826 research outputs found
Phenomenological discriminations of the Yukawa interactions in two-Higgs doublet models with symmetry
There are four types of two-Higgs doublet models under a discrete
symmetry imposed to avoid tree-level flavour-changing neutral current, i.e.
type-I, type-II, type-X and type-Y models. We investigate the possibility to
discriminate the four models in the light of the flavour physics data,
including mixing, , and
decays, the recent LHC Higgs data, the direct search
for charged Higgs at LEP, and the constraints from perturbative unitarity and
vacuum stability. After deriving the combined constraints on the Yukawa
interaction parameters, we have shown that the correlation between the mass
eigenstate rate asymmetry of and the
ratio could be sensitive probe to discriminate the four models with
future precise measurements of the observables in the
decay at LHCb.Comment: 29 pages, 4 tables, 11 figures. v3: minor corrections included,
matches published version in EPJ
Next-to-leading order QCD corrections to a heavy resonance production and decay into top quark pair at the LHC
We present a complete next-to-leading order (NLO) QCD calculation to a heavy
resonance production and decay into a top quark pair at the LHC, where the
resonance could be either a Randall-Sundrum (RS) Kaluza-Klein (KK) graviton
or an extra gauge boson . The complete NLO QCD corrections can enhance the
total cross sections by about and for the and
the , respectively, depending on the resonance mass. We also explore in
detail the NLO corrections to the polar angle distributions of the top quark,
and our results show that the shapes of the NLO distributions can be different
from the leading order (LO) ones for the KK graviton. Moreover, we study the
NLO corrections to the spin correlations of the top quark pair production via
the above process, and find that the corrections are small.Comment: Published version in PR
Flavor Violating Higgs Couplings in Minimal Flavor Violation
Motivated by the rencent LHC data on the lepton-flavor violating (LFV) decays
and , we study the
Higgs-mediated flavor-changing neutral current (FCNC) interactions in the
effective field theory (EFT) approach without and with the minimal flavor
violation (MFV) hypothesis, and concentrate on the later. After considering the
and physics data, the various LFV processes, and the LHC Higgs data,
severe constraints on the Higgs FCNC couplings are derived, which are dominated
by the LHC Higgs data, the mixing, and the
decay. In the general case and the MFV framework, allowed ranges of various
observables are obtained, such as ,
, , and the
branching ratio of conversion in Al. Future prospects of searching
for the Higgs FCNC interactions at the low-energy experiments and the LHC are
discussed.Comment: 26 pages, 5 figures, minor errors corrected, figures slightly
changed, comments and references adde
Search for sterile neutrinos decaying into pions at the LHC
We study the possibility to observe sterile neutrinos with masses in the
range between 5 GeV and 20 GeV at the LHC, using the exclusive semileptonic
modes involving pions, namely W to lepton + N to n pions + lepton+lepton (n =
1, 2, 3). The two pion and three pion modes require extrapolations of form
factors to large time-like , which we do using vector dominance models as
well as light front holographic QCD, with remarkable agreement. This mass
region is difficult to explore with inclusive dilepton+dijet modes or trilepton
modes and impossible to explore in rare meson decays. While particle
identification is a real challenge in these modes, vertex displacement due to
the long living neutrino in the above mass range can greatly help reduce
backgrounds. Assuming a sample of W bosons at the end of the LHC Run 2,
these modes could discover a sterile neutrino in the above mass range or
improve the current bounds on the heavy-to-light lepton mixings by an order of
magnitude, . Moreover, by studying the equal
sign and opposite sign dileptons, the Majorana or Dirac character of the
sterile neutrino may be revealed.Comment: 18 pages, 4 double figure
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