Momentum Correlations Research Articles

Quantized vortices in pionic superfluid

The interplay between classical vorticity being the main undisputed source of polarization in heavy-ion collisions (HIC) and quantized vortices is considered. The vortex tubes emerging in the rotating pionic (super) fluid polarize the baryons in their cores and explain the emerging global polarization. The appearance of vortices in the region separating participants and spectators in non-central HIC is similar to that for sliding layers of liquid helium. From the other side, it is also the region where the classical vorticity was earlier found to be large forming the vortex sheets. The formation of tubes manifests a threshold at certain critical vorticity implying the vanishing polarization at lower energies. For central HIC the compact jet-like flows may lead to formation of vortex rings related to local polarization. The P-odd momentum correlations for their experimental investigation are suggested. The role of shear and viscosity in the emergence of polarization is discussed.

Femtoscopy of the J/ψ-nucleon interaction

I discuss the prospects of using femtoscopy in high-energy protonproton and heavy-ion collisions to learn about the low-energy J/ψ-nucleon interaction. Femtoscopy is a technique that makes it possible to obtain spatiotemporal information on particle production sources at the femtometer scale through measurements of two-hadron momentum correlation functions. These correlation functions also provide information on low-energy hadron-hadron forces as final-state effects. In particular, such correlation functions give access to the forward scattering amplitude. One can express the forward amplitude as the product of the J/ψ chromopolarizability and the nucleon’s average chromoelectric gluon distribution, the latter being relevant to the problem of the origin of the nucleon mass. I will present the results of a recent study using the information on the J/ψ-nucleon interaction from lattice QCD simulations to compute J/ψ-nucleon correlation functions. The calculated correlation functions show clear sensitivity to the final-state interaction. I conclude discussing open issues regarding the use of the effective range expansion formula to fit experimental data for small scattering lengths and large effective range parameters.

Uncertainty Relations in the Madelung Picture.

Madelung showed how the complex Schrödinger equation can be rewritten in terms of two real equations, one for the phase and one for the amplitude of the complex wave function, where both equations are not independent of each other, but coupled. Although these equations formally look like classical hydrodynamic equations, they contain all the information about the quantum system. Concerning the quantum mechanical uncertainties of position and momentum, however, this is not so obvious at first sight. We show how these uncertainties are related to the phase and amplitude of the wave function in position and momentum space and, particularly, that the contribution from the phase essentially depends on the position–momentum correlations. This will be illustrated explicitly using generalized coherent states as examples.

First Observation of the Four-Proton Unbound Nucleus Mg18

Mg18 was observed, for the first time, by the invariant-mass reconstruction of O14+4p events. The ground-state decay energy and width are ET=4.865(34) MeV and Γ=115(100) keV, respectively. The observed momentum correlations between the five particles are consistent with two sequential steps of prompt 2p decay passing through the ground state of Ne16. The invariant-mass spectrum also provides evidence for an excited state at an excitation energy of 1.84(14) MeV, which is likely the first excited 2+ state. As this energy exceeds that for the 2+ state in Mg20, this observation provides an argument for the demise of the N=8 shell closure in nuclei far from stability. However, in open systems this classical argument for shell strength is compromised by Thomas-Ehrman shifts.Received 30 August 2021Revised 18 October 2021Accepted 16 November 2021DOI:https://doi.org/10.1103/PhysRevLett.127.262502© 2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLifetimes & widthsNuclear structure & decaysProton emissionRare & new isotopesProperties6 ≤ A ≤ 19TechniquesRadioactive beamsNuclear Physics

The relative associations of the paediatric trauma score and revised trauma score with the severity of childhood trauma.

Background:Children are prone to unintentional injuries and various scoring systems have been used to triage these injuries. The aim of this study is to determine the associations between paediatric trauma score (PTS), revised trauma score (RTS) and the length of hospital stay as an indicator of injury severity.Methods:This is a descriptive cross-sectional study conducted in the University of Calabar Teaching Hospital, Calabar and National Orthopaedic Hospital, Enugu from February 2018 to March 2020. A structured questionnaire was used to collect personal, injury-specific and treatment-specific data. The relationship between PTS, RTS and the length of hospital stay was evaluated using the one-way analysis of variance (ANOVA).Results:A total of 212 patients were included in the study. Majorities (129, 60%) of the injured children were male and most of the injuries were due to falls from height (54%). The mean PTS was 5.36 ± 1.9, while the mean RTS was 7.10 ± 0.9. The Pearson's product momentum correlation coefficient shows that there was weak but statistically significant correlation between the PTS and the RTS (r = 0.22, P = 0.02). The one-way ANOVA showed a statistically significant decrease in the RTS with increasing duration of hospital admission (F-statistic = 6.654, df = 3, P = 0.000). The PTS showed a less obvious decrease with no trend.Conclusion:In this study, the RTS showed an inverse relationship with the length of hospital stay.

Differential two-particle number and momentum correlations with the AMPT, UrQMD, and EPOS models in Pb-Pb collisions at sNN=2.76 TeV

We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differential number correlation functions, $R_{2} \left( \Delta \eta, \Delta \varphi \right)$, and transverse momentum correlation functions, $P_2 \left( \Delta \eta, \Delta \varphi \right)$ of charged particles produced in \PbPb\ collisions at the LHC centre-of-mass energy $\sqrt{s_{\rm NN}} =$ 2.76 TeV with the UrQMD, AMPT and EPOS models. Model predictions for $R_2$ and $P_2$ correlation functions are presented for inclusive charged hadrons ($h^\pm$) in selected transverse momentum ranges and with full azimuthal coverage in the pseudorapidity range $|\eta|< 1.0$. We compare these predictions for the strength, shape, and particularly the width of the correlation functions with recent measurements of these observables by the ALICE collaboration. Our analysis indicate that comparative studies of $R_2$ and $P_2$ correlation functions provide valuable insight towards the understanding of particle production in Pb--Pb collisions. We find, in particular, that these models have quantitatively different predictions for these three observables but none reproduce the measured correlation functions reported by the ALICE collaboration. Accounting for quantum number conservation in models, particularly charge conservation, is mandatory to reproduce the detailed measurements of number and transverse momentum correlation functions.

Color and baryon number fluctuation of preconfinement system in production process and Tcc structure

We suggest to study the production mechanism and some details of the production properties to probe the structure of the DDpi resonance T_cc^+ recently observed by the LHCb Collaboration. If the resonance is produced as a four-quark state, one can find the corresponding finger prints via measurements on some production properties that are the same as those of Xi_cc. The reason is that a special colour connection on the interface between the perturbative and non perturbative QCD is required for these doubly-charm hadron production. On the other hand, if T_cc^+ is produced as a hadron molecule, the measurement on the momentum correlation of DD^* can be a smoking gun to make the judgement. The present data favour a compact four-quark state production via the cc diquark fragmentation.

Unfolding the effects of final-state interactions and quantum statistics in two-particle angular correlations

Angular correlations of identified particles measured in ultrarelativistic proton-proton (pp) and heavy-ion collisions exhibit a number of features which depend on the collision system and particle type under consideration. Those features are produced by mechanisms, such as (mini)jets, elliptic flow, resonance decays, and conservation laws. In addition, of particular importance are those related to the quantum statistics (QS) and final-state interactions (FSIs). In this paper we show how to unfold the QS and FSI contributions in angular correlation functions by employing a Monte Carlo approach and using momentum correlations (femtoscopy), focusing on pp reactions. We validate the proposed method with PYTHIA 8 Monte Carlo simulations of pp collisions at $\sqrt{s}=13$ TeV coupled to calculations of QS and FSI effects with the Lednick\'y and Lyuboshitz formalism and provide predictions for the unfolded effects. In particular, we show how those effects modify the shape of the angular correlation function with emphasis on pions and protons. Most importantly, specific structures observed in the near-side region for both baryon-baryon and baryon-antibaryon pairs, originating from the strong interaction, are unveiled with the proposed method.

Microplastic pollution in seabed sediments at different sites on the shores of Istanbul-Turkey: Preliminary results

Despite recent increase in microplastics-related studies, little is known about their abundance in seabed sediment areas. However, the quantity of microplastics (MPs) in sediments is imperative for an overall understanding of worldwide MPs pollution. To address the above-mentioned gap, this study was performed on 43 seabed sediment stations from the Marmara Sea of Turkey. Studied stations vary between marine (MRN), pier (PIER), stream (STR), sea discharge (SD), and deep-sea discharge (DSD) stations. Collected seabed sediment samples were analyzed for MPs abundance, shape, size and color distribution. Besides, an investigation on the effect of sea depth on MPs' total abundance, size, and shape was investigated using Pearson's and Spearman's product momentum correlation coefficient. Empirical data analysis showed that the highest MPs abundance at STR stations changed between 1956.5 ± 3031.8 and 3256.2 ± 5168.2 particle/kg (dry weight: d.w.) for small MPs particles (SMP) and large MPs particles (LMP), respectively. Contrarily, the lowest abundance was found as 224.8 ± 423.05 and 287.68 ± 218.6 particle/kg (d.w.) for SMP and LMP fractions, respectively at DSD stations. The MPs abundance were found at 5 categorized stations in the following order; STR>PIER>MRN>SD>DSD, noted that the highest MPs quantity was found at STR-6 station located in Golden Horn. The isolated MPs were predominantly filament and fragment in shape (42.34 ± 6.10% and 33.91 ± 6.92%), blue and white in color (40.46 ± 4.66% and 24.75 ± 3.83%). Mean MPs abundance was determined to be 1957.37 ± 4079.96 particle/kg (d.w) at all 43 stations and sizes between 1 and 5 mm was found to be predominant at depths between 5 and 71m. Furthermore, a negative correlation was found between sea depth and parameters such as total MPs abundance, shape, and size. The overall results revealed the widespread presence of MPs in the seas surrounding Istanbul.

Kaon–proton strong interaction at low relative momentum via femtoscopy in Pb–Pb collisions at the LHC

In quantum scattering processes between two particles, aspects characterizing the strong and Coulomb forces can be observed in kinematic distributions of the particle pairs. The sensitivity to the interaction potential reaches a maximum at low relative momentum and vanishing distance between the two particles. Ultrarelativistic heavy-ion collisions at the LHC provide an abundant source of many hadron species and can be employed as a measurement method of scattering parameters that is complementary to scattering experiments. This study confirms that momentum correlations of particles produced in Pb–Pb collisions at the LHC provide an accurate measurement of kaon–proton scattering parameters at low relative momentum, allowing precise access to the K−p→K−p process. This work also validates the femtoscopic measurement in ultrarelativistic heavy-ion collisions as an alternative to scattering experiments and a complementary tool to the study of exotic atoms with comparable precision. In this work, the first femtoscopic measurement of momentum correlations of K−p(K+p‾) and K+p(K−p‾) pairs in Pb–Pb collisions at centre-of-mass energy per nucleon pair of sNN=5.02 TeV registered by the ALICE experiment is reported. The components of the K−p complex scattering length are extracted and found to be ℜf0=−0.91±0.03(stat)−0.03+0.17(syst) and ℑf0=0.92±0.05(stat)−0.33+0.12(syst). The results are compared with chiral effective field theory predictions as well as with existing data from dedicated scattering and exotic kaonic atom experiments.

Fragmentation of CF4q+ (q=2,3) induced by 1-keV electron collisions

We report on an investigation on the fragmentation dynamics of $\mathrm{C}{{\mathrm{F}}_{4}}^{q+}$ $(q=2,3)$ induced by 1-keV electron collisions utilizing an ion momentum imaging spectrometer. From the time-of-flight correlation maps five dominating dissociation channels of $\mathrm{C}{{\mathrm{F}}_{4}}^{2+}$ as well as one three-body fragmentation channel of $\mathrm{C}{{\mathrm{F}}_{4}}^{3+}$ are identified. The kinetic energy release (KER) distributions for these channels are obtained and compared with the data available in the literature. The Dalitz-like momentum diagram and the Newton diagram are employed to analyze the breakup mechanism in the three-body fragmentation channel. We found that, for $\mathrm{C}{{\mathrm{F}}_{4}}^{2+}$ dissociation into ${\mathrm{F}}^{+}+\mathrm{C}{{\mathrm{F}}_{2}}^{+}+\mathrm{F}$, ${\mathrm{F}}^{+}+\mathrm{C}{\mathrm{F}}^{+}+2\mathrm{F}$, and ${\mathrm{F}}^{+}+{\mathrm{F}}^{+}+{\mathrm{CF}}_{2}$, the concerted breakup is the dominating process. Channel ${\mathrm{C}}^{+}+{\mathrm{F}}^{+}+3\mathrm{F}$ is dominated by the initial charge separation, i.e., $\mathrm{C}{{\mathrm{F}}_{4}}^{2+}\ensuremath{\rightarrow}{\mathrm{F}}^{+}+\mathrm{C}{\mathrm{F}}^{+}+2\mathrm{F}\ensuremath{\rightarrow}{\mathrm{C}}^{+}+{\mathrm{F}}^{+}+3\mathrm{F}$. With the help of the native frame method, we assigned one sequential pathway and two concerted pathways for channel $\mathrm{C}{{\mathrm{F}}_{4}}^{3+}\ensuremath{\rightarrow}{\mathrm{F}}^{+}+{\mathrm{F}}^{+}+\mathrm{C}{{\mathrm{F}}_{2}}^{+}$. The branching ratios of these pathways are determined. The momentum correlation of the fragments and the deduced KER distribution indicate that different excited states of $\mathrm{C}{{\mathrm{F}}_{4}}^{3+}$ with different geometries are responsible for these three pathways. The Coulomb explosion model simulation shows that most of the events in this channel are produced by $\mathrm{C}{{\mathrm{F}}_{4}}^{3+}$ ions that have deformed geometries from the neutral ${\mathrm{CF}}_{4}$ molecule.

Ultrafast ring-opening fragmentation dynamics of C6H63+ induced by electron-impact ionization

The fragmentation dynamics of triply charged benzene [(${\mathrm{C}}_{6}{\mathrm{H}}_{6}{)}^{3+}$] induced by 260 eV electron-impact ionization are investigated using a multiparticle coincidence momentum spectrometer. By measuring three fragment ions and one outgoing electron in quadruple coincidence, we identify the complete three-body dissociation channels of ${{\mathrm{CH}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{3}}^{+} + {\mathrm{C}}_{3}{\mathrm{H}}^{+}, {{\mathrm{CH}}_{3}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{3}{\mathrm{H}}^{+}$, and ${\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+}$. We determine the projectile-energy-loss spectra, Dalitz plots, Newton diagrams, momentum correlation maps, and kinetic-energy release for each fragmentation channel. The analysis of these spectra is supported by an ab initio molecular dynamics simulation, which provides a molecular movie of the dissociation process. Our study reveals sequential mechanisms for all three dissociation channels of (${\mathrm{C}}_{6}{\mathrm{H}}_{6}{)}^{3+}$ trication, i.e., an ultrafast ring-opening reaction followed by two subsequent Coulomb-explosion processes.

Three-body fragmentation mechanism of C2H43+ produced by 18−keV/uNe8+ impact

In this article we present the three-body fragmentation dynamics of ${\mathrm{C}}_{2}{{\mathrm{H}}_{4}}^{3+}$ caused by $18\text{\ensuremath{-}}\mathrm{keV}/\mathrm{u}\phantom{\rule{0.16em}{0ex}}{\mathrm{Ne}}^{8+}$ ion impact. Utilizing the cold target recoil ion momentum spectroscopy, the complete kinematical information of three fragmentation channels, i.e., ${\mathrm{C}}_{2}{{\mathrm{H}}_{4}}^{3+}\ensuremath{\rightarrow}{\mathrm{H}}^{+}+{\mathrm{H}}^{+}+{\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+}, {\mathrm{H}}^{+}+\mathrm{C}{\mathrm{H}}^{+}+\mathrm{C}{{\mathrm{H}}_{2}}^{+}$, and ${\mathrm{H}}^{+}+{{\mathrm{H}}_{2}}^{+}+{\mathrm{C}}_{2}{\mathrm{H}}^{+}$ is obtained. For each channel, both concerted and sequential fragmentation mechanisms are observed and differentiated through the momentum correlation of resultant fragments visualized by the Dalitz plot and the Newton diagram. In particular, for the channel ${\mathrm{C}}_{2}{{\mathrm{H}}_{4}}^{3+}\ensuremath{\rightarrow}{\mathrm{H}}^{+}+{\mathrm{H}}^{+}+{\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+}$, it is found in addition to the sequential pathway that the two protons can be emitted concertedly in two ways, i.e., from the same carbon atom or from the two carbon atoms. The present results show a more diverse molecular fragmentation triggered by ion collisions in contrast to a previous study using intense laser field ionization.

Azimuthal dependence of two-particle transverse momentum current correlations

Two-particle transverse momentum correlation functions are a powerful technique for understanding the dynamics of relativistic heavy-ion collisions. Among these, the transverse momentum correlator G_{2}left( varDelta eta ,varDelta varphi right) is of particular interest for its potential sensitivity to the shear viscosity per unit of entropy density eta /s of the quark-gluon plasma formed in heavy-ion collisions. We use the UrQMD, AMPT, and EPOS models for Au–Au at sqrt{s_mathrm{NN}} = 200 GeV and Pb–Pb at sqrt{s_mathrm{NN}} = 2760 GeV to investigate the long range azimuthal dependence of G_{2}left( varDelta eta ,varDelta varphi right) , and explore its utility to constrain eta /s based on charged particle correlations. We find that the three models yield quantitatively distinct transverse momentum Fourier harmonics coefficients a^{p_mathrm{T}}_{n}. We also observe these coefficients exhibit a significant dependence on eta /s in the context of the AMPT model. These observations suggest that exhaustive measurements of the dependence of G_{2}left( varDelta varphi right) with collision energy, system size, collision centrality, in particular, offer the potential to distinguish between different theoretical models and their underlying assumptions. Exhaustive analyses of G_{2}left( varDelta varphi right) obtained in large and small systems should also be instrumental in establishing new constraints for precise extraction of eta /s.

Exact closed-form analytic wave functions in two dimensions: Contact-interacting fermionic spinful ultracold atoms in a rapidly rotating trap

Exact two-dimensional analytic wave functions for an arbitrary number $N$ of contact-interacting lowest-Landau-level (LLL) spinful fermions are derived with the use of combined numerical and symbolic computational approaches via analysis of exact Hamiltonian numerical diagonalization data. Closed-form analytic expressions are presented for two families of zero-interaction-energy states at given total angular momentum and total spin $0 \leq S \leq N/2$ in the neighborhood of the $\nu=1$ filling, covering the range from the maximum density droplet to the first quasihole. Our theoretical predictions for higher-order spatial and momentum correlations reveal intrinsic polygonal, multi-ring crystalline-type structures, which can be tested with ultracold-atom experiments in rapidly rotating traps, simulating quantum Hall physics (including quantum LLL skyrmions).

Imaging of OAM-entangled photon pairs in the Bessel-Gauss basis with full index control

In this paper, we directly image the orbital angular momentum (OAM) correlations, expressed in the Bessel-Gauss (BG) basis, present in quantum-entangled photon pairs produced by the process of spontaneous parametric downconversion (SPDC). We use a spatial light modulator that displays an appropriate phase mask, followed by coupling into a single-mode fiber, so as to project the signal, or heralding, photon onto a BG mode, and verify that the idler, or heralded, photon is projected non-locally as expected. In contrast with similar experiments relying on Laguerre-Gauss (LG) modes, our current experiment permits, firstly, full index control (allowing the experimenter to define both the azimuthal index ℓ s and the continuous radial index k rs , also referred to as scaling parameter). Importantly, while not resolving the radial index leaves the heralded single photon in a statistical mixture of all available radial modes, the ability to determine both indices allows us to herald single photons in a particular BG mode, described by a quantum-mechanically pure state. Our use of BG modes permits, secondly, the spatially-resolved detection of the heralded single photon, both in the near and far fields, with a time-gated intensified CCD camera, making it possible to experimentally determine both the radial and azimuthal indices of the heralded single photon. Thirdly, the fact that for BG modes the radial index (scaling parameter) is continuous makes it possible to use the scaling parameter as a continuous adjustment in quantum state engineering, for precise mode matching, or for the selection of photon-pair properties such as the spiral bandwidth, as we experimentally demonstrate. We believe that our work opens up interesting new possibilities in the field of quantum communications based on the spatial degree of freedom of photon pairs.

Emission of Spin-Correlated Matter-Wave Jets from Spinor Bose-Einstein Condensates.

We report the observation of matter-wave jet emission in a strongly ferromagnetic spinor Bose-Einstein condensate of ^{7}Li atoms. Directional atomic beams with |F=1,m_{F}=1⟩ and |F=1,m_{F}=-1⟩ spin states are generated from |F=1,m_{F}=0⟩ state condensates or vice versa. This results from collective spin-mixing scattering events, where spontaneously produced pairs of atoms with opposite momentum facilitates additional spin-mixing collisions as they pass through the condensates. The matter-wave jets of different spin states (|F=1,m_{F}=±1⟩) can be a macroscopic Einstein-Podolsky-Rosen state with spacelike separation. Its spin-momentum correlations are studied by using the angular correlation function for each spin state. Rotating the spin axis, the inter- and intraspin-momentum correlation peaks display a high-contrast oscillation, indicating collective coherence of the atomic ensembles. We provide numerical calculations that describe the experimental results at a quantitative level. Our Letter paves the way to generating macroscopic quantum entanglement with the spin and motional degree of freedom with massive particles. It has a wide range of applications from quantum information science to the fundamental studies of quantum entanglement.

Position correlation enabled quantum imaging with undetected photons

Quantum imaging with undetected photons (QIUP) is a unique imaging technique that does not require the detection of the light used for illuminating the object. This technique requires a correlated pair of photons. In the existing implementations of QIUP, the imaging is enabled by the momentum correlation between the twin photons. We investigate the complementary scenario in which the imaging is instead enabled by the position correlation between the two photons. We present a general theory and show that the properties of the images obtained in these two cases are significantly distinct.

Associated production of a vector boson and jets

The production cross section of vector bosons recoiling against jets is studied, with CMS data, differentially as a function of the transverse momentum and angular correlations of the final state particles. The measurements are confronted with different state-of-the-art theory predictions that include next-to-leading-order calculations and matrix-element plus parton shower event simulations.

Bose-Einstein momentum correlations at fixed multiplicities: Lessons from an exactly solvable thermal model for pp collisions at the LHC

Two-particle momentum correlations of $N$ identical bosons are studied in the quantum canonical ensemble. We define the latter as a properly selected subensemble of events associated with the grand canonical ensemble which is characterized by a constant temperature and a harmonic-trap chemical potential. The merits of this toy model are that it can be solved exactly, and that it demonstrates some interesting features revealed recently in small systems created in $p+p$ collisions at the LHC. We find that partial coherence can be observed in particle emission from completely thermal ensembles of events if instead of inclusive measurements one studies the two-boson distribution functions related to the events with particle numbers selected in some fixed multiplicity bins. The corresponding coherence effects increase with the multiplicity.