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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Measurement of the ratio of the $𝐵^+_𝑐 → 𝐽/𝜓⁢𝜏^+⁢𝜈_𝜏$ and $𝐵^+_𝑐 → 𝐽/𝜓⁢𝜇^+⁢𝜈_𝜇$ branching fractions using three-prong 𝜏 lepton decays

The ratio between the $𝐵^+_𝑐 → 𝐽/𝜓⁢𝜏^+⁢𝜈_𝜏$ and $𝐵^+_𝑐 → 𝐽/𝜓⁢𝜇^+⁢𝜈_𝜇$ branching fractions is measured using a data sample of proton-proton collisions collected by CMS at a center-of-mass energy of 13 TeV in the years 2016–2018 and corresponding to an integrated luminosity of 138 fb −1 . The 𝐽/𝜓 meson is identified through its 𝐽/𝜓 → 𝜇 + ⁢𝜇 − decay and the tau lepton is reconstructed in the hadronic three-prong final state. The measured ratio of branching fractions in this tau decay mode, ℛ had 𝐽/𝜓 = $1.0⁢4^{+0.50}_{−0.44}$, is combined with the previous analysis based on the 𝜏 + $→ 𝜇^+⁢𝜈_𝜇\bar{𝜈}_𝜏$ leptonic decay channel, leading to ℛ 𝐽/𝜓 = 0.49 ± 0.26. As this result is consistent with the standard model prediction of 0.258 ± 0.004, no evidence of lepton flavor universality violation is found.

Chekhovsky, V. [Yerevan Physics Institute]↗
DOE OSTI2025

Deviations from the Porter-Thomas Distribution due to Nonstatistical 𝛾 Decay below the 150 Nd Neutron Separation Threshold

We introduce a new method for the study of fluctuations of partial transition widths based on nuclear resonance fluorescence experiments with quasimonochromatic linearly polarized photon beams below particle separation thresholds. It is based on the average branching of decays of 𝐽=1 states of an even-even nucleus to the 2$^{+}_{1}$ state in comparison to the ground state. Between 5 and 7 MeV, a constant average branching ratio for 𝛾 decays from 1 − states of 0.490(16) is observed for the nuclide 150 Nd. Assuming 𝜒 2 -distributed partial transition widths, this average branching ratio is related to a degree of freedom of 𝜈 = 1.93⁢(12), rejecting the validity of the Porter-Thomas distribution, requiring 𝜈 = 1. The observed deviation can be explained by nonstatistical effects in the 𝛾-decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.

150 ≤ A ≤ 189↗
DOE OSTI2025

Spontaneous magnon decays from nonrelativistic time-reversal symmetry breaking in altermagnets

Quasiparticles are central to condensed matter physics, but their stability can be undermined by quantum many-body interactions. Magnons, i.e., quasiparticles in quantum magnets, are particularly intriguing because their properties are governed by both real and spin space. While crystal symmetries may be low, spin interactions often remain approximately isotropic, limiting spontaneous magnon decay. Textbook wisdom holds that collinear Heisenberg magnets follow a dichotomy: ferromagnets host stable magnons, while antiferromagnetic magnons may decay depending on dispersion curvature. Up to now, relativistic spin-orbit coupling and noncollinear order that connect spin space to real space were shown to introduce more complex magnon instability mechanisms. Here, we show that even in nonrelativistic isotropic collinear systems, this conventional dichotomy is disrupted in altermagnets. Altermagnets, a newly identified class of collinear magnets, exhibit compensated spin order with nonrelativistic time-reversal symmetry breaking and even-parity band splitting. Using kinematic analysis, nonlinear spin-wave theory, and quantum simulations, we reveal that even weak band splitting opens a decay phase space, driving quasiparticle breakdown. Additionally, 𝑑-wave altermagnets form a rare “island of stability” at the Brillouin-zone center. Furthermore, our findings establish a quasiparticle stability trichotomy in collinear Heisenberg magnets and position altermagnets as a promising platform for unconventional spin dynamics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Quantum Hamiltonian for the surface charge density on a ring torus and radiative decay of plasmons

Photon scattering and the ensuing excitation of surface plasmons in single rings, single composite rings, and many-ring systems was recently shown to provide dispersion and field distributions [K. V. Garapati et al., J. Phys. Commun. 2, 015031 (2018)] of potential for specific applications in particle and molecular trapping [R. Alaee et al., Appl. Phys. Lett. 109, 141102 (2016); M. Salhi et al., Phys. Rev. A 92, 033416 (2015)], in addition to metamaterials and sensing. Furthermore, following photon or electron interactions with metallic nanorings, both radiative and nonradiative decay channels are important in the consideration of the nanoparticle as a photon or phonon source, and in related applications. In this work, we quantize the electronic normal modes of the ring torus and obtain the radiative decay of plasmons. Due to a geometry-related complexity, we employ a perturbation approach to obtain analytical expressions for the radiative decay channel for a vacuum bounded single solid nanoring. In quantizing the fields, the frequency spectrum of the charge density normal modes of the nanoring is obtained and shown to agree with the exact quasistatic plasmon dispersion relations. Higher-order corrections beyond the presented zero- and first-order calculations may be obtained following the presented results. The results are of potential interest in quantum sensing such as entangling photons and plasmons, or plasmons and trapped molecules.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Majorana parameters of the interacting boson model of nuclear structure and their implication for 0 ν β β decay

Here, the well-known spherical-deformed-transitional nucleus and potential 0$\textit{νββ}$ emitter 150 Nd and its daughter 150 Sm were investigated in nuclear resonance fluorescence experiments using quasimonoenergetic, linearly polarized γ-ray beams. For both nuclei transitions from the 1 + scissors mode to the $0^+_2$ and $2^+_2$ states were observed for the first time and their respective $\textit{M}$ 1 transition strengths were determined. Through a systematic investigation, a sensitivity of these transition strengths to the three Majorana parameters of the interacting boson model-2 (IBM-2) was established. In combination with the novel experimental data, this poses strong constraints to the Majorana parameters in improved IBM-2 representations of both nuclei. A subsequent recalculation of the nuclear matrix elements (NMEs) for the 150 Nd → 150 Sm 0$\textit{νββ}$ decay in the IBM-2 with these improved representations results in $M^{(0νββ)}_{\text{IBM-2}}[0^+_1]$ = 3.35 for the NME for 0$\textit{νββ}$ decay into the ground state of 150 Sm and $M^{(0νββ)}_{\text{IBM-2}}[0^+_2]$ = 1.30 for 0$\textit{νββ}$ decay to its $0^+_2$ state.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Search for neutrinoless β-plus-EC decay of 120 Te with CUORE

The Cryogenic Underground Observatory for Rare Events (CUORE) is a large-scale cryogenic experiment searching for neutrinoless double-beta decay (0νββ) in 130 Te. The CUORE detector is made of natural tellurium, providing the possibility of rare event searches on isotopes other than 130 Te. In this work we describe a search for neutrinoless positron-emitting electron capture (β + EC ) decay in 120 Te with a total TeO 2 exposure of 355.7 kg yr, corresponding to 0.2405 kg yr of 120 Te. Albeit 0νββ with two final-state electrons represents the most promising channel, the emission of a positron and two 511-keV γ 's make 0νβ + EC decay signature extremely clear. To fully exploit the potential offered by the detector modularity we include events with different topology and perform a simultaneous fit of five selected signal signatures. Using blinded data we extract a median exclusion sensitivity of 3.4 × 10 22 yr at 90% credibility interval (C.I.). After unblinding we find no evidence of 0νβ + EC signal and set a 90% C.I. Bayesian lower limit of 2.9 × 10 22 yr on 120 Te half-life. This result improves by an order of magnitude the existing limit from the combined analysis of CUORE-0 and Cuoricino.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

Search for an s -wave resonance in Li 7 just above the proton-decay threshold

Near-threshold resonances play an important role in nucleosynthesis and applied nuclear science. The study of nuclei removed from stability has greatly extended the list of resonances close to decay thresholds. The no core shell model with continuum (NCSMC) recently predicted an s-wave resonance just above the proton-decay threshold of 7 Li at an excitation energy of 10.2 MeV. This potential case of a near-threshold resonance is dependent on the quantum mechanics of the p + 6 He fragments extended into the continuum. Further, the 6 He(d,n) 7 Li* reaction was employed in an attempt to populate this resonance and search for its proton decay via the invariant-mass method. No evidence of this resonance was found. However, the data collected in this search led to better constraints on the energy and width of the isobaric analog state (IAS) with (J π ,T) = (3/2 - , 3/2) and revealed a new weak resonance just above the IAS in energy, predicted by the NCSMC as a (J π , T ) = (3/2 – , 1/2) state and potentially a part of the antianalog structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Search for long-lived particles decaying to jets with displaced vertices in proton-proton collisions at √ s = 13 TeV

A search is presented for long-lived particles produced in pairs in proton-proton collisions at the LHC operating at a center-of-mass energy of 13 TeV . The data were collected with the CMS detector during the period from 2015 through 2018, and correspond to a total integrated luminosity of 140 fb –1 . This search targets pairs of long-lived particles with mean proper decay lengths between 0.1 and 100 mm , each of which decays into at least two quarks that hadronize to jets, resulting in a final state with two displaced vertices. No significant excess of events with two displaced vertices is observed. In the context of R-parity violating supersymmetry models, the pair production of long-lived neutralinos, gluinos, and top squarks is excluded at 95% confidence level for cross sections larger than 0.08 fb, masses between 800 and 3000 GeV, and mean proper decay lengths between 1 and 25 mm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Thermal false vacuum decay around black holes

In flat space and at finite temperature, there are two regimes of false vacuum decay in quantum field theory. At low temperature, the decay proceeds through thermally-assisted tunneling described by periodic Euclidean solutions—bounces—with nontrivial time dependence. On the other hand, at high temperatures the bounces are time independent and describe thermal jumps of the field over the potential barrier. Here, we argue that only solutions of the second type are relevant for false vacuum decay catalyzed by a black hole in equilibrium with thermal bath. The argument applies to a wide class of spherical black holes, including d-dimensional anti–de Sitter/de Sitter Schwarzschild black holes and Reissner-Nordström black holes sufficiently far from criticality. It does not rely on the thin-wall approximation and applies to multifield scalar theories.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Study of the lineshape of X ( 3872 ) using B decays to D 0 D ¯ * 0 K

We present a study of the X⁡(3872) lineshape in the decay B →X(3872)⁢K →D 0 $\overline{D}$ *0 ⁢K using a data sample of 772 ×10 6 B$\overline{B}$ pairs collected at the Y⁡(4⁢S) resonance with the Belle detector at the KEKB asymmetric-energy e +⁢ e - collider. The peak near the threshold in the D 0 $\overline{D}$ *0 invariant mass spectrum is fitted using a relativistic Breit-Wigner lineshape. We determine the mass and width parameters to be m BW =3873.7⁢1$^{+0.56}_{-0.50⁢}$(stat) ±0.13⁢(syst) MeV/c 2 and Γ BW =5.2$^{+2.2}_{-1.5}$⁢(stat) ±0.4⁢(syst) MeV, respectively. The branching fraction is found to be $\mathscr{B}$⁡(B + → X⁡(3872)⁢K + ) × $\mathscr{B}$⁡(X⁡(3872) → D 0 $\overline{D}$ *0 ) = (0.9⁢7$^{+0.21}_{-0.18}$⁢(stat) ± 0.10⁢(syst)) ×10 -4 . The signal from B 0 decays is observed for the first time with 5.2σ significance, and the ratio of branching fractions between charged and neutral B decays is measured to be $\mathscr{B}$(B 0 → X⁡(3872)⁢K 0 )/$\mathscr{B}$⁡(B + →X⁡(3872)⁢K + ) =1.34$^{+0.47}_{-0.40}$⁢(stat) $^{+0.10}_{-0.12}$⁢(syst). The peak is also studied using a Flatté lineshape. We determine the lower limit on the D 0 $\overline{D}$ * coupling constant g to be 0.075 at 95% credibility in the parameter region where the ratio of g to the mass difference from the D 0 $\overline{D}$ *0 threshold is equal to -15.11 GeV -1 , as measured by LHCb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Amplitude analysis of B 0 → D ¯ 0 D s + π - and B + → D - D s + π + decays

Resonant contributions in B 0 → D ¯ 0 D s + π - and B + → D - D s + π + decays are determined with an amplitude analysis, which is performed both separately and simultaneously, where in the latter case isospin symmetry between the decays is assumed. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV. The full data sample corresponds to an integrated luminosity of 9 fb -1 . A doubly charged spin-0 open-charm tetraquark candidate together with a neutral partner, both with masses near 2.9 GeV, are observed in the $D_sπ$ decay channel.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Anomaly detection search for new resonances decaying into a Higgs boson and a generic new particle $X$ in hadronic final states using $\sqrt{s}$ = 13 TeV $pp$ collisions with the ATLAS detector

A search is presented for a heavy resonance $Y$ decaying into a Standard Model Higgs boson $H$ and a new particle $X$ in a fully hadronic final state. The full Large Hadron Collider run 2 dataset of proton-proton collisions at $\sqrt{s}$ = 13 TeV collected by the ATLAS detector from 2015 to 2018 is used and corresponds to an integrated luminosity of 139 fb –1 . The search targets the high $Y$-mass region, where the $H$ and $X$ have a significant Lorentz boost in the laboratory frame. A novel application of anomaly detection is used to define a general signal region, where events are selected solely because of their incompatibility with a learned background-only model. It is constructed using a jet-level tagger for signal-model-independent selection of the boosted $X$ particle, representing the first application of fully unsupervised machine learning to an ATLAS analysis. Two additional signal regions are implemented to target a benchmark $X$ decay into two quarks, covering topologies where the $X$ is reconstructed as either a single large-radius jet or two smallradius jets. The analysis selects Higgs boson decays into $b$$\overline{b}$, and a dedicated neural-network-based tagger provides sensitivity to the boosted heavy-flavor topology. No significant excess of data over the expected background is observed, and the results are presented as upper limits on the production cross section $σ$ ($pp$ → $Y$ → $XH$ → $q$$\overline{q}$$b$$\overline{b}$) for signals with $m_Y$ between 1.5 and 6 TeV and $m_X$ between 65 and 3000 GeV

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Integrated and differential fiducial cross-section measurements for the vector boson fusion production of the Higgs boson in the $H → WW^* → evμv$ decay channel at 13 TeV with the ATLAS detector

The vector-boson production cross-section for the Higgs boson decay in the H→WW*→eνμν channel is measured as a function of kinematic observables sensitive to the Higgs boson production and decay properties as well as integrated in a fiducial phase space. The analysis is performed using the proton-proton collision data collected by the ATLAS detector in Run 2 of the LHC at $\sqrt{s}$=13 TeV center-of-mass energy corresponding to an integrated luminosity of 139 fb -1 . The different flavor final state is studied by selecting an electron and a muon originating from a pair of W bosons and compatible with the Higgs boson decay. The data are corrected for the effects of detector inefficiency and resolution, and the measurements are compared with different state-of-the-art theoretical predictions. The differential cross-sections are used to constrain anomalous interactions described by dimension-six operators in an Effective Field Theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for neutrino lines from dark matter annihilation and decay with IceCube

Dark matter particles in the Galactic Center and halo can annihilate or decay into a pair of neutrinos producing a monochromatic flux of neutrinos. The spectral feature of this signal is unique and it is not expected from any astrophysical production mechanism. Its observation would constitute a dark matter smoking gun signal. Here we performed the first dedicated search with a neutrino telescope for such signal, by looking at both the angular and energy information of the neutrino events. To this end, a total of five years of IceCube’s DeepCore data has been used to test dark matter masses ranging from 10 GeV to 40 TeV. No significant neutrino excess was found and upper limits on the annihilation cross section, as well as lower limits on the dark matter lifetime, were set. The limits reached are of the order of 10 -24 cm 3 /s for an annihilation and up to 10 27 s for decaying dark matter. Using the same data sample we also derive limits for dark matter annihilation or decay into a pair of Standard Model charged particles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for the semileptonic decays Ξ c 0 → Ξ 0 ℓ + ℓ − at Belle

Using the full data sample of 980 fb − 1 collected with the Belle detector at the KEKB asymmetric energy electron-positron collider, we report the results of the first search for the rare semileptonic decays Ξ c 0 → Ξ 0 ℓ + ℓ − ( ℓ = e or μ ). No significant signals are observed in the Ξ 0 ℓ + ℓ − invariant-mass distributions. Taking the decay Ξ c 0 → Ξ − π + as the normalization mode, we report 90% credibility upper limits on the branching fraction ratios B ( Ξ c 0 → Ξ 0 e + e − ) / B ( Ξ c 0 → Ξ − π + ) < 6.7 × 10 − 3 and B ( Ξ c 0 → Ξ 0 μ + μ − ) / B ( Ξ c 0 → Ξ − π + ) < 4.3 × 10 − 3 based on the phase-space assumption for signal decays. The 90% credibility upper limits on the absolute branching fractions of B ( Ξ c 0 → Ξ 0 e + e − ) and B ( Ξ c 0 → Ξ 0 μ + μ − ) are found to be 9.9 × 10 − 5 and 6.5 × 10 − 5 , respectively. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Prospects for exotic h → 4 τ decays in single and di-Higgs boson production at the LHC and future hadron colliders

We study the prospects for observing exotic decays of the Standard Model Higgs boson h into light beyond the Standard Model scalars a with mass m a ≲ m h / 2 in the single Higgs and Higgs pair production channels at the high luminosity run of the Large Hadron Collider (HL-LHC). Discovery prospects for single Higgs production in the gluon-gluon fusion and vector boson fusion modes with the Higgs boson decaying via the exotic mode h → a a → 4 τ are analyzed at the HL-LHC. The projected sensitivity for exotic Higgs decays in the nonresonant Higgs pair production channel p p → h h → ( h → b b ¯ ) ( h → a a → 4 τ ) → 2 b 4 τ at the HL-LHC and a future s = 100 TeV hadron collider (FCC-hh) are also estimated. Furthermore, we study HL-LHC’s potential reach for the Higgs-strahlung process in the 2 b 4 τ channel, taking into account the contamination from nonresonant Higgs pair production. Finally, the potential reach for resonant Higgs pair production in the 2 b 4 τ channel at the HL-LHC is also explored for several choices of { m H , m a } . Our studies suggest that significant improvements over existing bounds are achievable in several production channels, motivating new dedicated searches for h → a a → 4 τ at the HL-LHC and future colliders. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Dark dimension and decaying dark matter gravitons

We explore the cosmology of the dark-dimension scenario taking into account perturbations in the linear regime. In the context of the dark-dimension scenario, a natural candidate for dark matter in our Universe is the excitations of a tower of massive spin-2 Kaluza-Klein (KK) gravitons. These dark gravitons are produced in the early Universe and decay to lighter KK gravitons during the course of cosmological evolution. The decay causes the average dark matter mass to decrease as the Universe evolves. In addition, the kinetic energy liberated in each decay leads to a kick velocity for the dark matter particles, leading to a suppression of structure formation. Using current cosmic microwave background (), baryon acoustic oscillation, and cosmic shear (KiDS-1000) data, we put a bound on the dark matter kick velocity today v today ≤ 2.2 × 10 − 4 c at 95% CL. This leads to rather specific regions of parameter space for the dark-dimension scenario. The combination of the experimental bounds from cosmology, astrophysics, and table-top experiments leads to the range l 5 ∼ 1 – 10 μ m for the size of the dark dimension. The dark-dimension scenario is found to be remarkably consistent with current observations and provides signatures that are within reach of near-future experiments. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Constituent model of light hybrid meson decays

A model of light hybrid mesons and their strong decays is developed. The model employs a gluonic quasiparticle to describe low energy gluodynamics and uses the QCD Hamiltonian in Coulomb gauge to guide the construction of states and decay amplitudes. We compute the partial widths of the twelve low lying isovector and vector hybrids. Implications of these results on hybrid searches are also made, with the chief conclusions being that direct observation of the vector states will be difficult, that a hybrid π ( 1800 ) has distinctive decay characteristics, a narrow η ( 1900 ) hybrid should exist, an η 1 ( 1750 ) should be sought, and that the exotic nature of J P C = 2 − + hybrid mesons should be discernible with sufficient data. We argue that the isovector π 2 hybrid has been discovered, giving a total of four possible hybrid mesons, π 1 ( 1600 ) , η 1 ( 1855 ) , π ( 1800 ) , and π 2 ( 2360 ) , which appear to be filling out the low lying hybrid supermultiplet in the expected fashion. Published by the American Physical Society 2024

Astronomy & Astrophysics↗