ}$ and $G_{X_{c}X_{c}ρ}$ corresponding to these vertices are found using the $ρ$-meson leading and higher-twist distribution amplitudes. In the calculations $X_{b}$ and $X_{c}$ are treated as scalar bound states of a diquark and antidiquark.

hep-ph↗

arXiv2017

Open charm-bottom scalar tetraquarks and their strong decays

The mass and meson-current coupling of the diquark-antidiquark states with the quantum numbers $J^{P}=0^{+}$ and quark contents $Z_{q}=[cq][\bar {b} \bar q ]$ and $Z_{s}=[cs][\bar {b} \bar s]$ are calculated using two-point QCD sum rule approach. In calculations the quark, gluon and mixing condensates up to eight dimensions are taken into account. The parameters of the scalar tetraquarks extracted from this analysis are employed to explore the strong vertices $Z_q B_c π$, $Z_q B_c η$ and $Z_s B_c η$ and compute the couplings $g_{Z_qB_c π}$, $g_{Z_qB_c η}$ and $g_{Z_sB_c η}$. The strong couplings are obtained within the soft-meson approximation of QCD light-cone sum rule method: they form, alongside with other parameters, the basis for evaluating the widths of $Z_q \to B_c π$, $% Z_q \to B_c η$ and $Z_s \to B_c η$ decays. Obtained in this work results for the mass of the tetraquarks $Z_{q}$ and $Z_{s}$ are compared with available predictions presented in the literature.

hep-ph↗

arXiv2017

Resonance $X(5568)$ as an exotic axial-vector state

The mass and meson-current coupling constant of the resonance $X(5568)$, as well as the width of the decay $X(5568)\to B_s^{\ast}π$ are calculated by modeling the exotic $X(5568)$ resonance as a diquark-antidiquark state $% X_b=[su][bd]$ with quantum numbers $J^{P}=1^{+}$. The calculations are made employing QCD two-point sum rule method, where the quark, gluon and mixed vacuum condensates up to dimension eight are taken into account. The sum rule approach on the light-cone in its soft-meson approximation is used to explore the vertex $X_bB_{s}^{\ast}π$ and extract the strong coupling $% g_{X_bB_{s}^{\ast}π}$, which is a necessary ingredient to find the width of the $X_b \to B_s^{\ast}π^{+}$ decay process. The obtained predictions are compared with the experimental data of the D0 Collaboration, and results of other theoretical works.

hep-ph↗

arXiv2016

Mass and magnetic dipole moment of negative parity heavy baryons with spin--3/2

We calculate the mass and residue of the heavy spin--3/2 negative parity baryons with single heavy bottom or charm quark by the help of a two-point correlation function. We use the obtained results to investigate the diagonal radiative transitions among the baryons under consideration. In particular, we compute corresponding transition form factors via light cone QCD sum rules which are then used to obtain the magnetic dipole moments of the heavy spin--3/2 negative parity baryons. We remove the pollutions coming from the positive parity spin--3/2 and positive/negative parity spin--1/2 baryons by constructing sum rules for different Lorentz structures. We compare the results obtained with the existing theoretical predictions.

hep-ph↗

arXiv2016

Impact of finite density on spectroscopic parameters of decuplet baryons

The decuplet baryons, $Δ$, $Σ^{*}$, $Ξ^{*}$ and $Ω^{-}$, are studied in nuclear matter by using the in-medium QCD sum rules. By fixing the three momentum of the particles under consideration at the rest frame of the medium, the negative energy contributions are removed. It is obtained that the parameters of the $Δ$ baryon are more affected by the medium against the $Ω^{-}$ state, containing three strange quarks, whose mass and residue do not affected by the medium, considerably. We also find the vector and scalar self energies of these baryons in nuclear matter. By the recent progresses at $\bar{P}$ANDA experiment at FAIR and NICA facility it may be possible to study the in-medium properties of such states even the multi-strange $Ξ^{*}$ and $Ω^{-}$ systems in near future.

nucl-th↗

arXiv2016

Decuplet baryons in a hot medium

The thermal properties of the light decuplet baryons are investigated in the framework of the thermal QCD sum rules. In particular, the behavior of the mass and residue of the $Δ$, $Σ^{*}$, $Ξ^{*}$ and $Ω$ baryons with respect to temperature are analyzed taking into account the additional operators coming up in the Wilson expansion at finite temperature. It is found that the mass and residue of these particles remain overall unaffected up to $T\simeq150~MeV$ but, beyond this point, they start to diminish, considerably.

hep-ph↗

arXiv2016

Exploring $X(5568)$ as a meson molecule

The parameters, i.e. the mass and current coupling of the exotic $X(5568)$ state observed by the D0 Collaboration as well as the decay width of the process $X \to B_s^{0}π^{+}$ are explored using $B\bar{K}$ molecule assumption on its structure. Employed computational methods include QCD two-point and light-cone sum rules, latter being considered in the soft-meson approximation. The obtained results are compared with the data of the D0 Collaboration as well as with the predictions of the diquark-antidiquark model. This comparison strengthens a diquark-antidiquark picture for the $X(5568)$ state rather than a meson molecule structure.

hep-ph↗

arXiv2016

Width of the exotic $X_b(5568)$ state through its strong decay to $B_s^{0} π^{+}$

The width of the newly observed exotic state $X_b(5568)$ is calculated via its dominant strong decay to $% B_s^{0} π^{+}$ using the QCD sum rule method on the light-cone in conjunction with the soft-meson approximation. To this end, the vertex $X_{b}B_{s}π$ is studied and the strong coupling $g_{X_{b}B_{s}π}$ is computed employing for $X_b(5568)$ state the interpolating diquark-antidiquark current of the $[su][\overline{b}\overline{d}]$ type. The obtained prediction for the decay width of $X_b(5568)$ is confronted and a nice agreement found with the experimental data of the D0 Collaboration.

hep-ph↗

arXiv2016

QCD nature of dark energy at finite temperature: cosmological implications

The Veneziano ghost field has been proposed as an alternative source of dark energy whose energy density is consistent with the cosmological observations. In this model, the energy density of QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from late time to early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras. It is found that this model safely defines the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The EoS parameter of dark energy is dynamical and evolves from $-1/3$ in the presence of radiation to $-1$ at late time. The finite temperature ghost dark energy predictions on the Hubble parameter well fit to those of $Λ$CDM and observations at late time.

hep-ph↗

arXiv2016

Mass and decay constant of the newly observed exotic $X(5568)$ state

The mass and decay constant of the $X(5568)$ state newly observed by D0 Collaboration are computed within the two-point sum rule method using the diquark-antidiquark interpolating current. In calculations, the vacuum condensates up to eight dimensions are taken into account. The obtained result for the mass of the $X(5568)$ state is in a nice agreement with the experimental data.

hep-ph↗

arXiv2016

Charmed partner of the exotic $X(5568)$ state and its properties

The mass, decay constant and width of a hypothetical charmed partner $X_c$ of the newly observed exotic $X_b(5568)$ state are calculated using a technique of QCD sum rule method. The $X_c=[su][\overline{c}\overline{d}]$ state with $J^{P}=0^{+}$ is described employing two types of the diquark-antidiquark interpolating currents. The evaluation of the mass $m_{X_c}$ and decay constant $f_{X_c}$ is carried out utilizing the two-point sum rule method by including vacuum condensates up to eight dimensions. The widths of the decay channels $X_c \to D_s^{-} π^{+}$ and $X_c \to D^{0} K^{0}$ are also found. To this end, the strong couplings $g_{X_{c}D_{s}π}$ and $g_{X_{c}D K}$ are computed by means of QCD sum rules on the light-cone and soft-meson approximation.

hep-ph↗

arXiv2016

Strong $Z_c^{+}(3900)\rightarrow J/ψπ^{+}; η_{c} ρ^{+}$ decays in QCD

The widths of the strong decays $Z_c^{+}(3900)\to J/ψπ^{+}$ and $Z_c^{+}(3900)\to η_{c} ρ^{+}$ are calculated. To this end, the mass and decay constant of the exotic $Z_c^{+}(3900)$ state are computed by means of a two-point sum rule. The obtained results are then used to calculate the strong couplings $g_{Z_{c}J/ψπ}$ and $g_{Z_{c}η_{c} ρ}$ employing QCD sum rules on the light-cone supplied by a technique of the soft-meson approximation. We compare our predictions on the mass and decay widths with available experimental data and other theoretical results.

hep-ph↗

arXiv2016

Transition Form Factors of $χ_{b2}(1P)\rightarrow B_{c}\bar{l}ν$ in QCD

The form factors of the semileptonic $χ_{b2}(1P)\rightarrow B_{c}\bar{l}ν$ decay are calculated using the QCD sum rule approach. The results obtained are then used to estimate the decay widths of this transition in all lepton channels. The orders of decay rates indicate that this transition is accessible at LHC for all lepton channels.

hep-ph↗