Observation of a $$ {\varLambda}_b^0 $$ − $$ {\overline{\varLambda}}_b^0 $$ production asymmetry in proton-proton collisions at $$ \sqrt{s} $$ = 7 and 8 TeV

This article presents differential measurements of the asymmetry between $$ {\varLambda}_b^0 $$ Λ b 0 and $$ {\overline{\varLambda}}_b^0 $$ Λ ¯ b 0 baryon production rates in proton-proton collisions at centre-of-mass energies of $$ \sqrt{s} $$ s = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb−1. The $$ {\varLambda}_b^0 $$ Λ b 0 baryons are reconstructed through the inclusive semileptonic decay $$ {\varLambda}_b^0 $$ Λ b 0 → $$ {\varLambda}_c^{+} $$ Λ c + μ−$$ \overline{\nu} $$ ν ¯ μX. The production asymmetry is measured both in intervals of rapidity in the range 2.15 < y < 4.10 and transverse momentum in 2 < pT< 27 GeV/c. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both $$ \sqrt{s} $$ s = 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in Pythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b-hadron production at LHC energies.

Converging Evidence of Underlying Competence: Comprehension and Production in the Acquisition of Spanish Subject-Verb Agreement

A surprising comprehension-production asymmetry in subject-verb (SV) agreement acquisition has been suggested in the literature, and recent research indicates that task-specific as well as language-specific features may contribute to this apparent asymmetry across languages. The present study investigates when during development children acquiring Mexican Spanish gain competence with 3rd-person SV agreement, testing production as well as comprehension in the same children aged between 3;6 and 5;7 years, and whether comprehension of SV agreement is modulated by the sentential position of the verb (i.e., medial vs. final position). Accuracy and sensitivity analyses show that comprehension performance correlates with SV agreement production abilities, and that comprehension of singular and plural third-person forms is not influenced by the sentential position of the agreement morpheme. Issues of the appropriate outcome measure and the role of structural familiarity in the development of abstract representations are discussed.

Evaluation of Power Production Asymmetry during Cycling in Persons with Multiple Sclerosis

Lower limb asymmetries have been observed in persons with multiple sclerosis (PwMS), and have been associated with mobility impairment. An incremental cycling test was performed on a cycle ergometer to determine peak power output (PPO) and peak oxygen consumption (VO2peak). Then, participants cycled at 50%, 60%, and 70% of their PPO to assess the contribution of each lower limb to power production. Two-way repeated measures ANOVA was used to detect group × intensity differences in power production asymmetry. Eight PwMS and six healthy individuals (Non-MS) completed the study. No statistically significant (p > 0.05) group × intensity interactions or main effects were present when examining between-limb differences in power production. The current data do not indicate a statistically significant difference in power production asymmetry between groups and exercise intensities. Previous research has established a 10% difference between contralateral limbs as a threshold for asymmetry. The average asymmetry in power production in PwMS exceeded the 10% threshold at all measured outputs, suggesting the presence of asymmetry in power production.

Production asymmetry of open charm mesons within unfavoured ragmentation scenario

We consider unfavoured light quark/antiquark to D meson fragmentation. We discuss nonperturbative effects for small transverse momenta. The asymmetry for D+ and D- production measured by the LHCb collaboration provides natural constraints on the parton (quark/antiquark) fragmentation functions. We find that already a fraction of $q/\overline q \to D$ fragmentation probability is sufficient to account for the measured asymmetry. Large D-meson production asymmetries are found for large xF which is related to dominance of light quark/antiquark $q/\overline q \to D$ fragmentation over the standard c → D fragmentation. As a consequence, prompt atmospheric neutrino flux at high neutrino energies can be much larger than for the conventional c → D fragmentation. The latter can constitute a sizeable background for the cosmic neutrinos claimed to be observed recently by the IceCube Observatory.