<< Chapter < Page Chapter >> Page >

The solution was to use the DaVinci cluster at Rice to generate the backgrounds by running up to 200 Pythia simulation runs at once. This process generated enough background for 12 t-tbar events and this served as our test set. Unfortunately signal-to-noise ratio in the test set was so low that the logistic regression algorithm in WEKA could not be trained against it – the resulting model failed to detect any t-tbar events at all. Also, training logistic regression on the full test set strained the memory capabilities of the Java virtual machine it was run on, leading to frequent crashes.

To get around this, the author decided to compromise and experiment with training the logistic regression classifier on much smaller training sets with differing ratios of t-tbar events to background events. The performance of the resulting models were then tested on the cross-validation set containing 10,000 of each type of event. The model generated from a training set with a ratio of tt-bar to background events of about 50 seemed to perform the best. (See Table TODO).

Results

As a result of performing the above optimizations, the efficiency of the logistic regression model at analyzing the very large test set improved by over a factor of 30 while only halving the true positive rate, as shown in Table TODO. It is important to note that the false positive ratio is still much too high for top quarks to be discoverable with a data set of this size. Since we are dealing with counting statistics of independent events, the uncertainty in the background count is approximately the square root of the background count, corresponding to a standard deviation of about 13. Since our signal is only 6 t-tbar events, this means we have a signal significance of about 0 . 4 σ . In order to get a statistically significant result, we would need to collect around 150 times as much raw data.

Conclusion

We have demonstrated that we can optimize our use of linear regression to exploit characteristics of a particular particle physics data set. Existing tools like WEKA make using machine learning for this task relatively straightforward, with no need to reinvent the wheel.

It should be noted that this project has neglected the most difficult and computationally intensive part of identifying new physics with particle detectors: modeling the performance of the particle detectors themselves. Modern particle detectors are incredibly complicated pieces of machinery and modeling their capabilities (which change often as components are upgraded) requires a measurable fraction of the planet's computing resources. (ref Grid Computing)

Future work

Dr. Subramanian also suggested that classifier performance could be improved by combining several integer features, namely how many of each type of lepton were found in each event, into one category feature, namely which lepton type was found. This makes sense because the high-level trigger eliminates all events that do not have exactly one lepton. A simple script should be able to transform all of the existing data to make this possible.

References

WEKA PythiaParticle physics book

h t t p : / / w w w . r e a d w r i t e w e b . c o m / a r c h i v e s / c e r n o f f i c i a l l y u n v e i l s i t s g r . p h p

Acknowledgments

The author would like to thank Dr. Paul Padley and Dr. Devika Subramanian for providing advice and training for this project, as well as Dr. Andrew Ng for his excellent and fun on-line machine learning class.

Directions for using code

Install Pythia 8 and WEKA on your UNIX machine. The included scripts and Makefile assume that the WEKA classes are in /usr/share/java/weka.jar and that the directory containing the code and data files is located in the pythia directory. See the included README file for more details.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
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
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Introductory survey and applications of machine learning methods' conversation and receive update notifications?

Ask