DOE ESSAY 1: PERSONAL STATEMENT



DOE ESSAY 1: PERSONAL STATEMENT

Your personal statement should be a concise, well-written essay describing your academic studies and other relevant experiences in science, engineering, or mathematics and how these experiences have prepared you to pursue graduate study and research in the field you have chosen. The statement should include any notable coursework, research activities, participation in local, regional, or national scientific professional societies, and work experience. Your statement should also provide information illustrating your ability to work independently as well as in teams and demonstrating leadership or involvement in scientific and technical activities.

In describing the scientific research activities in which you have participated—whether through undergraduate research, a research internship, or other academic or job-related research—please provide an account of the purpose of the research, the nature of your contributions, and what knowledge and skills you acquired as a result. If you have not had research experience, describe any activities (courses, job-related work, etc.) you believe have prepared you for graduate research.

State your broad career goals and objectives. Describe how graduate study and research in the field you have chosen contributes to your broader career goals and objectives; how the DOE Office of Science Graduate Fellowship will enable you to achieve your goals; and how your career goals and objectives contribute to the mission areas of the DOE Office of Science.

FIRST DRAFT ESSAY 1:

Several years ago, I completed a bachelors and masters degree in mathematics, which also included enough coursework in physics to qualify me for an engineering physics major. I had elected to continue on to the master’s degree as I had finished my undergraduate degree a year early and wished to further my studies before beginning a career path. While working on the master’s degree, I taught sections of precalculus and calculus. I enjoyed teaching mathematics, and so decided to pursue a teaching career with an eye towards possible research in the future.

After completing my studies I took a position in 2003 teaching high school mathematics at the University School of Nashville. The school gave me the flexibility to develop curriculum, and in my second year working there, I gave a presentation on a financial debt analysis project that I developed with another teacher at the 2004 TenesseeTennessee Association of Independent Schools conference.

In the summer 2006 I participated in a research experience for teachers program where I assistedhelped Victoria Morgan, a researcher at Vanderbilt University, with her work on the detection of diseased neurological tissue in epileptic patients using functional MRI technology. I learned the software analysis tools and contributed a few simple scripts of my own to the project. To culminate the experience, I wrote a lengthy curriculum module to teach magnetism at the advanced placement level using MRI safety as a motivating application of the theory. This module has since been published on the website, a project of the National Science Foundation.

After the research project, I began teaching advanced placement physics and used the curricular module that I had designed. My students were very successful in the course, with over 90% scoring the highest grades of 4 or 5 on the AP Physics C exam. Although I was enjoying my career as a high school teacher, I felt increasingly drawn to research, and my recent change in focus from mathematics to physics convinced me that I should begin work in a new field. I then applied to the graduate physics program at Vanderbilt University and was accepted for the 2008-09 school year.

Ever since I was a child I have been interested in the fascinating world of subatomic particles, often looking at encyclopedia articles of exotic concepts such as quarks and gluons. I therefore knew that I would wish to work in the field of high energy nuclear or particle physics. I believed Vanderbilt University to be a good match for me based on prior research experience, but more importantly, the existence of two research groups involved with the Large Hadron Collider (LHC) Experiment.

Last December our relativistic heavy ion group had an opening for a graduate student to work on the Compact Muon Solenoid (CMS) experiment at the LHC, which I eagerly accepted. After joining, I set to work on learning the simulation, event reconstruction, and analysis software for the detector. As the primary focus of the CMS collaboration is to explore the physics of proton-proton collisions, many modifications need to be made to the software in order to correctly simulate, reconstruct, and analyze the products of collisions between lead nuclei. This is primarily due to the sheer number of particles produced in the collision, which increases the noise background into the detector subsystems and, tends to as well as overwhelm many algorithms used in the standard event reconstruction process.

After joining the CMS collaboration, I learned how to produce and reconstruct simulated events using the detector software using the complex CMS software framework CMSSW. I have also familiarized myself with the Advanced Computing Center for Research and & Education (ACCRE) facility at Vanderbilt, which hosts a computer cluster of over 1500 processor cores. I have written Ppython and perlPerl scripts to submit and manage large-scale jobs that to simulate and reconstruct hundreds of collisions simultaneously on the ACCRE cluster. Although I have little formal training in computer programming, it has been a serious hobby of mine for years, and I have found my experience with linuxLinux, C/C++, perlPerl, network administration, computer repair, and even web development to be invaluable for my research.

This summer, I traveled to CERN to better learn one of the new CMSSWthe software analysis packagestools, called the Physics Analysis Toolkit (PAT), from the developers at the project. These tools had been adopted by many physics interest groups within the collaboration, but had not yet been evaluated by the heavy ion group. After learning to use the software, and working on adapting it to heavy ion collisions, I presented my work to the CMS heavy ion group in general collaboration meeting,a presentation demonstrating the use and capabilities of the tools. After my presentation, the CMS HI groupwe voted to adopt this toolkit as our official analysis software package. I have since been helping with the development and documentation of the application of this package to heavy ion events.

In addition to my work with the software tools, I have been very active in the development of a CMS computing center at Vanderbilt, aiding in the testing of systems such as the high-speed internetInternet connection to CERN as well as the proposed tape backup system. A major related project has been to specifically define our computer hardware needs. , and Ffor that project I have been producing detailed plots of timing and memory usage for the variousdifferent software tasks on a per event basis, using different settings for the tasks of reconstruction and simulation. Additionally, I have been looking closely at the size of our event files on disk, and developed explanatorying charts depictingshowing the relative sizes of the various contentsdifferent data components of the files.

As I have truly enjoyed my work in CMS so far, my career objective is now to obtain my PhD and to eventually teach at a university where I may continue to actively work on relativistic heavy ion research. The Office of Science graduate fellowship will greatly enhance my ability to pursue this researchresearch, as the funds will allow me to travel to additional conferences and to focus all of my energy directly on my work with CMS.

ESSAY 2: PROPOSED PLAN OF RESEARCH

In a clear, concise, and original statement, describe a complete plan for a research project that you will pursue during the tenure of your fellowship. If you are not currently enrolled in a graduate program and have not determined your thesis/dissertation research topic, describe a complete plan for research on a topic that is of interest to you and relevant to the course of study you plan to pursue as a graduate student.

The research topic should be relevant to one or more of the six DOE Office of Science research programs.

The proposed plan of research should include:

* A title

* Introduction and objectives

* Background and significance

* Research design and methods

* References

The proposed plan of research statement should describe how the proposed research is novel or has the potential to make meaningful contributions to the forefront of the research field. The statement should identify the scientific or technical challenges associated with the problem or question and how the proposed methodology or approach is appropriate. If your proposed methods include use of any of the DOE Office of Science scientific user facilities, please include the name(s) of those facilities. .

The statement should also explain how the proposed research is relevant to the DOE Office of Science.

References should be inserted in the separate text box provided.

FIRST DRAFT ESSAY 2:

MEASURING ANISOTROPY IN PIONS AND ETAS, AND DISCRIMINATING CHARM AND BEAUTY IN SQRT(S) = 4 TEV LEAD-LEAD COLLISIONS

[You should put in the section headings (Introduction …, Background …, Research design …, References) as indicated in the instructions, ahead of the related paragraphs. You should add sentences in the paragraphs which point out DOE-NP’s commitment to the LHC research and that this work will serve to advance that DOE mission. ]

I plan to continue to work with the Compact Muon Solenoid (CMS) collaboration at the Large Hadron Collider (LHC) to constrain advance our understanding of the properties of high temperature nuclear matter known as the quark-gluon plasma (QGP). [needs reference to RHIC work, for example the PHENIX White Paper]

When heavy nuclei are collided at extremely high energy, the nucleons are thought to break down into their constituent partons, namely quarks and gluons, and thus for a brief instant forms a finite size medium with many of the predicted properties of the QGP. An understanding of this medium will enhance fundamental knowledge about nuclear and particle interactions, and will help constrain our understanding of the birth of the universe, as a form of QGP is thought to be the dominant state of matter in the first few milliseconds of the big bang.

The QGP is a strongly interacting medium, so a colored particle traversing the medium at high momentum is expected to quickly lose a significant fraction of its energy until it reaches thermal equilibrium with the medium. This effect, called jet quenching, is considered an important signature of the QGP state. In a heavy ion collision, if a QGP is formed, then one should expect that particles with a high transverse momentum formed in the initial collisions between nucleons will experience a reduction in momentum before emerging from the medium.

One indication of jet quenching is the suppression of hadrons leaving the collision with high transverse momentum. One may observe this suppression by comparing the momentum spectra of hadrons in heavy ion collisions to the spectra of proton-proton collisions, and performing the appropriate scaling. The proton-proton collisions serve as a control as particles emitted in the initial collision do not need to traverse a hot nuclear medium.

The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has shown that at a center of mass energy of 130 GeV, high momentum charged hadrons and neutral pions are indeed suppressed relative to proton-proton collisions. [1] This suppression has since been explained by a variety of jet energy loss models which match experimental results of neutral pion suppression at 200 GeV very well and yield nearly identical predictions. [2]

So to better understand the state of the nuclear matter produced in such collisions and to constrain the models, it is necessary to produce more refined measurements in which the models yield different predictions.

One strategy is to take advantage of the fact that in collisions with a non-zero impact parameter, the shape of the produced medium is anisotropic, extending further at a right angle to the plane of the reaction. For these collisions, the energy loss models predict considerably different results for the neutral pion suppression perpendicular to and parallel to the reaction plane. [2] Recently, the PHENIX experiment has measured the spectrum of neutral pions in 200 GeV collisions at various angles with respect to the reaction plane, providing a better discriminator between models. [3]

It will be crucialinteresting to performtry a similar measurements at the LHC where the collision energy of approximately 4 TeV between lead nuclei is a factor 20 above the comparable energy at RHIC. This enormous increase in energy should lead to a longer-lived, larger QGP state in which the various signatures become more pronounced experimentally. FurthermoreIn additiont, I wish to extend this type analysis can be easily extended to the eta meson at the LHC.

Both the neutral pion and the eta meson decay primarily into a pair of photons. By measuring the energy and position of photon pairs in an electromagnetic calorimeter, one may determine the invariant mass of a hypothetical parent particle that had decayed into the photon pair. By combining all such photon pairs in each event, and making a histogram of the calculated invariant masses, one can may detect a peak at the mass of the pion or eta above the combinatorial background. The size of this peak may can give a measurement of the total pions or etas produced, and one may also extract the momentum spectra of these particles by separating the photon combinations into momentum bins.

The CMS barrel electromagnetic calorimeter consists of 61,200 lead tungstate crystals positioned at 1.29 meters away from the beam pipe, allowing an angular resolution of approximately one degree. [4] With this resolution and using my knowledge of the CMSSW software procedures, I have carried out simulations that confirm the detector’s intrinsic capabilitybeen able to reconstruct pions with momenta from 3 to 11 GeV/c. in simulation. However, in these simulations the individual pions were produced without the expected accompanying expected background from a heavy ion collision. With this background and the identification of pions in a real collision will be more difficult. Pions cannot be identified below 3 GeV/c as the photons produced lack sufficient energy to trigger the electromagnetic calorimeter readouts. Above 11 GeV/c, the momentum is so high that the photons do not spatially separate enough to distinguish them into two particles. The eta particle will be an interesting particle to observe as its larger mass will allow for resolution of the photon pair at considerably higher momenta than for the pions. However, the determination of the eta spectrum will be more challengingdifficult due to both a lower particle yield and the fact due to the fact that a considerable fraction of etas do not decay into a photon pair.

The full azimuthal coverage and large range in pseudorapidity of the CMS electromagnetic calorimeter make it ideal for use in measuring spectra at specific angles to the plane of the reaction between the colliding nuclei. Recent simulations have shown a good resolution of this reaction plane in event reconstruction.

Theoretical models have also suggested that heavy quarks, specifically b and c quarks, will have a different energy loss when traversing the hot nuclear medium of the heavy ion collisions. This is due to an inability to radiate gluons in the direction of their motion, which is referred to as the “dead cone” effect.[5] As the masses of the c and b quarks differ, being about 1.27 GeV/c^2 and 4.20 GeV/c^2 respectively [6], one should expect different radiative energy losses for these partons as they traverse the medium. For this reason, it will also be theoretically interesting to measure the spectra of D and B mesons, which are mesons that contain a heavy flavor quark or antiquark. Specifically, D mesons contain a c quark, and B mesons a b quark.

Both the D and B mesons have a long enough half-life to traverse a length of up to several mm before decay, taking account of relativistic time dilation. If one can reconstruct the tracks of their decay products, as well as the exact position of the collision event, then one may identify heavy flavor mesons by looking at the distance of closest approach of the track to the collision point. Although resolving to resolve such a small distance may initially seem difficult for a detector several meters in radius, in fact the inner pixel tracker subsystem of the CMS detector is designed to resolve the decay vertex point of collision to within 100 micrometers. [7]

Both heavy flavor mesons have a decay channel that involves a muon as well as some assorted hadrons. As its name implies tThe CMS detector is primarily designed to detect muons with a momentum of over 4 GeV/c, so by observing muon tracks embedded in jets of hadrons that miss the primary collision vertex one may be able to resolve the momentum spectrum of an admixture of both D and B mesons.

Once the combined spectrum of all heavy flavor mesons is known, one may attempt to resolve just the spectrum of the B mesons, and by subtraction, determine the spectrum of D mesons as well. There are multiple methods that have a good chance of yielding such a separation. A significant interest group in the CMS collaboration is working on multiple methods to ‘tag’ jets of hadrons as originating from a b quark in proton-proton collsionscollisions, and some of the methods may be adaptable to the noisier environment of heavy ion collisions. Additionally, one may use the decay path of a B meson to a J/Psi particle, which then may decay into a pair of muons, to measure the B meson momentum spectrum. However, this second approach will likely require a significant amount of data that may not be available after the first two heavy ion runs at the LHC.

[1] K. Adcox, et al. Phys. Rev. Lett 88, 022301 (2001)

[2] S. A. Bass, et al. Phys. Rev. C 79, 024901 (2009)

[3] S. Afanasiev, et al. arXiv:0903.4886v1 [nucl-ex] (submitted for publication)

[4] CERN/LHCC, Vol. 1997 / 033 No. CMS TDR 4

[5] Y. L. Dokshitzer and D. E. Karazeev, Phys. Lett. B 519, 199 (2001)

[6] C. Amsler et al, (Particle Data Group), Phys. Lett. B667, 1 (2008)

[7] CERN/LHCC, Vol. 1998 / 006 No. CMS TDR 5

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