Discovery potentials of double-charm tetraquarks

In this study, we investigate the discovery potential of double-charm tetraquarks $T^{{cc}}_{[bar{q}bar{q}]}$. We find that their production cross sections at the LHCb with $sqrt{s} = 13$ TeV reach $mathcal{O}(10^4)$ pb, which indicates that the LHCb has collected $mathcal{O}(10^8)$ such particles. Through the decay channels of $T^{{cc}}_{[bar{u}bar{d}]}to D^{+}K^{-}pi^{+}$ or $D^0D^+gamma$ (if stable) or $T^{{cc}}_{[bar{u}bar{d}]}to D^0D^{*+}to D^0D^0pi^+$ (if unstable), it is highly expected that they get discovered at the LHCb in the near future. We also discuss the productions and decays of the double-charm tetraquarks at future Tera-$Z$ factories.

Charm CPV: observation and prospects

An overview of the recent first observation of CP violation in the Charm sector by the LHCb collaboration. Selection of theoretical models explaining this measurement is reviewed. Finally, experimental prospects for future measurements are discussed.

Heavy neutrino searches at future $Z$-factories

We analyze the capacity of future $Z$-factories to search for heavy neutrinos with their mass from 10 to 85 GeV. The heavy neutrinos $N$ are considered to be produced via the process $e^+e^-to Zto u N$ and to decay into an electron or muon and two jets. By means of Monte Carlo simulation of such signal events and the Standard Model background events, we obtain the upper bounds on the cross sections $sigma(e^+e^-to u Nto uell jj)$ given by the $Z$-factories with integrated luminosities of 0.1, 1 and 10 ab$^{-1}$ if no signal events are observed. Under the assumption of a minimal extension of the Standard Model in the neutrino sector, we also present the corresponding constraints on the mixing parameters of the heavy neutrinos with the Standard Model leptons, and find they are improved by at least one order compared to current experimental constraints.

Summary of WG7 at CKM 2018: Mixing and $CP$ violation in the $D$ system: $x_D$, $y_D$, $|q/p|_D$, $phi_D$, and direct $CP$ violation in $D$ decays

The 10$^{rm th}$ International Workshop on the CKM Unitary Triangle took place at the University of Heidelberg on September 17$^{rm th}$-21$^{rm st}$, 2018. In this write-up, we summarize the material discussed at the workshop by the Working Group 7, which focused on latest experimental results and theoretical developments in the study of mixing and $CP$ violation in the neutral $D$ system, and of $CP$ violation and decay properties of other charm mesons and baryons.