Lepton spectra from heavy quark decay

An analytic result for the O(α s ) corrections to the triple differential B → X u lν l decay rate is presented, to leading order in the heavy-quark expansion. This is relevant for computing partially integrated decay distributions with arbitrary cuts on kinematic variables. Several double and single differential distributions are derived, most of which generalize known results. In particular, an analytic result for the O(α s ) corrections to the hadronic invariant mass spectrum is presented. The effects of Fermi motion, which are important for the description of decay spectra close to infrared sensitive regions, are included. The behaviour of perturbation theory in the region of time-like momenta is also investigated.

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“…This agrees with the well-known result obtained first by Jeżabek and Kühn [25]. The function G(x) is regular for x → 0.…”

Section: Charged-lepton Energy Spectrumsupporting

confidence: 92%

B→X_ulbar nu_l decay distributions to order α_s

Fazio

Neubert

1999

J. High Energy Phys.

178

255

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“…393 for bottom quarks [72][73][74], and the same α i value with opposite sign for the respective antiparticles.…”

Section: Spin Correlation Observablesmentioning

confidence: 99%

Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7 TeVusing the ATLAS detector

Aad¹,

Abbott²,

Abdallah³

et al. 2014

Phys. Rev. D

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Measurements of spin correlation in top quark pair production are presented using data collected with the ATLAS detector at the LHC with proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 4.6 fb −1 . Events are selected in final states with two charged leptons and at least two jets and in final states with one charged lepton and at least four jets. Four different observables sensitive to different properties of the top quark pair production mechanism are used to extract the correlation between the top and antitop quark spins. Some of these observables are measured for the first time. The measurements are in good agreement with the Standard Model prediction at next-to-leadingorder accuracy.

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“…The direction of the charged lepton in semileptonic decays is optimally suited to analyze the polarization of the top quark [2]. The reason is [18] that in the top quark rest frame the double differential energy-angular distribution of the charged lepton is a product of the energy and the angular dependent factors. The angular dependence is of the form (1 + P cos θ), where P denotes the top quark polarization and θ is the angle between the polarization three-vector and the direction of the charged lepton.…”

mentioning

confidence: 99%

Top quark polarization in polarized $e^+e^-$ annihilation near threshold

Harlander

Jeżabek²,

Kühn

et al. 1997

Zeitschrift f�r Physik C Particles and Fields

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Top quark polarization in e + e − annihilation into tt is calculated for linearly polarized beams. The Green function formalism is applied to this reaction near threshold. The Lippmann-Schwinger equations for the S-wave and P -wave Green functions are solved numerically for the QCD chromostatic potential given by the two-loop formula for large momentum transfer and Richardson's ansatz for intermediate and small momenta. S-P -wave interference contributes to all components of the top quark polarization vector. Rescattering of the decay products is considered. The mean values nℓ of the charged lepton fourmomentum projections on appropriately chosen directions n in semileptonic top decays are proposed as experimentally observable quantities sensitive to top quark polarization. The results for nℓ are obtained including S-P -wave interference and rescattering of the decay products. It is demonstrated that for the longitudinally polarized electron beam a highly polarized sample of top quarks can be produced.

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Lepton spectra from heavy quark decay

Cited by 266 publications

References 12 publications

B→X_ulbar nu_l decay distributions to order α_s

B→X_ulbar nu_l decay distributions to order α_s

Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7 TeVusing the ATLAS detector

Top quark polarization in polarized $e^+e^-$ annihilation near threshold

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Lepton spectra from heavy quark decay

Cited by 266 publications

References 12 publications

B→Xulbar nul decay distributions to order αs

B→Xulbar nul decay distributions to order αs

Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7 TeVusing the ATLAS detector

Top quark polarization in polarized $e^+e^-$ annihilation near threshold

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Product

Resources

About

B→X_ulbar nu_l decay distributions to order α_s

B→X_ulbar nu_l decay distributions to order α_s