58 research outputs found
Analytic two-loop master integrals for production at hadron colliders: II
We present analytic results of the two-loop master integrals for hadronic
production that contain two massive propagators. For the planar integral
family, we succeed in constructing the canonical basis, so the results are
written in terms of multiple polylogarithms. The master integrals in the
non-planar integral families have been calculated by Taylor series expansion
around . Even with this simplification, there are multiple square
roots involved in the differential equations, which can not be rationalized
simultaneously. We find that a proper linear combination of the integral basis
alleviates the problem so that the results are expressed by multiple
polylogarithms or single integrals over multiple polylogarithms up to weight
four. These single integrals can be evaluated using the classic Newton-Cotes
formulas. These analytic results of master integrals would be used in the
computation of the two-loop amplitudes for production.Comment: 35 pages, 8 figure
Analytic decay width of the Higgs boson to massive bottom quarks at next-to-next-to-leading order in QCD
The Higgs boson decay to a massive bottom quark pair provides the dominant
contribution to the Higgs boson width. We present an exact result for such a
decay induced by the bottom quark Yukawa coupling with next-to-next-to-leading
order (NNLO) QCD corrections. We have adopted the canonical differential
equations in the calculation and obtained the result in terms of multiple
polylogarithms. We also compute the contribution from the decay to four bottom
quarks which consist of complete elliptic integrals or their one-fold
integrals. The small bottom quark mass limit coincides with the previous
calculation using the large momentum expansion. The threshold expansion
exhibits power divergent terms in the bottom quark velocity, which has a
structure different from that in but can be reproduced by
computing the corresponding Coulomb Green function. The NNLO corrections
significantly reduce the uncertainties from both the renormalization scale and
the renormalization scheme of the bottom quark Yukawa coupling. Our result can
be applied to a heavy scalar decay to a top quark pair.Comment: 29 pages, 11 figure
Analytic result for the top-quark width at next-to-next-to-leading order in QCD
We present the first full analytic results of next-to-next-to-leading order
(NNLO) QCD corrections to the top-quark decay width by
calculating the imaginary part of three-loop top-quark self-energy diagrams.
The results are all expressed in terms of harmonic polylogarithms and valid in
the whole region . The expansions in the and
limits coincide with previous studies. Our results can also be
taken as the exact prediction for the lepton invariant mass spectrum in
semileptonic decays. We also analytically compute the decay width
including the off-shell boson effect up to NNLO in QCD for the first time.
Combining these contributions with electroweak corrections and the finite
-quark mass effect, we determine the most precise top-quark width to be
1.331 GeV for GeV. The total theoretical uncertainties including
those from renormalization scale choice, top-quark renormalization scheme,
input parameters and missing higher-order corrections are scrutinized and found
to be less than .Comment: 8 pages, 3 figure
Analytic three-loop QCD corrections to top-quark and semileptonic decays
We present the first analytic results of NLO QCD corrections to the
top-quark decay width. We focus on the dominant leading color contribution,
which includes light-quark loops. At NNLO, this dominant contribution accounts
for 95% of the total correction. By utilizing the optical theorem, the NLO
corrections are related to the imaginary parts of the four-loop self-energy
Feynman diagrams, which are calculated with differential equations. The results
are expressed in terms of harmonic polylogarithms, enabling fast and accurate
evaluation. The third-order QCD corrections decrease the LO decay width by
0.667%, and the scale uncertainty is reduced by half compared to the NNLO
result. The most precise prediction for the top-quark width is now 1.321 GeV
for GeV. Additionally, we obtain the third-order QCD corrections
to the dilepton invariant mass spectrum and decay width in the semileptonic
transition.Comment: 11 pages, 2 figure
Clinical outcomes following surgical mitral valve plasty or replacement in patients with infectious endocarditis: A meta-analysis
BackgroundFor degenerative mitral disease, more and more evidences support that mitral valve plasty (MVP) has much better clincial outcomes than mitral valve replacement (MVR). However, the advantages of MVP in patients suffering from infectious endocarditis (IE) are unclear. To evaluate the appropriateness of MVP in IE patients, we conducted this meta-analysis. Based on the difference between active and healed phase, we not only compared the result of patients with IE, but also identified the subgroup with active IE.MethodsWe systematically searched the clinical trials comparing clinical outcomes of MVP and MVR in patients suffering from IE. Relevant articles were searched from January 1, 2000 to March 18, 2021 in Pubmed and Cochrane Library. Studies were excluded if they were with Newcastle–Ottawa Scale (NOS) score less than 6 or lacking of direct comparisons between MVP and MVR.Results23 studies were involved and 25,615 patients were included. Pooled analysis showed fewer adverse events and early or long-term death in the MVP group. However, more reoperations existed in this patient group. And the reinfection rate was close between two groups. Similar results were observed after identifying active IE subgroup, but there is no difference in the freedom from reoperation due to all-events.ConclusionsAlthough limitimations exited in this study, patients suffering from IE can benefit from both MVP and MVR. For surgeons with consummate skills, MVP can be the preferred choice for suitable IE patients
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