Doubly heavy baryons in Born-Oppenheimer EFT

We report on the recent progress on the computation of the doubly heavy baryon spectrum in effective field theory. The effective field theory is built upon the heavy-quark mass and adiabatic expansions. The potentials can be expressed as NRQCD Wilson loops with operator insertions. These are nonperturbative objects and so far only the one corresponding to the static potential has been computed with lattice QCD. We review the proposal for a parametrization of the potentials based in an interpolation between the shortand long-distance regimes. The long-distance description is obtained with a newly proposed Effective String Theory which coincides with the previous ones for pure gluodynamics but it is extended to contain a fermion field. We show the doubly heavy baryon spectrum with hyperfine contributions obtained using these parametrizations for the hyperfine potentials.

Study of excited $$\varvec{\varXi }$$ baryons with the $$\overline{\text{ P }}$$ANDA detector

The study of baryon excitation spectra provides insight into the inner structure of baryons. So far, most of the world-wide efforts have been directed towards $$N^*$$ N ∗ and $$\varDelta $$ Δ spectroscopy. Nevertheless, the study of the double and triple strange baryon spectrum provides independent information to the $$N^*$$ N ∗ and $$\varDelta $$ Δ spectra. The future antiproton experiment $$\overline{\text{ P }}$$ P ¯ ANDA will provide direct access to final states containing a $${\overline{\varXi }}\varXi $$ Ξ ¯ Ξ pair, for which production cross sections up to $$\mu \text{ b }$$ μ b are expected in $$\bar{\text{ p }}$$ p ¯ p reactions. With a luminosity of $$L=10^{31}$$ L = 10 31 cm$$^{-2}$$ - 2 s$$^{-1}$$ - 1 in the first phase of the experiment, the expected cross sections correspond to a production rate of $$\sim 10^6\, \text{ events }/\text{day }$$ ∼ 10 6 events / day . With a nearly $$4\pi $$ 4 π detector acceptance, $$\overline{\text{ P }}$$ P ¯ ANDA will thus be a hyperon factory. In this study, reactions of the type $$\bar{\text{ p }}$$ p ¯ p $$\rightarrow $$ → $${\overline{\varXi }}^{+}$$ Ξ ¯ + $$\varXi ^{*-}$$ Ξ ∗ - as well as $$\bar{\text{ p }}$$ p ¯ p $$\rightarrow $$ → $${\overline{\varXi }}^{*+}$$ Ξ ¯ ∗ + $$\varXi ^{-}$$ Ξ - with various decay modes are investigated. For the exclusive reconstruction of the signal events a full decay tree fit is used, resulting in reconstruction efficiencies between 3 and 5%. This allows high statistics data to be collected within a few weeks of data taking.

Gauge/gravity dual dynamics for the strongly coupled sector of composite Higgs models

A holographic model of chiral symmetry breaking is used to study the dynamics plus the meson and baryon spectrum of the underlying strong dynamics in composite Higgs models. The model is inspired by top-down D-brane constructions. We introduce this model by applying it to Nf = 2 QCD. We compute meson masses, decay constants and the nucleon mass. The spectrum is improved by including higher dimensional operators to reflect the UV physics of QCD. Moving to composite Higgs models, we impose perturbative running for the anomalous dimension of the quark condensate in a variety of theories with varying number of colors and flavours. We compare our results in detail to lattice simulations for the following theories: SU(2) gauge theory with two Dirac fundamentals; Sp(4) gauge theory with fundamental and sextet matter; and SU(4) gauge theory with fundamental and sextet quarks. In each case, the holographic results are encouraging since they are close to lattice results for masses and decay constants. Moreover, our models allow us to compute additional observables not yet computed on the lattice, to relax the quenched approximation and move to the precise fermion content of more realistic composite Higgs models not possible on the lattice. We also provide a new holographic description of the top partners including their masses and structure functions. With the addition of higher dimension operators, we show the top Yukawa coupling can be made of order one, to generate the observed top mass. Finally, we predict the spectrum for the full set of models with top partners proposed by Ferretti and Karateev.

Anatomy of spacetime and possible origins of internal symmetry and all particle quantum numbers

Not driven by observations, this paper digs into the “internal workings” of spacetime. Through logical deductions, micro dimensions appear to be uncovered, with possible SU(4) or SU(5): 1. It is thought that special relativity merely initiated the definition of spacetime, but more scales are yet to be defined. 2. In the definition of spacetime, EM (electromagnetism) played another critical role, i.e., the six circular magnetic and electric field lines (running on the six planes) cross and “define equivalencies” between the four linear scales. Without this definition, light would not be measured at the same speed in different directions. Being a gauge theory, EM defines two things: Linear scales and “equivalencies” between linear scales. 3. For any scale (and their equivalencies), there could be no or many arbitrarily assumed definitions, or a concrete definition based on relevant physics. Nature would conform with but the one based on relevant physics, because Nature itself is consisted of that relevant physics. Thus, the principle: No scale and their equivalencies are meaningful unless defined by relevant physics. 4. Then, what are those fields running (and defining equivalencies between the six “angle scales”) on the six planes of the 4D spacetime? It is believed to be the “classical” weak fields which run in solid angles (or “3D angles”) between the six planes. (The only suspicion is that this rotation does not preserve vector length, which is not a problem ultimately.) 5. If the six angle scales are drawn as six axes of a 6D superspace, then the “3D angle” rotations look like “plane angle” rotations and cause SO(6)∼SU(4) [or SO(10)∼SU(5) for 5D spacetime], which appears to match baryon spectrum without quarks. 6. Since this rotation is between “planes” of the “external” spacetime, no linear dimension is visible, yet causing P-violations. 7. Similarly, fields running in 4D and 5D angle rotations (between 3D and 4D surfaces) must also exist, which may be responsible for CP-violation and strong interactions. 8. The 5D angle rotations may be generating Baryon and Lepton numbers and hence explaining their conservation behaviors, e.g., no proton decay. 9. It can be inferred, if 3D, 4D (and 5D) angle rotation fields did not exist, the 4D (and 5D) spacetime would be warped and the four (or five) linear axes would not be perpendicular to each other. 10. EM was simplified and turned elegant “only” after redefinition of spacetime by special relativity. Likewise, weak, CP-violation and strong interactions are expected to simplify and turn as elegant as EM when 2D (plane), 3D, and 4D angle scales are defined by weak, CP-violation, and strong forces, respectively. 11. Verifications as accurate as EM are expected too. 12. Mathematically, higher angle rotations thought to be inexistent only because it does not conserve vector length. Actually, they did not vanish and their symmetries would surface in particle classifications when linear momentum is not concerned. Micro dimensions being invisible is because symmetries do not have to happen between linear axes, but can happen between 2-, 3- or 4-surfaces. These geometries together generate the complete particles spectrum.