4,645 research outputs found
Semileptonic tau decays, structure functions, kinematics and polarisation
The most general angular distribution of two or three meson final states from
semileptonic decays , , ,
, , , of polarized
leptons can be characterized by 16 structure functions. Predictions for
hadronic matrix elements, based on CVC and chiral Lagrangians and their
relations to the structure functions are discussed. Most of them can be
determined in currently ongoing high statistics experiments. Emphasis of the
kinematical analysis is firstly put on decays in
experiments where the neutrino escapes detection and the rest frame
cannot be reconstructed. Subsequently it is shown, how the determination of
hadron tracks in double semileptonic events allows to fully reconstruct the
kinematics. The implications for the spin analysis are indicated.Comment: 12 pages, LaTeX (uses epsf.sty, 3 ps-figures appended as extra
uuencoded file) The complete paper, including figures, is also available via
anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ttp94-27/ttp94-27.ps,
or via www at http://ttpux2.physik.uni-karlsruhe.de/preprints.htm
Exotic Bound State Production at Hadron Colliders
Hadronic production of nonrelativistic boundstates of or
isosinglet quarks D with suppressed weak decays is investigated for LHC and SSC
energies. QCD corrections to production and decay rates are incorporated. Large
rates for final states from are predicted.Comment: 7 pages and 13 figures (figures not includes, can be sent upon
request), TTP93-1
Electroweak effects in top-quark pair production at Hadron Colliders
Top-quark physics plays an important role at hadron colliders such as the
Tevatron collider at Fermilab or the upcoming Large Hadron Collider (LHC) at
CERN. Given the planned experimental precision, detailed theoretical
predictions are mandatory. In this article we present analytic results for the
complete electroweak corrections to gluon induced top-quark pair production,
completing our earlier results for the quark-induced reaction. As an
application we discuss top-quark pair production at Tevatron and at LHC. In
particular we show that, although small for inclusive quantities, weak
corrections can be sizeable for differential distribution
CP Violation in Semileptonic Decays with Unpolarized Beams
CP violating signals in semileptonic decays are studied. These can be
observed in decays of unpolarized single 's even if their rest frame
cannot be reconstructed. No beam polarization is required. The importance of
the two meson channel, in particular the final state is emphasized.Comment: Latex, 17 pages, 2 figures. The complete paper, including figures, is
also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ ,
or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints
Electroweak corrections and anomalous triple gauge-boson couplings in WW and WZ production at the LHC
We have analysed the production of WW and WZ vector-boson pairs at the LHC.
These processes give rise to four-fermion final states, and are particularly
sensitive to possible non-standard trilinear gauge-boson couplings. We have
studied the interplay between the influence of these anomalous couplings and
the effect of the complete logarithmic electroweak O(\alpha) corrections.
Radiative corrections to the Standard Model processes in double-pole
approximation and non-standard terms due to trilinear couplings are implemented
into a Monte Carlo program for p p -> 4f (+\gamma) with final states involving
four or two charged leptons. We numerically investigate purely leptonic final
states and find that electroweak corrections can fake new-physics signals,
modifying the observables by the same amount and shape, in kinematical regions
of statistical significance.Comment: 19 pages, LaTex, 12 eps figure
QCD Corrections to Toponium Production at Hadron Colliders
Toponium production at future hadron colliders is investigated. Perturbative
QCD corrections to the production cross section for gluon fusion are calculated
as well as the contributions from gluon-quark and quark-antiquark collisions to
the total cross section. The dependence on the renormalization and
factorization scales and on the choice of the parton distribution functions is
explored. QCD corrections to the branching ratio of into
are included and the two-loop QCD potential is used to predict
the wave function at the origin. The branching ratio of into , , and is compared with the channel.Comment: 16 pages (latex) 9 figures (postscript) available upon request,
TTP92-3
Variational study of U(1) and SU(2) lattice gauge theories with Gaussian states in 1+1 dimensions
We introduce a method to investigate the static and dynamic properties of
both Abelian and non-Abelian lattice gauge models in 1+1 dimensions.
Specifically, we identify a set of transformations that disentangle different
degrees of freedom, and apply a simple Gaussian variational ansatz to the
resulting Hamiltonian. To demonstrate the suitability of the method, we analyze
both static and dynamic aspects of string breaking for the U(1) and SU(2) gauge
models. We benchmark our results against tensor network simulations and observe
excellent agreement, although the number of variational parameters in the
Gaussian ansatz is much smaller.Comment: 19 pages, 6 figures. Added references and corrected typo
Transport of dipolar Bose-Einstein condensates in a one-dimensional optical lattice
We show that magnetic dipolar interactions can stabilize superfluidity in
atomic gases but the dipole alignment direction required to achieve this
varies, depending on whether the flow is oscillatory or continuous. If a
condensate is made to oscillate through a lattice, damping of the oscillations
can be reduced by aligning the dipoles perpendicular to the direction of
motion. However, if a lattice is driven continuously through the condensate,
superfluid behavior is best preserved when the dipoles are aligned parallel to
the direction of motion. We explain these results in terms of the formation of
topological excitations and tunnel barrier heights between lattice sites.Comment: 6 pages, 7 figure
Gaussian states for the variational study of (1+1)-dimensional lattice gauge models
We introduce a variational ansatz based on Gaussian states for
(1+1)-dimensional lattice gauge models. To this end we identify a set of
unitary transformations which decouple the gauge degrees of freedom from the
matter fields. Using our ansatz, we study static aspects as well as real-time
dynamics of string breaking in two (1+1)-dimensional theories, namely QED and
two-color QCD. We show that our ansatz captures the relevant features and is in
excellent agreement with data from numerical calculations with tensor networks.Comment: 7 pages, 2 figures, proceedings of the 36th Annual International
Symposium on Lattice Field Theory, 22-28 July, 2018 Michigan State
University, East Lansing, Michigan, US
Electroweak corrections to W-boson pair production at the LHC
Vector-boson pair production ranks among the most important Standard-Model
benchmark processes at the LHC, not only in view of on-going Higgs analyses.
These processes may also help to gain a deeper understanding of the electroweak
interaction in general, and to test the validity of the Standard Model at
highest energies. In this work, the first calculation of the full one-loop
electroweak corrections to on-shell W-boson pair production at hadron colliders
is presented. We discuss the impact of the corrections on the total cross
section as well as on relevant differential distributions. We observe that
corrections due to photon-induced channels can be amazingly large at energies
accessible at the LHC, while radiation of additional massive vector bosons does
not influence the results significantly.Comment: 29 pages, 15 figures, 4 tables; some references and comments on
\gamma\gamma -> WW added; matches version published in JHE
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