Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSimple model for large CP violation in charm decays, B-physics anomalies, muon g-2, and Dark Matter
78
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present a minimal extension of the Standard Model that can simultaneously account for the anomalies in semi-leptonic B meson decays and the muon g-2, give large CP violation in charm decays (up to the value recently measured by LHCb), and provide thermal-relic dark matter, while evading all constraints set by other flavour observables, LHC searches, and dark matter experiments. This is achieved by introducing only four new fields: a vectorlike quark, a vectorlike lepton, and two scalar fields (a singlet and a doublet) that mix due to the electroweak symmetry breaking and provide the dark matter candidate. The singlet-doublet mixing induces chirally-enhanced dipole transitions, which are crucial for the explanation of the muon g-2 discrepancy and the large charm CP violation, and allows to achieve the observed dark matter density in wide regions of the parameter space.
rate research
Read More
In the light of the recent result of the Muon g-2 experiment and the update on the test of lepton flavour universality $R_K$ published by the LHCb collaboration, we systematically build and discuss a set of models with minimal field content that can simultaneously give: (i) a thermal Dark Matter candidate; (ii) large loop contributions to $bto sellell$ processes able to address $R_K$ and the other $B$ anomalies; (iii) a natural solution to the muon $g-2$ discrepancy through chirally-enhanced contributions.
We study the constraints of the CP violation in the muon $g-2$ preferred region of the minimal supersymmetric standard model assuming a universal slepton masses within first two generations. We present two particular scenarios where the $g-2$ anomaly is predicted within 2 $sigma$ level mainly through the chargino loop or the bino loop. We found that for both cases the electron EDM experiment already highly constrained the CP phase of the parameters: either the Arg[$mu M_1]$ or Arg[$mu M_2]$ should be smaller than $mathcal O$(2-3)$times10^{-5}$. If the muon $g-2$ anomaly is explained by the MSSM, a particular SUSY breaking mechanism is needed to guarantee the small CP phase of SUSY parameters. Otherwise, a tuning of $mathcal O(10^{-5})$ is needed to cancel the phase in a general CP violated SUSY model.
We propose simple models with a flavor-dependent global $U(1)_ell$ and a discrete $mathbb{Z}_2$ symmetries to explain the anomalies in the measured anomalous magnetic dipole moments of muon and electron, $(g-2)_{mu,e}$, while simultaneously accommodating a dark matter candidate. These new symmetries are introduced not only to avoid the dangerous lepton flavor-violating decays of charged leptons, but also to ensure the stability of the dark matter. Our models can realize the opposite-sign contributions to the muon and electron $g-2$ via one-loop diagrams involving new vector-like leptons. Under the vacuum stability and perturbative unitarity bounds as well as the constraints from the dark matter direct searches and related LHC data, we find suitable parameter space to simultaneously explain $(g-2)_{mu,e}$ and the relic density. In this parameter space, the coupling of the Higgs boson with muons can be enhanced by up to $sim 38%$ from its Standard Model value, which can be tested in future collider experiments.
We present a model of radiative neutrino masses which also resolves anomalies reported in $B$-meson decays, $R_{D^{(star)}}$ and $R_{K^{(star)}}$, as well as in muon $g-2$ measurement, $Delta a_mu$. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars $R_2$ and $S_3$. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in $R_{D^{(star)}}$, $R_{K^{(star)}}$ and $Delta a_mu$ within $1, sigma$. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out that the doubly-charged scalar contained therein can be produced in the decays of the $S_3$ LQ, which enhances its reach to 1.1 (6.2) TeV at $sqrt s=14$ TeV high-luminosity LHC ($sqrt s=100$ TeV FCC-hh). We also present flavor-dependent upper limits on the Yukawa couplings of the LQs to the first two family fermions, arising from non-resonant dilepton ($pp rightarrow ell^+ ell^-$) processes mediated by $t$-channel LQ exchange, which for 1 TeV LQ mass, are found to be in the range $(0.15 - 0.36)$. These limits preclude any explanation of $R_{D^{(star)}}$ through LQ-mediated $B$-meson decays involving $ u_e$ or $ u_mu$ in the final state. We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to $Delta a_mu$ give rise to new contributions to the SM Higgs decays to muon and tau pairs, with the modifications to the corresponding branching ratios being at (2-6)% level, which could be tested at future hadron colliders, such as HL-LHC and FCC-hh.
Model-independent techniques for CP violation searches in multi-body charm decays are discussed. Examples of recent analyses from BaBar and LHCb are used to illustrate the experimental challenges involved.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
