Glimpsed particles that the LHC may confirm

The LHC is back in business. Many of us have watched the webcast today. There was a one-hour delay at the beginning. Then they lost the beam once. And things went pretty much smoothly afterwards. After a 30-month coffee break, the collider is collecting actual data to be used in the future papers at the center mass of \(13\TeV\).

See also Juan Rojo's list of anomalies, updated January 2016, and search e.g. for LHC excess on this blog.

So far, no black hole has destroyed the Earth.



It's possible that the LHC will discover nothing new, at least for years. But it is in no way inevitable. I would say that it's not even "very likely". We have various theoretical reasons to expect one discovery or another. A theory-independent vague argument is that the electroweak scale has no deep reason to be too special. And every time we added an order of magnitude to the energies, we saw something new.




But in this blog post, I would like to recall some excesses – inconclusive but tantalizing upward deviations from the Standard Model predictions – that have been mentioned on this blog. Most of them emerged from ATLAS or CMS analyses at the LHC. Some of them may be confirmed soon.




Please submit your corrections if some of the "hopeful hints" have been killed. And please submit those that I forgot.

The hints below will be approximately sorted from those that I consider most convincing at this moment. The energy at the beginning is the estimated mass of a new particle.

• the locally 4-sigma excess at \(750\GeV\) in the diphoton channel of both ATLAS, CMS will become the by far most celebrated anomaly and will emerge in December 2015. This blog will contain a dozen of blog posts about the models to explain this "cernette" particle. Around June 20th, 2016, rumors will start to spread that the excess in 2015 data wasn't repeated in 2016
• \(2\TeV\), a new charged \(W'\) boson suggested by an ATLAS \(WZ\) channel, 3.4 sigma locally, 2.5 sigma globally
• \(2.1\TeV\), a new charged \(W_R\) boson suggested by a CMS \(\ell\ell q\bar q\) channel, 2.8 sigma. May it be the same particle as the one in the previous entry? A possible fast route to left-right-symmetric models and \(SO(10)\) or \(E_6\) grand unification
• \(5\TeV\), a heavy particle decaying to two jets, CMS in both cases, one \(5.15\TeV\) event in 2012 and one \(5\TeV\) in early 2015
• \(79\GeV\), a superpartner-related invariant mass in edge, CMS' dileptons, 2.6 sigma
• \(90\GeV\), a mass difference, Z-peaked excess, ATLAS, 3 sigma, perhaps a sign of NMSSM or MSSM
• \(650\GeV\), sbottom in R-parity-violating SUSY or leptoquark, CMS in \(\ell q\) decays, 2.4 sigma
• unknown mass, probably due to new Higgses, flavor-violating Higgs decays \(\mu^\pm \tau^\mp\) at CMS, 2.4 sigma (1% of Higgses seem to decay in this weird way)
• \(1.85\TeV\), a triplet or littlest Higgs, CMS' \(WH\) resonance, 2.9 sigma
, see also Dorigo's new text
• \(830\GeV\), a sgluon (scalar superpartner of gluon), ATLAS in \(tt\bar t\bar t\) channel, 2.5 sigma
• \(105\GeV\), ATLAS' like-sign dimuons, Christmas 2012 rumor, 14 events
• \(105\GeV\) invariant mass, CMS may confirm ATLAS' same-sign dimuons \(\mu^\pm \mu^\pm\), several sigma; cool update: note that CERN's DELPHI in 2000 saw a dimuon excess near \(100\GeV\), see the last page
• unknown mass, an LHCb penguin excess in \(B\)-meson decays, 3.7 sigma
• unknown mass, an LHCb flavor anomaly
• \(560\GeV\), a CP-odd Higgs boson \(A\), CMS' \(\ell\ell b\bar b\) channel, 2.6-2.9 sigma; see also another pair of CMS excesses at mass \(286\GeV\) with 2.6/1.6 sigma locally/globally and \(662\GeV\) with 2.85/1.9 sigma locally/globally
• \(136.5\GeV\), a CP-even neutral Higgs boson, another one, CMS \(\gamma\gamma\), 2.93 sigma
• \(144\) or \(145\GeV\), extra Higgs boson, over 3 sigma from 4 experiments combined in 2011, a broad excess, see also an October 2015 preprint
• \(325\GeV\), another CP-even Higgs boson, CDF's 4 leptons
• \(320\GeV\), another CP-even Higgs boson, perhaps the same as the previous entry, CMS, 2 sigma
• below \(200\GeV\), higgsino, CMS trileptons or tetraleptons, 2.6 sigma; see another higgsino excess text from CMS
• \(1600\)-\(1650\GeV\), effective mass, ATLAS \(\ell b\bar\,{\rm MET}\)
• unknown mass, CMS' top+higgs+dileptons, 2.5 sigma
• unknown mass, stops or sbottoms or staus, CMS' multileptons with \(\tau\), 2 sigma or so
• unknown mass, ATLAS' 1 lepton and 7 jets, 4 sigma; more multijets and ATLAS' multileptons with more similar links
• \(98\GeV\), another Higgs boson, LEP
• \(300\)-\(600\GeV\), top squark, ATLAS, 2.5 sigma; see also ATLAS' top partners
• \(700\GeV\), a shadron, long-lived particle, CMS' HCSP, 2 sigma
• \(WW\) excess is dead now, I think, much like \(h\to\gamma\gamma\) excess
• unknown mass, multimuon ghost events at CDF, 9 sigma

I omitted LHC hints older than November 2011 but you may see that the number of possible deviations has been nontrivial.



The most accurate photographs of the Standard Model's elementary particles provided by CERN so far. The zoo may have to be expanded.

Stay tuned.