Wed·Sep 22, 2021Wednesday·September 22, 2021

1. 01*

   Approaching nuclear interactions with lattice QCD

   Marc Illa🇪🇸

   Nuclei make up the majority of the visible matter in the Universe; obtaining a first principles description of the nuclear properties and interactions between nuclei directly from the underlying theory of the strong interaction, Quantum Chromodynamics (QCD), is one of the main goals of the nuclear physics community. Although the theory was established nearly fifty years ago, the complexities of QCD at low energies precludes analytical solutions of the simplest hadronic systems, let alone the features of the nuclear forces. In this thesis we follow the lattice QCD approach, according to which QCD is solved non-perturbatively in a discretized space-time via large-scale numerical calculations. Specifically, the interactions between two octet baryons, with strangeness ranging from 0 to -4, are studied at low energies with larger-than-physical quark masses, and the low-energy coefficients in pionless effective field thepry relevant for two-baryon interactions, including those responsible for SU(3) flavor-symmetry breaking, are constrained.

   hep-latnucl-th1 citation
2. 02*

   Funny business from the large $N_c$ finite temperature crossover

   Thomas DeGrand🇺🇸

   It is well known that the deconfinement transition temperature for $SU(N_c)$ gauge theory is almost independent of $N_c$, and the transition is first order for $N_c\ge 3$. In the real world ($N_c=3$, light quarks) it is a crossover located far away from the pure gauge value. What happens to the transition temperature at fixed fermion mass if the number of fermion flavors is held constant ($N_f=2$) and $N_c$ is varied? There are multiple plausible stories, only one of which appears to be true when the systems are simulated on the lattice. I describe the physics issues which surround the question and my lattice - based answer to it.

   hep-latnucl-thPoS(2022)·1 citation
3. 03*

   Radiative ${\Xi }_b^{-}\to {\Xi }^{-}\gamma$ decay

   A. R. Olamaei🇮🇷 · K. Azizi🇮🇷

   Recently, the LHCb Collaboration performed first search for the rare radiative ${\Xi }_b^{-}\to {\Xi }^{-}\gamma$ decay and put an upper limit, $\mathcal{B}({\Xi }_b^{-}\to {\Xi }^{-}\gamma )<1.3\times 10^{-4}$, on its branching ratio. The measurement agrees well with existing theory prediction using SU(3) flavor symmetry method, but shows a slight tension with the previous prediction from light-cone sum rules. Inspired by this, we investigate this decay as well as other radiative decays of ${\Xi }_b^{0(-)}({\Xi }_b^{{}^{\prime }-})$ to ${\Xi }^{0(-)}$ and ${\Sigma }^{0(-)}$ baryons using the form factors calculated from light-cone QCD sum rules in full theory. we obtain $\mathcal{B}({\Xi }_b^{-}\to {\Xi }^{-}\gamma )=1.08_{-0.49}^{+0.63}\times 10^{-5}$, which lies below the upper limit set by LHCb and is consistent with flavor-symmetry driven prediction. Our predictions on other channels may be checked in experiment and by other phenomenological approaches.

   ↳ hep-phhep-exhep-latEPJC(2022)·6 citations
4. 04*

   Dilaton in scalar QFT: a no-go theorem in $4-\epsilon$ and $3-\epsilon$ dimensions

   Daniel Nogradi🇭🇺 · Balint Ozsvath🇭🇺

   Spontaneous scale invariance breaking and the associated Goldstone boson, the dilaton, is investigated in renormalizable, unitary, interacting non-supersymmetric scalar field theories in $4-\epsilon$ dimensions. At leading order it is possible to construct models which give rise to spontaneous scale invariance breaking classically and indeed a massless dilaton can be identified. Beyond leading order, in order to have no anomalous scale symmetry breaking in QFT, the models need to be defined at a Wilson-Fisher fixed point with exact conformal symmetry. It is shown that this requirement on the couplings is incompatible with having the type of flat direction which would be necessary for an exactly massless dilaton. As a result spontaneous scale symmetry breaking and an exactly massless dilaton can not occur in renormalizable, unitary $4-\epsilon$ dimensional scalar QFT. The arguments apply to ${\varphi }^6$ theory in $3-\epsilon$ dimensions as well.

   ↳ hep-thhep-latSciPost Phys.(2022)·5 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.