Oliver Witzel
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Oliver Witzel has a total of 141 co-authors. Here are the top co-authors by number of shared publications:
- Anna Hasenfratz
University of Colorado, Boulder
29 shared publications - Claudio Rebbi
Boston University
12 shared publications - Ethan T. Neil
University of Colorado
5 shared publications Anna Hasenfratz
Department of Physics University of Colorado 80309 Boulder CO United States
4 shared publicationsClaudio Rebbi
Department of Physics and Center for Computational Science, Boston University, Boston, Massachusetts 02215, USA
4 shared publicationsAmarjit Soni
Physics Department Brookhaven National Laboratory 11973 Upton NY USA
3 shared publications
Latest Publications
- Open Access
- 5 November 2026
- Published by American Physical Society (APS) in Physical Review D
- Vol. 114 (9) , 094503
Heavy-meson bag parameters using gradient flow
We demonstrate the use of the gradient flow combined with the short flow-time expansion ( GF + SFTX ) as a renormalization procedure for four-quark operator matrix elements and associated bag parameters relevant to neutral heavy-meson mixing ( Δ Q = 2 ) and heavy-meson lifetimes ( Δ Q = 0 ). Using six RBC/UKQCD 2 + 1 -flavor domain-wall fermion ensembles, we calculate for a charm-strange system with physical quark masses flowed bag parameters and match them to the MS ¯ scheme using perturbative SFTX coefficients up to next-to-next-to-leading order in QCD. We employ a multiscale matching strategy and a renormalization-group improved flow-time evolution which allows for a reliable estimate of systematic uncertainties. For a fictitious neutral D s meson, we obtain the Δ Q = 2 MS ¯ bag parameter B 1 MS ¯ ( 3 GeV ) = 0.7673 ( 123 ) , consistent with existing short-distance D 0 mixing determinations. For the Δ Q = 0 lifetime-ratio operator basis, we find the MS ¯ results B 1 MS ¯ ( 3 GeV ) = 1.0524 ( 97 ) , B 2 MS ¯ ( 3 GeV ) = 0.9621 ( 71 ) , ε 1 MS ¯ ( 3 GeV ) = − 0.2275 ( 76 ) , and ε 2 MS ¯ ( 3 GeV ) = − 0.0005 ( 8 ) . We provide conversion formulae to reexpress these results for an arbitrary choice of evanescent operators. These results demonstrate that GF + SFTX can deliver precise determinations of dimension-six four-quark operators and establish a framework for future lattice computations including more complex operator bases, where the challenge of power-divergent mixing is shifted to the continuum and handled in the SFTX.
- 5 November 2026
- Published by American Physical Society (APS) in Physical Review D
- Vol. 114 (9) , 094503
Open AccessHeavy-meson bag parameters using gradient flow
We demonstrate the use of the gradient flow combined with the short flow-time expansion ( GF + SFTX ) as a renormalization procedure for four-quark operator matrix elements and associated bag parameters relevant to neutral heavy-meson mixing ( Δ Q = 2 ) and heavy-meson lifetimes ( Δ Q = 0 ). Using six RBC/UKQCD 2 + 1 -flavor domain-wall fermion ensembles, we calculate for a charm-strange system with physical quark masses flowed bag parameters and match them to the MS ¯ scheme using perturbative SFTX coefficients up to next-to-next-to-leading order in QCD. We employ a multiscale matching strategy and a renormalization-group improved flow-time evolution which allows for a reliable estimate of systematic uncertainties. For a fictitious neutral D s meson, we obtain the Δ Q = 2 MS ¯ bag parameter B 1 MS ¯ ( 3 GeV ) = 0.7673 ( 123 ) , consistent with existing short-distance D 0 mixing determinations. For the Δ Q = 0 lifetime-ratio operator basis, we find the MS ¯ results B 1 MS ¯ ( 3 GeV ) = 1.0524 ( 97 ) , B 2 MS ¯ ( 3 GeV ) = 0.9621 ( 71 ) , ε 1 MS ¯ ( 3 GeV ) = − 0.2275 ( 76 ) , and ε 2 MS ¯ ( 3 GeV ) = − 0.0005 ( 8 ) . We provide conversion formulae to reexpress these results for an arbitrary choice of evanescent operators. These results demonstrate that GF + SFTX can deliver precise determinations of dimension-six four-quark operators and establish a framework for future lattice computations including more complex operator bases, where the challenge of power-divergent mixing is shifted to the continuum and handled in the SFTX.
- Open Access
- 5 November 2026
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 137 (19) , 191905
Bag Parameters for Heavy Meson Lifetimes from a Lattice QCD Calculation at the SU ( 3 ) F -symmetric Point
We calculate the dimension-six Δ Q = 0 four-quark matrix elements describing heavy-meson lifetime ratios using the gradient flow with its short flow-time expansion (SFTX) as a renormalization procedure. On six RBC/UKQCD 2 + 1 -flavor domain-wall fermion ensembles, we determine flowed bag parameters for physical charm and strange quarks and match to the MS ¯ scheme with perturbative SFTX coefficients through next-to-next-to-leading order (NNLO). A multiscale matching procedure using renormalization-group running improves the extrapolation to zero flow time. For the operators relevant to τ ( D s ) / τ ( D 0 ) at the SU ( 3 ) F symmetric point, we obtain B 1 MS ¯ ( 3 GeV ) = 1.0524 ( 97 ) , B 2 MS ¯ ( 3 GeV ) = 0.9621 ( 70 ) , ε 1 MS ¯ ( 3 GeV ) = − 0.2275 ( 76 ) , and ε 2 MS ¯ ( 3 GeV ) = − 0.0005 ( 8 ) using a specific choice of evanescent operators. This is the first lattice-QCD determination of Δ Q = 0 four-quark operators with a full error budget. It opens the path toward higher-precision predictions of heavy-meson lifetimes and similar quantities exhibiting operator mixing under renormalization.
- 5 November 2026
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 137 (19) , 191905
Open AccessBag Parameters for Heavy Meson Lifetimes from a Lattice QCD Calculation at the SU ( 3 ) F -symmetric Point
We calculate the dimension-six Δ Q = 0 four-quark matrix elements describing heavy-meson lifetime ratios using the gradient flow with its short flow-time expansion (SFTX) as a renormalization procedure. On six RBC/UKQCD 2 + 1 -flavor domain-wall fermion ensembles, we determine flowed bag parameters for physical charm and strange quarks and match to the MS ¯ scheme with perturbative SFTX coefficients through next-to-next-to-leading order (NNLO). A multiscale matching procedure using renormalization-group running improves the extrapolation to zero flow time. For the operators relevant to τ ( D s ) / τ ( D 0 ) at the SU ( 3 ) F symmetric point, we obtain B 1 MS ¯ ( 3 GeV ) = 1.0524 ( 97 ) , B 2 MS ¯ ( 3 GeV ) = 0.9621 ( 70 ) , ε 1 MS ¯ ( 3 GeV ) = − 0.2275 ( 76 ) , and ε 2 MS ¯ ( 3 GeV ) = − 0.0005 ( 8 ) using a specific choice of evanescent operators. This is the first lattice-QCD determination of Δ Q = 0 four-quark operators with a full error budget. It opens the path toward higher-precision predictions of heavy-meson lifetimes and similar quantities exhibiting operator mixing under renormalization.
- Open Access
- 21 May 2026
- Published by American Physical Society (APS) in Physical Review D
- Vol. 113 (9)
Renormalized quark masses using gradient flow
We propose a new and simple method for determining the renormalized quark masses from lattice simulations. Renormalized quark masses are an important input to many phenomenological applications, including searching and modeling physics beyond the Standard Model. The nonperturbative renormalization is performed using gradient flow combined with the short-flow-time expansion that is improved by renormalization group (RG) running to match to the MS ¯ scheme. Implementing the RG running perturbatively, we demonstrate this method works reliably at least up to the charm-quark mass and exhibits an easily attainable “windowing condition.” Using RBC/UKQCD’s ( 2 + 1 )-flavor Shamir domain-wall fermion ensembles with Iwasaki gauge action, we find m s MS ¯ ( μ = 2 GeV ) = 89 ( 3 ) MeV and m c MS ¯ ( μ = 3 GeV ) = 972 ( 16 ) MeV . These results predict the scale-independent ratio m c / m s = 12.1 ( 4 ) . Generalization to other observables is possible, providing an efficient approach to determine nonperturbatively renormalized fermionic observables like form factors or bag parameters from lattice simulations.
- 21 May 2026
- Published by American Physical Society (APS) in Physical Review D
- Vol. 113 (9)
Open AccessRenormalized quark masses using gradient flow
We propose a new and simple method for determining the renormalized quark masses from lattice simulations. Renormalized quark masses are an important input to many phenomenological applications, including searching and modeling physics beyond the Standard Model. The nonperturbative renormalization is performed using gradient flow combined with the short-flow-time expansion that is improved by renormalization group (RG) running to match to the MS ¯ scheme. Implementing the RG running perturbatively, we demonstrate this method works reliably at least up to the charm-quark mass and exhibits an easily attainable “windowing condition.” Using RBC/UKQCD’s ( 2 + 1 )-flavor Shamir domain-wall fermion ensembles with Iwasaki gauge action, we find m s MS ¯ ( μ = 2 GeV ) = 89 ( 3 ) MeV and m c MS ¯ ( μ = 3 GeV ) = 972 ( 16 ) MeV . These results predict the scale-independent ratio m c / m s = 12.1 ( 4 ) . Generalization to other observables is possible, providing an efficient approach to determine nonperturbatively renormalized fermionic observables like form factors or bag parameters from lattice simulations.
- Open Access
- 6 February 2026
- Published by Sissa Medialab Srl
- Vol. 485, 467
Symmetric Mass Generation
In recent years tantalizing signs for a novel phase have been reported that is chirally symmetric but nevertheless exhibits massive bound states. The necessary condition for such a phase, referred to as Symmetric Mass Generation (SMG), is the cancellation of all (continuous and discrete) 't~Hooft anomalies. In 3+1 dimensions this occurs in systems containing a multiple of 16 massless Weyl fermions. SMG was originally discovered in lower dimensional condensed matter systems. We present results investigating four dimensional field theories with gauge group SU(3). Our findings suggest that SU(3) with $N_f=8$ fundamental fermions exhibits an SMG phase not only on the lattice but also in the infinite cutoff continuum limit. If confirmed, SMG could provide a new UV completion of the standard model and give rise to new scenarios for beyond standard model physics.- 6 February 2026
- Published by Sissa Medialab Srl
- Vol. 485, 467
Open AccessSymmetric Mass Generation
In recent years tantalizing signs for a novel phase have been reported that is chirally symmetric but nevertheless exhibits massive bound states. The necessary condition for such a phase, referred to as Symmetric Mass Generation (SMG), is the cancellation of all (continuous and discrete) 't~Hooft anomalies. In 3+1 dimensions this occurs in systems containing a multiple of 16 massless Weyl fermions. SMG was originally discovered in lower dimensional condensed matter systems. We present results investigating four dimensional field theories with gauge group SU(3). Our findings suggest that SU(3) with $N_f=8$ fundamental fermions exhibits an SMG phase not only on the lattice but also in the infinite cutoff continuum limit. If confirmed, SMG could provide a new UV completion of the standard model and give rise to new scenarios for beyond standard model physics. - Open Access
Symmetric Mass Generation
In recent years tantalizing signs for a novel phase have been reported that is chirally symmetric but nevertheless exhibits massive bound states. The necessary condition for such a phase, referred to as Symmetric Mass Generation (SMG), is the cancellation of all (continuous and discrete) 't~Hooft anomalies. In 3+1 dimensions this occurs in systems containing a multiple of 16 massless Weyl fermions. SMG was originally discovered in lower dimensional condensed matter systems. We present results investigating four dimensional field theories with gauge group SU(3). Our findings suggest that SU(3) with $N_f=8$ fundamental fermions exhibits an SMG phase not only on the lattice but also in the infinite cutoff continuum limit. If confirmed, SMG could provide a new UV completion of the standard model and give rise to new scenarios for beyond standard model physics.Open AccessSymmetric Mass Generation
In recent years tantalizing signs for a novel phase have been reported that is chirally symmetric but nevertheless exhibits massive bound states. The necessary condition for such a phase, referred to as Symmetric Mass Generation (SMG), is the cancellation of all (continuous and discrete) 't~Hooft anomalies. In 3+1 dimensions this occurs in systems containing a multiple of 16 massless Weyl fermions. SMG was originally discovered in lower dimensional condensed matter systems. We present results investigating four dimensional field theories with gauge group SU(3). Our findings suggest that SU(3) with $N_f=8$ fundamental fermions exhibits an SMG phase not only on the lattice but also in the infinite cutoff continuum limit. If confirmed, SMG could provide a new UV completion of the standard model and give rise to new scenarios for beyond standard model physics. - Open Access
- 30 January 2025
- Published by Sissa Medialab Srl
- Vol. 466, 146
Investigating SU(3) with $N_f=8$ fundamental fermions at strong renormalized couplingLattice simulations have observed a novel strong coupling symmetric mass generation (SMG) phase for the SU(3) gauge system with $N_f=8$ fundamental fermions (represented by two sets of staggered fields) at very large renormalized coupling ($g^2_{GF} \gtrsim 25$). The results of Phys.~Rev.~D 106 (2022) 014513 suggest that the SMG phase is separated from the weak coupling, conformal phase by a continuous phase transition, implying that the SMG phase exists in the continuum limit. To scrutinize these findings, we are generating a set of large volume zero temperature ensembles using nHYP improved staggered fermions with additional Pauli-Villars fields to tame gauge field fluctuations. We consider the low-lying meson spectrum and verify the existence of the SMG phase. Based on a finite size scaling analysis we predict that the phase transition between the strong and weak coupling phases is likely governed by a merged fixed point that is ultraviolet in the strong coupling but infrared in the weak coupling side. This finding suggests that the SU(3) 8-flavor system sits at the opening of the conformal window.- 30 January 2025
- Published by Sissa Medialab Srl
- Vol. 466, 146
Open AccessInvestigating SU(3) with $N_f=8$ fundamental fermions at strong renormalized couplingLattice simulations have observed a novel strong coupling symmetric mass generation (SMG) phase for the SU(3) gauge system with $N_f=8$ fundamental fermions (represented by two sets of staggered fields) at very large renormalized coupling ($g^2_{GF} \gtrsim 25$). The results of Phys.~Rev.~D 106 (2022) 014513 suggest that the SMG phase is separated from the weak coupling, conformal phase by a continuous phase transition, implying that the SMG phase exists in the continuum limit. To scrutinize these findings, we are generating a set of large volume zero temperature ensembles using nHYP improved staggered fermions with additional Pauli-Villars fields to tame gauge field fluctuations. We consider the low-lying meson spectrum and verify the existence of the SMG phase. Based on a finite size scaling analysis we predict that the phase transition between the strong and weak coupling phases is likely governed by a merged fixed point that is ultraviolet in the strong coupling but infrared in the weak coupling side. This finding suggests that the SU(3) 8-flavor system sits at the opening of the conformal window. - Open Access
Investigating SU(3) with Nf=8 fundamental fermions at strong renormalized coupling
Lattice simulations have observed a novel strong coupling symmetric mass generation (SMG) phase for the SU(3) gauge system with $N_f=8$ fundamental fermions (represented by two sets of staggered fields) at very large renormalized coupling ($g^2_{GF} \gtrsim 25$). The results of Phys.Rev.D 106 (2022) 014513 suggest that the SMG phase is separated from the weak coupling, conformal phase by a continuous phase transition, implying that the SMG phase exists in the continuum limit. To scrutinize these findings, we are generating a set of large volume zero temperature ensembles using nHYP improved staggered fermions with additional Pauli-Villars fields to tame gauge field fluctuations. We consider the low-lying meson spectrum and verify the existence of the SMG phase. Based on a finite size scaling analysis we predict that the phase transition between the strong and weak coupling phases is likely governed by a merged fixed point that is ultraviolet in the strong coupling but infrared in the weak coupling side. This finding suggests that the SU(3) 8-flavor system sits at the opening of the conformal windowOpen AccessInvestigating SU(3) with Nf=8 fundamental fermions at strong renormalized coupling
Lattice simulations have observed a novel strong coupling symmetric mass generation (SMG) phase for the SU(3) gauge system with $N_f=8$ fundamental fermions (represented by two sets of staggered fields) at very large renormalized coupling ($g^2_{GF} \gtrsim 25$). The results of Phys.Rev.D 106 (2022) 014513 suggest that the SMG phase is separated from the weak coupling, conformal phase by a continuous phase transition, implying that the SMG phase exists in the continuum limit. To scrutinize these findings, we are generating a set of large volume zero temperature ensembles using nHYP improved staggered fermions with additional Pauli-Villars fields to tame gauge field fluctuations. We consider the low-lying meson spectrum and verify the existence of the SMG phase. Based on a finite size scaling analysis we predict that the phase transition between the strong and weak coupling phases is likely governed by a merged fixed point that is ultraviolet in the strong coupling but infrared in the weak coupling side. This finding suggests that the SU(3) 8-flavor system sits at the opening of the conformal window - Open Access
- 20 November 2024
- Published by EDP Sciences in EPJ Web of Conferences
- Vol. 312, 04001
Theory on CKM and heavy quark decay
The combination of precise experimental measurements and theoretical predictions allows to extract Cabibbo-Kobayashi-Maskawa (CKM) matrix elements or constrain flavor changing processes in the standard model. Focusing at theoretical predictions, we review recent highlights from the sector of heavy charm and bottom quark decays. Special emphasis is given to nonperturbative contributions due to the strong force calculated using lattice QCD.
- 20 November 2024
- Published by EDP Sciences in EPJ Web of Conferences
- Vol. 312, 04001
Open AccessTheory on CKM and heavy quark decay
The combination of precise experimental measurements and theoretical predictions allows to extract Cabibbo-Kobayashi-Maskawa (CKM) matrix elements or constrain flavor changing processes in the standard model. Focusing at theoretical predictions, we review recent highlights from the sector of heavy charm and bottom quark decays. Special emphasis is given to nonperturbative contributions due to the strong force calculated using lattice QCD.
- Open Access
- 4 September 2024
- Published by American Physical Society (APS) in Physical Review D
- Vol. 110 (5) , 054501
Light scalar meson and decay constant in SU(3) gauge theory with eight dynamical flavors
The SU(3) gauge theory with nearly massless Dirac fermions has long been of theoretical and phenomenological interest due to the near-conformality arising from its proximity to the conformal window. One particularly interesting feature is the emergence of a relatively light, stable flavor-singlet scalar meson in contrast to the theory QCD. In this work, we study the finite-volume dependence of the meson correlation function computed in lattice gauge theory and determine the meson mass and decay constant extrapolated to the infinite-volume limit. We also determine the infinite-volume mass and decay constant of the flavor-nonsinglet scalar meson .- 4 September 2024
- Published by American Physical Society (APS) in Physical Review D
- Vol. 110 (5) , 054501
Open AccessLight scalar meson and decay constant in SU(3) gauge theory with eight dynamical flavors
The SU(3) gauge theory with nearly massless Dirac fermions has long been of theoretical and phenomenological interest due to the near-conformality arising from its proximity to the conformal window. One particularly interesting feature is the emergence of a relatively light, stable flavor-singlet scalar meson in contrast to the theory QCD. In this work, we study the finite-volume dependence of the meson correlation function computed in lattice gauge theory and determine the meson mass and decay constant extrapolated to the infinite-volume limit. We also determine the infinite-volume mass and decay constant of the flavor-nonsinglet scalar meson . - Open Access
Theory on CKM and heavy quark decay
The combination of precise experimental measurements and theoretical predictions allows to extract Cabibbo-Kobayashi-Maskawa (CKM) matrix elements or constrain flavor changing processes in the standard model. Focusing at theoretical predictions, we review recent highlights from the sector of heavy charm and bottom quark decays. Special emphasis is given to nonperturbative contributions due to the strong force calculated using lattice QCD.
Open AccessTheory on CKM and heavy quark decay
The combination of precise experimental measurements and theoretical predictions allows to extract Cabibbo-Kobayashi-Maskawa (CKM) matrix elements or constrain flavor changing processes in the standard model. Focusing at theoretical predictions, we review recent highlights from the sector of heavy charm and bottom quark decays. Special emphasis is given to nonperturbative contributions due to the strong force calculated using lattice QCD.