60,338 research outputs found
Electroweak Absorptive Parts in NRQCD Matching Conditions
Electroweak corrections associated with the instability of the top quark to
the next-to-next-to-leading logarithmic (NNLL) total top pair threshold cross
section in e+e- annihilation are determined. Our method is based on absorptive
parts in electroweak matching conditions of the NRQCD operators and the optical
theorem. The corrections lead to ultraviolet phase space divergences that have
to be renormalized and lead to NLL mixing effects. Numerically, the corrections
can amount to several percent and are comparable to the known NNLL QCD
corrections.Comment: 17 pages, revtex4, 4 postscript figures included; minor changes in
text and references, title modified in printed versio
Alternative Buffer-Layers for the Growth of SrBi2Ta2O9 on Silicon
In this work we investigate the influence of the use of YSZ and CeO2/YSZ as
insulators for Metal- Ferroelectric-Insulator-Semiconductor (MFIS) structures
made with SrBi2Ta2O9 (SBT). We show that by using YSZ only the a-axis oriented
Pyrochlore phase could be obtained. On the other hand the use of a CeO2/YSZ
double-buffer layer gave a c-axis oriented SBT with no amorphous SiO2 inter-
diffusion layer. The characteristics of MFIS diodes were greatly improved by
the use of the double buffer. Using the same deposition conditions the memory
window could be increased from 0.3 V to 0.9 V. From the piezoelectric response,
nano-meter scale ferroelectric domains could be clearly identified in SBT thin
films.Comment: 5 pages, 9 figures, 13 refernece
On Electroweak Matching Conditions for Top Pair Production at Threshold
We determine the real parts of electroweak matching conditions relevant for
top quark pair production close to threshold in e+e- annihilation at
next-to-next-to-leading logarithmic (NNLL) order. Numerically the corrections
are comparable to the NNLL QCD corrections.Comment: 12 pages, revtex4, 1 postscript figure included; minor changes in
text and references, version published in Phys. Rev.
Magnetized strange quark matter and magnetized strange quark stars
Strange quark matter could be found in the core of neutron stars or forming
strange quark stars. As is well known, these astrophysical objects are endowed
with strong magnetic fields which affect the microscopic properties of matter
and modify the macroscopic properties of the system. In this paper we study the
role of a strong magnetic field in the thermodynamical properties of a
magnetized degenerate strange quark gas, taking into account beta-equilibrium
and charge neutrality. Quarks and electrons interact with the magnetic field
via their electric charges and anomalous magnetic moments. In contrast to the
magnetic field value of 10^19 G, obtained when anomalous magnetic moments are
not taken into account, we find the upper bound B < 8.6 x 10^17 G, for the
stability of the system. A phase transition could be hidden for fields greater
than this value.Comment: 9 pages, 9 figure
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