Letters in High Energy Physics

The $\tau$ Magnetic Dipole Moment at Future Lepton Colliders

2019-04-11T12:53:33+00:00

The magnetic moment of the $\tau$ lepton is an interesting quantity that is potentially sensitive to physics beyond the Standard Model. Electroweak gauge invariance implies that a heavy new physics contribution to it takes the form of an operator which involves the Higgs boson, implying that rare Higgs decays are able to probe the same physics as $a_\tau$. We examine the prospects for rare Higgs decays at future high energy lepton (electron or muon) colliders, and find that such a project collecting a few ab$^{-1}$ would be able to advance our understanding of this physics by roughly a factor of 10 compared to the expected reach of the high luminosity LHC.

Can the symmetry breaking in the SM be determined by the "second minimum" of the Higgs potential?

2019-04-11T22:11:45+00:00

The possibility that the spontaneous symmetry breaking in the Standard Model (SM) may be generated by the Top-Higgs Yukawa interaction (which determines the so called ``second minimum" in the SM) is investigated. A former analysis about a QCD action only including the Yukawa interaction of a single quark with a scalar field is here extended. We repeat the calculation done in that study of the two loop effective action for the scalar field of the mentioned model. A correction of the former evaluation allowed to select a strong coupling $\alpha $($\mu,\Lambda_{QCD})=0.2254$ GeV at an intermediate scale $\mu=11.63$ GeV, in order to fix the minimum of the potential at a scalar mean field determining $175$ GeV for the single quark mass. Further, a scalar field mass $m=44$ GeV is evaluated, which is also of the order of the experimental Higgs mass. The work is also considering the effects of employing a running with momenta strong coupling. For this purpose, the finite part of the two loop potential contribution determined by the strong coupling, was represented as a momentum integral. Next, substituting in this integral the experimental values of the running coupling, the potential curve became very close to the one for constant coupling. This happened after simply assuming that the low momentum dependence of the coupling is "saturated" to a constant value being close to its lowest experimental value.

Scalar models of formally interacting non-standard quantum fields in Minkowski space-time

2019-04-11T12:53:34+00:00

For decades, a lot of work has been devoted to the problem of constructing a non-trivial quantum field theory in four-dimensional space-time. This letter addresses the attempts to construct an algebraic quantum field theory in the framework of non-standard theories like hyperfunction or ultra-hyperfunction quantum field theory. Model theories of formally self-coupled interacting neutral scalar fields are solved and discussed from a non-perturbative point of view.

Search for more sensitive observables to charged scalar in $B \rightarrow D^{(*)}\tau\nu_{\tau}$ decays.

2019-04-28T15:07:01+00:00

It has been known that $B \rightarrow D^{(*)} \tau \nu_{\tau}$ are good observables in the search for the charged Higgs. The recent obervation of deviation from standard-model by almost 4$\sigma$ by Babar, Belle and LHCb in $R(D^{(*)})$ revived the interest in possible signal of presence of charged Higgs in these modes. But such a large deviation in the rates, where standard-model has tree level contribution, coming from a charged Higgs alone is highly unlikely. However these decay modes are good probes to search for small charged Higgs signal if we can construct sensitive observables in these modes. In this work we would like to propose four new observables which shows much more sensitivity to the presence of charged Higgs than the usual observables such as $A_{\lambda}^{D^{(*)}}$ and $A_{\theta}^{D^{(*)}}$. These four observable are (1) $\frac{1}{A_{\lambda}^{D}}$,\ (2) $Y_{1}(q^{2}) = \frac{A^{D}_{\theta}}{A^{D}_{\lambda}}$,\ (3) $Y_{2}(q^{2}) = \frac{d\Gamma(B \rightarrow D^{*}\tau\nu_{\tau})}{d\Gamma_{D}(\lambda_{\tau}=+1/2) - d\Gamma_{D}(\lambda_{\tau}=-1/2)}$ and (4) $Y_{3}(q^{2}) = (\frac{q^{2}}{m^{2}_{\tau}})(A^{D}_{\lambda} + 1)\frac{1}{A^{D}_{\lambda}}$.

Letters in High Energy Physics

The \(\tau\) Magnetic Dipole Moment at Future Lepton Colliders

Can the symmetry breaking in the SM be determined by the "second minimum" of the Higgs potential?

Scalar models of formally interacting non-standard quantum fields in Minkowski space-time

Search for more sensitive observables to charged scalar in \(B \rightarrow D^{(*)}\tau\nu_{\tau}\) decays.