Assessment Report / Helsinki Institute of Physics

ASSESSMENT OF THE HELSINKI INSTITUTE OF PHYSICS (HIP)


Experimental High-Energy Physics

The Helsinki Institute of Physics (HIP) is the National Institute for Theoretical and Particle Physics. As such it has responsibility for Finland’s relation and involvement in the experimental high-energy physics program at CERN (and other international accelerator centers). The presentation to the Panel included the efforts of the experimental program from both, HIP and the Department of Physics. This illustrates the close relationship between these two institutes, and is therefore treated here as one.

The past involvement of this program has been primarily in the DELPHI experiment at CERN. In this situation the Helsinki effort has been well recognized both in view of its technical involvement in the experimental setup (Delphi Hadron Calorimeter and Delphi Vertex Detector) and in the physics analysis. Key results with strong Helsinki involvement are the extraction of the color structure of multi-parton final states and gluon identification, as well as precise information on the up(charm)-bottom quark coupling matrix elements of the Cabbibo-Kobayashi-Maskawa matrix. There are a number of other important results from the overall DELPHI experiment with less intense Helsinki involvement although many of the routine activities (such as the continuous maintenance of the DELPHI Hadron Calorimeter) have provided for a constant involvement of the Helsinki group in the experiment.

The results of the DELPHI experiment represent important physics at the particle frontier. The involvement of the Helsinki group has placed it at a forefront of high-energy physics in a worldwide context. The Panel hopes that the group will be able to maintain such a position.

High-energy experiments have evolved to major technical enterprises, involving hundreds and in the future possibly more than a thousand collaborators. For a smaller group to achieve recognition and to be able to claim interesting physics results, the identification with a sub-component of the experiment is desirable, preferably paired with a specialty area in technology that plays a critical role in the setup. The future program of the Helsinki group is directed towards the very high-energy collisions at the CERN LHC accelerator, expected to start operation in 2005/6. The group brings special knowledge in precision detectors with VLSI technology, for example. This could have given the group a lead role in the Vertex Tracker design of the CMS detector project, the detector that the group has chosen to get involved with.

For reasons not fully transparent to the committee, HIP decided not to get involved in either production or the major testing programs for the Tracker semi-conductor detectors. It is beyond the scope of this review to assess whether this would have indeed been possible given the limited resources, or whether it was a conscious decision by the management to keep the effort focussed more on software-related contributions (and design and construction of tracker mechanical structure and alignment).

In view of what was said above about involvement with a specialty area in technology, the Panel is somewhat concerned that the role of the Helsinki effort may be less visible, and recommends therefore to take measures to increase the visibility. In this respect the creation of the new chair in experimental particle physics in the Department of Physics is welcome. The physics goals of the LHC program are at the forefront of our understanding of the very nature of elementary particles and the fundamental mechanism that generates their mass. There is no question that this is a research at the absolute top.


The Theory Program

Of the 119 positions occurring on the list of staff of the Helsinki Institute of Physics, 53 currently are occupied by the theory program. The theoretical research activities center around four domains:

A. Mathematical physics and field theory
B. Particle theory and cosmology
C. Laser physics and quantum optics
D. Statistical physics and materials science
The scientific output of the four groups documents their very high level of competence. The publications appeared in the leading international journals and are often referred to in the current literature. The quality of the work done within the theory program compares favourably with that of the best european groups working in one of the above fields.

Mathematical physics, field theory, particle theory and cosmology are at the focus of attention in theoretical physics, internationally and are likely to remain very active domains of research in the years to come. In particular, the Panel considers the interface between particle physics and astrophysics as a very promising line of research. Both in mathematical physics and in particle theory, there exist strong collaborations with the theory group at the Department of Physics of the University of Helsinki. Also, the particle theory group is participating in the work done within the international scientific community to prepare the ground for the experimental search for supersymmetry and other possible extensions of the Standard Model of particle physics.

The laser physics and quantum optics group works on quantum information, quantum control and laser cooling of atoms, and Bose-Einstein condensation of quantum gases. All these problems are new and subject to very active research internationally. They probe the limits of our understanding of the quantum behaviour of nature. Despite its very young age the group is already recognised in this competitive field, and has created a very active international collaboration with some of the leading groups in the field.

The work of the statistical physics and materials science group is broadly divided between that on disordered media and that on surface diffusion and growth. These are both important areas in modern statistical physics research, and have a wide range of applications in other branches of science and also in practical life. The group is well recognised and visible in its field of research and has very good connections internationally. The panel finds it important that quantum optics and statistical physics, both being new active fields of research, are supported by HIP as they are absent in the Department of Physics.

Technology program

This program provides a valuable support for organising the data transfer, engineering design, project management via easy accessible world wide web. Although the Panel is impressed by this activity it does not include a research evaluation of this group.

General Comments


At present, the appointments at HIP for scientists, engineers and technicians are very short term, including those of the program and group leaders. On the one side, this policy ensures a high degree of flexibility in the development of the research activities hosted by the institute, on the other side it runs the risk that the best people will either not be attracted or leave the institute prematurely. The Panel is of the opinion that this hiring policy should be complemented with longer term appointments for outstanding scientists, to give a longer term perspective to the research program.

HIP’s main role should be to offer unique reasearch opportunities to its own scientists and to scientists from other institutes, especially from Finnish university groups, to focus their research on important and highly relevant subjects by temporarily forming or joining teams of ”critical mass”. The institute should provide these teams with a creative and inspiring environment with adequate infrastructure support.

It seems that the institute, being only recently created through merger of three research institutes, still to some extent lacks a well-defined identity, and there appears to be some gap between the visions of the leadership and those of the active research staff. However, the efforts of the leadership to attract outstanding physicists with long-term appointments has the full support of the Panel. Ideally, one of these persons could eventually be charged with the full responsibility of leading the institute, ensuring thereby close contact between the leadership and the research staff.

In summary the work of the Helsinki Institute of Physics is rated by the Panel with Grade 6.