[en] The available experimental measurements for g_bb-bar and g_cc-bar are reviewed, including some very recent results. The measurements are combined having particular care in the cross-correlations between the two quantities. The combined values can be used to rescale the central value and the error for R_b

[en] We report on some properties of the newly observed charged hidden-charmed open strange Z${}_{cs}$(3985)${}^{-<!--\; ???\; -->}$ state by BESIII Collaboration. Assigning the quantum numbers J${}^P$ = 1${}^{+}$ and the quark composition $c\stackrel{¯<!--\; ??\; -->}{c}s\stackrel{¯<!--\; ??\; -->}{u}$ and considering it as the strange partner of the famous Z${}_c$(3900) state, we estimate the mass of the Z${}_{cs}$(3985)${}^{-<!--\; ???\; -->}$ resonance in vacuum and compare it with the experimental data. We also investigate its mass, current coupling and vector-self energy in a medium with finite density. Our result on the mass in vacuum agrees well with the experimental data. We estimate the mass and current coupling of the b-partner of this state, Z${}_{bs}$, in the vacuum as well. For its mass we get m${}_{Z_{bs}}$ = 10732${}_{-<!--\; ???\; -->46}^{+97}$ MeV, which may be checked via other nonperturbative approaches as well as future experiments. We present the dependence of the spectroscopic parameters of Z${}_{cs}$(3985)${}^{-<!--\; ???\; -->}$ state on density and observe that these parameters are linearly changed with increasing in the density.

[en] Short communication

[en] We introduce the hypothesis that diquarks and antidiquarks in tetraquarks are separated by a potential barrier. We show that this notion can answer satisfactorily long standing questions challenging the diquark–antidiquark model of exotic resonances. The tetraquark description of X and Z resonances is shown to be compatible with present limits on the non-observation of charged partners $X^{\pm }$, of the $X(3872)$ and the absence of a hyperfine splitting between two different neutral states. In the same picture, $Z_c$ and $Z_b$ particles are expected to form complete isospin triplets plus singlets. It is also explained why the decay rate into final states including quarkonia are suppressed with respect to those having open charm/beauty states.

[en] The rate of gluon splitting into cc-bar pairs in hadronic Z decays is measured using the data sample collected by ALEPH from 1991 to 1995. The selection is based on the identification of leptons (electrons and muons) originating from semileptonic charm decays, and on the topological properties of signal events. The result derived from the selected sample is g_cc-bar=(3.26±0.23(stat)±0.42(syst))%

[en] From a total of 408,000 hadronic events, measured by the L3 detector during both the 1990 and 1991 running periods at LEP, a search for the Minimum Standard Model Higgs has been made in the channel Z⁰ → Higgs + Z* with Z* → v bar v. Cuts for selecting the Higgs events are decided based on the studies of about 700,000 Monte Carlo events samples. The uncertainty in the selection efficiency has been intensively studied. Detection efficiency for a 50 GeV Higgs reaches 59% with no event surviving from the entire real and simulated data sample. From these data, the lower limit for the Minimum Standard Model Higgs is found to be 50.0 GeV at the 95% confidence level. Together with all the other Higgs search channels at the L3 detector, a lower mass limit of the Minimum Standard Model Higgs has been found to be 52 GeV at 95% confidence level

[en] It is demonstrated that recently announced strong bound on magnetic moment of the τ-neutrinos μ_ντ cannot be justified. It is concluded that the use of SU(2)_LxU(1)_Y gauge invariant operators do not improve the bound on μ_ντ in contrast to what is claimed. The calculations reproduce and confirm the previous bound found by L3 collaboration from analysis of e⁺e^- annihilation at the Z resonance

[en] We consider a U(1)${}_{B-<!--\; ???\; -->L}$ model with a Z${}^{\mathrm{\prime <!--\; ???\; -->}}$ portal Dirac fermion dark matter (DM) $\mathrm{\chi <!--\; ??\; -->}$ of low mass which couples very weakly to the B - L gauge boson Z${}^{\mathrm{\prime <!--\; ???\; -->}}$. An arbitrary B - L charge Q $\ne <!--\; ???\; -->$ ±1, ±3 of the DM $\mathrm{\chi <!--\; ??\; -->}$ ensures its stability. Motivated by the sensitivity reach of forthcoming "Lifetime Frontier" experiments, we focus on the Z${}^{\mathrm{\prime <!--\; ???\; -->}}$ mass, m${}_{Z^{\mathrm{\prime <!--\; ???\; -->}}}$, in the sub-GeV to few GeV range. To evaluate the DM relic abundance, we examine both the freeze-out and freeze-in DM scenarios. For the freeze-out scenario, we show that the observed DM abundance is reproduced near the Z${}^{\mathrm{\prime <!--\; ???\; -->}}$ resonance, m${}_{\mathrm{\chi <!--\; ??\; -->}}$$\simeq <!--\; ???\; -->$ m${}_{Z^{\mathrm{\prime <!--\; ???\; -->}}}$/2, where m${}_{\mathrm{\chi <!--\; ??\; -->}}$ is the DM mass. For the freeze-in scenario, we focus on m${}_{\mathrm{\chi <!--\; ??\; -->}}$$\ll <!--\; ???\; -->$ m${}_{Z^{\mathrm{\prime <!--\; ???\; -->}}}$. We show that for a fixed value of m${}_{Z^{\mathrm{\prime <!--\; ???\; -->}}}$, g${}_{BL}$ values roughly scale as 1/Q to reproduce the observed DM abundance. For various Q values in the range between 10${}^{-<!--\; ???\; -->6}$ and 10${}^2$, we show that the gauge coupling values g${}_{BL}$ needed to reproduce the observed DM abundance lie in the search reach of future planned and/or proposed experiments such as FASER, Belle-II, LDMX, and SHiP. In the freeze-in case, the Q values to realize observable g${}_{BL}$ values are found to be much smaller than that in the freeze-out case.

[en] The dependence of the Z-resonance shape on the location of the threshold of the NN-bar production (N is the fourth-generation neutrino) is analyzed. The bounds on the existence of the fourth generation are derived from the comparison of the theoretical expression for the Z lineshape with the experimental data. The fourth generation is excluded at 95% C.L. for m_N < 46.7 ± 0.2 GeV

[en] In the context of topcolor-assisted technicolor (TC2) models, we examine the flavor changing (FC) Z decay Z→bs-bar(b-bars) and calculate the contributions of the new particles predicted by TC2 models to the branching ratio Br(Z→bs-bar+b-bars). We find that the contributions mainly come from the top-pions. In most of the parameter space, the Br(Z→bs-bar+b-bars) can reach 10^-5, which may be detected in near future experiments such as Giga-Z version of the TESLA. Thus, the FC Z decay Z→bs-bar(b-bars) can be used to test TC2 models