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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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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Signals with six bottom quarks for charged and neutral Higgs bosons

In extensions of two Higgs doublet models with vectorlike quarks, the decays of vectorlike quarks may easily be dominated by cascade decays through charged or neutral Higgs bosons leading to signatures with 6 top or bottom quarks. Since top quark decays also contain bottom quarks, a common signature for many possible decay chains is 6 bottom quarks in the final state. We present a search strategy focusing on this final state and find the mass ranges of vectorlike quarks and Higgs bosons that can be explored at the Large Hadron Collider. Among other results, the sensitivity to the charged and neutral Higgs bosons, extending to about 2 TeV, stands out when compared to models without vectorlike matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

FIMP dark matter from flavon portals

We investigate the phenomenology of a non-thermal dark matter (DM) candidate in the context of flavor models that explain the hierarchy in the masses and mixings of quarks and leptons via the Froggatt-Nielsen (FN) mechanism. A flavor-dependent U(1) FN symmetry explains the fermion mass and mixing hierarchy, and also provides a mechanism for suppressed interactions of the DM, assumed to be a Majorana fermion, with the Standard Model (SM) particles, resulting in its FIMP (feebly interacting massive particle) character. Such feeble interactions are mediated by a flavon field through higher dimensional operators governed by the U(1) FN charges. We point out a natural stabilizing mechanism for the DM within this framework with the choice of half-integer U(1) FN charge n for the DM fermion, along with integer charges for the SM fermions and the flavon field. In this flavon portal scenario, the DM is non-thermally produced from the decay of the flavon in the early universe which becomes a relic through the freeze-in mechanism. We explore the allowed parameter space for this DM candidate from relic abundance by solving the relevant Boltzmann equations. We find that reproducing the correct relic density requires the DM mass to be in the range (100 – 300) keV for n = 7.5 and (3 – 10) MeV for n = 8.5 where n is the U(1) FN charge of the DM fermion.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Neutron Electric Dipole Moments with Clover Fermions

We present preliminary results for the contributions to the neutron EDM arising from the QCD θ-term, the Weinberg three-gluon and the quark chromo-EDM operators from our ongoing lattice calculations using clover valence quarks on the MILC HISQ lattices. We use the gradient-flow technique to smooth the lattices and renormalize the gluonic operators, and use the Schwinger source method to incorporate the quark chromo-EDM interactions in the quark propagator. For the QCD θ-term and the Weinberg three-gluon operator, we report results in the gradient-flow scheme from 8 ensembles at four lattice spacings and three pion masses, including 2 physical pion mass ensembles. For the quark chromo-EDM, unrenormalized results are presented at two lattice spacings, a=0.12 and 0.09 fm, and two pion masses, M π =310 MeV and 220 MeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Higgs alignment and the top quark

There is a surprising connection between the top quark and Higgs alignment in Gildener-Weinberg multi-Higgs doublet models. Were it not for the top quark and its large mass, the coupling of the 125 GeV Higgs boson H to gauge bosons and fermions would be indistinguishable from those of the Standard Model Higgs. The top quark’s coupling to a single Higgs doublet breaks this perfect alignment in higher orders of the Coleman-Weinberg loop expansion of the effective potential. But the effect is still small, ≲O(1%), and probably experimentally inaccessible.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Lattice B -field correlators for heavy quarks

We analyze the color-magnetic (or “ B ”) field two-point function that encodes the finite-mass correction to the heavy-quark momentum-diffusion coefficient. The simulations are done on fine isotropic lattices in the quenched approximation at 1.5 T c , using a range of gradient flow times for noise suppression and operator renormalization. The continuum extrapolation is performed at fixed flow time followed by a second extrapolation to zero flow time. Perturbative calculations to next-to-leading order of this correlation function, matching gradient-flowed correlators to MS ¯ , are used to resolve nontrivial renormalization issues. We perform a spectral reconstruction based on perturbative model fits to estimate the coefficient κ B of the finite-mass correction to the heavy-quark momentum-diffusion coefficient. The approach we present here yields high-precision data for the correlator with all renormalization issues incorporated at next-to-leading order and is also applicable for actions with dynamical fermions. Published by the American Physical Society 2024

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Measuring spin correlation between quarks during QCD confinement

The vacuum is now understood to have a rich and complex structure, characterized by fluctuating energy fields and a condensate of virtual quark–antiquark pairs. The spontaneous breaking of the approximate chiral symmetry, signalled by the nonvanishing quark condensate $\langle$$q\bar{q}$$\rangle$, is dynamically generated through topologically nontrivial gauge configurations such as instantons. The precise mechanism linking the chiral symmetry breaking to the mass generation associated with quark confinement remains a profound open question in quantum chromodynamics (QCD)—the fundamental theory of strong interaction. High-energy proton–proton collisions could liberate virtual quark–antiquark pairs from the vacuum that subsequently undergo confinement to form hadrons, whose properties could serve as probes into QCD confinement and the quark condensate. Here we report evidence of spin correlations in $Λ\bar{Λ}$ hyperon pairs inherited from spin-correlated strange quark–antiquark virtual pairs. Measurements by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory reveal a relative polarization signal of (18 ± 4)% that links the virtual spin-correlated quark pairs from the QCD vacuum to their final-state hadron counterparts. Crucially, this correlation vanishes when the hyperon pairs are widely separated in angle, consistent with the decoherence of the quantum system. Our findings provide a new experimental model for exploring the dynamics and interplay of quark confinement and entanglement.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Investigating charm quark energy loss in medium with the nuclear modification factor of D 0 -tagged jets

The nuclear modification factor R AA of charm jets, identified by the presence of a D 0 meson among the jet constituents, has been measured for the first time in Pb–Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{NN}} = 5.02$ TeV with the ALICE detector at the LHC. The D 0 mesons and their charge conjugates are reconstructed from the hadronic decay D 0 → K – π + . Jets are reconstructed from D 0 -meson candidates and charged particles using the anti-k T algorithm with jet resolution parameter R = 0.3, in the jet transverse momentum (p T ) range 5 < $p^{ch}_{T}$$^{jet}$ < 50 GeV/c and pseudorapidity |η ch jet| < 0.6. A hint of reduced suppression in the charm-jet R AA is observed in comparison to inclusive jets in central Pb–Pb collisions with a significance of about 2σ in 20 < $p^{ch}_{T}$$^{jet}$ < 50 GeV/c, suggesting the in-medium energy loss to depend on both the difference between quark and gluon coupling strength (Casimir colour-charge effect) and quark mass (dead-cone effect). The data are compared with model calculations that include mass effects in the in-medium energy loss. Several state-of-the-art models are consistent with the data, with the LIDO model providing the best description of the data in the common kinematic range of inclusive and D 0 -tagged jets, highlighting the role of mass effects in interpreting the results.

Acharya, S. (ORCID:0000000292135329)↗
DOE OSTI2021

Charged and neutral Higgs bosons in final states with 6 bottom quarks

In extensions of two Higgs doublet models with vectorlike quarks, the decays of vectorlike quarks may be easily dominated by cascade decays through charged or neutral Higgs bosons leading to signatures with 6 top or bottom quarks. Since top quark decays also contain bottom quarks, the 6 bottom quarks in final states is a common signature to a large class of possible decay chains. We present a search strategy focusing on this final state and find the mass ranges of vectorlike quarks and Higgs bosons that can be explored at the Large Hadron Collider. Among other results the sensitivity to the charged Higgs boson, extending above 2 TeV, stands out when compared to models without vectorlike matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

LHC probes of the 10 TeV scale

The usual range of new particle masses, up to a few TeV, searched for at the LHC may be substantially extended if ultraheavy diquark particles exist. A diquark scalar, $S_{uu}$, that interacts perturbatively with two up quarks may be as heavy as 10 TeV and would still produce tens of spectacular events at the 14 TeV LHC. It is shown here that an ultraheavy $S_{uu}$ could be discovered through final states of very high energy in various channels, especially if the diquark can decay into other new heavy particles. Examples include cascade decays of $S_{uu}$ via a second scalar produced in pairs, which leads to two dijet resonances, or to more exotic signals with top quarks, Higgs bosons, electroweak bosons, and high-$p_T$ jets. Another possibility is that the diquark decays into a vectorlike quark of multi-TeV mass and a top or up quark. Signal events include one or two highly boosted top quarks and a Higgs boson or a $Z$, without counterparts containing top antiquarks. Similarly, direct decays of the diquark into $tj$ or $tt$ with leptonic top decays involve only positively charged leptons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

A natural mechanism for approximate Higgs alignment in the 2HDM

The 2HDM possesses a neutral scalar interaction eigenstate whose tree-level properties coincide with the Standard Model (SM) Higgs boson. In light of the LHC Higgs data which suggests that the observed Higgs boson is SM-like, it follows that the mixing of the SM Higgs interaction eigenstate with the other neutral scalar interaction eigenstates of the 2HDM should be suppressed, corresponding to the so-called Higgs alignment limit. The exact Higgs alignment limit can arise naturally due to a global symmetry of the scalar potential. If this symmetry is softly broken, then the Higgs alignment limit becomes approximate (although still potentially consistent with the current LHC Higgs data). In this paper, we obtain the approximate Higgs alignment suggested by the LHC Higgs data as a consequence of a softly broken global symmetry of the Higgs Lagrangian. However, this can only be accomplished if the Yukawa sector of the theory is extended. We propose an extended 2HDM with vector-like top quark partners, where explicit mass terms in the top sector provide the source of the soft symmetry breaking of a generalized CP symmetry. In this way, we can realize approximate Higgs alignment without a significant fine-tuning of the model parameters. We then explore the implications of the current LHC bounds on vector-like top quark partners for the success of our proposed scenario.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Deciphering the mechanism of near-threshold $$J/\psi $$ photoproduction

Abstract The photoproduction of the $$J/\psi $$ J / ψ off the proton is believed to deepen our understanding of various physics issues. On the one hand, it is proposed to provide access to the origin of the proton mass, based on the QCD multipole expansion. On the other hand, it can be employed in a study of pentaquark states. The process is usually assumed to proceed through vector-meson dominance, that is the photon couples to a $$J/\psi $$ J / ψ which rescatters with the proton to give the $$J/\psi p$$ J / ψ p final state. In this paper, we provide a compelling hint for and propose measurements necessary to confirm a novel production mechanism via the $$\varLambda _c \bar{D}^{(*)}$$ Λ c D ¯ ( ∗ ) intermediate states. In particular, there must be cusp structures at the $$\varLambda _c \bar{D}^{(*)}$$ Λ c D ¯ ( ∗ ) thresholds in the energy dependence of the $$J/\psi $$ J / ψ photoproduction cross section. The same mechanism also implies the $$J/\psi $$ J / ψ -nucleon scattering lengths of order 1 mfm. Given this, one expects only a minor contribution of charm quarks to the nucleon mass.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

𝐵 → 𝜌⁢ℓ⁢$\bar{v}$ Resonance Form Factors from 𝐵→ 𝜋⁢𝜋⁢ℓ⁢$\bar{v}$ in Lattice QCD

The decay 𝐵 → 𝜌⁢ℓ⁢$\bar{v}$ is an attractive process for determining the magnitude of the smallest Cabibbo-Kobayashi-Maskawa matrix element, |𝑉 𝑢⁢𝑏 |, and can provide new insights into the origin of the long-standing exclusive-inclusive discrepancy in determinations of this standard-model parameter. This requires a nonperturbative QCD calculation of the 𝐵 → 𝜌 form factors 𝑉, 𝐴 0 , 𝐴 1 , and 𝐴 12 . The unstable nature of the 𝜌 resonance has prevented precise lattice QCD calculations of these form factors to date. Here, we present the first lattice QCD calculation of the 𝐵 → 𝜌 form factors in which the 𝜌 is treated properly as a resonance in 𝑃-wave 𝜋⁢𝜋 scattering. To this end, we use the Lellouch-Lüscher finite-volume formalism to compute the 𝐵 → 𝜋⁢𝜋 form factors as a function of both momentum transfer and 𝜋⁢𝜋 invariant mass, and then analytically continue to the 𝜌 resonance pole. This calculation is performed with 2 + 1 dynamical quark flavors at a pion mass of approximately 320 MeV, and demonstrates a clear path toward results at the physical point.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

An analytic result for the 0 → ggHHH amplitude

We present a fully analytic calculation of the leading-order one-loop amplitude for triple Higgs production via gluon fusion, gg → HHH, retaining full dependence on the mass of the heavy quark circulating in the loop. This amplitude provides a direct probe of the triple and quartic Higgs self-couplings, the measurement of which is a central goal of current and future colliders. The amplitude can be presented in compact form thanks to the use of analytic reconstruction techniques, based on finite-field and p-adic evaluations, multivariate partial fraction decompositions, and primary decompositions to identify common numerator factors. Although full analytic results are given in the text and in the supplementary material, the main thrust of this paper is to further test and illustrate these analytic reconstruction techniques in a concrete physical example. Our results provide a compact and efficient representation of the matrix element for this process, enabling evaluations that are more than an order of magnitude faster than existing numerical alternatives. Full analytic control of the leading-order, loop-induced amplitude is an important step towards handling more complex 2-loop or real-radiation corrections to this and related processes.

Campbell, John M. [Fermilab] (ORCID:00000002136193↗
DOE OSTI2021

Complementarity between neutrinoless double beta decay and collider searches for heavy neutrinos in composite-fermion models

Composite-fermion models predict excited quarks and leptons with mass scales which can potentially be observed at high-energy colliders like the LHC; the most recent exclusion limits from the CMS and ATLAS Collaborations corner excited-fermion masses and the compositeness scale to the multi-TeV range. At the same time, hypothetical composite Majorana neutrinos would lead to observable effects in neutrinoless double beta decay ($0\nu \beta \beta$) experiments. In this work, we show that the current composite-neutrino exclusion limit $M_N>4.6$ TeV, as extracted from direct searches at the LHC, can indeed be further improved to $M_N>8.8$ TeV by including the bound on the nuclear transition $^{136}$Xe $\to ^{136}$Ba + $2e^-$. Looking ahead, the forthcoming HL-LHC will allow probing a larger portion of the parameter-space, nevertheless, it will still benefit from the complementary limit provided by $0 \nu \beta \beta$ future detectors to explore composite-neutrino masses up to $12.6$ TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for pair-produced vector-like top and bottom partners in events with large missing transverse momentum in $pp$ collisions with the ATLAS detector

A search for pair-produced vector-like quarks using events with exactly one lepton ($e$ or $μ$), at least four jets including at least one $b$-tagged jet, and large missing transverse momentum is presented. Data from proton–proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV, recorded by the ATLAS detector at the LHC from 2015 to 2018 and corresponding to an integrated luminosity of 139 fb –1 , are analysed. Vector-like partners $T$ and $B$ of the top and bottom quarks are considered, as is a vector-like $X$ with charge +5/3, assuming their decay into a $W$, $Z$, or Higgs boson and a third-generation quark. No significant deviations from the Standard Model expectation are observed. Upper limits on the production cross-section of $T$ and $B$ quark pairs as a function of their mass are derived for various decay branching ratio scenarios. The strongest lower limits on the masses are 1.59 assuming mass-degenerate vector-like quarks and branching ratios corresponding to the weak-isospin doublet model, and 1.47 TeV (1.46 TeV) for exclusive $T$→$Zt$ ($B/X$→$Wt$) decays. In addition, lower limits on the $T$ and $B$ quark masses are derived for all possible branching ratios.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Proton decay from quark and lepton compositeness

Within a chiral SU(15) gauge theory in which the Standard Model fermions are bound states of massless preons, we show that proton-decay operators are likely induced at the compositeness scale, Λ pre . Our estimate of the limit imposed by searches for proton decays is Λ pre > 10 4 TeV 1/2 $C^{1/4}_{8} m^{1/2}_{Q}$, where C 8 is a rescaled coefficient of an 8-prebaryon operator induced by SU(15) dynamics, and m Q is the mass of a composite vectorlike quark. The latter has a lower limit related to the mass of a composite vectorlike lepton, which in turn is required by LHC searches to be above 1 TeV. For C 8 in the 10 –5 – 1 range, the lower limit on Λ pre varies between 3 × 10 3 TeV and 5 × 10 4 TeV. We point out that exotic proton decay modes, into a π + and a heavy right-handed neutrino, could be observed using the Super-Kamiokande or DUNE detectors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the top quark-antiquark pair charge asymmetry in events with highly boosted top quarks in proton-proton collisions at 13 TeV with the CMS detector

The top quark is the heaviest elementary particle, making it a unique tool to search for new physics. In this talk, I will present a new measurement of the top quark pair charge asymmetry for highly boosted top quarks decaying to a single lepton, missing transverse momentum and jets. The analysis is performed on 13TeV proton-proton collision data recorded by the CMS experiment during Run 2. We have defined a dedicated phase space that selects top quark-antiquark pairs with invariant mass greater than 750GeV in a semileptonic final state where the lepton is not necessarily isolated. This highly boosted sample is enhanced in valence quark production and thus expected to be more sensitive to deviations in the charge asymmetry caused by BSM processes. Dedicated tagging techniques are used to identify the decay products of hadronic top quarks and W bosons. An unfolding procedure is used to correct for detector resolution and acceptance, and inefficiencies in the event reconstruction. The result is presented in the full phase space at parton level and can be used as input to global EFT interpretations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗