Measurement of the Omega_c Lifetime

We present the measurement of the lifetime of the Omega_c we have performed using three independent data samples from two different decay modes. Using a Sigma- beam of 340 GeV/c we have obtained clean signals for the Omega_c decaying into Xi- K- pi+ pi+ and Omega- pi+ pi- pi+, avoiding topological cuts normally used in charm analysis. The short but measurable lifetime of the Omega_c is demonstrated by a clear enhancement of the signals at short but finite decay lengths. Using a continuous maximum likelihood method we determined the lifetime to be tau(Omega_c) = 55 +13-11(stat) +18-23(syst) fs. This makes the Omega_c the shortest living weakly decaying particle observed so far. The short value of the lifetime confirms the predicted pattern of the charmed baryon lifetimes and demonstrates that the strong interaction plays a vital role in the lifetimes of charmed hadrons.Comment: 15 pages, including 7 figures; gzipped, uuencoded postscrip

Search for the exotic Ξ−−(1860)\Xi^{--}(1860) Resonance in 340GeV/c Σ−\Sigma^--Nucleus Interactions

We report on a high statistics search for the $\Xi^{--}(1860)$ resonance in $\Sigma^-$-nucleus collisions at 340GeV/c. No evidence for this resonance is found in our data sample which contains 676000 $\Xi^-$ candidates above background. For the decay channel $\Xi^{--}(1860) \to \Xi^-\pi^-$ and the kinematic range 0.15$<x_F<$0.9 we find a 3$\sigma$ upper limit for the production cross section of 3.1 and 3.5 $\mu$b per nucleon for reactions with carbon and copper, respectively.Comment: 5 pages, 4 figures, modification of ref. 43 and 4

Charge Asymmetries for D, D_s and Lambda_c Production in Sigma- - Nucleus Interactions at 340 GeV/c

CERN experiment WA89 has studied charmed particles produced by a Sigma^- beam at 340 GeV/c on nuclear targets. Production of particles which have light quarks in common with the beam is compared to production of those which do not. Considerable production asymmetries between D^- and D^p, D_s^ and D_s^+ and Lambda_c and Antilambda_c are observed. The results are compared with pion beam data and with theoretical calculations.Comment: LaTeX ; 16 pages including 4 ps figure

Intrafraction motion of the prostate during an IMRT session: a fiducial-based 3D measurement with Cone-beam CT

Background: Image-guidance systems allow accurate interfractional repositioning of IMRT treatments, however, these may require up to 15 minutes. Therefore intrafraction motion might have an impact on treatment precision. 3D geometric data regarding intrafraction prostate motion are rare; we therefore assessed its magnitude with pre- and post-treatment fiducial-based imaging with cone-beam-CT (CBCT). Methods: 39 IMRT fractions in 5 prostate cancer patients after (125)I-seed implantation were evaluated. Patient position was corrected based on the (125)I-seeds after pre-treatment CBCT. Immediately after treatment delivery, a second CBCT was performed. Differences in bone- and fiducial position were measured by seed-based grey-value matching. Results: Fraction time was 13.6 +/- 1.6 minutes. Median overall displacement vector length of (125)Iseeds was 3 mm (M = 3 mm, Sigma = 0.9 mm, sigma = 1.7 mm; M: group systematic error, Sigma: SD of systematic error, sigma: SD of random error). Median displacement vector of bony structures was 1.84 mm (M = 2.9 mm, Sigma = 1 mm, sigma = 3.2 mm). Median displacement vector length of the prostate relative to bony structures was 1.9 mm (M = 3 mm, Sigma = 1.3 mm, sigma = 2.6 mm). Conclusion: a) Overall displacement vector length during an IMRT session is &lt; 3 mm. b) Positioning devices reducing intrafraction bony displacements can further reduce overall intrafraction motion. c) Intrafraction prostate motion relative to bony structures is &lt; 2 mm and may be further reduced by institutional protocols and reduction of IMRT duration

Search for the pentaquark candidate Θ+\Theta^+(1540) in the hyperon beam experiment WA89

We report on a high-statistics search for the \t1540 resonance in $\Sigma^-$-nucleus collisions at 340 \gevc1 . No evidence for this resonance was found in our data sample which contains 13 millions $K^0_s \to \pi^+\pi^-$ decays above background. For the decay channel $\Theta^+ \to K^0_s p$ and the kinematic range $x_F>$ 0.05 we find the production cross section to be $BR(\Theta^+ \to K^0_s p)\cdot \sigma_0 <$ 1.8 $\mu$b per nucleon at 99% CL.Comment: 5 pages, 4 figure

Effect of methylene blue on the genomic response to reperfusion injury induced by cardiac arrest and cardiopulmonary resuscitation in porcine brain

<p>Abstract</p> <p>Background</p> <p>Cerebral ischemia/reperfusion injury is a common secondary effect of cardiac arrest which is largely responsible for postresuscitative mortality. Therefore development of therapies which restore and protect the brain function after cardiac arrest is essential. Methylene blue (MB) has been experimentally proven neuroprotective in a porcine model of global ischemia-reperfusion in experimental cardiac arrest. However, no comprehensive analyses have been conducted at gene expression level.</p> <p>Methods</p> <p>Pigs underwent either untreated cardiac arrest (CA) or CA with subsequent cardiopulmonary resuscitation (CPR) accompanied with an infusion of saline or an infusion of saline with MB. Genome-wide transcriptional profiling using the Affymetrix porcine microarray was performed to 1) gain understanding of delayed neuronal death initiation in porcine brain during ischemia and after 30, 60 and 180 min following reperfusion, and 2) identify the mechanisms behind the neuroprotective effect of MB after ischemic injury (at 30, 60 and 180 min).</p> <p>Results</p> <p>Our results show that restoration of spontaneous circulation (ROSC) induces major transcriptional changes related to stress response, inflammation, apoptosis and even cytoprotection. In contrast, the untreated ischemic and anoxic insult affected only few genes mainly involved in intra-/extracellular ionic balance. Furthermore, our data show that the neuroprotective role of MB is diverse and fulfilled by regulation of the expression of soluble guanylate cyclase and biological processes accountable for inhibition of apoptosis, modulation of stress response, neurogenesis and neuroprotection.</p> <p>Conclusions</p> <p>Our results support that MB could be a valuable intervention and should be investigated as a therapeutic agent against neural damage associated with I/R injury induced by cardiac arrest.</p

Total charm production cross section and production asymmetries in 340 GeV/c Σ−\Sigma^{-} nucleus interactions

CERN experiment WA89 uses a Sigma /sup -/ beam at 340 GeV/c to study the production of charmed particles. Based on the reconstruction of all final charm states from the full data sample of our '93 and '94 beamtimes the total $9 cc-cross section has been determined. Production of particles which have a light quark in common with the beam is compared to production of those which do not. Considerable production asymmetries between D/sup -/ and D/sup +/, D/sub$9 s//sup -/ and D/sub s//sup +/, and Lambda /sub c/ and Lambda /sub c/ are observed. (3 refs)

Total Charm Production Cross Section and Production Asymmetries in 340

Introduction The examination of charm production can play a key role in the understanding of heavy hadron production. On one hand, charmed hadrons are experimentally accessible with reasonable statistics, on the other hand they are also heavy enough that the theoretical description of charmed hadron production can be splitted into a hard process which describes the production of the c¯c-pair itself, and a soft part, describing the subsequent fragmentation into hadrons. The total c¯c-pair production cross section has been calculated in the framework of perturbative QCD up to next to leading order. The subsequent fragmentation process is too soft to be described with perturbative methods. Therefore only empirical models exist so far. As one might naively expect final states, which show a quark flavour overlap with the beam particle, inherit part of the beam momentum and thus preferably hadronize at higher momenta.