The EPR-type strangeness correlation in the K K system produced in the reaction pp ™ K K at rest has been tested using the CPLEAR detector. The strangeness was tagged via strong interaction with absorbers away from the creation point. The results are consistent with the QM non-separability of the wave function and exclude a spontaneous wave-function Ž . factorisation at creation CL ) 99.99% . q 1998 Elsevier Science B.V.

We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of K 0 0 0 transforming into K and K into K as a function of the neutral-kaon eigentime t. The comparison is based on the analysis of the neutral-kaon semileptonic decays recorded in the CPLEAR experiment. There, the strangeness of the neutral kaon at ". 0 0 was measured over the interval 1 tt-20 t , thus leading to evidence for time-reversal non-invariance.

Today, PET and SPECT tracers cannot be imaged simultaneously at high resolutions but require 2 separate imaging systems. This paper introduces a Versatile Emission Computed Tomography system (VECTor) for radionuclides that enables simultaneous submillimeter imaging of single-photon and positron-emitting radiolabeled molecules. Methods: g-photons produced both by electron-positron annihilation and by single-photon emitters are projected onto the same detectors by means of a novel cylindric high-energy collimator containing 162 narrow pinholes that are grouped in clusters. This collimator is placed in an existing SPECT system (U-SPECT-II) with 3 large-field-of-view g-detectors. From the acquired projections, PET and SPECT images are obtained using statistical image reconstruction that corrects for energy-dependent system blurring. Results: For PET tracers, the tomographic resolution obtained with a Jaszczak hot rod phantom was less than 0.8 mm, and 0.5-mm resolution images of SPECT tracers were acquired simultaneously. SPECT images were barely degraded by the simultaneous presence of a PET tracer, even when the activity concentration of the PET tracer exceeded that of the SPECT tracer by up to a factor of 2.5. Furthermore, we simultaneously acquired fully registered 3-and 4-dimensional multiple functional images from living mice that, in the past, could be obtained only sequentially. Conclusion: High-resolution complementary information about tissue function contained in SPECT and PET tracer distributions can now be obtained simultaneously using a fully integrated imaging device. These combined unique capabilities pave the way for new perspectives in imaging the biologic systems of rodents.

We use ts to recent published CPLEAR data on neutral kaon decays to + and e to constrain the CPT{violation parameters appearing in a formulation of the neutral kaon system as an open quantum-mechanical system. The obtained upper limits of the CPT{violation parameters are approaching the range suggested by certain ideas concerning quantum gravity.

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The potential of tumour tracking for active spot-scanned proton therapy was assessed. Using a 4D-dose calculation and simulated target motion, a tumour tracking algorithm has been implemented and applied to a simple target volume in both homogenous and heterogeneous in silico phantoms. For tracking and retracking (a hybrid solution combining tumour tracking and rescanning), three tracking modes were analysed: 'no tracking' (uncorrected irradiation of a moving target), 'perfect tracking' (no time delays and exact knowledge of target position) and 'imperfect tracking' (simulated time delays or position prediction errors). For all plans, dose homogeneity in the target volume was assessed as the difference between D5 and D95 in the CTV. For the homogeneous phantom, perfect tracking could retrieve nominal dose homogeneity for all motion phases and amplitudes while severe deterioration of treatment outcomes was found for imperfect tracking. The use of retracking reduced the sensitivity to position errors significantly in the homogeneous phantom. In the heterogeneous phantoms (simulated rib proximal to target), the nominal dose homogeneity could not be obtained with perfect tracking. Adjustments in pencil beam positions could cause pencil beams to deform under the influence of the bone, resulting in loss of dose homogeneity. As retracking was not capable of reducing these effects, rescanning provided the best treatment outcomes for moving heterogeneous targets in this study.

A two-dimensional position sensitive dosimetry system based on a scintillating gas detector has been developed for pre-treatment verification of dose distributions in hadron therapy. The dosimetry system consists of a chamber filled with an Ar/CF 4 scintillating gas mixture, inside which two cascaded gas electron multipliers (GEMs) are mounted. A GEM is a thin kapton foil with copper cladding structured with a regular pattern of sub-mm holes. The primary electrons, created in the detector's sensitive volume by the incoming beam, drift in an electric field towards the GEMs and undergo gas multiplication in the GEM holes. During this process, photons are emitted by the excited Ar/CF 4 gas molecules and detected by a mirror-lens-CCD camera system. Since the amount of emitted light is proportional to the dose deposited in the sensitive volume of the detector by the incoming beam, the intensity distribution of the measured light spot is proportional to the 2D hadron dose distribution. For a measurement of a 3D dose distribution, the scintillating gas detector is mounted at the beam exit side of a water-bellows phantom, whose thickness can be varied in steps. In this work, the energy dependence of the output signal of the scintillating gas detector has been verified in a 250 MeV/u clinical 12 C ion beam by means of a depth-dose curve measurement. The underestimation of the measured signal at the Bragg peak depth is only 9% with respect to an airfilled ionization chamber. This is much smaller than the underestimation found for a scintillating Gd 2 O 2 S:Tb ('Lanex') screen under the same measurement conditions (43%). Consequently, the scintillating gas detector is a promising device for verifying dose distributions in high LET beams, for example to check hadron therapy treatment plans which comprise beams with different energies.

Determination of the T-and CPT-violation parameters in the neutral-kaon system using theBell-Steinberger relation and data from CPLEAR. CPLEAR CollaborationA. Apostolakis 1) , E. Aslanides 11) , G. Backenstoss 2) , P. AbstractData from the CPLEAR experiment, together with the most recent world averages for some of the neutral-kaon parameters, were constrained with the Bell-Steinberger (or unitarity) relation, allowing the T-violation parameter Re( ) and the CPT-violation parameter Im(δ) of the neutral-kaon mixing matrix to be determined with an increased accuracy:−5 . Moreover, the constraint allows the CPT-violation parameter for the neutralkaon semileptonic decays, Re(y), to be determined for the first time. The ∆S = ∆Q parameters Re(x − ) and Im(x + ) are given with an increased accuracy. The quantity Re(y + x − ), which enters the T-violation CPLEAR asymmetry previously published, is determined to be (0.2 ± 0.3) × 10 −3 . The value obtained for Re(δ) is in agreement with the one resulting from a previous unconstrained fit and has a slightly smaller error. (Submitted to Physics Letters B) IntroductionThe CPLEAR experiment has directly measured for the first time the violation of T invariance in the neutral-kaon system [1] and has provided a new, more accurate limit for the CPT-violation parameter Re(δ) [2]. These results were obtained by analysing the rate asymmetries between K 0 and K 0 for decays to e ± π ∓ ν, as a function of the decay time t = τ .In continuation of this work we have studied the constraints on our results deriving from the Bell-Steinberger (or unitarity) relation [3][4][5]. The Bell-Steinberger relation relates all decay channels of neutral kaons to the parameters describing T and CPT non-invariance. With the present precision of the two-pion decay parameters the dominant uncertainties arise from the three-pion and semileptonic decays. Moreover, the semileptonic decays enter the relation with the parameter Re(y), describing CPT violation in semileptonic decays and as yet not measured. Having improved the precision of three-pion decays [7,8] and measured precisely the semileptonic decay rates, CPLEAR allows the determination of all parameters with an unprecedented accuracy. We stress here that they are obtained free of theoretical assumptions, apart from unitarity, unlike others obtained previously also using the unitarity relation [6].