Baryons in a soft-wall AdS-Schwarzschild approach at low temperature

Recently we derived a soft-wall anti–de Sitter-Schwarzschild approach at small temperatures for the description of hadrons with integer spin and adjustable number of constituents (mesons, tetraquarks, dibaryons, etc.). In the present paper we extend our formalism to states with half-integer spin (baryons, pentaquarks, etc.), presenting analytical results for the temperature dependence of their masses and form factors

The Importance of Bottlenecks in Protein Networks: Correlation with Gene Essentiality and Expression Dynamics

It has been a long-standing goal in systems biology to find relations between the topological properties and functional features of protein networks. However, most of the focus in network studies has been on highly connected proteins (“hubs”). As a complementary notion, it is possible to define bottlenecks as proteins with a high betweenness centrality (i.e., network nodes that have many “shortest paths” going through them, analogous to major bridges and tunnels on a highway map). Bottlenecks are, in fact, key connector proteins with surprising functional and dynamic properties. In particular, they are more likely to be essential proteins. In fact, in regulatory and other directed networks, betweenness (i.e., “bottleneck-ness”) is a much more significant indicator of essentiality than degree (i.e., “hub-ness”). Furthermore, bottlenecks correspond to the dynamic components of the interaction network—they are significantly less well coexpressed with their neighbors than nonbottlenecks, implying that expression dynamics is wired into the network topology

Search for a Hypothetical 16.7 MeV Gauge Boson and Dark Photons in the NA64 Experiment at CERN

We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e+e− pairs observed in the excited 8Be∗ nucleus decays. Because of its coupling to electrons, the X could be produced in the bremsstrahlung reaction e−Z→e−ZX by a 100 GeV e−beam incident on an active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through the subsequent decay into a e+e− pair. With 5.4×1010 electrons on target, no evidence for such decays was found, allowing us to set first limits on the X−e− coupling in the range 1.3×10−4≲εe≲4.2×10−4 excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A′) from nonobservation of the decay A′→e+e−of the bremsstrahlung A′ with a mass ≲23  MeV

Search for vector mediator of dark matter production in invisible decay mode

A search is performed for a new sub-GeV vector boson (A′) mediated production of dark matter (χ) in the fixed-target experiment, NA64, at the CERN SPS. The A′, called dark photon, can be generated in the reaction e−Z→e−ZA′ of 100 GeV electrons dumped against an active target followed by its prompt invisible decay A′→χ¯χ. The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to 4.3×1010 electrons on target no evidence of such a process has been found. New stringent constraints on the A′ mixing strength with photons, 10−5≲ε≲10−2, for the A′ mass range mA′≲1  GeV are derived. For models considering scalar and fermionic thermal dark matter interacting with the visible sector through the vector portal the 90% C.L. limits 10−11≲y≲10−6on the dark-matter parameter y=ε2αD(mχmA′)4 are obtained for the dark coupling constant αD=0.5and dark-matter masses 0.001≲mχ≲0.5  GeV. The lower limits αD≳10−3 for pseudo-Dirac dark matter in the mass region mχ≲0.05  GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using exact tree level calculations of the A′production cross sections, which turn out to be significantly smaller compared to the one obtained in the Weizsäcker-Williams approximation for the mass region mA′≳0.1  Ge

Improved exclusion limit for light dark matter from e+e− annihilation in NA64

The current most stringent constraints for the existence of sub-GeV dark matter coupling to Standard Model via a massive vector boson A′ were set by the NA64 experiment for the mass region mA′≲250  MeV, by analyzing data from the interaction of 2.84×1011 100-GeV electrons with an active thick target and searching for missing-energy events. In this work, by including A′ production via secondary positron annihilation with atomic electrons, we extend these limits in the 200-300 MeV region by almost an order of magnitude, touching for the first time the dark matter relic density constrained parameter combinations. Our new results demonstrate the power of the resonant annihilation process in missing energy dark-matter searches, paving the road to future dedicated e+ beam efforts

Search for pseudoscalar bosons decaying into e+e− pairs in the NA64 experiment at the CERN SPS

We report the results of a search for a light pseudoscalar particle a that couples to electrons and decays to e+e− performed using the high-energy CERN SPS H4 electron beam. If such light pseudoscalar exists, it could explain the ATOMKI anomaly (an excess of e+e− pairs in the nuclear transitions of 8Be and 4He nuclei at the invariant mass ≃17  MeV observed by the experiment at the 5 MV Van de Graaff accelerator at ATOMKI, Hungary). We used the NA64 data collected in the “visible mode” configuration with a total statistics corresponding to 8.4×1010 electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter ε we also used the data collected in 2016-2018 in the “invisible mode” configuration of NA64 with a total statistics corresponding to 2.84×1011 EOT. The background and efficiency estimates for these two configurations were retained from our previous analyses searching for light vector bosons and axionlike particles (ALP) (the latter were assumed to couple predominantly to γ). In this work we recalculate the signal yields, which are different due to different cross section and lifetime of a pseudoscalar particle a, and perform a new statistical analysis. As a result, the region of the two dimensional parameter space ma−ε in the mass range from 1 to 17.1 MeV is excluded. At the mass of the central value of the ATOMKI anomaly (the first result obtained on the beryllium nucleus, 16.7 MeV) the values of ε in the range 2.1×10−4<ε<3.2×10−4 are excluded

Organizational Heterogeneity of Vertebrate Genomes

Genomes of higher eukaryotes are mosaics of segments with various structural, functional, and evolutionary properties. The availability of whole-genome sequences allows the investigation of their structure as “texts” using different statistical and computational methods. One such method, referred to as Compositional Spectra (CS) analysis, is based on scoring the occurrences of fixed-length oligonucleotides (k-mers) in the target DNA sequence. CS analysis allows generating species- or region-specific characteristics of the genome, regardless of their length and the presence of coding DNA. In this study, we consider the heterogeneity of vertebrate genomes as a joint effect of regional variation in sequence organization superimposed on the differences in nucleotide composition. We estimated compositional and organizational heterogeneity of genome and chromosome sequences separately and found that both heterogeneity types vary widely among genomes as well as among chromosomes in all investigated taxonomic groups. The high correspondence of heterogeneity scores obtained on three genome fractions, coding, repetitive, and the remaining part of the noncoding DNA (the genome dark matter - GDM) allows the assumption that CS-heterogeneity may have functional relevance to genome regulation. Of special interest for such interpretation is the fact that natural GDM sequences display the highest deviation from the corresponding reshuffled sequences

Type-directed continuation allocation

Abstract. Suppose we translate two different source languages, £¥ ¤ and £§ ¦ , into the same intermediate language; can they safely interoperate in the same address space and under the same runtime system? If £ ¤ supports first-class continuations (call/cc) and £ ¦ does not, can £ ¦ programs call arbitrary £ ¤ functions? Would the fact of possibly calling £¨ ¤ impose restrictions on the implementation strategy of £ ¦ ? Can we compile £ ¤ functions that do not invoke call/cc using more efficient techniques borrowed from the £ ¦ implementation? Our view is that the implementation of a common intermediate language ought to support the so-called pay-as-you-go efficiency: first-order monomorphic functions should be compiled as efficiently as in C and assembly languages, even though they may be passed to arbitrary polymorphic functions that support advanced control primitives (e.g. call/cc). In this paper, we present a typed intermediate language with effect and resource annotations, ensuring the safety of inter-language calls while allowing the compiler to choose continuation allocation strategies.