266 research outputs found
SUSY-QCD corrections in the squark-gluino sector
A status report is given of the calculations of next-to-leading-order ()
supersymmetric QCD corrections to the production of squarks and gluinos in
collisions. The implementation of these SUSY-QCD corrections
leads to more stable theoretical predictions and to a substantial increase of
the production cross-sections. In addition we give a discussion of the use of
the scheme for renormalizing the coupling constants in the QCD
sector of () supersymmetric theories.Comment: 6 two-column pages, tar'ed gzip'ed uuencoded files, LaTeX, 7
Encapsulated Postscript figures, uses epsfig and espcrc2. To appear in the
proceedings of the 1996 Zeuthen Workshop on Elementary Particle Theory: "QCD
and QED in Higher Orders", J.Bl\"umlein, F.Jegerlehner, and T.Riemann eds.
Complete postscript file available at
http://rulgm4.LeidenUniv.nl/preprints.htm
Scalar one-loop integrals for QCD
We construct a basis set of infra-red and/or collinearly divergent scalar
one-loop integrals and give analytic formulas, for tadpole, bubble, triangle
and box integrals, regulating the divergences (ultra-violet, infra-red or
collinear) by regularization in dimensions. For scalar triangle
integrals we give results for our basis set containing 6 divergent integrals.
For scalar box integrals we give results for our basis set containing 16
divergent integrals. We provide analytic results for the 5 divergent box
integrals in the basis set which are missing in the literature. Building on the
work of van Oldenborgh, a general, publicly available code has been
constructed, which calculates both finite and divergent one-loop integrals. The
code returns the coefficients of and
as complex numbers for an arbitrary tadpole, bubble, triangle or box integral.Comment: 27 pages, 5 figures, associated fortran code available at
http://qcdloop.fnal.gov/. New version corrects typographical error in Eq. 5.
Stop decays in SUSY-QCD
The partial widths are determined for stop decays to top quarks and gluinos,
and gluino decays to stop particles and top quarks (depending on the masses of
the particles involved). The widths are calculated including one-loop SUSY-QCD
corrections. The radiative corrections for these strong-interaction decays are
compared with the SUSY-QCD corrections for electroweak stop decays to quarks
and neutralinos/charginos and top-quark decays to stops and neutralinos.Comment: 20 pages, LaTeX, 8 figures (uses epsfig). Complete postscript file
available at http://rulgm4.LeidenUniv.nl/preprints.htm
Gluon Radiation Off Scalar Stop Particles
We present the distributions for gluon radiation off stop-antistop particles
produced in annihilation: . For
high energies the splitting functions of the fragmentation processes and are derived; they are
universal and apply also to high-energy stop particles produced at hadron
colliders.Comment: 9 pages, 2 figures as uuencoded ps files, Latex, uses epsfig,
complete postscript version at
ftp://x4u2.desy.de/pub/preprints/desy/1994/desy94-235.p
Degenerate Photons from a Cryogenic Spontaneous Parametric Down-Conversion Source
We demonstrate the generation of degenerate photon pairs from spontaneous
parametric down-conversion in titanium in-diffused waveguides in lithium
niobate at cryogenic temperatures. Since the phase-matching cannot be
temperature tuned inside a cryostat, we rely on a precise empirical model of
the refractive indices when fabricating a fixed poling period. We design the
phase-matching properties of our periodic poling to enable signal and idler
photons at (1559.3 0.6) nm, and characterize the indistinguishability of
our photons by performing a Hong-Ou-Mandel interference measurement. Despite
the effects of photorefraction and pyroelectricity, which can locally alter the
phase-matching, we achieve cryogenic indistinguishable photons within 1.5 nm to
our design wavelength. Our results verify sufficient understanding and control
of the cryogenic nonlinear process, which has wider implications when combining
quasi-phase-matched nonlinear optical processes with other cryogenic photonic
quantum technologies, such as superconducting detectors.Comment: 7 pages, 6 figure
Towards integrated superconducting detectors on lithium niobate waveguides
Superconducting detectors are now well-established tools for low-light
optics, and in particular quantum optics, boasting high-efficiency, fast
response and low noise. Similarly, lithium niobate is an important platform for
integrated optics given its high second-order nonlinearity, used for high-speed
electro-optic modulation and polarization conversion, as well as frequency
conversion and sources of quantum light. Combining these technologies addresses
the requirements for a single platform capable of generating, manipulating and
measuring quantum light in many degrees of freedom, in a compact and
potentially scalable manner. We will report on progress integrating tungsten
transition-edge sensors (TESs) and amorphous tungsten silicide superconducting
nanowire single-photon detectors (SNSPDs) on titanium in-diffused lithium
niobate waveguides. The travelling-wave design couples the evanescent field
from the waveguides into the superconducting absorber. We will report on
simulations and measurements of the absorption, which we can characterize at
room temperature prior to cooling down the devices. Independently, we show how
the detectors respond to flood illumination, normally incident on the devices,
demonstrating their functionality.Comment: 7 pages, 4 figure
SUSY-QCD Decays of Squarks and Gluinos
The partial widths are determined for squark decays to gluinos and quarks,
and gluino decays to squarks and quarks, respectively. The widths are
calculated including one-loop SUSY-QCD corrections. The corrections amount to
30\% to 50\% for squark decays and 10\% to 10\% for gluino decays.
We have derived the results in the \DR ~and \MS ~renormalization schemes, and
we have demonstrated explicitly that the one-loop effective and q\sq\gl
couplings are equal in the limit of exact supersymmetry.Comment: 11 pages, Latex2e, 2 figures (uses epsfig). Complete postscript file
available at http://www.desy.de/pub/preprints/desy/1996/desy96-022.p
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