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DOE OSTI2025

Observation of η c ( 1 S , 2 S ) and χ c J decays to 2 ( π + π − ) η via ψ ( 3686 ) radiative transitions

Based on ( 2712.4 ± 14.1 ) × 10 6 ψ ( 3686 ) decays collected with the BESIII detector, we have observed, for the first time, the hadronic decays of S- and P-wave charmonium states into 2 ( π + π − ) η via radiative transitions from ψ ( 3686 ) . The branching fraction of the decay η c ( 1 S ) → 2 ( π + π − ) η has a significant dependence on the interference pattern between η c ( 1 S ) and non- η c ( 1 S ) processes. We measure it in both the destructive and constructive interference scenarios for the first time. The mass and width of the η c ( 1 S ) are measured to be M = ( 2984.14 ± 0.13 ± 0.38 ) MeV / c 2 and Γ = ( 28.82 ± 0.11 ± 0.82 ) MeV , respectively. Clear signals for the decays of the χ c J ( J = 0 , 1 , 2 ) and the η c ( 2 S ) to 2 ( π + π − ) η are also observed for the first time, and the corresponding branching fractions are measured. The ratio of the branching fractions between the η c ( 2 S ) and η c ( 1 S ) decays is significantly lower than the theoretical prediction, which might suggest different dynamics in their decays. Published by the American Physical Society 2025

Ablikim, M.↗

DOE OSTI2026

Search for resonances decaying to an anomalous jet and a Higgs boson in proton–proton collisions at $\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V}$

This paper presents a search for new physics through the process where a massive particle, X, decays into a Higgs boson and a second particle, Y. The Higgs boson subsequently decays into a bottom quark–antiquark pair, which is reconstructed as a single large-radius jet. The decay products of Yare also assumed to produce a single large-radius jet. The identification of the Yparticle is enhanced by computing the anomaly score of its candidate jet using an autoencoder, which measures deviations from typical quark- or gluon-induced jets. This allows a simultaneous search for multiple Ydecay scenarios within a single analysis. In the main benchmark process, Yis a scalar particle that decays into a Wboson pair. Two other scalar Ydecay processes are also considered as benchmarks: decays to a light quark–antiquark pair, and decays to a top quark–antiquark pair. A fourth benchmark process considers Yas a hadronically decaying top quark, arising from the decay of a vector-like quark into a top quark and a Higgs boson. Data recorded by the CMS experiment at a center-of-mass energy of 13 TeV in 2016–2018, corresponding to an integrated luminosity of 138 fb -1 , are analyzed. The search covers Xmasses between 1.4 and 3.0 TeV and Ymasses between 90 and 400 TeV, with all simulated signals produced in the narrow-width approximation. No significant excess above the standard model background expectation is observed. The most stringent upper limits to date are placed on benchmark signal cross sections for various masses of X and Y particles

Hayrapetyan, A. [Yerevan Physics Institute]↗

DOE OSTI2025

Search for Higgs boson decays into a pair of pseudoscalar particles in the γγτhadτhad final state using pp collisions at s = 13 TeV with the ATLAS detector

A search for exotic decays of the 125 GeV Higgs boson into a pair of new spin-0 particles, H → aa, where one decays into a photon pair and the other into a τ-lepton pair, is presented. Hadronic decays of the τ-leptons are considered and reconstructed using a dedicated tagger for collimated τ-lepton pairs. The search uses 140 fb−1 of proton-proton collision data at a centre-of-mass energy of s$$ \sqrt{s} $$ = 13 TeV recorded between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider. The search is performed in the mass range of the a boson between 10 GeV and 60 GeV. No significant excess of events is observed above the Standard Model background expectation. Model-independent upper limits at 95% confidence level are set on the branching ratio of the Higgs boson to the γγττ final state, B$$ \mathcal{B} $$(H → aa → γγττ), ranging from 0.2% to 2%, depending on the a-boson mass hypothesis.

Aad, G↗

DOE OSTI2024

Search for long-lived particles using displaced vertices and missing transverse momentum in proton-proton collisions at s = 13 TeV

A search for the production of long-lived particles in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC is presented. The search is based on data collected by the CMS experiment in 2016–2018, corresponding to a total integrated luminosity of 137 fb − 1 . This search is designed to be sensitive to long-lived particles with mean proper decay lengths between 0.1 and 1000 mm, whose decay products produce a final state with at least one displaced vertex and missing transverse momentum. A machine learning algorithm, which improves the background rejection power by more than an order of magnitude, is applied to improve the sensitivity. The observation is consistent with the standard model background prediction, and the results are used to constrain split supersymmetry (SUSY) and gauge-mediated SUSY breaking models with different gluino mean proper decay lengths and masses. This search is the first CMS search that shows sensitivity to hadronically decaying long-lived particles from signals with mass differences between the gluino and neutralino below 100 GeV. It sets the most stringent limits to date for split-SUSY models and gauge-mediated SUSY breaking models with gluino proper decay length less than 6 mm. © 2024 CERN, for the CMS Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2025

Locality in collider tests of quantum mechanics with top quark pairs

Tests of quantum properties of fundamental particles in high energy colliders are starting to appear. Entanglement and Bell inequality violation in top and antitop quark system is of particular interest since top quarks are unstable particles that undergo a cascade decay. We argue for criteria for the spacelike separation between top and antitop quarks at their different decay stages. We considered causal separation at three different instances: at the top quark decay, at the 𝑊 boson decay, and at the lepton/jet contact with the macroscopic apparatus. We showed that the spacelike fraction of events is the smallest, when requiring that both top quarks and 𝑊 bosons decay within the spacelike interval. For high invariant masses, typically required for the Bell inequality violation, this is almost identical to just the top quark decay requirement. We also include an option for the angular correlation of the 𝑏 quarks from top quark decay to be used for the spin correlation measurement. We require that both top quark and 𝑏 hadron decays are spacelike separated. Again, we find that at high invariant masses it is almost identical to just the requirement of spacelike separation between top and antitop quarks. We provide numerical values for our proposed criteria. If such a criterion is satisfied, the system is guaranteed to not be in a causal connection.

Entanglement in field theory↗

DOE OSTI2025

Bottomonium meson spectrum with quenched and unquenched quark models

An open question in hadronic phenomenology concerns the “unquenching” effects of higher Fock space components on the leading Fock space description of hadrons. Here, we address this by making a comparison of the bottomonium spectrum as computed with the relativized Godfrey–Isgur quark model and an unquenched coupled channel model driven by the “$^3P_0$” mechanism of hadronic decay. Our results show that both models can describe the spectrum well, indicating that the influence of coupled channel effects can be largely absorbed into the parameters of the quenched quark model. This conclusion is reinforced by a perturbative calculation that shows that the spin-dependence of mass splittings due to mixing with the continuum recapitulates quenched quark model spin-dependent interactions. We also show that softening of the quark-antiquark wavefunction due to continuum mixing improves the description of vector bottomonium decay constants. Together, these results illustrate and substantiate the surprising robustness of simple constituent quark model descriptions of hadrons.

Sultan, M. Atif [Nankai Univ., Tianjin (China); Un↗

DOE OSTI2026

Multiplicity dependence of K*(892) ± production in pp collisions at $\sqrt{s}$ = 13 TeV

The first results of K*(892) ± production at midrapidity (|y| < 0.5) in pp collisions at $\sqrt{s}$= 13 TeV as a function of the event multiplicity are presented. The K*(892) ± has been reconstructed via its hadronic decay channel K*(892) ± → π ± + K$^0_{\textrm{S}}$ using the ALICE detector at the LHC. For each multiplicity class, the differential transverse momentum (p T ) spectrum, the mean transverse momentum ⟨p T ⟩, the p T -integrated yield (dN/dy), and the ratio of the K*(892) ± to K$^0_{\textrm{S}}$ yields are reported. These are consistent with previous K*(892) 0 resonance results with a higher level of precision. Comparisons with phenomenological models such as PYTHIA6, PYTHIA8, EPOS-LHC, and DIPSY are also discussed. For the first time, a significant K*(892) ± /K$^0_{\textrm{S}}$ suppression in pp collisions is observed at a 7σ level passing from low to high multiplicity events. The ratios of the p T -differential yields of K*(892) ± and K$^0_{\textrm{S}}$ in high and low multiplicity events are also presented along with their double ratio. For p T ≲ 2 GeV/c this double ratio persists below unity by more than 3σ suggesting that the suppression affects mainly low p T resonances. The measured decreasing trend of the K*(892) ± /K$^0_{\textrm{S}}$ ratio with increasing multiplicity, which in heavy-ion collisions is typically attributed to the rescattering of decay particles of the short-lived resonances, is reproduced by the EPOS-LHC model without the use of hadronic afterburners.

Hadronic resonance production↗

DOE OSTI2024

Three-point energy correlators in hadronic Higgs boson decays

We present the analytic calculation of the leading-order three-point energy correlator (EEEC) in hadronic Higgs decays, including both the gluon-initiated channel H → g g + X and quark-initiated channel H → q q ¯ + X . The phase-space integration is evaluated directly using Mandelstam variables s i j = ( p i + p j ) 2 , and the appearing square roots can be rationalized by either conformal ratios or celestial coordinate variables. Throughout the calculation, we observe the same transcendental function space as in N = 4 super–Yang-Mills theory and e + e − → hadrons . Different infrared limits are also explored using the full analytic result, offering the fixed-order data for EEEC factorization and resummation. Given its nontrivial shape dependence, the EEEC presents an excellent opportunity to explore the dynamics of gluon jets originating from the H → g g decay channel at future lepton colliders. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2025

Measurement of the W boson decay branching fraction ratio $\mathscr{B}$(W → cq)/$\mathscr{B}$(W →$q\bar{q}'$) in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The most precise measurement to date of the W boson hadronic decay branching fraction ratio $R_{c}^{W} = \mathcal{B}(W \to cq) / \mathcal{B}(W \to q\bar{q}$) is presented. The measurement is based on a sample of proton-proton collision data from the CERN LHC collected by the CMS experiment at a center-of-mass energy of 13 TeV in 2016-2018 with an integrated luminosity of 138 fb$^{-1}$. The large cross section of top quark-antiquark production at the LHC offers a sizable high-purity sample of W bosons suitable for this measurement. Events with one charged lepton (electron or muon) and at least four jets, two tagged as bottom quark jets, are analyzed. Charm jets are tagged using the presence of a muon inside the jet. The result, $R_\mathrm{c}^\mathrm{W}$ = 0.489 $\pm$ 0.020, is consistent with the standard model prediction and is twice as precise as the current world-average value.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Contribution of coherent electron production to measurements of heavy-flavor decayed electrons in heavy-ion collisions

Abstract Heavy quarks, produced at early stages of heavy-ion collisions, are an excellent probe of the Quark-Gluon Plasma (QGP) also created in these collisions. Electrons from open heavy-flavor hadron decays (HFE) are good proxies for heavy quarks, and have been measured extensively in the last two decades to study QGP properties. These measurements are traditionally carried out by subtracting all known background sources from the inclusive electron sample. More recently, a significant enhancement of $$e^+e^-$$ e + e - pair production at very low transverse momenta was observed in peripheral heavy-ion collisions. The production characteristics is consistent with coherent photon–photon interactions, which should also constitute a background source to the HFE measurements. In this article, we provide theoretical predictions for the contribution of coherent electron production to HFEs as a function of transverse momentum, centrality and collision energy in Au+Au and Pb+Pb collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Search for charged-lepton-flavor violating μ τ q t interactions in top-quark production and decay in p p collisions at s = 13 TeV with the ATLAS detector at the LHC

A search for charged-lepton-flavor violating μ τ q t (q = u, c) ) interactions is presented, considering both top-quark production and decay. The data analyzed correspond to 140 fb -1 of proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The analysis targets events containing two muons with the same electric charge, a hadronically decaying $\tau$ -lepton and at least one jet, with exactly one b -tagged jet, produced by a μ τ q t interaction. Agreement with the Standard Model expectation within 1.6 standard deviations is observed, and limits are set at the 95% confidence level (CL) on the charged-lepton-flavor violation branching ratio of $\mathcal{B}$(t → μ$\tau$q) < 8.7 x 10 -7 . An effective field theory interpretation is performed yielding 95% CL limits on Wilson coefficients, dependent on the flavor of the associated light quark and the Lorentz structure of the coupling. These range from |c$^{3(2313)}_{lequ}$|Λ 2 < 0.10 TeV -2 for μ$\tau$ut to |c$^{1(2323)}_{lequ}$| /Λ 2 < 1.8 TeV -2 for μ$\tau$ct. An additional interpretation is performed for scalar leptoquark production inducing charged-lepton-flavor violation, with fixed intergenerational couplings. Upper limits on leptoquark coupling strengths are set at the 95% CL, ranging from $\lambda$ LQ = 1.3 to $\lambda$ LQ =3.7 for leptoquark masses between 0.5 and 2.0 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Search for a scalar or pseudoscalar dilepton resonance produced in association with a massive vector boson or top quark-antiquark pair in multilepton events at s = 13 TeV

A search for beyond the standard model spin-0 bosons, ϕ , that decay into pairs of electrons, muons, or tau leptons is presented. The search targets the associated production of such bosons with a W or Z gauge boson, or a top quark-antiquark pair, and uses events with three or four charged leptons, including hadronically decaying tau leptons. The proton-proton collision data set used in the analysis was collected at the LHC from 2016 to 2018 at a center-of-mass energy of 13 TeV, and corresponds to an integrated luminosity of 138 fb - 1 . The observations are consistent with the predictions from standard model processes. Upper limits are placed on the product of cross sections and branching fractions of such new particles over the mass range of 15 to 350 GeV with scalar, pseudoscalar, or Higgs-boson-like couplings, as well as on the product of coupling parameters and branching fractions. Several model-dependent exclusion limits are also presented. For a Higgs-boson-like ϕ model, limits are set on the mixing angle of the Higgs boson with the ϕ boson. For the associated production of a ϕ boson with a top quark-antiquark pair, limits are set on the coupling to top quarks. Finally, limits are set for the first time on a fermiophilic dilaton-like model with scalar couplings and a fermiophilic axion-like model with pseudoscalar couplings.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Test of lepton flavor universality in B ± → K ± μ + μ – and B ± → K ± e + e – decays in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A test of lepton flavor universality in B ± → K ± μ + μ – and B ± → K ± e + e – decays, as well as a measurement of differential and integrated branching fractions of a nonresonant B ± → K ± μ + μ – decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded in 2018, by the CMS experiment at the LHC, using a special high-rate data stream designed for collecting about 10 billion unbiased b hadron decays. The ratio of the branching fractions B(B ± → K ± μ + μ – ) to B(B ± → K ± e + e – ) is determined from the measured double ratio R(K) of these decays to the respective branching fractions of the B ± → J/ψK ± with J/ψ → μ + μ – and e + e – decays, which allow for significant cancellation of systematic uncertainties. The ratio R(K) is measured in the range 1.1 < q 2 < 6.0 GeV 2 , where q is the invariant mass of the lepton pair, and is found to be R(K) = 0.78$^{+0.47}_{-0.23}$, in agreement with the standard model expectation R(K) ≈ 1. This measurement is limited by the statistical precision of the electron channel. The integrated branching fraction in the same q 2 range, B(B ± → K ± μ + μ – ) = (12.42 ± 0.68) x 10 -8 , is consistent with the present world-average value and has a comparable precision.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2026

Search for Long-Lived Particles with Muon Detector Shower Signature in the CMS Run-3 data

Many beyond standard model theories predict the existence of long-lived particles (LLPs). These LLPs can have sizable lifetimes and decay several meters from their production vertex. In this poster/talk, we present the analysis strategy for searching for LLPs using the Compact Muon Solenoid (CMS) Experiment. The proton-proton collision data used in this analysis were collected from 2022 to 2024 at a center-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 170 fb^-1. The LLP decays are reconstructed as a high-multiplicity cluster of detector hits in the cathode strip chambers (CSC) of the muon system endcap. This signature is referred to as the Muon Detector Showers (MDS). This search requires events to contain at least one MDS cluster. The analysis focuses on LLP hadronic decays and LLP masses up to a few tens of GeV. We present the signal properties in MonteCarlo simulation, event selection, background modeling, and evaluation of the expected sensitivity. The results are interpreted under the Twin Higgs model benchmark.

Agyemang-Duah, Andrews [Grambling State U.]↗

DOE OSTI2025

Measurement of f1(1285) production in pp collisions at $\sqrt{s}$ = 13 TeV

This study presents the first measurement of the f 1 (1285) resonance using the ALICE detector in inelastic proton–proton collisions at a center-of-mass energy of 13 TeV. The resonance is reconstructed at midrapidity (|y| < 0.5) through the hadronic decay channel f 1 (1285)→ K$^0_S$K ± π ± . Key measurements include the determination of its mass, transverse-momentum integrated yield, and average transverse momentum. Additionally, the ratio of the transverse-momentum integrated yield of f 1 (1285) to pion is compared with calculations from the canonical statistical hadronization model. The model calculation, assuming a zero total strangeness content for f 1 (1285), reproduces the data within 1σ deviation, shedding light on the quark composition of f 1 (1285).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2025

Energy scale and resolution for anti-$k_t$ jets with radius parameters $R$ = 0.2 and 0.6 measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

Jets with different radius parameters R are an important tool for probing quantum chromodynamics processes at different angular scales. Jets with small R = 0.2 are instrumental in measurements of the substructure of large-R jets resulting from collimated hadronic decays of energetic W, Z, and Higgs bosons, top quarks, and of potential new resonances. This paper presents measurements of the energy scale, resolution, and associated uncertainties of jets with radius parameters R = 0.2 and 0.6, obtained using the ATLAS detector. The results are based on 37 fb -1 of proton–proton collision data from the Large Hadron Collider at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. A new in situ method for measuring jet energy scale differences between data and Monte Carlo simulations is presented. The systematic uncertainties in the jet energy scale for central jets $(|\eta | < 1.2)$ typically vary from 1% to about 5% as a function of $|\eta |$ at very low transverse momentum, $p_T$ of around 20 GeV for both R = 0.2 and 0.6 jets. The relative energy resolution ranges from (35 ± 6)% at $p_T$ = 20 GeV to (6 ± 0.5)% at $p_T$ = 300 GeV for central R = 0.2 jets, and is found to be slightly worse for R + 0.6 jets. Finally, the effect of close-by hadronic activity on the jet energy scale is investigated and is found to be well modelled by the ATLAS Monte Carlo simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Search for new particles in final states with a boosted top quark and missing transverse momentum in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search for events with one top quark and missing transverse momentum in the final state is presented. The fully hadronic decay of the top quark is explored by selecting events with a reconstructed boosted top-quark topology produced in association with large missing transverse momentum. The analysis uses 139 fb -1 of proton-proton collision data at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV recorded during 2015-2018 by the ATLAS detector at the Large Hadron Collider. The results are interpreted in the context of simplified models for Dark Matter particle production and the single production of a vector-like T quark. Without significant excess relative to the Standard Model expectations, 95% confidence-level upper limits on the corresponding cross-sections are obtained. The production of Dark Matter particles in association with a single top quark is excluded for masses of a scalar (vector) mediator up to 4.3 (2.3) TeV, assuming m χ = 1 GeV and the model couplings λ q = 0.6 and λ χ = 0.4 (a = 0.5 and g χ = 1). The production of a single vector-like T quark is excluded for masses below 1.8 TeV assuming a coupling to the top quark κ T = 0.5 and a branching ratio for T → Zt of 25%.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Search for high-mass resonances in final states with a τ-lepton and missing transverse momentum with the ATLAS detector

A search for high-mass resonances decaying into a τ-lepton and a neutrino using proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ =13 TeV is presented. The full run 2 data sample corresponding to an integrated luminosity of 139 fb -1 recorded by the ATLAS experiment in the years 2015–2018 is analyzed. The τ-lepton is reconstructed in its hadronic decay modes and the total transverse momentum carried out by neutrinos is inferred from the reconstructed missing transverse momentum. The search for new physics is performed on the transverse mass between the τ-lepton and the missing transverse momentum. No excess of events above the Standard Model expectation is observed and upper exclusion limits are set on the W' →τ⁢v production cross section. Heavy W' vector bosons with masses up to 5.0 TeV are excluded at 95% confidence level, assuming that they have the same couplings as the Standard Model W boson. For nonuniversal couplings, W' bosons are excluded for masses less than 3.5–5.0 TeV, depending on the model parameters. In addition, model-independent limits on the visible cross section times branching ratio are determined as a function of the lower threshold on the transverse mass of the τ-lepton and missing transverse momentum.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗