Recent ucsc_physics items

Overview of the Theory of Extremely Correlated Fermi Liquids

Fri, 12 Jun 2026 00:00:00 +0000

The Extremely Correlated Fermi Liquids (ECFL) theory is reviewed as a framework for understanding the t-J model in metallic systems close to the Mott insulating limit. This overview presents the underlying ideas and the resulting equations in a form accessible to nonexperts. We compare theoretical results with all available resistivity data for single-layer High-Tc systems, and with some spectral data. The highlighted results include a density dependent quasilinear T-dependence in resistivity, an unusually small quasiparticle weight, and distinct low-temperature emergent scales that dominate transport, thermodynamics and spectral properties of single-layer High Tc systems. Suggestions are made for further experiments to probe the physics of these challenging quantum many-body systems.

Ground-state Entropy of the Ising model on a Frustrated lattice

Fri, 12 Jun 2026 00:00:00 +0000

We report the ground-state entropy of a 2-d Ising model on the Shastry-Sutherland lattice. We also study a generalization of this model, where a constraint on the zero temperature allowed configurations is removed continuously.

Search for long-lived particles using displaced vertices of oppositely charged leptons in 140 fb − 1 of pp collisions at s = 13 TeV with the ATLAS detector

Thu, 4 Jun 2026 00:00:00 +0000

A search is presented for long-lived particles decaying into an oppositely charged lepton pair, μ + μ − , e + e − , or e  ±  μ ∓, that form a vertex within the inner tracking system of the ATLAS detector at the Large Hadron Collider, displaced from the primary proton–proton interaction region. The analysis uses the 140 fb − 1 of Run-2 data collected at s = 13 TeV by the ATLAS experiment in 2015–2018. The results of the analysis are interpreted in the context of three benchmark models covering masses from 0.1 to 2.2 TeV and a range of mean proper lifetimes times the speed of light from 1 to 10 000 mm. The first model is a generic Z′ boson pair-produced by a new heavy scalar, with the Z′ decaying into lepton pairs. The remaining two models are R-parity violating supersymmetric models in which the lightest neutralino χ ˜ 1 0 decays into ℓ + ℓ ′ − ν ( ℓ , ℓ ′ = e , μ). The models differ by the mode of production of the χ ˜ 1 0 , which can be produced via the decay of pairs of gluinos...

Characterization of nuclear breakup as a function of hard-scattering kinematics using dijets measured by ATLAS in p+Pb collisions

Thu, 4 Jun 2026 00:00:00 +0000

This Letter analyzes the sensitivity of event geometry estimators to the initial-state kinematics of hard scattering in proton–lead collisions. This analysis uses dijets as a proxy for the parton–parton scattering configuration, correlating it with event geometry estimators, namely the energy deposited in the Zero-Degree Calorimeter and the transverse energy recorded in the Forward Calorimeter in the Pb-going direction. The analysis uses data recorded by the ATLAS detector at the Large Hadron Collider with a nucleon–nucleon center-of-mass energy of 8.16 TeV, corresponding to an integrated luminosity of 56 nb − 1 . The jets are measured within the pseudorapidity interval −2.8  <  η  <  4.5, where positive η values correspond to the direction of the proton beam. Results are presented as a function of the Bjorken-x of the parton originating from the proton, xp . Both event geometry estimators are found to be dependent on xp , with the energy deposited in the Zero-Degree Calorimeter...

Measurement of the Higgs boson production in association with top quarks in multilepton final states in pp collisions at s=13 TeV with the ATLAS detector

Thu, 4 Jun 2026 00:00:00 +0000

A measurement of the associated production of a top-quark pair with the Higgs boson (tt¯H$$ t\overline{t}H $$) in multilepton final states is presented. The analysis is based on a data sample of proton-proton collisions at s=13$$ \sqrt{s}=13 $$ TeV recorded with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 140 fb−1. Six final states defined by the number and flavour of reconstructed charged leptons are combined in a simultaneous likelihood fit to extract the tt¯H$$ t\overline{t}H $$ signal and constrain the most relevant backgrounds. The measured tt¯H$$ t\overline{t}H $$ cross-section normalised to Standard Model (SM) prediction is σtt¯H/σSM=0.63−0.19+0.20$$ {\sigma}_{t\overline{t}H}/{\sigma}^{\mathrm{SM}}=0.{63}_{-0.19}^{+0.20} $$. This result corresponds to an observed (expected) significance of 3.3σ (5.3σ). Additionally, two other fits are used to measure the tt¯H$$ t\overline{t}H $$ cross-section differentially in bins...

Measurement of differential t-channel single top (anti)quark production cross-sections at 13 TeV with the ATLAS detector

Thu, 4 Jun 2026 00:00:00 +0000

The production of single top quarks and top antiquarks via the t-channel exchange of a virtual W boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider. The full Run 2 data sample recorded with the ATLAS detector in the years 2015–2018 is used, corresponding to an integrated luminosity of 140 fb−1. The absolute and normalised production cross-sections are measured differentially as a function of the transverse momentum and absolute rapidity of the top quark and top antiquark. In addition, the ratio of top quark to top antiquark production cross-sections is measured. The measured distributions are compared with next-to-leading-order quantum chromodynamics predictions obtained with different combinations of matrix-element generators, parton-shower programs and proton parton distribution functions, as well as to next-to-next-to-leading-order calculations. Overall, good agreement is observed between the measurements and the...

Search for a resonance decaying into a scalar particle and a Higgs boson in the final state with two bottom quarks and two photons with 199 fb − 1 of data collected at s =13 and 13.6 TeV with the ATLAS detector

Thu, 4 Jun 2026 00:00:00 +0000

A search for the resonant production of a heavy scalar X decaying into a lighter scalar S and a Higgs boson, through the process X → S ( → b b ¯ ) H ( → γ γ ) , where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using integrated luminosities of 140 and 59 fb − 1 of proton–proton collision data at centre-of-mass energies of 13 and 13.6 TeV, respectively, recorded with the ATLAS detector at the LHC. The search is performed over the mass ranges of 170  ≤  mX  ≤  1000 GeV and 15  ≤  mS  ≤  500 GeV. No significant excess over the Standard Model background predictions is observed and limits at 95% confidence level are set on the product of cross section and branching fraction for the process X → S ( → b b ¯ ) H ( → γ γ ) at 13 TeV, ranging from 9 fb to 0.06 fb.

Measurement of the W-boson angular coefficients and transverse momentum in pp collisions at s=13 TeV with the ATLAS detector

Wed, 3 Jun 2026 00:00:00 +0000

The angular distributions of Drell–Yan lepton pairs provide sensitive probes of the underlying dynamics of quantum chromodynamics (QCD) effects in vector-boson production. This paper presents for the first time the measurement of the full set of angular coefficients together with the differential cross-section as a function of the transverse momentum of the W boson, in the full phase space of the decay leptons. The measurements are performed separately for the W-$$W^-$$ and W+$$W^+$$ channels. The analysis uses proton–proton collision data recorded by the ATLAS experiment at the Large Hadron Collider in 2017 and 2018, during special low-luminosity runs with a reduced number of interactions per bunch crossings (pile-up). The data correspond to an integrated luminosity of 338 pb-1$$^{-1}$$ at a centre-of-mass energy of s=13$$\sqrt{s} = 13$$ TeV. The low pile-up environment provides excellent experimental conditions for high-precision measurements of W-boson production....

Search for the Higgs boson decay to a Z boson and a photon in pp collisions at s = 13 TeV and 13.6 TeV with the ATLAS detector

Wed, 3 Jun 2026 00:00:00 +0000

A search for the Higgs boson decay to a Z boson and a photon in the ℓℓγ ( ℓ = e , μ ) final state is performed using pp collisions at s = 13.6 TeV recorded with the ATLAS detector at the Large Hadron Collider during 2022–2024, corresponding to an integrated luminosity of 165 fb − 1 . The signal yield, normalised to the Standard Model prediction, is measured to be μ = 0 . 9 − 0.6 + 0.7 , compatible with the expected value of μ = 1.0 ± 0.7 . This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations under the background-only hypothesis. This result is combined with that of a similar search performed with 140 fb − 1 of s = 13 TeV pp collisions to provide the best expected sensitivity to date to this rare decay, namely an observed (expected) signal strength of μ = 1 . 3 − 0.5 + 0.6 ( μ = 1 . 0 − 0.5 + 0.6 ), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model...

Search for signatures of electroweakinos with photons, jets, and large missing transverse momentum in s=13 TeV pp collisions with the ATLAS detector

Wed, 3 Jun 2026 00:00:00 +0000

A search for final states characterised by at least one isolated high transverse-momentum photon, jets and large missing transverse momentum is presented. Such a final state might occur in gauge-mediated supersymmetric models where a pair of binos and higgsinos mix to form neutralinos, one of which decays into a photon plus a gravitino while the other decays into a Higgs boson, a Z boson or a photon, plus a gravitino. The search is performed using the full Run-2 data sample of 140 fb−1 of s=13$$ \sqrt{s}=13 $$ TeV proton-proton collisions collected by the ATLAS detector at the Large Hadron Collider. No significant excess of events is observed above the Standard Model prediction and model-dependent exclusion limits at the 95% confidence level are set. These limits are interpreted in terms of the masses of gauginos, which are excluded up to 1.2 TeV depending on their branching ratios, and on their branching ratios as a function of their mass.

Measurement of the inclusive-isolated prompt-photon cross section in pp¯ collisions using the full CDF data set

Wed, 3 Jun 2026 00:00:00 +0000

A measurement of the inclusive production cross section of isolated prompt photons in proton-antiproton collisions at center-of-mass energy s=1.96 TeV is presented. The results are obtained using the full Run II data sample collected with the Collider Detector at the Fermilab Tevatron, which corresponds to an integrated luminosity of 9.5 fb-1. The cross section is measured as a function of photon transverse energy, ETγ, in the range 30

Electroweak diboson production in association with a high-mass dijet system in semileptonic final states from pp collisions at s=13 TeV with the ATLAS detector

Wed, 3 Jun 2026 00:00:00 +0000

This paper reports the observation of electroweak diboson (WW/WZ/ZZ) production in association with a high-mass dijet system, in which final states with one boson decaying leptonically and the other boson decaying hadronically are studied. The hadronically decaying W/Z boson is reconstructed as either two small-radius jets or one large-radius jet with jet substructure requirements. The data analyzed correspond to an integrated luminosity of 140fb-1$$140 \ \text {fb}^{-1}$$ of proton–proton collisions at a center-of-mass energy of s=13$$\sqrt{s}=13$$ TeV collected with the ATLAS detector during the 2015-2018 data taking at the Large Hadron Collider. The electroweak production of WW/WZ/ZZ in association with two jets is observed in a phase space dominated by vector-boson scattering with a significance of 7.4σ$$7.4\sigma $$ (expected 6.1σ$$6.1\sigma $$) and the signal strength is determined to be 1.28-0.21+0.23$$1.28^{+0.23}_{-0.21}$$. The corresponding production cross section in...

Precise measurement of the tt¯ production cross-section and lepton differential distributions in eμ dilepton events from s=13TeVpp collisions with the ATLAS detector

Wed, 3 Jun 2026 00:00:00 +0000

The inclusive top quark pair (tt¯$$t\bar{t}$$) cross-section σtt¯$$\sigma _{t\bar{t}}$$ has been measured in proton–proton collisions at s=13TeV$$\sqrt{s}=13\,\text {TeV}$$, using 140fb-1$$140\,{\text {fb}^{-1}} $$ of data collected by the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge eμ$$e\mu $$ pair and b-tagged jets, the cross-section is measured to be: σtt¯=829.3±1.3(stat)±8.0(syst)±7.3(lumi)±1.9(beam)pb,$$\begin{aligned} \sigma _{t\bar{t}} & = 829.3\pm 1.3\,\mathrm {(stat)}\ \pm 8.0\,\mathrm {(syst)}\ \pm 7.3\,\mathrm {(lumi)}\ \\ & \quad \pm 1.9\,\mathrm {(beam)}\,\textrm{pb}, \end{aligned}$$where the uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, the integrated luminosity, and the proton beam energy, giving a total uncertainty of 1.3%. The result is used to determine the top quark pole mass via the dependence of the predicted cross-section on mtpole$${m_{t}^\textrm{pole}}$$,...

Measurement of the top-quark mass using decays with a J/ψ meson at s=13 TeV with the ATLAS detector

Wed, 3 Jun 2026 00:00:00 +0000

The top-quark mass is measured using top-quark decays producing an isolated lepton and J/ψ meson reconstructed in its μ+μ− decay mode. The data sample was recorded with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of s=13$$ \sqrt{s}=13 $$ TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1. The measurement is based on the invariant mass m(ℓμ+μ−) of the system made of the isolated lepton ℓ from the W boson decay and the non-isolated μ+μ− pair from a J/ψ decay of a b-hadron, exploiting its sensitivity to the top-quark mass. An unbinned maximum-likelihood fit to the m(ℓμ+μ−) distribution is performed to extract the top-quark mass. The top-quark mass is measured to be mtop = 172.17 ± 0.80 (stat) ± 0.81 (syst) ± 1.07 (recoil) GeV, with a total uncertainty of 1.56 GeV. The third uncertainty arises from changing the dipole parton shower gluon-recoil scheme used in top-quark decays.

Measurement of coherent exclusive J/ψ → μ+μ− production in ultraperipheral Pb+Pb collisions at sNN=5.36 TeV with the ATLAS detector

Tue, 5 May 2026 00:00:00 +0000

The ATLAS experiment has performed a measurement of coherent exclusive J/ψ → μ+μ− production in ultraperipheral Pb+Pb collisions at sNN=5.36$$ \sqrt{s_{\textrm{NN}}}=5.36 $$ TeV. The data was recorded at the Large Hadron Collider (LHC) during 2023, and corresponds to an integrated luminosity of 79 μb−1. Exclusive J/ψ candidates were selected with a dedicated track-sensitive trigger based on the ATLAS transition radiation tracker. The analysis involves reconstruction of the dimuon invariant mass based on muon tracks from the inner detector, as the muon transverse momentum range of interest precludes the use of the standard muon reconstruction and identification algorithms. Differential cross sections are measured as a function of J/ψ rapidity and are compared with theoretical predictions. After extrapolation to sNN=5.02$$ \sqrt{s_{\textrm{NN}}}=5.02 $$ TeV, they are also compared with previous measurements performed by other experiments using data from LHC Run 2. While the results...

Measurement of the azimuthal anisotropy of charged particles in sNN=5.36TeV O16+O16 and Ne20+Ne20 collisions with the ATLAS detector

Tue, 5 May 2026 00:00:00 +0000

This paper presents the first measurements of the azimuthal anisotropy coefficients , which quantify the -order Fourier modulation of charged-particle azimuthal distributions, for in and collisions recorded with the ATLAS detector at the CERN Large Hadron Collider in 2025. The coefficients are measured as a function of transverse momentum ( ), collision centrality, and event multiplicity. They are extracted using two complementary methods: two-particle correlations with a template-fit subtraction of short-range nonflow contributions, and four-particle subevent cumulants, which intrinsically suppress nonflow effects and provide sensitivity to flow fluctuations. The results show a clear hierarchy and a nonmonotonic dependence on , reaching a maximum around , consistent with trends observed in heavy-ion collisions. Detailed comparisons between the two collision systems reveal an enhanced in central collisions, consistent with theory expectations based on the predicted...

Search for Higgs bosons produced in association with a high-energy photon via vector-boson fusion and decaying to a pair of b-quarks in the ATLAS detector

Tue, 5 May 2026 00:00:00 +0000

A search for Standard Model Higgs bosons produced in association with a high-energy photon and decaying to b b ¯ is performed using 133 fb − 1 of s = 13 TeV pp collision data collected with the ATLAS detector at the Large Hadron Collider at CERN. The photon requirement reduces the multijet background, and the H → b b ¯ decay is the dominant decay mode. Event selection requirements target events produced by vector-boson fusion, the dominant production mode in this channel. Several improvements enhance the search sensitivity compared to previous measurements. These improvements include better background modelling and characterization, the use of a neural-network classifier, and an updated signal extraction strategy adopting a direct binned-likelihood fit to the classifier output. With these improvements, the Higgs boson signal strength is measured to be 0.2 ± 0.7 relative to the Standard Model prediction. This corresponds to an observed significance of 0.3 standard deviations, compared...

Erratum: The environmental impact, carbon emissions and sustainability of computing in the ATLAS experiment

Tue, 5 May 2026 00:00:00 +0000

The worldwide distribution of ATLAS computing, based on the amount of CPU provided, in HS23 (see Sect. 4.1 for the precise definition of HS23), on average in 2023–2024. Countries in gray did not contribute significant CPU One correction is noted for the paper [1], which does not affect the results reported. The vertical axis range of the legend of Fig. 1 is corrected as it was reversed in the original publication.

Measurements of differential cross-sections of WbWb production in the dilepton channel in pp collisions at s=13 TeV using the ATLAS detector

Tue, 24 Mar 2026 00:00:00 +0000

At the Large Hadron Collider, the WbWb final state is expected to be dominated by tt¯$$ t\overline{t} $$ production with a contribution from single-top processes. Differential cross-sections for WbWb production in the dilepton decay channel are measured at the particle level as a function of various kinematic variables. The analysis is based on data from proton-proton collisions at a centre-of-mass energy of s=13$$ \sqrt{s}=13 $$ TeV, recorded by the ATLAS detector at the Large Hadron Collider over the period from 2015 to 2018, corresponding to an integrated luminosity of 140 fb−1. Measurements are performed within the fiducial phase-space defined by the presence of two b-jets and one electron and one muon of opposite charges. The differential cross-sections are corrected for detector effects and unfolded to the particle level. Results are compared with predictions from Monte Carlo event generators at next-to-leading order in perturbative quantum chromodynamics; overall the measurements...

Erratum: Precision measurement of the B0 meson lifetime using B0→J/ψK∗0 decays with the ATLAS detector

Tue, 24 Mar 2026 00:00:00 +0000

Erratum: Precision measurement of the B0 meson lifetime using B0→J/ψK∗0 decays with the ATLAS detector

Study of Higgs boson pair production in the H H → b b ‾ γ γ final state with 308 fb − 1 of data collected at s = 13 TeV and 13.6 TeV by the ATLAS experiment

Tue, 24 Mar 2026 00:00:00 +0000

A search for Higgs boson pair production in the b b ¯ γ γ final state is performed. The proton–proton collision dataset corresponds to an integrated luminosity of 308 fb − 1 , consisting of two samples, 140 fb − 1 at a centre-of-mass energy of s = 13 TeV and 168 fb − 1 at s = 13.6 TeV , recorded between 2015 and 2024 by the ATLAS detector at the CERN Large Hadron Collider. In addition to a larger dataset, this analysis improves upon the previous search in the same final state through several methodological and technical developments. The Higgs boson pair production cross section divided by the Standard Model prediction is found to be μ H H = 0 . 9 − 1.1 + 1.4 ( μ H H = 1 − 1.0 + 1.3 expected), which translates into a 95% confidence-level upper limit of μHH  < 3.7. At the same confidence level the Higgs self-coupling modifier is constrained to be in the range − 1.6 < κ λ < 6.6 ( − 1.8 < κ λ < 6.9 expected).

Search for Beyond the Standard Model physics with anomaly detection in multilepton final states in pp collisions at s=13TeV with the ATLAS detector

Tue, 24 Mar 2026 00:00:00 +0000

A model-agnostic search for Beyond the Standard Model physics is presented, targeting final states with at least four light leptons (electrons or muons). The search regions are separated by event topology and unsupervised machine learning is used to identify anomalous events in the full 140 fb-1$$^{-1}$$ of proton–proton collision data collected with the ATLAS detector during Run 2. No significant excess above the Standard Model background expectation is observed. Model-agnostic limits are presented in each topology, along with limits on several benchmark models including vector-like leptons, wino-like charginos and neutralinos, or smuons. Limits are set on the flavourful vector-like lepton model for the first time.

Observation of t t ¯ γ γ production at s = 13 TeV with the ATLAS detector

Tue, 24 Mar 2026 00:00:00 +0000

This paper presents the first observation of top-quark pair production in association with two photons ( t t ¯ γ γ ). The measurement is performed in the single-lepton decay channel using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider. The data correspond to an integrated luminosity of 140 fb − 1 recorded during Run 2 at a centre-of-mass energy of 13 TeV. The t t ¯ γ γ production cross section, measured in a fiducial phase space based on particle-level kinematic criteria for the lepton, photons, and jets, is found to be 2 . 42 − 0.53 + 0.58 fb , corresponding to an observed significance of 5.2 standard deviations. Additionally, the ratio of the production cross section of t t ¯ γ γ to top-quark pair production in association with one photon is determined, yielding ( 3 . 30 − 0.65 + 0.70 ) × 10 − 3 .

Search for heavy neutral leptons in decays of W bosons produced in 13 TeV pp collisions using prompt signatures in the ATLAS detector

Tue, 24 Feb 2026 00:00:00 +0000

The existence of right-handed neutrinos with Majorana masses below the electroweak scale could help address the origins of neutrino masses, the matter–antimatter asymmetry, and dark matter. In this paper, leptonic decays of W bosons from 140 fb-1$$^{-1}$$ of 13 TeV proton–proton collisions at the LHC, reconstructed in the ATLAS experiment, are used to search for heavy neutral leptons produced through their mixing with muon or electron neutrinos in a scenario with lepton number violation. The search is conducted using prompt leptonic decay signatures. The considered final states require two same-charge leptons or three leptons, while vetoing three-lepton same-flavour topologies. No significant excess over the expected Standard Model backgrounds is found, leading to constraints on the heavy neutral lepton’s mixing with muon and electron neutrinos for heavy-neutral-lepton masses. The analysis excludes |Ue|2$$|U_{e}|^2$$ values above 8×10-5$$8\times 10^{-5}$$ and |Uμ|2$$|U_{\mu...

Curvilinear Magnonic Crystal Based on 3D Hierarchical Nanotemplates

Tue, 17 Feb 2026 00:00:00 +0000

Curvilinear magnetic nanostructures enable control of magnetization dynamics through geometry-induced anisotropy and chiral interactions, as well as magnetic field modulation. In this work, we report a curvilinear magnonic crystal based on large-area square arrays of truncated nanospikes fabricated by conformal coating of 3D hierarchical templates with permalloy thin films. Brillouin light scattering spectroscopy reveals an anisotropic band structure with multiple dispersive and folded Bloch-type dispersive spin-wave modes as well as nondispersive modes exhibiting direction-dependent frequency shifts and intensity asymmetries along lattice principal axes. Finite element micromagnetic simulations indicate that curvature-induced variations of the demagnetizing field govern the magnonic response, enabling the identification of modes propagating in nanochannels and others localized on nanospike apexes or along the ridges connecting adjacent nanospikes. The combination of geometric...

Measurement of the top-quark Yukawa coupling from tt¯ production in the lepton+jets final state using pp collisions at s=13 TeV with the ATLAS detector

Tue, 10 Feb 2026 00:00:00 +0000

The top-quark Yukawa coupling is extracted from the distribution of the top-quark pair (tt¯$$ t\overline{t} $$) invariant mass in proton-proton collisions using 140 fb−1 of data at s=13$$ \sqrt{s}=13 $$ TeV collected in 2015–2018 by the ATLAS experiment at the Large Hadron Collider. In the region near the production threshold, the tt¯$$ t\overline{t} $$ invariant mass spectrum is sensitive to electroweak virtual corrections, including contributions from Higgs boson exchange, thereby providing sensitivity to the top-quark Yukawa coupling. This is the first measurement in ATLAS that aims to obtain this coupling exploiting this approach. The tt¯$$ t\overline{t} $$ system is reconstructed in the single-lepton final state, requiring exactly one isolated electron or muon and at least four jets with at least two identified as originating from b-quarks. The measured Yukawa coupling is found to be in good agreement with the Standard Model prediction. An upper limit on the top-quark Yukawa...

Low Frequency Vibrational Modes of Two-Dimensional Lead-Free Metal Halide Double Perovskites

Sat, 7 Feb 2026 00:00:00 +0000

2D layered double perovskites of (S-MPA)4AgBiI8 (MPA-AgBiI8) and (S-MPA)4CuBiI8 (MPA-CuBiI8) (S-MPA, S-β-methylphenethylammonium) were synthesized with a hydrothermal method. The crystal structure of MPA-AgBiI8 was determined using single-crystal X-ray diffraction (scXRD). Powder XRD (pXRD) data suggest that the crystal structure of MPA-CuBiI8 is more complex than that of MPA-AgBiI8. UV–vis electronic absorption spectra of these perovskites reveal a bandgap of 2.03 eV for both. Short exciton lifetime from time-resolved photoluminescence (TRPL) results and low PL intensity of the Cu-based perovskite suggest a high density of trap states within the bandgap. Low frequency Raman spectra of both materials show distinct peaks and a slightly higher frequency for the Cu-based perovskite than the Ag-based perovskite. Density functional theory (DFT) calculations were conducted to simulate the low frequency Raman spectra and help explain the different phonon modes, which are collective vibrations...

Evidence for the Dimuon Decay of the Higgs Boson in pp Collisions with the ATLAS Detector