Conveners
Particle physics beyond the Standard Model
- Axel Torsten Maas (University of Graz)
Particle physics beyond the Standard Model
- Claudio Rebbi (Boston University)
Particle physics beyond the Standard Model
- Hiroshi Suzuki (Kyushu Univ.)
Particle physics beyond the Standard Model
- David Schaich (University of Liverpool)
- Enrico Rinaldi (Lawrence Livermore National Laboratory)
We investigate the renormalization of the Gluino-Glue operator, using both Lattice Perturbation Theory (LPT) and a Gauge Invariant Renormalization Scheme (GIRS). The latter scheme involves gauge-invariant Green's functions of two operators at different space-time points, which can be also computed via numerical simulations. There is no need to fix a gauge and the mixing with gauge noninvariant...
$\mathcal{N} = 1$ supersymmetric Yang-Mills theory describes gluons interacting with gluinos, which are spin 1/2 Majorana particles in the adjoint representation of the gauge group. In addition to glueballs and mesonic bound states, the theory contains colour neutral bound states of three gluinos, which are analogous to baryons in QCD. We calculate their correlation functions, involving...
We numerically study QCD with a single quark flavour on the lattice probing predictions from effective field theories that are equivalent to minimal super-symmetric Yang-Mills theory in the large $N_c$ limit.
The hadronic spectrum including excited states is analyzed using one gauge coupling and several physical volumes and fermion masses. We use the LapH method and also compute...
Gauge theories with fermions in adjoint and fundamental representations are relevant for many different applications including composite Higgs models and general aspects of the confinement problem. In this talk, I will present first results from simulations of SU(2) gauge theory with two Dirac fermions in the fundamental representation and one adjoint Majorana flavour. In this context, I will...
We introduce a on-parameter family of SU(N) gauge actions which, when used in combination with an HMC update algorithm, prevent the gauge system from entering an artificial bulk-"phase". We briefly discuss the (presumed) mechanism behind the bulk-prevention and present test results for different SU(N) gauge groups.
I will present lattice investigations into the thermal phase structure of the Berenstein--Maldacena--Nastase deformation of maximally supersymmetric Yang--Mills quantum mechanics. The phase diagram of the theory depends on both the temperature $T$ and the deformation parameter $\mu$, through the dimensionless ratios $T / \mu$ and $g = \lambda / \mu^3$ with $\lambda$ the 't Hooft coupling. We...
In this talk we present results from numerical simulations of $\mathcal{N}$ = 4 super Yang-Mills for two color gauge theory over a wide range of ’t Hooft coupling $0 < \lambda ≤ 30$ using a supersymmetric lattice action. Numerical study of this lattice theory has been stymied until recently by both sign problems and the occurrence of lattice artifact phases at strong coupling. We have recently...
Mass-split models are governed by a nearby conformal infrared fixed point and therefore feature by construction a large separation of scales. This makes them attractive candidates to explore beyond the standard model scenarios describing the Higgs boson as a composite particle. We report updates on our investigation based on an SU(3) gauge theory with four light and six heavy flavors in the...
In this talk, we present a lattice study of the scattering of pseudo-Goldstone Bosons in SU(3) gauge theory with $N_f=8$ light Dirac fermions, a theory which lies close to the boundary of the conformal window. The scattering phase shift is measured in the s-wave, maximal isospin channel for different values of the scattering momentum, as well as for different values of the underlying fermion...
We review dilaton chiral perturbation theory (dChPT), the low-energy theory for the light sector of near-conformal, confining theories. dChPT accounts for the pions and the light scalar,and provides a systematic expansion in both the fermion mass and the distance to the conformal window. Unlike ChPT, dChPT predicts a large-mass regime in which the theory exhibits hyperscaling,while the...
We calculate the low-energy constant $L_{10}$ in an SU(4) lattice gauge theory
with dynamical fermions in two representations. This theory is close to a particular composite-Higgs model. From this, we obtain the contribution of the new strong sector to the S parameter. The resulting upper bound on the vacuum misalignment parameter $\xi$ is similar to current estimates for this bound. We...
In the context of possible dilaton behavior in near conformal gauge theories, it has recently been proposed that a parametrized potential $V_\Delta$, interpolating between two limiting forms, might effectively describe the light particle spectrum. We tested two models, namely SU(3) gauge theory with $N_f = 8$ fermions in the fundamental rep or $N_f = 2$ fermions in the sextet rep, against this...
We present various applications of the gradient-flow beta-function, including an extended study of the finite-volume version in the $N_f = 10$ fundamental rep SU(3) model, prompted by claims of possible conformality. We show how the infinite-volume beta-function can be reached through a sequence of stages, handling the correlation across gradient-flow time when taking the continuum limit, and...
The RG beta function describes the running of the renormalized coupling and connects the ultraviolet and infrared regimes of quantum field theories. We consider both the finite volume step scaling and the continuous beta function of the gradient flow coupling in SU(3) systems with fundamental fermions. Investigating theories with $N_f=6$, 8, 10 and 12 flavors allows us to study the onset of...
We study baryon-baryon scattering with Luscher’s method for N_c = 4 gauge theory. To improve signal in our scattering observables, we employ the Laplacian Heaviside or Distillation method to construct low rank interpolating operators with good overlap with low lying energy states. Though of interest for large N_c QCD studies, the LSD collaboration has been investigating a dark matter candidate...
The dynamics of the glueballs is important in the context of their experimental search as well as for understanding non-Abelian theories. The glueballs of the dark SU(N) Yang-Mills theory are also good candidates of the dark matter [1,2].
The low energy effective Lagrangian of the 0++ glueball may be determined from the interglueball potential calculated on lattice. In this talk, we report on...
Numerical estimation of fermionic observables often requires introduction of auxiliary bosonic fields that have no direct physical relevance through a Hubbard-Stratonovich transformation. The variance of some fermionic observables (for example, appropriately constructed local four-fermion operators in 2d Gross-Neveu model) when they estimated using such auxiliary fields may not correspond to...
We use a regular tessellation of AdS$_2$ based on the (2,3,7) triangle group, with an extension to Euclidean AdS$_3$, to study
the AdS/CFT correspondence. Perturbative calculations are verified and initial tests of monte carlo calculations for
non-perturbative $\phi^4$ theory exhibit critical phenomena on the boundary.
We study the two-dimensional Yang-Mills theory with four supercharges in the large N limit. By using thermal boundary conditions, the distribution of scalars is studied at large N, in the limit of a vanishing scalar potential. We explore the extent of scalar distribution in this theory and look for behavior identical to its maximally supersymmetric cousin, which is known to admit holographic...
Self-interacting scalar quantum field theories possessing PT-symmetry are physically admissible since their energy spectrum is real and bounded below. However, models with PT-invariant potentials can have complex actions in general. Thus, they cannot be studied using methods based on traditional Monte Carlo due to a sign problem. We use complex Langevin dynamics to study two-dimensional...
Composite Higgs models can be extended to the Planck scale by means of the partially unified partial compositeness (PUPC) framework. We present in detail the Techni-Pati-Salam model, based on a renormalizable gauge theory SU(8)×SU(2)L×SU(2)R. We demonstrate that masses and mixings for all generations of standard model fermions can be obtained via partial compositeness at low energy, with...
Among novel strong interactions beyond the standard being currently investigated, the Sp(4) gauge theory with two fundamental and three antisymmetric fermions is compatible with the pseudo-Nambu-Goldstone-Boson (pNGB) mechanism of electroweak symmetry breaking and the implementation of partial top compositeness. Unlike in QCD, the lack of a manifest experimental counterpart and the scarcity of...
We study a four-dimensional lattice gauge theory with fermions transforming as the fundamental and antisymmetric representations of Sp(2N) gauge groups. More specifically, we consider the case of N=2 with two and three Dirac flavors for the fundamental and antisymmetric fermions, respectively, whose continuum limit serves as the microscopic theory for SU(4)/Sp(4) models of composite Higgs and...
We perform dynamical lattice studies for mesonic spectroscopy of Sp(4) gauge theory coupled to three flavours of Dirac fermions in the antisymmetric representation. In addition, mesons composed of valence fundamental Dirac fermions are considered in the partially-quenched setting. We employ the Wuppertal and APE smearing methods to improve the signals of effective masses. By combining the...
Motivated by studies of Composite Higgs models based on the $SU(4)/Sp(4)$ coset on the one hand and by large-$N$ limit investigations on the other, we analyse the quenched meson spectrum of Symplectic -- $Sp(2N)$ -- gauge theories on the lattice. We examine fermions in the symmetric representation of $Sp(4)$; we also study fermions in the fundamental, antisymmetric and symmetric...
$Sp(2N)$ gauge theories are potentially relevant in the context of Composite Higgs Models and provide an alternative sequence to the more widely studied $SU(N)$ and $SO(N)$ groups in the investigation of the large-N limit of Yang-Mills theories.
In this contribution, we report on our study of the scale setting and of the topological features of the vacuum of $Sp(2N)$ lattice (pure) gauge...
We investigate a UV completion of a pseudo-Goldstone Composite Higgs model based on a SU(2) gauge theory with two fundamental flavours of Dirac fermions. The model is based on the SU(4) to Sp(4) chiral symmetry breaking pattern and can be view as a minimal template to explore the phenomenological signatures of Composite Higgs models. To characterize the model, lattice calculations are used to...
Motivated by recent scenarios of exotic infrared behaviour and by earlier lattice findings, we present results for the $\mathrm{SU}(2)$ gauge theory with one Dirac flavor in the adjoint representation. This provides a major update on our previous investigation of this theory, including data for four values of the gauge coupling $\beta$, and for smaller masses and larger volumes than previously...
Many candidate theories for BSM physics involve Yang-Mills gauge fields coupled to scalars. By considering a 'toy model' of a GUT — an SU(3) gauge theory with a scalar 'Higgs' in the fundamental representation — we give analytical reasons to suspect qualitative discrepancies between the spectrum obtained from the conventional perspective of spontaneous gauge symmetry breaking compared to an...
In GUT-like scenarios it is necessary to break the gauge group to the SM-group. This is usually achieved by adding scalars to the theory, which may introduce one or more possible breaking patterns to the theory. Additionally, a valid description of gauge-symmetry-breaking needs to be manifestly gauge-invariant, which is often neglected in standard phenomenology.
In our work we therefore...
The naturalness problem in the Higgs sector finds a popular solution in composite Higgs models. In such theories the Higgs boson emerges as the pseudo-Nambu-Goldstone boson associated with the breaking of a global symmetry realised in a new, strongly interacting sector. In this talk we address a model arising in this context and well motivated by phenomenological arguments, a SU(4) gauge...
In various theories of strongly-interacting dark matter non-degenerate flavors play an important role to satisfy constraints like relic abundance. To quantify the impact we investigate a candidate theory, Sp(4) gauge theory with two fundamental flavors. At the relevant quark mass scales we find interesting patterns in the pseudoscalar and vector channel, which mix behavior from chiral and...
