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A 25-year old male patient presented with avascular necrosis (AVN) of the trochlea of both elbows following combination chemotherapy for Acute Lymphoblastic Leukaemia (ALL). He had developed restriction of movement in both elbows with little pain. Radiographs confirmed AVN and secondary osteoarthritis of the ulnar-humeral joint. The central part of the trochlea is an area with poor vascularity, due to a blood supply from separate medial and lateral arcades. Treatment was non-operative with a high functional level being maintained., Case Report A 19 year-old, Caucasian man was diagnosed with acute lymphoblastic leukaemia (ALL) in April 2002. He as entered into the UKALL XII protocol, which involved combination chemotherapy, including [...]

The COMPASS experiment at CERN provides hadron identification in a wide momentum range employing a large size gaseous Ring Imaging CHerenkov detector (RICH). The presence of large uncorrelated background in the COMPASS environment was limiting the efficiency of COMPASS RICH-1 in the very forward regime. A major upgrade of RICH-1 required a new technique for Cherenkov photon detection at count rates of several $10^6/{\rm s}$per channel in the central detector part, and a read-out system allowing for trigger rates of up to 100 kHz. To cope with these requirements, the photon detectors of the central region have been replaced with a fast photon detection system described here, while, in the peripheral regions, the existing multi-wire proportional chambers with CsI photo-cathodes have been equipped with a new read-out system based on APV preamplifiers and flash ADC chips. The new system consists of multi-anode photo-multiplier tubes (MAPMTs) coupled to individual fused silica lens telescopes, and fast read-out electronics based on the MAD4 amplifier-discriminator and the dead-time free F1 TDC chip. The project was completely designed and implemented in less than two years: The upgraded detector is in operation since the 2006 CERN SPS run. We present the photon detection design, constructive aspects and test studies to characterise the single photon response of the MAPMTs coupled to the read-out system as well as the detector performance based on the 2006 data.

The resonancelike signal with axial-vector quantum numbers JPC = 1++ at a mass of 1420 MeV and a width of 140 MeV, recently observed by the COMPASS and VES experiments in the f0(980)π final state and tentatively called a1 (1420), is discussed. Instead of a genuine new meson, we interpret this signal as a dynamical effect due to a singularity (branching point) in the triangle diagram formed by the processes a1(1260) → K*K, K* → Kπ, and KK → f0(980) (+c.c). The amplitude for this diagram is calculated. The result exhibits a peak in the intensity with a sharp phase motion with respect to the dominant a1(1260) → ρπ S-wave decay, in good agreement with the data. The branching ratio of a1(1260) → f0(980)π via the triangle diagram is estimated and compared to the dominant decay a1(1260) → ρπ. [ABSTRACT FROM AUTHOR]

The small area tracking system of COMPASS, a new high-luminosity fixed target experiment at CERN''s SPS accelerator, comprises 20 large-size triple GEM (Gas Electron Multiplier) detectors. It was completed and fully operational for the first time for the 2002 muon run. We report on the performance of these chambers in the high-intensity beam and give first results on efficiencies as well as spatial and time resolutions measured for the full set of detectors under various beam conditions. [Copyright &y& Elsevier]

Abstract:: The quenching of metastable states of antiprotonic helium by collisions with hydrogen and deuterium molecules was studied. A systematic investigation of the delayed annihilation time spectra at various H2 and D2 admixture ratios at the ppm level revealed characteristic changes of their shape, which indicated a strong principal and orbital quantum number dependent quenching of levels in both cases. Applying a laser spectroscopy technique to measure the lifetimes of individual states and cascades we deduced H2 and D2 quenching cross-sections for the states (n, l )= (39, 35) and (37, 34). These cross-sections establish for D2 molecules the strong increase of the quenching efficiency with increasing principal quantum number n of the state under investigation previously reported for the case of H2 admixtures. Our experiments indicate that the low-n state (37, 34) is somewhat less affected by D2 than by H2, while the high-n state (39, 35) is equally quenched by both isotopes.

The nucleon density at the nuclear periphery has been investigated with two different methods. The first one is the measurement of the energy shift and the width of antiprotonic X-ray lines. Besides various other nuclides the X-rays from the isotopes 172Yb and 176Yb have been measured very extensively. From these data the absorption widths of six antiprotonic levels and the shifts of the lowest visible transitions could be determined. The comparison of the experimental intensities of the transitions with results from calculations of the antiprotonic cascade showed a good agreement. The second method is the determination of the yield of the annihilation products from the reaction of the antiprotons with nuclei. From this the neutron-to-proton density ratio at a distance of about 3 fm outside the half-density radius can be determined. This method was extended to short-lived residual nuclei with a half-life down to 5 s. The experiment confirmed the previously found negative correlation between the size of the neutron skin and the binding energy of the last neutron. The results have been compared with calculations. For many nuclei a good agreement was found between experiment and calculation, however for some nuclei measured and calculated values are at variance.

The interaction of antiprotonic helium atoms with admixtures of foreign gases was investigated using laser spectroscopy techniques.

In 2002 the COMPASS experiment at CERN has started to take physics data. The fixed target experiment at the SPS uses muon and hadron beams of very high intensity to investigate the structure of the nucleon. For beam definition and small angle tracking silicon microstrip detectors are used. This article describes the current design and the performance of the cryogenic cooling system of these detectors as well as the further development which is underway. [ABSTRACT FROM AUTHOR]

The ANDA fixed target experiment planned at FAIR will investigate fundamental questions of non-perturbative QCD. It makes use of a cooled antiproton beam (momentum: 1.5 to ) and will reach luminosities of up to , yielding a -annihilation rate of . One option for the central tracker of ANDA is a cylindrical, ungated, continuously running TPC with GEM-based gas amplification stage. [ABSTRACT FROM AUTHOR]

We perform an analysis of the three-pion system with quantum numbers JPC=1++ produced in the weak decay of τ leptons. The interaction is known to be dominated by the axial meson a1(1260). We build a model based on approximate three-body unitary and fix the free parameters by fitting it to the ALEPH data on τ-→π-π+π-ντ decay. We then perform the analytic continuation of the amplitude to the complex energy plane. The singularity structures related to the ππ subchannel resonances are carefully addressed. Finally, we extract the a1(1260) pole position mp(a1(1260))-iΓp(a1(1260))/2 with mp(a1(1260))=(1209±4+12-9) MeV, Γp(a1(1260))=(576±11+89-20) MeV. [ABSTRACT FROM AUTHOR]