Fragmentation Region Research Articles

Fellgett Revisited: On the Nature of Noise in Two-Dimensional Mass Spectrometry.

Two-dimensional mass spectrometry (2DMS) is a truly data-independent acquisition technique used in the analysis of complex mixtures; however, the nature of the noise within these spectra is not well understood. In this work, 2DMS is tested for conformity with the Fellgett principle: (signal/noise) ∝ √ (no. of data points). Since 2DMS functions through the modulation of ions through a fragmentation region across many scans, the individual scans are considered data points in this experiment. Random noise was shown to be prevalent as the main source of noise in this experiment with minor systematic noise. This means that the minimum size for a 2DMS spectrum that displays a target fragment ion can be determined using a fast-2D equation detailed herein. The effects of existing denoising algorithms were also found to change the relationship between the signal-to-noise ratio and the scan numbers to be of a quasi-linear nature rather than the square root trend observed before denoising.

Insect Mitochondrial Genomics: A Decade of Progress.

The past decade has seen the availability of insect genomic data explode, with mitochondrial (mt) genome data seeing the greatest growth. The widespread adoption of next-generation sequencing has solved many earlier methodological limitations, allowing the routine sequencing of whole mt genomes, including from degraded or museum specimens and in parallel to nuclear genomic projects. The diversity of available taxa now allows finer-scale comparisons between mt and nuclear phylogenomic analyses; high levels of congruence have been found for most orders, with some significant exceptions (e.g., Odonata, Mantodea, Diptera). The evolution of mt gene rearrangements and their association with haplodiploidy have been tested with expanded taxonomic sampling, and earlier proposed trends have been largely supported. Multiple model systems have been developed based on findings unique to insects, including mt genome fragmentation (lice and relatives) and control region duplication (thrips), allowing testing of hypothesized evolutionary drivers of these aberrant genomic phenomena. Finally, emerging research topics consider the contributions of mt genomes to insect speciation and habitat adaption, with very broad potential impacts. Integration between insect mt genomic research and other fields within entomology continues to be our field's greatest opportunity and challenge.

The connection between nucleon energy correlators and fracture functions

We establish a sum rule that connects fracture functions to nucleon energy-energy correlators (NEECs) in a one-to-one correspondence. Using this sum rule, we study the energy pattern in the target fragmentation region of deep inelastic scatterings. Through investigations up to twist-3, we express all eighteen energy-pattern structure functions in terms of associated NEECs, elucidating various azimuthal and spin asymmetries critical for nucleon tomography. Additionally, we investigate the perturbative matching of the twist-2 quark NEECs. We demonstrate that the Sivers-type and worm-gear-type quark NEECs match onto twist-3 multi-parton distributions. Our work provides a framework for examining energy-weighted observables through hadron production processes in the target fragmentation region, offering new insights into nucleon tomography.

Gluonic contributions to semi-inclusive DIS in the target fragmentation region

We study one-loop contributions to semi-inclusive deep inelastic scattering in the target fragmentation region for a polarized lepton beam and nucleon target. Complete one-loop results at leading twist are derived, with a particular focus on the gluonic channel. It shows that four structure functions are generated uniquely by the gluon fracture functions starting at one-loop. Additionally, we obtain two structure functions associated with the longitudinal polarization of the virtual photon, and they are contributed by both gluon and quark channels. By combining existing twist-3 results, all eighteen structure functions for the studied process are predicted in terms of fracture functions convoluted with perturbative coefficient functions.

Cellular and molecular alterations to muscles and neuromuscular synapses in a mouse model of MEGF10-related myopathy

Loss-of-function mutations in MEGF10 lead to a rare and understudied neuromuscular disorder known as MEGF10-related myopathy. There are no treatments for the progressive respiratory distress, motor impairment, and structural abnormalities in muscles caused by the loss of MEGF10 function. In this study, we deployed cellular and molecular assays to obtain additional insights about MEGF10-related myopathy in juvenile, young adult, and middle-aged Megf10 knockout (KO) mice. We found fewer muscle fibers in juvenile and adult Megf10 KO mice, supporting published studies that MEGF10 regulates myogenesis by affecting satellite cell differentiation. Interestingly, muscle fibers do not exhibit morphological hallmarks of atrophy in either young adult or middle-aged Megf10 KO mice. We next examined the neuromuscular junction (NMJ), in which MEGF10 has been shown to concentrate postnatally, using light and electron microscopy. We found early and progressive degenerative features at the NMJs of Megf10 KO mice that include increased postsynaptic fragmentation and presynaptic regions not apposed by postsynaptic nicotinic acetylcholine receptors. We also found perisynaptic Schwann cells intruding into the NMJ synaptic cleft. These findings strongly suggest that the NMJ is a site of postnatal pathology in MEGF10-related myopathy. In support of these cellular observations, RNA-seq analysis revealed genes and pathways associated with myogenesis, skeletal muscle health, and NMJ stability dysregulated in Megf10 KO mice compared to wild-type mice. Altogether, these data provide new and valuable cellular and molecular insights into MEGF10-related myopathy.

Bjorken x weighted energy-energy correlators from the target fragmentation region to the current fragmentation region

We present the complete spectrum for the Bjorken x weighted energy-energy correlation in the deep inelastic scattering (DIS) process, from the target fragmentation region to the current fragmentation region, in the Breit frame. The corresponding collinear and transverse momentum-dependent logarithms are resummed to all orders with the accuracy of NLL and N3LL, respectively. The results in the full region are matched with an O(αs2) fixed-order calculation. The final numerical predictions are presented for both Electron-Ion Collider and Continuous Electron Beam Accelerator Facility kinematics. Published by the American Physical Society 2024

A Pathway for Collisional Planetesimal Growth in the Ice-dominant Regions of Protoplanetary Disks

We present a semi-analytic model for the growth, drift, desorption, and fragmentation of millimeter- to meter-sized particles in protoplanetary disks. Fragmentation occurs where particle collision velocities exceed critical fragmentation velocities. Using this criterion, we produce fragmentation regions in disk orbital radius–particle size phase space for particles with a range of material properties, structures, and compositions (including SiO2, Mg2SiO4, H2O, CO2, and CO). For reasonable disk conditions, compact aggregate H2O, CO2, and CO ice particles do not reach destructive relative velocities and are thus not likely to undergo collisional fragmentation. Uncoated silicate particles are more susceptible to collisional destruction and are expected to fragment in the inner disk, consistent with previous work. We then calculate the growth, drift, and sublimation of small particles, initially located in the outer disk. We find that ice-coated particles can avoid fragmentation as they grow and drift inward under a substantial range of disk conditions, as long as the particles are aggregates composed of 0.1 μm-sized monomers. Such particles may undergo runaway growth in disk regions abundant in H2O or CO2 ice, depending on the assumed disk temperature structure. These results indicate that icy collisional growth to planetesimally relevant sizes may happen efficiently throughout a disk’s lifetime, and is particularly robust at early times when the disk’s dust-to-gas ratio is comparable to that of the interstellar medium.

Twist-3 contributions in semi-inclusive DIS in the target fragmentation region

Twist-3 contributions in semi-inclusive DIS in the target fragmentation region

Production of Δ0 resonances in the target and projectile fragmentation regions in p+12C and d+12C collisions at 4.2 GeV/c per nucleon

Production of Δ0 resonances in the target and projectile fragmentation regions in p+12C and d+12C collisions at 4.2 GeV/c per nucleon

Gluon radiation from a classical point particle: recoil effects

The gluon radiation spectrum of a classical particle struck by a sheet of colored glass, is a key ingredient in understanding the distribution of energy and baryon density in the fragmentation region, particularly in the initial stages of heavy ion collisions. However, the currently known classical spectrum has a troublesome high-momentum tail (Kajantie et al. in Phys. Rev. D 100(5):054011, 2019; Phys Rev D 101(5):054012, 2020). By comparing tree-level bremsstrahlung of a spin-less quark to the above-mentioned known result, we propose an interpolating formula that takes into account the recoil of the struck particle, and therefore produces the correct perturbative behaviour at high momentum of the radiated gluon.

AGTML: A novel approach to land cover classification by integrating automatic generation of training samples and machine learning algorithms on Google Earth Engine

The timely, accurate, and automatic acquisition of land cover (LC) information is a prerequisite for detecting LC dynamics and performing ecological analyses. Cloud computing platforms, such as the Google Earth Engine, have substantially improved the efficiency and scale of LC classification. However, the lack of sufficient and representative training samples hinders automatic and accurate LC classification. In this study, we propose a new approach that integrates the automatic generation of training samples and machine learning algorithms (AGTML) for LC classification in Heilongjiang Province, China. After optimal focal radii were determined for different LC types using Landsat 8 based on focal statistics and unique phenology. Then target training samples were automatically generated based on the improved distance measure SED (a composite of Spectral angle distance (SAD) and Euclidean distance (ED)). Furthermore, LC classification was performed using four feature combinations and three machine learning algorithms. According to independent validation data, the automatically generated training samples demonstrated good representativeness and stability among all three classifiers, with an overall accuracy (OA) of classification higher than 86%, and showed high consistency in the landscape pattern of classification. RF yielded the highest classification accuracy (92.99% OA). AGTML outperformed GLC-FCS30 in identifying large fragmentation and small patch regions in the landscape types. The AGTML approach was subsequently applied to the Guanzhong Plain using different satellite imagery. Results were consistent and accurate (>96.50% OA), demonstrating that the AGTML approach can be applied to various regions and sensors, and has immense potential for automated LC classification across regional and global scales.

Search for a three-proton resonance state in d+12C, α+12C and 12C+12C collisions at 3.37AGeV

The new experimental results on the search and study of formation of a possible three-proton resonance state in a target fragmentation region in the total ensemble of collisions of deuterons (2H), [Formula: see text]-particles (4He), and carbon-12 nuclei with target carbon-12 nuclei at incident kinetic energy 3.37[Formula: see text]GeV per nucleon are presented. The narrow peak structure of a possible three-proton resonance state was observed with a four-sigma statistical significance in the spectrum of invariant masses of three protons in the analyzed ensemble of collisions in the collision events with four protons in the final state. The peak structure was not visible in the other channels with the number of protons equal 3, 5, and [Formula: see text]. The mass and width of this possible three-proton resonance state were estimated to be [Formula: see text][Formula: see text]MeV/[Formula: see text] and [Formula: see text][Formula: see text]MeV/[Formula: see text]. The inclusive cross-section of formation of this possible resonance state was estimated to be [Formula: see text][Formula: see text]mb. It was deduced that the three-proton resonances could possibly be formed as a result of capture by a two-proton resonance (with mass [Formula: see text][Formula: see text]MeV/[Formula: see text]) of one more proton with a close velocity. The observed three-proton as well as two-proton resonances are likely to be the hadronic molecules. Taking into account an alpha cluster structure of carbon-12 nuclei, one of the possible mechanisms of formation of three-proton resonances could be the effective fusing of pair of protons with opposite spins, from one fragmenting alpha cluster, with a proton, originating from the second fragmenting alpha cluster.

Instanton induced spin–spin correlations

The QCD instanton can be observed at relatively low energies at Nica collider by studying the spin-spin correlations between the incoming proton and the produced Lambda or Sigma hyperons (or the Lambda and bar{Lambda } hyperons). Low Nica energy will allow to better record and to measure the polarization of the hyperon originated by the polarized valence quark(s) in the proton fragmentation region.

Production of Cumulative Pions and Percolation of Strings

Production of pions in high-energy collisions with nuclei in the kinematics prohibited for free nucleons (“cumulative pions”) is studied in the fusing color string model. The model describes the so-called direct mechanism for cumulative production. The other (spectator) mechanism dominates in production of cumulative protons, and is suppressed for pions. In the model, cumulative pions are generated by string fusion, which raises the maximal energy of produced partons above the level of the free nucleon kinematics. Momentum and multiplicity sum rules are used to determine the spectra in the deep fragmentation region. Predicted spectra of cumulative pions exponentially fall with the scaling variable x in the interval 1<x<3 with a slope between 5.1 and 5.6, which agrees well with the raw data obtained in the recent experiment at RHIC involving Cu–Au collisioins. However, the agreement is worse for the so-called unfolded data, presumably taking into account corrections due to the experimental setup and having rather a power-like form.

First Measurement of Λ Electroproduction off Nuclei in the Current and Target Fragmentation Regions.

We report results of Λ hyperon production in semi-inclusive deep-inelastic scattering off deuterium, carbon, iron, and lead targets obtained with the CLAS detector and the Continuous Electron Beam Accelerator Facility 5.014GeV electron beam. These results represent the first measurements of the Λ multiplicity ratio and transverse momentum broadening as a function of the energy fraction (z) in the current and target fragmentation regions. The multiplicity ratio exhibits a strong suppression at high z and an enhancement at low z. The measured transverse momentum broadening is an order of magnitude greater than that seen for light mesons. This indicates that the propagating entity interacts very strongly with the nuclear medium, which suggests that propagation of diquark configurations in the nuclear medium takes place at least part of the time, even at high z. The trends of these results are qualitatively described by the Giessen Boltzmann-Uehling-Uhlenbeck transport model, particularly for the multiplicity ratios. These observations will potentially open a new era of studies of the structure of the nucleon as well as of strange baryons.

Origin of Resonant Character in the Electron Impact Two-Body Neutral-Fragmentation of Methane.

The observation of peaks in the threshold region of two-body neutral fragmentation of methane molecule, i. e., CH4 →CH3 +H, by low energy electron (LEE) impact has been an enigma. The prevailing explanation that this resonant behavior is due to excitation energy transfer is unsatisfactory since this process is not expected to show peaks in the cross-sections unless there is the involvement of electron-molecule resonances. Our first-principles calculations now reveal that the observed peaks could be explained as due to the formation of negative ion resonances, which dominantly dissociate into two neutral fragments and a free-electron. This case of methane is a pointer to the possibility that such reactions contribute significantly to neutral radical production from molecules by LEE impact in comparison to dissociative electron attachment, and in general could play a significant role in electron-based chemical control.

Matching of fracture functions for SIDIS in target fragmentation region

In the target fragmentation region of Semi-Inclusive Deep Inelastic Scattering, the diffractively produced hadron has small transverse momentum. If it is at order of ΛQCD, it prevents to make predictions with the standard collinear factorization. However, in this case, differential cross-sections can be predicted by the factorization with fracture functions, diffractive parton distributions. If the transverse momentum is much larger than ΛQCD but much smaller than Q which is the virtuality of the virtual photon, both factorizations apply. In this case, fracture functions can be factorized with collinear parton distributions and fragmentation functions. We study the factorization up to twist-3 level and obtain gauge invariant results. They will be helpful for modeling fracture functions and useful for resummation of large logarithm of the transverse momentum appearing in collinear factorization.

Δ0 (1232) production in n+12C collisions at 4.2GeV/c

For the first time, the production of [Formula: see text] (1232) resonances has been analyzed in minimum bias [Formula: see text]C collisions at 4.2[Formula: see text]GeV/[Formula: see text]. The value of the mass and width of the [Formula: see text] resonances as well as the fraction of the negative pions coming from [Formula: see text] decay obtained in this work in [Formula: see text]C collisions coincide within the uncertainties with those extracted earlier in [Formula: see text]C collisions at 4.2[Formula: see text]GeV/[Formula: see text] per nucleon. The inclusive cross-section for production of [Formula: see text] (1232) resonances in [Formula: see text]C collisions at 4.2[Formula: see text]GeV/[Formula: see text] is estimated to be [Formula: see text][Formula: see text]mb. Production of [Formula: see text] resonances in [Formula: see text]C collisions at 4.2[Formula: see text]GeV/[Formula: see text] has been investigated separately in regions of fragmentation of the target and projectile. The mass of the [Formula: see text] (1232) proved to be the same within the statistical errors in the target and projectile fragmentation regions. The width of the invariant mass spectrum of [Formula: see text] excited in the projectile region proved to be considerably larger than that in the target fragmentation region, coinciding within statistical errors with that obtained in collisions of free nucleons. The results of the previous experiments, in which production of [Formula: see text] resonances is investigated in the whole phase space (without separating the target and projectile fragmentation regions), can be approximately regarded as the mean values of [Formula: see text] parameters, averaged over those in the target and projectile fragmentation regions.

Deep inelastic scattering as a probe of entanglement: Confronting experimental data

Parton distributions can be defined in terms of the entropy of entanglement between the spatial region probed by deep inelastic scattering (DIS) and the rest of the proton. For very small $x$, the proton becomes a maximally entangled state. This approach leads to a simple relation $S = \ln N $ between the average number $N$ of color-singlet dipoles in the proton wave function and the entropy of the produced hadronic state $S$. At small $x$, the multiplicity of dipoles is given by the gluon structure function, $N = x G(x,Q^2)$. Recently, the H1 Collaboration analyzed the entropy of the produced hadronic state in DIS, and studied its relation to the gluon structure function; poor agreement with the predicted relation was found. In this letter we argue that a more accurate account of the number of color-singlet dipoles in the kinematics of H1 experiment (where hadrons are detected in the current fragmentation region) is given not by $xG(x,Q^2)$ but by the sea quark structure function $x\Sigma(x,Q^2)$. Sea quarks originate from the splitting of gluons, so at small $x$ $x\Sigma(x,Q^2)\,\sim\, xG(x,Q^2)$, but in the current fragmentation region this proportionality is distorted by the contribution of the quark-antiquark pair produced by the virtual photon splitting. In addition, the multiplicity of color-singlet dipoles in the current fragmentation region is quite small, and one needs to include $\sim 1/N$ corrections to $S= \ln N$ asymptotic formula. Taking both of these modifications into account, we find that the data from the H1 Collaboration in fact agree well with the prediction based on entanglement.

Experimental and numerical study on fragmentation mechanism of copper sheet in laser dynamic forming

The fragmentation mechanism of copper sheet in laser dynamic forming (LDF) process is investigated. The investigation of the fragmentation mechanism in the moving sample is quite difficult, so finite element method is adopted to provide detailed information on the stress state during micro-forming. The shock loading was generated using laser-shock-rubber loading technique in which a layer of rubber is inserted to improve laser shock efficiency. When laser power density is 0.491 GW cm−2, the obvious circular fragmentation is located at the center region of rear surface. When laser power density is 0.658 GW cm−2, the diameter of the fragmentation region increased, and what’s more, circumferential and radial cracks were formed in the fragmentation region. The void linkages and terrace-like pattern were also observed. Finite element model reveals that the fragmentation in the moving sheet is not caused by the initial rubber direct loading, but the deceleration at the last stage of forming. Because the curvature in the tip has the highest value at the stopping point, deceleration passes through its maximum value and then causes fragmentation at the last stage of forming. When laser power density is 0.658 GW cm−2, the single layer fragmentation, multiple layer fragmentation, circumferential crack, and radial cracks occur in that sequence.