arXiv subjects

M. C. Mauser

Publications and source records attributed to M. C. Mauser.

9 recordsLinked to original sources

arXiv2008

$ O(α_s) $ corrections to polarized top decay into a charged Higgs $ t(\uparrow) \to H^+ + b $

We calculate the $ O(α_s) $ radiative corrections to polarized top quark decay into a charged Higgs boson and a massive bottom quark in two variants of the two-Higgs-doublet model. The radiative corrections to the polarization asymmetry of the decay may become as large as $ 25 % $. We provide analytical formulae for the unpolarized and polarized rates for $ m_b \neq 0 $ and for $ m_b = 0 $. For $ m_b = 0 $ our closed-form expressions for the unpolarized and polarized rates become rather compact.

hep-ph↗

arXiv2004

Semi-inclusive decays Lambda_b -> X_c + D_s^* at O(alpha_s) including Lambda_b and D_s^* polarization effects

In the leading order of the (1/m_b)-expansion in HQET the dominant contribution to the semi-inclusive decays of polarized Lambda_b baryons into the charm-strangeness mesons D_s and D_s^* is given by the partonic process b(up) -> c + (D_s^-, D_s^{*-}). Using standard values for the parameters of the process one expects a rather large branching ratio of approx. 8% into these two channels. In the factorization approximation the semi-inclusive decay of a polarized Lambda_b is governed by three unpolarized and four polarized structure functions for which we determine the nonperturbative O(1/m_b^2) corrections and the O(alpha_s) radiative corrections. We find that the perturbative and nonperturbative corrections amount to approx. 10% and approx. 3%, respectively. The seven structure functions can be measured through an analysis of the joint decay distributions of the process involving the polarization of the Lambda_b and the decays D_s^{*-} -> D_s^- + gamma and D_s^{*-} -> D_s^- + pi^0 for which we provide explicit forms. We also provide numerical results for the Cabibbo suppressed semi-inclusive decays Lambda_b -> X_u + (D_s, D_s^*).

hep-ph↗

arXiv2003

Leptonic $ μ$- and $ τ$-decays: mass effects, polarization effects and $ O(α) $ radiative corrections

We calculate the radiative corrections to the unpolarized and the four polarized spectrum and rate functions in the leptonic decay of a polarized $ μ$ into a polarized electron. The new feature of our calculation is that we keep the mass of the final state electron finite which is mandatory if one wants to investigate the threshold region of the decay. Analytical results are given for the energy spectrum and the polar angle distribution of the final state electron whose longitudinal and transverse polarization is calculated. We also provide analytical results on the integrated spectrum functions. We analyze the $ m_e \to 0 $ limit of our general results and investigate the quality of the $ m_e \to 0 $ approximation. In the $ m_e \to 0 $ case we discuss in some detail the role of the $ O(α) $ anomalous helicity flip contribution of the final electron which survives the $ m_e \to 0 $ limit. The results presented in this 0203048 also apply to the leptonic decays of polarized $ τ$-leptons for which we provide numerical results.

hep-ph↗

arXiv2002

Heavy Quarks on the Lattice

I review the basic ideas behind lattice QCD calculations that involve charm and bottom quarks. I report on the progress in getting the correct hyperfine splitting in charmonium from lattice QCD. Some of the basic technology behind numerical lattice QCD calculations is explained by studying some specific examples: computation of the charm quark mass, and the calculation of fB.

hep-lat↗

arXiv2002

Electroweak and finite width corrections to top quark decays into transverse and longitudinal $ W $-bosons

We calculate the electroweak and finite width corrections to the decay of an unpolarized top quark into a bottom quark and a $ W $-gauge boson where the helicities of the $ W $ are specified as longitudinal, transverse-plus and transverse-minus. Together with the $ O(α_s) $ corrections these corrections may become relevant for the determination of the mass of the top quark through angular decay measurements.

hep-ph↗

arXiv2001

Complete angular analysis of polarized top decay at O(alpha_s)

We calculate the O(alpha_s) radiative corrections to the three spin independent and five spin dependent structure functions that describe the angular decay distribution in the decay of a polarized top quark into a W-boson (followed by the decay W^{+} -> l^{+} + nu_l or by W^{+} -> anti-q + q and a bottom quark. The angular decay distribution is described in cascade fashion, i.e. the decay t(uparrow) -> W^{+} + X_b is analyzed in the top rest system while the subsequent decay W^{+} -> l^{+} + nu_l (or W^{+} -> anti-q + q) is analyzed in the W rest frame. We present our results for the eight O(alpha_s) integrated structure functions in analytical form keeping the mass of the bottom quark finite. In the limit m_b -> 0 the structure function expressions reduce to rather compact forms.

hep-ph↗

arXiv2000

Longitudinal, transverse-plus and transverse-minus W-bosons in unpolarized top quark decays at O(alpha_s)

We consider the O(alpha_s) radiative corrections to the decay of an unpolarized top quark into a bottom quark and a W-gauge boson where the helicities of the W are specified as longitudinal, transverse-plus and transverse-minus. The O(alpha_s) radiative corrections lower the normalized longitudinal rate Gamma_L/Gamma by 1.06% and increase the the normalized transverse-minus rate Gamma_-/Gamma by 2.17%. We find that the normalized transverse-plus rate Gamma_+/Gamma, which vanishes at the Born term level for m_b->0, receives radiative correction contributions at the sub-percent level. We discuss m_b!=0 effects for the Born term and the alpha_s-contributions but find these to be small. Our results are discussed in the light of recent measurements of the helicity content of the W in top quark decays by the CDF Collaboration.

hep-ph↗

arXiv2000

Inclusive Decays of B Mesons into D_s and $D_s^{\ast}$ at $O(α_s)$ Including $D_s^{\ast}$ Polarization Effects

The dominant contribution to the inclusive decays of $B$ mesons into the charm-strangeness mesons $D_s$ and $D_s^{\ast}$ is expected to be given by the partonic process $b \to c+(D_s^-,D_s^{\ast -})$. We determine the nonperturbative $O(1/m_b^2)$ and the $O(α_s)$ radiative corrections to $b \to c+(D_s^-,D_s^{\ast -})$ and thereby to the inclusive decays $ \bar{B} \to X_c+(D_s^-,D_s^{\ast -})$. The new feature of our calculation is that we separately determine the nonperturbative and the $O(α_s)$ corrections to the longitudinal ($L$) and transverse ($T$) pieces of the spin 1 $D_s^{\ast -}$ meson. The longitudinal/transverse composition of the $D_s^{\ast -}$ can be probed through its two principal decay modes $D_s^{\ast -} \to D_s^- + γ$ and $D_s^{\ast -} \to D_s^- + π^0$ for which we write down the angular decay distributions.

hep-ph↗

arXiv1999

Polarized top decay into polarized W: t(up)->W(up) + b at O(alpha_s)

We consider the decay of a polarized top quark into a polarized W-boson plus a bottom quark, followed by the decay of the W-boson into a pair of leptons or quarks. The polar angle distribution of the top spin relative to the W-momentum and the polar angle distribution of the lepton (or quark) in the W-rest frame is governed by three polarized and three unpolarized rate functions which are related to the double density matrix elements of the decay $t \to W^+ + b$. We obtain analytical expressions for the $O(α_s)$ radiative corrections to the three polarized and three unpolarized rate functions. We also provide a comprehensive discussion of the dependence of the longitudinal, transverse and normal polarization of the top quarks produced at $e^+e^-$-colliders on beam polarization parameters.

hep-ph↗