11 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
A Bayesian approach for determining protein side-chain rotamer conformations using unassigned NOE data
Abstract. A major bottleneck in protein structure determination via nuclear magnetic resonance (NMR) is the lengthy and laborious process of assigning resonances and nuclear Overhauser effect (NOE) cross peaks. Recent studies have shown that accurate backbone folds can be determined using sparse NMR data, such as residual dipolar couplings (RDCs) or backbone chemical shifts. This opens a question of whether we can also determine the accurate protein sidechain conformations using sparse or unassigned NMR data. We attack this question by using unassigned nuclear Overhauser effect spectroscopy (NOESY) data, which record the through-space dipolar interactions between protons nearby in 3D space. We propose a Bayesian approach with a Markov random field (MRF) model to integrate the likelihood function derived from observed experimental data, with prior information (i.e., empirical molecular mechanics energies) about the protein structures. We unify the side-chain structure prediction problem with the side-chain structure determination problem using unassigned NMR data, and apply the deterministic dead-end elimination (DEE) and A * search algorithms t
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