Static energy in ( 2 + 1 + 1 )-flavor lattice QCD: Scale setting and charm effects
Not Available
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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Flavor SU(3) in Cabibbo-favored D -meson decays
Model-independent description of nonleptonic decays of charmed mesons is a challenging task due to large nonperturbative effects of strong interactions on the transition amplitudes. We discuss the equivalence of two different flavor-SU(3)-based descriptions of Cabibbo-favored non-leptonic decays of charmed mesons to two-pseudoscalars final states including the η and η' mesons.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Measurement of the time-integrated C P asymmetry in D 0 → K S 0 K S 0 decays using Belle and Belle II data
We measure the time-integrated C P asymmetry in D 0 → K S 0 K S 0 decays reconstructed in e + e − → c c ¯ events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and 428 fb − 1 , respectively. The D 0 decays are required to originate from the D * + → D 0 π + decay, which determines the charm flavor at production time. A control sample of D 0 → K + K − decays is used to correct for production and detection asymmetries. The result, ( − 1.4 ± 1.3 ( stat ) ± 0.1 ( syst ) ) % , is consistent with previous determinations and with C P symmetry. Published by the American Physical Society 2025
Adachi, I. (ORCID:0000000322870173)↗
Scalar and Tensor Charmonium Resonances in Coupled-Channel Scattering from Lattice QCD
We determine J P C = 0 + + and 2 + + hadron-hadron scattering amplitudes in the charmonium energy region up to 4100 MeV using lattice QCD, a first-principles approach to QCD. Working at m π ≈ 391 MeV , more than 200 finite-volume energy levels are computed and these are used in extensions of the Lüscher formalism to determine infinite-volume coupled-channel scattering amplitudes. We find that this energy region contains a single χ c 0 and a single χ c 2 resonance. Both are found as pole singularities on the closest unphysical Riemann sheet, just below 4000 MeV with widths around 70 MeV. The largest couplings are to kinematically closed D * D ¯ * channels in S -wave, and couplings to several decay channels consisting of pairs of open-charm mesons are found to be large and significant in both cases. Above the ground state χ c 0 , no other scalar bound states or near- D D ¯ threshold resonances are found, in contrast to several theoretical and experimental studies. Published by the American Physical Society 2024
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g - 2) μ with large-N c Regge models
While the low-energy part of the hadronic light-by-light (HLbL) tensor can be constrained from data using dispersion relations, for a full evaluation of its contribution to the anomalous magnetic moment of the muon (g – 2) μ also mixed- and high-energy regions need to be estimated. Both can be addressed within the operator product expansion (OPE), either for configurations where all photon virtualities become large or one of them remains finite. Imposing such short-distance constraints (SDCs) on the HLbL tensor is thus a major aspect of a model-independent approach towards HLbL scattering. Here, we focus on longitudinal SDCs, which concern the amplitudes containing the pseudoscalar-pole contributions from π o , η, η'. Since these conditions cannot be fulfilled by a finite number of pseudoscalar poles, we consider a tower of excited pseudoscalars, constraining their masses and transition form factors from Regge theory, the OPE, and phenomenology. Implementing a matching of the resulting expressions for the HLbL tensor onto the perturbative QCD quark loop, we are able to further constrain our calculation and significantly reduce its model dependence. We find that especially for the π0 the corresponding increase of the HLbL contribution is much smaller than previous prescriptions in the literature would imply. Overall, we estimate that longitudinal SDCs increase the HLbL contribution by Δa$^{LSDC}_{μ}$ = 13(6) × 10 -11 . This number does not include the contribution from the charm quark, for which we find a$^{c–quark}_{μ}$ = 3(1) × 10 –11 .
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Long-distance contribution to ε K from lattice QCD
A lattice QCD approach to the calculation of the long-distance contributions to ε K is presented. This parameter describes indirect C P violation in K → π π decay. While the short-distance contribution to ε K can be accurately calculated in terms of standard model parameters and a single hadronic matrix element, B K , there is a long-distance part which is estimated to be approximately 5% of the total and is more difficult to determine. A method for determining this small but phenomenologically important contribution to ε K using lattice QCD is proposed and a complete exploratory calculation of the contribution is presented. This exploratory calculation uses an unphysical light quark mass corresponding to a 339 MeV pion mass and an unphysical charm quark mass of 968 MeV, expressed in the MS ¯ scheme at 2 GeV. This calculation demonstrates that future work should be able to determine this long-distance contribution from first principles with a controlled error of 10% or less. Published by the American Physical Society 2024
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for charged-lepton flavor violation in the production and decay of top quarks using trilepton final states in proton-proton collisions at $\sqrt{s}$ =13 TeV
A search is performed for charged-lepton flavor violating processes in top quark (𝑡) production and decay. The data were collected by the CMS experiment from proton-proton collisions at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 138 fb −1 . The selected events are required to contain one opposite-sign electron-muon pair, a third charged lepton (electron or muon), and at least one jet of which no more than one is associated with a bottom quark. Boosted decision trees are used to distinguish signal from background, exploiting differences in the kinematics of the final states particles. The data are consistent with the standard model expectation. Upper limits at 95% confidence level are placed in the context of effective field theory on the Wilson coefficients, which range between 0.024–0.424 TeV −2 depending on the flavor of the associated light quark and the Lorentz structure of the interaction. These limits are converted to upper limits on branching fractions involving up (charm) quarks, 𝑡 → 𝑒𝜇𝑢 (𝑡 → 𝑒𝜇𝑐), of 0.032(0.498) × 10 −6 , 0.022(0.369) × 10 −6 , and 0.012(0.216) × 10 −6 for tensorlike, vectorlike, and scalarlike interactions, respectively.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Deciphering the mechanism of near-threshold $$J/\psi $$ photoproduction
Abstract The photoproduction of the $$J/\psi $$ J / ψ off the proton is believed to deepen our understanding of various physics issues. On the one hand, it is proposed to provide access to the origin of the proton mass, based on the QCD multipole expansion. On the other hand, it can be employed in a study of pentaquark states. The process is usually assumed to proceed through vector-meson dominance, that is the photon couples to a $$J/\psi $$ J / ψ which rescatters with the proton to give the $$J/\psi p$$ J / ψ p final state. In this paper, we provide a compelling hint for and propose measurements necessary to confirm a novel production mechanism via the $$\varLambda _c \bar{D}^{(*)}$$ Λ c D ¯ ( ∗ ) intermediate states. In particular, there must be cusp structures at the $$\varLambda _c \bar{D}^{(*)}$$ Λ c D ¯ ( ∗ ) thresholds in the energy dependence of the $$J/\psi $$ J / ψ photoproduction cross section. The same mechanism also implies the $$J/\psi $$ J / ψ -nucleon scattering lengths of order 1 mfm. Given this, one expects only a minor contribution of charm quarks to the nucleon mass.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Studies of charm quark diffusion inside jets using PbPb and pp collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV
The first study of charm quark diffusion with respect to the jet axis in heavy ion collisions is presented. The measurement is performed using jets with $p^{jet}_T > 60 GeV / c$ and $D^0$ mesons with $p^D_T > 4 GeV / c$ in lead-lead (Pb-Pb) and proton-proton ($pp$) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{NN}} = 5.02 TeV$, recorded by the CMS detector at the LHC. The radial distribution of $D^0$ mesons with respect to the jet axis is sensitive to the production mechanisms of the meson, as well as to the energy loss and diffusion processes undergone by its parent parton inside the strongly interacting medium produced in Pb-Pb collisions. When compared to Monte Carlo event generators, the radial distribution in $pp$ collisions is found to be well described by pythia, while the slope of the distribution predicted by sherpa is steeper than that of the data. In Pb-Pb collisions, compared to the $pp$ results, the $D^0$ meson distribution for $4 < p^D_T < 20 GeV / c$ hints at a larger distance on average with respect to the jet axis, reflecting a diffusion of charm quarks in the medium created in heavy ion collisions. At higher $p^D_T$, the Pb-Pb and $pp$ radial distributions are found to be similar.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
First measurements of the absolute branching fraction of Λ c ( 2625 ) + → Λ c + π + π − and upper limit on Λ c ( 2595 ) + → Λ c + π + π −
The absolute branching fraction of the decay Λ c ( 2625 ) + → Λ c + π + π − is measured for the first time to be ( 50.2 ± 5.7 stat ± 3.5 syst ) % with 368.48 pb − 1 of e + e − collision data collected by the BESIII detector at the center-of-mass energies of s = 4.918 and 4.950 GeV. Although the central value of the result is lower than the theoretical prediction of 67%, obtained from isospin symmetry, they are consistent taking the uncertainties into account. This is the first absolute branching fraction measurement for Λ c ( 2625 ) + since it was found. This measurement is necessary to obtain the coupling constants for the transitions between s -wave and p -wave charmed baryons in heavy hadron chiral perturbation theory. In addition, we search for the decay Λ c ( 2595 ) + → Λ c + π + π − . No significant signal is observed, and the upper limit on its branching fraction is determined to be 85.0% at the 90% confidence level. Published by the American Physical Society 2024
Astronomy & Astrophysics↗
Charmed hadron chemistry in relativistic heavy-ion collisions
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A precise electron EDM constraint on CP-odd heavy-quark Yukawas
CP-odd Higgs couplings to bottom and charm quarks arise in many extensions of the standard model and are of potential interest for electroweak baryogenesis. These couplings induce a contribution to the electron EDM. The experimental limit on the latter then leads to a strong bound on the CP-odd Higgs couplings. We point out that this bound receives large QCD corrections, even though it arises from a leptonic observable. We calculate the contribution of CP-odd Higgs couplings to the bottom and charm quarks in renormalisation-group improved perturbation theory at next-to-leading order in the strong interaction, thereby reducing the uncertainty to a few percent.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Evidence of the singly Cabibbo suppressed decay Λ c + → p π 0
Evidence for the singly Cabibbo suppressed decay Λ c + → p π 0 is reported for the first time with a statistical significance of 3.7 σ based on 6.0 fb − 1 of e + e − collision data collected at center-of-mass energies between 4.600 and 4.843 GeV with the BESIII detector at the BEPCII collider. The absolute branching fraction of Λ c + → p π 0 is measured to be ( 1.5 6 − 0.58 + 0.72 ± 0.20 ) × 10 − 4 . Combining with the branching fraction of Λ c + → n π + , ( 6.6 ± 1.3 ) × 10 − 4 , the ratio of the branching fractions of Λ c + → n π + and Λ c + → p π 0 is calculated to be 3.2 − 1.2 + 2.2 . As an important input for the theoretical models describing the decay mechanisms of charmed baryons, our result indicates that the nonfactorizable contributions play an essential role and their interference with the factorizable contributions should not be significant. In addition, the absolute branching fraction of Λ c + → p η is measured to be ( 1.63 ± 0.3 1 stat ± 0.1 1 syst ) × 10 − 3 . Published by the American Physical Society 2024
Astronomy & Astrophysics↗
The Experimental Programs on Light Pseudoscalar Meson Decays
The decays of the low-lying pseudoscalar mesons (?0, ?, and ??) allow access to a plethora of physics probes, from measurements of fundamental properties of matter such as the up-down quark mass ratio, to studies of channels that access higher-order terms in Chiral Perturbation theory, to tests of fundamental symmetries and searches for signatures of physics beyond the Standard Model. Several experiments have studied pseudoscalar decays: these experiments include PrimEx in Hall B at Jefferson Lab, A2 at the MAMI electron accelerator facility, the KLOE-II experiment at the DA?NE ?-factory, WASA-at-COSY at the cooler synchrotron COSY storage ring, and BESIII at the Beijing charm factory. In Hall D at Jefferson Lab, PrimEx-eta uses the Primakoff process to measure the ? radiative width using the GlueX spectrometer. In the near future the Jefferson Lab Eta Factory (JEF) experiment will use the GlueX spectrometer with an upgraded forward calorimeter to study ?(?) decay channels with a focus on all-neutral final states. Finally, a proposal for a new experiment, ``Rare Eta Decays with a TPC for Optical Photons'' (REDTOP) utilizing a proton beam on fixed targets, is under development. Highlights from previous and ongoing experiments and plans for future experiments will be presented.
Taylor, Simon↗
Strong coupling constant and quark masses from lattice QCD
In this paper, we review lattice determinations of the charm- and bottom-quark masses and the strong coupling constant obtained by different methods. We explain how effective field theory approaches, such as Non-Relativistic QCD (NRQCD), potential Non-Relativistic QCD (pNRQCD), Heavy Quark Effective Theory (HQET) and Heavy Meson rooted All- Staggered Chiral Perturbation Theory (HMrASχPT) can help in these determinations. After critically reviewing different lattice results we determine lattice world averages for the strong coupling constant, $α_s(M_Z, N_f=5) = 0.11803^{+0.00047}_{–0.00068}$, as well as for the charm-quark mass, $m_c(m_c, N_f=4) = 1.2735(35)$ GeV, and the bottom-quark mass, $m_b(m_b, N_f=5) = 4.188(10)$ GeV. The above
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Position-space renormalization schemes for four-quark operators in HQET
Abstract X-space schemes are gauge-invariant, regulator-independent renormalization schemes that are defined by requiring position-space correlation functions of gauge-invariant operators to be equal to their noninteracting values at particular kinematic points. These schemes can be used to nonperturbatively renormalize composite operators in Lattice Quantum Chromodynamics (LQCD), and by computing matching coefficients between theX-space scheme and$$ \overline{\textrm{MS}} $$ MS ¯ in the dimensionally-regulated continuum, matrix elements calculated with LQCD can be converted to$$ \overline{\textrm{MS}} $$ MS ¯ -renormalized matrix elements. UsingX-space schemes for Heavy Quark Effective Theory (HQET) operators has the additional benefit that appropriate ratios of position-space correlation functions cancel the power-divergent static-quark self-energy of Lattice HQET nonperturbatively. This work presents theO(α S ) matching coefficients betweenX-space renormalized four-quark flavor-nonsinglet HQET operators relevant for the lifetimes of charm- and bottom-hadrons, and four-quark HQET operators relevant for mixing between neutral mesons containing a heavy quark, such asB−$$ \overline{B} $$ B ¯ mixing.
Physics↗
Flavor-changing light bosons with accidental longevity
We consider a model with a complex scalar field that couples to (e, μ) or (μ, τ) within the “longevity” window: [|m l 1 – m l 2 |, m l 1 + m l 2 ] in which l 1 and l 2 are the two different charged leptons. Within such a mass window, even a relatively large coupling (e.g. of the size commensurate with the current accuracy/discrepancy in the muon g – 2 experiment) leads to long lifetimes and macroscopic propagation distance between production and decay points. We propose to exploit several existing neutrino experiments and one future experiment to probe the parameter space of this model. For the μ – e sector, we exploit the muonium decay branching ratio and the production and decay sequence at the LSND experiment, excluding the parametric region suggested by g μ – 2 anomaly. For the τ – μ sector, we analyze three main production mechanisms of scalars at beam dump experiments: the Drell-Yan process, the heavy meson decay, and the muon scattering. We explore the constraints from the past CHARM and NuTeV experiments, and evaluate sensitivity for the proposed beam dump experiment, SHiP. The latter can thoroughly probe the parameter space relevant for the g μ – 2 anomaly.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Thermal energy of a charm-meson molecule in a pion gas
The thermal corrections to the propagator of a loosely bound charm-meson molecule in a pion gas are calculated to next-to-leading order in the heavy-meson expansion using a zero-range effective field theory. Ultraviolet divergences in the charm-meson-pair self energy are canceled by corrections to the charm-meson-pair contact vertex. Terms that are singular at the charm-meson-pair threshold can be absorbed into thermal corrections to the rest energies and kinetic masses of the charm-meson constituents. The remaining terms reduce to a thermal correction to the binding momentum that is proportional to the pion number density and suppressed by the pion/charm-meson mass ratio. The correction gives a tiny decrease in the binding energy of the charm-meson molecule relative to the charm-meson-pair threshold in the pion gas and a change in its thermal width that is small compared to the thermal widths of the charm-meson constituents. These results are encouraging for the prospects of observing X(3872) and $T$$^{+}_{cc}$ (3875) in the expanding hadron gas produced by heavy-ion collisions.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗