27,382 research outputs found
The Experiment Road to the Heavier Quarks and Other Heavy Objects
After a brief history of heavy quarks, I will discuss charm, bottom, and top
quarks in turn. For each one, I discuss its first observation, and then what we
have learned about production, hadronization, and decays - and what these have
taught us about the underlying physics. I will also point out remaining open
issues. For this series of lectures, the charm quark will be emphasized. It is
the first of the heavy quarks, and its study is where many of the techniques
and issues first appeared. Only very brief mention is made of CP violation in
the bottom-quark system since that topic is the subject of a separate series of
lectures by Gabriel Lopez. As the three quarks are reviewed, a pattern of
techniques and lessons emerges. These are identified, and then briefly
considered in the context of anticipated physics signals of the future; e.g.,
for Higgs and SUSY particles.Comment: From three lectures at the "IX Escuela de Particulas y Campos" in
Metepec, Mexico - August, 2000. 30 pages, 5 figures Revised version with
spelling/grammar corrections and clearer figur
LHC Symposium 2003: Summary Talk
This summary talk reviews the LHC 2003 Symposium, focusing on expectations as
we prepare to leap over the current energy frontier into new territory. We may
learn from what happened in the two most recent examples of leaping into new
energy territory. Quite different scenarios appeared in those two cases. In
addition, we review the status of the machine and experiments as reported at
the Symposium. Finally, I suggest an attitude which may be most appropriate as
we look forward to the opportunities anticipated for the first data from the
LHC.Comment: Summary Talk: LHC Symposium, May 1-3, 2003, Fermilab, Batavia, IL US
Charm Results on CP Violation and Mixing
The most recent results on CP violation and mixing in the charm system are
reviewed as a guide to the future. While no surprising results are reported so
far, charm provides a unique window to physics beyond the Standard Model. The
results reported here come from four sources: ALEPH at LEP, E791 and FOCUS/E831
at Fermilab, and CLEO II.V at CESR. Results beyond these sources may be
expected as a byproduct of B-motivated experiments.Comment: 17 pages,including 4 figures, Workshop on Physics and Detectors for
Daphne, Frascati, Italy, November 16-19, 199
Future Hadron Physics at Fermilab
Today, hadron physics research occurs at Fermilab as parts of broader
experimental programs. This is very likely to be the case in the future. Thus,
much of this presentation focuses on our vision of that future - a future aimed
at making Fermilab the host laboratory for the International Linear Collider
(ILC). Given the uncertainties associated with the ILC - the level of needed
R&D, the ILC costs, and the timing - Fermilab is also preparing for other
program choices. I will describe these latter efforts, efforts focused on a
Proton Driver to increase the numbers of protons available for experiments. As
examples of the hadron physics which will be coming from Fermilab, I summarize
three experiments: MIPP/E907 which is running currently, and MINER A and
Drell-Yan/E906 which are scheduled for future running periods. Hadron physics
coming from the Tevatron Collider program will be summarized by Arthur Maciel
in another talk at Hadron05.Comment: To be published in the Proceedings of the XI International Conference
on Hadron Spectroscopy (Alberto Reis, editor) in the AIP Conference
Proceedings series, 10 page
Toward a language theoretic proof of the four color theorem
This paper considers the problem of showing that every pair of binary trees
with the same number of leaves parses a common word under a certain simple
grammar. We enumerate the common parse words for several infinite families of
tree pairs and discuss several ways to reduce the problem of finding a parse
word for a pair of trees to that for a smaller pair. The statement that every
pair of trees has a common parse word is equivalent to the statement that every
planar graph is four-colorable, so the results are a step toward a language
theoretic proof of the four color theorem.Comment: 18 pages, many images; final versio
Reduced purities as measures of decoherence in many-electron systems
A hierarchy of measures of decoherence for many-electron systems that is
based on the purity and the hierarchy of reduced electronic density matrices is
presented. These reduced purities can be used to characterize electronic
decoherence in the common case when the many-body electronic density matrix is
not known and only reduced information about the electronic subsystem is
available. Being defined from reduced electronic quantities, the interpretation
of the reduced purities is more intricate than the usual (many-body) purity.
This is because the nonidempotency of the -body reduced electronic density
matrix that is the basis of the reduced purity measures can arise due to
decoherence or due to electronic correlations. To guide the interpretation,
explicit expressions are provided for the one-body and two-body reduced
purities for a general electronic state. Using them, the information content
and structure of the one-body and two-body reduced purities is established, and
limits on the changes that decoherence can induce are elucidated. The practical
use of the reduced purities to understand decoherence dynamics in many-electron
systems is exemplified through an analysis of the electronic decoherence
dynamics in a model molecular system.Comment: 10 pages, 3 figure
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