Du, M. L., Baru, V., Guo, F. K., Hanhart, C., Meissner, U. G., Oller, J. A., et al. (2021). Revisiting the nature of the P-c pentaquarks. J. High Energy Phys., 08(8), 157–50pp.
Abstract: The nature of the three narrow hidden-charm pentaquark P-c states, i.e., P-c (4312), P-c (4440) and P-c (4457), is under intense discussion since their discovery from the updated analysis of the process Lambda(0)(b) -> I ) J/psi pK(-) by LHCb. In this work we extend our previous coupled-channel approach [Phys. Rev. Lett. 124, 072001 (2020)], in which the Pc states are treated as Sigma(()(c)*()) (D) over bar (()*()) molecules, by including the Lambda(c)(D) over bar (()*()) and eta(c)p as explicit inelastic channels in addition to the J/psi p, as required by unitarity and heavy quark spin symmetry (HQSS), respectively. Since inelastic parameters are very badly constrained by the current data, three calculation schemes are considered: (a) scheme I with pure contact interactions between the elastic, i.e., Sigma(()(c)*()) (D) over bar (()*()), and inelastic channels and without the Lambda(c)(D) over bar (()*()) interactions, (b) scheme II, where the one-pion exchange (OPE) is added to scheme I, and (c) scheme III, where the Lambda(c)(D) over bar (()*()) interactions are included in addition. It is shown that to obtain cutoff independent results, OPE in the multichannel system is to be supplemented with S-wave-to-D-wave mixing contact terms. As a result, in line with our previous analysis, we demonstrate that the experimental data for the J/psi p invariant mass distribution are consistent with the interpretation of the P-c(4312) and P-c(4440)/P-c(4457) as Sigma(c)(D) over bar and Sigma(c)(D) over bar* hadronic molecules, respectively, and that the data show clear evidence for a new narrow state, P-c(4380), identified as a Sigma(c)*(D) over bar molecule, which should exist as a consequence of HQSS. While two statistically equally good solutions are found in scheme I, only one of these solutions with the quantum numbers of the P-c (4440) and P-c (4457) being J(P) = 3/2(-) and 1/2(-), respectively, survives the requirement of regulator independence once the OPE is included. Moreover, we predict the line shapes in the elastic and inelastic channels and demonstrate that those related to the P-c (4440) and the P-c (4457) in the Sigma(()(c)*())<(D)over ( )anf eta(c)p mass distributions from Lambda(0)(b) ->( )Sigma(()(c)*()) (D) over barK(-) and Lambda(0)(b) -> eta(c)pK(-) will shed light on the quantum numbers of those states, once the data are available. We also investigate possible pentaquark signals in the Lambda(c)(D) over bar (()*()) final states.
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Aguilar, A. C., Binosi, D., & Papavassiliou, J. (2010). QCD effective charges from lattice data. J. High Energy Phys., 07(7), 002–24pp.
Abstract: We use recent lattice data on the gluon and ghost propagators, as well as the Kugo-Ojima function, in order to extract the non-perturbative behavior of two particular definitions of the QCD effective charge, one based on the pinch technique construction, and one obtained from the standard ghost-gluon vertex. The construction relies crucially on the definition of two dimensionful quantities, which are invariant under the renormalization group, and are built out of very particular combinations of the aforementioned Green's functions. The main non-perturbative feature of both effective charges, encoded in the infrared finiteness of the gluon propagator and ghost dressing function used in their definition, is the freezing at a common finite (non-vanishing) value, in agreement with a plethora of theoretical and phenomenological expectations. We discuss the sizable discrepancy between the freezing values obtained from the present lattice analysis and the corresponding estimates derived from several phenomenological studies, and attribute its origin to the difference in the gauges employed. A particular toy calculation suggests that the modifications induced to the non-perturbative gluon propagator by the gauge choice may indeed account for the observed deviation of the freezing values.
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Deak, M. (2013). Estimation of saturation and coherence effects in the KGBJS equation – a non-linear CCFM equation. J. High Energy Phys., 07(7), 087–18pp.
Abstract: We solve the modified non-linear extension of the CCFM equation – KGBJS equation – numerically for certain initial conditions and compare the resulting dipole amplitudes with those obtained front solving the original CCFM equation and the BFKL and BK equations for the same initial conditions. We improve the low transversal momentum behaviour of the KGBJS equation by a small modification.
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Baker, M. J., Bordes, J., Dominguez, C. A., Peñarrocha, J., & Schilcher, K. (2014). B meson decay constants f(Bc), f(Bs) and f(B) from QCD sum rules. J. High Energy Phys., 07(7), 032–16pp.
Abstract: Finite energy QCD sum rules with Legendre polynomial integration kernels are used to determine the heavy meson decay constant f(Bc), and revisit f(B) and f(Bs). Results exhibit excellent stability in a wide range of values of the integration radius in the complex squared energy plane, and of the order of the Legendre polynomial. Results are f(Bc) = 528 +/- 19 MeV, f(B) = 186 +/- 14 MeV, and f(Bs) = 222 +/- 12 MeV.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Production of associated Y and open charm hadrons in pp collisions at root s=7 and 8 TeV via double parton scattering. J. High Energy Phys., 07(7), 052–36pp.
Abstract: Associated production of bottomonia and open charm hadrons in pp collisions at root s = 7 and 8 TeV is observed using data corresponding to an integrated luminosity of 3 fb(-1) accumulated with the LHCb detector. The observation of five combinations, Y(1S)D-0, Y(2S)D-0, Y(1S)D+, Y(2S)D+ and Y(1S)D (s) (+) , is reported. Production crosssections are measured for Y(1S)D-0 and Y(1S)D+ pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism.
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