Spin Correlation Coefficients Research Articles

Impact of the N4LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^4\\hbox {LO}$$\\end{document} Short-Range Three-Nucleon Force Components on the Nucleon-Deuteron Spin Correlation Coefficients

The spin correlation coefficients in the neutron-deuteron elastic scattering process at incoming neutron laboratory energies E=10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {E}=10$$\\end{document}, 135, 190, and 250 MeV are determined by solving the momentum space three-nucleon (3N) Faddeev equations. The chiral two-nucleon (2N) interaction with momentum-space semi-local (SMS) regularization up to the fifth order of chiral expansion (N4LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^4\\hbox {LO}$$\\end{document}), supplemented by the F-waves terms from the sixth order (N5LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^5\\hbox {LO}$$\\end{document}), is used. Additionally, the consistent 3N force (3NF) at the third order of chiral expansion, supplemented by the short-range contributions from N4LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^4\\hbox {LO}$$\\end{document} is applied. As a results, we give predictions for the complete set of spin correlation coefficients Cα,β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C_{\\alpha ,\\beta }$$\\end{document}. We find that the effect of the investigated three-nucleon N4LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^4\\hbox {LO}$$\\end{document} components amounts up to several dozen percent, depending on reaction energy, scattering angle and type of spin correlation coefficient itself. Our results can serve as a guide for future measurements of the spin correlation coefficients.

Laboratory-frame tests of quantum entanglement in H→WW

Quantum entanglement between the two $W$ bosons resulting from the decay of a Higgs boson may be investigated in the dilepton channel $H\ensuremath{\rightarrow}WW\ensuremath{\rightarrow}\ensuremath{\ell}\ensuremath{\nu}\ensuremath{\ell}\ensuremath{\nu}$ using laboratory-frame observables that only involve the charged leptons $\ensuremath{\ell}=e$, $\ensuremath{\mu}$. The dilepton invariant mass distribution, already measured by the ATLAS and CMS Collaborations at the LHC, can be used to observe the quantum entanglement of the $WW$ pair with a statistical sensitivity of $7\ensuremath{\sigma}$ with run 2 data, and of $6\ensuremath{\sigma}$ when including theoretical systematics. As a by-product, the relation between $W$ rest frame (four-dimensional) angular distributions, $H\ensuremath{\rightarrow}WW$ decay amplitudes, and spin correlation coefficients, is written down.

Time-reversal-invariance violation in the Nd system and large NC

A minimal set of five low energy constants (LECs) for time-reversal and parity violating $(\overline{)T}\overline{)P})$ nucleon-nucleon $(NN)$ interactions at low energies $(E<{m}_{\ensuremath{\pi}}^{2}/{M}_{N})$ is given. Using a large-${N}_{C}$ (number of colors in quantum chromodynamics) analysis we show that one linear combination of LECs is $\mathcal{O}({N}_{C})$, three LECs are $\mathcal{O}({N}_{C}^{0})$, and one linear combination of LECs is $\mathcal{O}({N}_{C}^{\ensuremath{-}1})$. We also calculate the $\overline{)T}\overline{)P}$ observables of neutron spin rotation through a polarized deuteron target and a spin correlation coefficient in nucleon-deuteron scattering using pionless effective field theory. Using the large-${N}_{C}$ analysis we show that the spin correlation coefficient and the neutron spin rotation are predominantly determined by the same two LECs in the large-${N}_{C}$ basis.

Spin correlation coefficient for proton- He3 elastic scattering at 100 MeV

We present the measured spin correlation coefficient Cy,y for p−He3 elastic scattering at 100 MeV at the angles θc.m.=46.9∘–149.2∘ in the center-of-mass system. The Cy,y data and the existing cross section data are compared with rigorous four-nucleon scattering calculations based on realistic nucleon-nucleon potentials. Large differences are seen in the regime around the cross section minimum for both observables. The Δ-isobar effects estimated by the NN+NΔ coupled-channels approach are small for the cross section. Meanwhile, in Cy,y, the Δ-isobar effects improve the agreement with the data. The analysis of the p−He3 elastic scattering amplitudes implies the necessity of three-nucleon forces (3NFs) that enhance the vector components in the amplitudes. The obtained results indicate that the spin correlation coefficient Cy,y expands the knowledge of the nuclear interactions with the Δ isobar or those including 3NFs that are masked in nucleon-deuteron elastic scattering.1 MoreReceived 29 July 2022Accepted 17 October 2022DOI:https://doi.org/10.1103/PhysRevC.106.054002©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasFew-body systemsH & He induced nuclear reactionsNuclear forcesNucleon-nucleon interactionsNuclear Physics

Improved tests of entanglement and Bell inequalities with LHC tops

We discuss quantum entanglement in top pair production at the LHC. Near the t {bar{t}} threshold, entanglement observables are enhanced by suppressing the contribution of q {bar{q}} subprocesses, which is achieved by a simple cut on the velocity of the t {bar{t}} system in the laboratory frame. Furthermore, we design new observables that directly measure the relevant combinations of t{bar{t}} spin correlation coefficients involved in the measurement of entanglement and Bell inequalities. As a result, the statistical sensitivity is enhanced, up to a factor of 7 for Bell inequalities near threshold.

Phase separation of spin-1 spin-orbital-angular-momentum coupled Bose–Einstein condensates

In this study, we study the circularly-symmetric phase separation in spin-1 spin-orbit-angular-momentum coupled (SOAMC) [Formula: see text] Bose–Einstein condensate (BEC) system in the [Formula: see text]-plane using a numerical solution of the mean-field Gross–Pitaevskii equation. The increase of the coupling strength [Formula: see text] in such a system is found to generate annular structures. The phase-separated had different structures with the spin and linear momentum coupling BEC. Our results are in good agreement with the new experiment H. R. Chen, K. Y. Lin, P. K. Chen, N. C. Chiu, J. B. Wang and C.-A. Chen, Phys. Rev. Lett. 121 (2018) 113204. We also analyzed the influence of different parameters of SOAMC on coupling strength [Formula: see text], spin correlation coefficient [Formula: see text], the number of particles [Formula: see text], and the anisotropy of the potential in the three-component equations. The dynamical stability of the phase separation is demonstrated by real-time propagation numerically.

Influence of nucleon structure on spin correlation coefficients in elastic lepton-deuteron scattering

Spin correlation coefficients in elastic scattering of leptons on the deuteron are studied in the one-photon-exchange Born approximation within the limit of zero lepton mass. Numerical estimations for the spin correlation coefficients caused by a polarized beam and a vector polarized target are presented and analyzed at various beam energies and scattering angles in two coordinate systems which are relevant for experiment. The influence of the obtained results on the nucleon structure is investigated, and a considerable dependence at incident beam energies greater than 1[Formula: see text]fm[Formula: see text] and backward scattering angles is found. The estimated results are of particular interest for encouragement of experimental measurements of lepton-deuteron scattering which aim for accurate calculation of the charge radius of the proton to a high degree of precision. These results may also stimulate new generation of measurements of different physical observables very sensitive to the spin structure of the nucleon and light nuclei.

Spin correlation coefficients in lepton–deuteron elastic scattering and their sensitivity to realistic NN potentials

Spin correlation coefficients in the elastic scattering of leptons on the deuteron, [Formula: see text], are studied in the one-photon-exchange approximation within the limit of zero lepton mass. Numerical estimations for the spin correlation coefficients caused by a polarized beam and a vector polarized target are given. The estimated spin correlation coefficients are analyzed at various values of beam energy and scattering angle. The sensitivity of the obtained results to the choice of realistic NN potential used for the deuteron wave function is investigated. We found a considerable dependence of the results on the realistic deuteron wave functions at incident beam energies greater than 0.4 GeV and backward scattering angles. The estimated results are of particular interest for encouragement of experimental measurements of lepton–deuteron scattering which aim for accurate calculation of the charge radius of the proton to a high degree of precision. These results may also stimulate new generation of measurements of different physical observables very sensitive to the spin structure of the nucleon and light nuclei.

Probing the spin correlations of t{bar{t}} production at NLO QCD+EW

In this work we investigate the NLO QCD+EW corrections to the top quark pair production and their effects on the spin correlation coefficients and asymmetries at fixed-order top quark pair production and LO decay in the dilepton channel, within the narrow-width approximation. The spin correlations are implicitly measured through the lepton kinematics. Moreover we study the EW effects to the leptonic differential distributions. We find that the EW corrections to the t {bar{t}} production are within the NLO QCD theoretical uncertainties for the spin correlation coefficients and the leptonic asymmetries. On the other hand, for the differential distributions we find that the EW corrections exceed the NLO QCD scale uncertainty band in the high rapidity regimes and are of the order of the NLO QCD scale uncertainty in the case of invariant mass and transverse momentum distributions.

MANIFESTATION OF AN EXCITED ELECTRON IN e⁺e¯ → γγ REACTION

The differential cross section and some polarization observables have been calculated for the e⁺e¯ → γγ reaction taking into account the contribution of the excited electron. The spin correlation coefficients were calculated for the case when both beams are polarized. We consider two approaches for the excited electron contribution: the eу → γγ contact interaction and the exchange of the excited electron in t- and u-channels. Numerical estimations are given for the excited electron contribution to the differential cross section and spin correlation coefficients for vari-ous values of the electron beam energy and excited electron mass.

Proton- He3 elastic scattering at intermediate energies

We present a precise measurement of the cross section, proton and $\rm ^3He$ analyzing powers, and spin correlation coefficient $C_{y,y}$ for $p$-$\rm ^3He$ elastic scattering near 65 MeV, and a comparison with rigorous four-nucleon scattering calculations based on realistic nuclear potentials and a model with $\Delta$-isobar excitation. Clear discrepancies are seen in some of the measured observables in the regime around the cross section minimum. Theoretical predictions using scaling relations between the calculated cross section and the $\rm ^3 He$ binding energy are not successful in reproducing the data. Large sensitivity to the $NN$ potentials and rather small $\Delta$-isobar effects in the calculated cross section are noticed as different features from those in the deuteron-proton elastic scattering. The results obtained above indicate that $p$-$\rm ^3He$ scattering at intermediate energies is an excellent tool to explore nuclear interactions not accessible by three-nucleon scattering.

Polarization Effects in the Reaction d+eˉ → d+eˉ

The differential cross section and polarization observables for the elastic reaction induced by deuteron scattering off electrons at rest, are calculated in the one-photon-exchange approximation. The following polarization observables were calculated: 1- the analyzing powers (asymmetries) due to the tensor polarization of the deuteron beam, 2 - the spin correlation coefficients caused by the arbitrarily polarized electron target and the vector polarized deuteron beam, 3 - the coefficients of the polarization transfer from the arbitrarily polarized target electron to the recoil electrons. The differential cross section and polarization observables have been expressed in terms of the deuteron electromagnetic form factors: (charge monopole), (magnetic dipole) and (charge quadrupole). Numerical estimations are given for the analyzing powers (asymmetries) due to the tensor polarization of the deuteron beam. They are calculated as functions of the deuteron beam energy for some values of the scattering angle (the angle between the deuteron beam and the recoil electron momenta). For the numerical calculation we use the existing phenomenological parametrization of the deuteron electromagnetic form factors. It turns out that the analyzing powers (asymmetries) are increasing with the growth of the deuteron beam energy and they have appreciable sensitivity to the value of the scattering angle. The specific interest of this reaction is to investigate the possibility to use this reaction for the measurement of the polarization of the high energy deuteron beams.

Measurement of spin correlation coefficients p-$^{3}$He scattering at 65 MeV

We performed the experiment of p–^{3}3He scattering at 65 MeV by using polarized proton beams and the newly constructed polarized ^{3}3He target. The proton analyzing power A_{y}Ay, the ^{3}3He analyzing power A_{y}^{T}AyT, and the spin correlation coefficient C_{yy}Cyy were measured. In the conference, the experimental data were compared with the rigorous numerical calculations based on various nuclear potentials. Large discrepancies between the experimental data and the calculations were found in the A_{y}^{T}AyT and the {C_{yy}}Cyy at the backward angles.

Deuteron wave function for Reid93 potential and polarization observables in elastic lepton–deuteron scattering

The elastic lepton–deuteron scattering was considered within the limits of zero lepton mass. The deuteron wave function in the coordinate representation for Reid93 potential was applied to numerical calculations. The angular-momentum dependence of values of the spin correlation coefficients [Formula: see text], [Formula: see text] and tensor asymmetries [Formula: see text], [Formula: see text], [Formula: see text] were evaluated in 3D format for Reid93 potential. These polarization observables are analyzed at different energies and scattering angles. The influence of the choice of the potential model and their nodes on the calculations of the polarization observables at a fixed scattering angle was taken into account. The application of the obtained values allows better explanation and illustration of the laws for the elastic lepton–deuteron scattering.

Various types of theoretical uncertainties by example of the elastic nucleon-deuteron scattering spin correlation coefficient Cz,x

The elastic nucleon-deuteron scattering process can be used to study three-nucleon dynamics, but in order to draw reliable conclusions based on the comparison of theoretical predictions and data, an estimation of theoretical uncertainties is necessary. We consider the statistical errors arising from a propagation of uncertainties of the two-nucleon interaction parameters to the three-nucleon system, truncation errors, regulator dependencies, and uncertainties arising from using the formalism of partial waves. We give an example of the nucleon-deuteron spin correlation coefficient Cz,x, obtained within the Faddeev approach, to discuss magnitudes of the above mentioned theoretical uncertainties. We find that using various models of the nuclear forces results in the dominant theoretical uncertainty for the nucleon-deuteron elastic scattering observables.

EFFECTS OF SCALAR BOSON IN ELASTIC PROTON-ELECTRON SCATTERING

The differential cross section for the elastic scattering of unpolarized protons on unpolarized electrons at rest is calculated taking into account two mechanisms: one-photon and scalar-boson exchange. The spin correlation coefficients, when the proton beam and the electron target are both arbitrarily polarized, have also been calculated. These observables are calculated in terms of the proton electromagnetic form factors, namely magnetic and electric ones. Some peculiarities of the inverse kinematics (the mass of the colliding particle is larger than mass of the target particle) have been discussed. It was shown that all the spin correlation coefficients in the elastic proton electron collisions are proportional to the proton magnetic form factor. The same behaviour takes place for the spin correlation coefficients in the elastic electron proton scattering (the electron beam and proton target are both polarized). It was shown that only the interference of the two mechanisms (one-photon and one-boson) gives nonzero contribution to the spin correlation coefficients. If the spin vectors of the proton beam and electron target lie in the reaction plane then the corresponding spin correlation coefficients are zero for the case when scattered electron momentum is in the direction of the proton beam momentum.

Top quark properties and mass measurements with the ATLAS detector

Highlights on recent measurements of top quark properties in ATLAS, using pp collision data at s = 8 TeV and 13 TeV, are presented. The measurements of the top quark polarization and spin correlation coefficients, the W boson helicity fractions, the structure of the Wtb vertex, the associated production of a tt‾ pair with a vector boson or a photon, and the top quark mass are all in agreement with the Standard Model expectations.

Polarization Observables in Few-Nucleon Scattering

Systems composed of a few nucleons are subject of experimental studies for many years with the aim to gain precise information on the interaction between nucleons. Intermediate energies, below the threshold for pion production, deserve special attention: it is a region where comparison with exact theoretical calculations is possible, while the sensitivity to various aspects of interaction, like subtle effects of the dynamics beyond the pairwise nucleon-nucleon force, is significant. In addition to differential cross section, the observables related to nuclear polarization are studied, like vector and tensor analyzing powers, spin-correlation coefficients or polarization transfer coefficients. A brief survey of results of recent studies in few-nucleon systems is given.

Phenomenology of spin observables in the reactions of meson production with the 1 S 0 Diproton pN → {pp} s X

Formalism for spin observables for production of pseudoscalar, scalar, and vectormesons in pN collision with formation of the 1S0 diproton {pp}s in the final state is considered in model-independent way assuming parity and angular momentum conservation. Production of the pseudoscalar mesons (Jπ = 0−) is described by two spin amplitudes and both of them can be completely determined by measurement of unpolarized cross section dσ0, vector analyzing power Ay, and spin-correlation coefficients Cx,x = −Cz,z> and Cx,z. Similar result is obtained for production of scalar mesons (Jπ = 0+). It is shown that measurement of the tensor polarization t20 of the vector meson V (Jπ = 1−) in the reaction pN → {pp}sV in collinear kinematics gives the same information as measurement of the spin-correlation coefficients Cz,z or Cy,y.

Measurement of the spin-correlation coefficients A x,x and A y,y in the quasi-free np → {pp} s π− reaction near threshold at ANKE-COSY

A kinematically complete double-polarization measurement of the quasi-free np → {pp} s π− reaction near threshold has been performed using the ANKE spectrometer at COSY-Julich. Here {pp} s represents a two-proton system with an excitation energy less than 3 MeV. The transversely vector polarized deuteron beam and the internal polarized ANKE hydrogen target were used to determine the spin-correlation coefficients A x,x and A y,y . Events from the quasi-free np → dπ0 reaction were recorded simultaneously and used for both beam and target polarimetry. In addition, the product of the beam and target polarizations could be estimated from the A y,y coefficient. The storage cell within the polarized target was the main source of background events. Dedicated runs, with no gas in the cell and with the cell filled with N 2 gas, were taken to study the backgrounds. The data analysis procedure and the initial results of the experiment are presented.