Ref Arxiv: 1009.2428
DOI: 10.1016/j.nuclphysbps.2010.10.068
Ref. & Cit.: NASA ADS
5 citations
Abstract:

We consider the ratios of doubly heavy baryon masses using Double Ratios of Sum Rules (DRSR), which are more accurate than the usual simple ratios used for getting hadron masses. Our results are comparable with the ones from potential models. The Xi^*_{QQ}-Xi_{QQ} splittings seem to behave like 1/M_Q and can only allow the electromagnetic decay Xi^*_{QQ} to Xi_{QQ}+gamma but not to Xi_{QQ}+ pi. Our results also show that the SU(3) mass-splittings are (almost) independent of the spin of the baryons and behave approximately like 1/M_Q, which could be understood from the QCD expressions of the corresponding two-point correlator. Our results can improved by including radiative corrections to the SU(3) breaking terms and can be tested, in the near future, at Tevatron and LHCb.

Comments: 4 pages, 3 figures, 1 table talk given by R.M. Albuquerque at QCD 10 (28th june - 2nd july 2010, Montpellier), to appear in Nucl. Phys. B (Proc. Suppl.) Journal: Nucl.Phys.Proc.Suppl.207-208:265-268,2010

Ref Arxiv: 1009.2773
DOI: 10.1016/j.physletb.2010.12.001
Ref. & Cit.: NASA ADS
28 citations
Abstract:

Using an improved "analytic K-matrix model", we reconsider the extraction of the sigma/f_0(600) and f_0(980) gamma-gamma widths from gamma-gamma to pi-pi scatterings data of Crystal Ball and Belle. Our main results are summarized in Tables 3 and 4. The averaged sigma "direct width" to gamma-gamma is 0.16(3) keV which confirms a previous result of [1] and which does neither favour a large four-quark (diquark-antidiquark) nor a molecule nor a pure \bar qq component. The "direct width" of the f_0(980) of 0.28(2) keV is much larger than the four-quark expectation but can be compatible with a \bar ss or gluonium component. We also found that the rescattering part of the amplitude is relatively large indicating an important contribution of the meson loops in the determination of the gamma-gamma total widths. This is mainly due to the large couplings of the sigma and f_0(980) to pi-pi and/or \bar KK, which can also be due to a light scalar gluonium with large OZI violating couplings but not necessary to a four-quark or molecule state. Our average results for the total (direct+rescattering) gamma-gamma widths: Gamma_sigma^{tot}= 3.08(82) keV, Gamma_{f_0}^{tot}= 0.16(1) keV} are comparable with the ones from dispersion relations and PDG values. Using the parameters from QCD spectral sum rules, we complete our analysis by showing that the production rates of unmixed scalar gluonia sigma_B(1) and G (1.5-1.6) agree with the data from J/\psi, phi radiative and D_s semi-leptonic decays.

Comments: 11 pages, 6 figures (1 more figure added in Fig 6), 4 tables : version appeared on-line in doi:10.1016/j.physletb.2010.12.001 Journal: Phys.Lett.B696:40-50,2011

Ref Arxiv: 1009.3590
DOI: 10.1016/j.nuclphysbps.2010.10.046
Ref. & Cit.: NASA ADS
3 citations
Abstract:

We extract the pole positions, hadronic and gamma-gamma widths of sigma and f_0(980, from pi-pi and gamma-gamma scattering data using an improved analytic K-matrix model. Our results favour a large gluon component for the sigma and a \bar ss or/and gluon component for the f_0(980) but neither a large four-quark nor a molecule component. Gluonium sigma_B production from J/psi, phi radiative and D_s semi-leptonic decays are also discussed.

Comments: 4 pages, 5 figures, 6 tables, talk given by X.-G. Wang at QCD 10 (25th anniversary) 28th june-2nd july 2010 (Montpellier - FR) Journal: Nucl.Phys.Proc.Suppl.207-208:177-180,2010

Ref Arxiv: 1010.1959
DOI: 10.1016/j.nuclphysbps.2010.10.078
Ref. & Cit.: NASA ADS
17 citations
Abstract:

For this exceptional 25th anniversary of the QCD-Montpellier series of conferences initiated in 85 with the name "Non-perturbative methods", we take the opportunuity to celebrate the 30 + 1 years of the discovery of the SVZ (also called ITEP, QCD or QCD spectral) sum rules by M.A. Shifman, A.I. Vainshtein and V.I. Zakahrov in 79 [1]. In this talk, I have the duty to present the status of the method. I shall (can) not enumerate the vast area of successful applications of sum rules in hadron physics but I shall focus on the historical evolution of field and its new developments. More detailed related discussions and more complete references can be found in the textbooks [2,3].

Comments: 8 pages, 1 figure, 4 tables, talk given at QCD 10 (15th international QCD-Montpellier conference) for the celebration of the 25th anniversary of the QCD series of Montpellier conference and of the 30+1 years discovery of the SVZ sum rules Journal: Nucl.Phys.Proc.Suppl.207-208:315-322,2010

Ref HAL: hal-00457346_v1
Ref Arxiv: 1002.1402
DOI: 10.1016/j.physletb.2010.03.031
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
31 citations
Abstract:

We systematically reconsider, within an improved "analytic K-matrix model", the extraction of the sigma = f_0(600) and f_0(980) masses, widths and hadronic couplings using new Ke4 = K-->pi-pi e nu_e data on pi-pi phase shift below 390 MeV and different sets of pi-pi--> pi-pi / K-K scatterings data from 400 MeV to 1.4 GeV. Our results are summarized in Tables 1, 2 and 5. In units of MeV, the complex poles are: M_sigma=452(12) - i 260(15) and M_f=981(34) -i 18(11), which are comparable with some recent high-precision determinations and with PDG values. Besides some other results, we find: |g_{sigma K+K-}|/|g_{sigma pi+pi-}|=0.37(6) which confirms a sizeable g_{sigma K+K-} coupling found earlier, and which disfavours a large pi-pi molecule or four-quark component of the sigma, while its broad pi-pi width (relative to the one of the rho-meson) cannot be explained within a \bar qq scenario. The narrow pi-pi width of the f_0(980) and the large value: |g_{f K+K-}|/|g_{f pi+pi-}|=2.59(1.34), excludes its pure (\bar uu+\bar dd) content. A significant gluonium component eventually mixed with \bar qq appears to be necessary for evading the previous difficulties.

Ref HAL: hal-00398342_v1
Ref Arxiv: 0906.4312
DOI: 10.1016/j.physletb.2009.07.060
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
69 citations
Abstract:

We elaborate on the relation between perturbative and power-like correctionsto short-distance sensitive QCD observables. We confront theoreticalexpectations with explicit perturbative calculations existing in literature. Asis expected, the quadratic correction is dual to a long perturbative series andone should use one of them but not both. However, this might be true only forvery long perturbative series, with number of terms needed in most casesexceeding by far the number of terms available. What has not been foreseen isthat the quartic corrections might also be dual to the perturbative series. Wereview possible reasons for this emerging duality. We also observe anapproximate geometric growth of the perturbative series for differentobservables evaluated in the euclidean region, signaling a simple structure ofthe series in large orders. Some phenomenological applications are discussed.The emerging values of the running light quark masses at 2 GeV, frompseudoscalar, e+e- to hadrons and tau-decay sum rules and including thequadratic corrections are: (m_u+m_d)(2)=8.7(1.3) MeV and m_s(2) = 106.2(15.4)MeV, while the one of the QCD coupling from tau-decay is: alpha_s(M_Z)=0.1192(10). These results are comparable with existing estimates.

Ref HAL: hal-00378611_v1
Ref Arxiv: 0904.3717
DOI: 10.1016/j.physletb.2010.01.011
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
40 citations
Abstract:

We directly extract (for the first time) the heavy-baryons octetmass-splittings due to SU(3) breaking using double ratios of QCD spectral sumrules(QSSR), which are less sensitive to the exact value and definition of theheavy quark mass and to the QCD continuum contributions than the simple ratioscommonly used in the current literature for determining the heavy baryonmasses. As a result, we can provide relatively accurate predictions of the Xi_Qand Omega_Q masses once the ones of the associated non-strange Lambda_Q andSigma_Q baryons are known from the data. It is remarkable to notice that theleading term controlling the mass-splittings is the ratio ss/dd of the quarkcondensate rather than the running mass m_s. The optimal choice of theinterpolating currents for the spin 1/2 baryons octet is the same as in thecase of light baryons with the mixing parameter b=-1/5 and confirms the firstQSSR results obtained in [1-3] for the non-strange Lambda_Q and Sigma_Qbaryons.