We report recent progress in determining $\varepsilon_K$, the indirect CP violation parameter in the neutral kaon system, calculated using lattice QCD inputs such as $\hat{B}_K$, $\xi_0$, $\xi_2$, $|V_{us}|$, $|V_{cb}|$, and $m_c(m_c)$.
We present the first lattice study of dibaryons with highest bottom number. Utilizing a set of state-of-the-art lattice QCD ensembles and methodologies, we determine ground state of the dibaryon composed of two $\Omega_{bbb}$ baryons. We extract the related scattering amplitude in the $^1S_0$ channel and find a sub threshold pole, which is an unambiguous evidence for a deeply bound...
The dominant contribution to the long distance region of any meson correlation function comes from the quark propagator's eigenmodes with the smallest eigenvalues. As precision demands for this region increase, methods that offer an exact determination of these low modes have become widely adopted as an effective tool for noise reduction. This work explores the effect of exact low modes on...
We report recent progress in data analysis on two-point and three-point correlation functions. The data set of measurement is obtained using the Oktay-Kronfeld (OK) action for the heavy quarks (valence quarks) and the HISQ action for the light quarks on MILC HISQ a12m220 ensemble ($N_f = 2+1+1$ flavors).
Inclusive hadronic $\tau$ decays are particularly interesting from the phenomenological since they give access to $V_{ud}$ and $V_{us}$. A long-standing issue is the tension between the $V_{us}$ determinations coming from leptonic and semileptonic kaon decays and the ones obtained from inclusive hadronic $\tau$ decays. To date (as far as we know) the problem has been addressed indirectly by...
In this study, we explore the distribution of energy-momentum tensor around the static quark and antiquark in SU(3) pure gauge theory at finite temperature. Double extrapolated transverse distributions on mid-plane of the flux tube have been presented for the first time at nonzero temperature. Also, we investigate the spatial distributions of the flux tube on the source plane obtaining from...
We compute the spectra of flux tubes formed between a static quark antiquark pair up to a significant number of excitations and for eight symmetries of the flux tubes, up to $\Delta_u$, using pure gauge $SU(3)$ lattice QCD in 3+1 dimensions. To accomplish this goal, we employ a large set of appropriate operators, an anisotropic tadpole improved action, smearing techniques, and solve a...
A study of heavy-light meson spectroscopy, specifically the excited and exotic spectra of $B$, $B_s$ and $B_c$ is presented. This work was done on an anisotropic lattice of volume $20^3 \times 128$, with (2+1) flavours of dynamical quarks. A large basis of suitable operators was used in a variational analysis to determine finite volume spectra grouped by lattice irrep for each meson....
In this work, we calculate the fine tuning of parameters in N = 1 Super- symmetric QCD, discretized on a Euclidean lattice. Specifically, we study the renormalization of the Yukawa (gluino-quark-squark interactions) and the quar- tic (four-squark interactions) couplings. At the quantum level, these interactions suffer from mixing with other operators which have the same transformation...
Lattice scales defined using gradient flow are typically very precise, while also easy to calculate. However, different definitions of flows and operators can differ, suggesting possible systematical effects. Using the set of RBC-UKQCD 2+1 flavor domain wall fermion and Iwasaki gauge action ensembles, we explore differences between $\sqrt{t_0}$ and $w_0$ gradient flow scales, compare the...
The Lambda parameter of three flavor QCD is obtained by computing the running of a
renormalized finite volume coupling from hadronic to very high energies where connection with perturbation theory can safely be made. The theory of decoupling allows us to perform the bulk of the computation in pure gauge theory. The missing piece is then an accurate matching of a massive three flavor coupling...
We refine our previous study of a $\bar{b}\bar{b}ud$ tetraquark resonance with quantum numbers $I(J^P) = 0(1^-)$ which is based on antistatic-antistatic-light-light lattice QCD potentials by including heavy quark spin effects via the mass difference of the $B$ and $B^\ast$ meson.
This leads to a coupled channel Schroedinger equation where the two channels correspond to $BB$ and $B^\ast B^...
The calculation of disconnected diagram contributions to physical signals is a computationally expensive task in Lattice QCD. To extract the physical signal, the trace of the inverse Lattice Dirac operator, a large sparse matrix, must be stochastically estimated. Because the variance of the stochastic estimator is typically large, variance reduction techniques must be employed. Multilevel...
Staggered fermions, Karsten-Wilczek (KW) fermions and Borici-Creutz (BC) fermions all retain a remnant chiral symmetry. The price to be payed is that they are doubled, and the resulting taste symmetry is broken by cut-off effects. We measure the size of the taste symmetry violation by determining the low-lying eigenvalues of these fermion operators in the two-dimensional Schwinger model which...
We report recent progress in data analysis on two-point correlation functions with HYP-smeared staggered fermions using a sequential bayesian fitting method. We present details on data analysis and preliminary results for the meson spectrum.
We describe our implementation of a multigrid solver for Wilson clover fermions, which increases parallelism by solving for multiple right-hand sides (MRHS) simultaneously. The solver is based on Grid and thus runs on all computing architectures supported by the Grid framework. We present detailed benchmarks of the relevant kernels, such as hopping and clover term on the various multigrid...
QCD sum-rule mass predictions for tetraquark states provide insights on the interpretations and internal structure of experimentally-observed exotic mesons. However, the overwhelming majority of tetraquark QCD sum-rule analyses have been performed at leading order (LO), which raises questions about the underlying theoretical uncertainties from higher-loop corrections. The impact of...
When comparing the Lagrangian and Hamiltonian formulations of lattice gauge theories, a matching procedure is required to match the parameters and observables between these two formulations. For this, we take the continuum limit in time direction on the Lagrangian side, while keeping the spatial lattice spacing fixed. We study several observables for this nonperturbative matching and compare...
The problem of having to reconstruct the decay rates and corresponding amplitudes of the single-exponential components of a noisy multi-exponential signal is common in many other areas of physics and engineering besides lattice field theory, and it can be helpful to study the methods devised and used for that purpose in those contexts in order to get a better handle on the problem of...
Wilson-like Dirac operators can be written in the form $D=\gamma_\mu\nabla_\mu-\frac 12 \Delta$. For Wilson fermions the standard two-point derivative $\nabla_\mu^\mathrm{std}$ and 9-point Laplacian $\Delta^\mathrm{std}$ are used. For Brillouin fermions these are replaced by improved discretizations $\nabla_\mu^\mathrm{iso}$ and $\Delta^\mathrm{bri}$ which have 54- and 81-point stencils...
We report recent progress in data analysis on the correlation functions
of the semileptonic decays $B_{(s)} \to D_{(s)}\ell\nu$ form factors.
The data set of measurement is MILC HISQ ensemble for the light quarks
and Oktay-Kronfeld (OK) action for the heavy quarks: a12m310 ($N_f=2+1+1$ flavor)
We used sequential Bayesian method for the analysis and adopted Newton
method to find...
We investigate $I = 0$ bottomonium bound states and resonances in S, P, D and F waves using lattice QCD static-static-light-light potentials. We consider five coupled channels, one confined quarkonium and four open $B^{(*)}\bar{B}^{(*)}$ and $B^{(*)}_s\bar{B}^{(*)}_s$ meson-meson channels and use the Born-Oppenheimer approximation and the emergent wave method to compute poles of the \box{T}...
In this study, we calculated the effect of self-interacting dark matter on neutron stars. Properties like the mass, radius and the tidal deformability are affected by the presence of dark matter in neutron stars. We show that the Love number can be used to probe the presence and the properties of dark matter inside of neutron stars in future gravitational wave measurements.
Low energy effective models are a useful tool to understand the mechanisms behind physical processes in QCD. They additionally provide ways to probe into regions of the QCD phase diagram that are harder to simulate on the lattice, e.g., small temperature, due to their lower UV cutoff, as well as more direct comparison with functional methods such as fRG. We present here lattice simulations of...
We compute the pion and kaon matrix elements with non-local staple-shaped operators using an $N_f=2+1+1$ twisted mass fermion ensemble. The lattice has volume $24^3 * 48$, lattice spacing $a=0.093 \ fm$ and a pion mass of $350 \ MeV$. We employ momentum smearing to improve the signal as we increase the momentum. We explore momenta corresponding to $1.11 \ GeV$ and $2.78 \ GeV$. We also study...
Bridge++ is a general-purpose code set for lattice QCD simulations aiming at a readable, extensible, and portable code while keeping practically high performance. The new version 2.0 employs machine-dependent optimization,extended from a fixed data layout in double precision only to a flexible data layout in float/double precision. In this talk, we report the performance on supercomputer...
Modern B-factory experiments, such as Belle II, are able to investigate physics anomalies with some
of the largest datasets ever produced. High luminosity datasets allow for precision measurements of
exclusive B-decays, such as in B → ℓν, which in turn reduce error in calculations of the correponding
CKM matrix element, Vub. This is especially important given the current tension between...
High statistics results for quantities like the gradient flow scale, the quark masses, the lower lying baryon spectrum and the baryon octet sigma terms determined on CLS ensembles with $N_f=2+1$ non-perturbatively $O(a)$ improved Wilson dynamical fermions are presented at this conference by the RQCD collaboration. In this contribution, we provide further details of the analysis focusing on...
Our exploratory study looks for direct access to the hadronic transition
amplitude at the resonance without resorting to the Lüscher formalism.
We study the decay $\Psi(3770)\to D\bar{D}$ by applying partially
twisted boundary conditions to the quenched charm quark,
circumventing possible problems with final state interactions.
If successful, we could compute the dependence of the...
Fourier acceleration is a technique used in Hybrid Monte Carlo (HMC) simulations to decrease the autocorrelation length. In the weak interaction limit, Fourier acceleration eliminates the problem of critical slowing down. In this work, we show that by properly tuning the kinetic term in HMC simulations, Fourier acceleration can be applied effectively to a strongly interacting $\phi^4$ theory....
Collins-Soper (CS) evolution kernel is critical to relate transverse-momentum-dependent parton distribution functions (TMDPDFs) at different scales. When the parton transverse momentum is small, $q_{T}\sim\Lambda_{\mathrm{QCD}}$, the CS kernel is non-perturbative; the determination of the CS kernel in the non-perturbative regime can only be done through experiment or first-principles...
Isospin breaking corrections become relevant when aiming to quantify hadronic observables with uncertainties below the percent level. Discretising QED on the lattice is a non-trivial task and several suggested methodologies are available in the literature. Our work uses massive QED, which provides a fully local prescription of QED on the lattice. We present a status update of our ongoing...
The automatic fine-tuning of isospin breaking effects by conformal coalescence found by Howard Georgi in the 2-flavor Schwinger model is studied. Numerical investigation of meson mass splitting confirms the exponential suppression of symmetry breaking effects.
The stochastic LapH method has proven to be successful in hadronic calculations. In this work, with charm light spectroscopy in mind, we set up and optimise the LapH procedure limiting ourselves to the evaluation of 2-point mesonic functions. The calculations are performed on CLS ensembles with $N_F = 2 +1$ Wilson-Clover fermions on a $32^3 \times 64$ lattice with open boundary conditions. The...
We present first results of a recently started lattice QCD investigation of antiheavy-antiheavy-light-light tetraquark systems including scattering interpolating operators in correlation functions both at the source and at the sink. In particular, we discuss the importance of such scattering interpolating operators for a precise computation of the low-lying energy levels in $\bar b \bar b u d$...
Topological freezing is a well known problem in lattice simulations: with shrinking lattice spacing, a transition between topological sectors becomes increasingly improbable, leading to a problematic increase of the autocorrelation time. We present our investigation of metadynamics as a solution for topological freezing in the Schwinger model. Specifically, we take a closer look at the...
We report on the non-perturbative determination of the improvement coefficient $c_A$ of the axial vector current $A^\mu(x)$ in three-flavour lattice QCD with stabilised Wilson-Clover fermions.
Our computational method exploits the PCAC relation for two different pseudo-scalar states within the Schrödinger functional, which are modelled by altering the spatial structures at the boundaries via...
Stabilized Wilson fermions are a reformulation of Wilson clover fermions that incorporates several numerical stabilizing techniques, but also a local change of the fermion action - the original clover term being replaced with an exponentiated version of it. We intend to apply the stabilized Wilson fermions toolbox to the thermodynamics of QCD, starting on the Nf=3 symmetric line on the...
Computations within theories with complex actions are generally inaccessible by standard numerical techniques as they typically suffer from the numerical sign problem. The complex Langevin (CL) method aims to resolve this problem. In recent years CL has been successfully applied to various problems, e.g. the QCD equation of state for finite chemical potential, and therefore also may represent...
This poster reviews the recent HPQCD calcuation of $B_c^+ \to D^0 \ell^+ \nu$ and $B_c^+ \to D_s^+ \ell^+ \ell^- (\nu \bar\nu)$ form factors [Phys. Rev. D 105, 014503 (2022), arXiv:2108.11242]. We comment on prospects for experimental measurement of $B_c^+ \to D^0 \ell^+ \nu$ and implications for CKM matrix elements.
Increasing GPU power across a competitive market of various GPU manufacturers and GPU based supercomputers pushes lattice programmers to develop code usable for multiple APIs. In this poster we showcase SIMULATeQCD, a SImple MUlti-GPU LATtice code for QCD calculations, developed and used by the HotQCD collaboration for large-scale projects on both NVIDIA and AMD GPUs. Our code has been made...
We present preliminary results for the leading strange and charm connected contributions to the hadronic vacuum polarization contribution to the muon's g-2. Measurements are performed on the RC collaboration’s QCD ensembles, with $N_f =3+1$ $O(a)$ improved Wilson fermions and C boundary conditions. The HVP is computed on a single value of the lattice spacing and two lattice volumes. In...
Semileptonic heavy-to-heavy and heavy-to-light $B$ decays are very intriguing transitions since a long-standing tension affects the inclusive and the exclusive determinations of the CKM matrix elements $\vert V_{cb} \vert$ and $\vert V_{ub} \vert$. In the former case, another discrepancy exists between the SM expectations and the measurements of the ratios $R(D^{(*)})$, which are a test of...
The I=1/2 and I=3/2 nucleon-pion scattering lengths are determined from a high-statistics computation on a single ensemble of gauge field configurations from the CLS consortium with dynamical up, down, and strange quarks and a pion mass $m_{\pi} = 200{\rm MeV}$. The stochastic-LapH approach to quark propagation enables the efficient computation of all required correlation functions, and a...
The quark-gluon vertex is an important object of QCD. Studies have shown that this quantity can be relevant for the dynamical chiral symmetry breaking pattern in the vacuum. The goal of our project is to obtain the quark-gluon vertex at finite temperature around the deconfinement/chiral transition using the tools provided by lattice QCD. It will be the first time that the quark-gluon vertex at...
We give an update on the ongoing effort of the RC$^\star$ collaboration to generate fully dynamical QCD+QED ensembles with C$^\star$ boundary conditions using the openQ$^\star$D code. The simulations were tuned to the U-symmetric point ($m_d=m_s$) with pions at $m_{\pi^{\pm}} \approx 400$ MeV. The splitting of the light mesons is used as one of three tuning observables and fixed to...
Gauge covariant smearing based on the 3D lattice Laplacian can be used to create extended operators that have better overlap with hadronic ground states. This is often done iteratively. For staggered quarks using two-link parallel transport preserves taste properties. We found that such iterative smearing was taking an inordinate amount of time when done on the CPU, so we have implemented the...
We give an update on our ongoing studies of the light composite scalar in eight-flavor SU(3) gauge theory. The chiral limit of this theory can serve as the strong dynamics input to a number of composite Higgs models. Composite Higgs models of this type naturally produce $S$ and $T$ parameters of the size required to explain the new CDF $W$ mass measurement. We present our improved subtraction...
