Better angle on hadron transverse momentum distributions at the Electron-Ion Collider
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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Results for “elementary effects”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Comparison of post-Minkowskian and self-force expansions: Scattering in a scalar charge toy model
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Spectral flow in instanton computations and the β functions
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Signatures of vacuum birefringence in low-power flying focus pulses
Vacuum birefringence produces a differential phase between orthogonally polarized components of a weak electromagnetic probe in the presence of a strong electromagnetic field. Despite representing a hallmark prediction of quantum electrodynamics, vacuum birefringence remains untested in pure light configurations due to the extremely large electromagnetic fields required for a detectable phase difference. Here, we exploit the programmable focal velocity and extended focal range of a flying focus laser pulse to substantially lower the laser power required for detection of vacuum birefringence. In the proposed scheme, a linearly polarized x-ray probe pulse counterpropagates with respect to a flying focus pulse, whose focus moves at the speed of light in the same direction as the x-ray probe. The peak intensity of the flying focus pulse overlaps the probe over millimeter-scale distances and induces a polarization ellipticity on the order of 10 − 10 , which lies within the detection sensitivity of existing x-ray polarimeters. Published by the American Physical Society 2024
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Polarized 𝐽/𝜓 production in semi-inclusive DIS at large 𝑄 2 : Comparing quark fragmentation and photon-gluon fusion
We compare the relative importance of different mechanisms for polarized 𝐽/𝜓 production in semi-inclusive deep inelastic scattering processes at large 𝑄 2 . The transverse momentum dependent (TMD) factorization framework and nonrelativistic quantum chromodynamics are used to study the leading contributions from light quark fragmentation to polarized 𝐽/𝜓, and compared to direct production via photon-gluon fusion, which can proceed through color-singlet as well as color-octet mechanisms. We identify kinematic regimes where light quark fragmentation dominates, allowing for the extraction of the 3 𝑆$^{[8]}_{1}$ matrix element, as well as regimes where photon gluon fusion dominates, suggesting that the gluon TMD parton distribution function can be probed.
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Top quark electroweak dipole moment at a high energy muon collider
We study the sensitivity reach to probe the electroweak dipole operators associated with a top quark at a multi-TeV lepton collider. Studying the electroweak dipole operators is strongly motivated by precision physics. The operators exhibit unique chiral structure and can be enhanced with respect to others in theories beyond the Standard Model. We illustrate this point in a strongly coupled composite Higgs model. We find that a high energy μ + μ – collider may offer a unique opportunity to probe the electroweak dipole operators beyond the coverage by the LHC and future hadron colliders. The significant sensitivity is achieved by the leading channel μ + μ – → $t$$\overline{t}$ near the threshold, and substantially improved by the novel channel μ + μ – → $t$$\overline{t}$ℎ at high energies. We may be able to reach a new physics scale well above the collider energy for moderate couplings of the Wilson coefficients. Our main conclusions are applicable to future e + e – colliders.
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Noble dark matter: Surprising elusiveness of dark baryons
Dark matter could be a baryonic composite of stronglyc upled constituents transforming under SU(2) 𝐿 . We classify the SU(2) 𝐿 representations of baryons in a class of simple confining dark sectors and find that the lightest state can be a pure singlet or a singlet that mixes with other neutral components of SU(2) 𝐿 representations, which strongly suppresses the dark matter candidate’s interactions with the Standard Model. We focus on models with a confining SU(𝑁 𝑐 ) and heavy dark quarks constituting vectorlike 𝑁 𝑓 -plet of SU(2) 𝐿 . For benchmark 𝑁 𝑐 and 𝑁 𝑓 , we calculate baryon mass spectra, incorporating electroweak gauge boson exchange in the nonrelativistic quark model, and demonstrate that above TeV mass scales, dark matter is dominantly a singlet state. The combination of this singlet nature with the recently discovered ℋ-parity results in an inert state analogous to noble gases, hence we coin the term noble dark matter. Our results can be understood in the nonrelativistic effective theory that treats the dark baryons as elementary states, where we find singlets accompanying triplets, 5-plets, or more exotic representations. This generalization of WIMP-like theories is more difficult to find or rule out than dark matter models that include only a single SU(2) 𝐿 multiplet (such as a wino), motivating new searches in colliders and a reanalysis of direct and indirect detection prospects in astrophysical observations.
dark matter direct detection↗
Path from Lattice QCD to the Short-Distance Contribution to 0 ν β β Decay with a Light Majorana Neutrino
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Scattering Amplitudes and Conservative Binary Dynamics at O ( G 4 )
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Measurement of the Branching Fractions $\mathcal{B}(B^0 → p\bar{p}p\bar{p})$ and $\mathcal{B}(B^0_S → p\bar{p}p\bar{p})$
Searches for the rare hadronic decays $B^0 → p\bar{p}p\bar{p}$ and $B^0_S → p\bar{p}p\bar{p}$ are performed using proton-proton collision data recorded by the LHCb experiment and corresponding to an integrated luminosity of 9 fb –1 . Significances of 9.3σ and 4.0σ, including statistical and systematic uncertainties, are obtained for the $B^0 → p\bar{p}p\bar{p}$ and $B^0_S → p\bar{p}p\bar{p}$ signals, respectively. The branching fractions are measured relative to the topologically similar normalization decays B 0 → J/ψ(→ $p\bar{p}$)K* 0 (→ K + π – ) and B$^0_s$→J/ψ(→ $p\bar{p}$) $\phi$(→K + K – ). The branching fractions are measured to be $\mathcal{B}(B^0 → p\bar{p}p\bar{p})$ = (2.2 ± 0.4 ± 0.1 ± 0.1)×10 –8 and $\mathcal{B}(B^0_S → p\bar{p}p\bar{p})$ = (2.3 ± 1.0 ± 0.2 ± 0.1)×10 –8 . In these measurements, the first uncertainty is statistical, the second is systematic, and the third one is due to the external branching fraction of the normalization channel.
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Higgs potential from instantons
We propose that the Higgs potential, a key element in our understanding of nature, is partially generated by the instantons of new confining dynamics, perhaps from a hidden sector. In this picture, while the Higgs itself is a fundamental field, it controls the strength of the nonperturbative interactions that give rise to its potential. This setup can be realized in “Twin Higgs” hierarchy models, where the twin strong dynamics confines at or above the weak scale, but large quantum corrections to the Higgs potential are avoided. We examine a simple setup in which this instanton contribution is augmented by a quartic term, which is sufficient for a realistic electroweak symmetry breaking mechanism. The minimum of the potential is given by the Lambert 𝑊 0 function, with these assumptions. We discuss the predictions of this model and how it may be tested through measurements of the Higgs self coupling. Given the connection with nontrivial dynamics, one may also consider the prospects of accessing hidden sector states at colliders; this seems to be typically challenging in our setup. Symmetry restoration in the early Universe in this scenario is briefly examined. We also comment on the possible connection of our general setup with recent work on the physics of field space end points.
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Towards grounding nuclear physics in QCD
Exascale computing could soon enable a predictive theory of nuclear structure and reactions rooted in the Standard Model, with quantifiable and systematically improvable uncertainties. Such a predictive theory will help exploit experiments that use nucleons and nuclei as laboratories for testing the Standard Model and its limitations. Examples include direct dark matter detection, neutrinoless double beta decay, and searches for permanent electric dipole moments of the neutron and atoms. It will also help connect QCD to the properties of cold neutron stars and hot supernova cores. We discuss how a quantitative bridge between QCD and the properties of nuclei and nuclear matter will require a synthesis of lattice QCD (especially as applied to two- and three- nucleon interactions), effective field theory, and ab initio methods for solving the nuclear many-body problem. While there are significant challenges that must be addressed in developing this triad of theoretical tools, the rapid advance of computing is accelerating progress. In particular, we focus this review on the anticipated advances from lattice QCD and how these advances will impact few-body effective theories of nuclear physics by providing critical input, such as constraints on unknown low-energy constants of the effective (field) theories. We also review particular challenges that must be overcome for the successful application of lattice QCD for low-energy nuclear physics. We describe progress in developing few-body effective (field) theories of nuclear physics, with an emphasis on HOBET, a non-relativistic effective theory of nuclear physics, which is less common in the literature. We use the examples of neutrinoless double beta decay and the nuclear-matter equation of state to illustrate how the coupling of lattice QCD to effective theory might impact our understanding of symmetries and exotic astrophysical environments.
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Temperature effects on the neutron matter equation of state obtained from chiral effective field theory
Temperature effects on the neutron matter equation of state (EoS) are investigated in the framework of chiral effective field theory. Recently, state-of-the-art chiral two-nucleon forces are applied from third to fifth order in the chiral expansion together with chiral three-nucleon forces, allowing for a determination of the truncation error of the theoretical predictions. The thermodynamic quantities considered include the chemical potential, the internal energy, the entropy, and the free energy. In general, good order-by-order convergence of all predictions is observed. As to be expected, temperature effects are largest at low density. Finally, the temperature dependence of the chiral three-nucleon force turns out to be weak.
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Solvent Effects on Catalytic Reactions and Related Phenomena at Liquid-Solid Interfaces
Catalytic reactions involve the direct interaction of reactants, intermediates and products with the catalyst surface. We not only need to control the atomic structure and electronic properties of the active site, but also explore the multiple molecular interactions that occur beyond the active site; they play an essential role in altering the binding and reactivity of surface species. In liquid-phase catalysis, solvents provide additional degrees of freedom in the design of the catalytic process for desirable activity and selectivity. Here, the multi-faceted effects of solvents have a profound impact on the catalyst performance by restricting the mass transfer to the site, tuning the chemical potential of the surface species, competing for active sites, stabilizing the initial and transition states, and causing mechanistic changes by participating in the kinetically relevant elementary steps. This review addresses the different aspects of solvent effects, using a few prototype solid-liquid interfaces to illustrate these fundamental features. Recent experimental and computational studies that provide new insight at the molecular level are examined. Solvent structures in the proximity of the catalyst surface are discussed along with their influence in molecular binding and reaction at the solid-liquid interfaces. Furthermore, opportunities to alter such a solid-liquid interaction by tuning the wettability of the catalyst surfaces are explored.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
An effective field theory for non-maximal quantum chaos
In non-maximally quantum chaotic systems, the exponential behavior of out-of-time-ordered correlators (OTOCs) results from summing over exchanges of an infinite tower of higher “spin” operators. We construct an effective field theory (EFT) to capture these exchanges in (0 + 1) dimensions. The EFT generalizes the one for maximally chaotic systems, and reduces to it in the limit of maximal chaos. The theory predicts the general structure of OTOCs both at leading order in the 1/N expansion (N is the number of degrees of freedom), and after resuming over an infinite number of higher order 1/N corrections. These general results agree with those previously explicitly obtained in specific models. We also show that the general structure of the EFT can be extracted from the large q SYK model.
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The bottom-up EFT: complete UV resonances of the SMEFT operators
The standard model effective field theory (SMEFT) provides systematic parameterization of all possible new physics above the electroweak scale. According to the amplitude-operator correspondence, an effective operator can be decomposed into a linear combination of several j-basis operators, which correspond to local amplitudes carrying certain spin and gauge quantum numbers in a particular scattering channel. Based on the Poincare and gauge symmetries of scattering amplitude, we construct the j-basis using the Casimir method for both the Lorentz and gauge sectors. The quantum numbers of the j-basis operators fix the quantum numbers of any intermediate state in the corresponding amplitudes, such as a UV resonance. This can be re-interpreted as the j-basis/UV correspondence, thus obtaining the j-bases in all partitions of fields for an operator amounts to finding all of its UV origins at tree level, constituting the central part of the bottom-up EFT framework. Applying the j-basis analysis to SMEFT, we obtain a complete list of possible tree-level UV origins of the effective operators at the dimension 5, 6, 7, and all the bosonic operators at dimension 8.
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Counting linearly polarized gluons with lattice QCD
We outline an approach to calculate the transverse-momentum-dependent distribution of linearly polarized gluons inside an unpolarized hadron on the lattice with the help of large momentum effective theory. To achieve this purpose, we propose calculating a Euclidean version of the degree of polarization for a fast-moving hadron on the lattice, which is ultraviolet finite, and no soft function subtraction is needed. It indicates a practical way to explore the distribution of the linearly polarized gluons in a proton and the linearly polarized gluon effects in hadron collisions on the lattice.
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Unitarity bounds on effective field theories at the LHC
Effective Field Theory (EFT) extensions of the Standard Model are tools to compute observables (e.g. cross sections with partonic center-of-mass energy √s^) as a systematically improvable expansion suppressed by a new physics scale M. If one is interested in EFT predictions in the parameter space where M < √s^, concerns of self-consistency emerge, which can manifest as a violation of perturbative partial-wave unitarity. However, when we search for the effects of an EFT at a hadron collider with center-of-mass energy √s using an inclusive strategy, we typically do not have access to the event-by-event value of √s^. This motivates the need for a formalism that incorporates parton distribution functions into the perturbative partial-wave unitarity analysis. Developing such a framework and initiating an exploration of its implications is the goal of this work. Our approach opens up a potentially valid region of the EFT parameter space where M << √s. We provide evidence that there exist valid EFTs in this parameter space. The perturbative unitarity bounds are sensitive to the details of a given search, an effect we investigate by varying kinematic cuts.
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