We study the scaled-energy (x B ) distribution of bottom-flavored hadrons (B) inclusively produced in top-quark decays at next-to-leading order (NLO) in the general-mass variable-flavor-number scheme endowed with realistic, nonperturbative fragmentation functions that are obtained through a global fit to e + e − data from CERN LEP1 and SLAC SLC exploiting their universality and scaling violations. Specifically, we study the effects of gluon fragmentation and finite bottomquark and B-hadron masses. We find the NLO corrections to be significant. Gluon fragmentation leads to an appreciable reduction in the partial decay width at low values of x B . Hadron masses are responsible for the low-x B threshold, while the bottom-quark mass is of minor importance. Neglecting the latter, we also study the doubly differential distribution d 2 Γ/(dx B d cos θ) of the partial width of the decay t → bW + → Bℓ + ν ℓ + X, where θ is the decay angle of the charged lepton in the W -boson rest frame.PACS numbers: 12.38.Bx, 13.85.Ni, 14.40.Nd, 14.65.Ha Among other things, the CERN Large Hadron Collider (LHC) is a superlative top factory, producing about 90 million top-quark pairs per year of running at design energy √ S = 14 TeV and design luminosity L = 10 34 cm −2 s −1 in each of the four experiments [1]. This will allow us to determine the properties of the top quark, such as its mass m t , total decay width Γ t , branching fractions, and elements V tq of the Cabibbo-Kobayashi-Maskawa (CKM) [2] quark mixing matrix, with unprecedented precision. Due to its large mass, the top quark decays so rapidly that it has no time to hadronize and passes on its full spin information to its decay products. If it were not for the confinement of color, the top quark could, therefore, be considered as a free particle. Due to |V tb | ≈ 1, top quarks almost exclusively decay to bottom quarks, via t → bW + .On the other hand, bottom quarks hadronize, via b → B + X, before they decay, so that the decay process t → BW + + X is of prime importance, and it is an urgent task to predict its partial decay width as realistically and reliably as possible. Of particular interest are the distribution in the scaled B-hadron energy x B in the top-quark rest frame, and, in the case of leptonic W -boson decays W + → ℓ + ν ℓ , the one in the charged-lepton decay angle θ in the W -boson rest frame. In fact, the x B distribution provides direct access to the B-hadron fragmentation functions (FFs), and the cos θ distribution allows us to analyze the W -boson polarization and so to further constrain the B-hadron FFs by exploiting x B distributions for all the W -boson polarization states. B mesons are, for instance, cleanly identified by their decays to J/ψ mesons, which are easy to tag through their spectacular decays to e + e − and µ + µ − pairs.The theoretical aspects of top-quark physics at the LHC are nicely summarized in a recent review paper [3]. In the approximation of treating the bottom quark as a stable final-state particle that does not hadronize, the QCD co...

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.

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We present, for the first time, a set of next-to-next-to-leading order (NNLO) fragmentation functions (FFs) describing the production of charmed-meson D Ã from partons. Exploiting the universality and scaling violations of FFs, we extract the NLO and NNLO FFs through a global fit to all relevant data sets from single-inclusive e þ e − annihilation. The uncertainties for the resulting FFs as well as the corresponding observables are estimated using the Hessian approach. We evaluate the quality of the SKM18 FFs determined in this analysis by comparing with the recent results in literature and show how they describe the available data for single-inclusive D ÃAE -meson production in electron-positron annihilation. As a practical application, we apply the extracted FFs to make our theoretical predictions for the scaled-energy distributions of D ÃAE -mesons inclusively produced in top quark decays. We explore the implications of SKM18 for LHC phenomenology and show that our findings of this study can be introduced as a channel to indirect search for top-quark properties.

We present our analytic results for the NLO corrections to the partial decay width t → H + b followed by b → BX for nonzero b-quark mass (m b = 0) in the FixedFlavor-Number scheme (FFNs). To make our predictions for the energy distribution of the outgoing bottom-flavored hadron (B-hadron) as a function of the normalized B-energy fraction x B , we apply the General-Mass Variable-Flavor-Number scheme (GM-VFNs) in the general two-Higgs-doublet model. In order to describe both the b-quark and the gluon hadronizations in top decay we use fragmentation functions extracted from data from e + e − machines. We find that the most reliable prediction for the B-hadron energy spectrum is made in the GM-VFN scheme.

We present nonperturbative fragmentation functions (FFs) for bottom-flavored (B) hadrons both at next-to-leading (NLO) and, for the first time, at next-to-next-to-leading order (NNLO) in the MS factorization scheme with five massless quark flavors. They are determined by fitting all available experimental data of inclusive single B-hadron production in e + e − annihilation, from the ALEPH, DELPHI, and OPAL Collaborations at CERN LEP1 and the SLD Collaboration at SLAC SLC. The uncertainties in these FFs as well as in the corresponding observables are estimated using the Hessian approach. We perform comparisons with available NLO sets of B-hadron FFs. We apply our new FFs to generate theoretical predictions for the energy distribution of B hadrons produced through the decay of unpolarized or polarized top quarks, to be measured at the CERN LHC.

We present new sets of proton fragmentation functions (FFs) describing the production of protons from the gluon and each of the quarks, obtained by a global fit to all relevant data sets of singleinclusive electron-positron annihilation. Specifically, we determine their uncertainties using the Gaussian method for error estimation. Our analysis is in good agreement with the e + e − annihilation data. We also include finite-mass effects of the proton in our calculations, a topic with very little attention paid to in the literatures. Proton mass effects turn out to be appreciable for gluon and light quark FFs. The inclusion of finite-mass effects tends to improve the overall description of the data by reducing the minimized χ 2 values significantly. As an application, we apply the extracted FFs to make predictions for the scaled-energy distribution of protons inclusively produced in top quark decays at next-to-leading order, relying on the universality and scaling violations of FFs.