### Conveners

#### Weak Decays and Matrix Elements: 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

- Vittorio Lubicz

#### Weak Decays and Matrix Elements

- Nazario Tantalo (Rome University Tor Vergata and INFN sez. of Rome Tor Vergata)

#### Weak Decays and Matrix Elements

- Mattia Bruno (Brookhaven Natl. Lab.)

#### Weak Decays and Matrix Elements

- Oliver Witzel (University of Edinburgh)

Dr
Jon Bailey
(Seoul National University)

7/27/16, 9:00 AM

Weak Decays and Matrix Elements

Talk

The Oktay-Kronfeld action is a highly improved version of the Fermilab action and
systematically reduces heavy quark discretization effects through $\mathcal{O}(\lambda^3)$ in HQET power counting, for the heavy-light meson spectrum. To calculate $\bar{B}\rightarrow D^{(*)}\ell \bar{\nu}$ semi-leptonic form factors using Oktay-Kronfeld heavy quarks, we need to improve the heavy quark currents...

Mr
Judd Harrison
(Department of applied mathematics and theoretical physics, University of Cambridge)

7/27/16, 9:20 AM

Weak Decays and Matrix Elements

Talk

We present our recent calculation of the zero-recoil form factor for the semileptonic decay $\bar{B}^0\rightarrow D^{*+} \ell^- \bar{\nu} $ using lattice QCD with 2+1+1 flavours of highly improved staggered quarks in the sea (the MILC HISQ configurations) and using non-relativistic QCD for the bottom quark. We obtain $\mathcal{F}(1)$ and combine this with the latest HFAG average of $\eta_{EW}...

Dr
Andrew Lytle
(University of Glasgow)

7/27/16, 9:40 AM

Weak Decays and Matrix Elements

Talk

We use both non-relativistic QCD (NRQCD) and fully relativistic formalisms to calculate
semileptonic form factors for the decays B_c -> eta_c lv and B_c -> J/psi lv over the entire q^2 range. To achieve this we employ a highly improved lattice quark action at several lattice spacings down to a=.044 fm, which allows a fully relativistic treatment of charm and simulation of the full q^2 range...

Dr
Chris Monahan
(Rutgers, the State University of New Jersey)

7/27/16, 10:00 AM

Weak Decays and Matrix Elements

Talk

We present a calculation of the form factors, $f_0$ and $f_+$, for the $B_{(s)}$ to $D_{(s)}$ semileptonic decays. Our work uses the MILC $n_f=2+1$ asqtad configurations with NRQCD and HISQ valence quarks at four values of the momentum transfer $q^2$. We present preliminary results for our combined chiral-continuum extrapolation.

Dr
Oliver Witzel
(University of Edinburgh)

7/27/16, 10:20 AM

Weak Decays and Matrix Elements

Talk

First results for our calculation of semi-leptonic $B$ decays with charmed-mesons in the final state are presented. Our work is based on RBC-UKQCD's 2+1 flavor domain-wall fermion and Iwasaki gauge field configurations, We calculate the form factors by simulating the $b$ quarks using the relativistic heavy quark action, create light $u/d$ and $s$ quarks with standard domain-wall kernel, and...

Dr
Matthew Wingate
(University of Cambridge)

7/27/16, 10:40 AM

Weak Decays and Matrix Elements

Talk

The width difference $\Delta \Gamma_s$ is one of three observables,
along with the mass splitting $\Delta M_s$ and the semileptonic CP
asymmetry $a^s_{\mathrm{SL}}$, whose measurements completely constrain
the physics of $B_s-\bar{B}_s$ oscillations. One of the
dominant uncertainties in theoretical calculations of the width
difference is due to not knowing matrix elements of...

Mr
Masaaki Tomii
(SOKENDAI)

7/27/16, 11:30 AM

Weak Decays and Matrix Elements

Talk

We calculate the current correlators in the coordinate space and compare
them with the experimental information obtained through the spectral
functions of hadronic tau decays at ALEPH.
Lattice data are obtained with 2+1 Mobius domain-wall fermions at
three lattice spacings 0.044, 0.055 and 0.080 fm and the continuum limit
is taken.
On the experimental side, there is no information for...

Dr
Nazario Tantalo
(Rome University Tor Vergata and INFN sez. of Rome Tor Vergata)

7/27/16, 11:50 AM

Weak Decays and Matrix Elements

Talk

In Ref.[1] we proposed a method for calculating leptonic (and semileptonic) decay rates of pseudoscalar mesons including $O(\alpha)$ electromagnetic corrections. Because of the presence of infrared divergences, this requires the calculation of contributions with both virtual and real photons. We have shown that the real photon contribution, by integrating up to photon momenta of the order of...

Dr
Silvano Simula
(INFN - Roma Tre)

7/27/16, 12:10 PM

Weak Decays and Matrix Elements

Talk

Electromagnetic effects on the leptonic decay rates pi+ -> mu+ nu and K+ -> mu+ nu are evaluated for the first time on the lattice.
Following a method recently proposed in Ref. [1] the emission of virtual photons at leading order in the e.m. coupling is evaluated on the lattice with the subtraction of the infrared divergence computed for a point-like meson at finite lattice volume.
The...

Prof.
Johan Bijnens
(Lund University)

7/28/16, 2:00 PM

Weak Decays and Matrix Elements

Talk

Recent progress in mesonic Chiral Perturbation Theory at finite volume
and/or with twisted boundary conditions will be discussed. Topics include
the finite volume at two-loop order calculations of masses and decay constants
for the pseudoscalar of the normal case for two and three flavours [1],
partially quenched three flavour [2] and the case for different patterns of
spontaneous...

Dr
Elvira Gamiz
(University of Granada)

7/28/16, 2:20 PM

Weak Decays and Matrix Elements

Talk

We present an update of our calculation of the $K_{\ell 3}$ form factor $f_+^{K \pi}(0)$, with added statistics and the inclusion of new ensembles with smaller lattice spacing. In addition, we now also include a study of finite volume effects using a version of staggered ChPT that includes the effects of twisted boundary conditions.We also examine the implications for the unitarity of the CKM...

Dr
Enno E. Scholz
(University of Regensburg)

7/28/16, 2:40 PM

Weak Decays and Matrix Elements

Talk

The leptonic decay-constant ratio $f_K/f_\pi$ is calculated from lattice-QCD simulations using $N_f=2+1$ dynamical fermion flavors in the clover-improved formulation and 2-HEX smearing. The simulations were performed at a range of mass-degenerate light quarks including the physical point and at various lattice couplings and volumes, allowing to quantify all relevant sources of systematic...

Dr
Roger Horsley
(University of Edinburgh)

7/28/16, 3:00 PM

Weak Decays and Matrix Elements

Talk

The SU(3) flavour symmetry breaking expansion in up, down and
strange quark masses is extended from hadron masses to meson
decay constants. This allows a determination of the ratio of
kaon to pion decay constants in QCD. Furthermore when using
partially quenched valence quarks the expansion is such that
SU(2) isospin breaking effects can also be determined. It is
found that the lowest...

Kim Maltman
(York University)

7/28/16, 3:20 PM

Weak Decays and Matrix Elements

Talk

We discuss the current status of the determination of V_us based on
flavor-breaking finite energy sum rule analyses of non-strange and
strange hadronic tau decay data, highlighting the role of lattice
input in providing a means of investigating the reliability of the
OPE representation for the relevant flavor-breaking polarization
combination employed in this analysis, and in quantifying...

Dr
Hiroshi Ohki
(RIKEN BNL Research Center)

7/28/16, 3:40 PM

Weak Decays and Matrix Elements

Talk

We present a novel approach to determining Vus which employs inclusive
strange hadronic tau decay data and hadronic vacuum polarization functions
(HVPs) computed on the lattice. The experimental and lattice data are
related through dispersion relations which employ a class of weight functions
which are products of factors having poles at Euclidean Q^2.
Implementing this approach using...

Dr
Mattia Bruno
(Brookhaven Natl. Lab.)

7/28/16, 4:30 PM

Weak Decays and Matrix Elements

Talk

Perturbation theory plays a significant role in some lattice calculations, in particular in those related to weak processes. Here we discuss the possibility to calculate the Wilson Coefficients of the leading order electro-weak effective Hamiltonian of the Standard model to all order in the strong coupling constant, using lattice simulations.

Dr
Christopher Kelly
(Columbia University)

7/28/16, 4:50 PM

Weak Decays and Matrix Elements

Talk

We discuss recent progress by the RBC & UKQCD collaborations in the lattice calculation of the measure of Standard Model direct CP violation, \epsilon', with physical kinematics. We present results with improved systematic errors resulting from the use of step-scaling to
reduce the renormalization error, an analysis that also takes into account the one-loop-suppressed mixing with the G_1...

Prof.
Norman Christ
(Columbia University)

7/28/16, 5:10 PM

Weak Decays and Matrix Elements

Talk

The rare kaon decays K+ -> pi+ nu nu-bar are highly suppressed in the standard model and thus provide an ideal place to search for new physics beyond the standard model. These decays are the principal objective of a new experiment, NA62 at CERN. Another new experiment to search for KL -> pi0 nu nu-bar is now underway at J-PARC. Given the goal of 10% precision by NA62, it is important to...

Mr
Ziyuan Bai
(Columbia)

7/28/16, 5:30 PM

Weak Decays and Matrix Elements

Talk

We demonstrate the lattice QCD calculation of the long distance contribution
to $\epsilon_K$. Due to the singular, short-distance structure of
$epsilon_K$, we must perform a short-distance subtraction and introduce a
corresponding subtraction term determined from perturbation theory, which
we calculate at Next Leading Order (NLO). We perform the calculation on a
$24^3 \times 64$ lattice...

Mr
Andrew Lawson
(University of Southampton)

7/28/16, 5:50 PM

Weak Decays and Matrix Elements

Talk

The rare decays of a kaon into a pion and a lepton/antilepton pair proceed via a flavour changing neutral current and therefore first arise in the Standard Model only as a second order electroweak interaction. This natural suppression makes these decays sensitive to the effects of potential New Physics. However the rare decay channels K+ -> pi+ l+ l- are dominated by contributions from...

Mr
Justus Tobias Tsang
(University of Southampton)

7/29/16, 2:00 PM

Weak Decays and Matrix Elements

Talk

This talk will provide an overview of RBC/UKQCD's charm project on their 2+1 flavour physical point ensembles using Domain Wall Fermions for the light as well as for the charm quarks. I will discuss the analysis strategy and present the latest results for the $D$ and $D_s$ decay constants. I will also outline the wider charm-related physics program of RBC/UKQCD.

Dr
Takashi Kaneko
(KEK)

7/29/16, 2:20 PM

Weak Decays and Matrix Elements

Talk

We report on our study of $D$ meson semileptonic decays
in 2+1 flavor lattice QCD. Gauge ensembles are generated
at the lattice cutoffs around 2.5 GeV and above
and at pion masses as low as 300 MeV. We employ
the Moebius domain-wall action for both light
and charm quarks. We report our preliminary results for
the vector and scalar form factors.

Giorgio Salerno
(Università di Roma Tre)

7/29/16, 2:40 PM

Weak Decays and Matrix Elements

Talk

We present lattice results of the form factors relevant for semileptonic $D\to\pi \ell \nu$ decays, using the gauge ensembles produced by the European Twisted Mass Collaboration with Nf=2+1+1 flavors of dynamical quarks, at three values of the lattice spacing and pion masses as low as 210 MeV.
We have computed the matrix elements of both the vector and scalar weak currents for several...

Aurora Melis
(RomaTre University)

7/29/16, 3:00 PM

Weak Decays and Matrix Elements

Talk

We present the results of a Lattice QCD determination of the heavy-light vector mesons masses and decay constants. The vector decay constants are relevant hadronic parameters that, for instance, can provide phenomenologically good descriptions of non-leptonic decay rates within the factorization approximation.
Our calculation is based on the gauge configurations generated by the European...

Prof.
Steven Gottlieb
(Indiana University)

7/29/16, 3:20 PM

Weak Decays and Matrix Elements

Talk

We present a calculation of the form factors of the $D\to K l \nu$ and $D\to\pi l \nu$ semileptonic decays at zero momentum transfer, ultimately for the purpose of determining the CKM matrix elements $|{V_{cs}}|$ and $|{V_{cd}}|$. This work uses MILC $N_f=2+1+1$ configurations with the HISQ action for both sea quarks and valence quarks, including several physical mass ensembles and lattice...

Dr
Andreas Kronfeld
(Fermilab)

7/29/16, 3:40 PM

Weak Decays and Matrix Elements

Talk

We present results for neutral $D$-meson mixing in 2+1-flavor lattice QCD.
We compute the matrix elements for all five operators that contribute to $D$ mixing at short distances, including those that only arise beyond the Standard Model.
We present a detailed error breakdown for all sources of statistical and systematic uncertainty and the corresponding set of correlations among the matrix...

Claude Bernard
(Washington University),
Javad Komijani
(Technische Universit\"at M\"unchen)

7/29/16, 4:30 PM

Weak Decays and Matrix Elements

Talk

We present high-precision results for the decay constants $f_B$ and $f_{B_s}$ from simulations with HISQ heavy and
light valence and sea quarks. Calculations are carried out with several heavy valence-quark masses on ensembles with
2+1+1 flavors of HISQ sea quarks. We generate data at five lattice spacings with three light sea quark mass ratios,
including an approximately physical...

Prof.
Stefan Meinel
(University of Arizona / RIKEN BNL Research Center)

7/29/16, 4:50 PM

Weak Decays and Matrix Elements

Talk

Experimental results for mesonic $b \to s \mu^+ \mu^-$ decays show a pattern of deviations from Standard-Model predictions. These deviations could be due to new fundamental physics or due to an insufficient understanding of hadronic effects. Complementary information on the $b \to s \mu^+ \mu^-$ transition can be obtained from $\Lambda_b$ decays. This was recently done using the process...

Mr
Edwin Lizarazo
(University of Southampton)

7/29/16, 5:10 PM

Weak Decays and Matrix Elements

Talk

We present an update on our calculation of short distance contributions
to semi-leptonic form factors for rare $B$ decays. Results for $B_s \to
\phi \ell^+\ell^-$ at three lattice spacings of $a^-1 = 1.78$, 2.38, and
2.76 GeV are shown. Our calculations are based on RBC-UKQCD's $N_f =
2+1$ domain-wall fermion and Iwasaki gauge field ensembles. The heavy
$b$-quarks are simulated using the...

Dr
Chris Bouchard
(William & Mary)

7/29/16, 5:30 PM

Weak Decays and Matrix Elements

Talk

We report on our ongoing calculation of the $B\to\pi$ semileptonic decay form factors using NRQCD/HISQ valence quarks with MILC's $N_f=2+1$ asqtad ensembles. The use of HISQ light quarks allows simulation at large pion momenta, corresponding to $q^2\approx 0$, with controlled $(ap)^2$ errors. We perform a simultaneous chiral, continuum, and kinematic extrapolation using the Hard Pion ChPT...

Dr
Debasish Banerjee
(NIC, DESY)

7/29/16, 5:50 PM

Weak Decays and Matrix Elements

Talk

We report on a recent computation of the form factors in semi-leptonic decays of the $B_s$ using Heavy Quark Effective Theory (HQET) formalism applied on the lattice. The connection of the form factors with the 2-point and 3-point correlators on the lattice is explained, and the subsequent non-perturbative renormalization of HQET and it's matching to $N_f=2$ QCD is outlined. The results of the...

Dr
Mateusz Koren
(NIC, DESY Zeuthen)

7/29/16, 6:10 PM

Weak Decays and Matrix Elements

Talk

The extraction of bare ground-state matrix elements for $B_s \to K\ell\nu$ decay at 2% precision poses a significant numerical challenge. Especially the B-sector, treated in HQET, is problematic due to large contamination by excited states combined with the signal-to-noise problem. The numerical setup that we use provides access to all time separations for both the two-point and three-point...