perturbation theory: chiral

$B_s$ to $K \ell \nu$ decay from lattice QCD

We use lattice QCD to calculate the form factors f+(q2) and f0(q2) for the semileptonic decay Bs→Kℓν. Our calculation uses six MILC asqtad 2+1 flavor gauge-field ensembles with three lattice spacings. At the smallest and largest lattice spacing the …

$|V_{us}|$ from $K_{\ell 3}$ decay and four-flavor lattice QCD

Using highly improved staggered quark (HISQ) Nf=2+1+1 MILC ensembles with five different values of the lattice spacing, including four ensembles with physical quark masses, we perform the most precise computation to date of the K→πℓν vector form …

Up-, down-, strange-, charm-, and bottom-quark masses from four-flavor lattice QCD

We calculate the up-, down-, strange-, charm-, and bottom-quark masses using the MILC highly improved staggered-quark ensembles with four flavors of dynamical quarks. We use ensembles at six lattice spacings ranging from a≈0.15 to 0.03 fm and with …

Spectroscopy of SU(4) composite Higgs theory with two distinct fermion representations

We have simulated the SU(4) lattice gauge theory coupled to dynamical fermions in the fundamental and two-index antisymmetric (sextet) representations simultaneously. Such theories arise naturally in the context of composite Higgs models that include …

One-loop Chiral Perturbation Theory with two fermion representations

We develop chiral perturbation theory for chirally broken theories with fermions in two different representations of the gauge group. Any such theory has a nonanomalous singlet U(1)A symmetry, yielding an additional Nambu-Goldstone boson when …

$Btextasciicircum0_(s)$-mixing matrix elements from lattice QCD for the Standard Model and beyond

We calculate—for the first time in three-flavor lattice QCD—the hadronic matrix elements of all five local operators that contribute to neutral B0- and Bs-meson mixing in and beyond the Standard Model. We present a complete error budget for each …

B→Dℓν form factors at nonzero recoil and textbarV$_b̧$textbar from 2+1-flavor lattice QCD

We present the first unquenched lattice-QCD calculation of the hadronic form factors for the exclusive decay B¯→Dℓν¯ at nonzero recoil. We carry out numerical simulations on 14 ensembles of gauge-field configurations generated with 2+1 flavors of …

$textbarV_ubtextbar$ from $Btopiellnu$ decays and (2+1)-flavor lattice QCD

We present a lattice-QCD calculation of the B→πℓν semileptonic form factors and a new determination of the CKM matrix element textbarVubtextbar. We use the MILC asqtad (2+1)-flavor lattice configurations at four lattice spacings and light-quark …

Determination of $textbarV_ustextbar$ from a Lattice-QCD Calculation of the $Ktopiellnu$ Semileptonic Form Factor with Physical Quark Masses

We calculate the kaon semileptonic form factor $f_+(0)$ from lattice QCD, working, for the first time, at the physical light-quark masses. We use gauge configurations generated by the MILC collaboration with $N_f=2+1+1$ flavors of sea quarks, which …

Kaon semileptonic vector form factor and determination of textbarV_ustextbar using staggered fermions

Using staggered fermions and twisted boundary conditions, we calculate the K meson semileptonic decay vector form factor at zero momentum transfer. The HISQ formulation is used for the valence quarks, while the sea quarks are simulated with the …