| DATE: |
2008-03-19 14:00 - 15:00 |
| PLACE: |
Honkan 2F Rm 220 |
| TITLE: |
Running mass of the b-quark in QCD and MSSM |
| CONTACT: |
Daisuke Nomura |
| SPEAKER: |
Dr. Alexander Bednyakov (JINR, Russia) |
| LANGUAGE: |
English |
| ABSTRACT: |
Running mass of the b-quark defined in DRbar-scheme is one of the
important parameters of MSSM. To find its value, it should be
related to some known experimental input. The b-quark running mass
defined in nonsupersymmetric QCD is chosen for determination of
the corresponding parameter in MSSM. Two-loop relation between
these two quantities is found by considering five-flavor QCD as
an effective theory obtained from its supersymmetric extension.
A numerical analysis of the calculated two-loop contribution and
its impact on the MSSM spectrum is discussed. Since for
nonsupersymmetric models MSbar-scheme is more natural than DRbar,
a new procedure is proposed that allows one to calculate relations
between MSbar- and DRbar-parameters. Unphysical epsilon-scalars
that give rise to the difference between the above-mentioned schemes
are assumed to be heavy and decoupled in the same way as physical
degrees of freedom. By means of this method it is possible to
``catch two rabbits'', i.e., decouple heavy particles and turn
from DRbar to MSbar, at the same time. The advantages and
disadvantages of the method are briefly discussed.
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