I Presentation of the laboratory and of the topic of the internship

The OUHEP is managed by Dr P. Skubic. This laboratory works on the preparation of two experiments: "ATLAS" and "CLEO".

The area of research of Dr P. Skubic is experimental elementary particle physics. His present interest in this field is in experiments that produce particles containing the newly discovered "bottom" or "beauty" quark ("bottom-flavored" particles). He also has a strong interest in the development of semiconductor detectors for use in high-energy physics experiment and he is currently involved in several major efforts in the continued development of these detectors.

For twenty years, experiments and observations helped to confirm the prediction of The Standard Model and especially to observe a certain number of quarks (the quark TOP was discovered in April 1995 at Fermilab). In order to further demonstrate this theory, experiment at very high energy level (about one TeV) must be performed. Only at these energy levels new particles such as the Higgs boson may be observed.

The Standard Model has a proposal to explain this question: « Why do the fundamental particles have mass, and why are their masses different?  ». Most of scientists are familiar with electric, magnetic and gravitational fields. The Standard Model proposes that there is another field, never before observed, a field that is almost indistinguishable from empty space. The Standard Model calls this the Higgs field. The Standard Model says that all of space is filled with this field, and that by interacting with this field, particles acquire their masses. Particles that interact strongly with the Higgs field are heavy, while those that interact weakly are light. The Higgs field has at least one new particle associated with it: the Higgs boson.

A very efficient detector is needed to see such particle. The ATLAS detector will be able to detect this particle if it exits.

This detector is due to begin in the year 2005 at the LHC (Large Hadron Collider) at the CERN. A picture of the LHC is showed in annex, page I. The diagram 1 shows the position of the ATLAS detector at LHC.

The ATLAS detector consists of four major components:

¯ The inner tracker: measures the momentum of each charged particle.

¯ The calorimeter: measures the energies carried by the particles.

¯ The muon spectrometer: identifies and measures muons.

¯ The magnet system: create a strong magnetic field over a huge volume.

Diagram 1 : Position of the detector at LHC

To have more information about Atlas you can check this web site: http://atlasinfo.cern.ch/Atlas/public/Welcome.html .

CLEO is a multipurpose high energy physics detector incorporating excellent charged and neutral particle detection and measurement, used to analyze electron-positron collision events generated by the CESR (Cornell Electron positron Storage Ring). The CLEO detector is operated by a collaboration of over 100 physicists from many institutions. A picture of the CLEO detector is showed in annex, page II.

The CESR is an electron-positron collider with a circumference of 768 meters, located on the Cornell University campus. It is capable of producing collisions between electrons and their anti-particles, positrons, with center-of-mass energies between 9 and 12 GeV. When an electron and a positron collide and annihilate, there is a flash of energy that is studied with a large and complex detection apparatus called the CLEO detector. The diagram 2 shows the position of the CLEO detector at CESR.

To have more information about Cleo you can check this web site: http://www.lns.cornell.edu/public/lab-info/cleo.html .

A key component of the CLEO experiment is the unit that links the detector with the electronics. These two parts are not located in the same plan. That’s why the circuit is a flexible circuit. This Flex was made by GECRD. (General Electric Corporate Research and Development).

The purpose of the internship is to set up a glue dispensing system able to glue small components on similar circuits to be used for ATLAS. The major problem comes from the size of the components and of the pads of the circuit. Indeed the resistors that are needed to be glued are 1 mm long, 0.5 mm large and 0.2 mm high.To glue such small components the laboratory had to buy and to test special equipment that is shown in the next paragraph.