Low Momentum Transfer Research Articles

Reactor neutrino liquid xenon coherent elastic scattering experiment

Coherent elastic neutrino-nucleus scattering (CEνNS) provides a unique probe for neutrino properties beyond the Standard Model physics. The reactor neutrino liquid xenon coherent scattering experiment (RELICS), a proposed reactor neutrino program using liquid xenon time projection chamber technology, aims to investigate the CEνNS process of antineutrinos off xenon atomic nuclei. In this work, the design of the experiment is studied and optimized based on Monte Carlo simulations. To achieve a sufficiently low-energy threshold for CEνNS detection, an ionization-only analysis channel is adopted for RELICS. A high emission rate of delayed electrons after a big ionization signal is the major background, leading to an analysis threshold of 120 photoelectrons in the CEνNS search. The second largest background, nuclear recoils induced by cosmic-ray neutrons, is suppressed via a passive water shield. The physics potential of RELICS is explored with a 30 kg·yr exposure at a baseline of 25 m from a reactor core with a 3 GW thermal power. In an energy range of 120–300 photoelectrons, corresponding to an average nuclear recoil from 0.63 to 1.36 keV considering the liquid xenon response and detector-related effect, we expect 4639.7 CEνNS and 1687.8 background events. The sensitivity of RELICS to the weak mixing angle is investigated at a low momentum transfer. Our study shows that RELICS can further improve the constraints on the nonstandard neutrino interaction compared to the current best results. Published by the American Physical Society 2024

Glue in hadrons at medium resolution and the QCD instanton vacuum

We discuss a general framework for the evaluation of the gluonic form factors in light hadrons at low momentum transfer, in the QCD instanton vacuum. At medium resolution of the order of the inverse mean instanton size, the glue is mostly localized in single or pairs of pseudoparticles and globally constrained by the fluctuations of their topological charges. These pseudoparticles trap light quarks, giving rise to emerging multiflavor ’t Hooft interactions. We explicitly evaluate the gluonic scalar, pseudoscalar, energy-momentum tensor (EMT), and the leading C-odd and C-even three-gluon hadronic form factors, at next to leading order in the instanton density, including molecular clusters of like and unlike instantons. We use the results for the EMT to address the contribution of the gluons in Ji’s mass and spin sum rules, at low resolution. When evolved, our results for the mass and spin composition of the nucleon are shown to be in good agreement with the recently reported lattice results at higher resolution. Published by the American Physical Society 2024

Neutron radius determination of 133Cs and its impact on the interpretation of CEνNS-CsI measurement

Proton-133Cs elastic scattering at low momentum transfer is performed using an in-ring reaction technique at the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou. Recoil protons from the elastic collisions between the internal H2-gas target and the circulating 133Cs ions at 199.4 MeV/u are detected by a silicon-strip detector. The matter radius of 133Cs is deduced by describing the measured differential cross sections using the Glauber model. Employing the adopted proton distribution radius, a point-neutron radius of 4.86(21) fm for 133Cs is obtained. With the newly determined neutron radius, the weak mixing angle sinθW2 is independently extracted to be 0.227(28) by fitting the coherent elastic neutrino-nucleus scattering data. Our work limits the sinθW2 value in a range smaller than the ones proposed by the previous independent approaches, and would play an important role in searching new physics via the high precision CEνNS-CsI cross section data in the future.

Odderon contribution in light of the LHC low- t data

We perform the analysis of elastic scattering pp and p¯p data at low momentum transfer |t|<0.1 GeV2 within large collider energy interval s=50 GeV–13 TeV in order to evaluate quantitatively the possible Odderon contribution. We use the two-channel eikonal model, which naturally accounts for the screening of the Odderon amplitude by C-even (Pomeron) exchanges. Published by the American Physical Society 2024

Ultrahigh resolution x-ray Thomson scattering measurements at the European X-ray Free Electron Laser

Using an ultrahigh resolution (ΔE∼0.1eV) setup to measure electronic features in x-ray Thomson scattering (XRTS) experiments at the European XFEL in Germany, we have studied the collective plasmon excitation in aluminium at ambient conditions, which we can measure very accurately even at low momentum transfers. As a result, we can resolve previously reported discrepancies between time-dependent density functional theory simulations and experimental observations. The demonstrated capability for high-resolution XRTS measurements will be a game changer for the diagnosis of experiments with matter under extreme densities, temperatures, and pressures, and unlock the full potential of state-of-the-art x-ray free electron laser (XFEL) facilities to study planetary interior conditions, to understand inertial confinement fusion applications, and for material science and discovery. Published by the American Physical Society 2024

Resonance contributions to nucleon spin structure in holographic QCD

We study polarized inelastic electron-nucleon scattering at low momentum transfer in the Witten-Sakai-Sugimoto model of holographic QCD, focusing on resonance production contributions to the nucleon spin structure functions. Our analysis includes both spin 3/2 and spin 1/2 low-lying nucleon resonances with positive and negative parity. We determine, in turn, the helicity amplitudes for nucleon-resonance transitions and the resonance contributions to the neutron and proton generalized spin polarizabilities. Extrapolating the model parameters to realistic QCD data, our analysis, triggered by recent experimental results from Jefferson Lab, agrees with the observation that the ∆(1232) resonance gives the dominant contribution to the forward spin polarizabilities at low momentum transfer. The contribution is negative and tends to zero as the momentum transfer increases. As expected, the contribution of the ∆(1232) to the longitudinal-transverse polarizabilities is instead negligible. The latter, for both nucleons, turn out to be negative functions with zero asymptote. The holographic results, at least for the proton where enough data are available, are in qualitative agreement with the resonance contributions to the spin polarizabilities extracted from experimental data on the helicity amplitudes.

New determination of |Vub/Vcb| from Bs0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}_s^0 $$\\end{document}→ {K−, Ds−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}_s^{-} $$\\end{document}}μ+ν

We update the full set of B¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\overline{B} $$\\end{document}s → K form factors using light-cone sum rules with an on-shell kaon. Our approach determines the relevant sum rule parameters — the duality thresholds — from a Bayesian fit for the first time. Using a modified version of the Boyd-Grinstein-Lebed parametrisation, we combine our sum rule results at low momentum transfer q2 with more precise lattice QCD results at large q2. We obtain a consistent description of the form factors in the full q2 range. Applying these results to a recent LHCb measurement of branching ratios for the decays Bs0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}_s^0 $$\\end{document} → {K−, Ds−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}_s^{-} $$\\end{document}}μ+νμ, we determine the ratio of Cabibbo-Kobayashi-Maskawa elementsVubVcbq2<7GeV2=0.0681±0.0040andVubVcbq2>7GeV2=0.0801±0.0047,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\left|\\frac{V_{ub}}{V_{cb}}\\right|}_{q^2<7\\;{\ extrm{GeV}}^2}=0.0681\\pm 0.0040\\kern0.5em \ extrm{and}\\kern0.5em {\\left|\\frac{V_{ub}}{V_{cb}}\\right|}_{q^2>7\\;{\ extrm{GeV}}^2}=0.0801\\pm 0.0047, $$\\end{document}which are mutually compatible at the 1.9σ level. We further comment on the sensitivity to Beyond the Standard Model effects through measurements of the shape of Bs0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}_s^0 $$\\end{document} → K−μ+νμ decays, in light of recent limits on such effects from other exclusive b → uℓν processes.

Calculation of X-ray attenuation coefficients for normal and cancerous breast tissues

The study was carried out by numerical integration based on the diffraction properties and elemental composition. The elemental compositions of breast tissues in the literature were tested. The photon attenuation coefficients calculated using the recent elemental composition were found within 0.2˗16% for adipose tissue and within 0.04˗17% for glandular tissue with the experimental reference data. The attenuation coefficients of cancerous breast tissue calculated according to the elemental content previously measured in breast cancer patients were found within 0˗17% with experimental data in the literature. The attenuation coefficients are of great interest to medical research. To calculate realistic attenuation coefficients, the characteristic coherent scatter, which is most intense at small angles, must be considered. For this reason, experimentally measured form factor data were reviewed, and the most compatible one with the theoretical form factor data produced in this study was used at low momentum transfer x (0 < x ≤ 8 nm−1). The differential linear coherent scattering distributions were calculated for an energy value of 17.44 keV and compared with their experimental counterparts.

Multiscale Imaging of Nuclear Deformation at the Electron-Ion Collider.

We show within the color glass condensate framework that exclusive vector meson production at high energy is very sensitive to the geometric deformation of the target nucleus at multiple length scales. We show that different multipole deformation parameters affect different regions of transverse momentum transfer. These results have two important consequences: (1)Deformations of nuclear targets need to be taken into account when making predictions for and interpreting certain observables at the EIC. (2)Differential diffractive vector meson production has the potential to become a powerful tool, enabling the most direct measurements of nuclear structure at different length scales, ranging from large scale nuclear deformation at low transverse momentum transfer to fluctuations on nucleon- and subnucleon-size scales at higher transverse momentum transfer.

Triple differential cross sections for single ionization of an atom by bare ion impact

We present triple differential cross sections (TDCSs) for single ionization of atoms by proton and highly charged bare ions impact by means of the three-body formalism of the first Born, two-Coulomb wave and three-Coulomb (3C) wave (3CW) methods, respectively. The TDCS has been calculated both in the scattering and perpendicular planes. The purpose of this work is to investigate the validity of different methods as well as the role of interaction between projectile and residual-target-ion in the final state for weak perturbation strength with low electron emission energy at several momentum transfers. By comparing our calculations with experimental data, overall, the 3CW predicts better agreement with experiments than other calculations in the scattering plane. In the perpendicular plane, all calculations deviate from experimental data with increasing transverse momentum transfer for p − He collision. At low momentum transfer, the location of binary peak obtained by the first Born approximation calculation is well established with the experiment for proton impact. On the other hand, the 3CW model is in much better agreement with experiments, both in absolute values and peak position for highly charged impact. Finally, the strong influence of the internuclear Coulomb distortion on TDCS has been observed at low and intermediate momentum transfer.

Neutrino structure functions from GeV to EeV energies

The interpretation of present and future neutrino experiments requires accurate theoretical predictions for neutrino-nucleus scattering rates. Neutrino structure functions can be reliably evaluated in the deep-inelastic scattering regime within the perturbative QCD (pQCD) framework. At low momentum transfers (Q2 ≲ few GeV2), inelastic structure functions are however affected by large uncertainties which distort event rate predictions for neutrino energies Eν up to the TeV scale. Here we present a determination of neutrino inelastic structure functions valid for the complete range of energies relevant for phenomenology, from the GeV region entering oscillation analyses to the multi-EeV region accessible at neutrino telescopes. Our NNSFν approach combines a machine-learning parametrisation of experimental data with pQCD calculations based on state-of-the-art analyses of proton and nuclear parton distributions (PDFs). We compare our determination to other calculations, in particular to the popular Bodek-Yang model. We provide updated predictions for inclusive cross sections for a range of energies and target nuclei, including those relevant for LHC far-forward neutrino experiments such as FASERν, SND@LHC, and the Forward Physics Facility. The NNSFν determination is made available as fast interpolation LHAPDF grids, and it can be accessed both through an independent driver code and directly interfaced to neutrino event generators such as GENIE.

Pauli Exclusion Classical Potential for Intermediate-Energy Heavy-Ion Collisions

This article presents a classical potential used to describe nucleon–nucleon interactions at intermediate energies. The potential depends on the relative momentum of the colliding nucleons and can be used to describe interactions at low momentum transfer mimicking the Pauli exclusion principle. We use the potential with molecular dynamics to study finite nuclei, their binding energy, radii, symmetry energy, and a case study of collisions.

Probing Hadronic Interactions with Cosmic Rays

High-energy cosmic rays interact in the Earth’s atmosphere and produce extensive air showers (EASs) which can be measured with large detector arrays at the ground. The interpretation of these measurements relies on models of the EAS development which represents a challenge as well as an opportunity to test quantum chromodynamics (QCD) under extreme conditions. The EAS development is driven by hadron-ion collisions under low momentum transfer in the non-perturbative regime of QCD. Under these conditions, hadron production cannot be described using first principles and these interactions cannot be probed with existing collider experiments. Thus, accurate measurements of the EAS development provide a unique probe of multi-particle production in hadronic interactions.

VALIDATION OF A STOCHASTIC BREAKUP MODEL FOR TURBULENT JETS IN HIGH-SPEED CROSSFLOW: ASSESSMENT OF TURBULENT INTERACTIONS AND SENSITIVITY TO BOUNDARY CONDITIONS

Improving the mixing of fuel and air by injecting a turbulent liquid fuel jet into a high-speed cross-flowing gas can reduce the emissions of gas turbine applications. To facilitate and hasten the development of such low-emissions technologies, accurate predictions of the spray characteristics are needed. The objective of the present study is to validate the predictive capabilities of a stochastic breakup model for turbulent transverse jets over a wide range of representative pressures and atomization characteristics. The effect of turbulence modeling is also assessed to provide accurate and computationally less expensive Eulerian-Lagrangian transient approaches. To do so, the predictions made with the large eddy simulation (LES) approach for different subgrid-scale (SGS) models and with the synthetic eddy method (SEM) are compared to the ones made using the unsteady Reynolds-averaged Navier-Stokes (RANS) approach with and without a turbulent dispersion model. The sensitivity of the numerical methodology to the upstream velocity profile, pressure, and momentum flux ratio were also assessed. Properly accounting for the upstream gas velocity profile was found to be critical to ensure accurate predictions of the spray characteristics. The unsteady RANS (URANS) turbulent approach coupled with the turbulent dispersion model showed good agreement with experimental data, but the LES approach tends to overpredict the spray penetration and underpredict the Sauter mean diameter (SMD). This could be due to the lower turbulent interactions it predicts, which may lead to lower momentum transfer between the phases.

Interpolating between small- and large- g expansions using Bayesian model mixing

Bayesian model mixing (BMM) is a statistical technique that can be used to combine models that are predictive in different input domains into a composite distribution that has improved predictive power over the entire input space. We explore the application of BMM to the mixing of two expansions of a function of a coupling constant $g$ that are valid at small and large values of $g$ respectively. This type of problem is quite common in nuclear physics, where physical properties are straightforwardly calculable in strong and weak interaction limits or at low and high densities or momentum transfers, but difficult to calculate in between. Interpolation between these limits is often accomplished by a suitable interpolating function, e.g., Pad\'e approximants, but it is then unclear how to quantify the uncertainty of the interpolant. We address this problem in the simple context of the partition function of zero-dimensional ${\ensuremath{\phi}}^{4}$ theory, for which the (asymptotic) expansion at small $g$ and the (convergent) expansion at large $g$ are both known. We consider three mixing methods: linear mixture BMM, localized bivariate BMM, and localized multivariate BMM with Gaussian processes. We find that employing a Gaussian process in the intermediate region between the two predictive models leads to the best results of the three methods. The methods and validation strategies we present here should be generalizable to other nuclear physics settings.

A formalism to assess the accuracy of nuclear-structure weak interaction effects in precision β-decay studies

Multiple high precision β-decay measurements are being carried out these days on various nuclei, in search of beyond the Standard Model (SM) signatures. These measurements necessitate accurate SM theoretical predictions to be compared with. Motivated by the experimental surge, we present a formalism for such a calculation of β-decay observables, with controlled accuracy, based on a perturbative analysis of the theoretical observables related to the phenomena, including high order nuclear recoil and shape corrections. The accuracy of the corrections is analyzed by identifying a hierarchy of small parameters, related to the low-momentum transfer characterizing β-decays. Furthermore, we show that the sub-percent uncertainties, targeted by ongoing and planned experiments, entail an accuracy of the order of 10% for the solution of the nuclear many-body problem, which is well within the reach of modern nuclear theory for light to medium mass nuclei.

Consequences of the Dresden-II reactor data for the weak mixing angle and new physics

The Dresden-II reactor experiment has recently reported a suggestive evidence for the observation of coherent elastic neutrino-nucleus scattering, using a germanium detector. Given the low recoil energy threshold, these data are particularly interesting for a low-energy determination of the weak mixing angle and for the study of new physics leading to spectral distortions at low momentum transfer. Using two hypotheses for the quenching factor, we study the impact of the data on: (i) The weak mixing angle at a renormalization scale of ~ 10 MeV, (ii) neutrino generalized interactions with light mediators, (iii) the sterile neutrino dipole portal. The results for the weak mixing angle show a strong dependence on the quenching factor choice. Although still with large uncertainties, the Dresden-II data provide for the first time a determination of sin2θW at such scale using coherent elastic neutrino-nucleus scattering data. Tight upper limits are placed on the light vector, scalar and tensor mediator scenarios. Kinematic constraints implied by the reactor anti-neutrino flux and the ionization energy threshold allow the sterile neutrino dipole portal to produce up-scattering events with sterile neutrino masses up to ~ 8 MeV. In this context, we find that limits are also sensitive to the quenching factor choice, but in both cases competitive with those derived from XENON1T data and more stringent that those derived with COHERENT data, in the same sterile neutrino mass range.

Dominant Kitaev interactions in the honeycomb materials Na3Co2SbO6 and Na2Co2TeO6

Cobaltates with 3$d$ based layered honeycomb structure were recently proposed as Kitaev magnets and putative candidates to host the long-sought Kitaev spin liquid. Here we present inelastic neutron scattering results down to 50 mK for powder samples of Na$_3$Co$_2$SbO$_6$ and Na$_2$Co$_2$TeO$_6$, with high resolution in regions of low momentum and energy transfers. We compare the experimental data below the antiferromagnetic zigzag ordering temperature with dynamical structure factors obtained within spin wave theory. We search the wide parameter range of a $K$-$J_1$-$\Gamma$-$\Gamma^{\prime}$-$J_3$ spin 1/2 model and identify the best fits to constant momentum cuts of the inelastic neutron data. The powder average limits the selection of a unique parameter set for each material, but we see clear trends towards ferromagnetic Kitaev exchange in both compounds, and ratios $|K/J_1|$ could be as large as $5\ldots 25$; in contrast, antiferromagnetic Kitaev exchange cannot be ruled out, but requires a fine-tuning of all involved spin exchange couplings with only moderate ratio $|K/J_1| \sim 1$. Our experimental data are incompatible with a purely isotropic Heisenberg model.

CENTAUR-The small- and wide-angle neutron scattering diffractometer/spectrometer for the Second Target Station of the Spallation Neutron Source.

CENTAUR has been selected as one of the eight initial instruments to be built at the Second Target Station (STS) of the Spallation Neutron Source at Oak Ridge National Laboratory. It is a small-angle neutron scattering (SANS) and wide-angle neutron scattering (WANS) instrument with diffraction and spectroscopic capabilities. This instrument will maximally leverage the high brightness of the STS source, the state-of-the-art neutron optics, and a suite of detectors to deliver unprecedented capabilities that enable measurements over a wide range of length scales with excellent resolution, measurements on smaller samples, and time-resolved investigations of evolving structures. Notably, the simultaneous WANS and diffraction capability will be unique among neutron scattering instruments in the United States. This instrument will provide much needed capabilities for soft matter and polymer sciences, geology, biology, quantum condensed matter, and other materials sciences that need in situ and operando experiments for kinetic and/or out-of-equilibrium studies. Beam polarization and a high-resolution chopper will enable detailed structural and dynamical investigations of magnetic and quantum materials. CENTAUR's excellent resolution makes it ideal for low-angle diffraction studies of highly ordered large-scale structures, such as skyrmions, shear-induced ordering in colloids, and biomembranes. Additionally, the spectroscopic mode of this instrument extends to lower momentum transfers than are currently possible with existing spectrometers, thereby providing a unique capability for inelastic SANS studies.

VERDI: VERsatile DIffractometer with wide-angle polarization analysis for magnetic structure studies in powders and single crystals.

The VERsatile DIffractometer will set a new standard for a world-class magnetic diffractometer with versatility for both powder and single crystal samples and capability for wide-angle polarization analysis. The instrument will utilize a large single-frame bandwidth and will offer high-resolution at low momentum transfers and excellent signal-to-noise ratio. A horizontal elliptical mirror concept with interchangeable guide pieces will provide high flexibility in beam divergence to allow for a high-resolution powder mode, a high-intensity single crystal mode, and a polarized beam option. A major science focus will be quantum materials that exhibit emergent properties arising from collective effects in condensed matter. The unique use of polarized neutrons to isolate the magnetic signature will provide optimal experimental input to state-of-the-art modeling approaches to access detailed insight into local magnetic ordering.