0000000000281657
AUTHOR
Christopher T. Sachrajda
An exploratory lattice study of Delta I=3/2 K ->pi pi decays at next-to-leading order in the chiral expansion
We present the first direct evaluation of Delta I = 3/2K -> pi pi matrix elements with the aim of determining all the low-energy constants at NLO in the chiral expansion. Our numerical investigation demonstrates that it is indeed possible to determine the K -> pi pi matrix elements directly for the masses and momenta used in the simulation with good precision. In this range however, we find that the matrix elements do not satisfy the predictions of NLO chiral perturbation theory. For the chiral extrapolation we therefore use a hybrid procedure which combines the observed polynomial behavior in masses and momenta of our lattice results, with NLO chiral perturbation theory at lower masses. In…
First lattice calculation of the B-meson binding and kinetic energies
We present the first lattice calculation of the B-meson binding energy $\labar$ and of the kinetic energy $-\lambda_1/2 m_Q$ of the heavy-quark inside the pseudoscalar B-meson. This calculation has required the non-perturbative subtraction of the power divergences present in matrix elements of the Lagrangian operator $\bar h D_4 h$ and of the kinetic energy operator $\bar h \vec D^2 h$. The non-perturbative renormalisation of the relevant operators has been implemented by imposing suitable renormalisation conditions on quark matrix elements, in the Landau gauge. Our numerical results have been obtained from several independent numerical simulations at $\beta=6.0$ and $6.2$, and using, for t…
Review of Particle Properties
This biennial Review summarizes much of Particle Physics. Using data from previous editions, plus 2205 new measurements from 667 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. This edition features expanded coverage of CP violation in B mesons and of neutrino oscillations. For the fir…
‘‘Improved’’ lattice study of semileptonic decays ofDmesons
We present results of a lattice computation of the matrix elements of the vector and axial-vector currents which are relevant for the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$. The computations are performed in the quenched approximation to lattice QCD on a $24^3 \times 48$ lattice at $\beta=6.2$, using an $O(a)$-improved fermionic action. In the limit of zero lepton masses the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$ are described by four form factors: $f^{+}_K,V,A_1$ and $A_2$, which are functions of $q^2$, where $q^{\mu}$ is the four-momentum transferred in the process. Our results for these form factors at $q^2=0$ are: $f^+_K(0)=0.67 \er{7}{8}$…
The Isgur-Wise function from the lattice
We calculate the Isgur-Wise function by measuring the elastic scattering amplitude of a $D$ meson in the quenched approximation on a $24^3\times48$ lattice at $\beta=6.2$, using an $O(a)$-improved fermion action. Fitting the resulting chirally-extrapolated Isgur-Wise function to Stech's relativistic-oscillator parametrization, we obtain a slope parameter $\rho^2=1.2+7-3. We then use this result, in conjunction with heavy-quark symmetry, to extract $V_{cb}$\ from the experimentally measured $\bar B\to D^*l\bar\nu\,$\ differential decay width. We find $|V_{cb}|\sqrt{\tau_B/1.48{\mathrm ps}}= 0.038 +2-2 +8-3, where the first set of errors is due to experimental uncertainties, while the second …
Matrix elements of Delta I=3/2 K ->pi pi decays
We present a numerical computation of matrix elements of DeltaI = 3/2 K --> pipi decays by using Wilson fermions. In order to extrapolate to the physical point we work at unphysical kinematics and we resort to Chiral Perturbation Theory at the next-to-leading order. In particular we explain the case of the electroweak penguins O-7,O-8 which can contribute significantly in the theoretical prediction of epsilon'/epsilon. The study is done at beta = 6.0 on a 24(3) x 64 lattice.
Lattice study of semileptonic b-decays - (b)over-bar-]dl(nu)over-bar decays
We present a study of semileptonic ($) over bar B --> Dl ($) over bar v decays in quenched lattice QCD through a calculation of the matrix element [D\($) over bar c gamma(mu)b\($) over bar B] on a 24(3) x 48 lattice at beta = 6.2, using an O(alpha)-improved fermion action. We perform the calculation for several values of the initial and final heavy-quark masses around the charm mass, and three values of the light-(anti)quark mass around the strange mass. Because the charm quark has a bare mass which is almost 1/3 the inverse lattice spacing, we study the ensuing mass-dependent discretization errors, and propose a procedure for subtracting at least some of them nonperturbatively. We extract …
Kaon weak matrix elements with Wilson fermions
We present results of several numerical studies with Wilson fermions relevant for kaon physics. We compute the B_K parameter by using two different methods and extrapolate to the continuum limit. Our preliminary result is B_K(2 GeV)=0.66(7). Delta I=3/2 K->pi pi matrix elements are obtained by using the next-to-leading order expressions derived in chiral perturbation theory in which the low energy constants are determined by the lattice results computed at unphysical kinematics. From the simulation at beta=6.0 our (preliminary) results read: _{I=2}=0.14(1)(1) GeV^3 and _{I=2}=0.69(6)(6) GeV^3.
An exploratory lattice study of decays at next-to-leading order in the chiral expansion
Abstract We present the first direct evaluation of Δ I = 3 / 2 K → π π matrix elements with the aim of determining all the low-energy constants at NLO in the chiral expansion. Our numerical investigation demonstrates that it is indeed possible to determine the K → π π matrix elements directly for the masses and momenta used in the simulation with good precision. In this range however, we find that the matrix elements do not satisfy the predictions of NLO chiral perturbation theory. For the chiral extrapolation we therefore use a hybrid procedure which combines the observed polynomial behavior in masses and momenta of our lattice results, with NLO chiral perturbation theory at lower masses. …
Kl3Semileptonic Form Factor from (2+1)-Flavor Lattice QCD
We present the first results for the ${K}_{l3}$ form factor from simulations with $2+1$ flavors of dynamical domain wall quarks. Combining our result, namely, ${f}_{+}(0)=0.964(5)$ with the latest experimental results for ${K}_{l3}$ decays leads to $|{V}_{us}|=0.2249(14)$, reducing the uncertaintity in this important parameter. For the $O({p}^{6})$ term in the chiral expansion we obtain $\ensuremath{\Delta}f=\ensuremath{-}0.013(5)$.
Kl3form factor withNf= 2 +1 dynamical domain wall fermions
We present the latest results from the UKQCD/RBC collaborations for the Kl3 form factor from simulations with 2 + 1 flavours of dynamical domain wall quarks. Simulations are performed on lattices with two different volumes and four values of the light quark mass, allowing for an extrapolation to the chiral limit. The analysis includes a thorough investigation into the sources of systematic error in our fits. After interpolating to zero momentum transfer, we obtain f+(0) = 0.964(5) (or ?f = -0.013(5)) which, when combined with the latest experimental results for Kl3 decays, leads to |Vus| = 0.2249(14).
First lattice study of semileptonic decays of Lambda(b) and Xi(b) baryons
We present the results of the first lattice study of semileptonic decays of baryons containing a b quark. Predictions for the decay distributions are given and the Isgur-Wise functions for heavy baryons are computed for values of the velocity transfer up to about omega = 1.2. The computations are performed on a 24(3) x 48 lattice at beta = 6.2 using the Sheikholeslami-Wohlert action in the quenched approximation.
A high statistics lattice calculation of the B-meson binding energy
We present a high statistics lattice calculation of the B--meson binding energy $\overline{\Lambda}$ of the heavy--quark inside the pseudoscalar B--meson. Our numerical results have been obtained from several independent numerical simulations at $\beta=6.0$, $6.2$ and $6.4$, and using, for the meson correlators, the results obtained by the APE group at the same values of $\beta$. Our best estimate, obtained by combining results at different values of $\beta$, is $\overline{\Lambda}=180^{+30}_{-20}$ MeV. For the $\overline{MS}$ running mass, we obtain $\overline{m}_{b}(\overline{m}_{b})=4.15 \pm 0.05 \pm 0.20$ GeV, in reasonable agreement with previous determinations. The systematic error is…