Z′-mediated flavor-changing neutral currents and their contributions toBq0

Abstract

ZЈ bosons are known to naturally exist in well-motivated extensions of the standard model. The leptophobic ZЈ gauge boson can appear in models with E 6 gauge symmetry due to the mixing of the gauge-boson kinetic terms. We show that flavor-changing neutral currents can be generated in some of these models due to the mixing of the ordinary d R , s R , and b R quark fields with the exotic h R , where exotic h R means an exotic vector-singlet charge Ϫ1/3 quark h. Since the ZЈ boson does not couple to charged leptons, the constraints on the flavor-changing couplings U db ZЈ and U sb ZЈ are relatively weak. B q 0 -B q 0 mixing (qϭd,s) can be dominated by ZЈ-mediated flavor-changing neutral currents.

Study of semileptonic decays B→πl+l− and BNayek1, Maji2, Sahoo3 2019Phys. Rev. DSelf Cite110140View full textAdd to dashboardCite

“…In a classically conformal Uð1Þ 0 extended standard model [42], an upper bound for the mass of the Z 0 boson is estimated as M Z0 ≤ 6 TeV. Basically, flavor mixing between ordinary and exotic left-handed quark sector induces Z-mediated FCNC but right-handed quarks d R , s R and b R have different Uð1Þ 0 quantum numbers which induce Z 0 -mediated FCNC while mixing with the exotic q R [43][44][45][46][47]. The FCNC transition mediated by the addition of the Z and Z 0 bosons occurs at the tree level in the up-type quark sector [48].…”

Analysis of Λ b → Λl + l − rare decays in a non-universal Z′ model

“…In a study of B meson decays with Z  -mediated flavor-changing neutral currents [38], the Z  -boson was studied in the mass range of a few hundred GeV to 1 TeV. Sahoo et al [39] [38,[43][44][45][46] among the ordinary down quark types. Tree level FCNC interactions can also be induced by an additional boson in the up-type quark sector [47].…”

EFFECT OF BOTH Z AND Z′ MEDIATED FLAVOR-CHANGING NEUTRAL CURRENTS ON THE BARYONIC RARE DECAY Λb→Λℓ+ℓ-

“…With FCNCs, both Z and Z ′ -boson contributes at tree level, and its contribution will interfere with the SM contributions [31,32,35]. In this paper, we study…”

“…quantum numbers than exotic R q and their mixing will induce Z ′ -mediated FCNCs [29,31,32] among the ordinary down quark types. Tree level FCNC interactions can also be induced by an additional Z ′ -boson on the up-type quark sector [33].…”

“…The same idea can be applied to a Z′ -boson i.e., mixing among particles which have different Z′ quantum numbers will induce FCNCs due to Z′ exchange [31,32,47]. Since the Z q p U are generated by mixing that breaks weak isospin, they are expected to be at most O( (28) as :…”