Predictions of a model of weak scale from dynamical breaking of scale invariance

We consider a model where the weak and the DM scale arise at one loop from the Coleman-Weinberg mechanism. We perform a precision computation of the model predictions for the production cross section of a new Higgs-like scalar and for the direct detection cross section of the DM particle candidate

Trinification can explain the di-photon and di-boson LHC anomalies

LHC data show a diphoton excess at 750 GeV and a less significant diboson excess around 1.9 TeV. We propose trinification as a common source of both anomalies. The 1.9 TeV excess can be produced by the lightest extra vector: a $W_R^\pm$ with a gauge coupling $g_R\approx 0.44$ that does not decay into leptons. Furthermore, trinification predicts extra scalars. One of them can reproduce the $\gamma\gamma$ excess while satisfying constraints from all other channels, given the specific set of extra fermions predicted by trinification.Comment: 14 pages, 3 figure

Totally asymptotically free trinification

Motivated by new ideas about the Higgs mass naturalness problem, we present realistic TeV-scale extensions of the Standard Model, into the gauge group SU(3)_L x SU(3)_R x SU(3)_c, such that all gauge, Yukawa and quartic couplings can be extrapolated up to infinite energy. Three generations of chiral fermions and Higgses are needed, as well as some extra fermion.Comment: 15 pages. The ancillary Mathematica file shows a sample of results. v2: final version accepted by JHE

Dynamical generation of the weak and Dark Matter scale

Il lavoro è finalizzato a calcolare le predizioni sperimentali di un modello proposto in Hambye, Strumia, "Dynamical generation of the weak and Dark Matter scale", arXiv:1306.2329 [hep-ph], che abbandona la usuale linea di pensiero mainsteram (secondo cui la supersimmetria protegge la scala debole da divergenze quadratiche alla massa del bosone di Higgs) per esplorare uno scenario nuovo, nel quale le divergenze quadratiche sono ignorate, assumendo che non esistano scale di massa nella Lagrangiana fondamentale. Scopo del modello è generare dinamicamente la scala debole e la materia oscura alla scala debole. A tal fine il modello introduce un nuovo gruppo di simmetria di gauge SU(2) X , un nuovo bosone scalare S e dei nuovi bosoni vettore X: saranno proprio questi ultimi i candidati a rappresentare la materia oscura. In particolare la lagrangiana ha un potenziale differente rispetto al Modello Standard: va sottolineata l'assenza di un termine di massa sia per l'higgs sia per il nuovo bosone scalare; entrambi prendono massa attraverso il meccanismo di Coleman-Weinberg, considerando la teoria ad un loop. Il nuovo potenziale è formato da tre termini quartici: vi sarà il termine quartico dell'higgs, presente anche nel Modello Standard, un termine analogo per il bosone S e un termine di interazione quartica dei due campi scalari. Inoltre, verrà introdotto nella lagrangiana il termine cinetico del nuovo scalare, nonché il termine cinetico dei nuovi vettori. I parametri lagrangiani introdotti sono λS , λH , λHS e gX , e se ne fisserà il valore a partire dai dati sperimentali noti. In particolare verranno usati i dati relativi al valore sperimentale della massa del bosone di Higgs, all'abbondanza di DM nell'universo e all'ampiezza di decadimento del muone. In aggiunta a questo, dato che nel modello avviene la rottura spontanea di simmetria, si dovranno imporre le due equazioni che fissano il valore di aspettazione dei due campi scalari; in questo modo anche essi diventeranno parametri da determinare della teoria. Resta solo un parametro libero, che supponiamo essere gX , quindi tutte le quantità che si calcoleranno andranno studiate al variare di esso. Si studierà infine, l'andamento della sezione d'urto di produzione del nuovo scalare in funzione della sua massa, considerando i bound previsti dagli esperimenti LEP, CMS ed ATLAS, e l'andamento della sezione d'urto di rilevazione diretta per i vettori X in funzione della loro massa, considerando i bound sperimentali di Xenon2012 e LUX2013

Naturalness of asymptotically safe Higgs

We extend the list of theories featuring a rigorous interacting ultraviolet fixed point by constructing the first theory featuring a Higgs-like scalar with gauge, Yukawa and quartic interactions. We show that the theory enters a perturbative asymptotically safe regime at energies above a physical scale $\Lambda$. We determine the salient properties of the theory and use it as a concrete example to test whether scalars masses unavoidably receive quantum correction of order $\Lambda$. Having at our dispose a calculable model allowing us to precisely relate the IR and UV of the theory we demonstrate that the scalars can be lighter than $\Lambda$. Although we do not have an answer to whether the Standard Model hypercharge coupling growth towards a Landau pole at around $\Lambda \sim 10^{40}$ GeV can be tamed by non-perturbative asymptotic safety, our results indicate that such a possibility is worth exploring. In fact, if successful, it might also offer an explanation for the unbearable lightness of the Higgs.Comment: 17 pages. v2: final version; extra argument in the conclusions makes obvious why our claims are correc

Realistic SM extensions valid up to infinite energy

In the last years the colliders could explore a wider range of energies, but the absence of new particles close enough to the weak scale makes the SM more and more un-natural. In a framework where only the physical corrections to the dimensionful parameters are considered and the gravitational interactions are supposed to be weak at all scales, we want to extend the SM with new degrees of freedom at the TeV scale, such that the behavior of the coupling constants at high energy has no Landau poles and it is under perturbative control. We analyzed the Trinification models, that extend the SM gauge group to SU(3)_L x SU(3)_R x SU(3)_c, to find a model where all the couplings go to zero at infinite energy (Totally Asymptotically Free model). We studied the possible signals of the newly introduced particles that are measurable at colliders. We considered a toy model with gauge group SU(N) featuring vector-like fermions and charged scalars: all the couplings approach an interacting fixed point in the Veneziano limit (Totally Asymptotically Safe behavior). We considered the addition of $N_F$ vector-like fermions to the SM: the complete resummation of the corrections at any order in perturbation theory but at leading order in 1/N_F is known. Considering such contributions in the Renormalization Group equations allows the taming of the Landau poles for all the SM couplings while an interacting fixed point arises and the model becomes Totally Asymptotically Safe

Asymptotically safe standard model extensions?

We consider theories with a large number NF of charged fermions and compute the renormalization group equations for the gauge, Yukawa and quartic couplings resummed at leading order in 1=NF. We construct extensions of the standard model where SU(2) and/or SU(3) are asymptotically safe. When the same procedure is applied to the Abelian U(1) factor, we find that the Higgs quartic can not be made asymptotically safe and stay perturbative at the same time