Direct measurements of Ab and Ac using vertex and kaon charge tags at the SLAC detector.

Exploiting the manipulation of the SLAC Linear Collider electron-beam polarization, we present precise direct measurements of the parity-violation parameters A(c) and A(b) in the Z-boson-c-quark and Z-boson-b-quark coupling. Quark-antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLAC Large Detector charge coupled device vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-1998 sample of 400 000 Z decays, produced with an average beam polarization of 73.4%, we find A(c)=0.673+/-0.029(stat)+/-0.023(syst) and A(b)=0.919+/-0.018(stat)+/-0.017(syst).

Improved direct measurement of the parity-violation parameter Ab using a mass tag and momentum-weighted track charge.

We present an improved direct measurement of the parity-violation parameter A(b) in the Z boson-b-quark coupling using a self-calibrating track-charge technique applied to a sample enriched in Z-->bb events via the topological reconstruction of the B hadron mass. Manipulation of the Stanford Linear Collider electron-beam polarization permits the measurement of A(b) to be made independently of other Z-pole coupling parameters. From the 1996-1998 sample of 400,000 hadronic Z decays, produced with an average beam polarization of 73.4%, we find A(b)=0.906+/-0.022(stat)+/-0.023(syst).

Improved direct measurement of A(b) and A(c) at the Z(0) pole using a lepton tag.

The parity violation parameters A(b) and A(c) of the Zb(b) and Zc(c) couplings have been measured directly, using the polar angle dependence of the polarized cross sections at the Z(0) pole. Bottom and charmed hadrons were tagged via their semileptonic decays. Both the electron and muon analyses take advantage of new multivariate techniques to increase the analyzing power. Based on the 1993-1998 SLD sample of 550,000 Z(0) decays produced with highly polarized electron beams, we measure A(b) = 0.919+/-0.030(stat)+/-0.024(syst), and A(c) = 0.583+/-0.055(stat)+/-0.055(syst).

First symmetry tests in polarized Z0 decays to bbg.

We have made the first direct symmetry tests in the decays of polarized Z0 bosons into fully identified bbg states, collected in the SLD experiment at SLAC. We searched for evidence of parity violation at the bbg vertex by studying the asymmetries in the b-quark polar- and azimuthal-angle distributions, and for evidence of T-odd, CP-even or CP-odd, final-state interactions by measuring angular correlations between the three-jet plane and the Z0 polarization. We found results consistent with standard model expectations and set 95% C. limits on anomalous contributions.

Improved direct measurement of leptonic coupling asymmetries with polarized Z bosons.

We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26.

High-precision measurement of the left-right Z Boson cross-section asymmetry.

We present a measurement of the left-right cross-section asymmetry ( A(LR)) for Z boson production by e(+)e(-) collisions. The measurement includes the final data taken with the SLD detector at the SLAC Linear Collider during the period 1996-1998. Using a sample of 383 487 Z decays collected during the 1996-1998 runs we measure the pole value of the asymmetry, A(0)(LR), to be 0.150 56+/-0.002 39 which is equivalent to an effective weak mixing angle of sin (2)straight theta(eff)(W) = 0.231 07+/-0.000 30. Our result for the complete 1992-1998 data set comprising approximately 537 000 Z decays is sin (2)straight theta(eff)(W) = 0.230 97+/-0.000 27.

Validity of DSM-IV subtypes of conduct disorder based on age of onset.

OBJECTIVE: To present data from the DSM-IV field trials that led to the distinction between subtypes of conduct disorder (CD) that emerge in childhood or adolescence. In addition, data from a household sample were used to attempt to cross-validate these findings. METHOD: Differences between youths who met criteria for the two subtypes of CD were examined in the field trials sample of 440 youths aged 4 through 17 years and in a household sample of 1,285 youths aged 9 through 17 years. RESULTS: In both samples, there was a steep decline in aggression occurring around an age of onset of 10 years, but the number of nonaggressive behaviors was unrelated to the age of onset of CD. In the field trials sample, youths who met criteria for the adolescent-onset type were more likely to be girls, less likely to meet criteria for oppositional defiant disorder, and less likely to have a family history of antisocial behavior than the childhood-onset type, but these latter findings were not confirmed in the household sample. CONCLUSIONS: The DSM-IV approach to subtyping CD distinguishes subgroups that differ markedly in level of physical aggression. The advantages of a developmental approach to subtyping are discussed.

Validity of the age-of-onset criterion for ADHD: a report from the DSM-IV field trials.

OBJECTIVE: To examine the validity of the DSM-IV requirement of an age of onset of impairment due to symptoms before 7 years of age for the diagnosis of attention-deficit/hyperactivity disorder (ADHD). METHOD: The validity of this criterion was examined in a clinic sample of 380 youths aged 4 through 17 years by comparing youths who met symptom criteria for ADHD and either did or did not display impairment before age 7 years. RESULTS: Nearly all youths who met symptom criteria for the predominantly hyperactive-impulsive subtype also met the age of onset of impairment criterion, but 18% of youths who met symptom criteria for the combined type, and 43% of youths who met symptom criteria for the predominantly inattentive type, did not manifest impairment before 7 years. For the latter two subtypes, requiring impairment before age 7 years reduced the accuracy of identification of currently impaired cases of ADHD and reduced agreement with clinicians' judgments. CONCLUSIONS: These findings raise questions about the validity of the DSM-IV definition of age of onset of ADHD. Marked differences in the ages of onset of both symptoms and impairment for the three subtypes of ADHD support the validity of distinguishing among these subtypes in DSM-IV.

Developmental change in attention-deficit hyperactivity disorder in boys: a four-year longitudinal study.

One hundred six clinic-referred boys meeting criteria for DSM-III-R attention-deficit hyperactivity disorder (ADHD) (mean age 9.4 years) were assessed annually for 4 years using structured interviews of multiple informants. Hyperactivity-impulsivity symptoms declined with increasing age, but inattention symptoms did not. Rather, inattention declined only from the first to the second assessment and remained stable thereafter in boys of all ages. The rate of decline in hyperactivity-impulsivity symptoms was independent of the amount and type of treatment received. Boys who still met criteria for ADHD in Years 3 and 4 were significantly younger, more hyperactive-impulsive, and more likely to exhibit conduct disorder in Year 1 than boys who no longer met criteria in Years 3 and 4.

Young boys who commit serious sexual offenses: demographics, psychometrics, and phenomenology.

This study reports on a population of early adolescent male sexual offenders 9 to 14 years of age compared with a clinic control group matched for age, sex, ethnic status, and the presence of a DSM-III-R conduct disorder. The sex offenders were found to exhibit a significant history of nonsexual antisocial behavior, physical and sexual abuse, and psychiatric comorbidity. The two groups did not differ in number and category of comorbid psychiatric diagnoses, the number of nonsexual aggressive and nonaggressive symptoms of conduct disorder, symptoms of major depressive disorder or dysthymia, and symptoms of anxiety disorders. The EGTC group demonstrated significantly lower mathematic achievement. There is evidence that sexual offending behavior in this population is one aspect of a pattern of antisocial behavior. Sixty-five percent of the index group had a history of early sexual victimization.

Anxiety, inhibition, and conduct disorder in children: II. Relation to salivary cortisol.

The relation of symptoms of conduct disorder (CD) and anxiety to salivary cortisol was explored in 67 clinic-referred boys aged 8 to 13 years. Children with anxiety disorder had higher levels of cortisol, but this main effect was qualified by a significant CD x anxiety disorder interaction. Consistent with Gray's biological model of the behavioral inhibition system (BIS), children with both CD and anxiety disorder had higher levels of salivary cortisol than children with CD without comorbid anxiety disorder. In the absence of CD, however, anxiety disorder was not clearly associated with higher cortisol. This result suggests that cortisol may be a useful biological marker of arousal associated with BIS activity in children with CD.