Caroline Kathrin Riedl

Research Assistant Professor


Caroline Kathrin Riedl

Primary Research Area

  • Nuclear Physics
467 Loomis Laboratory


Riedl received her diploma degree in physics from the University of Erlangen-Nuremberg, Germany, in 2001. She wrote her diploma thesis in theoretical physics on (1+1)-dimensional quantum field theoretical models and massless mesons in dense nuclear matter at zero temperature. In 2002, she switched her research focus to experimental particle physics and received her PhD with the University of Erlangen-Nuremberg in 2005. In her PhD research, she worked at DESY, Germany, on HERMES data. She investigated the tensor structure of polarized deuterons in deep-inelastic lepton-nucleon scattering.

A fellowship with INFN Frascati, Italy, and a postdoc association with DESY allowed her to continue her research at HERMES. She participated in the commissioning and operation of the HERMES recoil detector and lead the analysis and publication of hard-exclusive data collected with this detector. From 2008 to 2010, Riedl was the deputy analysis coordinator of HERMES. In 2011 and 2012, she worked from DESY as main data quality manager for CMS, one of the LHC experiments at CERN, and contributed to the analysis of the Higgs-boson decay into two tau-leptons and successively into muons.

Riedl joined the Department of Physics at the University of Illinois as a research assistant professor in 2013. In 2013-2015, she was the project coordinator for a detector upgrade for COMPASS at CERN. She organized the prototyping, construction and assembly of a large-area planar drift chamber (DC5). Riedl is currently the co-covener for the COMPASS polarized Drell-Yan program.

The DC5 detector was constructed in the US, mostly at the Nuclear Physics Laboratory. This would not have been possible without a small army of undergraduate students. The detector parts were shipped to CERN in fall 2014 and assembled. DC5 was installed into COMPASS in May 2015 and has been successfully collecting valuable data since then.

Research Interests

  • Development and construction of detectors for nuclear-physics research.
  • Experimental nuclear physics: investigation of the structure the nucleon, in particular its spin structure. Transverse-Momentum Dependent parton distribution functions (TMDs) from polarization-dependent semi-inclusive deep-inelastic scattering (SIDIS) as compared to polarization-dependent Drell-Yan scattering. Generalized Parton Distributions (GPDs) in hard-exclusive reactions, in particular from Deeply Virtual Compton Scattering (DVCS). In hard-exclusive reactions, the nucleon probed by the incident lepton beam remains intact.

Research Statement

I am currently stationed at CERN, the European center for nuclear research, where I study the spin structure of the proton. The COMPASS experiment will continue to collect data until mid-November 2015 using a negatively charged pion beam scattering off a transversely polarized proton target. The goal is to extract from this measurement in polarization-dependent Drell-Yan scattering the so-called Sivers amplitude, which correlates the transverse spin of the parent nucleon and the transverse momentum of its partons. The comparison to the Sivers amplitude previously extracted from data in semi-inclusive deep-inelastic scattering is eagerly awaited in the nuclear-physics community and will provide another puzzle piece of understanding nuclear structure.

Selected Articles in Journals

  • Beam-helicity asymmetry arising from deeply virtual Compton scattering measured with kinematically complete event reconstruction. HERMES Collaboration, JHEP 10 (2012) 042.
  • First Measurement of the Tensor Structure Function b1 of the Deuteron. HERMES Collaboration, Phys. Rev. Lett. 95 (2005) 242001.
  • Precise determination of the spin structure function g1 of the proton, deuteron and neutron. HERMES Collaboration, Phys. Rev. D 75 (2007) 012007.
  • Measurement of azimuthal asymmetries associated with deeply virtual Compton scattering on a longitudinally polarized deuterium target. HERMES Collaboration, Nucl. Phys. B842 (2011) 265- 298.
  • Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC. CMS Collaboration, Phys. Lett. B 716 (2012) 30-61.

Articles in Conference Proceedings