arXiv subjects

R. M. Albuquerque

Publications and source records attributed to R. M. Albuquerque.

At least 19 recordsLinked to original sources

arXiv2025

Light scalar quarkonia from QCD Laplace sum rule at higher order

We review our estimations on the light scalar $\bar{q}q$, $(\bar{q}q')(\bar{q'}q)$ and $\overline{qq'}qq'$ ($q,q'\equiv u,d,s$) states from relativistic Laplace sum rule (LSR) within stability criteria and including higher order perturbative (PT) corrections up to the (estimated) N5LO. We evaluate the QCD spectral functions at Lowest Order (LO) of PT QCD and up to the $D=6$ dimension of quark and gluon condensates. Using stability criteria and the constraint: Pole contribution is larger than the QCD continuum one ($R_{P/C}\geqslant 1$) our results exclude an on-shell mass around $(500-600)$ MeV obtained for values of the QCD continuum threshold $t_c \leqslant(1\sim 1.5)$ GeV$^2$. The complete results for the different scalar states are given in Tables 1 to 3. We conclude from the complete analysis that the assignement of the nature of the scalar mesons is not crystal clear and needs further studies.

hep-ph↗

arXiv2024

Light scalar quarkonia from Laplace sum rule at NLO

We review our results on light scalar quarkonia ($\bar{q}q$ and four-quark states) from (inverse) QCD Laplace sum rules (LSR) and their ratios ${\cal R}$ within stability criteria and including higher order perturbative (PT) corrections up to the (estimated) ${\mathcal O}(α_{s}^{5})$. As the Operator Product Expansion (OPE) usually converges for $D\leqslant 6-8$, we evaluated the QCD spectral functions at Lowest Order (LO) of PT QCD and up to the $D=6$ dimension vaccum condensates. We request that the optimal results obey the constraint: Pole (Resonance) contribution to the spectral integral is larger than the QCD continuum one which excludes an on-shell mass around $(500-600)$MeV obtained for values of the QCD continuum threshold $t_c\leqslant(1\sim 1.5)$ GeV$^2$. Our results for the different assignments of the scalar mesons are compiled in Tables 1 to 3

hep-ph↗

arXiv2023

Fully and Doubly-heavy four-quarks within QCD Laplace sum rule

We present a review of our results for the masses and couplings of the scalar fully heavy four-quarks and $T_{QQ\bar{q}\bar{q}'}\, (J^P=0^\pm , 1^\pm)$ tetraquarks states from QCD Laplace sum rule (LSR), their ratios ${\cal R}$ and double ratio of sum rules (DRSR) within stability criteria and including Factorized Next-to-Leading Order (FNLO) Perturbative (PT) corrections. As the Operator Product Expansion (OPE) usually converges for $d\leqslant 6-8$, we evaluated the QCD spectral functions at Lowest Order of PT QCD and up to $\langle G^3 \rangle$. Our results for the $0^{++}$ fully heavy four-quark states may explain the LHCb broad structure around (6.2-6.7)GeV which can be due to $\overline{η_c} η_c,~~ \overline{χ_{c1}}χ_{c1}$ and $\overline{J/ψ}J/ψ$ molecules or/and their analogue $S_c S_c,~~ A_cA_c$ and $V_cV_c$ tetraquarks. The peak at (6.8-6.9)GeV can be identified to the $\overline{χ_{c0}}χ_{c0}$ molecule or/and the $P_c P_c$ tetraquark state. Then, combining ${\cal R}$ and DRSR we focus on the analysis of the four-quark nature of $T_{cc\bar{q}\bar{q}'}$ $1^{\pm}$ and $0^{\pm}$ states. We show that combining ${\cal R}$ and DRSR can provide more precise results: $M_{T^{1^+}_{cc}}=3886(6)$MeV and $M_{T^{0^+}_{cc}}=3883(3)$MeV. From our estimates of the masses of the Pseudoscalar and Vector $T_{cc\bar{q}\bar{q}'}$ states, we observe that the interpolating currents lead to two classes: Class H (Heavy) states with masses around 6GeV and Class L (Light) states around (3.8-4.4)GeV where the pseudoscalar (resp. all vector states) are below the $\overline{D}D_0,~~ overline{D}_s D_{s0}$ (resp. $\overline{D}D_1,~~ \overline{D}_s D_{s1}$) open charm thresholds. Finally, we extend the whole study to the bottom sector and confront our results with the ones from different LSR predictions and some other approaches in the literature.

hep-ph↗

arXiv2023

Doubly-hidden scalar heavy molecules and tetraquarks states from QCD at NLO

Alerted by the recent LHCb discovery of exotic hadrons in the range (6.2 -- 6.9) GeV, we present new results for the doubly-hidden scalar heavy $(\bar QQ) (Q\bar Q)$ charm and beauty molecules using the inverse Laplace transform sum rule (LSR) within stability criteria and including the Next-to-Leading Order (NLO) factorized perturbative and $\langle G^3\rangle$ gluon condensate corrections. We also critically revisit and improve existing Lowest Order (LO) QCD spectral sum rules (QSSR) estimates of the $({ \bar Q \bar Q})(QQ)$ tetraquarks analogous states. In the example of the anti-scalar-scalar molecule, we separate explicitly the contributions of the factorized and non-factorized contributions to LO of perturbative QCD and to the $\langleα_sG^2\rangle$ gluon condensate contributions in order to disprove some criticisms on the (mis)uses of the sum rules for four-quark currents. We also re-emphasize the importance to include PT radiative corrections for heavy quark sum rules in order to justify the (ad hoc) definition and value of the heavy quark mass used frequently at LO in the literature. Our LSR results for tetraquark masses summarized in Table II are compared with the ones from ratio of moments (MOM) at NLO and results from LSR and ratios of MOM at LO (Table IV). The LHCb broad structure around (6.2 --6.7) GeV can be described by the $\overlineη_{c}η_{c}$, $\overline{J/ψ}{J/ψ}$ and $\overlineχ_{c1}χ_{c1}$ molecules or/and their analogue tetraquark scalar-scalar, axial-axial and vector-vector lowest mass ground states. The peak at (6.8--6.9) GeV can be likely due to a $\overlineχ_{c0}χ_{c0}$ molecule or/and a pseudoscalar-pseudoscalar tetraquark state. Similar analysis is done for the scalar beauty states whose masses are found to be above the $\overlineη_bη_b$ and $\overlineΥ(1S)Υ(1S)$ thresholds.

hep-ph↗

arXiv2023

Z_c -like spectra from QCD Laplace sum rules at NLO

We present a global analysis of the observed Z_c, Z_cs and future Z_css-like spectra using the inverse Laplace transform (LSR) version of QCD spectral sum rules (QSSR) within stability criteria. Integrated compact QCD expressions of the LO spectral functions up to dimension-six condensates are given. Next-to-Leading Order (NLO) factorized perturbative contributions are included. We re-emphasize the importance to include PT radiative corrections (though numerically small) for heavy quark sum rules in order to justify the (ad hoc) definition and value of the heavy quark mass used frequently at LO in the literature. We also demonstrate that, contrary to a naïve qualitative 1/N_c counting, the two-meson scattering contributions to the four-quark spectral functions are numerically negligible confirming the reliability of the LSR predictions. Our results are summarized in Tables III to VI. The Z_c(3900) and Z_cs(3983) spectra are well reproduced by the T_c(3900) and T_cs(3973) tetramoles (superposition of quasi-degenerated molecules and tetraquark states having the same quantum numbers and with almost equal couplings to the currents). The Z_c(4025) or Z_c(4040) state can be fitted with the D*_0D_1 molecule having a mass 4023(130) MeV while the Z_cs bump around 4.1 GeV can be likely due to the (D^*_s0D_1+ D^*_0D_s1) molecules. The Z_c(4430) can be a radial excitation of the Z_c(3900) weakly coupled to the current, while all strongly coupled ones are in the region (5634-6527) MeV. The double strange tetramole state T_css which one may identify with the future Z_css is predicted to be at 4064(46) MeV. It is remarkable to notice the regular mass-spliitings of the tetramoles due to SU(3) breakings M_{T_cs}-M_{T_c}= M_{T_css}-M_{T_cs= (73- 91) MeV.

hep-ph↗

arXiv2023

Tests of the Z_c-like Laplace Sum Rule (LSR) results using FESR at NLO

In this note, we use local duality Finite Energy Sum Rule (FESR) to test the validity of the Laplace sum rules (LSR) results truncated at the dimension-six condensates for the estimates of the masses and couplings of the Z_c-like ground states in Ref.1 by taking the example of the D^*D molecule configuration. We confirm the existence of an eventual (D^*D)_1 radial excitation with a mass around 5700 MeV and coupling of 197(25) keV to the current which may mask the eventual Z_c(4430) radial excitation candidate (named (D^*D)_0 in Ref.1) having a relatively small coupling f_{(D^*D)_0}=46(56) keV. We add more explanations on the estimates in Ref.1 from LSR and comment the results in Ref.2.

hep-ph↗

arXiv2022

1+ XTZ States within QCD Sum Rules

We present improved estimates of the couplings, masses and mass ratios of the $X_Q, Z_Q$ and $T_{QQ\bar q\bar q'}$ states using (inverse) QCD Laplace sum rules (LSR), their ratios ${\cal R}$ and double ratios (DRSR), within stability criteria. We conclude that the observed $X_c(3872)$ and $Z_c(3900)$ are tetramoles states (superposition of quasi-degenerated molecule and tetraquark states having similar couplings to the currents) with the predicted masses: $M_{{\cal T}_{X_c}}=3876(44)$ MeV and $M_{{\cal T}_{Z_c}}=3900(42)$ MeV. We also do an extensive analysis of the four-quark nature of different $T_{QQ\bar q\bar q'}$ axial-vector states. Then, combining ${\cal R}$ and DRSR, we reanalyze the observed state $X_c(3872)$ and we obtain a precise prediction of $M_{T_{cc}^{1^+}}$=3886(6) MeV. Extending to the beauty sector, we find the results: $M_{{\cal T}_{Z_b}}=10579(99)$ MeV and $M_{X_b}=10545(131)$ MeV. Finally, we confront our combined LSR $\oplus$ DRSR results with the ones from some other approaches (lattices and quark models).

hep-ph↗

arXiv2022

$0^+$ XTZ states from QCD spectral sum rules

We review our results in\,\cite{ANR22} for the masses and couplings of $T_{ccqq'}\, (J^P=0^+)$ states from (inverse) QCD Laplace sum rule (LSR), their ratios ${\cal R}$ and double ratio of sum rules (DRSR) within stability criteria and including Factorized Next-to-Leading Order (FNLO) Perturbative (PT) corrections and Lowest Order (LO) QCD condensates up to $\langle G^3 \rangle$. We show that combining ${\cal R}$ and DRSR can provide more precise results. Calibrated to the observed $X_c(3872)$ and $T^{1^+}_{cc}(3875)$, ${\cal R}$ combined with DRSR lead to a more precise prediction of $M_{T^{0^+}_{cc}}=3883(3)~\rm{MeV}$. In a similar way, calibrated to the new prediction of $T^{0^+}_{cc}$ ${\cal R} \oplus$DRSR lead to the improved mass predictions: $M_{T^{0^+}_{cc\bar{s}\bar{u}}}=3927(6)~\rm{MeV}$ and $M_{T^{0^+}_{cc\bar{s}\bar{s}}}=3993(11)~\rm{MeV}$. We extend our analysis to the bottom sector and compare our results with the ones from different LSR predictions and some other determinations (lattice, quark and potential models,...) in the literature.

hep-ph↗

arXiv2021

The New Charm-Strange Resonances in the D^- K^+ Channel

We evaluate the masses and decay constants of the $0^+$ and $1^-$ open-charm $(\bar{c}\bar{d})(us)$ tetraquarks and molecular states from QCD spectral sum rules (QSSR) by using QCD Laplace sum rule (LSR). This method takes into account the stability criteria where the factorized perturbative NLO corrections and the contributions of quark and gluon condensates up to dimension-6 in the OPE are included. We confront our results with the $D^- K^+$ invariant mass recently reported by LHCb from $B^+ \to D^+(D^- K^+)$ decays. We expect that the resonance near the $D^- K^+$ threshold can be originated from the $0^{+}(D^-K^+)$ molecule and/or $D^- K^+$ scattering. The $X_0(2900)$ scalar state and the resonance $X_J(3150)$ (if $J = 0$) can emerge from a minimal mixing model, with a tiny mixing angle $θ_0 \simeq (5.2 \pm 1.9)^0$, between a scalar Tetramole $({\cal T}_{\!\!{\cal M}0})$ (superposition of nearly degenerated hypothetical molecules and compact tetraquarks states with the same quantum numbers), having a mass $M_{{\cal T}_{\!\!{\cal M}0}} = 2743(18)$ MeV, and the first radial excitation of the $D^- K^+$ molecule with mass $M_{(DK)_1} = 3678(310)$ MeV. In an analogous way, the $X_1(2900)$ and the $X_J(3350)$ (if $J = 1$) could be a mixture between the vector Tetramole $({\cal T}_{\!\!{\cal M}1})$, with a mass $M_{{\cal T}_{\!\!{\cal M}1}} = 2656(20)$ MeV, and its first radial excitation having a mass $M_{{\cal T}_{\!\!{\cal M}1}} = 4592(141)$ MeV with an angle $θ_0 \simeq (9.1 \pm 0.6)^0$. A (non)-confirmation of these statements requires experimental findings of the quantum numbers of the resonances at $3150$ and $3350$ MeV.

hep-ph↗

arXiv2021

Doubly hidden $0^{++}$ molecules and tetraquarks states from QCD at NLO

Motivated by the LHCb-group discovery of exotic hadrons in the range (6.2 $\sim$ 6.9) GeV, we present new results for the masses and couplings of $0^{++}$ fully heavy $(\bar{Q}Q)(Q\bar{Q})$ molecules and $(QQ)(\overline{QQ})$ tetraquaks states from relativistic QCD Laplace Sum Rule (LSR) within stability criteria where Next-to-Leading Order (NLO) Factorized (F) Perturbative (PT) corrections is included. As the Operator Product Expansion (OPE) usually converges for $d\leqslant 6-8$, we evaluated the QCD spectral functions at Lowest Order (LO) of PT QCD and up to $\langle G^3 \rangle$. We also emphasize the importance of PT radiative corrections for heavy quark sum rules in order to justify the use of the running heavy quark mass value in the analysis. We compare our predictions in Table 3 with the ones from ratio of Moments (MOM). The broad structure arround (6.2 $\sim$ 6.9) GeV can be described by the $\overlineη_cη_c$, $\overline{J/ψ}J/ψ$ and $\overlineχ_{c1}χ_{c1}$ molecules or/and $\overline{S}_c S_c$, $\overline{A}_c A_c$ and $\overline{V}_c V_c$ tetraquarks lowest mass ground states. The narrow structure at (6.8 $\sim$ 6.9) GeV if it is a $0^{++}$ state can be a $\overlineχ_{c0}χ_{c0}$ molecules or/and its analogue $\overline{P}_c P_c$ tetraquark. The $\overlineχ_{c1}χ_{c1}$ predicted mass is found to be below the $χ_{c1}χ_{c1}$ threshold while for the beauty states, all of the estimated masses are above the $η_b η_b$ and $Υ(1S)Υ(1S)$ threshold.

hep-ph↗

arXiv2020

$X_{0,1}$(2900) and $(D^-K^+)$ invariant mass from QCD Laplace sum rules at NLO

We revisit, improve and complete some recent estimates of the $0^{+}$ and $1^-$ open charm $(\bar c \bar d)(us)$ tetraquarks and the corresponding molecules masses and decay constants from QCD spectral sum rules (QSSR) by using QCD Laplace sum rule (LSR) within stability criteria where the factorised perturbative NLO corrections and the contributions of quark and gluon condensates up to dimension-6 in the OPE are included. We confront our results with the $D^-K^+$ invariant mass recently reported by LHCb from $B^+\to D^+(D^-K^+)$ decays. We expect that the bump near the $D^-K^+$ threshold can be originated from the $0^{++}(D^-K^+)$ molecule and/or $D^-K^+$ scattering. The prominent $X_{0}$(2900) scalar peak and the bump $X_J(3150)$ (if $J=0$) can emerge from a {\it minimal mixing model}, with a tiny mixing angle $θ_0\simeq (5.2\pm 1.9)^0$, between a scalar {\it Tetramole} (${\cal T_M}_0$) (superposition of nearly degenerated hypothetical molecules and compact tetraquarks states with the same quantum numbers) having a mass $M_{{\cal T_M}_0}$=2743(18) MeV and the first radial excitation of the $D^-K^+$ molecule with mass $M_{(DK)_1}=3678(310)$ MeV. In an analogous way, the $X_1$(2900) and the $X_J(3350)$ (if $J=1$) could be a mixture between the vector {\it Tetramole} $({\cal T_M}_1)$ with a mass $M_{{\cal T_M}_1}=2656(20)$ MeV and its first radial excitation having a mass $M_{({\cal T_M}_1)_1}=4592(141)$ MeV with an angle $θ_1\simeq (9.1\pm 0.6)^0$. A (non)-confirmation of the previous {\it minimal mixing models} requires an experimental identification of the quantum numbers of the bumps at 3150 and 3350 MeV.

hep-ph↗

arXiv2016

X, Y and Z States

Many new states in the charmonium mass region were recently discovered by BaBar, Belle, CLEO-c, CDF, D0, BESIII, LHCb and CMS Collaborations. We use the QCD Sum Rule approach to study the possible structure of some of these states.

hep-ph↗

arXiv2015

Production of the Y(4260) State in B Meson Decay

We calculate the branching ratio for the production of the meson $Y(4260)$ in the decay $B^- \to Y(4260)K^-$. We use QCD sum rules approach and we consider the $Y(4260)$ to be a mixture between charmonium and exotic tetraquark, $[\bar{c}\bar{q}][qc]$, states with $J^{PC}=1^{--}$. Using the value of the mixing angle determined previously as: $θ=(53.0\pm0.5)^\circ$, we get the branching ratio $\mathcal{B}(B\to Y(4260)K)=(1.34\pm0.47)\times10^{-6}$, which allows us to estimate an interval on the branching fraction $3.0 \times 10^{-8} < {\mathcal B}_{_Y} < 1.8 \times 10^{-6}$ in agreement with the experimental upper limit reported by Babar Collaboration.

hep-ph↗

arXiv2013

CHARM 2013: X(4260) as a Mixed Charmonium-Tetraquark State

Using the QCD sum rule approach we study the X(4260) state assuming that it can be described by a mixed charmonium-tetraquark current with $J^{PC}=1^{--}$ quantum numbers. For the mixing angle around $θ=(53.0 \pm 0.5)^0$, we obtain a value for the mass which is in good agreement with the experimental mass of the X(4260). For the decay width into the channel $X \to J/ψππ$, we find the value $Γ_{X \to J/ψππ}=(4.1 \pm 0.6)$ MeV, which is much smaller than the total experimental width $Γ= (108\pm 12)$ MeV. However, considering the experimental upper limits for the decay of the X(4260) into open charm, we conclude that we cannot rule out the possibility of describing this state as a mixed charmonium-tetraquark state.

hep-ph↗

arXiv2013

Y(3940) as a Mixed Charmonium-Molecule State

Using the QCD sum rules approach we study the mass and decay width of the channel $J/ψ+ ω$ for the $Y(3940)$ state. We assume that it can be described by a mixed charmonium-molecule scalar state, $(χ_{c0})-(D^\ast D^\ast)$ current, with $J^{PC} = 0^{++}$ quantum numbers. For the mixing angle $(76.0 \pm 5.0)^0$, we obtain the value $M = (3.95 \pm 0.11)$ GeV for the mass, which is in good agreement with the experimental mass of the $Y(3940)$ state. For the decay width into the channel $Y \rightarrow J/ψ+ ω$, we find the value $Γ_Y = (1.7 \pm 0.6)$ MeV, which is also compatible with the experimental data. We thus conclude that the present description of the $Y(3940)$ as a mixed charmonium-molecule state is a possible scenario to explain the structure of this state.

hep-ph↗

arXiv2013

QCD Sum Rule Study for a Possible Charmed Pentaquark Θc(3250)

We use QCD sum rules to study the possible existence of a Θc(3250) charmed pentaquark. We consider the contributions of condensates up to dimension-10 and work at leading order in α_s. We obtain m(Θc) = (3.21 +/- 0.13) GeV, compatible with the mass of the structure seen by BaBar Collaboration in the decay channel B- -> p- Σc++ pi- pi-. The proposed state is compatible with a previous proposed pentaquark state in the anti-charmed sector.

hep-ph↗

arXiv2012

1-- and 0++ Four-Quarks and Molecules from QCD Spectral Sum Rules

We estimate the masses of the 1-- heavy four-quark and molecule states by combining exponential Laplace (LSR) and finite energy (FESR) sum rules known perturbatively to lowest order (LO) in α_s but including non perturbative terms up to the complete dimension-six condensate contributions. We use double ratio of sum rules (DRSR) for determining the SU(3) breakings terms. The SU(3) mass-splittings of about (50 - 110) MeV and the ones of about (250 - 300) MeV between the lowest ground states and their 1st radial excitations are (almost) heavy-flavour independent. The mass predictions summarized in Table 2 are compared with the ones in the literature (when available) and with the three Yc(4260, 4360, 4660) and Yb(10890) 1-- experimental candidates. We conclude that the lowest observed state cannot be a pure 1-- four-quark nor a pure molecule but may result from their mixings. We extend the above analyzes to the 0++ four-quark and molecule states which are about (0.5-1.0) GeV heavier than the corresponding 1-- states, while the splittings between the 0++ lowest ground state and the 1st radial excitation is about (300-500) MeV. We complete the analysis by estimating the decay constants of the 1-- and 0++ four-quark states. Our predictions can be tested using some alternative non-perturbative approaches or/and at LHCb or some other hadron factories.

hep-ph↗

arXiv2012

Y(4260) as a mixed charmonium-tetraquark state

Using the QCD sum rule approach we study the Y(4260) state assuming that it can be described by a mixed charmonium-tetraquark current with $J^{PC}=1^{--}$ quantum numbers. For the mixing angle around $θ\approx (53.0\pm 0.5)^{0}$, we obtain a value for the mass which is in good agreement with the experimental mass of the Y(4260). However, for the decay width we find the value $\Ga_Y \approx (1.0\pm 0.2)$ MeV which is not compatible with the experimental value $\Ga \approx (88\pm 23)$ MeV. Therefore, we conclude that, although we can explain the mass of the Y(4260), this state cannot be described as a mixed charmonium-tetraquark state since, with this assumption, we can not explain its decay width.

hep-ph↗