Lattice calculation of the short and intermediate time-distance hadronic vacuum polarization contributions to the muon magnetic moment using twisted-mass fermions

Abstract

We present a lattice determination of the leading-order hadronic vacuum polarization (HVP) contribution to the muon anomalous magnetic moment, aμHVP, in the so-called short and intermediate time-distance windows, aμSD and aμW, defined by the RBC/UKQCD Collaboration [Phys. Rev. Lett. 121, 022003 (2018)PRLTAO0031-900710.1103/PhysRevLett.121.022003]. We employ gauge ensembles produced by the Extended Twisted Mass Collaboration (ETMC) with Nf=2+1+1 flavors of Wilson-clover twisted-mass quarks with masses of all the dynamical quark flavors tuned close to their physical values. The simulations are carried out at three values of the lattice spacing equal to ≃0.057, 0.068 and 0.080 fm with spatial lattice sizes up to L≃7.6 fm. For the short-distance window we obtain aμSD(ETMC)=69.27(34)×10-10, which is consistent with the recent dispersive value of aμSD(e+e-)=68.4(5)×10-10 [Colangelo, Phys. Lett. B 833, 137313 (2022)PYLBAJ0370-269310.1016/j.physletb.2022.137313]. In the case of the intermediate window we get the value aμW(ETMC)=236.3(1.3)×10-10, which is consistent with the result aμW(BMW)=236.7(1.4)×10-10 [Borsanyi, Nature (London) 593, 51 (2021)NATUAS0028-083610.1038/s41586-021-03418-1] by the BMW Collaboration as well as with the recent determination by the CLS/Mainz group of aμW(CLS)=237.30(1.46)×10-10 [Cè, Phys. Rev. D 106, 114502 (2022)PRVDAQ2470-001010.1103/PhysRevD.106.114502]. However, it is larger than the dispersive result of aμW(e+e-)=229.4(1.4)×10-10 by approximately 3.6 standard deviations. The tension increases to approximately 4.5 standard deviations if we average our ETMC result with those by BMW and CLS/Mainz. Our accurate lattice results in the short and intermediate windows point to a possible deviation of the e+e- cross section data with respect to Standard Model predictions in the low- and intermediate-energy regions but not in the high-energy region.