Conveners
Weak Decays and Matrix Elements
- Stefan Meinel (University of Arizona / RIKEN BNL Research Center)
Weak Decays and Matrix Elements
- Takashi Kaneko (KEK)
Weak Decays and Matrix Elements
- Chris Bouchard (William and Mary)
Weak Decays and Matrix Elements
- Antonin Portelli (The University of Edinburgh)
Weak Decays and Matrix Elements
- Christopher Kelly (Columbia University)
Weak Decays and Matrix Elements
- Andrew Lytle (University of Glasgow)
We present a proposal to compute on the lattice $B \to \pi$ form factors in the full momentum range. We also discuss some new results for the $B \to D,D^*$ semileptonic form factors.
We present nearly final results from our analysis of the form factors for $B \to D^\ast\ell\nu$ decay at nonzero recoil. Our analysis includes 15 MILC asqtad ensembles with $N_f$=2+1 flavors of sea quarks and lattice spacings ranging from $a\approx$ 0.15 fm down to 0.045 fm. The valence light quarks employ the asqtad action, whereas The b and c quarks are treated using the Fermilab action. We...
We report on our calculation of the $B \to D^{(*)}\ell\nu$ form factors
in 2+1 flavor lattice QCD. The Moebius domain-wall action is employed
for light, strange, charm and bottom quarks. At lattice cut-offs
$a^{-1} \sim $ 2.4, 3.6 and 4.5 GeV, we simulate bottom quark masses
up to 0.8 $a^{-1}$ to control discretization errors. The pion mass
is as low as 230 MeV. We discuss the heavy quark...
We present results of the first lattice QCD calculation of $B_c \rightarrow B_s$ and $B_c \rightarrow B_d$ vector matrix elements with 4-momentum transfer across the entire physical range. Form factors are then extracted and combined with CKM matrix elements to predict the decay rates for $B_c^+ \rightarrow B_s^0 \overline{l} \nu_l$ and $B_c^+ \rightarrow B^0 \overline{l} \nu_l$. Results are...
We present our exploratory study with the aim of simulating heavy-light semileptonics as part of the RBC-UKQCD charm (to bottom) physics programme. We are using a distillation-based setup as a strategy to get optimised plateaus in semi-leptonic $D_{(s)}$ and $B_{(s)}$ decays. The study will be done in a centre-of-mass frame and several moving frames and will use an $N_f=2+1$ domain wall...
We report on the JLQCD Collaboration's calculation of form factors for the exclusive semileptonic decay of $B$ meson to pion on $2+1$-flavour lattices with lattice spacings from 0.080 fm down to 0.044 fm. Using the Möbius domain wall fermion action for both sea and valence quarks, we simulate pions with masses down to 230 MeV. By utilizing a range of heavy quark masses up to 2.44 times the...
This talk will focus on RBC/UKQCD's most recent analysis for $B \rightarrow \pi l \nu$ and $B \rightarrow D l \nu$ semileptonic form factors. Heavy quarks have been simulated with the Columbia formulation of the relativistic heavy quark (RHQ) action, and light quarks with a domain-wall fermion action. The decays have been investigated over six ensembles. The form factor dependence on the...
We report updates to an ongoing lattice-QCD calculation of the form factors for the semileptonic decays $B \to \pi \ell \nu$, $B_s \to K \ell \nu$, $B \to \pi \ell^+ \ell^-$, and $B \to K \ell^+ \ell^-$. The tree-level decays $B_{(s)} \to \pi (K) \ell \nu$ enable precise determinations of the CKM matrix element $|V_{ub}|$, while the flavor-changing neutral-current interactions $B \to...
Form factors and related phenomenology for the $B \to \pi \ell \nu$ and $B \to \pi \ell \ell$ decays will be presented. The simulations use HISQ light and NRQCD $b$ valence quarks on the MILC $N_f = 2 + 1$ asqtad ensembles, with pion momenta covering the full kinematic range for the decays. Large pion momenta (up to 2.6 GeV) data are analyzed via the hard pion ChPT motivated modified...
The form factors in the semileptonic decays of heavy $B/D$ meson decays can be represented by dispersion relations, by which the kinematics in the decay region are related to the ones in the scattering region. By fitting to the lattice QCD data on the form factors, the subtraction constants in their dispersive representations can be determined such that the form factors in the whole...
We analyze the inclusive semi-leptonic $B \to X_c \ell\nu$ structure
functions in 2+1-flavor lattice QCD. The M\"obius domain-wall fermion action is used for light, strange, charm and bottom quarks. The structure function receives contributions from various exclusive modes, including the dominant S-wave states $D^{(*)}_s$ as well as the P-wave states $D_s^{**}$. We can identify them in the...
We calculate the amplitude of $B \to K l^+l^-$ through the charmonium intermediate state.
It may give a significant contribution near the charmonium resonances.
Away from the resonances, one needs a reliable theoretical estimate for the search of potential new physics, and our lattice calculation provides a test of the factorization approximation, which has been used in previous...
Adding a hard photon to the final state of a leptonic pseudoscalar-meson decay lifts the helicity suppression and can provide sensitivity to a larger set of operators in the weak effective Hamiltonian. Furthermore, radiative leptonic B decays at high photon energy are well suited to constrain the first inverse moment of the B-meson light-cone distribution amplitude, an important parameter in...
In this talk we will give a brief review of our recent computation of ratios of decay constants and neutral meson mixing parameters for $B_{(s)}$ and $D_{(s)}$ mesons (1812.08791).
We will present our efforts to extend this calculation to the individual decay constants and bag parameters and outline the wider heavy flavour physics Domain Wall Fermion program.
We present a lattice QCD calculation of both scalar and vector form factors associated with the D→Klν semileptonic decay over full range of $q^2$. We extract the central CKM matrix element, $V_{cs}$ in the Standard Model, by comparing the lattice QCD results for the form factors and the experimental decay rates. This calculation has been performed on the $N_f=2+1+1$ MILC HISQ ensembles...
We present our results of the $K_{l3}$ form factors on the volume of configuration more than $L=$10 fm, with the physical pion and kaon masses using the stout-smearing clover $N_f = 2+1$ quark action and Iwasaki gauge action at $a^{-1}=2.333$ GeV.
The $K_{l3}$ form factor at zero momentum transfer is obtained from fit results using the NLO formula in SU(3) chiral perturbation theory with NNLO...
The rare second-order weak decay $K_L \to \mu^+\mu^-$ is precisely measured and sensitive to the structure of the weak interactions at short distances. However, these effects are obscured by a large third-order, long-distance contribution to this decay in which the muon pair is created by two photons. We will discuss the prospects for computing this third-order electroweak process using...
The important $K_L\rightarrow \mu^+ \mu^-$ decay is complicated by the presence of intermediate states with the same or lower energy than the mass of kaon. To address one of these intermediate states, the two-particle $\gamma\gamma$ state, it is useful to work on a simpler problem which offers the same difficulty --- the $\pi^0 \rightarrow e^+ e^-$ decay. We hope to present preliminary...
We present a lattice procedure to calculate the leptonic pion decay width with only exponentially-suppressed finite-volume errors using the infinite-volume reconstruction method. Three technical points: 1) the inclusion of pion wave function renormalization factor, 2) the cancellation of infared divergence and 3) the connection between Euclidean-space correlation function and the relevant...
During the last few years we have developed the theoretical framework for including radiative corrections to lattice computations of the $\pi_{\ell 2}$ and $K_{\ell 2}$ leptonic decay rates and performed the corresponding numerical calculations. This necessarily includes the treatment of infrared divergences. In this talk we discuss the extension of this framework to semileptonic decays, such...
When calculating isospin-breaking corrections to hadronic quantities, sea quark effects are often neglected. In this work by the RBC/UKQCD collaboration, based on their domain-wall fermion ensembles combined with an all-to-all approach, we discuss our strategy for computing the disconnected isospin-breaking contributions to light pseudo-scalar meson masses and matrix elements. We will present...
In this talk we present the status of the RBC-UKQCD collaboration project to compute the QED corrections to light pseudo-scalar leptonic decay rates. This computation is using domain-wall fermions at close-to-physical quark masses. We summarise the overall strategy to obtain the relevant amplitude corrections from Euclidean correlation functions. These correlations functions are assembled...
We will present the status of our calculation of the difference between the masses of the long- and short-lived neutral K mesons, $\Delta m_K$, predicted by the Standard Model. This calculation is performed on an ensemble of 152, $64^3 \times 128$ gauge configurations with an inverse lattice spacing of 2.36 GeV and physical quark masses. The results from different methods of analysis and our...
The pi-pi scattering phase shifts for both the s-wave I=0 and I=2 channels are determined from a lattice calculation performed on 741 gauge configurations obeying G-parity boundary conditions with a physical pion mass. The phase shifts are determined for both stationary and moving pi-pi systems, at four different center of mass momenta. We implement three interpolating operators including a...
We provide an update on the RBC & UKQCD lattice calculation of the measure of Standard Model direct CP-violation in kaon decays, \epsilon'.
Recently LHCb announced a 5-sigma exciting observation of direct CP in D0 decays to KK/pipi. Computations of direct CP remain an outstanding important challenge for theory for a variety of fundamental reasons. Here a rough estimate of the observed size of the asymmetry will be explained. Although 1st principle calculations of direct CP in D^0 to KK/pi pi cannot be done by known lattice...
