Stringy origin of diboson and dijet excesses at the LHC

Luis A Anchordoqui,Ignatios Antoniadis,Haim Goldberg,Xing Huang,Dieter Lüst,Tomasz R Taylor

doi:10.1016/j.physletb.2015.08.033

Abstract

Very recently, the ATLAS and CMS Collaborations reported diboson and dijet excesses above standard model expectations in the invariant mass region of 1.8–2.0 TeV. Interpreting the diboson excess of events in a model independent fashion suggests that the vector boson pair production searches are best described by WZ or ZZ topologies, because states decaying into W+W− pairs are strongly constrained by semileptonic searches. Under the assumption of a low string scale, we show that both the diboson and dijet excesses can be steered by an anomalous U(1) field with very small coupling to leptons. The Drell–Yan bounds are then readily avoided because of the leptophobic nature of the massive Z′ gauge boson. The non-negligible decay into ZZ required to accommodate the data is a characteristic footprint of intersecting D-brane models, wherein the Landau–Yang theorem can be evaded by anomaly-induced operators involving a longitudinal Z. The model presented herein can be viewed purely field-theoretically, although it is particularly well motivated from string theory. Should the excesses become statistically significant at the LHC13, the associated Zγ topology would become a signature consistent only with a stringy origin.

Highlights

Very recently, searches for narrow resonances at the ATLAS and CMS experiments uncovered various peaks in invariant mass distributions near 2 TeV: (i) The ATLAS search for diboson production contains a 3.4σ excess at ∼ 2 TeV in boosted jets of W Z [1]
Many of the events can be explained by a Z Z or W W
∼ 1.8 TeV [3]. (iii) The CMS search for dijet resonances finds a 2.2σ excess near 1.8 TeV [5]. (iv) Around the same invariant mass ATLAS recorded an excess in the dijet distribution with a 1σ significance [4]. (v) The CMS search for resonant H W production yields a 2.1σ excess in the energy bin of 1.8 to 1.9 TeV; here the Higgs boson is highly boosted and decays into bb, whereas the W decays into charged leptons and neutrinos [6]

Summary

Stringy origin of diboson and dijet excesses at the LHC

None of the excesses is statistical significant yet, it is interesting to entertain the possibility that they correspond to a real new physics signal On this basis, with the assumption that all resonant channels are consistent with a single resonance energy, a model free analysis of the various excesses has been recently presented [7]. We assume that the source of the excesses originates in the decay of a new abelian gauge boson that suffers a mixed anomaly with the SM, but is made self-consistent by the Green–Schwarz (GS) mechanism [13] Such gauge bosons occur naturally in D-brane TeV-scale string compactifications [14], 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 [15]. The anomalous mass growth allows the survival of global baryon number conservation, preventing fast proton decay [22]

The content of the hypercharge operator is given by

Xμ gY

GF is the

MZ TeV

The last two terms in the covariant derivative

2YμY μ