Achim Stahl


office +49 241 80-27301 mobile +49 172 5761500



Nationality: German
Date-of-birth: Sept. 14th 1962, married, 2 children

Current Position since Dec. 2004

III. Physikalisches Institut B
RWTH Aachen University

Research Interests:

  • CMS-Experiment:
    Data-analysis with tau leptons
    Operation of the CMS tracker
    R&D for phase-2 upgrade
    Operation of a Tier-2 and a national Tier-3 grid-station
  • Neutrino Physics: mass hierarchy and CP-violation with DoubleChooz, T2K and JUNO.
  • CP-Violation: search for electric dipole moments of protons and light ions with an electrostatic storage ring. A future project at FZ Jülich with the COSY storage ring.
  • Medical Physics: radiation therapy, GEANT4 simulations, measurements of nuclear cross sections, treatment planning for movable tumors.

I am the chair and director of the institute with approximately 70 scientists, engineers and administrators. I am PI of the CMS group, the institute’s largest project. I am also involved in some of the neutrino projects.
Since July 2012 I am the national representative of Germany in the CMS collaboration and spokesperson of the BMBF research focus FSP-102 “Particle Physics with the CMS experiment” (see
In recent years a close collaboration between RWTH Aachen University and the nearby HGF research center FZ Jülich developed under the name JARA (Jülich Aachen Research Alliance). I am founding member and current director of the JARA section FAME focusing on CP-violation and the matter–antimatter asymmetry in the universe.
In 2013 I was awarded the title distinguished professor at the RWTH Aachen University as one out of currently four distinguished professors in Aachen.

Hardware experiences:
Construction of a CMS tracker endcap. Development, construction, and operation of the trigger and timing system of the DoubleChooz experiment. Time-of-flight spectrometer and calorimeter for measurement of nuclear cross sections for medical phyiscs.

DESY Feb. 2001 - Nov. 2004

Leading scientist
Head of TESLA research group @ DESY-Zeuthen

Research Interests:

TESLA-project (later ILC), data-analysis and detector R&D, accelerator physics

  • Instrumentation of the very-forward region, beam-strahlung and beam monitoring, luminosity measurement, beam backgrounds.
  • Development of a source of polarized positrons, test experiment E166 @ SLAC.
  • Physics case and technical challenges of a gamma-gamma collider within the TESLA project.

Hardware experience:
Transmission polarimeter for E166. Diamond sensors for the TESLA beam calorimeter.

University of Bonn Oct. 1992 - Jan. 2001

Postdoc and research assistant
with Prof. Norbert Wermes, OPAL experiment.
Scientific associate at CERN from Nov. 1999 to Oct. 2000

Research Interests:

  • Major contributions to the data analysis in tau physics. Supervision of 20 thesis from which 11 OPAL papers arose, i.e. the measurements of the strange and non-strange spectral functions and \(\alpha_S\), the limit on the mass of the \(\nu_\tau\), searches for CP-violation in the \(\tau\)-production, or the first test of CPT from the mass of \(\tau^+\) and \(\tau^-\).
  • Introduction of the likelihood method for particle identification in OPAL tau physics and many other areas in OPAL.
  • Transfer of the \(\tau\)-identification tools from LEP-1 to the SUSY searches at LEP-2 while scientific associate at CERN.
  • Major update of the Monte Carlo simulation of the preshower endcap detector (PE)

Venia Legendi
Habilitation with a book on “\(\tau\)-lepton physics” submitted in 1998 and published as a separate volume in Springer Tracts in Modern Physics. Awarded the title “Privatdozent” in July 1999.

Hardware experience:
R&D on BaF crystals for a \(\tau\)-charm factory detector.

SLAC Mar. 1996 - Feb. 1998

Feodor-Lynen fellow of the Alexander-von-Humboldt Foundation
Postdoc with Group E in BaBar (Prof. Rafe Schindler and Prof. Marin Perl)
On leave of absence from University of Bonn.

Research Interests:

  • Coordination of the mechanical construction and integration of the barrel of the BaBar CsI(Tl) calorimeter. The calorimeter was built during these two years by a team of two engineers, ten technicians, some students and me.
  • In parallel some work on \(\tau \)-lepton physics (CP-violation) with SLD.

Hardware experience:
CsI(Tl) crystals, large scale detector construction. Mechanics, electronics, cooling.

University of Heidelberg – PhD Mar. 1989 - Feb. 1993

Graduate student
Supervisor: Prof. Klaus Tittel, ALEPH experiment
Research stays at CERN for trigger operation: Jul. 1989 – Dec. 1999 and Apr. – Jul. 1991

Research Interests:

  • Analysis of the decay \(\tau\rightarrow\mu\nu\nu\). Measurement of the \(\tau\) polarization, branching ratio, Michel parameters and a search for lepton number violating \(Z \rightarrow\tau\mu\) events.
  • Installation and operation of the ALEPH level-1 trigger. Development of a concept of redundant triggers for all major Z-decay channels and first determinations of the trigger thresholds and efficiencies.

Title of the thesis “Installation, optimization and analysis of the ALEPH event trigger and investigation of muonic decays of tau leptons”, accepted in Feb. 1993 with distinction.

Hardware experience:
Trigger systems, discrete electronics.

University of Tübingen – Diploma Oct. 1982 - Oct. 1988

Studies of Physics
Diploma in Physics with the optimal mark 1.0

Diploma thesis in atomic physics with Prof. Werner Nagel:
“Measurement of the momentum distribution of K-shell electrons in silver"

Further Responsibilities

  • National representative of Germany in the CMS collaboration
  • Member of the board of advisors of the particle physics section of the German Physical Society.
  • Member of the particle data group
  • Member of the Neutrino Strategy Group in the European Strategy Process at CERN
  • Referee for Physical Review Letters, Physical Review D, and Physics Letters
  • Referee for Deutsche Forschungsgemeinschaft DFG, German-Israeli Foundation GIF, Deutsche Studienstiftung, Alexander-von-Humboldt Foundation, Karl-Zeiss Foundation and others.
  • Member of the scientific advisory committee of the workshop on tau lepton physics since 2004. This is the major conference on tau lepton physics. I am organizing the upcoming 2014 conference in Aachen.
  • Teaching:
    • regular lectures on experimental physics, particle physics
    • coordinator of the international master program in physics
    • responsible for the advanced lab courses in particle physics
    • I supervised more than 50 PhD and around 100 diploma and master thesis


I am author / coauthor of approximately 750 refereed publications leading to an h-index of currently 64 (see for details).

The most important publications are:

  1. A. Stahl, “Physics with tau leptons”, Springer Tracts Mod.Phys.160 (2000) 1.
  2. S. Chatrchyan et al. [CMS Collaboration], “Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC”, JHEP 06 (2013) 081.
  3. K. Abe et al. [T2K Collaboration], “Indication of Electron Neutrino Appearance from an Acceleratorproduced Off-axis Muon Neutrino Beam”, Phys.Rev.Lett. 107 (2011) 041801.
  4. Y. Abe et al. [DoubleChooz Collaboration], “Indication for the disappearance of reactor electron antineutrinos in the Double Chooz experiment.”, Phys.Rev.Lett. 108 (2012) 131801
  5. J. Beringer et al. [Particle Data Group] “Review of Particle Physics”, Phys.Rev. D86 (2012) 010001.