Flavour structure of low-energy hadron pair photoproduction

We consider the process $\gamma\gamma\to H_1\bar H_2$ where $H_1$ and $H_2$ are either mesons or baryons. The experimental findings for such quantities as the $p\bar p$ and $K_SK_S$ differential cross sections, in the energy range currently probed, are found often to be in disparity with the scaling behaviour expected from hard constituent scattering. We discuss the long-distance pole--resonance contribution in understanding the origin of these phenomena, as well as the amplitude relations governing the short-distance contribution which we model as a scaling contribution. When considering the latter, we argue that the difference found for the $K_SK_S$ and the $K^+K^-$ integrated cross sections can be attributed to the s-channel isovector component. This corresponds to the $\rho\omega\to a$ subprocess in the VMD (vector-meson-dominance) language. The ratio of the two cross sections is enhanced by the suppression of the $\phi$ component, and is hence constrained. We give similar constraints to a number of other hadron pair production channels. After writing down the scaling and pole--resonance contributions accordingly, the direct summation of the two contributions is found to reproduce some salient features of the $p\bar p$ and $K^+K^-$ data.Comment: 12 pages, 9 figures, revised version to be published in EPJ

Peculiarities of thermal expansion of quasi-two-dimensional organic conductor κ-(BEDT–TTF)₂Cu[N(CN)₂]Cl

Linear coefficient of thermal expansion α( T) of single crystal (BEDT–TTF)₂Cu[N(CN)₂]Cl was studied along the crystal layers using the method of precise capacitive dilatometry in the temperature range 2–285 K. It is positive in this direction over the entire temperature range. Anomalies of thermal expansion were observed at 29–30 K and 74–80 K. The anomaly near 30 K is, apparently, due to the transition between the paramagnetic phase and the antiferromagnetic insulator state. Peak of α( T) at 78 K corresponds to a phase transition related to orientational disordering of ethylene groups in dimers of BEDT–TTF. A broad maximum of α(T) in the temperature range 40–70 K, is apparently explained by fluctuations of charge within the dimers, and by spin fluctuations, which first increase with increasing temperature, and then decrease in process of thermal disordering of dimers

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. The plethora of newly-found quarkonium-like 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 c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. 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.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair

Discovery of widespread transcription initiation at microsatellites predictable by sequence-based deep neural network

Using the Cap Analysis of Gene Expression (CAGE) technology, the FANTOM5 consortium provided one of the most comprehensive maps of transcription start sites (TSSs) in several species. Strikingly, ~72% of them could not be assigned to a specific gene and initiate at unconventional regions, outside promoters or enhancers. Here, we probe these unassigned TSSs and show that, in all species studied, a significant fraction of CAGE peaks initiate at microsatellites, also called short tandem repeats (STRs). To confirm this transcription, we develop Cap Trap RNA-seq, a technology which combines cap trapping and long read MinION sequencing. We train sequence-based deep learning models able to predict CAGE signal at STRs with high accuracy. These models unveil the importance of STR surrounding sequences not only to distinguish STR classes, but also to predict the level of transcription initiation. Importantly, genetic variants linked to human diseases are preferentially found at STRs with high transcription initiation level, supporting the biological and clinical relevance of transcription initiation at STRs. Together, our results extend the repertoire of non-coding transcription associated with DNA tandem repeats and complexify STR polymorphism

Thermal expansion of organic superconductor κ-(D₄-BEDT-TTF)₂Cu{N(CN)₂}Br. Isotopic effect

Linear thermal expansion coefficient (LTEC) of single crystal κ-(D₄-BEDT-TTF)₂Cu[N(CN)₂]Br was studied across the crystal layers in the temperature range 2–290 K using the method of precise capacitive dilatometry. Below Tc = 11.6 K the LTEC of the sample had a small negative value, which is apparently due to the transition from the paramagnetic metal in the superconducting state. There was a bend of temperature dependence of the LTEC, which shows broad peak around 40 K and can be attributed to the elastic lattice anomaly around the end-point of Mott boundary. A sharp jump in the LTEC values and hysteresis was observed in the area of Tg ∼ 75–77 K, what is likely explained by the transition in a glass-like state. The isotope effect in the thermal expansion is discusses, which manifested itself in a shift of the phase transitions in comparison with fully deuterated BEDT-TTF sample

Thermal expansion of organic superconductor κ-(D₄-BEDT-TTF)₂Cu[N(CN)₂]Br. Isotopic effect

Linear thermal expansion coefficient (LTEC) of single crystal κ-(D₄-BEDT-TTF)₂Cu[N(CN)₂]Br was studied across the crystal layers in the temperature range 2–290 K using the method of precise capacitive dilatometry. Below Tc = 11.6 K the LTEC of the sample had a small negative value, which is apparently due to the transition from the paramagnetic metal in the superconducting state. There was a bend of temperature dependence of the LTEC, which shows broad peak around 40 K and can be attributed to the elastic lattice anomaly around the end-point of Mott boundary. A sharp jump in the LTEC values and hysteresis was observed in the area of Tg ~ 75–77 K, what is likely explained by the transition in a glass-like state. The isotope effect in the thermal expansion is discusses, which manifested itself in a shift of the phase transitions in comparison with fully deuterated BEDT-TTF sample

Thermal expansion of organic superconductor α-(BEDT-TTF)₂ NH₄Hg(SCN)₄

The temperature dependence of the linear thermal expansion coefficients (LTEC) of a single crystal of α-(BEDT-TTF)₂NH₄Hg(SCN)₄ where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene was studied by the method of precision capacitive dilatometry in the temperature range 2–250 K along the crystallographic direction b (perpendicular to the crystal layers). Negative values of LTEC were found below 4 K. Probably it is due to charge fluctuations as the temperature approaches the temperature of transition to the superconducting state Tc. It has been suggested that the bends on temperature dependence of LTEC observed in the temperature range 25–45 K are related to order-disorder arrangement of NH₄⁺ ions. Weak maximum of the LTEC, detected at a temperature of about 200–220 K, can be caused by the processes of charge redistribution and the associated intermolecular interaction fluctuations.Методом прецизійної ємнісної дилатометрії в температурному інтервалі 2–250 К досліджено температурну залежність коефіцієнтів лінійного теплового розширення (КЛТР) монокристала α-(BEDT-TTF)₂NH₄Hg(SCN)₄, де BEDT-TTF — біс(етілендітіо)тетратіафульвален, уздовж кристалографічного напрямку b (перпендикулярно до шарів кристалу). Нижче 4 К виявлено від'ємні значення КЛТР, ймовірно, обумовлені флуктуаціями заряду при наближенні температури вимірювань до температури переходу в надпровідний стан Тс. Висловлено припущення, що перегини температурної залежності КЛТР, які спостерігаються в температурному інтервалі 25–45 К, пов'язані з процесами упорядкування-розупорядкування NH₄⁺ іонів. Пагорбоподібна аномалія КЛТР, яка виявлена при температурі близько 200–220 К, може бути викликана процесами перерозподілу заряду та пов'язаними з ними флуктуаціями міжмолекулярної взаємодії.Методом прецизионной емкостной дилатометрии в температурном интервале 2–250 К исследована температурная зависимость коэффициентов линейного теплового расширения (КЛТР) монокристалла α-(BEDT-TTF)₂NH₄Hg(SCN)₄, где BEDT-TTF — бис(этилендитио)тетратиафульвален, вдоль кристаллографического направления b (перпендикулярно слоям кристалла). Ниже 4 К обнаружены отрицательные значения КЛТР, вероятно, обусловленные флуктуациями заряда при приближении температуры измерений к температуре перехода в сверхпроводящее состояние Тс. Высказано предположение, что наблюдаемые в температурном интервале 25–45 К перегибы температурной зависимости КЛТР связаны с процессами упорядочения-разупорядочения NH₄⁺ ионов. Холмообразная аномалия КЛТР, обнаруженная при температуре около 200– 220 К, может быть вызвана процессами перераспределения заряда и связанными с ними флуктуациями межмолекулярного взаимодействия

Significance of Claraia from the late permian of South Guizhou, China

Recently collecte material of two Claraia taxa, Claraia zhiyunica Yang et al, 2001 and Claraia sp. nov. from the Late Permian of South China, are described. Late Permian Claraia species are compared with those from the Early Triassic, and the survival of Claraia across the mass extinction period across the Permian- Triassic boundary (PTB) is discussed. <br /