2,136 research outputs found
Single-top-quark production via q qbar -> t bbar
We consider single-top-quark production via the weak process at hadron colliders. This process may provide the best measurement of
the magnitude of the Cabbibo-Kobayashi-Maskawa matrix element . We show
that a signal can potentially be observed at the Fermilab Tevatron with 3
of integrated luminosity. In contrast, the signal is masked at the
CERN Large Hadron Collider by top-quark pair production and single-top-quark
production via -gluon fusion.Comment: 12 pages latex + 5 uuencoded figure
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Visual Analytics for Understanding Spatial Situations from Episodic Movement Data
Continuing advances in modern data acquisition techniques result in rapidly growing amounts of geo-referenced data about moving objects and in emergence of new data types. We define episodic movement data as a new complex data type to be considered in the research fields relevant to data analysis. In episodic movement data, position measurements may be separated by large time gaps, in which the positions of the moving objects are unknown and cannot be reliably reconstructed. Many of the existing methods for movement analysis are designed for data with fine temporal resolution and cannot be applied to discontinuous trajectories. We present an approach utilizing Visual Analytics methods to explore and understand the temporal variation of spatial situations derived from episodic movement data by means of spatio-temporal aggregation. The situations are defined in terms of the presence of moving objects in different places and in terms of flows (collective movements) among the places. The approach, which combines interactive visual displays with clustering of the spatial situations, is presented by example of a real dataset collected by Bluetooth sensors
Standard Model Higgs Physics at a 4 TeV Upgraded Tevatron
We compute an array of Standard Model Higgs boson (\hsm) signals and
backgrounds for a possible upgrade of the Tevatron to E_{\rm cm}=4\tev.
Taking \mt\geq 140\gev, and assuming a total accumulated luminosity of
L=30\fbi, we find that a Standard Model Higgs boson with \mhsm\lsim 110\gev
could almost certainly be detected using the \wpm\hsm\rta l\nu b\anti b mode.
A Higgs boson with mass between \sim 120\gev and \sim 140\gev or above
\sim 230-250\gev almost certainly would not be seen. A Higgs boson with
\mhsm\sim 150\gev or 200\lsim\mhsm\lsim 230-250\gev has a decent chance of
being detected in the ZZ\rta 4l mode. There would also be some possibility of
discovering the \hsm in the WW\rta l\nu jj mode for 150\lsim\mhsm\lsim
200\gev. Finally, hints of an event excess in the WW\rta ll \nu\nu mode due
to the \hsm might emerge for 140\lsim\mhsm\lsim 180\gev. Given the
difficult nature of the Higgs boson signals for \mhsm values beyond the reach
of LEP-200, and the discontinuous \mhsm range that could potentially be
probed, justification of an upgrade of the Tevatron to 4\tev on the basis of
its potential for Standard Model Higgs boson discovery would seem
inappropriate.Comment: 21 pages; requires phyzzx.tex and tables.tex; full postscript file
including embedded figures available via anonymous ftp at ucdhep.ucdavis.edu
as [anonymous.gunion]4tev.ps, preprint UCD-94-1
QCD and Yukawa corrections to single-top-quark production via q qbar -> t bbar
We calculate the O(alpha_s) and O(alpha_W m_t^2/M_W^2) corrections to the
production of a single top quark via the weak process q qbar -> t bbar at the
Fermilab Tevatron and the CERN Large Hadron Collider. An accurate calculation
of the cross section is necessary in order to extract |V_tb| from experiment.Comment: LaTeX, 13 pages, replaced with version to appear in Phys. Rev.
A double parton scattering background to Higgs boson production at the LHC
The experimental capability of recognizing the presence of b quarks in
complex hadronic final states has addressed the attention towards final states
with b\bar{b} pairs for observing the production of the Higgs boson at the LHC,
in the intermediate Higgs mass range.We point out that double parton scattering
processes are going to represent a sizeable background to the process.Comment: 9 pages, 2 figure
Anomalous Higgs Couplings
We review the effects of new effective interactions on the Higgs boson
phenomenology. New physics in the electroweak bosonic sector is expected to
induce additional interactions between the Higgs doublet field and the
electroweak gauge bosons leading to anomalous Higgs couplings as well as to
anomalous gauge-boson self-interactions. Using a linearly realized invariant effective Lagrangian to describe the bosonic sector of
the Standard Model, we review the effects of the new effective interactions on
the Higgs boson production rates and decay modes. We summarize the results from
searches for the new Higgs signatures induced by the anomalous interactions in
order to constrain the scale of new physics in particular at CERN LEP and
Fermilab Te vatron colliders.Comment: 35 pages, latex using epsfig.sty psfig.sty and axodraw.sty, 16
postscript figure
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Ultrafast modulation of the chemical potential in BaFe2As2 by coherent phonons
Time- and angle-resolved extreme ultraviolet photoemission spectroscopy is used to study the electronic structure dynamics in BaFe2As2 around the high-symmetry points Πand M. A global oscillation of the Fermi level at the frequency of the A1g(As) phonon mode is observed. It is argued that this behavior reflects a modulation of the effective chemical potential in the photoexcited surface region that arises from the high sensitivity of the band structure near the Fermi level to the A1g(As) phonon mode combined with a low electron diffusivity perpendicular to the layers. The results establish a novel way to tune the electronic properties of iron pnictides: coherent control of the effective chemical potential. The results further suggest that the equilibration time for the effective chemical potential needs to be considered in the ultrafast electronic structure dynamics of materials with weak interlayer coupling. © 2014 American Physical Society
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