High Energy Physics - Phenomenology (hep-ph)

Abstract: The gauge coupling unification is investigated at the classical level under the assumptions that the gauge symmetry breaking chain is $E_8\to E_7\times U_1 \to E_6\times U_1 \to SO_{10}\times U_1 \to SU_5 \times U_1 \to SU_3 \times SU_2 \times U_1$ and only components of the representations 248 of $E_8$ can acquire vacuum expectation values. We demonstrate that there are several options for the relations between the gauge couplings of the resulting theory, but the only symmetry breaking pattern corresponds to $\alpha_3=\alpha_2$ and $\sin^2\theta_W=3/8$. Moreover, only for this option the particle content of the resulting theory includes all MSSM superfields. It is also noted that this symmetry breaking pattern corresponds to the case when all representation which acquire vacuum expectation values have the minimal absolute values of the relevant $U_1$ charges.

Abstract: The discovery of the Higgs particle has yielded a specific value for the mass of the Higgs boson, which, depending on some technical details in the calculation of the $\overline{\mathrm{MS}}$ parameters (relevant for the high energy range) from the physical parameters (measured in low energy range), allows the Standard Model (SM) to hold up to the Planck scale about $\Lambda_{\rm Pl} \sim 10^{19}~{\rm GeV}$. One then has the possibility that the Higgs boson not only provides mass for all SM-particles but very likely also has supplied dark energy that inflated the young universe shortly after the Big Bang. The SM Higgs boson is a natural candidate for the Inflaton, and the Higgs boson decays are able to reheat the universe after inflation. I argue that the structures of the SM evolve naturally from a Planck cutoff medium (ether) and thus find their explanation. That the SM is an emergent structure is also strongly supported by Veltman's derivation of the SM from some general principles, which we can understand as the result of a low-energy expansion. I emphasize the role of the hierarchy problem and the problem of the cosmological constant as causal for the Higgs inflation scenario. After the discovery of the Higgs boson at 125 GeV, and considering the absence of beyond the SM particles at the LHC, a new view on the SM of particle physics and its role in early cosmology has become indispensable. Very likely, the spectacular Higgs discovery turned out to have completed the SM in an unexpected way, revealing it as an inescapable emergence which shapes the early universe.

Abstract: The Witten effect implies the presence of electric charge of magnetic monople and possible relationship between axion and dyon. The axion-dyon dynamics can be reliably built based on the quantum electromagnetodynamics (QEMD) which was developed by Schwinger and Zwanziger in 1960's. A generic low-energy axion-photon effective field theory can also be realized in the language of ``generalized symmetries'' with higher-form symmetries and background gauge fields. In this work, we implement the quantum calculation of axion-single photon transition rate inside a homogeneous electromagnetic field in terms of the new axion interaction Hamiltonian in QEMD. This quantum calculation can clearly imply the enhancement of conversion rate through resonant cavity in axion haloscope experiments. We also show the promising potentials on the cavity search of new axion-photon couplings in QEMD.

Abstract: We study the $Z_{cs}(3985)$ and $Z_{cs}(4000)$ exotic states in the decays of $\Lambda_b$ baryons through a molecular scenario. In the final state interaction, the $\Lambda_b\to \Lambda_c D_s^{(*)-}$ decays are followed by the $\Lambda_c D_s^{(*)-}$ to $Z^-_{cs}p$ rescatterings via exchange of a $D^{(*)}$ meson. We predict a branching fraction of $(3.1^{+1.4}_{-2.6})\times 10^{-4}$ for $\Lambda_b\to Z^-_{cs}p$, which can be measured in the $\Lambda_b\to J/\psi K^{(*)-}p$ decay. This study provides insights into the nature of exotic hadrons and their production mechanisms, and guides future experimental searches for the $Z_{cs}(3985)$ and $Z_{cs}(4000)$.

Abstract: We investigate the twelve-dimensional gauge-Higgs unification models with an eight-dimensional coset space. For each model, we apply the coset space dimensional reduction procedure and examine the particle contents of the resulting four-dimensional theory. Then, some twelve-dimensional SO(18) gauge theories lead to models of the SO(10)\times U(1) grand unified theory in four dimensions, where fermions of the Standard Model appear in multiple generations along with scalars that may break the electroweak symmetry. The representations of the obtained scalars and fermions are summarized.

Abstract: We investigate the quality of the extrapolation procedure employed in Ref. [1] to extract the crossover line at real chemical potential from lattice data at imaginary potential. To this end we employ a functional approach that does not suffer from the sign problem. We utilize a well-studied combination of lattice Yang--Mills theory with a truncated set of Dyson--Schwinger equations in Landau gauge for $2 + 1$ quark flavors. This system predicts a critical endpoint at moderate temperatures and rather large (real) chemical potential with a curvature comparable to recent lattice extrapolations. We determine the light quark condensate and chiral susceptibility at imaginary chemical potentials and perform an analytic continuation along the lines described in [1]. We find that the analytically continued crossover line agrees very well (within one percent) with the explicitly calculated one for chemical potentials up to about 80 % of the one of the critical end point. The method breaks down in the region where the chiral susceptibility as a function of the condensate cannot any longer be well described by a polynomial.

Abstract: The study of $J/\psi$ photoproduction at low energies has consequences for the understanding of multiple aspects of nonperturbative QCD, ranging from mechanical properties of the proton, to the binding inside nuclei, and the existence of hidden-charm pentaquarks. Factorization of the photon-$c \bar c$ and nucleon dynamics or Vector Meson Dominance are often invoked to justify these studies. Alternatively, open charm intermediate states have been proposed as the dominant mechanism underlying $J/\psi$ photoproduction. As the latter violates this factorization, it is important to estimate the relevance of such contributions. We analyse the latest differential and integrated photoproduction cross sections from the GlueX and $J/\psi$-007 experiments. We show that the data can be adequately described by a small number of partial waves, which we parameterize with generic models enforcing low-energy unitarity. The results suggest a nonnegligible contribution from open charm intermediate states. Furthermore, most of the models present an elastic scattering length incompatible with previous extractions based on Vector Meson Dominance, and thus call into question its applicability to heavy mesons. Our results indicate a wide array of physics possibilities that are compatible with present data and need to be disentangled.

Abstract: The matrix elements of the electromagnetic current and the energy-momentum tensor for sharply localized states of spin-1 systems are considered. Their interpretation as local spatial densities of various characteristics of the considered system is discussed.