Bmesons from top-quark decay in the presence of the charged Higgs boson in the zero-mass variable-flavor-number scheme

Abstract

We study the energy spectrum of the inclusive bottom-flavored mesons in top-quark decay into a charged-Higgs boson and a massless bottom quark at next-to-leading order (NLO) in the two-Higgsdoublet model. To extract the result we work in the Zero-Mass Variable-Flavor-Number scheme (ZM-VFNs) using realistic nonperturbative fragmentation functions obtained through a global fit to e þ e À data from CERN LEP1 and SLAC SLC on the Z-boson resonance. We study both the contribution of the bottom quark fragmentation and the gluon fragmentation to produce the bottom-flavored meson (B-Meson). We find that the contribution of the gluon leads to an appreciable reduction in decay rate at low values of the B-meson energy. It means the NLO corrections are significant.

QCD analysis of light charged Higgs production through polarized top quark decay in two different frames

“…In refs. [23,24], we calculated the unpolarized differential decay width dΓ(t → bH + )/dx b at NLO and showed that our result after integration over x b (0 ≤ x b ≤ 1) is in complete agreement with refs. [19][20][21] and the corrected version of [22].…”

“…Thus, at the LHC any deviation of the B-meson energy spectrum from the SM predictions can be considered as a signal for the existence of charged Higgs. Although, the SM contribution is normally larger than the one coming from 2HDM [23,24], but there is always a clear separation between the decay channels t → bW + and t → bH + in both the ttX pair production and the t/tX single top production at the LHC, this point is mentioned in [33]. This paper is organized as follows.…”

“…where dΓ unpol /dx b is presented in [23,24]. The O(α s ) real gluon (tree-graph) contribution to the differential decay rate results from the square of the real amplitude as…”

“…obtaining the results above, we applied the unpolarized decay rate presented in [23,24] and the polarized ones in the first and second helicity systems given in [25] and (3.21), respectively. Here, we take a moment to mention to an important effect which was neglected in our previous calculations of charged Higgs production.…”

“…In eq. (2.2) dΓ unpol /dx i stands for the unpolarized differential rate, which is extensively calculated in [23,24] up to NLO, and dΓ pol /dx i refers to the polarized one. The analytical expression for the differential partial width dΓ pol /dx i depends on the selected helicity coordinate system.…”