Among many possibilities, solar axion has been proposed to explain the electronic recoil events excess observed by Xenon1T collaboration, although it has tension with astrophysical observations. The axion couplings, to photon $g_{agamma}$ and to elec
tron $g_{ae}$ play important roles. These couplings are related to the Peccei-Quinn (PQ) charges $X_f$ for fermions. In most of the calculations, $g_{agamma}$ is obtained by normalizing to the ratio of electromagnetic anomaly factor $E = TrX_f Q^2_f N_c$ ($N_c$ is 3 and 1 for quarks and charged leptons respectively) and QCD anomaly factor $N = TrX_q T(q)$ ($T(q)$ is quarks $SU(3)_c$ index). The broken PQ symmetry generator is used in the calculation which does not seem to extract out the components of broken generator in the axion which are eaten by the $Z$ boson. However, using the physical components of axion or the ratio of anomaly factors should obtain the same results in the DFSZ for $g_{agamma}$. When going beyond the standard DFSZ models, such as variant DFSZ models, where more Higgs doublets and fermions have different PQ charges, one may wonder if the results are different. We show that the two methods obtain the same results as expected, but the axion couplings to quarks and leptons $g_{af}$ (here f indicates one of the fermions in the SM) are more conveniently calculated in the physical axion basis. The result depends on the values of the vacuum expectation values leading to a wider parameter space for $g_{af}$ in beyond the standard DFSZ axion. We also show explicitly how flavor conserving $g_{af}$ couplings can be maintained when there are more than one Higgs doublets couple to the up and down fermion sectors in variant DFSZ models at tree level, and how flavor violating couplings can arise.
Considerable information has been obtained about neutrino mixing matrix. Present data show that in the particle data group (PDG) parameterization, the 2-3 mixing angle and the CP violating phase are consistent with $theta_{23} = pi/4$ and $delta_{PDG
} = -pi/2$, respectively. A lot of efforts have been devoted to constructing models in realizing a mixing matrix with these values. However, the particular angles and phase are parameterization convention dependent. The meaning about the specific values for mixing angle and phase needs to be clarified. Using the well known 9 independent ways of parameterizing the mixing matrix, we show in detail how the mixing angles and phase change with conventions even with the 2-3 mixing angle to be $pi/4$ and the CP violating phase to be $-pi/2$. The original Kaobayashi-Maskawa and an additional one belong to such a category. The other 6 parameterizations have mixing angles and phase very different values from those in the PDG parameterization although the physical effects are the same. Therefore one should give the specific parameterization convention when making statements about values for mixing angles and phase.
We introduce a scenario for CP-violating (CPV) dark photon interactions in the context of non-abelian kinetic mixing. Assuming an effective field theory that extends the Standard Model (SM) field content with an additional $U(1)$ gauge boson ($X$) an
d a $SU(2)_L$ triplet scalar, we show that there exist both CP-conserving and CPV dimension five operators involving these new degrees of freedom and the SM $SU(2)_L$ gauge bosons. The former yields kinetic mixing between the $X$ and the neutral $SU(2)_L$ gauge boson (yielding the dark photon), while the latter induces CPV interactions of the dark photon with the SM particles. We discuss experimental probes of these interactions using searches for permanent electric dipole moments (EDMs) and di-jet correlations in high-energy $pp$ collisions. It is found that the experimental limit on the electron EDM currently gives the strongest restriction on the CPV interaction. In principle, high energy $pp$ collisions provide a complementary probe through azimuthal angular correlations of the two forward tagging jets in vector boson fusion. In practice, observation of the associated CPV asymmetry is likely to be challenging.
We revisit the theory and phenomenology of scalar electroweak multiplet thermal dark matter. We derive the most general, renormalizable scalar potential, assuming the presence of the Standard Model Higgs doublet, $H$, and an electroweak multiplet $Ph
i$ of arbitrary SU(2$)_L$ rank and hypercharge, $Y$. We show that, in general, the $Phi$-$H$ Higgs portal interactions depend on three, rather than two independent couplings as has been previously considered in the literature. For the phenomenologically viable case of $Y=0$ multiplets, we focus on the septuplet and quintuplet cases, and consider the interplay of relic density and spin-independent direct detection cross section. We show that both the relic density and direct detection cross sections depend on a single linear combination of Higgs portal couplings, $lambda_{rm eff}$. For $lambda_{rm eff}sim mathcal{O}(1)$, present direct detection exclusion limits imply that the neutral component of a scalar electroweak multiplet would comprise a subdominant fraction of the observed DM relic density.
Analyses of heavy mesons and baryons hadronic charmless decays using the flavor SU(3) symemtry can be formulated in two different forms. One is to construct the SU(3) irreducible representation amplitude (IRA) by decomposing effective Hamiltonian, an
d the other is to draw the topological diagrams (TDA). In the flavor SU(3) limit, we study various $B/Dto PP,VP,VV$, $B_cto DP/DV$ decays, and two-body nonleptonic decays of beauty/charm baryons, and demonstrate that when all terms are included these two ways of analyzing the decay amplitudes are completely equivalent. Furthermore we clarify some confusions in drawing topological diagrams using different ways of describing beauty/charm baryons.
In certain new physics scenarios, a singly charged Higgs boson can couple to both fermions and $W^pm Z$ at tree level. We develop new strategies beyond current experimental searches using $ppto jjH^pm$, $H^pm to tb $ at the Large Hadron Collider (LHC
). With the effective $H^pm W^mp Z$ and $H^pm tb$ couplings we perform a model-independent analysis at the collision energy $sqrt{s}=13$~TeV with the integrated luminosity of $3~text{ab}^{-1}$. We derive the discovery prospects and exclusion limits for the charged Higgs boson in the mass range from 200~GeV to 1~TeV. With $|F_{WZ}|,|A_t|sim 0.5-1.0$ and $300~text{GeV}lesssim m_{H^pm}lesssim 400~text{GeV}$, we point out that a discovery significance of $5sigma$ can be achieved. The constraints and projected sensitivities are also discussed in a realistic model, i.e., the modified Georgi-Machacek model without custodial symmetry. Our proposed search would provide direct evidence for a charged Higgs boson $H^pm$ that couples to $W^pm Z$ and $tb$, which can have better sensitivity to the couplings of $H^pm W^mp Z$ and $H^pm tb$ than current searches.
In the standard model (SM), the $rho$ parameter is equal to 1 and the ratio $lambda_{WZ}$ of Higgs $to ZZ$ and Higgs $to WW$ is also equal to 1 at the tree level. When going beyond the SM with more than one types of Higgs representations these quanti
ties may be different from the SM predictions which can provide crucial information about new physics. There may also exist a certain charged Higgs $h^+$ decays into a $W^+$ and a $Z$. Imposing a custodial symmetry can force the parameter $rho$ to be equal to 1 with certain predictions for $lambda_{WZ}$ and $h^+ to W^+Z$. However, imposing $rho =1$ without custodial symmetry may have different predictions. We show how differences arise and how to use experimental data to obtain information about the underlying physics in a model with the SM plus a real and a complex $SU(2)_L$ triplets.
We consider the recent LHCb result for $B_cto J/psi tau u$ in conjunction with the existing anomalies in $R(D)$ and $R(D^star)$ within the framework of a right-handed current with enhanced couplings to the third generation. The model predicts a line
ar relation between the observables and their SM values in terms of two combinations of parameters. The strong constraints from $bto s gamma$ on $W-W^prime$ mixing effectively remove one of the combinations of parameters resulting in an approximate proportionality between all three observables and their SM values. To accommodate the current averages for $R(D)$ and $R(D^star)$, the $W^prime$ mass should be near 1 TeV, and possibly accessible to direct searches at the LHC. In this scenario we find that $R(J/psi)$ is enhanced by about 20% with respect to its SM value and about 1.5$sigma$ below the central value of the LHCb measurement. The predicted $dGamma/dq^2$ distribution for $Bto D(D^star) tau u$ is in agreement with the measurement and the model satisfies the constraint from the $B_c$ lifetime.
We study constraints and implications of the recent LHCb measurement of ${cal B}(B_s to mu^+mu^-)$ for tree-level Higgs-mediated flavor-changing neutral current (FCNC) interactions. Combined with experimental data on $B_s$ mass difference $Delta m_s$
, the $h to mu tau$, and the $h to tau^+tau^-$ decay branching ratios from the LHC, we find that the Higgs FCNC couplings are severely constrained. The allowed regions for $B_s to mu tau$, $tautau$ and $h to sb$ decays are obtained. Current data allow large CP violation in the $h to tau^+ tau^-$ decay. Consequences of the Cheng-Sher ansatz for the Higgs Yukawa couplings are discussed in some detail.
One of the interesting portals linking a dark sector and the standard model (SM) is the kinetic mixing between the SM $U(1)_Y$ field with a new dark photon $A$ from a $U(1)_{A}$ gauge interaction. Stringent limits have been obtained for the kinetic m
ixing parameter $epsilon$ through various processes. In this work, we study the possibility of searching for a dark photon interaction at a circular $e^+e^-$ collider through the process $e^+ e^-to gamma A^{prime *} to gamma mu^+mu^-$. We find that the constraint on $epsilon^2$ for dark photon mass in the few tens of GeV range, assuming that the $mu^+mu^-$ invariant mass can be measured to an accuracy of $0.5%m_{A}$, can be better than $3times 10^{-6}$ for the proposed CEPC with a ten-year running at 3$sigma$ (statistic) level, and better than $2times 10^{-6}$ for FCC-ee with even just one-year running at $sqrt{s} = 240$ GeV, better than the LHC and other facilities can do in a similar dark photon mass range. For FCC-ee, running at $sqrt{s}=160$ GeV, the constraint can be even better.
