Friday, December 04, 2015

Dijet carnage: CMS shoots 20% more resonances

Today, a group of 3,000 gunmen known as the Carnage Master Sect (CMS) simultaneously entered the Large Hadron Collider and the arXiv of preprints and completed their
Search for narrow resonances decaying to dijets in proton-proton collisions at \(\sqrt{s} = 13\TeV\)
Tiziano Camporesi, the spokesman of the group (who met his predecessor Joe Incandela in the Italian Mafia), began with the scream "Standard Model Akbar".

The men and some women were equipped with 2.4 inverse femtobarns of ammunition produced in 2015; this translates to some 200 or 300 trillion pairs of protonic bullets. Among the CMS' fans, there were worries about the CMS magnet but most of the 2015, it apparently wasn't able to prevent CMS from shooting and looking at jets because most of the 4 delivered inverse femtobarns were transformed into real data.

When the CMS infiltrated CERN, they looked behind every corner in order to find all possible victims (the CMS holy text instructs the members to kill every resonance except for the only true and merciful \(125\GeV\) God particle before they see it). Even though the amount of ammunition they had was 10 times lower than the amount of lower-energy ammunition during their previous 2012 attack, everyone whose weight was between \(2\TeV\) and \(7\TeV\) was at a significantly higher risk than she was in 2012 that she would be gunned down.

At the end, there were lots of casualties. The victims may be organized into the following groups:
  • heavy \(W'\) bosons up to \(2.6\TeV\), higher than ATLAS' 2012 \(2.45\TeV\)
  • color octet scalars up to \(3.1\TeV\), ... \(2.7\TeV\)
  • excited quarks up to \(5\TeV\), ... \(4\TeV\)
  • axigluons+colorons up to \(5.1\TeV\), ... \(3.6\TeV\)
  • scalar diquarks up to \(6\TeV\), ... \(4.7\TeV\)
  • string resonances up to \(7\TeV\), ... \(5\TeV\)
Condolences to all the victims' relatives because they may become victims next time. Most of us didn't expect any new discoveries except for a chance for the new gauge bosons. Among gauge bosons, there were beliefs that there could be survivors especially among \(W'\) bosons at \(2\TeV\) and \(Z'\) bosons at \(2.9\TeV\). Those are "somewhat alive" after the CMS new contributions – because those particles require more luminosity and the number of events at \(2\TeV\) is still "slightly higher" than the average. It's the other channels (not dijets) that should see the new gauge bosons more clearly but my belief in those bosons' survival has decreased, too.

You may see that the limit on stringy resonances has increased by whopping 40%. Most likely, the mass of string resonances is close to \(10^{16}\GeV\) and the LHC cannot ever see them.

I am also puzzled by the highest dijet energy. ATLAS has shown the pictures of a \(8.8\TeV\) dijet in the first inverse femtobarn of the 2015 data. The CMS has analyzed twice as much and today, we learned that their highest dijet mass was only \(6.1\TeV\). This looks like a huge difference, \(2.7\TeV\), especially because the cross section seems to decrease almost by an order of magnitude for each \({\rm TeV}\) of increased mass. Hasn't ATLAS seen just some illusion?

At this moment, CMS is the king of the organized crime. The Al-Qaeda's Toroidal LHC AparatuS (ATLAS), a competitor of CMS among the armed groups, will try to recapture its hegemony later.

However, we're all sad about the victims and I tend to feel that the CMS will not find anything in the dijet data in the next year, either. Note that "dijets" may only arise from particles that are sufficiently neutral and don't carry any special conserved charged or quantum numbers. In particular, superpartners more or less can't decay to dijets because they carry the "special" negative R-parity. After this carnage, the conditional probability that SUSY will be the next discovered physics at the LHC has increased further, along with the probability that the LHC will discover nothing beyond the Standard Model at all.

No comments:

Post a Comment