Dr David Krofcheck

MSc/PhD (Ohio State)

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Senior Lecturer

Research | Current

Experimental high energy nuclear physics
The University of Auckland is a member of Compact Muon Solenoid (CMS) experiment currently running at The Large Hadron Collider (LHC) at CERN, Geneva. The CMS detector is a collaboration involving 41 countries, over 180 institutes and over 3000 physicists from around the world. The CMS group will examine the dynamics of collisions between counter-rotating beams of protons (light ions), and counter-rotating beams of lead nuclei (heavy ions). Auckland's role is to help develop and perform tests of the Beam Radiation Monitoring detectors, and to work on data analysis of p-p and Pb-Pb reactions.

The nuclear physics aims of this experiment are two-fold: first, to test predictions made using Quantum ChromoDynamics (QCD), which is the modern theory of strong nuclear forces, and second, to gain detailed information on the equation-of-state which governs highly compressed nuclear matter. In this work, the nuclear equation-of-state can be studied by measuring a property of heavy nuclei nuclear reactions called the "momentum flow". An important QCD prediction is that if nuclear matter is substantially compressed beyond its normal density, or if a high enough energy density is achieved in a nuclear volume, then a Quark-Gluon Plasma (QGP) may be formed. In such a case, the momentum flow may be substantially altered from its normal flow pattern. Other properties of the possible QGP may be studied in detail using hard probes or heavy meson flow. Such high energy-density matter is believed to have existed in the initial few microseconds following the "Big Bang" origin of the universe.

LHC activity


Environmental radiation
Radiation is a natural part of our environment. I constructed a Compton suppressed, High-Purity Germanium (HPGe) gamma-ray detector system to measure the energy of characteristic "fingerprint" gamma-rays from natural radionuclides. The HPGe and a Compton Suppression detector sit inside a 2000-kg lead shield. This type of measurement provides information on radiation hazards, sand transport, and dating of soils using gamma-rays from 137-cesium left over from nuclear testing in the south pacific. I also use the HPGe to measure the "fingerprint" gamma-rays produced by progeny of radon gas. Radon is a tasteless, colourless, and odourless gas emitted by the radioactive decay of natural uranium and thorium in the earth. The progeny 214-bismuth and 214-lead produce the gamma rays that permit us to deduce the amount of radon present in caves or buildings.

Areas of expertise

  • Experimental high energy nuclear physics
  • Environmental radiation

Selected publications and creative works (Research Outputs)

  • Chatrchyan, S., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Bergauer, T., ... Friedl, M. (2014). Evidence of b-jet quenching in PbPb collisions at √(s(NN))=2.76  TeV. Physical review letters, 113 (13)10.1103/physrevlett.113.132301
  • Chatrchyan, S., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Bergauer, T., ... Friedl, M. (2013). Measurement of the Bs0→μ+<sup>μ-</sup>branching fraction and search for B0→μ+<sup>μ-</sup>with the CMS experiment. Physical Review Letters, 111 (10).10.1103/PhysRevLett.111.101804
  • Chatrchyan, S., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Bergauer, T., ... Friedl, M. (2013). Observation of a new boson with mass near 125 GeV in pp collisions at √=7 and 8 TeV. Journal of High Energy Physics, 2013 (6).10.1007/JHEP06(2013)081
  • Chatrchyan, S., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Aguilo, E., ... Fabjan, C. (2013). Study of the mass and spin-parity of the Higgs boson candidate via its decays to Z boson pairs. Physical Review Letters, 110 (8).10.1103/PhysRevLett.110.081803
  • Chatrchyan, S., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Aguilo, E., ... Fabjan, C. (2013). Measurement of the azimuthal anisotropy of neutral pions in Pb-Pb collisions at √s<inf>NN</inf>=2.76 TeV. Physical Review Letters, 110 (4).10.1103/PhysRevLett.110.042301
  • Chatrchyan, S., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Aguilo, E., ... Fabjan, C. (2012). A New Boson with a Mass of 125 GeV Observed with the CMS Experiment at the Large Hadron Collider. SCIENCE, 338 (6114), 1569-1575. 10.1126/science.1230816
  • Chatrchyan, S., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Aguilo, E., ... Fabjan, C. (2012). Observation of sequential Υ suppression in PbPb collisions. Physical Review Letters, 109 (22).10.1103/PhysRevLett.109.222301
  • Chatrchyan, S., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Bergauer, T., ... Friedl, M. (2012). Azimuthal Anisotropy of Charged Particles at High Transverse Momenta in Pb-Pb Collisions at root S-NN=2.76 TeV. PHYSICAL REVIEW LETTERS, 109 (2)10.1103/PhysRevLett.109.022301

Identifiers

Contact details

Primary location

SCIENCE CENTRE - MATHPHYSIC - Bldg 303
Level 7, Room 711
38 PRINCES ST
AUCKLAND 1010
New Zealand

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