Scalar Interactions Research Articles

Dark Energy and Dark Matter as Relative Energy between Quarks in Nucleon

Dark energy and dark matter in the universe are assigned to the positive and negative, respectively, “hidden” relative energies between the diquark and quark in nucleon in the scalar strong interaction hadron theory, SSI. The origin of the “darkness” is that quarks cannot be observed individually.

Neutrino scattering and B anomalies from hidden sector portals

We examine current constraints on and the future sensitivity to the strength of couplings between quarks and neutrinos in the presence of a form factor generated from loop effects of hidden sector particles that interact with quarks via new interactions. We consider models associated with either vector or scalar interactions of quarks and leptons generated by hidden sector dynamics. We study constraints on these models using data from coherent elastic neutrino-nucleus scattering and solar neutrino experiments and demonstrate how these new interactions may be discovered by utilizing the recoil spectra. We show that our framework can be naturally extended to explain the lepton universality violating neutral current B decay anomalies, and that in a model framework the constraints from neutrino scattering can have implications for these anomalies.

Dynamic Nuclear Polarization of 13 C Nuclei in the Liquid State over a 10 Tesla Field Range.

Nuclear magnetic resonance (NMR) techniques play an essential role in natural science and medicine. In spite of the tremendous utility associated with the small energies detected, the most severe limitation is the low signal-to-noise ratio. Dynamic nuclear polarization (DNP), a technique based on transfer of polarization from electron to nuclear spins, has emerged as a tool to enhance sensitivity of NMR. However, the approach in liquids still faces several challenges. Herein we report the observation of room-temperature, liquid DNP 13 C signal enhancements in organic small molecules as high as 600 at 9.4 Tesla and 800 at 1.2 Tesla. A mechanistic investigation of the 13 C-DNP field dependence shows that DNP efficiency is raised by proper choice of the polarizing agent (paramagnetic center) and by halogen atoms as mediators of scalar hyperfine interaction. Observation of sizable DNP of 13 CH2 and 13 CH3 groups in organic molecules at 9.4 T opens perspective for a broader application of this method.

Dynamic Nuclear Polarization of 13C Nuclei in the Liquid State over a 10 Tesla Field Range

AbstractNuclear magnetic resonance (NMR) techniques play an essential role in natural science and medicine. In spite of the tremendous utility associated with the small energies detected, the most severe limitation is the low signal‐to‐noise ratio. Dynamic nuclear polarization (DNP), a technique based on transfer of polarization from electron to nuclear spins, has emerged as a tool to enhance sensitivity of NMR. However, the approach in liquids still faces several challenges. Herein we report the observation of room‐temperature, liquid DNP 13C signal enhancements in organic small molecules as high as 600 at 9.4 Tesla and 800 at 1.2 Tesla. A mechanistic investigation of the 13C‐DNP field dependence shows that DNP efficiency is raised by proper choice of the polarizing agent (paramagnetic center) and by halogen atoms as mediators of scalar hyperfine interaction. Observation of sizable DNP of 13CH2 and 13CH3 groups in organic molecules at 9.4 T opens perspective for a broader application of this method.

Neutron dark matter decays and correlation coefficients of neutron β−-decays

As we have pointed out in (arXiv:1806.10107 [hep-ph]), the existence of neutron dark matter decay modes n→χ+anything, where χ is a dark matter fermion, for the solution of the neutron lifetime problem changes priorities and demands to describe the neutron lifetime τn=888.0(2.0)s, measured in beam experiments and defined by the decay modes n→p+anything, in the Standard Model (SM). The latter requires the axial coupling constant λ to be equal to λ=−1.2690 (arXiv:1806.10107 [hep-ph]). Since such an axial coupling constant is excluded by experimental data reported by the PERKEO II and UCNA Collaborations, the neutron lifetime τn=888.0(2.0)s can be explained only by virtue of interactions beyond the SM, namely, by the Fierz interference term of order b∼−10−2 dependent on scalar and tensor coupling constants. We give a complete analysis of all correlation coefficients of the neutron β−-decays with polarized neutron, taking into account the contributions of scalar and tensor interactions beyond the SM with the Fierz interference term b∼−10−2. We show that the obtained results agree well with contemporary experimental data that does not prevent the neutron with the rate of the decay modes n→p+anything, measured in beam experiments, to have dark matter decay modes n→χ+anything.

Effective-field theory analysis of the \u03c4\u2212 \u2192 \u03c0\u2212\u03c00\u03bd\u03c4 decays

We perform an effective field theory analysis of the τ− → π−π0ντ decays, that includes the most general interactions between Standard Model fields up to dimension six, assuming left-handed neutrinos. We constrain as much as possible the necessary Standard Model hadronic input using chiral symmetry, dispersion relations, data and asymptotic QCD properties. As a result, we show that it is possible to set precise (competitive with low-energy and LHC measurements) bounds on (non-standard) charged current tensor interactions, finding a very small preference for their presence, according to Belle data. Belle-II near future measurements can thus be very useful in either confirming or further restricting new physics tensor current contributions to these decays. For this, the spectrum in the di-pion invariant mass turns out to be particularly promising. Distributions in the angle defined by the τ− and π− momenta can also be helpful if measured with less than 10% accuracy, both for non-standard scalar and tensor interactions.

Dynamics and kinematics of the reactive scalar gradient in weakly turbulent premixed flames

In turbulent flames, chemical species mixing rates are controlled to a large extent by the geometric alignment of the species composition gradients with the local velocity gradients. This alignment indeed characterizes the turbulence–scalar interaction (TSI), which is one of the leading-order source terms in the scalar dissipation rate (SDR) evolution. In situations featuring density variations, which may be relevant either to (i) non-reactive but multiphase or compressible flows, or to (ii) reactive flows such as those considered herein, it should be acknowledged that there is still some controversy about the role of dilatational effects and its connection with the rotation of the strain-rate tensor principal axes. These two issues are analyzed by considering direct numerical simulation databases of flame kernel growth in homogeneous isotropic turbulence (HIT). Two distinct conditions of turbulence–combustion interaction (TCI) are considered: the first is a quasi-laminar reference case while the second displays some local thickening of the preheating zone. Special emphasis is placed on the kinematics of the scalar gradient orientation, which is studied through the direct inspection of the reactive scalar gradient orientation budget. To the best of the authors’ knowledge, this is first time that such a budget is scrutinized in premixed combustion conditions. The analysis shows that, for the flow conditions that are presently investigated, the role associated to the rotation of the strain-rate eigenframe is of paramount importance: it is the leading-order term in the scalar gradient orientation budget. This study also confirms that, in the vicinity of the flame, the resulting evolution opposes the rise of the reactive scalar gradient norm (i.e., the rise of the SDR) but the corresponding effects are lessened as the normalized root mean square (RMS) of the velocity fluctuations is increased.

COHERENT analysis of neutrino generalized interactions

Effective neutrino-quark generalized interactions are entirely determined by Lorentz invariance, so they include all possible four-fermion non derivative Lorentz structures. They contain neutrino-quark non-standard interactions as a subset, but span over a larger set that involves effective scalar, pseudoscalar, axial and tensor operators. Using recent COHERENT data, we derive constraints on the corresponding couplings by considering scalar, vector and tensor quark currents and assuming no lepton flavor dependence. We allow for mixed neutrino-quark Lorentz couplings and consider two types of scenarios in which: (i) one interaction at the nuclear level is present at a time, (ii) two interactions are simultaneously present. For scenarios (i) our findings show that scalar interactions are the most severely constrained, in particular for pseudoscalar-scalar neutrino-quark couplings. In contrast, tensor and non-standard vector interactions still enable for sizable effective parameters. We find as well that an extra vector interaction improves the data fit when compared with the result derived assuming only the standard model contribution. In scenarios (ii) the presence of two interactions relaxes the bounds and opens regions in parameter space that are otherwise closed, with the effect being more pronounced in the scalar-vector and scalar-tensor cases. We point out that barring the vector case, our results represent the most stringent bounds on effective neutrino-quark generalized interactions for mediator masses of order $\sim 1\,$GeV. They hold as well for larger mediator masses, case in which they should be compared with limits from neutrino deep-inelastic scattering data.

Posner qubits: spin dynamics of entangled Ca9(PO4)6 molecules and their role in neural processing.

It has been suggested that 31P nuclear spins in Ca9(PO4)6 molecules could form the basis of a quantum mechanism for neural processing in the brain. A fundamental requirement of this proposal is that spins in different Ca9(PO4)6 molecules can become entangled and remain so for periods (estimated at many hours) that hugely exceed typical 31P spin relaxation times. Here, we consider the coherent and incoherent spin dynamics of Ca9(PO4)6 arising from dipolar and scalar spin-spin interactions and derive an upper bound of 37 min on the entanglement lifetime under idealized physiological conditions. We argue that the spin relaxation in Ca9(PO4)6 is likely to be much faster than this estimate.

Klein–Gordon field in spinning cosmic-string space-time with the Cornell potential

We study the relativistic quantum dynamics of a Klein–Gordon scalar field subject to a Cornell potential in spinning cosmic-string space-time, in order to better understand the effects of gravitational fields produced by topological defects on the scalar field. We solve the Klein–Gordon equation in the presence of scalar and vector interactions by utilizing the Nikiforov–Uvarov formalism and two ansätze, one of which leads to a biconfluent Heun differential equation. We obtain the wave-functions and the energy levels of the relativistic field in that space-time. We discuss the effect of various physical parameters and quantum numbers on the wave-functions.

Tests of the standard model in neutron β decay with a polarized neutron and electron and an unpolarized proton

We analyse the electron--energy and angular distribution of the neutron beta decay with polarized neutron and electron and unpolarized proton, calculated in Phys. Rev. C 95, 055502 (2017) within the Standard Model (SM), by taking into account the contributions of interactions beyond the SM. After the absorption of vector and axial vector contributions by the axial coupling constant and Cabibbo-Kobayashi-Maskawa (CKM) matrix element (Bhattacharya et al., Phys. Rev. D 85, 054512 (2012) and so on) these are the contributions of scalar and tensor interactions only. The neutron lifetime, correlation coefficients and their averaged values, and asymmetries of the neutron beta decay with polarized neutron and electron are adapted to the analysis of experimental data on searches of contributions of interactions beyond the SM. Using the obtained results we propose some estimates of the values of the scalar and tensor coupling constants of interactions beyond the SM. We use the estimate of the Fierz interference term "b_F = - 0.0028 +/- 0.0026" by Hardy and Towner (Phys. Rev. C 91, 025501 (2015)), the neutron lifetime "tau_n = 880.2(1.0)s"(Particle Data Group, Chin. Phys. C 40, 100001 (2016)) and the experimental data "N_{\exp} = 0.067 +/- 0.011_{\rm stat.} +/- 0.004_{\rm syst.}" for the averaged value of the correlation coefficient of the neutron-electron spin-spin correlations, measured by Kozela et al. (Phys. Ref. C 85, 045501 (2012)). The contributions of G-odd correlations are calculated and found at the level of 10^{-5} in agreement with the results obtained by Gardner and Plaster (Phys. Rev. C 87, 065504 (2013)).

Overhauser DNP FFC study of block copolymer diluted solution

Overhauser dynamic nuclear polarization (DNP) is the dominating hyperpolarization technique to increasing the nuclear magnetic resonance signal in liquids and diluted systems. The enhancement obtained depends on the overall mobility of the radical-carrying molecule but also on its specific interaction with the host molecules. Information about the nature of molecular and radical dynamics can be identified from determining the nuclear T1 as a function of Larmor frequency by Fast Field Cycling (FFC) relaxometry. In this work, DNP and FFC methods were combined for a detailed study of 1H Overhauser DNP enhancements at 340 mT (X-band) and 73 mT (S-band) for diluted solutions of a block-copolymer with and without the addition of TEMPO radicals. NMR relaxation dispersions of these solutions are measured at thermal polarization and DNP conditions in the X-band, and the obtained DNP data were analyzed by a model of electron-nucleus interactions modulated by translational diffusion. The coupling factors for the two different blocks of the copolymer are obtained independently from DNP and NMRD experiments. An additional contribution from scalar interactions was found for polystyrene blocks.

Doubly-charged scalars in the type II seesaw mechanism: Fundamental symmetry tests and high-energy searches

We analyze the sensitivity of low-energy fundamental symmetry tests to interactions mediated by doubly-charged scalars that arise in type II seesaw models of neutrino mass and their left-right symmetric extensions. We focus on the next generation measurement of the parity-violating asymmetry in M\o{}ller scattering planned by the MOLLER collaboration at Jefferson Laboratory. We compare the MOLLER sensitivity to that of searches for charged lepton flavor violation (CLFV) and neutrinoless double beta-decay ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay) as well as present and possible future high-energy collider probes. We show that for the simplest type-II seesaw scenario, CLFV searches have the greatest sensitivity. However, in a left-right symmetric extension where the scale of parity-breaking is decoupled from the $SU(2{)}_{R}$-breaking scale, the MOLLER experiment will provide a unique probe of scalar triplet interactions in the right-handed sector for a doubly-charged scalar mass up to $\ensuremath{\sim}10\text{ }\text{ }\mathrm{TeV}$ and help elucidate the mechanism of $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay.

Isovector charges of the nucleon from 2+1+1 -flavor lattice QCD

We present high statistics results for the isovector charges $g^{u-d}_A$, $g^{u-d}_S$ and $g^{u-d}_T$ of the nucleon. Calculations were carried out on eleven ensembles of gauge configurations generated by the MILC collaboration using highly improved staggered quarks (HISQ) action with 2+1+1 dynamical flavors. These ensembles span four lattice spacings $a \approx$ 0.06, 0.09, 0.12 and 0.15 fm and light-quark masses corresponding to $M_\pi \approx$ 135, 225 and 315 MeV. Excited-state contamination in the nucleon 3-point correlation functions is controlled by including up to three-states in the spectral decomposition. Remaining systematic uncertainties associated with lattice discretization, lattice volume and light-quark masses are controlled using a simultaneous fit in these three variables. Our final estimates of the isovector charges in the $\overline{\text{MS}}$ scheme at 2 GeV are $g_A^{u-d} = 1.218(25)(30)$, $g_S^{u-d} = 1.022(80)(60) $ and $g_T^{u-d} = 0.989(32)(10)$. The first error includes statistical and all systematic uncertainties except that due to the extrapolation ansatz, which is given by the second error estimate. We provide a detailed comparison with the recent result of $g_A^{u-d} = 1.271(13)$ by the CalLat collaboration and argue that our error estimate is more realistic. Combining our estimate for $g_S^{u-d}$ with the difference of light quarks masses $(m_d-m_u)^{\rm QCD}=2.572(66)$ MeV given by the MILC/Fermilab/TUMQCD collaboration for 2+1+1-flavor theory, we obtain $(M_N-M_P)^{\rm QCD} = 2.63(27)$ MeV. We update the low-energy constraints on novel scalar and tensor interactions, $\epsilon_{S}$ and $\epsilon_{T}$, at the TeV scale by combining our new estimates for $g^{u-d}_S$ and $g^{u-d}_T$ with precision low-energy nuclear experiments, and find them comparable to those from the ATLAS and the CMS experiments at the LHC.

Behind Horndeski: structurally robust higher derivative EFTs

Higher derivative scalar interactions can give rise to interesting cosmological scenarios. We present a complete classification of such operators that can yield sizeable effects without introducing ghosts and, at the same time, define an effective field theory robust under the inclusion of quantum corrections. A set of rules to power count consistently the coefficients of the resulting Lagrangian is provided by the presence of an approximate global symmetry. The interactions that we derive in this way contain a subset of the so-called Horndeski and beyond Horndeski theories. Our construction therefore provides a structurally robust context to study their phenomenology. Applications to dark energy/modified gravity and geodesically complete cosmologies are briefly discussed.

Asymmetric magnetized QCD matter realized by scalar and instanton-induced interactions

In a strong magnetic field utilizing a two-flavor NJL model, the isospin symmetry and asymmetry can be realized by altering the fraction parameter [Formula: see text] of the two kinds of interactions, i.e. the scalar coupling and instanton-induced coupling. As [Formula: see text] increases, the [Formula: see text] quark mass decreases while [Formula: see text] quark mass increases monotonously. The two mass lines cross at [Formula: see text] with an isospin symmetry mass [Formula: see text]. Even in the flavor-decoupled state, i.e. the strong isospin asymmetry, the [Formula: see text] and [Formula: see text] mass lines can have a common mass at a critical temperature [Formula: see text]. As the magnetic field becomes stronger, the [Formula: see text] will move towards the chiral restoration phase. The strong isospin asymmetry will lead to a split of the pseudocritical temperatures for [Formula: see text] and [Formula: see text] quarks, which can be reflected by the two peaks of the specific heat and sound velocity.

A new mechanism of sterile neutrino dark matter production

We consider a scenario where the dark matter candidate is a sterile neutrino with sizable self-interactions, described by a dimension-six operator, and with negligible interactions with the Standard Model. The relic abundance is set by the freeze-out of 4-to-2 annihilations in the dark sector plasma and reproduces the observed dark matter abundance when the sterile neutrino mass is in the range ∼ 500 keV – 20 GeV. The feeble interactions with the Standard Model may lead to observable signals from dark matter decay. Furthermore, the self-interactions can affect the formation of small scale structures. We also implement this mechanism in a concrete model where the sterile neutrino self-interaction is due to the exchange of a singlet scalar, and we discuss the relevance of the scalar portal interactions for constructing a complete thermal history of the dark sector.

Dirac operators with Lorentz scalar shell interactions

This paper deals with the massive three-dimensional Dirac operator coupled with a Lorentz scalar shell interaction supported on a compact smooth surface. The rigorous definition of the operator involves suitable transmission conditions along the surface. After showing the self-adjointness of the resulting operator, we switch to the investigation of its spectral properties, in particular, to the existence and non-existence of eigenvalues. In the case of an attractive coupling, we study the eigenvalue asymptotics as the mass becomes large and show that the behavior of the individual eigenvalues and their total number are governed by an effective Schrödinger operator on the boundary with an external Yang–Mills potential and a curvature-induced potential.

Angular and polarization trails from effective interactions of Majorana neutrinos at the LHeC

We study the possibility of the LHeC facility to disentangle different new physics contributions to the production of heavy sterile Majorana neutrinos in the lepton number violating channel e^{-}prightarrow l_{j}^{+} + 3 mathrm{jets} (l_jequiv e ,mu ). This is done investigating the angular and polarization trails of effective operators with distinct Dirac–Lorentz structure contributing to the Majorana neutrino production, which parameterize new physics from a higher energy scale. We study an asymmetry in the angular distribution of the final anti-lepton and the initial electron polarization effect on the number of signal events produced by the vectorial and scalar effective interactions, finding both analyses could well separate their contributions.

Lefschetz thimbles in fermionic effective models with repulsive vector-field

We discuss two problems in complexified auxiliary fields in fermionic effective models, the auxiliary sign problem associated with the repulsive vector-field and the choice of the cut for the scalar field appearing from the logarithmic function. In the fermionic effective models with attractive scalar and repulsive vector-type interaction, the auxiliary scalar and vector fields appear in the path integral after the bosonization of fermion bilinears. When we make the path integral well-defined by the Wick rotation of the vector field, the oscillating Boltzmann weight appears in the partition function. This “auxiliary” sign problem can be solved by using the Lefschetz-thimble path-integral method, where the integration path is constructed in the complex plane. Another serious obstacle in the numerical construction of Lefschetz thimbles is caused by singular points and cuts induced by multivalued functions of the complexified scalar field in the momentum integration. We propose a new prescription which fixes gradient flow trajectories on the same Riemann sheet in the flow evolution by performing the momentum integration in the complex domain.