Making use of a recently proposed formalism, we analyze the composite nature of the Pc(4450) resonance observed by LHCb. We show that the present data suggest that this state is almost entirely made ...of a χc1 and a proton, due to the close proximity to this threshold. This also suppresses the decay modes into other, lighter channels, in our study represented by J/Ψp. We further argue that this is very similar to the case of the scalar meson f0(980) which is located closely to the KK¯ threshold and has a suppressed decay into the lighter ππ channel.
Three hidden-charm pentaquark Pc states, Pc(4312), Pc(4440), and Pc(4457) were revealed in the Λb0→J/ψpK− process measured by LHCb using both run I and run II data. Their nature is under lively ...discussion, and their quantum numbers have not been determined. We analyze the J/ψp invariant mass distributions under the assumption that the crossed-channel effects provide a smooth background. For the first time, such an analysis is performed employing a coupled-channel formalism with the scattering potential involving both one-pion exchange as well as short-range operators constrained by heavy quark spin symmetry. We find that the data can be well described in the hadronic molecular picture, which predicts seven Σc(*)D¯(*) molecular states in two spin multiplets, such that the Pc(4312) is mainly a ΣcD¯ bound state with JP=1/2−, while Pc(4440) and Pc(4457) are ΣcD¯* bound states with quantum numbers 3/2− and 1/2−, respectively. We also show that there is evidence for a narrow Σc*D¯ bound state in the data which we call Pc(4380), different from the broad one reported by LHCb in 2015. With this state included, all predicted ΣcD¯, Σc*D¯, and ΣcD¯* hadronic molecules are seen in the data, while the missing three Σc*D¯* states are expected to be found in future runs of the LHC or in photoproduction experiments.
A
bstract
We report on the calculation of the CP-violating form factor
F
3
and the corresponding electric dipole moment for charmed baryons in the spin-1/2 sector generated by the QCD
θ
-term. We ...work in the framework of covariant baryon chiral perturbation theory within the extended-on-mass-shell renormalization scheme up to next-to-leading order in the chiral expansion.
A
bstract
The measurements of
V
us
in leptonic (
K
μ
2
) and semileptonic (
K
l
3
) kaon decays exhibit a 3
σ
disagreement, which could originate either from physics beyond the Standard Model or some ...large unidentified Standard Model systematic effects. Clarifying this issue requires a careful examination of all existing Standard Model inputs. Making use of a newly-proposed computational framework and the most recent lattice QCD results, we perform a comprehensive re-analysis of the electroweak radiative corrections to the
K
e
3
decay rates that achieves an unprecedented level of precision of 10
−
4
, which improves the current best results by almost an order of magnitude. No large systematic effects are found, which suggests that the electroweak radiative corrections should be removed from the “list of culprits” responsible for the
K
μ
2
–
K
l
3
discrepancy.
A
bstract
We derive the axion-nucleon interaction Lagrangian in heavy baryon chiral perturbation theory up to next-to-next-to-leading order. The effective axion-nucleon coupling is calculated to a ...few percent accuracy.
The in-medium properties of a hyperon–nucleon potential, derived within chiral effective field theory and fitted to ΛN and ΣN scattering data, are investigated. Results for the single-particle ...potentials of the Λ and Σ hyperons in nuclear matter are reported, based on a conventional G-matrix calculation. The Σ-nuclear potential is found to be repulsive, in agreement with phenomenological information. A weak Λ-nuclear spin–orbit interaction can be achieved by an appropriate adjustment of a low-energy constant corresponding to an antisymmetric ΛN–ΣN spin–orbit interaction that arises at next-to-leading order in the effective field theory approach.
Stimulated by recent indications that the binding energy of the hypertriton could be significantly larger than so far assumed, requirements of a more strongly bound HΛ3 state for the hyperon-nucleon ...interaction and consequences for the binding energies of A=4,5 and 7 hypernuclei are investigated. As basis, a YN potential derived at next-to-leading order in chiral effective field theory is employed. Faddeev and Yakubovsky equations are solved to obtain the corresponding 3- and 4-body binding energies, respectively, and the Jacobi no-core shell model is used for Λ5He and Λ7Li. It is found that the spin-singlet Λp interaction would have to be much more attractive which can be, however, accommodated within the bounds set by the available Λp scattering data. The binding energies of the HeΛ4 hypernucleus are predicted to be closer to the empirical values than for YN interactions that produce a more weakly bound HΛ3. The quality of the description of the separation energy and excitation spectrum for Λ7Li remains essentially unchanged.
Ab initio calculation of the Hoyle state Epelbaum, Evgeny; Krebs, Hermann; Lee, Dean ...
Physical review letters,
2011-May-13, Letnik:
106, Številka:
19
Journal Article
Recenzirano
Odprti dostop
The Hoyle state plays a crucial role in the helium burning of stars heavier than our Sun and in the production of carbon and other elements necessary for life. This excited state of the carbon-12 ...nucleus was postulated by Hoyle as a necessary ingredient for the fusion of three alpha particles to produce carbon at stellar temperatures. Although the Hoyle state was seen experimentally more than a half century ago nuclear theorists have not yet uncovered the nature of this state from first principles. In this Letter we report the first ab initio calculation of the low-lying states of carbon-12 using supercomputer lattice simulations and a theoretical framework known as effective field theory. In addition to the ground state and excited spin-2 state, we find a resonance at -85(3) MeV with all of the properties of the Hoyle state and in agreement with the experimentally observed energy.
Using dispersion theory with an improved description of the two-pion continuum based on the precise Roy-Steiner analysis of pion-nucleon scattering, we analyze recent data from electron-proton ...scattering. This allows for a high-precision determination of the electric and magnetic radius of the proton, rE=(0.838−0.004+0.005−0.003+0.004)fm and rM=(0.847±0.004±0.004)fm, where the first error refers to the fitting procedure using bootstrap and the data while the second one refers to the systematic uncertainty related to the underlying spectral functions.
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We study the nature of the hidden charm pentaquarks, i.e., the Pc4312,Pc4440 and Pc(4457), with a neural network approach in pionless effective field theory. In this framework, the ...normal χ2 fitting approach cannot distinguish the quantum numbers of the Pc(4440) and Pc(4457). In contrast to that, the neural network-based approach can discriminate them, which still cannot be seen as a proof of the spin of the states since pion exchange is not considered in the approach. In addition, we also illustrate the role of each experimental data bin of the invariant J/ψp mass distribution on the underlying physics in both neural network and fitting methods. Their similarities and differences demonstrate that neural network methods can use data information more effectively and directly. This study provides more insights about how the neural network-based approach predicts the nature of exotic states from the mass spectrum.
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