My project starts by investigating the difference, if any is
discernable from the plots I produce, between
SM Higgs processes and Higgs processes in the Minimally Symmetric Standard Model. To read more without
a small primer into the usage of Root/Pythia (which follows below), go directly to the page dealing with
this task. There's close to no question about the Higgs existence at this junction, but there is also no question that
high-energy phycisist, a group of which I loosely consider myself a member, most often long for the small
hint that the entire theory is somehow proven to be wrong, no matter how correct it appears: whether it be
quantum gravitational effects, novel particles, an expected Higgs or the expected supersymmetric partner
of any SM particle, the general feeling is that the field needs something completely novel.
During summer of 2016 there was a
hint at a bump in the detectors
at the ATLAS experiment
, hinting at something
unknown at a time when the the SM was considered complete. The 3 months following this event -- the hint
that there might be a particle at the given energy -- generated in excess of 300 papers from theoretical
That is to say there is no lack of imagination and playfulness on
the part of the hig energy particle theory
community. This page is dedicated to that work; here, I toy with some of the models. I start with the MSSM,
and for this I will simulate proton-proton events using Pythia as a plug-in to Root. I choose
the MSSM because it is the theory in accordance with Occam's razor: its predictions are in many respects
tantamount to the SM, with at least one particle corresponding to the already measured Higgs particle,
with the least amount of fluff.
In addition, I will attempt to play around with Les Houches Accord
Files, to familiarize myself with the system further.
With these files, settings are imported from outside Pythia itself, and incorporated into Pythia's settings and possibly
expand upon the possible reactions, particles, etc. For this purpose I will toy around with heavy flavour physics.
Pythia is an excellent framework for simulation of reactions at the
LHC. There are several process switches
flipped on during configuration (at least one must be switched on), including soft and hard QCD, electroweak,
and for the purposes of the first project, production of Higgs particles. One may choose to use the couplings as
predicted by the SM, or the MSSM, the latter of which allows for user settings on each individual coupling. I
will use all couplings equals to unity, given one must set all if one turn of the MSSM couplings. I pass the
switches "Higgs:useBSM = on" and "HiggsBSM:all = on" to TPythia8::ReadString() and use
TPythia8::Initialize(2212, 2212, 7000, 7000) to initialize to 14 TeV and pp-collisions
(protons have particleId = 2212).
Making a few pointers to some histograms to display some information
about the reaction in question, and
making a pointer to a location in memory at which the final state particles are stored, an event-loop is constructed,
in which an event is generated (TPythia8::GenerateEvent()), the list of particles is traversed, particle properties
are extracted from the particle database and filled into the histograms using TH1*::Fill().
The plots below show the multiplity and pseudorapidity of
final state particles in 1000 pp-collision at 14TeV; the plots
are print by calling TPad::Print().,
The macro I used to generate the plots can be viewed on this page.