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3,753 result(s) for "Yuan, C. Z."
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Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the B -factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations at BESIII, the LHC, RHIC, FAIR, the Super Flavor and/or Tau–Charm factories, JLab, the ILC, and beyond. The list of newly found conventional states expanded to include h c (1 P ), χ c 2 (2 P ), , and  η b (1 S ). In addition, the unexpected and still-fascinating X (3872) has been joined by more than a dozen other charmonium- and bottomonium-like “ XYZ ” states that appear to lie outside the quark model. Many of these still need experimental confirmation. The plethora of new states unleashed a flood of theoretical investigations into new forms of matter such as quark–gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of , , and bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. Lattice QCD has grown from a tool with computational possibilities to an industrial-strength effort now dependent more on insight and innovation than pure computational power. New effective field theories for the description of quarkonium in different regimes have been developed and brought to a high degree of sophistication, thus enabling precise and solid theoretical predictions. Many expected decays and transitions have either been measured with precision or for the first time, but the confusing patterns of decays, both above and below open-flavor thresholds, endure and have deepened. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark–gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.
Risk of hip fracture following stroke, a meta-analysis of 13 cohort studies
This study systematically reviews prospective and retrospective cohort studies evaluating the risk of hip fracture following stroke. Stroke survivors are at high risk of hip fracture and had a 1.5-fold increased risk compared to stroke-free men and women of the same age. Hip fracture often occurs in ageing and female stroke patients. We performed a meta-analysis to summarize evidence from prospective and retrospective cohort studies about the risk of hip fracture following stroke. We identified English and non-English publications in MEDLINE and EMBASE using stroke and fracture as keywords to 31 December 2015. The data of the incidence of hip fracture were extracted to calculate raw incident rate in stroke survivors as well as risk of hip fractures in strokes comparing populations using a random-effects model. Subgroup analyses were performed to identify the potential influence of some factors. Six prospective and seven retrospective cohort studies were included, involving 512,214 stroke patients with 22,559 hip fractures. The pooled prevalence of hip fractures was 4.87 % (95 % CI, 4.05 to 5.68 %) in stoke patients. We conducted subgroup analysis according to sex, age, duration of follow-up, study design, and region, which showed that female (vs. male) stroke patients older than 70 years (vs. those less than 70 years) and duration of follow-up more than 2 years (vs. those less than 2 years) have higher proportions of hip fractures. Four studies showed that stroke patients had a significantly higher risk of hip fracture compared with the general population, while the other study had a non-significant higher risk. The overall prevalence of hip fracture was 3.28 % (3431 of 104,646) in stroke patients and 2.83 % (36,493 of 1,287,726) in general population, respectively, and the unadjusted combined relative risk of hip fracture was 1.54 (95 % CI, 1.06–2.25). Hip fractures often occur in ageing and female stroke patients.
Reevaluation of the hadronic contribution to the muon magnetic anomaly using new e+e−→π+π− cross section data from BABAR
Using recently published, high-precision π + π − cross section data by the BABAR experiment from the analysis of e + e − events with high-energy photon radiation in the initial state, we reevaluate the lowest order hadronic contribution to the anomalous magnetic moment of the muon. We employ newly developed software featuring improved data interpolation and averaging, more accurate error propagation and systematic validation. With the new data, the discrepancy between the e + e − - and τ -based results for the dominant two-pion mode reduces from previously 2.4 σ to 1.5 σ in the dispersion integral, though significant local discrepancies in the spectra persist. We obtain for the e + e − -based evaluation , where the error accounts for all sources. The full Standard Model prediction of a μ differs from the experimental value by 3.2 σ .
Quest for precision in hadronic cross sections at low energy: Monte Carlo tools vs. experimental data
We present the achievements of the last years of the experimental and theoretical groups working on hadronic cross section measurements at the low-energy e + e − colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on τ decays. We sketch the prospects in these fields for the years to come. We emphasise the status and the precision of the Monte Carlo generators used to analyse the hadronic cross section measurements obtained as well with energy scans as with radiative return, to determine luminosities and τ decays. The radiative corrections fully or approximately implemented in the various codes and the contribution of the vacuum polarisation are discussed.
The discrepancy between τ and e+e− spectral functions revisited and the consequences for the muon magnetic anomaly
We revisit the procedure for comparing the π π spectral function measured in  τ decays to that obtained in e + e − annihilation. We re-examine the isospin-breaking corrections using new experimental and theoretical input and find improved agreement between the τ − → π − π 0 ν τ branching fraction measurement and its prediction using the isospin-breaking-corrected e + e − → π + π − spectral function, though not resolving all discrepancies. We recompute the lowest order hadronic contributions to the muon g −2 using e + e − and τ data with the new corrections and find a reduced difference between the two evaluations. The new tau-based estimate of the muon magnetic anomaly is found to be 1.9 standard deviations lower than the direct measurement.
Update of the ALEPH non-strange spectral functions from hadronic tau decays
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) An update of the ALEPH non-strange spectral functions from hadronic ... decays is presented. Compared to the 2005 ALEPH publication, the main improvement is related to the use of a new method to unfold the measured mass spectra from detector effects. This procedure also corrects a previous problem in the correlations between the unfolded mass bins. Results from QCD studies and for the evaluation of the hadronic vacuum polarisation contribution to the anomalous muon magnetic moment are derived using the new spectral functions. They are found in agreement with published results based on the previous set of spectral functions.
Thermo- and pH-sensitive behavior of hydrogels based on oligo (ethylene glycol) methacrylates and acrylic acid
Novel dual stimuli-responsive hydrogels were prepared by free-radical polymerization of 2-(2-methoxyethoxy) ethyl methacrylate (MEO 2 MA) and oligo (ethylene glycol) methacrylate (OEGMA), as thermosensitive monomers, and acrylic acid (AAc), as a pH-sensitive monomer. Due to the thermosensitive monomers introduced in the macromolecular network, the synthesized materials possessed tunable thermal behavior. In addition, as well as by introducing in the polymerization feed pH-sensitive monomer AAc, the equilibrium swelling properties of the hydrogels can be tuned by three comonomers. Moreover, the de-swelling kinetics was studied by changing temperature and/or pH, and they could be well described with a first-order kinetics equation. Especially, the faster shrinking rates of hydrogels were observed when the simultaneous temperature and pH stimuli changed from pH 8/18 to pH 2/55 °C because of the cooperative thermo-/pH responses. The prepared dual temperature-/pH-sensitive PMOA hydrogels as a new material candidate may provide significant valuable information for various potential applications.
Effects of corn type and fasting time before slaughter on growth and plasma index in weaning pigs
A 2 × 2 factorial experiment was conducted to evaluate the effects of dietary corn type (waxy corn [WC] vs. nonwaxy corn [NC]) and fasting period (2 h vs. 12-16 h) before slaughter on growth and plasma index in weaning pigs. Twenty-four crossbred barrows (8.26 ± 0.47 kg) were allotted to 4 treatments with 6 replications of 1 pig per replicate metabolism cage. Waxy corn contained less fat, a lower amylase:amylopectin ratio, more CP, and more starch than NC. Pigs fed the WC diet had lower jejunum digesta pH compared with those fed the NC diet ( < 0.05). Maltase activity in the jejunum and ileum mucosa ( < 0.01), sucrose activity in the ileum mucosa ( < 0.01), and amylase activity in the pancreas and jejunum digesta ( < 0.05) were increased in pigs fed the WC diet relative to those fed the NC diet. But the total tract apparent digestibility (TTAD) of starch and CP was lower for the WC group ( < 0.05). Ingestion of the NC diet resulted in higher ( < 0.05) ADG and ADFI in the second week but did not affect ADG ( = 0.091) and the feed:gain ratio (F:G; = 0.077) during the whole experiment period. The plasma glucose ( < 0.01) concentration was higher and high-density lipoprotein cholesterol (HDL-C; < 0.01) concentrations was lower in the hepatic portal vein in pigs fed the WC diet relative to those fed the NC diet. Fasting 2 h before slaughter decreased the jejunum and ileum digesta pH compared with the 12-h fasting group ( < 0.01). Villus height increased in the duodenum ( < 0.01) and jejunum ( < 0.05) and the villus height:crypt depth ratio increased in the duodenum ( < 0.05) of pigs after shortening the fasting period before slaughter. Shortening the fasting time before slaughter resulted in higher plasma glucose ( < 0.05) concentrations and a higher HDL-C:low-density lipoprotein cholesterol (LDL-C) ratio ( < 0.05) whereas the LDL-C ( < 0.05) concentrations were reduced in the hepatic portal vein. The results of this experiment indicate that although the production performance of both WC and NC diets is equal, the glucose concentration is higher and HDL-C is lower in the portal vein for the WC diet, and fasting time before slaughter has an influence on the plasma index and intestinal morphology in weaning pigs.
Update of the ALEPH non-strange spectral functions from hadronic τ decays
An update of the ALEPH non-strange spectral functions from hadronic τ decays is presented. Compared to the 2005 ALEPH publication, the main improvement is related to the use of a new method to unfold the measured mass spectra from detector effects. This procedure also corrects a previous problem in the correlations between the unfolded mass bins. Results from QCD studies and for the evaluation of the hadronic vacuum polarisation contribution to the anomalous muon magnetic moment are derived using the new spectral functions. They are found in agreement with published results based on the previous set of spectral functions.
Test of lepton flavor universality and search for lepton flavor violation in B → Kℓℓ decays
A bstract We present measurements of the branching fractions for the decays B → Kμ + μ − and B → Ke + e − , and their ratio ( R K ), using a data sample of 711 fb − 1 that contains 772 × 10 6 B B ¯ events. The data were collected at the ϒ(4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. The ratio R K is measured in five bins of dilepton invariant-mass-squared ( q 2 ): q 2 ∈ (0 . 1 , 4 . 0) , (4 . 00 , 8 . 12) , (1 . 0 , 6 . 0), (10 . 2 , 12 . 8) and ( > 14 . 18) GeV 2 /c 4 , along with the whole q 2 region. The R K value for q 2 ∈ (1 . 0 , 6 . 0) GeV 2 /c 4 is 1.03 − 0.24 + 0.28 ± 0 . 01. The first and second uncertainties listed are statistical and systematic, respectively. All results for R K are consistent with Standard Model predictions. We also measure CP -averaged isospin asymmetries in the same q 2 bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q 2 ∈ (1 . 0 , 6 . 0) GeV 2 /c 4 bin in the mode with muon final states. The measured differential branching fractions, d ℬ /dq 2 , are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B → Kμ ± e ∓ decays and set 90% confidence-level upper limits on the branching fraction in the range of 10 − 8 for B + → K + μ ± e ∓ , and B 0 → K 0 μ ± e ∓ modes.