Department of Physics
Doctor David Krofcheck
MSc, PhD (Ohio State)
Building 303, Room 711
Phone: +64 9 373 7599 ext 88897
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 37 countries, over 150 institutes and over 2000 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.
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. 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.
- CMS COLLABORATION (V. Khachatryan et al.), ‘First measurement of the cross section for top-quark pair production in proton–proton collisions at √s = 7 TeV', Physics Letters B http://cdsweb.cern.ch/record/1303021/files/plb.11.058.pdf
- CMS COLLABORATION (V. Khachatryan et al.), ‘Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at s=7 TeV’, Phys. Rev. Lett. 105, 022002, 2010
- CMS COLLABORATION (V. Khachatryan et al.), ‘Observation of Long-Range, Near-Side Angular Correlations in Proton-Proton Collisions at the LHC’, Journal of High Energy Physics 9, 091, 2010
- CMS COLLABORATION, (V. Khachatryan et al.), 'First Measurement of Bose-Einstein Correlations in Proton-Proton Collisions at √s =0.9 and 2.36 TeV at the LHC', Physical Peview Letters, 105, 032001, 2010
- CMS COLLABORATION, (V. Khachatryan et al.), 'Measurement of the charge ratio of atmospheric muons with the CMS detector', Physics Letters B, 692, 2010
- CMS COLLABORATION, (V. Khachatryan et al.), ‘Tracking performance results from early LHC operation', European Physical Journal C 70, 1165-1193, 2010
- CMS COLLABORATION, (V. Khachatryan et al.), 'Search for Dijet Resonances in 7 TeV pp Collisions at CMS', Physical Review Letters 105, 211801, 2010
- CMS COLLABORATION, (V. Khachatryan et al.), 'Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at √s =0.9 and 2.36 TeV', Journal of High Energy Physics 2, 041, 2010
- CMS COLLABORATION, (V. Khachatryan et al.), ‘First measurement of the underlying event activity at the LHC with √s=0.9 TeV’, European Physics Journal C70 555-572, 2010
- CMS COLLABORATION, (V. Khachatryan et al.), 'CMS Physics Technical Design Report', Journal of Physics G 34 99-1579, 2007
- CMS COLLABORATION, (V. Khachatryan et al.), ‘High Density QCD with Heavy Ions", Journal of Physics G 34 2307-2455, 2007
- D.Krofcheck, R. Mak. A, P. Allfrey ,’Hydjet Simulations of Elliptic Flow in Heavy Ion Collisions at the LHC’, International Journal of Modern Physics E 1917-1922, August 2007
- KROFCHECK, D. ''Signatures for AdS/CFT using the CMS experiment at the LHC”, 14th Lomonosov Conference on Elementary Particle Physics, Moscow, Russia, 19 August - 25 August 2009, Editor: Studenikin, A., PARTICLE PHYSICS AT THE YEAR OF ASTRONOMY. (World Scientific, Singapore). p.57-59. (2010).