We present a precise lattice computation of pseudoscalar and vector heavy-light meson masses for heavy-quark masses ranging from the physical charm mass up to ≃4 times the physical b-quark mass. We ...employ the gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with Nf=2+1+1 dynamical quarks at three values of the lattice spacing (a≃0.062,0.082,0.089 fm) with pion masses in the range Mπ≃210–450 MeV. The heavy-quark mass is simulated directly on the lattice up to ≃3 times the physical charm mass. The interpolation to the physical b-quark mass is performed using the ETMC ratio method, based on ratios of the meson masses computed at nearby heavy-quark masses, and adopting the kinetic mass scheme. The extrapolation to the physical pion mass and to the continuum limit yields mbkin(1 GeV)=4.61(20) GeV, which corresponds to m¯b(m¯b)=4.26(18) GeV in the MS¯ scheme. The lattice data are analyzed in terms of the heavy-quark expansion (HQE) and the matrix elements of dimension-four and dimension-five operators are extracted with a good precision, namely, Λ¯=0.552(26) GeV, μπ2=0.321(32) GeV2, and μG2(mb)=0.253(25) GeV2. The data also allow for a rough estimate of the dimension-six operator matrix elements. As the HQE parameters play a crucial role in the inclusive determination of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb, their precise determination on the lattice may eventually validate and improve the analyses based on fits to the semileptonic moments.
We present a lattice calculation of the leading-order electromagnetic and strong isospin-breaking corrections to the hadronic vacuum polarization (HVP) contribution to the anomalous magnetic moment ...of the muon. We employ the gauge configurations generated by the European Twisted Mass Collaboration with Nf = 2 + 1 + 1 dynamical quarks at three values of the lattice spacing (a≃0.062,0.082,0.089 fm) with pion masses between ≃210 and ≃450 MeV. The results are obtained by adopting the RM123 approach in the quenched-QED approximation, which neglects the charges of the sea quarks. Quark disconnected diagrams are not included. After the extrapolations to the physical pion mass and to the continuum and infinite-volume limits the contributions of the light, strange, and charm quarks are, respectively, equal to δaμHVP(ud)=7.1(2.5)×10−10, δaμHVP(s)=−0.0053(33)×10−10, and δaμHVP(c)=0.0182(36)×10−10. At leading order in αem and (md−mu)/ΛQCD we obtain δaμHVP(udsc)=7.1(2.9)×10−10, which is currently the most accurate determination of the isospin-breaking corrections to aμHVP.
We present a lattice calculation of the leading hadronic vacuum polarization (HVP) contribution of the light u- and d-quarks to the anomalous magnetic moment of the muon, aHVPμ (ud), adopting the ...gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with Nf = 2 + 1 + 1 dynamical quarks at three values of the lattice spacing (a ≃ 0.062, 0.082, 0.089 fm) with pion masses in the range Mπ ≃ 210–450 MeV. Thanks to several lattices at fixed values of the light-quark mass and scale but with different sizes we perform a careful investigation of finite-volume effects (FVEs), which represent one of main source of uncertainty in modern lattice calculations of aHVPμ (ud). In order to remove FVEs we develop an analytic representation of the vector correlator, which describes the lattice data for time distances larger than ≃ 0.2 fm. The representation is based on quark-hadron duality at small and intermediate time distances and on the two-pion contributions in a finite box at larger time distances. After removing FVEs we extrapolate the corrected lattice data to the physical pion point and to the continuum limit taking into account the chiral logs predicted by Chiral Perturbation Theory (ChPT). We obtain aHVPμ (ud) = 619.0 (17.8) × 10−10. Adding the contribution of strange and charm quarks, obtained by ETMC, and an estimate of the isospin-breaking corrections and quark-disconnected diagrams from the literature we get aHVPμ (udsc) = 683 (19) × 10−10, which is consistent with recent results based on dispersive analyses of the experimental cross section data for e+e− annihilation into hadrons. Using our analytic representation of the vector correlator, taken at the physical pion mass in the continuum and infinite volume limits, we provide the first eleven moments of the polarization function and we compare them with recent results of the dispersive analysis of the π+π− channels. We estimate also the light-quark contribution to the missing part of aHVPμ not covered in the MUonE experiment.
In this work we apply the Dispersive Matrix (DM) method of Di Carlo et al. (Phys Rev D 104:054502, 2021) and Martinelli et al. (Phys Rev D 105:034503, 2022) to the lattice computations of the Form ...Factors (FFs) entering the semileptonic
B
→
D
∗
ℓ
ν
ℓ
decays, recently produced by the FNAL/MILC Collaborations (Fermilab Lattice, MILC collaboration, Semileptonic form factors for
B
→
D
∗
ℓ
ν
at nonzero recoil from 2 + 1-flavor lattice QCD.
arXiv:2105.14019
) at small, but non-vanishing values of the recoil variable (
w
-
1
). Thanks to the DM method we obtain the FFs in the whole kinematical range accessible to the decay in a completely model-independent and non-perturbative way, implementing exactly both unitarity and kinematical constraints. Using our theoretical bands of the FFs we extract
|
V
cb
|
from the experimental data and compute the theoretical value of
R
(
D
∗
)
. Our final result for
|
V
cb
|
reads
|
V
cb
|
=
(
41.3
±
1.7
)
·
10
-
3
, compatible with the most recent inclusive estimate at the
0.5
σ
level. Moreover, we obtain the pure theoretical value
R
(
D
∗
)
=
0.275
±
0.008
, which is compatible with the experimental world average at the
∼
1.3
σ
level.
FLAG Review 2021 Aoki, Y.; Blum, T.; Colangelo, G. ...
The European physical journal. C, Particles and fields,
10/2022, Volume:
82, Issue:
10
Journal Article
Peer reviewed
Open access
We review lattice results related to pion, kaon,
D
-meson,
B
-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More ...specifically, we report on the determination of the light-quark masses, the form factor
f
+
(
0
)
arising in the semileptonic
K
→
π
transition at zero momentum transfer, as well as the decay constant ratio
f
K
/
f
π
and its consequences for the CKM matrix elements
V
us
and
V
ud
. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of
S
U
(
2
)
L
×
S
U
(
2
)
R
and
S
U
(
3
)
L
×
S
U
(
3
)
R
Chiral Perturbation Theory. We review the determination of the
B
K
parameter of neutral kaon mixing as well as the additional four
B
parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for
m
c
and
m
b
as well as those for the decay constants, form factors, and mixing parameters of charmed and bottom mesons and baryons. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant
α
s
. We consider nucleon matrix elements, and review the determinations of the axial, scalar and tensor bilinears, both isovector and flavor diagonal. Finally, in this review we have added a new section reviewing determinations of scale-setting quantities.
The leading-order electromagnetic and strong isospin-breaking corrections to the ratio of K_{μ2} and π_{μ2} decay rates are evaluated for the first time on the lattice, following a method recently ...proposed. The lattice results are obtained using the gauge ensembles produced by the European Twisted Mass Collaboration with N_{f}=2+1+1 dynamical quarks. Systematic effects are evaluated and the impact of the quenched QED approximation is estimated. Our result for the correction to the tree-level K_{μ2}/π_{μ2} decay ratio is -1.22(16)%, to be compared to the estimate of -1.12(21)% based on chiral perturbation theory and adopted by the Particle Data Group.
FLAG Review 2019 Aoki, S; Aoki, Y; Bečirević, D ...
The European physical journal. C, Particles and fields,
02/2020, Volume:
80, Issue:
2
Journal Article
Peer reviewed
Open access
We review lattice results related to pion, kaon, D-meson, B-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More ...specifically, we report on the determination of the light-quark masses, the form factor f+(0) arising in the semileptonic K→π transition at zero momentum transfer, as well as the decay constant ratio fK/fπ and its consequences for the CKM matrix elements Vus and Vud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2)L×SU(2)R and SU(3)L×SU(3)R Chiral Perturbation Theory. We review the determination of the BK parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for mc and mb as well as those for D- and B-meson decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant αs. Finally, in this review we have added a new section reviewing results for nucleon matrix elements of the axial, scalar and tensor bilinears, both isovector and flavor diagonal.
We present a lattice calculation of the masses and decay constants of D(s)* and B(s)* mesons using the gauge configurations produced by the European Twisted Mass Collaboration (ETMC) with Nf=2+1+1 ...dynamical quarks at three values of the lattice spacing a∼(0.06−0.09) fm. Pion masses are simulated in the range Mπ≃(210–450) MeV, while the strange and charm sea-quark masses are close to their physical values. We compute the ratios of vector to pseudoscalar masses and decay constants for various values of the heavy-quark mass mh in the range 0.7mcphys≲mh≲3mcphys. In order to reach the physical b-quark mass, we exploit the heavy quark effective theory prediction that, in the static limit of infinite heavy-quark mass, the considered ratios are equal to one. At the physical point our results are MD*/MD=1.0769(79), MDs*/MDs=1.0751(56), fD*/fD=1.078(36), fDs*/fDs=1.087(20), MB*/MB=1.0078(15), MBs*/MBs=1.0083(10), fB*/fB=0.958(22) and fBs*/fBs=0.974(10). Combining them with the experimental values of the pseudoscalar meson masses (used as input to fix the quark masses) and the values of the pseudoscalar decay constants calculated by ETMC, we get MD*=2013(14), MDs*=2116(11), fD*=223.5(8.4), fDs*=268.8(6.6), MB*=5320.5(7.6), MBs*=5411.36(5.3), fB*=185.9(7.2) and fBs*=223.1(5.4) MeV.
The ratios among the leading-order (LO) hadronic vacuum polarization (HVP) contributions to the anomalous magnetic moments of an electron, muon, and τ lepton, aHVP,LOℓ=e,μ,τ, are computed using ...lattice QCD + QED simulations. The results include the effects at order O(α2em) as well as the electromagnetic and strong isospin-breaking corrections at orders O(α3em) and O(α2em (mu − md)), respectively, where (mu − md) is the u - and d -quark mass difference. We employ the gauge configurations generated by the Extended Twisted Mass Collaboration with Nf = 2 + 1 + 1 dynamical quarks at three values of the lattice spacing (a ≃ 0.062, 0.082, 0.089 fm) with pion masses in the range ≃ 210 – 450 MeV . The calculations are based on the quark-connected contributions to the HVP in the quenched-QED approximation, which neglects the charges of the sea quarks. The quark-disconnected terms are estimated from results available in the literature. We show that in the case of the electron-muon ratio the hadronic uncertainties in the numerator and in the denominator largely cancel out, while in the cases of the electron- τ and muon- τ ratios such a cancellation does not occur. For the electron-muon ratio we get Re/μ ≡ (mμ / me)2 (aHVP,LOe / aHVP,LOμ) = 1.1456 (83) with an uncertainty of ≃ 0.7 % . Our result, which represents an accurate Standard Model (SM) prediction, agrees very well with the estimate obtained using the results of dispersive analyses of the experimental e+ e− → hadrons data. Instead, it differs by ≃ 2.7 standard deviations from the value expected from present electron and muon (g − 2) experiments after subtraction of the current estimates of the QED, electroweak, hadronic light-by-light and higher-order HVP contributions, namely Re/μ = 0.575 (213) . An improvement of the precision of both the experiment and the QED contribution to the electron (g − 2) by a factor of ≃ 2 could be sufficient to reach a tension with our SM value of the ratio R e / μ at a significance level of ≃ 5 standard deviations.
We present a nonperturbative lattice calculation of the form factors which contribute to the amplitudes for the radiative decays P → ℓνℓγ, where P is a pseudoscalar meson and ℓ is a charged lepton. ...Together with the nonperturbative determination of the corrections to the processes P → ℓνℓ due to the exchange of a virtual photon, this allows accurate predictions at O(αem) to be made for leptonic decay rates for pseudoscalar mesons ranging from the pion to the Ds meson. We are able to separate unambiguously and nonpertubatively the pointlike contribution, from the structure-dependent, infrared-safe, terms in the amplitude. The fully nonperturbative O(a) improved calculation of the inclusive leptonic decay rates will lead to the determination of the corresponding Cabibbo-Kobayashi-Maskawa matrix elements also at O(αem). Prospects for a precise evaluation of leptonic decay rates with emission of a hard photon are also very interesting, especially for the decays of heavy D and B mesons for which currently only model-dependent predictions are available to compare with existing experimental data.
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