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Events which contain the desired t-tbar events are inevitably accompanied by a much larger number of undesired background events. The vast majority of these events initially involve the creation of much lighter quarks – these are called “QCD" events, named after the theory that describes the behavior of these particles, quantum chromodynamics. QCD events are several million times more common than t-tbar events at the energies presently used at the LHC. A minority of background events involve the creation of W bosons. Although these W events are rarer, occurring at the rate of “only" a few hundred per t-tbar event, their detectable features are very similar to those of t-tbar events and are thus they are harder to distinguish from the desired t-tbar signal.

Prior work - phys 491 summer 2011

The author initially got started investigating this classification problem as part of an independent study course taken with Dr. Paul Padley. Dr. Padley works at Bonner Lab at Rice University and is manager of the Endcap Muon Subdetector, a large component of the Compact Muon Solenoid (CMS) experiment at the LHC. The course involved learning background about particle physics necessary to be able to understand the classification problem.

The strategy over the summer was to figure out how to use a popular event generating program called Pythia in conjunction with a popular machine learning toolkit called WEKA. The author wrote a small program in C to interface with Pythia to generate a large number of t-tbar, W, and QCD events. The C program ran the events through a simple filter, a “trigger" in physics parlance, to quickly eliminate a large number of events that had a relatively low probability of being t-tbar events. (The trigger filters out 95% of t-tbar events, but 99.9% of the QCD background events.) Sufficient data was collected to form a training data set and a test data set; each set had 10,000 of each type of event.


When Pythia generates an event, it makes available a wide array of information useful for generating features. The chosen features for use in this project included how many of each type of lepton (electrons, muons, and tau particles) were created in each event, how many “jets" corresponding to quarks were generated, and the minimum angle between any pair of quark jets. In addition, missing transverse momentum, indicative of an invisible neutrino, was measured. Finally, the total transverse energy (energy perpendicular to the beam axis) of all of the quark jets was measured. A large transverse energy is strongly associated with “head-on" collisions capable of releasing enough energy to make top quarks. “It turns out" that transverse energy is the most important single feature for identifying top quarks.


Because of the author's lack of experience with machine learning, a script was developed that ran each of the classifiers in WEKA against the training data and extracted the relevant statistics. Each of the classifiers was run with default parameters. For each classifier, the number of t-tbar events that were correctly identified (true positives) was determined, as well as the number of QCD and W events that were misclassified as t-tbar events (false positives.) From the ratio of these numbers and the cross-sections of the relevant pathways, it was possible to determine the total beam luminosity needed to confirm the existence of top quarks in a set of events using each classifier.

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Introductory survey and applications of machine learning methods. OpenStax CNX. Dec 22, 2011 Download for free at http://legacy.cnx.org/content/col11400/1.1
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