arXiv subjects
Publications and source records attributed to K. Melnikov.
In this note we report some model-independent bounds involving transition form factors for $ \Omb \rightarrow \Omc $ and $ \Omb \rightarrow \Omc ^* $ and the nonperturbative matrix elements of the $ \Omb $ system. They are derived by using operator product expansion (OPE) in Heavy Quark Effective Theory .
We have calculated part of O($α_{S}$) QCD radiative correction to the total cross-section of top's threshold production in $ e^{+}e^{-} \to t\bar t \to W^{-} b W^{+} \bar b$ reaction. We found out a curious fact: there is no O($α_{S}$) correction to the total cross-section, originated from $b \bar b , t \bar b ,\bar t b $ gluon exchange and corresponding gluon emission. Thus, all O($α_{S}$) corrections which are non-zero, can be classified as: 1) corrections to $t \bar t$ nonrelativistic potential 2) corrections to the top's width 3) hard gluon correction to $γt \bar t$-vertex. These corrections are well-known and were described in the previous papers. We can conclude that similar situation takes place for all unstable particles threshold production. This result can be expressed in the form of a general statment: There is no O($α_{QED}$ or $α_{QCD}$) corrections for the total cross-section , originated from the "jet-jet" interection.
QCD radiative correction to Higgs $\rightarrow$ two photons decay rate is calculated. Below the threshold we found negligible correction, thus supporting results obtained earlier by Djouadi et all [7]. Above the threshold radiative correction appears to be large for both real and imaginary part of H $γγ$ vertex. This leads to radiative correction for $Γ$(H $\rightarrow γγ$) to be of order 20--100 percents at $m_{t}=150 GeV$. Possible applications of our results for Higgs search at Next Linear Colliders (NLC) are briefly discussed.