Tapio Niinikoski

AN INVESTIGATION OF THE SPIN STRUCTURE OF THE PROTON IN DEEP INELASTIC SCATTERING OF POLARISED MUONS ON POLARISED PROTONS

An investigation of the spin structure of the proton in deep inelastic scattering of polarised muons on polarised protons

Physics potential and experimental challenges of the LHC luminosity upgrade

Abstract.We discuss the physics potential and the experimental challenges of an upgraded LHC running at an instantaneous luminosity of 1035 cm-2s-1. The detector R&D needed to operate ATLAS and CMS in a very high radiation environment and the expected detector performance are discussed. A few examples of the increased physics potential are given, ranging from precise measurements within the Standard Model (in particular in the Higgs sector) to the discovery reach for several New Physics processes.

Comparison of forward hadrons produced in muon interactions on nuclear targets and deuterium

Differential multiplicities of forward produced hadrons in deep inelastic muon scattering on nuclear targets have been compared with those from deuterium. The ratios are observed to increase towards unity as the virtual photon energy increases with no significant dependence on the other muon kinematic variables. The hadron transverse momentum distribution is observed to be broadened in nuclear targets. The dependence on the remaining hadron variables is investigated and the results are discussed in the framework of intranuclear interaction models and in the context of the EMC effect.

“Frozen spin” polarized target

Abstract We describe the construction and operation of a frozen spin polarized proton target used in a scattering experiment at the CERN Proton Synchrotron. The target, made of 1,2-propanediol, has 150 mm length and 17 mm diameter, about 90% average polarization with loss rate 1–5%/day, polarization reversal time of 2 h and solid angle of access of 4π×0.94.

A Frozen Spin Target with Three Orthogonal Polarization Directions

A frozen spin target has been designed and constructed at CEN-Saclay for nucleon-nucleon scattering experiments at the synchrotron SATURNE II. In this target, the polarization can be maintained in three directions: vertical, horizontal along the beam, or horizontal perpendicular to the beam. The angle of free access is up to 80° from the forward direction to the left and up to 56° or 43° to the right depending on the magnet configuration; the azimuthal angle is 15°. The magnet system is entirely superconducting. The target of about 70 cm3 maximum volume is cooled in a vertical dilution refrigerator. A 14 cm3 target has been used in several experiments with proton and deuteron beams during the 1981–1985 period.

Dynamic nuclear polarization in irradiated ammonia below 0.5 K

Abstract We have reached +90.5% and −93.6% dynamic proton polarization in solid NH3 using paramagnetic radicals created by proton irradiation of 40 Mrad total dose. The dynamic polarization experiments were performed at 25 kG field in a dilution refrigerator. These results may indicate a breakthrough in the development of better polarized target materials for high-energy physics experiments.

A measurement of the ratio of the nucleon structure function in copper and deuterium

Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function,F2, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleons momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects.

EURECA — the European future of cryogenic dark matter searches

EURECA (European Underground Rare Event Calorimeter Array) is a new project, searching for dark matter, with largely the present groups of the CRESST and EDELWEISS experiments and already a few new groups. The aim is to explore scalar cross sections in the 10−9 - 10−10 pico-barn region with a target mass of up to one tonne. A major advantage of EURECA is our planned use of more that just one target material (multi target experiment for WIMP identification). In preparation for this large-scale experiment, R&D for EURECA is provided through the current phases of CRESST and EDELWEISS.

Quantum diffusion of the positive muon in the superconducting state of Al

We report low temperature studies of muon diffusion and trapping in Al doped with Li impurities. The trapping rate at Li and the deduced muon diffusion rate increase more rapidly with decreasing temperature in the superconducting state compared with the normal state. The temperature dependence of the quantum diffusion rate in the superconducting state is close to that predicted by the Kondo theory.

A horizontal dilution refrigerator with very high cooling power

Abstract A horizontal, high cooling power, dilution refrigerator has been built and tested for studying the feasibility of a spin-frozen, polarized proton target to be used at CERN in the Omega spectrometer. In test conditions the following performance was observed: cooling power 6.3 mW at 0.5 K, 2.3 mW at 0.3 K and 0.19 mW at 0.1 K; cooling time 5 min from 0.5 K to 0.1 K and 20 min from 0.1 K to 0.030 K. The lowest temperature in continuous operation was 22 mK. The refrigerator has a tabular counterflow heat exchanger and two discrete, sintered copper heat exchangers of a new type.