Relative Momentum Research Articles

π+π− Coulomb interaction study and its use in data processing

In this work, the Coulomb effects (Coulomb correlations) in π+π− pairs produced in p+Ni collisions at 24 GeV/c, are studied using experimental π+π− pair distributions in Q, the relative momentum in the pair center-of-mass system (c.m.s.), and its projections QL (longitudinal component) and Qt (transverse component) relative to the pair direction in the laboratory system (LS). The major part of the pion pairs (“Coulomb pairs”) is produced in the decay of ρ, ω and Δ resonances and other short-lived sources. In these pairs, the significant Coulomb interaction occurs at small Q, dominating the π+π− interaction in the final state. The minor part of the pairs (“non-Coulomb pairs”) is produced if one or both pions arose from long-lived sources like η,η′ or from different interactions. In this case, the final state interaction is practically absent. The Q, QL, and Qt distributions of the Coulomb pairs in the c.m.s. have been simulated assuming they are described by the phase space modified by the known point-like Coulomb correlation function AC(Q), corrected for small effects due to the nonpointlike pair production and the strong two-pion interaction. The same distributions of non-Coulomb pairs have been simulated according to the phase space, but without AC(Q). In all Qt intervals, the experimental QL spectrum shows a peak around QL=0 caused by the Coulomb final state interaction. The full width at half maximum increases with Qt from 3 MeV/c for 0<Qt<0.25 MeV/c to 11 MeV/c for 4.0<Qt<5.0 MeV/c. The experimental QL distributions have been fitted with two free parameters: the fraction of Coulomb pairs and the normalization constant. The precision of the description of these distributions is better than 2% in Qt intervals 2–3, 3–4, and 4–5 MeV/c and better than 0.5% in the total Qt interval 0–5 MeV/c. It is shown that the number of Coulomb pairs in all Qt intervals, including the small Qt (small opening angles θ in the LS) is calculated with theoretical precision better than 2%. The comparison of the simulated and experimental numbers of Coulomb pairs at small Qt allows us to check and correct the detection efficiency for the pairs with small θ (0.06 mrad and smaller). It is shown that Coulomb pairs can be used as a new physical tool to check and correct the quality of the simulated events. The special property of the Coulomb pairs is the possibility of checking and correcting the detection efficiency, especially for the pairs with small opening angles. Published by the American Physical Society 2024

The public use of early-stage scientific advances in carbon dioxide removal: a science-technology-policy-media perspective

Abstract While Carbon Dioxide Removal (CDR) solutions are considered essential to meet Paris Agreement objectives and curb climate change, their maturity and current ability to operate at scale are highly debated. The rapid development, deployment, and diffusion of such methods will likely require the coordination of science, technology, policy, and societal support. This article proposes a bibliometric approach to quantify the public use of early-stage research in CDR. Specifically, we employ generalized linear models to estimate the likelihood that scientific advances in eight different carbon removal solutions may induce (i) further production of scientific knowledge, (ii) technological innovation, and (iii) policy and media discussion. Our main result is that research in CDR is of significant social value. CDR research generates significant, positive, yet heterogeneous spillovers within science and from science to technology, policy, and media. In particular, advances in Direct Air Capture spur further research and tend to result in patentable technologies, while Blue Carbon and Bio-energy with Carbon Capture and Storage appear to gain relative momentum in the policy and public debate. Moreover, scientific production and collaborations cluster geographically by type of CDR, potentially affecting long-term carbon removal strategies. Overall, our results suggest the existence of coordination gaps between science, technology, policy, and public support.

[formula omitted] and [formula omitted] two-particle femtoscopic correlations in PbPb collisions at [formula omitted]

Two-particle correlations are presented for KS0, ▪, and ▪ strange hadrons as a function of relative momentum in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The dataset corresponds to an integrated luminosity of 0.607nb−1 and was collected using the CMS detector at the CERN LHC. These correlations are sensitive to quantum statistics and to final-state interactions between the particles. The source size extracted from the KS0KS0 correlations is found to decrease from 4.6 to 1.6fm in going from central to peripheral collisions. Strong interaction scattering parameters (i.e., scattering length and effective range) are determined from the ▪ and ▪ (including their charge conjugates) correlations using the Lednický–Lyuboshitz model and are compared to theoretical and other experimental results.

Constraining bosonic dark matter-baryon interactions from neutron star collapse

Dark matter (DM) may be captured around a neutron star (NS) through DM-nucleon interactions. We observe that the enhancement of such capturing is particularly significant when DM-nucleon scattering cross-section depends on the relative velocity and/or momentum transfer. This increment could potentially lead to the formation of a black hole within the typical lifetime of the NS. As the black hole grows through the accretion of matter from the NS, it ultimately results in the collapse of the host. Utilizing the existing pulsar data J0437-4715 and J2124-3858, we derive the stringent constraints on the DM-nucleon scattering cross-section across a broad range of DM masses.

Relative, absolute or combined strength momentum strategies: what works for India?

Relative, absolute or combined strength momentum strategies: what works for India?

A new pairwise boost quantum number from celestial states

Infrared effects in the scattering of particles in gravity and electrodynamics entail an exchange of relativistic angular momentum between pairs of particles and the gauge field. Due to this exchange particles can carry an asymptotically non-vanishing “pairwise” boost-like angular momentum proportional to the product of their couplings to the field. At the quantum level this asymptotic angular momentum suggests the existence of a new quantum number carried by multi-particle states. We argue that such quantum number is related to a modification of the action of the generators of Lorentz transformations on multi-particle states. We derive such a modification using a group-theoretic argument based on the little group of the conformal primary basis for asymptotic states. The corresponding representation is an extension of the ordinary multi-particle Fock representation of the Poincaré group. The new multi-particle states belonging to such representation no longer factorize into tensor products of one-particle states. Viewed from a gravitational point of view, our results provide evidence for a universal breakdown of the description of multi-particle sates in terms of tensor products of one-particle states due to infrared back-reaction.

Space-Based Passive Orbital Maneuver Detection Algorithm for High-Altitude Situational Awareness

Orbital maneuver detection for non-cooperative targets in space is a key task in space situational awareness. This study develops a passive maneuver detection algorithm using line-of-sight angles measured by a space-based optical sensor, especially for targets in high-altitude orbit. Emphasis is placed on constructing a new characterization for maneuvers as well as the corresponding detection method. First, the concept of relative angular momentum is introduced to characterize the orbital maneuver of the target quantitatively, and the sensitivity of the proposed characterization is analyzed mathematically. Second, a maneuver detection algorithm based on the new characterization is designed in which sliding windows and correlations are utilized to determine the mutation of the maneuver characterization. Subsequently, a numerical simulation system composed of error models, reference missions and trajectories, and computation models for estimating errors is established. Then, the proposed algorithm is verified through numerical simulations for both long-range and close-range targets. The results indicate that the proposed algorithm is effective. Additionally, the sensitivity of the proposed algorithm to the width of the sliding window, accuracy of the optical sensor, magnitude and number of maneuvers, and different relative orbit types is analyzed, and the sensitivity of the new characterization is verified using simulations.

Application of the Pythagorean Theorem as a Quick Solution in Solving Relativistic Momentum Problems

The Pythagorean theorem is a fundamental concept in mathematics that is often used to solve various geometric problems. In physics studies, especially in relativistic momentum analysis, the application of this theorem can be a fast and effective solution. This article explores the application of the Pythagorean theorem in the context of relativistic momentum, where the speed and energy of objects approach the speed of light. By exploiting the quadratic relationship between the components of the relativistic momentum and energy vectors, the Pythagorean theorem allows for simpler and more efficient calculations. This research identifies the relationship between the Pythagorean theorem equation and the relativistic momentum equation through several steps. The first step involves calculating the Pythagorean theorem equation. The second step is to calculate Einstein's special relativity equations. The final step is to analyze the relationship between the two equations. In this case, the relativistic and Pythagorean momentum equations have similarities and one of the formulas can be used.

Intense Turbulent Bursts Promote the Release of Perfluoroalkyl Acids from Sediments at High Flow Velocity.

Despite frequent detection of high levels of perfluoroalkyl acids (PFAAs) in sediments, research on the environmental fate of PFAAs in sediments, particularly under hydrodynamic conditions, is rather limited, challenging effective management of PFAA loadings. Therefore, this study investigated the release and transport of 15 PFAAs in sediments under environmentally relevant flow velocities using recirculating flumes and revealed the underlying release mechanisms by identifying related momentum transfer. An increased velocity enhanced the release magnitude of total PFAAs by a factor of 3.09. The release capacity of short-chain PFAAs was notably higher than that of long-chain PFAAs, and this pattern was further amplified by flow velocity. Pore-water drainage was the major pathway for PFAA release, with the release amount predominantly determined by flow velocity-induced release intensity and depth, as well as affected by the perfluorocarbon chain length and sediment size. The weak anion exchanger-diffusion gradients in the thin-film technique confirmed that the release depth of PFAAs increased with flow velocity. Quadrant analysis revealed that the rise in the frequency and intensity of turbulent bursts driven by sweeps and ejections at high flow velocity was the underlying cause of the increased release magnitude and depth of PFAAs.

The Relationship between Take-Off Parameters and Relative Vertical Momentum of Free Limbs at the Take-Off in Hurdle Clearance.

This study aimed to clarify the kinetics of the relative vertical momentum to the proximal joint of each free limb and their contribution to the increase in the centre of mass height at the take-off of hurdle clearance, as well as their relationship with take-off variables. Thirteen male hurdlers cleared one hurdle at the height of their centre of mass, and their attempts were filmed using six high-speed cameras. The hurdle height was 96.54 ± 2.63 cm (55.35 ± 0.29% of body height). The approach distance was set at 15 m and adjusted by each hurdler in the range of 10-50 cm so as not to involve any noticeable step length adjustment before the take-off. The combined free limb relative vertical momentum tended to increase until mid-support and was maintained until the toe off. The smaller the whole-body vertical momentum at the toe off and the increase in relative vertical momentum of the lead leg during the take-off, the higher the take-off velocity, the shorter the support time, and the smaller the deceleration. The higher the relative vertical momentum of the forward swing arm during touchdown and the smaller the relative vertical momentum increase of the combined free limb and the forward swing arm during the take-off, the smaller the deceleration. In conclusion, hurdlers should reduce the increase in whole-body vertical momentum at the take-off by suppressing the increase in relative vertical momentum of the lead leg and the forward swing arm.

Hanbury-Brown–Twiss signature for clustered substructures probing primordial inhomogeneity in hot and dense QCD matter

We propose a novel approach to probe primordial inhomogeneity in hot and dense matter which could be realized in noncentral heavy-ion collisions. Although the Hanbury Brown and Twiss (HBT) interferometry is commonly used to infer the system size, the cluster size should be detected if substructures emerge in space. We demonstrate that a signal peak in the HBT two-particle correlation stands at the relative momentum corresponding to the spatial scale of pseudo one-dimensional modulation. We assess detectability using the data prepared by an event generator (AMPT model) with clustering implemented in the particle distribution. Published by the American Physical Society 2024

Effects of jet interaction angle on the ignition and combustion characteristics of hydrogen-diesel dual-fuel direct injection

This study investigates the ignition and combustion characteristics of intersecting diesel surrogate (pilot) and hydrogen (H2, main) jets under engine-relevant conditions. The experiments, performed in an optically accessible constant-volume combustion chamber (CVCC), utilised two converging single-hole injectors, with the pilot fuel accounting for 12% of the total injected fuel energy. This study investigated the effects of two key parameters on the ignition process: jet interaction angle (12° to 19°) and ambient O2 concentration (10 to 21 vol.%). The results show that the presence of H2 either advances or delays pilot ignition depending on whether the pilot n-heptane jet ignites before or after interacting with the H2 jet, respectively. The pilot-main ignition transition period is influenced by both jet interaction angle and ambient O2 concentration. Under identical ambient conditions, a smaller jet interaction angle results in a longer transition, while for a constant angle, lower ambient O2 leads to a more prolonged transition. Under 10 vol.% O2 conditions, flame kernels emerge upstream of the main flame body, before eventually merging with the reacting jet downstream, with this phenomenon observed to induce variation in heat and flame stabilisation characteristics. An explanation for the upstream kernel formation is offered based on the entrainment of residual pilot n-heptane-jet fuel into the upstream region of the still-injecting main jet, with the relative jet momentum a likely key contributor influencing this entrainment that impacts kernel formation.

Experimental Study of Cold Dense Nuclear Matter

The fundamental theory of nuclear interactions, Quantum Chromodynamics (QCD), operates in terms of quarks and gluons at higher resolution. At low resolution the relevant degrees of freedom are nucleons. Two-nucleon Short-Range Correlations (SRC) help to interconnect these two descriptions. SRCs are temporary fluctuations of strongly interacting close pairs of nucleons. The distance between the two nucleons is comparable to their radii and their relative momenta are larger than the fermi sea level. According to the electron scattering experiments held in the last decade, SRCs have far-reaching impacts on many-body systems, the nucleon-nucleon interactions, and nuclear substructure. The modern experiments with ion beams and cryogenic liquid hydrogen target make it possible to study properties of the nuclear fragments after quasi-elastic knockout of a single nucleon or an SRC pair. Here we review the status and perspectives of the SRC program in so-called inverse kinematics at JINR (Dubna, Russia). The first SRC experiment at the BM@N spectrometer (2018) with 4 GeV/c/nucleon carbon beam has shown that detection of an intact 11B nucleus after interaction selects out the quasi-elastic knockout reaction with minimal contribution of initial- and final-state interactions. Also, 25 events of SRC-breakups showed agreement in SRC properties as known from electron beam experiments. The analysis of the second measurement of SRC at BM@N held in 2022 with an improved setup is currently ongoing. The SRC project at JINR moved to a new experimental area in 2023, where the next measurement is being planned in terms of experimental setup and physics goals.

Theoretical and simulation study of dispersive electron cooling

In electron cooling, the transverse cooling rate is usually smaller than the longitudinal rate, especially at high energies. By introducing dispersive cooling, it is possible to redistribute the cooling rate between longitudinal and transverse planes. Theoretically, achieving dispersive electron cooling requires an ion dispersion and a transverse gradient of longitudinal friction force. The latter depends on many factors such as the relative momentum offset, transverse displacement, e-beam density distribution, and space charge effect. Therefore, several methods can be employed to achieve dispersive electron cooling based on these factors. Based on the dc electron beam, these factors and their respective impacts on the cooling rate are discussed and analyzed. For the first time, we propose a new mechanism to achieve dispersive cooling for a uniform electron beam by placing part of the ion beam outside of the electron beam. Based on a linear friction force model, we propose a simple formula to numerically estimate the cooling rate redistribution effect of these methods. The analytical results are in good agreement with Monte Carlo calculation and numerical simulation. Published by the American Physical Society 2024

Back-to-Back Inclusive Dijets in Deep Inelastic Scattering at Small x: Complete NLO Results and Predictions.

We compute the back-to-back dijet cross section in deep inelastic scattering at small x to next-to-leading order (NLO) in the color glass condensate effective field theory. Our result can be factorized into a convolution of the Weizsäcker-Williams gluon transverse-momentum-dependent distribution function (WW gluon TMD) with a universal soft factor and an NLO coefficient function. The soft factor includes both double and single logarithms in the ratio of the relative transverse momentum P_{⊥} of the dijet pair to the dijet momentum imbalance q_{⊥}; its renormalization group (RG) evolution is resummed into the Sudakov factor. Likewise, the WW TMD obeys a nonlinear RG equation in x that is kinematically constrained to satisfy both the lifetime and rapidity ordering of the projectile. Exact analytical expressions are obtained for the NLO coefficient function of transversely and longitudinally polarized photons. Our results allow for the first quantitative separation of the dynamics of Sudakov suppression from that of gluon saturation. They can be extended to other final states and provide a framework for precision tests of novel QCD many-body dynamics at the Electron-Ion Collider.

Calculation of momentum correlation functions between π, K , and p for several heavy-ion collision systems at sNN=39 GeV

Momentum correlation functions between π, K, and p are calculated for several heavy-ion collision systems, namely B510+B510, O816+O816, Ca2040+Ca2040, and Au79197+Au79197 in central collisions as well as Au79197+Au79197 collision in different centralities at center-of-mass energy sNN=39 GeV within the framework of a multiphase transport model complemented by the Lednický and Lyuboshitz analytical method. The results present the centrality and system-size dependence of the momentum correlation functions among pairs of π, K, and p, from which the emission source-size can be deduced. It is found that the deduced source sizes increase with the decreasing of centrality for Au + Au system or with the increasing of system size in central collisions with different nuclear size. In addition, through the momentum correlation functions of nonidentical particle pairs gated on velocity, the average emission sequence of nonidentical particles can be indicated. The results illustrate that in the small relative momentum region, protons are emitted in average earlier than π+ and K+, and K+ are emitted averagely earlier than π+. Furthermore, it seems that larger interval of the average emission order among them is exhibited for smaller collision systems. The present study sheds light on the dynamics of light particle emission at RHIC energy. Published by the American Physical Society 2024

Azimuthal anisotropies at high-pT from transverse momentum dependent (TMD) parton distribution and fragmentation functions

Unpolarized protons can generate transversely polarized quarks or linearly polarized gluons through a distribution known as the Boer-Mulders’ function. The fragmentation of similarly polarized partons to unpolarized hadrons is called the Collins’ function. Both of these functions include correlations between the spin or polarization and the relative transverse momentum of the incoming parton or outgoing hadron, with respect to the parent particle. We explore the effect of including these and other TMDs on the production of high-pT (unpolarized) hadron production from (unpolarized) proton-proton scattering. The resulting initial state anisotropies, modulated with similar final state effects, may account for the observed azimuthal anisotropy of the produced high transverse momentum hadrons, without modification to the angle integrated spectra (RAA). This may be an explanation for the existence of a v2 in high-pT hadron spectra in p-A collisions without any observable nuclear modification of the spectra.

Passive flow control at impeller radial bend for stall delay in centrifugal compressors with fishtail pipe diffusers

This paper proposes a new strategy for extending centrifugal compressor stall margin through shroud passive flow control placed at the impeller radial bend. Relative to the usual leading-edge location, the radial bend presents fewer geometrical constraints for flow control devices and allows them to have potentially more impact on low-momentum flow structures that lead to stall. Two centrifugal compressors with fishtail pipe diffusers are chosen for study: a high-speed transonic design exhibiting diffuser stall and a low-subsonic design with exducer stall. Four passive flow control techniques placed on the impeller shroud at the radial bend are evaluated for each compressor, in terms of stall margin improvement and efficiency penalty at design mass flow, using unsteady RANS CFD simulations. These are circumferential groove, slots, impeller recirculation pipe and diffuser-impeller recirculation pipe. The results indicate that passive flow control at the impeller shroud radial bend can be significantly more effective than at the impeller leading edge. For each compressor, the flow mechanisms associated with stall initiation and its delay by the most effective studied flow control technique as well as the associated efficiency penalty are elucidated. The findings indicate that techniques having flow injection with high spanwise penetration and low relative streamwise momentum are most effective for delaying diffuser stall, while the opposite applies to exducer stall. The design point efficiency penalty is due to mixing/shear losses from the jet-in-cross flow phenomenon in the impeller and shear losses from flow redistribution in the diffuser.

A TOPAS model for lens-based proton radiography

Objective. Proton Radiography can be used in conjunction with proton therapy for patient positioning, real-time estimates of stopping power, and adaptive therapy in regions with motion. The modeling capability shown here can be used to evaluate lens-based radiography as an instantaneous proton-based radiographic technique. The utilization of user-friendly Monte Carlo program TOPAS enables collaborators and other users to easily conduct medical- and therapy- based simulations of the Los Alamos Neutron Science Center (LANSCE). The resulting transport model is an open-source Monte Carlo package for simulations of proton and heavy ion therapy treatments and concurrent particle imaging. Approach. The four-quadrupole, magnetic lens system of the 800-MeV proton beamline at LANSCE is modeled in TOPAS. Several imaging and contrast objects were modelled to assess transmission at energies from 230–930 MeV and different levels of particle collimation. At different proton energies, the strength of the magnetic field was scaled according to βγ, the inverse product of particle relativistic velocity and particle momentum. Main results. Materials with high atomic number, Z, (gold, gallium, bone-equivalent) generated more contrast than materials with low-Z (water, lung-equivalent, adipose-equivalent). A 5-mrad collimator was beneficial for tissue-to-contrast agent contrast, while a 10-mrad collimator was best to distinguish between different high-Z materials. Assessment with a step-wedge phantom showed water-equivalent path length did not scale directly according to predicted values but could be mapped more accurately with calibration. Poor image quality was observed at low energies (230 MeV), but improved as proton energy increased, with sub-mm resolution at 630 MeV. Significance. Proton radiography becomes viable for shallow bone structures at 330 MeV, and for deeper structures at 630 MeV. Visibility improves with use of high-Z contrast agents. This modality may be particularly viable at carbon therapy centers with accelerators capable of delivering high energy protons and could be performed with carbon therapy.

Spatio-temporal dynamics of an acoustically forced cryogenic coaxial jet injector

This study focuses on the application of dynamical systems theory to characterize the local susceptibility of a nonreacting, cryogenic, coaxial-jet, rocket injector to transverse acoustics. This is achieved using trajectories of the phase space obtained from high-speed imaging data, which reveal the underlying dynamical states of the system. Recurrence analysis is then used to obtain regular patterns in low-dimensional sub-space plots and provide a measure of the local response through recurrence quantification analysis. Of particular interest is quantification of the spatio-temporal coupling of the jet with the external acoustics as a function of the relative momentum flux ratio between the outer and inner jets. At lower outer-to-inner jet momentum flux ratios (J < 1), the jets have a relatively strong local response to acoustic coupling in the near field. This is followed by a sharp drop in this response further downstream where a broad range of instabilities indicates turbulent breakdown of the acoustic mode. This is in contrast to higher outer-to-inner jet momentum flux ratios (J > 1), for which the jets are intermittently coupled to the acoustic mode throughout the entire axial domain due to the presence of a second harmonic or natural instability mode. These dynamical systems analysis tools are used in conjunction with wavelet filtering to improve the utility of high-speed backlit images and are qualitatively consistent with wavelet analysis of the acoustic mode within the flow. The utility of these methods for quantifying the local susceptibility of turbulent coaxial jets to acoustic perturbations can provide powerful insight for the design and optimization of passive or active control systems for bipropellant rocket injectors and other potential propulsion applications.