arXiv subjects

S. Narison

Publications and source records attributed to S. Narison.

At least 37 records · Page 2Linked to original sources

arXiv2021

Z_{c,b}-like states from QCD Laplace sum rules at NLO

We review our results on $Z_{c}$-like states[1] which we complete with the ones on $Z_{b}$-like states by using relativistic QCD Laplace Sum Rules (LSR) 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 emphasize the importance of PT radiative corrections for heavy quark sum rules in order to justify the use of the running heavy quark mass in the analysis. Our estimates are compiled in Tables 3 and 4. From our results, the observed $Z_{cs}(3983)$ state are good candidate for being ${\mathcal T}_{cs}$ tetramole (superposition of nearly degenerated molecules and tetraquark states having the same quatum numbers $J^{PC}$ and with almost the same couplings to the currents). The $Z_{cs}$ bump around 4100 MeV can be interpreted as a combination of $D^{*}_{0}D_{s1}$ and $D^{*}_{s0}D_{1}$ molecules. The physical states $Z_{cs}(4000)$ and $Z_{cs}(4220)$ found by LHCb are too low to be considered as the first radial excitations of $Z_{cs}(3983)$. For the future $Z_{b}$, $Z_{bs}$ and $Z_{bss}$, we suggest to scan the region around $(10.3 \sim 10.9)$ GeV while the 1st radial excitations are about 2.4 GeV above the ground states.

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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.

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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.

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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.

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arXiv2018

Scalar Meson Contributions to a_μfrom Hadronic Light-by-Light Scattering

Using an effective σ/f_0(500) resonance, which describes the ππ-->ππand γγ-->ππscattering data, we evaluate its contribution and the ones of the other scalar mesons to the the hadronic light-by-light (HLbL) scattering component of the anomalous magnetic moment a_μof the muon. We obtain the conservative range of values: \sum_S~a_μ^{lbl}\vert_S = -(4.51+- 4.12) 10^{-11}, which is dominated by the σ/f_0(500) contribution ( 50%~98%), and where the large error is due to the uncertainties on the parametrisation of the form factors. Considering our new result, we update the sum of the different theoretical contributions to a_μwithin the standard model, which we then compare to experiment. This comparison gives (a_μ^{\rm exp} - a_μ^{SM})= +(312.1+- 64.3) 10^{-11}, where the theoretical errors from HLbL are dominated by the scalar meson contributions.

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arXiv2018

XYZ-SU3 Breakings from Laplace Sum Rules at Higher Orders

We present new compact integrated expressions of SU3 breaking corrections to QCD spectral functions of heavy-light molecules and four-quark XYZ-like states at lowest order (LO) of perturbative (PT) QCD and up to d=8 condensates of the OPE. Including N2LO PT corrections in the chiral limit and NLO SU3 PT corrections, which we have estimated by assuming the factorization of the four-quark spectral functions, we improve previous LO results for the XYZ-like masses and decay constants from QCD spectral sum rules. Systematic errors are estimated from a geometric growth of the higher order PT corrections and from some partially known d=8 non-perturbative contributions. Our optimal results, based on stability criteria, are summarized in Tables 18 to 21 and compared with some LO results in Table 22. In most channels, the SU3 corrections on the meson masses are tiny: < 10% (resp. <3%) for the c (resp. b)-quark channel but can be large for the couplings (< 20%). Within the lowest dimension currents, most of the 0^{++} and 1^{++} states are below the physical thresholds while our predictions cannot discriminate a molecule from a four-quark state. A comparison with the masses of some experimental candidates indicates that the 0^{++} X(4500) might have a large D^*_{s0}D^*_{s0} molecule component while an interpretation of the 0^{++} candidates as four-quark ground states is not supported by our findings. The 1^{++} X(4147) and X(4273) are compatible with the D^*_{s}D_{s}, \bar D^*_{s0}D_{s1} molecules and/or with the axial-vector A_c four-quark ground state. Our results for the 0^{-\pm}, 1^{-\pm} and for different beauty states can be tested in the future data. Finally, we revisit our previous estimates [1] for the D^*_{0}D^*_{0} and D^*_{0}D_{1} and present new results for the D_1D_1.

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arXiv2018

0+ and 1+ heavy-light exotic mesons at N2LO in the chiral limit

We use QCD spectral sum rules (QSSR) and the factorization properties of molecule and four-quark currents to estimate the masses and couplings of the 0+ and 1+ molecules and four-quark at N2LO of PT QCD. We include in the OPE the contributions of non-perturbative condensates up to dimension-six. Within the Laplace sum rules approach (LSR) and in the MS-scheme, we summarize our results in Table 2, which agree within the errors with some of the observed XZ-like molecules or/and four-quark. Couplings of these states to the currents are also extracted. Our results are improvements of the LO ones in the existing literature.

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arXiv2018

XYZ - SU3 Breakings from Laplace Sum Rule at Higher Orders: Summary

This talk reviews and summarizes some of our results in [1] on XYZ- SU3 Breakings obtained from QCD Laplace Sum Rules (LSR) at next-to-next-leading order (N2LO) of perturbative (PT) theory and including next-to-leading order (NLO) SU3 breaking corrections and leading order (LO) contributions of dimensions d< (6 - 8) non-perturbative condensates. We conclude that the observed X states are good candidates for being 1^++ and 0^++ molecules states. We find that the SU3 breakings are relatively small for the masses (< 10 (resp. 3) %) for the charm (resp. bottom) channels while they are large (< 20 %) for the couplings. Like in the chiral limit case, the couplings decrease faster: 1/m_b^3/2 than 1/m_b^1/2 of HQET. Our approach cannot clearly separate ( within the errors ) some molecule states from the four-quark ones with the same quantum numbers.

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arXiv2016

XYZ-like Spectra from Laplace Sum Rule at N2LO in the Chiral Limit

We present new compact integrated expressions of QCD spectral functions of heavy-light molecules and four-quark $XYZ$-like states at lowest order (LO) of perturbative (PT) QCD and up to $d=8$ condensates of the Operator Product Expansion (OPE). Then, by including up to next-to-next leading order (N2LO) PT QCD corrections, which we have estimated by assuming the factorization of the four-quark spectral functions, we improve previous LO results from QCD spectral sum rules (QSSR), on the $XYZ$-like masses and decay constants which suffer from the ill-defined heavy quark mass. PT N3LO corrections are estimated using a geometric growth of the PT series and are included in the systematic errors. Our optimal results based on stability criteria are summarized in Tables 11 to 14 and compared, in Section 10, with experimental candidates and some LO QSSR results. We conclude that the masses of the $XZ$ observed states are compatible with (almost) pure $J^{PC}=1^{+\pm}, 0^{++}$ molecule or/and four-quark states. The ones of the $1^{-\pm}, 0^{-\pm}$ molecule / four-quark states are about 1.5 GeV above the $Y_{c,b}$ mesons experimental candidates and hadronic thresholds. We also find that the couplings of these exotics to the associated interpolating currents are weaker than that of ordinary $D,B$ mesons ($f_{DD}\approx 10^{-3}f_D$) and may behave numerically as $1/ \bar m_b^{3/2}$ (resp. $1/ \bar m_b$) for the $1^{+},0^{+}$ (resp. $1^{-}, 0^{-}$) states which can stimulate further theoretical studies of these decay constants.

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arXiv2016

Heavy-Light Exotics from QCD Laplace Sum Rules at N2LO in the chiral limit

These talks review and summarize our results in [1,2] on $XYZ$-like spectra obtained from QCD Laplace Sum Rules in the chiral limit at next-to-next-leading order (N2LO) of perturbation theory (PT) and including leading order (LO) contributions of dimensions $d\leq 6-8$ non-perturbative condensates. We conclude that the observed $XZ$ states are good candidates for $1^{+}$ and $0^+$ molecules or / and four-quark states while the predictions for $1^-$ and $0^-$ states are about 1.5 GeV above the $Y_{c,b}$ experimental candidates and hadronic thresholds. We (numerically) find that these exotic molecules couple weakly to the corresponding interpolating currents than ordinary $D,B$ heavy-light mesons while we observe that these couplings decrease faster [$1/m_b^{3/2}$ (resp. $1/m_b$) for the $1^+,0^+$ (resp. $1^-,0^-)$ states] than $1/m_b^{1/2}$. Our results do not also confirm the existence of the $X(5568)$ state in agreement with LHCb findings.

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arXiv2016

Nature of the X(5568) : a critical Laplace sum rule analysis at N2LO

We scrutinize recent QCD spectral sum rules (QSSR) results to lowest order (LO) predicting the masses of the BK molecule and (su)\bar(bd) four-quark states. We improve these results by adding NLO and N2LO corrections to the PT contributions giving a more precise meaning on the b-quark mass definition used in the analysis. We extract our optimal predictions using Laplace sum rule (LSR) within the standard stability criteria versus the changes of the external free parameters (τ-sum rule variable, t_c continuum threshold and subtraction constant μ). The smallness of the higher order PT corrections justifies (a posteriori) the LO order results + the uses of the ambiguous heavy quark mass to that order. However, our predicted spectra in the range (5173\sim 5226) MeV, summarized in Table 7, for exotic hadrons built with four different flavours (buds), do not support some previous interpretations of the D0 candidate[1], X(5568), as a pure molecule or a four-quark state. If experimentally confirmed, it could result from their mixing with an angle: sin 2θ\approx 0.15. One can also scan the region (2327~ 2444) MeV (where the D*_{s0}(2317) might be a good candidate) and the one (5173~ 5226) MeV for detecting these (cuds) and (buds) unmixed exotic hadrons (if any) via, eventually, their radiative or π+hadrons decays.

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arXiv2014

$\bar D^D^_0$ and $\bar B^B^_0 (1^--)$ molecules at N2LO from QSSR

We estimate the $\bar D^*D^*_0$ and $\bar B^*B^*_0(1^--)$ molecules masses and couplings using QCD spectral sum rules (QSSR)known perturbatively to N2LO of PT series and including the contributions of non-perturabtive condensates up to the dimension-eight. Our results improve earlier LO results obtained from QSSR in the current literature. We obtain $M_{D^*D^*_0} = 5244(228)$ MeV which is heavier than the experimental candidates Y(4260); Y(4360); Y(4660) suggesting that they cannot be pure molecule states. We predict $M_{B^*B^*_0}= 11920(159)$ MeV to be tested in B-factory experiments.

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arXiv2014

$ \bar D^D$ and $\bar B^B~(1^{++})$ molecules at N2LO from QSSR

We use QCD spectral sum rules (QSSR) and the factorization properties of molecule currents to estimate the masses and couplings of the $\bar D^*D$ and $\bar B^*B~(1^{++})$ molecules at N2LO of PT QCD. We include in the OPE the contributions of non-perturbative condensates up to dimension-eight. With the Laplace sum rules approach (LSR) and in the $\overline{MS}$-scheme, we obtain $M_{D^*D}=3738(152)$ MeV, which agrees within the errors with the newly discovered $Z_c$(3900). For the bottom channel, we find $M_{B^*B}=10687(232)$ MeV in good agreement with the observed $Z_b$(10610). Couplings of these states to the currents are also extracted. Our results are improvements of the LO ones in the existing literature.

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arXiv2014

Hadrons with Charm and Beauty

By combining potential models and QCD spectral sum rules (QSSR), we discuss the spectroscopy of the $(b\bar c)$ mesons and of the $(bcq)$, $(ccq)$ and $(bbq)$ baryons (${q}\equiv {d}$ or $s$), the decay constant and the (semi)leptonic decay modes of the $B_c$ meson. For the masses, the best predictions come from potential models and read: $M_{B_c} = (6255 \pm 20)$~MeV, $M_{B^*_c} = (6330 \pm 20)$~MeV, $M_{Λ(bcu)} = (6.93\pm 0.05)$~GeV, $M_{Ω(bcs)} = (7.00\pm 0.05)$~GeV, $M_{Ξ^*(ccu)} =(3.63\pm 0.05)$~GeV and $M_{Ξ^*(bbu)} = (10.21\pm 0.05)$~GeV. The decay constant $f_{B_c} = (2.94 \pm 0.21) f_π$ is well determined from QSSR and leads to: $Γ(B_c \rightarrow ν_ττ) = (3.0 \pm 0.4)( V_{cb}/0.037 )^2$ $\times 10^{10}$ s$^{-1}$.The uses of the vertex sum rules for the semileptonic decays of the $B_c$ show that the $t$-dependence of the form factors is much stronger than predicted by vector meson dominance. It also predicts the almost equal strength of about 0.30 $\times 10^{10}$ sec$^{-1}$ for the semileptonic rates $B_c$ into $B_s, B^*_s,η_c$ and J/$ψ$. Besides these phenomenological results, we also show explicitly how the Wilson coefficients of the $\langleα_s G^2\rangle$ and $\langle G^3\rangle$ gluon condensates already contain the full heavy quark- ($\langle\bar QQ\rangle$) and mixed- ($\langle\bar QGQ\rangle$) condensate contributions in the OPE.}

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arXiv2013

SVZ + 1/q2 expansion versus some QCD holographic Models

Considering the classical two-point correlators built from (axial)-vector, scalar \bar qq and gluonium currents, we confront results obtained using the SVZ + 1/q^2 expansion to the ones from some QCD holographic models in the Euclidian region and with negative dilaton Φ_i(z)=- |c_i^2| z^2. We conclude that the presence of the 1/q^2-term in the SVZ-expansion due to a tachyonic gluon mass appears naturally in the Minimum Soft Wall (MSW) and the Gauge/String Dual (GSD) models which can also reproduce semi-quantitatively some of the higher dimension condensate contributions appearing in the OPE. The Hard-Wall model shows a large departure from the SVZ + 1/q^2 expansion in the vector, scalar and gluonium channels due to the absence of any power corrections. The equivalence of the MSW and GSD models is manifest in the vector channel through the relation of the dilaton parameter with the tachyonic gluon mass. For approximately reproducing the phenomenological values of the dimension d=4,6 condensates, the holographic models require a tachyonic gluon mass (α_s/π)λ^2= -(0.12- 0.14) GeV^2, which is about twice the fitted phenomenological value from e^+e^- data. The relation of the inverse length parameter c_i to the tachyonic gluon mass also shows that c_i is channel dependent but not universal for a given holographic model. Using the MSW model and M_ρ=0.78 GeV as input, we predict a scalar \bar qq mass M_S=(0.95-1.10) GeV and a scalar gluonium mass M_G= (1.1- 1.3) GeV.

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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.

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arXiv2012

1-- and 0++ heavy four-quark and molecule states in QCD

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 alpha_s but including non-perturbative terms up to the complete dimension-six condensate contributions. This approach allows to fix more precisely the value of the QCD continuum threshold (often taken ad hoc) at which the optimal result is extracted. We use double ratio of sum rules (DRSR) for determining the SU(3) breakings terms. We also study the effects of the heavy quark mass definitions on these LO results. 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 4 are compared with the ones in the literature (when available) and with the three Y_c(4260,~4360,~4660) and Y_b(10890) 1^{--} experimental candidates. We conclude (to this order approximation) 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) 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 which are tiny and which exhibit a 1/M_Q behaviour. Our predictions can be further tested using some alternative non-perturbative approaches or/and at LHCb and some other hadron factories.

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arXiv2011

Relation between $T_{cc,bb}$ and $X_{c,b}$ from QCD

We have studied, using double ratio of QCD (spectral) sum rules, the ratio between the masses of $T_{cc}$ and X(3872) assuming that they are respectively described by the $D-{D}^*$ and $D-\bar{D}^*$ molecular currents. We found (within our approximation) that the masses of these two states are almost degenerate. Since the pion exchange interaction between these mesons is exactly the same, we conclude that if the observed X(3872) meson is a $D\bar{D}^*+c.c.$ molecule, then the $DD^*$ molecule should also exist with approximately the same mass. An extension of the analysis to the $b$-quark case leads to the same conclusion. We also study the SU(3) breakings for the $T^s_{QQ}/T_{QQ}$ mass ratios. Motivated by the recent Belle observation of two $Z_b$ states, we revise our determination of $X_b$ by combining results from exponential and FESR sum rules.

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