12 research outputs found
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
Production of pi+, pi-, K+, K-, p and p-bar in Light (uds), c and b Jets from Z0 Decays
We present improved measurements of the differential production rates of
stable charged particles in hadronic Z0 decays, and of charged pions, kaons and
protons identified over a wide momentum range using the SLD Cherenkov Ring
Imaging Detector. In addition to flavor-inclusive Z0 decays, measurements are
made for Z0 decays into light (u, d, s), c and b primary flavors, selected
using the upgraded Vertex Detector. Large differences between the flavors are
observed that are qualitatively consistent with expectations based upon
previously measured production and decay properties of heavy hadrons. These
results are used to test the predictions of QCD in the Modified Leading
Logarithm Approximation, with the ansatz of Local Parton-Hadron Duality, and
the predictions of three models of the hadronization process. The light-flavor
results provide improved tests of these predictions, as they do not include the
contribution of heavy-hadron production and decay; the heavy-flavor results
provide complementary model tests. In addition we have compared hadron and
antihadron production in light quark (as opposed to antiquark) jets.
Differences are observed at high momentum for all three charged hadron species,
providing direct probes of leading particle effects, and stringent constraints
on models.Comment: 44 pages, 14 figs; submitted to Phys. Rev.
A human monoclonal antibody obtained from EBV-transformed B cells with specificity for myosin
First measurement of the double inclusive B / anti-B hadron energy distribution in e+ e- annihilations, and of angle dependent moments of the B and anti-B energies
We have made the first measurement of the double-inclusive B/Bbar energy
distribution in e+e- annihilations, using a sample of 400,000 hadronic Z0 decay
events recorded in the SLD experiment at SLAC between 1996 and 1998. The small
and stable SLC beam spot and the CCD-based vertex detector were used to
reconstruct B/Bbar decay vertices with high efficiency and purity, and to
provide measurements of the kinematic quantities used to calculate the B
energies in this novel technique. We measured the B/Bbar energies with good
efficiency and resolution over the full kinematic range. We measured moments of
the scaled energies of the B and Bbar hadrons vs. the opening angle between
them. By comparing these results with perturbative QCD predictions we tested
the ansatz of factorisation in heavy-quark production. A recent next-to-leading
order calculation reproduces the data.Comment: 17 pages, 6 figures; submitted to Physics Letters
Guidelines for the use and interpretation of assays for monitoring autophagy
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field. © 2012 Landes Bioscience
Factorial and cumulant moments in e+ e- ---> hadrons at the Z0 resonance
We present the first experimental study of the ratio of cumulant to factorial
moments of the charged-particle multiplicity distribution in high-energy
particle interactions, using hadronic Z decays collected by the SLD
experiment at SLAC. We find that this ratio, as a function of the moment-rank
, decreases sharply to a negative minimum at , which is followed by
quasi-oscillations. These features are insensitive to experimental systematic
effects and are in qualitative agreement with expectations from
next-to-next-to-leading-order perturbative QCD.Comment: 13 pages, latex file, uuencoded eps figure