Ref Arxiv: 1004.5333
DOI: 10.1016/j.physletb.2010.09.007
Ref. & Cit.: NASA ADS
56 citations
Résumé:

We extract (for the first time) the ratio of the gluon condensate < g^3f_{abc}G^3 >/< alpha_s G^2 > expressed in terms of the liquid instanton radius rho_c from charmonium moments sum rules by examining the effects of < alpha_s G^2 > in the determinations of both rho_c and the running MS mass m_c(m_c). Using a global analysis of selected ratios of moments at different Q^2=0, 4m_c^2 and 8m_c^2 and taking < alpha_s G^2 > from 0.06 GeV^4, where the estimate of rho_c is almost independent of < alpha_s G^2 >, we deduce: rho_c=0.98(21) GeV^{-1} which corresponds to < g^3f_{abc}G^3 > = (31+- 13) GeV^2 < alpha_s G^2 >. The value of m_c(m_c) is less affected (within the errors) by the variation of < alpha_s G^2 >, where a common solution from different moments are reached for < alpha_s G^2 > greater than 0.02 GeV^4. Using the values of < alpha_s G^2 >=0.06(2) GeV^4 from some other channels and the previous value of < g^3f_{abc}G^3 >, we deduce: m_c(m_c)=1260(18) MeV and m_b(m_b)=4173(10) MeV, where an estimate of the 4-loops contribution has been included. Our analysis indicates that the errors in the determinations of the charm quark mass without taking into account the ones of the gluon condensates have been underestimated. To that accuracy, one can deduce the running light and heavy quark masses and their ratios evaluated at M_Z, where it is remarkable to notice the approximate equalities: m_s/m_u= m_b/m_s= m_t/m_b= 51(4), which might reveal some eventual underlying novel symmetry of the quark mass matrix in some Grand Unified Theories.

Commentaires: 8 pages, 2 figures, 5 tables. Due to a bug in the program, values of m_b(m_b) in Table 5 have been changed and are in excellent agreement with the ones from Q^2-moments (arXiv:1105.2922[hep-ph]) and exponential sum rules (arXiv:1105.5070[hep-ph]) within stability criteria. These changes will be published as an erratum in PLB Journal: Phys.Lett.B693:559-566,2010

Ref Arxiv: 1105.2922
Ref. & Cit.: NASA ADS
Résumé:

We reconsider the extraction of the gluon condensates , and the MS running quark masses m_{c,b} from different M_n(Q^2) Moments and their Ratios by including PT corrections to order alpha_s^3, NPT terms up to and using stability criteria of the results versus the degree n (number of Q^2-derivative). We explicitly show that the spectral part of the lowest moment M_1(0) depends strongly (as expected) on its high-energy (continuum) contribution, which is minimized for M_{n> 3-4}(0). Using higher moments and the correlations of with and < G^4>, we obtain =(7.0+- 1.3)10^{-2} GeV^4 and =(8.8+- 5.5) GeV^2 , while our analysis favours a modified factorisation for . Using the previous results, we re-determine m_c(m_c) and find that the commonly used M_1(0) lowest moment tends to overestimate its value compared to the ones from higher moments where stable values of m_c(m_c) versus the variations of n and the continuum models are reached. These features can indicate that the quoted errors of m_{c,b} from M_1(0) may have been underestimated. Optimal results from different high-n moments converge to the accurate (artithmetic) mean values: m_c(m_c)=1261(16) MeV and m_b(m_b)=4171(14) MeV, in excellent agreement with results obtained in [1] using some judicious choices of ratios of moments.

Commentaires: 11 pages, 9 figures, 5 tables. Improved version to appear in Phys. Lett. B including a reevaluation of the different sources of the errors

Ref Arxiv: 1105.5070
Ref. & Cit.: NASA ADS
Résumé:

We test the convergence of the QCD exponential moments by including PT corrections to order \alpha_s^3 and the NP contributions up to D=8 condensates. Then, using the ratio of exponential sum rules where the QCD PT series is more convergent, we study the correlation between the gluon condensates <\alpha_s G^2> and < g^3f_{abc} G^3>. From charmonium systems and using the charm quark mass as input, we deduce:< g^3f_{abc} G^3> =(8.2+-1.0)GeV^2 <\alpha_s G^2> corresponding to < \alpha_s G^2>=(7.5+- 2.0) 10^{-2} GeV^4. Using these results for the bottomium systems, we obtain: m_b(m_b)= 4212(32) MeV, which is slightly higher but consistent within the errrors with the ones from Q^2-moments and their ratios: m_b(m_b)= 4172(12) MeV. We are tempted to consider as a final result from the sum rules approaches, the average m_b(m_b)= 4177(11) MeV of the two previous determinations.

Commentaires: 5 pages, 4 figures, 2 references added on the proofs (Phys. Lett. B in press)

Ref Arxiv: 1105.5630
Ref. & Cit.: NASA ADS
Résumé:

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.

Commentaires: revised version to appear on Phys. Lett. B

Ref HAL: hal-00609283_v1
Ref Arxiv: 1107.2472
Ref INSPIRE: 918293
DOI: 10.1007/JHEP09(2011)105
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
82 citations
Commentaires: 19 pages , 10 figures

Ref Arxiv: 1109.2420
Ref. & Cit.: NASA ADS
Résumé:

Many extensions of the Standard Model involve two Higgs doublet fields to break the electroweak symmetry, leading to the existence of three neutral and two charged Higgs particles. In particular, this is the case of the Minimal Supersymmetric extension of the Standard Model, the MSSM. A very important parameter is $\tan\beta$ defined as the ratio of the vacuum expectation value of the two Higgs doublets. In this paper we focus on the left-right asymmetry in the production of polarised top quarks in association with charged Higgs bosons at the LHC. This quantity allows for a theoretically clean determination of $\tan\beta$. In the MSSM, the asymmetry remains sensitive to the strong and electroweak radiative corrections and, thus, to the superparticle spectrum. Some possible implications of these results are discussed.

Ref Arxiv: 0
Résumé:

We study the fine tuning in the parameter space of the semi-constrained NMSSM, where most soft Susy breaking parameters are universal at the GUT scale. We discuss the dependence of the fine tuning on the soft Susy breaking parameters $M_{1/2}$ and $m_0$, and on the Higgs masses in NMSSM specific scenarios involving large singlet-doublet Higgs mixing or dominant Higgs-to-Higgs decays. Whereas these latter scenarios allow a priori for considerably less fine tuning than the constrained MSSM, the early LHC results rule out a large part of the parameter space of the semi-constrained NMSSM corresponding to low values of the fine tuning.