David Hardtke
CV (current as of May 2007)
I'm currently serving as Chief Scientist at Surf Canyon Incorporated . Surf Canyon is developing
implicit relvance feedback technology for web search.
This page is about
my previous work as a physicist.
Until August 2007 I worked at the University of California Berkeley Space Sciences Lab in the
area of high-energy neutrino astrophysics. I am a
member of the IceCube
collaboration. We are currently constructing a cubic kilometer
scale neutrino detector using the South Pole Ice as a neutrino target
and Cerenkov radiator. My particular physics interests are:
- Using IceCube to search for Exotic Particles. In
particular, I want to
look for slowly moving massive particles (Q-balls, strangelets, GUT
monopoles). This work is part of the IceCube Exotic
Particles Working Group.
- Search for neutrinos from SGR 1806-20. On December 27th,
2004 one of the four known soft gamma repeaters had a giant flare and
became the brightest cosmic event ever observed. Using AMANDA, we
searched for muons coincident with this event. The limits on
gamma and neutrino fluxes are presented here.
Before coming to UC Berkeley, my research focused primarily on
relativistic heavy-ion collisions. Using the collision of heavy nuclei,
we hoped to create a state of quasi-deconfined quarks and gluons
(Quark-Gluon Plasma). This state of matter is predicted by lattice QCD
simulations and bag model calculations, although the properties of this
state are highly dependent on the input quark masses in the lattice
simulations. By measuring the properties of this state we can confirm
the lattice QCD predictions and measure the properties of partons in
this new state. We know that the "constituent" mass of a light quark
bound in ahadron is of order 300 MeV, while the "bare" quark mass
appropriate foruse in QCD Lagrangian is of order 5-10 MeV. By measuring
the propertiesof the deconfined QGP state, we hope to understand how
the quarks acquiremass during confinement. We can also learn about
phase transitions in astrongly interacting system. In some sense, we
hope to understand the "condensed matter" physics of QCD.
I worked from 1997 to 2003 as a member of the STAR collaboration. STAR is a
large experiment based at the Relativistic Heavy-Ion Collider. Within
the context of STAR, my specific research interests were:
- The production and modification of jets and dijets in hot and
cold nuclear matter. Jets and dijets result from a large momentum
transfer elastic scatterings of quarks and gluons. Quarks and
gluons produced in dense nuclear matter, however, lose energy via
multiple gluon emission. We are trying to measure the amount of
energy loss in order to probe the gluon densities created in these
collisions. These measurements may give the most accurate
determination of the initial densities created in nucleus-nucleus
collisions. I led the analysis efforts demonstrating that:
- Large transverse momentum particles are produced in a similar
manner in proton-proton and nucleus-nucleus collisions, i.e. parton
scattering and fragmentation into jets.
- The number of large transverse momentum particles produced in a
heavy-ion collision is strongly
suppressed compared to scaled proton-proton collisions.
- In the most violent nucleus-nucleus collisions, dijets
are not produced. One of the jets in the pair is absorbed in
the hot nuclear matter.
The picture that emerges from these observations is a highly excited
and dense state where only partons produced near the surface are able
to escape and fragment into jets. In order to account for the
observations, densities greater than 15 times nuclear matter density
must be achieved early in the evolution of the system. It is very
difficult to speak of such a system in terms of hadronic degrees of
freedom, and the natural language becomes quarks, gluons, and a
Quark-Gluon plasma.
- The production
of antinuclei and search for novel nuclear states. In a
central Gold-Gold collision at RHIC, over 4000 particles are produced.
Occasionally these particles cluster in light antinuclei.
We have observed copious production of antideuterons and
antihelium. In the futurewe will look for unobserved antinuclei
and other exotic objects (antihypernuclei, strangelets, etc.)
These measurements will be greatly enhanced ifthe proposed full
coverage time-of-flight detector for STAR is approved.
- Software for the analysis of large data volumes. STAR
produces data at an astounding rate of 60-70 MB/s. I was heavily
involved in the reconstruction and simulation software, particularly
for the Time Projection Chamber. Highly efficient reconstruction
of several thousand tracks per event presents an enormous intellectual
challenge.
Previously, I was involved with Experiment NA44 at CERN, a fixed-target
focussing spectrometer designed to measure single particle spectra and
two particle Bose-Einstein correlations. My thesis was on pion
interferometry measurements in Pb+Pb collisions at the SPS. I
have also worked on several technical aspects of Bose-Einstein
correlation measurements,including an analytical
interpretation of the fitted source radii.
Links to other pages:
IceCube
AMANDA
Price Group Home
STAR
How to contact me:
cell: (510) 823-8982
email: david @ hardtke.net
Last modified: 22 May 2008