Muonium-antimuonium conversion in models with heavy neutrinos

We study muonium-antimuonium conversion and mu+ e- to mu- e+ scattering within two different lepton-flavor-violating models with heavy neutrinos: model I is a typical seesaw that violates lepton number as well as flavor; model II has a neutrino mass texture where lepton number is conserved. We look for the largest possible amplitudes of these processes that are consistent with current bounds. We find that model I has very limited chance of providing an observable signal, except if a finely tuned condition in parameter space occurs. Model II, on the other hand, requires no fine tuning and could cause larger effects. However, the maximum amplitude provided by this model is still two orders of magnitude below the sensitivity of current experiments: one predicts an effective coupling G_MM up to 10^{-4}G_F for heavy neutrino masses near 10 TeV. We have also clarified some discrepancies in previous literature on this subject.Comment: 16 pages, 4 figures, reference adde

Rigorous results on spontaneous symmetry breaking in a one-dimensional driven particle system

We study spontaneous symmetry breaking in a one-dimensional driven two-species stochastic cellular automaton with parallel sublattice update and open boundaries. The dynamics are symmetric with respect to interchange of particles. Starting from an empty initial lattice, the system enters a symmetry broken state after some time T_1 through an amplification loop of initial fluctuations. It remains in the symmetry broken state for a time T_2 through a traffic jam effect. Applying a simple martingale argument, we obtain rigorous asymptotic estimates for the expected times ~ L ln(L) and ln() ~ L, where L is the system size. The actual value of T_1 depends strongly on the initial fluctuation in the amplification loop. Numerical simulations suggest that T_2 is exponentially distributed with a mean that grows exponentially in system size. For the phase transition line we argue and confirm by simulations that the flipping time between sign changes of the difference of particle numbers approaches an algebraic distribution as the system size tends to infinity.Comment: 23 pages, 7 figure

Optical coherence tomography for bladder cancer - ready as a surrogate for optical biopsy? - Results of a prospective mono-centre study

<p>Abstract</p> <p>Introduction</p> <p>New modalities like Optical Coherence Tomography (OCT) allow non-invasive examination of the internal structure of biological tissue in vivo. The potential benefits and limitations of this new technology for the detection and evaluation of bladder cancer were examined in this study.</p> <p>Materials and methods</p> <p>Between January 2007 and January 2008, 52 patients who underwent transurethral bladder biopsy or TUR-BT for surveillance or due to initial suspicion of urothelial carcinoma of the bladder were enrolled in this study. In total, 166 lesions were suspicious for malignancy according to standard white light cystoscopy. All suspicious lesions were scanned and interpreted during perioperative cystoscopy using OCT. Cold cup biopsies and/or TUR-B was performed for all these lesions. For this study we used an OCT-device (Niris^®, Imalux^®, Cleveland, US), that utilizes near-infrared light guided through a flexible fibre-based applicator, which is placed into the bladder via the working channel of the cystoscope. The technology provides high spatial resolution on the order of about 10-20 μm, and a visualization of tissue to a depth of about 2 mm across a lateral span of about 2 mm in width. The device used received market clearance from the FDA and CE approval in Germany. The diagnostic and surgical procedure was videotaped and analyzed afterwards for definitive matching of scanned and biopsied lesion. The primary aim of this study was to determine the level of correlation between OCT interpretation and final histological result.</p> <p>Results</p> <p>Of 166 scanned OCT images, 102 lesions (61.4%) matched to the same site where the biopsy/TUR-BT was taken according to videoanalysis. Only these video-verified lesions were used for further analysis. Of all analyzed lesions 88 were benign (inflammation, edema, hyperplasia etc.) and 14 were malignant (CIS, Ta, T1, T2) as shown by final histo pathology.</p> <p>All 14 malignant lesions were detected correctly by OCT. Furthermore all invasive tumors were staged correctly by OCT regarding tumor growth beyond the lamina propria. There were no false negative lesions detected by OCT. Sensitivity of OCT for detecting the presence of a malignant lesion was 100% and sensitivity for detection of tumor growth beyond the lamina propria was 100% as well. Specificity of OCT for presence of malignancy was 65%, due to the fact that a number of lesions were interpreted as false positive by OCT.</p> <p>Conclusion</p> <p>As a minimally invasive technique, OCT proved to have extremely high sensitivity for detection of malignant lesions as well as estimation of whether a tumor has invaded beyond the lamina propria. However, specificity of OCT within the bladder was impaired (65%), possibly due to a learning curve and/or the relatively low spatial resolution and visualization depth of the OCT technology. Further studies and technical development are needed to establish an adequate surrogate for optical biopsy.</p

JulianA: An automatic treatment planning platform for intensity-modulated proton therapy and its application to intra- and extracerebral neoplasms

Creating high quality treatment plans is crucial for a successful radiotherapy treatment. However, it demands substantial effort and special training for dosimetrists. Existing automated treatment planning systems typically require either an explicit prioritization of planning objectives, human-assigned objective weights, large amounts of historic plans to train an artificial intelligence or long planning times. Many of the existing auto-planning tools are difficult to extend to new planning goals. A new spot weight optimisation algorithm, called JulianA, was developed. The algorithm minimises a scalar loss function that is built only based on the prescribed dose to the tumour and organs at risk (OARs), but does not rely on historic plans. The objective weights in the loss function have default values that do not need to be changed for the patients in our dataset. The system is a versatile tool for researchers and clinicians without specialised programming skills. Extending it is as easy as adding an additional term to the loss function. JulianA was validated on a dataset of 19 patients with intra- and extracerebral neoplasms within the cranial region that had been treated at our institute. For each patient, a reference plan which was delivered to the cancer patient, was exported from our treatment database. Then JulianA created the auto plan using the same beam arrangement. The reference and auto plans were given to a blinded independent reviewer who assessed the acceptability of each plan, ranked the plans and assigned the human-/machine-made labels. The auto plans were considered acceptable in 16 out of 19 patients and at least as good as the reference plan for 11 patients. Whether a plan was crafted by a dosimetrist or JulianA was only recognised for 9 cases. The median time for the spot weight optimisation is approx. 2 min (range: 0.5 min - 7 min)

Aspects of Cooling at the TRIμ\muP Facility

The Tri$\mu$P facility at KVI is dedicated to provide short lived radioactive isotopes at low kinetic energies to users. It comprised different cooling schemes for a variety of energy ranges, from GeV down to the neV scale. The isotopes are produced using beam of the AGOR cyclotron at KVI. They are separated from the primary beam by a magnetic separator. A crucial part of such a facility is the ability to stop and extract isotopes into a low energy beamline which guides them to the experiment. In particular we are investigating stopping in matter and buffer gases. After the extraction the isotopes can be stored in neutral atoms or ion traps for experiments. Our research includes precision studies of nuclear $\beta$-decay through $\beta$-$\nu$ momentum correlations as well as searches for permanent electric dipole moments in heavy atomic systems like radium. Such experiments offer a large potential for discovering new physics.Comment: COOL05 Workshop, Galena, Il, USA, 18-23. Sept. 2005, 5 pages, 3 figure

First Test of Lorentz Invariance in the Weak Decay of Polarized Nuclei

A new test of Lorentz invariance in the weak interactions has been made by searching for variations in the decay rate of spin-polarized 20Na nuclei. This test is unique to Gamow-Teller transitions, as was shown in the framework of a recently developed theory that assumes a Lorentz symmetry breaking background field of tensor nature. The nuclear spins were polarized in the up and down direction, putting a limit on the amplitude of sidereal variations of the form |(\Gamma_{up} - \Gamma_{down})| / (\Gamma_{up} + \Gamma_{down}) < 3 * 10^{-3}. This measurement shows a possible route toward a more detailed testing of Lorentz symmetry in weak interactions.Comment: 11 pages, 6 figure

Spontaneous Symmetry Breaking in a Non-Conserving Two-Species Driven Model

A two species particle model on an open chain with dynamics which is non-conserving in the bulk is introduced. The dynamical rules which define the model obey a symmetry between the two species. The model exhibits a rich behavior which includes spontaneous symmetry breaking and localized shocks. The phase diagram in several regions of parameter space is calculated within mean-field approximation, and compared with Monte-Carlo simulations. In the limit where fluctuations in the number of particles in the system are taken to zero, an exact solution is obtained. We present and analyze a physical picture which serves to explain the different phases of the model

Non-Standard Neutrino Interactions from a Triplet Seesaw Model

We investigate non-standard neutrino interactions (NSIs) in the triplet seesaw model featuring non-trivial correlations between NSI parameters and neutrino masses and mixing parameters. We show that sizable NSIs can be generated as a consequence of a nearly degenerate neutrino mass spectrum. Thus, these NSIs could lead to quite significant signals of lepton flavor violating decays such as \mu^- \to e^- \nu_e anti\nu_\mu and \mu^+ \to e^+ anti\nu_e \nu_\mu at a future neutrino factory, effects adding to the uncertainty in determination of the Earth matter density profile, as well as characteristic patterns of the doubly charged Higgs decays observable at the Large Hadron Collider.Comment: 4 pages, 3 figures and 1 table; v2: minor corrections, Sect. IV revise

Cold Collision Frequency Shift of the 1S-2S Transition in Hydrogen

We have observed the cold collision frequency shift of the 1S-2S transition in trapped spin-polarized atomic hydrogen. We find $\Delta \nu_{1S-2S} = -3.8(8)\times 10^{-10} n Hz cm^3$, where $n$ is the sample density. From this we derive the 1S-2S s-wave triplet scattering length, $a_{1S-2S}=-1.4(3)$ nm, which is in fair agreement with a recent calculation. The shift provides a valuable probe of the distribution of densities in a trapped sample.Comment: Accepted for publication in PRL, 9 pages, 4 PostScript figures, ReVTeX. Updated connection of our measurement to theoretical wor