A simplest seesaw model of the TM1 and μ-τ reflection symmetries for the neutrino masses and leptogenesis

In this paper,following the Occam’s razor principle,we have put forward a very simple form of the Dirac neutrino mass matrix M_(D) in the minimal seesaw model with the right-handed neutrino mass matrix being diagonal M_(R)=diag(M_(1),M_(2));it has one texture zero and only contains three real parameters,whose values can be determined from the neutrino oscillation experimental results.Such a model leads to a neutrino mass matrix M_(v)≃-M_(D)M_(R)^(-1)M_(D)^(T)that obeys the TM1 and μ-τ reflection symmetries simultaneously.In this way all the lepton flavor mixing parameters except for θ_(13) are predicted;the value of θ_(12) is predicted by the TM1 symmetry,while those of θ_(23),δ,ρ and σ by the μ-τ reflection symmetry.And the neutrino masses are predicted to be of the NO case with m_(1)=0,for which all three light neutrino masses will be pinned down with the help of the experimental results for the neutrino mass squared differences.For these results,the effective Majorana neutrino mass∣(M_(ν))_(ee)∣that controls the rate of the neutrinoless double beta decay is predicted to be 1.6 or 3.8 meV in the case of σ=0 or π/2.We have also studied the implications of the model for leptogenesis.It turns out that only in the two-flavor leptogenesis regime(which holds in the temperature range 10^(9)-10^(12) GeV)can leptogenesis have a chance to be successful.And a successful leptogenesis can be achieved at M_(1)≃1.2×10^(11) GeV in the case of σ=π/2,but not in the case of σ=0.

B_((s))→D^(∗∗)_((s))form factors in HQEFT and model independent analysis of relevant semileptonic decays with NP effects

The form factors of B(s)decays into P-wave excited charmed mesons(including D∗0(2300),D1(2430),D1(2420),D∗2(2460)and their strange counterparts,denoted generically as D∗∗(s))are systematically calculated via QCD sum rules in the framework of heavy quark effective field theory(HQEFT).We consider contributions up to the next leading order of heavy quark expansion and give all the relevant form factors,including the scalar and tensor ones only relevant for possible new physics effects.The expressions for the form factors in terms of several universal wave functions are derived via heavy quark expansion.These universal functions can be evaluated through QCD sum rules.Then,the numerical results of the form factors are presented.With the form factors given here,a model independent analysis of relevant semileptonic decays B(s)→D∗∗(s)lν¯l is performed,including the contributions from possible new physics effects.Our predictions for the differential decay widths,branching fractions,and ratios of branching fractions R(D∗∗(s))may be tested in more precise experiments in the future.

Searching for the light leptophilic gauge boson Zx via four-lepton final states at the CEPC

We investigate the possibility of detecting the leptophilic gauge boson Z_(x) predicted by the U(1)Le−Lμmodel via the processes e+e−→ℓ^(+)ℓ^(−)Z_(x)(Z_(x)→ℓ^(+)ℓ^(−))and e+e−→ℓ^(+)ℓ^(−)Z_(x)(Z_(x)→νℓ¯νℓ)at the Circular Electron Positron Collider(CEPC)with a center of mass energy√s=240 GeV and luminosity L=5.6ab^(−1).We provide the expected sensitivities of the CEPC to the parameter space at the 1σ,2σ,3σ,and 5σlevels.

Charged-current non-standard neutrino interactions at the LHC and HL-LHC

A series of new physics scenarios predict the existence of the extra charged gauge boson W’,which can induce charged-current(CC)non-standard neutrino interactions(NSIs).The theoretical constraints on the simplified W’model and further on the CC NSI parameters ε_(αβ)^-qq'Y from partial wave unitarity and W’decays are considered.The sensitivity of the process pp→W’→lv to the W’model at the LHC and high-luminosity(HL)LHC experiments is investigated by estimating the expected constraints on ε_(αβ)^-qq'Y (α=β=e orμ)using a Monte-Carlo(MC)simulation.We find that the interference effect plays an important role,and the LHC can strongly constrain ε_(αβ)^-qq'L .Compared with those at the 13 TeV LHC with L=139 fb^(-1),the expected constraints at the 14TeV LHC with L=3 ab^(-1)can be strengthened to approximately one order of magnitude.

Study of the gluonic quartic gauge couplings at muon colliders

The potential of muon colliders opens up new possibilities for the exploration of new physics beyond the Standard Model.It is worthwhile to investigate whether muon colliders are suitable for studying gluonic quartic gauge couplings(gQGCs),which can be contributed by dimension-8 operators in the framework of the Standard Model effective field theory,and are intensively studied recently.In this paper,we study the sensitivity of the processμ^(+)μ^(-)→jjν■to gQGCs.Our results indicate that the muon colliders with c.m.energies larger than 4 TeV can be more sensitive to gQGCs than the Large Hadron Collider.