LHC phenomenology and cosmology of string-inspired intersecting D-brane models

Abstract

We discuss the phenomenology and cosmology of a Standard-like Model inspired by string theory, in which the gauge fields are localized on D-branes wrapping certain compact cycles on an underlying geometry, whose intersection can give rise to chiral fermions. The energy scale associated with string physics is assumed to be near the Planck mass. To develop our program in the simplest way, we work within the construct of a minimal model with gauge-extended sectorThe resulting U (1) content gauges the baryon number B, the lepton number L, and a third additional abelian charge I R which acts as the third isospin component of an SU (2) R . All mixing angles and gauge couplings are fixed by rotation of the U (1) gauge fields to a basis diagonal in hypercharge Y and in an anomaly free linear combination of I R and B − L. The anomalous Z ′ gauge boson obtains a string scale Stückelberg mass via a 4D version of the Green-Schwarz mechanism. To keep the realization of the Higgs mechanism minimal, we add an extra SU (2) singlet complex scalar, which acquires a VEV and gives a TeV-scale mass to the non-anomalous gauge boson Z ′′ . The model is fully predictive and can be confronted with dijet and dilepton data from LHC8 and, eventually, LHC14. We show that M Z ′′ ≈ 3 − 4 TeV saturates current limits from the CMS and ATLAS collaborations. We also show that for M Z ′′ 5 TeV, LHC14 will reach discovery sensitivity 5σ. After that, we demostrate in all generality that Z ′′ milli-weak interactions could play an important role in observational cosmology. Finally, we examine some phenomenological aspects of the supersymmetric extension of the D-brane construct. * On leave of absence from CPHT Ecole Polytechnique, F-91128, Palaiseau Cedex.

Vacuum stability of Standard Model++

“…Achieving the stability will necessarily impose constrains on physics beyond the SM. Very recently we have put forward a (string based) Standard-like Model [25]. Motivated by the above, here we study the vacuum stability of its scalar sector.…”

Production of light stringy states

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23]), Kaluza Klein states (see, e.g. [24][25][26][27][28][29][30]), or purely stringy signatures (see, e.g.…”

Right-handed neutrinos as the dark radiation: Status and forecasts for the LHC

“…The other gauge boson is coupled to an anomaly free current and therefore (under certain topological conditions) it can remain massless and grow a TeV-scale mass through ordinary Higgs mechanisms [39]. We consider two extreme possibilities in which the TeV-scale Z ′ gauge boson is mostly I R or mostly B − L. The chiral couplings (g i ) of these gauge boson are tabulated in [37]. We also consider a D-brane construct with TeV-scale string compactification (the chiral couplings of this model are given in Table IV of [38]).…”

“…Contact with gauge structures at TeV energies is achieved by a field rotation to couple diagonally to hypercharge Y . Two of the Euler angles are determined by this rotation and the third one is chosen so that one of the U (1) gauge bosons couples only to an anomaly free linear combination of I R and B − L [37]. Of the three original abelian couplings, the baryon number coupling is fixed to be 1/6 of the QCD coupling at the string scale.…”