1. JUAN CARDENAS - PHYSICS MAJOR
NIGMS RISE SCHOLAR
Juan CardenasCSUDH
Evidence for Λp Elastic
Scattering in the CLAS Detector
Cal State University, Dominguez Hills
Hadronic Structure Laboratory
Mentor: Dr. John Price
2. OUTLINE
Juan CardenasCSUDH
Λp Scattering Motivation
Previous Data
Data mining g12
Skimming
Data Analysis Methods
Results
Future Plans
6. PROTON STUDY
Juan CardenasCSUDH
γp→γp
Proton interacts via
EM + Strong force
K+, π+, Ko, π-
p, Λ, Ξ
But.. other particles don’t
live long..
Κ
Λ
Ξ
Σ
π
n
p
8. PHYSICAL EXPERIMENT
Juan CardenasCSUDH
Data mining on g12
1 of 2 with long target
40cm LH2
Energy 3.6 – 5.4GeV
Well suited
Large acceptance
(Spherical shape)
10. Data Skim/Data Selection
o Look for 2 protons
o Apparent Baryon
# violation =
Rescattering
Signal
o 126TB -> 17GB
• Reconstruct
scattered Λ
Juan CardenasCSUDH
Apparent Baryon Number
Violation
126 TB
17GB
13. Implications
1:Brought Lambda
beams to Nuclear
Physics.
2: Twice the world
sample in 750Mev – 2.5
GeV range (p)
3: Data points
Error bars
Juan CardenasCSUDH
14. Special Thanks!
Juan Cardenas
Dr. John Price
CLAS collaboration
Jefferson Lab
NIGMS-RISE Program
NIH
Colleagues at CSUDH
CSUDH
16. FUTURE
Juan CardenasCSUDH
Cross Section Requires
Clean up background for
exact # of events
Find effective path length
PAC proposal
• Dedicated experiment for
Λ beam
17. Works Cited
Juan Cardenas
Scattering Cross-section Graph
http://pdg.lbl.gov/2015/hadronic-xsections/rpp2014-
lambdap_sigmap_gp_gd_gg_plots.pdf
Picture of CLAS Detector
http://slideplayer.com/slide/1371778/
Picture of Real Detector
https://www.google.com/search?q=CLAS+detector&espv=2&biw=1280
&bih=705&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjepZXerMbL
AhVL9GMKHaolA4oQ_AUIBygC#imgrc=jx78kxI3wJ-gJM%3A
PROTON
https://en.wikipedia.org/wiki/Proton#/media/File:Quark_structure_pr
oton.svg
Neutron
https://en.wikipedia.org/wiki/Neutron#/media/File:Quark_structure_
neutron.svg
CSUDH
18. Works cited Cont.
Juan Cardenas
(Funnel pic)
https://41perspectives.files.wordpress.com/2013/07
/funnel-diagram-powerpoint2.jpg
CSUDH
19. Probability of Scattering in G12
Juan Cardenas
Given our parameters how often should Λp→ Λp
happen?
NLp » 4700events
NLp = NL ×ctL ×rLH2
×
NA
AH
×sLp
NLp =(26,000,000)×(7.9cm)×(.071
g
cm3
)×(
6.02´1023
1.008g
)×(20´10-27
cm2
)
NLp =175,000
NLp =175,000´.50´.054
CSUDH
20. Acceptance Rate
Juan Cardenas
CLAS has a 60% acceptance for positively-charged
particles
50% acceptance for negatively-charged particles
Accounting for detected particles [K+π - p p]
(0.6 *0.5 * 0.6 * 0.6) = 0.108 = 10.8%.
Half of K+ Decay before hitting detector
0.108 * 0.5 = 0.054 = 5.4 %
CSUDH
Editor's Notes
Lambda reconstruction is the method that we used to try and determine the scattering process. What we did was take the four momentums of the pi minus and one of the protons, take this one for example, and added them do see if their paths intersected and observed the mass of the particle they decayed from.
(Click)
The plot we obtained showed a very tall peak at 1.115GeV/C^2 telling us that the particle was indeed
(Click)
a lambda.
We are now ready to determine if scattering took place. (Click) We, again trace back the paths of the particles, this time the proton and the lambda, to see if their paths intersected. From here we created a mass plot of the particle that created them. If this particle turns out to be a lambda then this means that elastic scattering has been taken place. This plot is what we had been looking for.
After creating the mass plot, (Click) what do you know, after 2 years of mistakes and hard work, we got it, evidence for lambda elastic scattering in the CLAS detector.
Given that CLAS is not designed to detect these types of events, we did not expect this good of a result. The number of detected particles here is estimated to be about 2000. This is about twice the world data sample! In other words, twice as much as anyone has ever detected, combined.
What these findings have done is bring hadron beams to the world of nuclear physics; all previous measurements of the cross section using hadron beams have been done by particle physicists. We are the first to show evidence of one in the context of a nuclear physics experiment.
Also with the amount of events we have observed we can potentially 1) increase the amount of data points on this plot and 2) reduce the size of the error bars for the points that exist within this window here, this is the momentum range of the incoming or (beam lambda).
So where do we go from here.
What we plan to do next is find some values that are crucial to calculating the cross section.
These are finding the exact number of beam lambdas
And finding their effective path length,
(This is basically how far the lambdas travel before colliding with another proton)
Also as of now, we are in the process of writing a research proposal for the construction of an experiment dedicated to detecting these scattering events.
