1,936 research outputs found
Recent Tests of QCD at SLD
We present selected results on strong interaction physics from the SLD
experiment at the SLAC Linear Collider. We report on several new studies of 3-
and 4-jet hadronic Z decays, in which jets are identified as quark, antiquark
or gluon. The 3-jet Z^0->b\bar{b}g rate is sensitive to the b-quark mass;
prospects for measuring m_b are discussed. The gluon energy spectrum is
measured over the full kinematic range, providing an improved test of QCD and
limits on anomalous bbg couplings. The parity violation in Z^0->b\bar{b}g
decays is consistent with electroweak theory plus QCD. New tests of T- and
CP-conservation at the bbg vertex are performed. A new measurement of the rate
of gluon splitting into b\bar{b} pairs yields
g_{b\bar{b}}=0.0031+-0.0007(stat.)+-0.0006(syst.) (Preliminary). We also
present a number of new results on jet fragmentation into identified hadrons.
The B hadron energy spectrum is measured over the full kinematic range using a
new, inclusive technique, allowing stringent tests of predictions for its shape
and a precise measurement of =0.714+-0.005(stat.)+-0.007(syst.)
(Preliminary). A detailed study of correlations in rapidity y between pairs of
identified pions, kaons and protons confirms that strangeness and baryon number
are conserved locally, and shows local charge conservation between meson-baryon
and strange-nonstrange pairs. Flavor-dependent long-range correlations are
observed for all combinations of these hadron species, yielding new information
on leading particle production. The first study of correlations using
rapidities signed such that y>0 corresponds to the quark direction provides
additional new insights into fragmentation, including the first direct
observation of baryon number ordering along the q\bar{q} axis.Comment: 20 pages, 12 figs.; talk given at the QCD99 meeting, Montpellier,
France, 7-13 July, 1999; a smaller-print version will appear in the
proceeding
Introduction to Collider Physics
This is a set of four lectures presented at the Theoretical Advanced Study
Institute (TASI-09) in June 2009. The goal of the lectures is to introduce
students to some of the basic ideas and tools required for theoretical analysis
of collider data. Several examples of Standard Model processes at
electron-positron and hadron colliders are considered to illustrate these
ideas. In addition, a general strategy for formulating searches for physics
beyond the Standard Model is outlined. The lectures conclude with a brief
survey of recent, ongoing and future searches for the Higgs boson and
supersymmetric particles.Comment: 47 pages, 34 figures, contributed to TASI-09 proceedings. One
reference added in v
Heavy Quarkonium Physics
This report is the result of the collaboration and research effort of the
Quarkonium Working Group over the last three years. It provides a comprehensive
overview of the state of the art in heavy-quarkonium theory and experiment,
covering quarkonium spectroscopy, decay, and production, the determination of
QCD parameters from quarkonium observables, quarkonia in media, and the effects
on quarkonia of physics beyond the Standard Model. An introduction to common
theoretical and experimental tools is included. Future opportunities for
research in quarkonium physics are also discussed.Comment: xviii + 487 pages, 260 figures. The full text is also available at
the Quarkonium Working Group web page: http://www.qwg.to.infn.i
Review of Top Quark Physics
We present an overview of Top Quark Physics - from what has been learned so
far at the Tevatron, to the searches that lie ahead at present and future
colliders. We summarize the richness of the measurements and discuss their
possible impact on our understanding of the Standard Model by pointing out
their key elements and limitations. When possible, we discuss how the top quark
may provide a connection to new or unexpected physics.Comment: 84 pp. With permission from the Annual Review of Nuclear & Particle
Science. Final version of this material is scheduled to appear in the Annual
Review of Nuclear & Particle Science Vol. 53, to be published in December
2003 by Annual Reviews (http://www.annualreviews.org
The Physics of Hadronic Tau Decays
Hadronic tau decays represent a clean laboratory for the precise study of
quantum chromodynamics (QCD). Observables (sum rules) based on the spectral
functions of hadronic tau decays can be related to QCD quark-level calculations
to determine fundamental quantities like the strong coupling constant,
parameters of the chiral Lagrangian, |V_us|, the mass of the strange quark, and
to simultaneously test the concept of quark-hadron duality. Using the best
available measurements and a revisited analysis of the theoretical framework,
the value alpha_s(m_tau) = 0.345 +- 0.004[exp] +- 0.009[theo] is obtained.
Taken together with the determination of alpha_s(m_Z) from the global
electroweak fit, this result leads to the most accurate test of asymptotic
freedom: the value of the logarithmic slope of 1/alpha_s(s) is found to agree
with QCD at a precision of 4%. In another approach, the tau spectral functions
can be used to determine hadronic quantities that, due to the nonperturbative
nature of long-distance QCD, cannot be computed from first principles. An
example for this is the contribution from hadronic vacuum polarization to
loop-dominated processes like the anomalous magnetic moment of the muon. This
article reviews the measurements of nonstrange and strange tau spectral
functions and their phenomenological applications.Comment: 89 pages, 32 figures; final version accepted for publication by
Reviews of Modern Physic
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