David Hardtke

CV (current as of May 2007)

I'm currently developing an intelligent meta-search application that can be previewed at . The goal of this project is to build a general purpose search engine that combines multiple keyword-driven search feeds and intelligent semantic analysis to deliver the most timely search results irregardless of source and content type. With the real-time web, the meaning of a phrase might change on a daily or hourly basis, and we try to track and respond to these changes.

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:
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:
  1. 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.
  2. The number of large transverse momentum particles produced in a heavy-ion collision is strongly suppressed compared to scaled proton-proton collisions.
  3. 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.
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:

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How to contact me:

cell: (510) 823-8982 
email: david @

Last modified: 20 Aug 2009