Dr. Jaehoon Yu
Department of Physics
RM 342 CPB
Arlington, TX 76019-0059
Professor Paul Grannis
Department of Physics
Stony Brook University
Stony Brook, NY 11794
November 5, 2007
Dear professor Grannis,
It is my great pleasure to write this letter of recommendation for Mr. Venkatesh Kaushik who
is applying for a Research Associate position in your group. He started working with me
September, 2001, as soon as I arrived at the University of Texas at Arlington (UTA), on the DØ
remote computing project I was in charge of. He was a master’s degree student at the Computer
Science and Engineering (CSE) department of UTA and worked in my DØ remote computing
group to manage the local DØ production system. He, however, always desired to become a
physicist so he took various physics courses while he was a graduate student in the CSE
department and performed well in the courses, surpassing physics students and impressing our
faculty members.
After working with me for a semester as a part time CSE graduate research assistant, Venkat
decided to apply to the physics department as a graduate student with a strong interest in high
energy physics. Given his marked academic performance in the physics classes he took, extraordinary enthusiasm toward physics and strong potential to be successful in physics degree
program, he was admitted to physics graduate program without hesitation and with full support
from the physics department.
As a norm, Venkat was given a semester to focus on his curriculum and to investigate other
opportunities for one semester. Upon completing the first semester, he joined HEP group in a
heart bit and started working with me as my graduate student in the M.S. program. At that time,
I started getting involved in Linear Collider digital hadronic calorimeter (DHCAL) development
using the Gas Electron Multiplier (GEM) technology to improve hadronic jet energy resolution
to an unprecedented level, 30% EJet . To accomplish this level of precision, the energy flow
algorithm was suggested as a solution. The first step in this endeavor was to investigate
feasibility of GEM based DHCAL and its performance in jet energy resolution. Given his
timing, this investigation and the subsequent EFA development became his M.S. thesis topic.
Since we were just getting involved in the future linear collider, we did not even have any
simulation tools available. So Venkat interacted with the CALICE collaboration, as we became
the member of the collaboration, and single handedly implemented Mokka, a GEANT4 based
cell level simulation tool developed for TESLA detector. He then implemented a double GEM
detector geometry, turning it into a generally available one in the primary Mokka database.
Since one needs full detector geometries not just the hadronic calorimeter to study the detector
performance properly, he replaced the existing TESLA detector hadronic calorimeter with the
GEM based DHCAL. As the next step, he developed a root based analysis tool that not only
makes necessary plots but also performs sophisticated fits to the distributions. This allowed him
to carry out the feasibility study of the detector, to develop an EFA and to study performances of
the detector and the algorithm in two pion case and in complicated event topologies such as
tt → 6 jet final state. Venkat did all this by himself with minimal help from me in a very short
time span, leveraging his computing skills, and while he was working full time as a teaching
assistant since he was only supported one semester to complete his thesis. This demonstrates his
willingness to invest enormous time and effort in his research.
Based on Venkat’s study, we have learned that it is entirely feasible to achieve the targeted
jet energy resolution of 30% EJet using GEM DHCAL. Venkat made numerous presentations on
this subject, including the American Linear Collider Physics Group Workshop held at UTA in
Jan. 2003 and the APS Texas section meeting in April 2004. The GEM DHCAL geometry he
developed was sent to be incorporated in the SiD, an ILC detector concept, simulation package
through the interaction with Dr. Norman Graf at SLAC. This work is documented thoroughly in
his M.S. thesis. This thesis was evaluated by his defense committee members so high a quality
that it is at the satisfactory level even for a Ph.D with minor additional work.
Once he was done with his M.S. degree, he decided to continue his work in Ph.D. Of the
choices he had at the time of his admission to Ph.D. program, he decided to work on the Higgs
search in its W (Æeν) associated production at the DØ experiment at Fermilab in 2004. After
spending just one semester, passing all his qualifying exams with high marks, he was sent to
Fermilab in spring 2005 and started working on the experiment as a DAQ expert shifter. Given
the important role of the position in ensuring high data quality and high efficiency, this shift
requires intense commitment and put on shift for several weeks consecutively. He carried out
this task very well, working well with collaborators in the experiment.
Of course, life is not that simple, especially when you are away from the university. While
he was working on the DØ experiment, he had to take a few remaining courses remotely to
satisfy his degree requirements. He made arrangements with faculty for remote class
participation and performed very well in all classes he took. He did not miss any class or
homework. Sometimes, I took his exams and administered them separately on him at Fermilab. I
was impressed with his devotion and performance despite many other responsibilities at the
experiment that naturally are sources of distraction.
Venkat did not hesitate to roll up his sleeves and participated in service work our group is
responsible for. He helped testing and replacement of PMT’s in the Inter-Cryostat Detectors
(ICD) and took shifts for Forward Proton Detector operations. When the collaboration needed
urgently a new inter-calibration of the ICD due to increased instantaneous luminosity, he jumped
right in, despite the fact that it was close to the final stage of his thesis analysis, and established
the new calibration factors as a function of instantaneous luminosity through a thorough study of
the high luminosity special events and implemented it into the reconstruction package. This was
of critical importance since the ICD is a crucial detector in measuring missing ET with high
precision and thus high priority physics analyses relied heavily on this new calibration.
While working on detector operations and hardware related service work, Venkat also got
involved in electron trigger and ID efficiency studies. He worked with numerous postdoctoral
fellows in the collaboration and other senior physicists in making these results available to the
collaboration. He presented his work virtually every week in Higgs, electron ID and calorimeter
group meetings during this period. He then started looking into Higgs samples, completed the
analysis using 1fb-1 of data and subsequently contributed to the limit setting with the full 1.7fb-1
of data. These results are then incorporated into the overall DØ combined Higgs limits and the
eventual combined Tevatron Higgs limits. In carrying out this analysis, his thirst to knowledge
was apparent. Despite the division of the work that made final limit setting as a responsibility of
someone else’s, Venkat comprehended fully the statistical techniques behind the limit setting
procedure and made the limit setting technique his own. He made several high level
presentations on his thesis subject, including presentations at the APS meeting in April 2006 and
the DPF meeting in November 2006.
I have worked with many graduate students, throughout my career in many different
capacities, including the first commissioning coordinator of the Run II DØ detector. I, however,
have encountered only a handful of students as bright, competent, self-motivated and hard
working as Venkat. The extra-ordinary enthusiasm, devotion and thoroughness assisted by the
unquenchable thirst for excellence that he brings to his research projects and his tasks make him
a first rate physicist. The sincerity and seriousness toward his responsibilities rank him very high
on my list of respected colleagues. His remarkably high level computing skills together with his
intelligence make him a highly effective physicist. His mild manner and outgoing personality
make him a well liked colleague and a good team member. He is the kind of person who would
not hesitate to roll up his sleeves and put in as many hours as needed to accomplish goals
whether they are the group’s or his.
As you can tell from my long letter, I am very impressed with Venkat. I have no doubt he
will be a successful physicist and an extremely valuable asset to your group, especially given his
preparation in both hadron and lepton collider physics. Without a doubt he is well prepared and
well qualified to be a member of a prestigious institution like yours. In this regard, I strongly
recommend Venkat for the Research Associate position in your group. Please do not hesitate to
contact me either by phone at (817) 272-2814 or by e-mail, jaehoonyu@uta.edu, should you have
any questions concerning Venkat. I would be more than happy to answer any questions.
Sincerely yours,
______________________________
Dr. Jaehoon Yu, Ph.D.
Associate Professor
Department of Physics
University of Texas at Arlington