152 research outputs found
Characterization of energetically functional inverted membrane vesicles from Corynebacterium glutamicum
AbstractWe show that inverted membrane vesicles from Corynebacteriwn glutamicum, a Gram-positive bacterium, are able to generate and maintain an electrochemical gradient of protons in response to the addition of NADH. This result indicates that the respiratory chain is intact and that the vesicles are reasonably impermeable to protons. These membrane vesicles may be the starting point for in vitro translocation studies of proteins in Gram-positive bacteria
Infrared Fixed Point Structure in Minimal Supersymmetric Standard Model with Baryon and Lepton Number Violation
We study in detail the renomalization group evolution of Yukawa couplings and
soft supersymmetry breaking trilinear couplings in the minimal supersymmetric
standard model with baryon and lepton number violation. We obtain the exact
solutions of these equations in a closed form, and then depict the infrared
fixed point structure of the third generation Yukawa couplings and the highest
generation baryon and lepton number violating couplings. Approximate analytical
solutions for these Yukawa couplings and baryon and lepton number violating
couplings, and the soft supersymmetry breaking couplings are obtained in terms
of their initial values at the unification scale. We then numerically study the
infrared fixed surfaces of the model, and illustrate the approach to the fixed
points.Comment: 16 pages REVTeX, figures embedded as epsfigs, replaced with version
to appear in Physical Review D, minor typographical errors eliminated and
references reordered, figures correcte
Infra-red fixed points in supersymmetry
Model independent constraints on supersymmetric models emerge when certain
couplings are drawn towards their infra-red (quasi) fixed points in the course
of their renormalization group evolution. The general principles are first
reviewed and the conclusions for some recent studies of theories with R-parity
and baryon and lepton number violations are summarized.Comment: 5 pages Latex with 2 figures embedded as eps files Talk given at
WHEPP6, Chennai, India, January 3-15, 2000, to appear in special issue of
Praman
Infrared quasi-fixed solutions in the NMSSM
The considerable part of the parameter space in the MSSM corresponding to the
infrared quasi fixed point scenario is almost excluded by LEP II bounds on the
lightest Higgs boson mass. In the NMSSM the mass of the lightest Higgs boson
reaches its maximum value in the strong Yukawa coupling limit when Yukawa
couplings are essentially larger than gauge ones at the Grand Unification
scale. In this limit the solutions of the renormalisation group equations are
attracted to the infrared and Hill type effective fixed lines or surfaces in
the Yukawa coupling parameter space. They are concentrated in the vicinity of
quasi fixed points for . However the solutions are attracted
to such points rather weakly. For this reason when all the
solutions of the renormalisation group equations are gathered near a line in
the Hill type effective surface. In the paper the approximate solutions for the
NMSSM Yukawa couplings are given. The possibility of --quark and
--lepton Yukawa coupling unification at the scale is also
discussed.Comment: 32 pages, 8 figures included, LaTeX 2
Asymptotically Free Non-Abelian Gauge Theories With Fermions and Scalars As Alternatives to QCD
In this paper we construct non-Abelian gauge theories with fermions and
scalars that nevertheless possess asymptotic freedom.The scalars are taken to
be in a chiral multiplet transforming as under
and transforming as singlets under the colour SU(3) group. We consider two
distinct scenarios, one in which the additional scalars are light and another
in which they are heavier than half the Z-boson mass. It is shown that
asymptotic freedom is obtained without requiring that all additional couplings
keep fixed ratios with each other. It is also shown that both scenarios can not
be ruled out by what are considered standard tests of QCD like R- parameter,
g-2 for muons or deep inelastic phenomena. The light mass scenario is however
ruled out by high precision Z-width data (and only by that one data).The heavy
mass scenario is still viable and is shown to naturally pass the test of
flavour changing neutral currents. It also is not ruled out by precision
electroweak oblique parameters. Many distinctive experimental signatures of
these models are also discussed.Comment: 37 pages in LATEX with 10 fig
A Search for Instantons at HERA
A search for QCD instanton (I) induced events in deep-inelastic scattering
(DIS) at HERA is presented in the kinematic range of low x and low Q^2. After
cutting into three characteristic variables for I-induced events yielding a
maximum suppression of standard DIS background to the 0.1% level while still
preserving 10% of the I-induced events, 549 data events are found while
363^{+22}_{-26} (CDM) and 435^{+36}_{-22} (MEPS) standard DIS events are
expected. More events than expected by the standard DIS Monte Carlo models are
found in the data. However, the systematic uncertainty between the two
different models is of the order of the expected signal, so that a discovery of
instantons can not be claimed. An outlook is given on the prospect to search
for QCD instanton events using a discriminant based on range searching in the
kinematical region Q^2\gtrsim100\GeV^2 where the I-theory makes safer
predictions and the QCD Monte Carlos are expected to better describe the
inclusive data.Comment: Invited talk given at the Ringberg Workshop on HERA Physics on June
19th, 2001 on behalf of the H1 collaboratio
Semiclassical Double-Pomeron Production of Glueballs and
A semiclassical theory of high energy scattering based on interrupted
tunneling (instantons) or QCD sphaleron production has been recently developed
to describe the growing hadronic cross section and properties of the soft
Pomeron. In this work we address double-pomeron processes in this framework for
the first time. We specifically derive the cross section for central production
of parity even and odd clusters, scalar and pseudoscalar glueballs, and
in parton-parton scattering at high energy. We show that the specific
dependence of the production cross section on all its kinematical variables
compares favorably with the UA8 data on inclusive cluster production, as well
as the WA102 data on exclusive central production of scalar glueball and
, in double-pomeron exchange scattering. The magnitude of the cross
section and its dependece on kinematic variables is correct, explaining in
particular a large deviation from the Pomeron factorization at cluster masses
in the range GeV reported by UA8
Higgs bosons in the simplest SUSY models
Nowadays in the MSSM the moderate values of are almost excluded
by LEP II lower bound on the lightest Higgs boson mass. In the Next-to-Minimal
Supersymmetric Standard Model the theoretical upper bound on it increases and
reaches maximal value in the strong Yukawa coupling limit when all solutions of
renormalization group equations are concentrated near the quasi-fixed point.
For calculation of Higgs boson spectrum the perturbation theory method can be
applied. We investigate the particle spectrum in the framework of the modified
NMSSM which leads to the self-consistent solution in the strong Yukawa coupling
limit. This model allows one to get GeV at values of
. In the investigated model the lightest Higgs boson mass
does not exceed GeV. The upper bound on the lightest CP-even
Higgs boson mass in more complicated supersymmetric models is also discussed.Comment: 27 pages, 5 figures included, LaTeX 2e. Plenary talk at the
Conference of RAS Nuclear Physics Department 2000 in ITEP, Moscow, Russia; to
appear in Phys. Atom. Nuc
Nonminimal Supersymmetric Standard Model with Baryon and Lepton Number Violation
We carry out a comprehensive analysis of the nonminimal supersymmetric
standard model (NMSSM) with baryon and lepton number violation. We catalogue
the baryon and lepton number violating dimension four and five operators of the
model. We then study the renormalization group evolution and infrared stable
fixed points of the Yukawa couplings and the soft supersymmetry breaking
trilinear couplings of this model with baryon and lepton number (and R-parity)
violation involving the heaviest generations. We show analytically that in the
Yukawa sector of the NMSSM there is only one infrared stable fixed point. This
corresponds to a non-trivial fixed point for the top-, bottom-quark Yukawa
couplings and the violating coupling , and a trivial one
for all other couplings. All other possible fixed points are either unphysical
or unstable in the infrared region. We also carry out an analysis of the
renormalization group equations for the soft supersymmetry breaking trilinear
couplings, and determine the corresponding fixed points for these couplings. We
then study the quasi-fixed point behaviour, both of the third generation Yukawa
couplings and the baryon number violating coupling, and those of the soft
supersymmetry breaking trilinear couplings. From the analysis of the fixed
point behaviour, we obtain upper and lower bounds on the baryon number
violating coupling , as well as on the soft supersymmetry
breaking trilinear couplings. Our analysis shows that the infrared fixed point
behavior of NMSSM with baryon and lepton number violation is similar to that of
MSSM.Comment: 35 pages, Revtex, 6 eps fig
Quasi-fixed point scenario in the modified NMSSM
The simplest extension of the MSSM that does not contradict LEP II
experimental bound on the lightest Higgs boson mass at is the
modified Next-to-Minimal Supersymmetric Standard Model (MNSSM). We investigate
the renormalization of Yukawa couplings and soft SUSY breaking terms in this
model. The possibility of -quark and -lepton Yukawa coupling
unification at the Grand Unification scale is studied. The particle
spectrum is analysed in the vicinity of the quasi-fixed point where the
solutions of renormalization group equations are concentrated at the
electroweak scale.Comment: 19 pages, 3 figures, LaTeX2
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