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Inverse moment of the B -meson quasidistribution amplitude
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Transverse single-spin asymmetry of midrapidity π 0 and η mesons in p + Au and p + Al collisions at s N N = 200 GeV
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Timelike meson form factors beyond the elastic region from lattice QCD
We present a calculation of the vector-isovector timelike form factors of the pion and the kaon using lattice quantum chromodynamics. We calculate two-point correlation functions with m π ∼ 280 MeV , extracting both the finite-volume spectrum and matrix elements for these states created from the vacuum by a vector current. After determining the coupled-channel π π , K K ¯ scattering amplitudes, we perform the necessary correction for the significant finite-volume effects present in the current matrix elements, leading to the timelike form factors. We find these to be dominated by the presence of the ρ resonance, and we extract its decay constant by an analytic continuation of the amplitudes to the resonance pole. In addition, the spacelike pion form factor is determined on the same lattice configurations, and a dispersive parametrization is used to simultaneously describe the spacelike and elastic timelike regions. Published by the American Physical Society 2024
Observation of a New Excited D s + Meson in B 0 → D − D + K + π − Decays
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Analysis of Neutral B -Meson Decays into Two Muons
Branching fraction and effective lifetime measurements of the rare decay B s 0 → μ + μ - and searches for the decays B 0 → μ + μ - and B s 0 → μ + μ - γ are reported using proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a luminosity of 9 fb - 1 . The branching fraction B ( B s 0 → μ + μ - ) = ( 3.0 9 - 0.43 - 0.11 + 0.46 + 0.15 ) × 10 - 9 and the effective lifetime τ ( B s 0 → μ + μ - ) = 2.07 ± 0.29 ± 0.03 ps are measured, where the first uncertainty is statistical and the second systematic. No significant signal for B 0 → μ + μ - and B s 0 → μ + μ - γ decays is found and upper limits B ( B 0 → μ + μ - ) < 2.6 × 10 - 10 and B ( B s 0 → μ + μ - γ ) < 2.0 × 10 - 9 at the 95% C.L. are determined, where the latter is limited to the range m μ μ > 4.9 GeV / c 2 . The results are in agreement with the standard model expectations.
Dynamics and symmetries of nonleptonic hyperon decays - Scalar meson couplings.
Dynamics and symmetries of nonleptonic hyperon decay based on assumptions of parity-violating and parity-conserving amplitudes, inverse associated production amplitudes and SU SYMMETRY
Isospin-breaking corrections to light-meson leptonic decays from lattice simulations at physical quark masses
The decreasing uncertainties in theoretical predictions and experimental measurements of several hadronic observables related to weak processes, which in many cases are now smaller than O(1%), require theoretical calculations to include subleading corrections that were neglected so far. Precise determinations of leptonic and semi-leptonic decay rates, including QED and strong isospin-breaking effects, can play a central role in solving the current tensions in the first-row unitarity of the CKM matrix. In this work we present the first RBC/UKQCD lattice calculation of the isospin-breaking corrections to the ratio of leptonic decay rates of kaons and pions into muons and neutrinos. The calculation is performed at fixed lattice spacing (a –1 ≃ 1.730 GeV) on a 48 3 × 96 volume with N f = 2 + 1 dynamical quarks close to the physical point and domain wall fermions in the Möbius formulation are employed. Long-distance QED interactions are included according to the QED L prescription and the crucial role of finite-volume electromagnetic corrections in the determination of leptonic decay rates, which produce a large systematic uncertainty, is extensively discussed. Finally, we study the different sources of uncertainty on |V us |/|V ud | and observe that, if finite-volume systematics can be reduced, the error from isospin-breaking corrections is potentially sub-dominant in the final precision of the ratio of the CKM matrix elements.
Observation of CP violation in two-body $ {B}_{(s)}^0 $-meson decays to charged pions and kaons
The time-dependent CP asymmetries of B 0 → π + π – and $B$$^{0}_{s}$ → K + K – decays are measured using a data sample of $pp$ collisions corresponding to an integrated luminosity of 1.9 fb –1 , collected with the LHCb detector at a centre-of-mass energy of 13 TeV.
Measurements of the branching fraction ratio $$ \mathcal{B}\left(\phi \to {\mu}^{+}{\mu}^{-}\right)/\mathcal{B}\left(\phi \to {\textrm{e}}^{+}{\textrm{e}}^{-}\right) $$ with charm meson decays
Abstract Measurements of the branching fraction ratio$$ \mathcal{B}\left(\phi \to {\mu}^{+}{\mu}^{-}\right)/\mathcal{B}\left(\phi \to {e}^{+}{e}^{-}\right) $$ B ϕ → μ + μ − / B ϕ → e + e − with$$ {D}_s^{+}\to {\pi}^{+}\phi $$ D s + → π + ϕ andD + → π + ϕdecays, denoted$$ {R}_{\phi \pi}^s $$ R ϕπ s and$$ {R}_{\phi \pi}^d $$ R ϕπ d , are presented. The analysis is performed using a dataset corresponding to an integrated luminosity of 5.4 fb −1 ofppcollision data collected with the LHCb experiment. The branching fractions are normalised with respect to theB + →K + J/ψ(→e + e − ) andB + →K + J/ψ(→μ + μ − ) decay modes. The combination of the results yields$$ {R}_{\phi \pi}=1.022\pm 0.012\left(\textrm{stat}\right)\pm 0.048\left(\textrm{syst}\right). $$ R ϕπ = 1.022 ± 0.012 stat ± 0.048 syst . The result is compatible with previous measurements of theϕ→ℓ + ℓ − branching fractions and predictions based on the Standard Model.
Searches for 25 rare and forbidden decays of D + and ${D}_s^{+}$ mesons
A search is performed for rare and forbidden charm decays of the form ${D}_{(s)}^{+}\to {h}^{\pm }{\mathrm{\ell}}^{+}{\mathrm{\ell}}^{\left(\prime \right)\mp } $, where h ± is a pion or kaon and ℓ (')± is an electron or muon. The measurements are performed using proton-proton collision data, corresponding to an integrated luminosity of 1.6 fb –1 , collected by the LHCb experiment in 2016. No evidence is observed for the 25 decay modes that are investigated and 90 % confidence level limits on the branching fractions are set between 1.4 × 10 –8 and 6.4 × 10 –6 . In most cases, these results represent an improvement on existing limits by one to two orders of magnitude.
New method for calculating electromagnetic effects in semileptonic beta-decays of mesons
We construct several classes of hadronic matrix elements and relate them to the low-energy constants in Chiral Perturbation Theory that describe the electromagnetic effects in the semileptonic beta decay of the pion and the kaon. We propose to calculate them using lattice QCD, and argue that such a calculation will make an immediate impact to a number of interesting topics at the precision frontier, including the outstanding anomalies in |V us | and the top-row Cabibbo-Kobayashi-Maskawa matrix unitarity.
Energy dependence of coherent photonuclear production of J/ψ mesons in ultra-peripheral Pb-Pb collisions at $\sqrt{{\textrm{s}}_{\textrm{NN}}}$ = 5.02 TeV
The cross section for coherent photonuclear production of J/ψ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{{\textrm{s}}_{\textrm{NN}}}$ = 5.02 TeV. Cross sections are presented in five different J/ψ rapidity ranges within |y| < 4, with the J/ψ reconstructed via its dilepton decay channels. In some events the J/ψ is not accompanied by EMD, while other events do produce neutrons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range 17 < W γ Pb,n < 920 GeV, where W γ Pb,n is the centre-of-mass energy per nucleon of the γPb system. This range corresponds to a Bjorken-x interval spanning about three orders of magnitude: 1.1 × 10 —5 < x < 3.3 × 10 —2 . In addition to the ultra-peripheral and photonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energies.
Heavy meson tomography of cold nuclear matter at the electron-ion collider
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ϕ-meson lepto-production near threshold and the strangeness D-term
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Gluon saturation effects in exclusive heavy vector meson photoproduction
We study exclusive J/ψ and ϒ photoproduction for proton and Pb targets in the high-energy limit, with the energy dependence computed using the linear Balitsky–Fadin–Kuraev–Lipatov and the nonlinear Balitsky–Kovchegov evolution equations. The difference between these two evolution equations can be directly attributed to gluon saturation physics. We find that for proton targets there is no difference between the two approaches at the energies of the currently available data, while for Pb targets in J/ψ production the data shows a clear preference for the evolution with gluon saturation.
Ising meson spectroscopy on a noisy digital quantum simulator
Abstract Quantum simulation has the potential to be an indispensable technique for the investigation of non-perturbative phenomena in strongly-interacting quantum field theories (QFTs). In the modern quantum era, with Noisy Intermediate Scale Quantum (NISQ) simulators widely available and larger-scale quantum machines on the horizon, it is natural to ask: what non-perturbative QFT problems can be solved with the existing quantum hardware? We show that existing noisy quantum machines can be used to analyze the energy spectrum of several strongly-interacting 1+1D QFTs, which exhibit non-perturbative effects like ‘quark confinement’ and ‘false vacuum decay’. We perform quench experiments on IBM’s quantum simulators to compute the energy spectrum of 1+1D quantum Ising model with a longitudinal field. Our results demonstrate that digital quantum simulation in the NISQ era has the potential to be a viable alternative to numerical techniques such as density matrix renormalization group or the truncated conformal space methods for analyzing QFTs.