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At least 523 records · Page 29

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DOE OSTI2020

On the Pressure Generated by Thermite Reactions Using Stress-Altered Aluminum Particles

Here we examine pressure build-up and decay in thermites upon impact ignition and interprets reactivity based on the holistic pressure history. The thermite is a mixture of aluminum (Al) combined with bismuth trioxide (Bi 2 O 3 ) powder. Four different Al particles sizes were examined that ranged from 100 nm to 18.5 μm mean diameter and for each size, two different Al powder treatments were examined: stress-altered compared to untreated, as-received Al powder. Stress-altered Al powders have been shown to be more reactive, such that the stress-altered Al powder thermites offer a metric for analyzing thermite reactivity in terms of pressure development compared to untreated Al powder. In a binary thermite system, multiple phase changes and interface chemistry influence the transient pressure response during reaction. Results reveal three key pressure metrics that need consideration specifically for thermite combustion: (1) delay time to peak pressure, (2) peak pressure, and (3) decay after peak pressure. Our experiments show that a lower peak pressure corresponds with higher thermite reactivity because aluminum consumption of oxygen generated by decomposing solid oxidizer reduces the peak pressure. Faster rates of reaction consume oxygen at higher rates such that pressure development becomes more limited than less reactive thermites and the result is a lower peak pressure. This conclusion is opposite of traditional studies using metal fuels with a gaseous environment that typically show higher peak pressures correspond with greater reactivity.

42 ENGINEERING↗

DOE OSTI2020

Generic Construction of the Standard Model Gauge Group and Matter Representations in F-theory

In this work, we describe general classes of 6D and 4D F-theory models with gauge group (SU(3)×SU(2)×U(1))/Z 6 . For 6D F-theory models with no tensor multiplets, we prove that this set of constructions gives all possible consistent supergravity theories with this gauge group and the corresponding generic matter representations, which include those of the MSSM. We expect, though do not prove, that these models are similarly generic for 6D theories with tensor multiplets and for 4D N=1 supergravity theories. Finally, the models in the largest class of these constructions come from deforming an underlying geometry with SU(4)×SU(3)×SU(2), corresponding to Higgsing on three bifundamental fields.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

On the BPS Sector in AdS 3 /CFT 2 Holography

Abstract The BPS sector in duality has been fertile ground for the exploration of gauge/gravity duality, from the match between black hole entropy and the CFT elliptic genus to the construction of large families of geometrical microstates and the identification of the corresponding states in the CFT. Worldsheet methods provide a tool to further explore the relation between string theory in the bulk and corresponding CFT quantities. We show how to match individual BPS strings to their counterparts in the symmetric product orbifold CFT. In the process, we find an exact match between known constructions of microstate geometries and condensates of BPS supergraviton strings, and discuss their role in the broader collection of BPS states. In particular, we explore how microstate geometries develop singularities; and how string theory resolves these singularities through the appearance of “tensionless” string dynamics, which is the continuation of structures found in the weak‐coupling CFT into the strongly coupled regime described by string theory in the bulk. We argue that such “tensionless” strings are responsible for black hole microstructure in the bulk description.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

New magnetic symmetries in (d + 2)-dimensional QED

Previous analyses of asymptotic symmetries in QED have shown that the subleading soft photon theorem implies a Ward identity corresponding to a charge generating divergent large gauge transformations on the asymptotic states at null infinity. In this work, we demonstrate that the subleading soft photon theorem is equivalent to a more general Ward identity. The charge corresponding to this Ward identity can be decomposed into an electric piece and a magnetic piece. The electric piece generates the Ward identity that was previously studied, but the magnetic piece is novel, and implies the existence of an additional asymptotic “magnetic” symmetry in QED.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Evidence for Higgs boson decay to a pair of muons

Evidence for Higgs boson decay to a pair of muons is presented. This result combines searches in four exclusive categories targeting the production of the Higgs boson via gluon fusion, via vector boson fusion, in association with a vector boson, and in association with a top quark-antiquark pair. The analysis is performed using proton-proton collision data at $ \sqrt{s} $ = 13 TeV, corresponding to an integrated luminosity of 137 fb$^{−1}$, recorded by the CMS experiment at the CERN LHC. An excess of events over the back- ground expectation is observed in data with a significance of 3.0 standard deviations, where the expectation for the standard model (SM) Higgs boson with mass of 125.38 GeV is 2.5. The combination of this result with that from data recorded at $ \sqrt{s} $ = 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7 fb$^{−1}$, respectively, increases both the expected and observed significances by 1%. The measured signal strength, relative to the SM prediction, is $ {1.19}_{-0.39}^{+0.40}{\left(\mathrm{stat}\right)}_{-0.14}^{+0.15}\left(\mathrm{syst}\right) $. This result constitutes the first evidence for the decay of the Higgs boson to second generation fermions and is the most precise measurement of the Higgs boson coupling to muons reported to date.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Measurement of the W boson mass

The W boson mass is measured using proton-proton collision data at $\sqrt{s}$ = 13 TeV corresponding to an integrated luminosity of 1.7 fb -1 recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon $q/ρ_T$ distribution of a sample of W →$μv$ decays and the $\phi^*$ distribution of a sample of Z → $μμ$ decays the W boson mass is determined to be $m_w$ =80354±23 stat ±10 exp ±17 theory ±9 PDF MeV, where uncertainties correspond to contributions from statistical, experimental systematic, theoretical and parton distribution function sources. This is an average of results based on three recent global parton distribution function sets. The measurement agrees well with the prediction of the global electroweak fit and with previous measurements.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2024

Null Raychaudhuri: canonical structure and the dressing time

Abstract We initiate a study of gravity focusing on generic null hypersurfaces, non-perturbatively in the Newton coupling. We present an off-shell account of the extended phase space of the theory, which includes the expected spin-2 data as well as spin-0, spin-1 and arbitrary matter degrees of freedom. We construct the charges and the corresponding kinematic Poisson brackets, employing a Beltrami parameterization of the spin-2 modes. We explicitly show that the constraint algebra closes, the details of which depend on the non-perturbative mixing between spin-0 and spin-2 modes. Finally we show that the spin zero sector encodes a notion of a clock, called dressing time, which is dynamical and conjugate to the constraint. It is well-known that the null Raychaudhuri equation describes how the geometric data of a null hypersurface evolve in null time in response to gravitational radiation and external matter. Our analysis leads to three complementary viewpoints on this equation. First, it can be understood as a Carrollian stress tensor conservation equation. Second, we construct spin-0, spin-2 and matter stress tensors that act as generators of null time reparametrizations for each sector. This leads to the perspective that the null Raychaudhuri equation can be understood as imposing that the sum of CFT-like stress tensors vanishes. Third, we solve the Raychaudhuri constraint non-perturbatively. The solution relates the dressing time to the spin-2 and matter boost charge operators. Finally we establish that the corner charge corresponding to the boost operator in the dressing time frame is monotonic. These results show that the notion of an observer can be thought of as emerging from the gravitational degrees of freedom themselves. We briefly mention that the construction offers new insights into focusing conjectures.

Physics↗

DOE OSTI2026

Measurements of the inclusive W and Z boson production cross sections and their ratios in proton-proton collisions at $\sqrt{s}=13.6$ TeV

Measurements are presented of the W and Z boson production cross sections in proton-proton collisions at a center-of-mass energy of 13.6 TeV. Data collected in 2022 and corresponding to an integrated luminosity of 5.01 fb −1 with one or two identified muons in the final state are analyzed. The results for the products of total inclusive cross sections and branching fractions for muonic decays of W and Z bosons are 11.93 ± 0.08 (syst) ± 0.17 (lumi) $^{+0.07}_{−0.07}$ (acceptance) nb for W + boson production, 8.86 ± 0.06 (syst) ± 0.12 (lumi) $^{+0.05}_{−0.06}$ (acceptance) nb for W − boson production, and 2.021 ± 0.009 (syst) ± 0.028 (lumi) $^{+0.011}_{−0.013}$ (acceptance) nb for the Z boson production in the dimuon mass range of 60–120 GeV, all with negligible statistical uncertainties. Furthermore, the corresponding fiducial cross sections, as well as cross section ratios for both fiducial and total phase space, are provided. The ratios include charge-separated results for W boson production (W + and W − ) and the sum of the two contributions (W ± ), each relative to the measured Z boson production cross section. Additionally, the ratio of the measured cross sections for W + and W − boson production is reported. All measurements are in agreement with theoretical predictions, calculated at next-to-next-to-leading order accuracy in quantum chromodynamics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Stringy canonical forms

Canonical forms of positive geometries play an important role in revealing hidden structures of scattering amplitudes, from amplituhedra to associahedra. In this paper, we introduce “stringy canonical forms”, which provide a natural definition and extension of canonical forms for general polytopes, deformed by a parameter α'. They are defined by real or complex integrals regulated with polynomials with exponents, and are meromorphic functions of the exponents, sharing various properties of string amplitudes. As α'→ 0, they reduce to the usual canonical form of a polytope given by the Minkowski sum of the Newton polytopes of the regulating polynomials, or equivalently the volume of the dual of this polytope, naturally determined by tropical functions. At finite α', they have simple poles corresponding to the facets of the polytope, with the residue on the pole given by the stringy canonical form of the facet. There is the remarkable connection between the α'→ 0 limit of tree-level string amplitudes, and scattering equations that appear when studying the α'→ ∞ limit. We show that there is a simple conceptual understanding of this phenomenon for any stringy canonical form: the saddle-point equations provide a diffeomorphism from the integration domain to the interior of the polytope, and thus the canonical form can be obtained as a pushforward via summing over saddle points. When the stringy canonical form is applied to the ABHY associahedron in kinematic space, it produces the usual Koba-Nielsen string integral, giving a direct path from particle to string amplitudes without an a priori reference to the string worldsheet. We also discuss a number of other examples, including stringy canonical forms for finite-type cluster algebras (with type A corresponding to usual string amplitudes), and other natural integrals over the positive Grassmannian.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Combined analysis of Belle and Belle II data to determine the CKM angle φ 3 using B + → D($ {K}_S^0 $h + h – )h + decays

We present a measurement of the Cabibbo-Kobayashi-Maskawa unitarity triangle angle φ 3 (also known as γ) using a model-independent Dalitz plot analysis of B + → D($ {K}_S^0 $h + h – )h + , where D is either a D o or D o ¯ meson and h is either a π or K. This is the first measurement that simultaneously uses Belle and Belle II data, combining samples corresponding to integrated luminosities of 711 fb –1 and 128 fb –1 , respectively. All data were accumulated from energy-asymmetric e + e – collisions at a centre-of-mass energy corresponding to the mass of the Υ(4S) resonance. We measure φ 3 = (78.4 ± 11.4 ± 0.5 ± 1.0)°, where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is from the uncertainties on external measurements of the D-decay strong-phase parameters.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2025

Search for long-lived heavy neutral leptons in proton-proton collision events with a lepton-jet pair associated with a secondary vertex at $\sqrt{s}$ = 13 TeV

A search for long-lived heavy neutral leptons (HNLs) using proton-proton collision data corresponding to an integrated luminosity of 138 fb −1 collected at $\sqrt{s}$ = 13 TeV with the CMS detector at the CERN LHC is presented. Events are selected with a charged lepton originating from the primary vertex associated with the proton-proton interaction, as well as a second charged lepton and a hadronic jet associated with a secondary vertex that corresponds to the semileptonic decay of a long-lived HNL. No excess of events above the standard model expectation is observed. Exclusion limits at 95% confidence level are evaluated for HNLs that mix with electron and/or muon neutrinos. Limits are presented in the mass range of 1–16.5 GeV, with excluded square mixing parameter values reaching as low as 2 × 10 −7 . For masses above 11 GeV, the presented limits exceed all previous results in the semileptonic decay channel, and for some of the considered scenarios are the strongest to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2025

Search for same-charge top-quark pair production in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search for the production of top-quark pairs with the same electric charge ($tt$ or $\overline{tt}$) is presented. The analysis uses proton-proton collision data at $\sqrt{s}$ = 13 TeV, recorded by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb −1 . Events with two same-charge leptons and at least two b-tagged jets are selected. Neural networks are employed to define two selections sensitive to additional couplings beyond the Standard Model that would enhance the production rate of same-sign top-quark pairs. No significant signal is observed, leading to an upper limit on the total production cross-section of same-sign top-quark pairs of 1.6 fb at 95% confidence level. Corresponding limits on the three Wilson coefficients associated with the $\mathcal{O}^{(1)}_{tu}$, $\mathcal{O}^{(1)}_{Qu}$, and $\mathcal{O}^{(8)}_{Qu}$ operators in the Standard Model Effective Field Theory framework are derived.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2026

Collins-type fragmentation energy correlator in semi-inclusive deep inelastic lepton-hadron scattering

We initiate a systematic study of fragmentation energy correlators (FECs), which generalize traditional fragmentation functions and encode non-perturbative information about transverse dynamics in parton fragmentation processes. We define boost-invariant, non-perturbative FECs and derive a corresponding collinear factorization formula. A spin decomposition of the FECs is carried out, analogous to that of transverse-momentum-dependent fragmentation functions. In this work we focus particularly on the Collins-type quark FEC, which is sensitive to chiral symmetry breaking and characterizes the azimuthal asymmetry in the fragmentation of a transversely polarized quark. We perform a next-to-leading-order calculation of the corresponding hard coefficient in semi-inclusive deep-inelastic scattering for the quark non-singlet component, thereby validating the consistency of our theoretical framework.

Deep Inelastic Scattering or Small-x Physics↗

DOE OSTI2020

A search for the standard model Higgs boson decaying to charm quarks

A direct search for the standard model Higgs boson, H, produced in association with a vector boson, V (W or Z), and decaying to a charm quark pair is presented. The search uses a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb$^{−1}$, collected by the CMS experiment at the LHC in 2016, at a centre-of-mass energy of 13 TeV. The search is carried out in mutually exclusive channels targeting specific decays of the vector bosons: W → ℓν, Z → ℓℓ, and Z → νν, where ℓ is an electron or a muon. To fully exploit the topology of the H boson decay, two strategies are followed. In the first one, targeting lower vector boson transverse momentum, the H boson candidate is reconstructed via two resolved jets arising from the two charm quarks from the H boson decay. A second strategy identifies the case where the two charm quark jets from the H boson decay merge to form a single jet, which generally only occurs when the vector boson has higher transverse momentum. Both strategies make use of novel methods for charm jet identification, while jet substructure techniques are also exploited to suppress the background in the merged-jet topology. The two analyses are combined to yield a 95% confidence level observed (expected) upper limit on the cross section $ \sigma \left(\mathrm{VH}\right)\mathrm{\mathcal{B}}\left(\mathrm{H}\to \mathrm{c}\overline{\mathrm{c}}\right) $ of 4.5 $ \left({2.4}_{-0.7}^{+1.0}\right) $ pb, corresponding to 70 (37) times the standard model prediction.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Search for nonresonant Higgs boson pair production in final states with two bottom quarks and two photons in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

A search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two photons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of $ \sqrt{s} $ = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb$^{−1}$. No significant deviation from the background-only hypothesis is observed. An upper limit at 95% confidence level is set on the product of the Higgs boson pair production cross section and branching fraction into $ \gamma \gamma \mathrm{b}\overline{\mathrm{b}} $. The observed (expected) upper limit is determined to be 0.67 (0.45) fb, which corresponds to 7.7 (5.2) times the standard model prediction. This search has the highest sensitivity to Higgs boson pair production to date. Assuming all other Higgs boson couplings are equal to their values in the standard model, the observed coupling modifiers of the trilinear Higgs boson self-coupling κ$_{λ}$ and the coupling between a pair of Higgs bosons and a pair of vector bosons c$_{2V}$ are constrained within the ranges −3.3 < κ$_{λ}$< 8.5 and −1.3 < c$_{2V}$< 3.5 at 95% confidence level. Constraints on κ$_{λ}$ are also set by combining this analysis with a search for single Higgs bosons decaying to two photons, produced in association with top quark-antiquark pairs, and by performing a simultaneous fit of κ$_{λ}$ and the top quark Yukawa coupling modifier κ$_{t}$.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Search for long-lived particles produced in association with a Z boson in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016–2018, corresponding to an integrated luminosity of 117 fb -1 . The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H → SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10–100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass (≈ 15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions B(H → SS) < 20% for proper decay lengths of 10–50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Prompt and non-prompt J/ψ production cross sections at midrapidity in proton-proton collisions at $ \sqrt{\mathrm{s}} $ = 5.02 and 13 TeV

The production of J /ψ is measured at midrapidity ( |y| < 0 . 9) in proton-proton collisions at $ \sqrt{s} $ = 5 . 02 and 13 TeV, through the dielectron decay channel, using the ALICE detector at the Large Hadron Collider. The data sets used for the analyses correspond to integrated luminosities of $ \mathcal{L} $ int = 19.4 ± 0.4 nb - 1 and $ \mathcal{L} $ int = 32.2 ± 0.5 nb - 1 at $ \sqrt{s} $ = 5 . 02 and 13 TeV, respectively. The fraction of non-prompt J /ψ mesons, i.e. those originating from the decay of beauty hadrons, is measured down to a transverse momentum p T = 2 GeV /c (1 GeV /c ) at $ \sqrt{s} $ = 5 . 02 TeV (13 TeV). The p T and rapidity ( y ) differential cross sections, as well as the corresponding values integrated over p T and y , are carried out separately for prompt and non-prompt J /ψ mesons. The results are compared with measurements from other experiments and theoretical calculations based on quantum chromodynamics (QCD). The shapes of the p T and y distributions of beauty quarks predicted by state-of-the-art perturbative QCD models are used to extrapolate an estimate of the $ \mathrm{b}\overline{\mathrm{b}} $ pair cross section at midrapidity and in the total phase space. The total $ \mathrm{b}\overline{\mathrm{b}} $ cross sections are found to be $ {\sigma}_{\mathrm{b}\overline{\mathrm{b}}} $ = 541 ± 45 (stat . ) ± 69 $ {\left(\mathrm{syst}.\right)}_{-12}^{+10} $ (extr . ) μ b and $ {\sigma}_{\mathrm{b}\overline{\mathrm{b}}} $ = 218 ± 37 (stat . ) ± 31 $ {\left(\mathrm{syst}.\right)}_{-9.1}^{+8.2} $ (extr . ) μ b at $ \sqrt{s} $ = 13 and 5.02 TeV, respectively. The value obtained from the combination of ALICE and LHCb measurements in pp collisions at $ \sqrt{s} $ = 13 TeV is also provided.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Scattering in black hole backgrounds and higher-spin amplitudes. Part I

The scattering of massless waves of helicity |$h$| = $0$, $\frac{1}{2}$, $1$ in Schwarzschild and Kerr backgrounds is revisited in the long-wavelength regime. Using a novel description of such backgrounds in terms of gravitating massive particles, we compute classical wave scattering in terms of 2 → 2 QFT amplitudes in flat space, to all orders in spin. The results are Newman-Penrose amplitudes which are in direct correspondence with solutions of the Regge-Wheeler/Teukolsky equation. By introducing a precise prescription for the point-particle limit, in Part I of this work we show how both agree for $h$ = 0 at finite values of the scattering angle and arbitrary spin orientation. Associated classical observables such as the scattering cross sections, wave polarizations and time delay are studied at all orders in spin. The effect of the spin of the black hole on the polarization and helicity of the waves is found in agreement with previous analysis at linear order in spin. In the particular limit of small scattering angle, we argue that wave scattering admits a universal, point-particle description determined by the eikonal approximation. We show how our results recover the scattering eikonal phase with spin up to second post-Minkowskian order, and match it to the effective action of null geodesics in a Kerr background. Using this correspondence we derive classical observables such as polar and equatorial scattering angles. This study serves as a preceding analysis to Part II, where the Gravitational Wave ($h$ = 2) case will be studied in detail.

79 ASTRONOMY AND ASTROPHYSICS↗