Models of numerous kinds accept been proposed inward most 130 model builder papers then far that endeavour to explicate the diphoton resonance of invariant majority some \(750\GeV\) seen at the LHC – which may plough out to live a manifestation of novel physics or a fluke.
Tommaso Dorigo is a cynic but I constitute his recent comment amusing, fifty-fifty if it is wrong. He claims that
the \(750\GeV\) bump tin be neither the Loch Ness Monster nor Mickey Mouse, because of some differences inward the shape. Otherwise, the bump tin live anything.
The bump may really live due to Loch Ness as well as Mickey Mouse assuming that both of them cooperate as well as Loch Ness is properly twisted past times the Donald Duck. Dorigo has overlooked that model. More seriously, inward the existent world, the bumps may live existent as well as many of the explanations are feasible if non highly intriguing. I've discussed
sgoldstinos,
radions,
D3-branes as well as closed strings,
sbinos as well as NMSSM, as well as
a few other generic options.
But today, nosotros accept a clear novel winner, the \(E_6\) grand unified theories.
On the hep-ph arXiv, nosotros were shown the outset dose of
new papers submitted inward 2016. There are 84 entries on the hep-ph arXiv today. 33 of them are novel papers primarily classified equally hep-ph articles. I believe that xi of them are dedicated to the novel diphoton resonance: 2, 9, 12, 17, 24, 28-33.
Previously, the total release of hep-ph papers most the resonance was
118 on Dec 29th. I believe that xi were added on Dec 31st but exclusively 2 on Jan 1st. So equally of now, the release of papers should live 118+11+2+11=142 but I promise you lot empathise that it volition live increasingly hard to live whatever for certain most the total release (the papers can't live constitute past times whatever piece of cake reliable "reference"). See
this page amongst a graph as well as hyperlinks claiming that the electrical current release is 146 (thanks, Djack).
At the terminate of the year, I could call a
fun Chilean paper that claims to explicate the patterns inward quark as well as lepton masses, on top of the diphoton resonance, from a scalar amongst a \(\ZZ_{14}\times\ZZ_2\) grouping as well as a novel quark of accuse \(+8/3\); as well as
Ian Low's as well as Joe Lykken's newspaper imposing model-independent bounds on the branching ratios.
But amidst the xi novel papers today, at that topographic point is 1 rather specific sort of models that dominate. 4 out of xi papers (36%) debate that the diphoton resonance may live obtained from the grand unified theories whose estimate grouping is \(E_6\), the exclusively uncomplicated exceptional compact Lie grouping that has complex representations as well as is so conduct feasible equally the estimate grouping of grand unified acre theories. It is non quite a novel category – I've reminded you lot of some \(E_6\) model edifice e.g. inward the context of the
paper [25] here, marketed equally an extension of NMSSM. (Maybe I was the outset 1 to verbalise most \(E_6\) inward the context of the diphoton resonance as well as the novel papers accept copied me – as well as I am non upset at all if that is the case.)
But the "synergy" amongst which the today's authors write most \(E_6\) is sort of remarkable.
The \(E_6\) Dynkin diagram is left-right-symmetric, much similar the \(SO(2N)\) as well as \(SU({}^\geq 3)\) diagrams (\(SO(8)\) has the higher \(S_3\) triality symmetry). This \(\ZZ_2\) symmetry is what exchanges the representations amongst their inequivalent complex conjugate friends. The existence of this left-right symmetry as well as so these complex representations (reps inequivalent to their complex conjugates) is ironically needed to explicate the left-right-asymmetric grapheme of the electroweak forcefulness which is why \(E_6\) is the exclusively exceptional grouping that may live conduct used equally a grand unified estimate group. We are talking most 4 papers
Palti: Vector-Like Exotics inward F-Theory as well as \(750\GeV\) Diphotons
Ko+2: Diphoton Excess at \(750\GeV\) inward leptophobic \(U(1)'\) model inspired past times \(E_6\) GUT
Chao: The Diphoton Excess from an Exceptional Supersymmetric Standard Model
Karozas+3: Diphoton excess from \(E_6\) inward F-theory GUTs
Bonus from terminate of Jan 2016:
King+Nevzorov: \(750\GeV\) Diphoton Resonance from Singlets inward an Exceptional Supersymmetric Standard Model
Three papers amidst the 4 (except for Ko+2) verbalise most the stringy source of these effective acre theories. The outset as well as the lastly 1 explicitly verbalise most F-theory, Vafa's geometric generalized nonperturbative description of type IIB string vacua, piece the 3rd newspaper past times Chao envisions a heterotic string model equally the source (there be heterotic-F-theory dualities then a model may oft accept both descriptions at the same moment).
As I accept previously mentioned, relatively to the 16-dimensional representation for fermions inward \(SO(10)\) grand unified model edifice (the sixteen components include the right-handed neutrino, different the 5+10-dimensional representation inward \(SU(5)\) models), the fundamental representation of \(E_6\) is 27-dimensional as well as decomposes equally \[
{\bf 27} = {\bf 16}\oplus {\bf 10}\oplus {\bf 1}
\] nether the \(SO(10)\) subgroup. The extra 10-dimensional representation behaves equally \({\bf 5}\oplus \bar{\bf 5}\) nether the \(SU(5)\) subgroup. Because nosotros teach both the representation as well as its complex conjugate, it way that the fermions volition transform equally total uniform Dirac spinors nether the \(SU(5)\) group. So the estimate couplings volition live non-chiral i.e. vector-like, equally people telephone phone it. In the Dirac spinor notation, you lot won't quest whatever \(\gamma_5\) to write the Lagrangian for those fields.
The chiral interactions are the cornerstone of the electroweak theory, equally you lot know (only the left-handed fermions as well as right-handed antifermions interact weakly) but to explicate the diphoton resonance, nosotros quest the couplings to the pairs of gluons (initial state) as well as pairs of photons (final state) as well as non-chiral interactions are expert for that.
However, equally most of the 4 papers notice, the novel vector-like quarks interact chirally amongst a novel \(U(1)'\) estimate grouping that arises out of the \(E_6\). At to the lowest degree the outset 2 papers amidst the 4 papers higher upwardly explicate that this is keen because this non-chiral interaction of the novel exotic quarks guarantees that they accept masses linked to the Higgs that breaks this \(U(1)'\) symmetry – which they set unopen to \(1\TeV\). This scale used to live expected to live close the GUT scale instead. The outset newspaper claims that past times reducing this scale, nosotros teach an extra bonus: the proton decay slows down!
Note that inward the original "normal"
2013 TRF text most the basic GUT embeddings.