arXiv subjects

Raphael M. Albuquerque

Publications and source records attributed to Raphael M. Albuquerque.

7 recordsLinked to original sources

arXiv2026

Beyond Borel Windows: A Systematic Optimization Framework for QCD Sum Rules

We propose a systematic optimization framework for determining the sum rule window in QCD Laplace sum rules. Instead of relying primarily on fixed convergence percentages and visual plateau selection, the procedure combines an OPE entropy criterion, local mass stationarity, and a correlated analysis of the Laplace parameter $τ$, the continuum threshold $t_c$, and the interpolating-current mixing angle $θ$. The normalized OPE entropy is introduced to quantify the redistribution of the QCD contributions between the perturbative and nonperturbative sectors and to delimit an initial Working Region. This domain is subsequently refined by minimizing the residual variation of the mass estimator and requiring weak sensitivity to the continuum threshold and to the current composition. As an application, we study the lowest fully charmed tetraquark state with quantum numbers $J^{PC}=2^{++}$ using a mixed diquark--antidiquark and meson--meson interpolating current. The optimization selects $θ=17.2^\circ\pm0.4^\circ$, $\sqrt{t_c}=7.08\pm0.08~\mathrm{GeV}$, and $τ=0.410\pm0.010~\mathrm{GeV}^{-2}$, leading to the mass prediction $M_{c\bar c c\bar c}^{2^{++}}=(6.32\pm0.11)~\mathrm{GeV}$. The predicted state lies in the near-threshold region of the di-$J/ψ$ spectrum and is compatible, within uncertainties, with the lowest resonant component reported by ATLAS and with the enhancement parametrized as $BW_0$ in the recent CMS publication. The proposed framework provides a reproducible way of identifying finite domains of reduced auxiliary-parameter sensitivity and of incorporating the remaining dependence into the final uncertainty.

hep-ph↗

arXiv2019

QCD Sum Rules Approach to the $X,~Y$ and $Z$ States

In the past decade, due to the experimental observation of many charmonium-like states, there has been a revival of hadron spectroscopy. In particular, the experimental observation of charged charmonium-like, $Z_c$ states, and bottomonium-like, $Z_b$ states, represents a challenge since they can not be accommodated within the naive quark model. These charged states are good candidates of either tetraquark or molecular states and their observation motivated a vigorous theoretical activity. This is a rapidly evolving field with enormous amount of new experimental information. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. The present review is written from the perspective of the QCD sum rules approach, where we present the main steps of concrete calculations and compare the results with other approaches and with experimental data.

hep-ph↗

arXiv2013

Charmonium Exotic States

In this thesis, the QCD sum rules approach has been used to study the nature of the following charmonium resonances: Y(3930), Y(4140), X(4350), Y(4260), Y(4360) and Y(4660). There is a strong evidence that these states have non-conventional (or exotic) hadronic structures since their respective masses and decay channels observed experimentally are inconsistent with expected for a conventional charmonium state. The same phenomenon occurs on the bottomonium sector, where new states like Yb(10890) and Yb(11020) observed recently could indicate the existence of new bottomonium exotic states. In this way, one verifies that the Y(4140) state could be described as a D*sD*s (0++) molecular state or even as a mixture of D*sD*s (0++) and D*D* (0++) molecular states. For the Y(3930) and X(4350) states, both cannot be described as a D*D* (0++) and D*sD*s0 (1-+), respectively. From the sum rule point of view, the Y(4660) state could be described as a ψ' f0(980) molecular state. The extension to the bottomonium sector is done in a straightforward way to demonstrate that the Υ' f0(980) molecular state is a good candidate for describing the structure of the Yb(10890) state. In the following, one estimates the mass of the exotic Bc-like molecular states using the sum rule approach, where these new exotic states would correspond to bound states of D(*) and B(*) mesons. All of these mass predictions could (or not) be checked in a near future experiments at LHC. A large study using the Double Ratio of Sum Rules approach has been evaluated for studying the heavy baryon masses in QCD. The obtained results for the unobserved heavy baryons, with one (Qqq) and two (QQq) heavy quarks will be an excellent test for the capability of the sum rule approach in predicting their masses.

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arXiv2012

Exotic B_c-like molecules in QCD Sum Rules

We use the QCD sum rules to study possible $B_c$-like molecular states. We consider isoscalar $J^P = 0^+$ and $J^P = 1^+ D^{(\ast)}B^{(\ast)}$ molecular currents. We consider the contributions of condensates up to dimension eight and we work at leading order in $α_s$ . We obtain for these states masses around 7 GeV.

hep-ph↗

arXiv2012

Exotic $1^{--}$ States in QCD Sum Rules

Using the QCD sum rules we test if the charmonium-like structure Y(4260), observed in the $J/ψππ$ invariant mass spectrum, can be described with a $J/ψf_0(980)$ molecular current with $J^{PC}=1^{--}$. We consider the contributions of condensates up to dimension six and we work at leading order in $α_s$. We keep terms which are linear in the strange quark mass $m_s$. The mass obtained for such state is $m_{Y}=(4.67\pm 0.09)$ GeV, when the vector and scalar mesons are in color singlet configurations. We conclude that the proposed current can better describe the Y(4660) state that could be interpreted as a $Ψ(2S) f_0(980)$ molecular state. We also use different $J^{PC}=1^{--}$ currents to study the recently observed $Y_b(10890)$ state. Our findings indicate that the $Y_b(10890)$ can be well described by a scalar-vector tetraquark current.

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arXiv2010

Can the X(4350) narrow structure be a $1^{-+}$ exotic state?

Using the QCD sum rules we test if the new narrow structure, the X(4350) recently observed by the Belle Collaboration, can be described as a $J^{PC}=1^{-+}$ exotic $D_s^*D_{s0}^*$ molecular state. We consider the contributions of condensates up to dimension eight, we work at leading order in $α_s$ and we keep terms which are linear in the strange quark mass $m_s$. The mass obtained for such state is $m_{D_s^*{D}_{s0}^*}=(5.05\pm 0.19)$ GeV. We also consider a molecular $1^{-+}, D^{*}{D}_0^{*}$ current and we obtain $m_{D^*{D}_0^*}=(4.92\pm 0.08)$ GeV. We conclude that it is not possible to describe the X(4350) structure as a $1^{-+} D_s^*{D}_{s0}^*$ molecular state.

hep-ph↗

arXiv2009

A QCD sum rule calculation for the Y(4140) narrow structure

We use the QCD sum rules to evaluate the mass of a possible scalar mesonic state that couples to a molecular $D_{s}^{*}\bar{D}_s^{*}$ current. We find a mass $m_{D_s^*D_s^*}=(4.14\pm 0.09)$ GeV, which is in a excellent agreement with the recently observed Y(4140) charmonium state. We consider the contributions of condensates up to dimension eight, we work at leading order in $α_s$ and we keep terms which are linear in the strange quark mass $m_s$. We also consider a molecular $D^{*}\bar{D}^{*}$ current and we obtain $m_{D^*{D}^*}=(4.13\pm 0.10)$, around 200 MeV above the mass of the Y(3930) charmonium state. We conclude that it is possible to describe the Y(4140) structure as a $D_s^*\bar{D}_s^*$ molecular state.

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