Division of Elementary Particle Physics

The Division conducts research in particle physics and cosmology using both experimental and theoretical methods.

Theoretical Particle Physics

The research in particle theory covers a wide range of topics in quantum field theories, including phenomenology, computational field theory and non-commutative space-time.

Research on non-commutative gauge theories has continued in several aspects, including implications on non-commutative gravity and non-commutative gauge symmetries. The solution of the stochastic Langevin equations for clustering in turbulent flows has been presented using Wiener path integral.

The computational field theory research group started its operations in 2009. The research is concentrated on non-perturbative numerical simulations. The theories studied include the Standard Model and strongly coupled beyond the Standard Model theories, e.g. the so-called Minimal Technicolor model. We are among the pioneers in studying these models non-perturbatively.

In beyond the Standard Model phenomenology emphasis was in supersymmetric models and gauge extensions of the Standard Model. The connection between collider searches and dark matter was studied. The detection of the Higgs sector particles in supersymmetric and gauge extended models was considered and identification of the Higgs presentation was studied.

In hadron physics the focus has been on understanding hadron structure in the basic theory of quantum chromodynamics. A method was developed for deriving Lorentz and gauge covariant wave equations of mesons and baryons. A long-standing challenge by R. P. Feynman concerning the anomalous magnetic moment of electrons was successfully addressed.

Experimental Particle Physics

The Large Hadron Collider (LHC) at CERN, Geneva, was brought into operation in 2009. The first proton-proton collisions were observed in the CMS detector on 23rd of November, with proton beams of E=450 GeV each, corresponding to the LHC beam injection energy. The first test run of the accelerator lasted until 16th December, and during the period the beam energies were raised to 1.18 TeV per beam, which was the highest beam energy ever achieved with particle accelerators.

The CMS detector, with participation from the University of Helsinki, collected large quantities of data both at 900 GeV and 2.36 TeV centre-of-mass energies. The CMS B physics group, co-convened by P. Eerola, was in particular looking for dimuon events. The collected statistics was still too small to see a J/ψ mass peak, but one candidate event was found.

In the field of forward physics the research was concentrated on:

Graphical event display of
  final stage of CMS scattering experiment.  Two muons clearly visible.

A J/ψ candidate event observed by CMS at 2.36 TeV centre-of-mass energy. The two muons from the J/ψ candidate are marked with the red lines.

Cosmology

We participate in the Planck satellite mission and in its data analysis at the Low Frequency Instrument (LFI) Data Processing Centre (DPC). We are responsible for producing the sky maps for the Low Frequency Instrument (maps at 30, 44, and 70 GHz).  By the end of 2009 we had exchanged maps of the first 2.5 months of data with the HFI DPC. We have also set up a Planck Monte Carlo simulation pipeline at the Finnish supercomputer center CSC, for error propagation and systematic effect analysis of Planck data.

In theoretical cosmology the focus has been on the primordial perturbation and dark energy. We have studied the dynamics of the subdominant curvaton and dark energy. We have studied the dynamics of the subdominant curvaton models and attempted to clarify the role of inhomogeneities for the accelerated expansion.

Detector Laboratory

Detector Laboratory supports Finnish experimental research on collider-based physics. It is a joint laboratory between Helsinki Institute of Physics and the Department of Physics. The Laboratory provides premises, equipment and know-how for research projects developing radiation detectors.

The work with the semicircular GEM detectors for the CERN TOTEM T2 telescope continued. After successfully completed tests in the Laboratory, the detectors were transported to CERN and commissioned at the LHC.

The Finnish Cosmic Rack telescope, built from eight layers of CMS silicon detectors measuring tracks of cosmic particles, was used as a test station providing real data for testing the CMS Tracker Outer Barrel (TOB) functionality as well as for development of TOB software.