Strongly interacting dynamics beyond the Standard Model and the Higgs boson

24 Apr 2013, 08:00 → 26 Apr 2013, 14:00 Europe/London

Higgs Centre for Theoretical Physics

Biagio Lucini (University of Wales Swansea), Luigi Del Debbio (University of Edinburgh (GB)), Maurizio Piai (University of Wales Swansea)

This meeting aims at bringing together experts from three different areas of Particle Physics with a common interest in strongly interacting dynamics beyond the standard model as a mechanism of electroweak symmetry breaking. Traditionally, there is little cross-talk among those sectors: phenomenologists focus on experimental data and their implications; model builders start from a theoretical framework and using analytical techniques (derived either from field theory or string theory arguments) work out predictions that can be tested at experiments; finally, lattice gauge theorists use numerical techniques to determine quantitative answers for problems for which conventional analytical methods fail. The main objective of this workshop is to promote a significant advance in the field of BSM strong dynamics by facilitating the synergy among those apparently different but strictly interconnected sub-fields. This workshop is supported by the Higgs Centre, the ESF network Holograv, Swansea University, and the EU network STRONGnet.

Wednesday 24 April

1 Registration

2 Discovering Walking Technicolor at LHC and on the Lattice

Walking technicolor having large anomalous dimension near unity and approximate scale symmetry predicts a light composite pseudo-Nambu-Goldstone boson of the approximate scale symmetry, Technidilaton, which can be identified with the 125 GeV boson discovered at LHC. I will describe how such a weakly coupled light composite scalar can be dynamically realized in the strongly coupled dynamics, and can be fit to the current data in all exclusive channels observed at LHC, based on the ladder-like computation and holographic one. I will also discuss some lattice results performed at our lattice collaboration (LatKMI Collaboration) on some hints of the walking technicolor and a light composite scalar.

Speaker: K Yamawaki

Slides Higgs_Centre_Workshop.pdf Higgs_Centre_Workshop.pptx

3 Holographic techni-dilaton

We construct a bottom-up model for the holographic dual of walking technicolor, which is based on dilaton-deformed AdS_5 geometry, taking into account the back-reaction of the probe brane. We then calculate the dilaton decay constant and its mass to show that the dilaton can be very light.

Speaker: D-K Hong

Slides higgs_hong.pdf

10:30 Coffee

4 Implications of a 125 GeV Composite Higgs

Speaker: A Pomarol

Slides Edinburgh13.pdf

5 The 4D Composite Higgs Model at the LHC

I will propose a four dimensional description of composite Higgs models which represents a complete framework for the physics of the Higgs as a pseudo-Nambu-Goldstone boson capturing all the relevant features of 5D models and more in general of composite Higgs models with partial compositeness. The minimal scenario includes a single multiplet of resonances of the composite sector, as these will be the only degrees of freedom which might be accessible at the LHC. This turns out to be sufficient to compute the effective potential and derive phenomenological consequences of the theory. Moreover this simplified approach is well adapted to simulate composite Higgs models at the LHC. I'll show that the 4DCHM can give an explanation of the 125 GeV Higgs-like signal and provide signatures for the new bosons and fermions foreseen by these scenarios.

Speaker: S De Curtis

Slides Edi24.pdf

12:00 Discussion

13:00 Lunch

6 Anomalous dimension of the chiral condensate from the Dirac-operator spectrum

A strategy for computing the anomalous dimension of the chiral condensate at the fixed point in infrared-conformal gauge theories from lattice simulations is discussed. The method is based on the scaling of the spectral density of the Dirac operator or rather its integral, the mode number. It is relatively cheap, mainly for two reasons: (a) the mode number can be determined with quite high accuracy, and (b) the anomalous dimension of the chiral condensate is extracted from a fit of several observables on the same set of configurations (no scaling in the Lagrangian parameters is needed). As an example the anomalous dimension of the chiral condensate has been computed in the SU(2) theory with 2 Dirac fermions in the adjoint representation of the gauge group. In this particular case, the proposed strategy has proved to be very robust and effective. Old and new preliminary results will be presented.

Speaker: A Patella

Slides patella_higgscenter.pdf

7 Anomalous dimensions of four-fermion operators from conformal EWSB dynamics

(Quasi)conformal scaling of composite operators from a strongly coupled EWSB dynamics helps to produce the characteristic hierarchies exhibited by the flavour couplings of the SM. It is however crucial to ensure that specific models do not violate bounds on BSM flavour dynamics; this in turn requires to control not only the anomalous dimensions of bilinears, but also those of higher-dimensional operators. We report on an ongoing effort to determine four-fermion operator anomalous dimensions, via Schrödinger Functional techniques, in the benchmark of the Minimal Walking Technicolour scenario.

Speaker: C Pena

Slides talk_pena.pdf

8 Large N volume reduction of Minimal Walking Technicolor

I will discuss some numerical simulations of the large N limit of minimal walking technicolor, the SU(N=2) gauge theory with 2 adjoint fermions. Taking advantage of the conjectured volume independence at large N, the lattice simulations are performed on single site, with the end goal being a determination of the mass anomalous dimension of the theory.

Speaker: L Keegan

Slides talk.pdf

15:30 Coffee

9 Improved analysis for running coupling constant for SU(3) gauge theory with 12 flavours

Whether or not the SU(3) gauge theory with 12 flavours is IR conformal remains a controversy. In this talk, we present improved analysis for running coupling constant for this theory in the Twisted Polyakov Loop scheme. Our updated analysis make use of lattice with size up to 24^4. This allows us to control the lattice artefacts in the analysis.

Speaker: D Lin

10 Orthogonal Technicolor with Isotriplet Dark Matter on the Lattice

We study the gauge dynamics of Orthogonal Technicolor on the lattice. It is an SO(4)-gauge theory with two Dirac Wilson fermions transforming according to the vector representation of the gauge group. When used to break the electroweak symmetry dynamically the model leads to a natural dark matter candidate. We determine the lattice phase diagram by locating the strong coupling bulk phase transition line and the zero PCAC mass line. We present results for the spectrum of the theory. In particular, we measure the pseudoscalar, vector, and axial meson masses. The data favour strongly a chiral symmetry breaking scenario over a conformal one.

Speaker: A Hietanen

Slides so4.pdf

17:00 Discussion

Thursday 25 April

11 Towards non-Supersymmetric Seiberg Duality

Speaker: S ABEL

Slides Steve_Abels_Talk.pdf

10:30 Coffee

12 A Simple Holographic Model of the Conformal Window and the Techni-Dilaton

I present a simplified holographic model of chiral symmetry breaking in gauge theory. The chiral condensate is represented by a single scalar field in AdS, with the gauge dynamics input through radial dependence of its mass, representing the running of the anomalous dimension of the qbar q operator. Simple examples display the key elements of the chiral transition out of the conformal window - a BKT/Miransky scaling transition when the infrared value of the anomalous dimension, gamma_m, is tuned to one). The output of the model are the masses of the qbar q scalar meson bound states. I show in an explicit example that if the gradient of the running of the anomalous dimension falls to zero at the scale where the BF bound violation occurs, so that the theory becomes near conformal, then the theory possesses a techni-dilaton state that is parametrically lighter than the dynamically generated quark mass.

Speaker: N EVANS

Slides Evans.pdf

13 Stable D7 embeddings in walking backgrounds

Nonsupersymmetric probe branes play an important role in models of walking technicolor. However, the lack of supersymmetry makes it rather nontrivial to find stable configurations. In particular, the usual kind of embedding, used so far in this context, turns out to have an instability. We describe how to stabilize it by either introducing a certain worldvolume flux or allowing a more general ansatz for the embedding functions.

Speaker: L ANGUELOVA

Slides Anguelova.pdf

12:00 Discussion

13:00 Lunch

14 Challenges in obtaining reliable lattice results near the conformal window

Speaker: K Rummukainen

Slides rummukainen.pdf

15 MWT: Chirally rotated Schrödinger functional scheme

I will discuss preliminary results for our ongoing simulations of the evolution of the coupling constant for the Minimal Walking Technicolor (MWT) model. We use the recently proposed chirally rotated Schrödinger functional scheme, which is free from O(a) lattice artefacts.

Speaker: C Pica

Slides Pica-EDI2013.pdf

16 The gradient flow running coupling scheme

Luscher's recently introduced Yang-Mills gradient flow is adapted to a finite volume setting. A suitable renormalized coupling is then defined which only depends on the linear size of the finite 4-volume. Using step scaling the beta-function of non-abelian gauge theories can easily be measured on the lattice in this new scheme. The ideas are illustrated for SU(3) coupled to N_f = 4 flavors including a careful and fully controlled continuum limit and preliminary results for N_f = 8 flavors.

Speaker: D Nogradi

Slides Nogradi.pdf

15:30 Coffee

17 The sextet BSM model and the Higgs impostor

Speaker: J Kuti

Slides kuti.pdf

18 Conformality and the Higgs

Speaker: E Pallante

Slides Pallante_Conformality&Higgs.pdf

17:00 Discussion

Friday 26 April

19 Phenomenology of Technicolor with a light Techni-Higgs

I will present the LHC phenomenology of Technicolor models in which the TC-Higgs accounts for the recently observed resonance at LHC. I will argue that the couplings of the TC-Higgs to SM fields are of the same order as a SM Higgs and discuss how the interplay between the TC-Higgs and other TC resonances can ultimately help discriminate it from such a SM Higgs.

Speaker: M Frandsen

Slides Frandsen_HiggsCenter.pdf

20 Light Higgs from Technicolor via EW radiative corrections vs precision data

Speaker: F Sannino

Slides Sannino-Higgs-Centre-2013.pdf

10:30 Coffee

21 Higgs couplings and New Physics

I will discuss how signs of new physics may appear in the measurements of the Higgs couplings at the LHC, with a particular focus on the effects arising from a strongly interacting dynamics. I will present a parameterisation of the couplings motivated by New Physics, and briefly discuss the advantage compared to other approaches. The latest CMS/ATLAS results will also be included.

Speaker: G Cacciapaglia

Slides Cacciapaglia_Edi13.pdf

22 LHC data and aspects of new physics

We consider the implications of current LHC data on new physics with strongly interacting sector(s). In particular we consider the effects of new vector mesons arising from strong dynamics. We discuss two example cases: first, the case where the effects of the vectors arise only through their mixing with the electroweak gauge fields and, second, the case where also a direct interaction terms exist. We find that in the case where the new vector states couple with the higgs boson only via non-negligible mixing is ruled out in light of the present data, but direct interactions can compensate and result in a viable model.

Speaker: K Tuominen

Slides Edinburgh_tuominen.pdf

12:00 Discussion

13:00 Lunch