First-order perturbative calculation of the frequency-shifts caused by static cylindrically-symmetric electric and magnetic imperfections of a Penning trap

The ideal Penning trap consists of a uniform magnetic field and an electrostatic quadrupole potential. Cylindrically-symmetric deviations thereof are parametrized by the coefficients Bn and Cn, respectively. Relativistic mass-increase aside, the three characteristic eigenfrequencies of a charged particle stored in an ideal Penning trap are independent of the three motional amplitudes. This three-fold harmonicity is a highly-coveted virtue for precision experiments that rely on the measurement of at least one eigenfrequency in order to determine fundamental properties of the stored particle, such as its mass. However, higher-order contributions to the ideal fields result in amplitude-dependent frequency-shifts. In turn, these frequency-shifts need to be understood for estimating systematic experimental errors, and eventually for correcting them by means of calibrating the imperfections. The problem of calculating the frequency-shifts caused by small imperfections of a near-ideal trap yields nicely to perturbation theory, producing analytic formulas that are easy to evaluate for the relevant parameters of an experiment. In particular, the frequency-shifts can be understood on physical rather than purely mathematical grounds by considering which terms actually drive them. Based on identifying these terms, we derive general formulas for the first-order frequency-shifts caused by any perturbation parameter Bn or Cn.Comment: 18 pages, 1 figure, 0 tables. Accepted manuscript subsequently published. Streamlined the introduction. Optimized choice of summation variable

Classical calculation of relativistic frequency-shifts in an ideal Penning trap

The ideal Penning trap consists of a uniform magnetic field and an electrostatic quadrupole potential. In the classical low-energy limit, the three characteristic eigenfrequencies of a charged particle trapped in this configuration do not depend on the amplitudes of the three eigenmotions. No matter how accurate the experimental realization of the ideal Penning trap, its harmonicity is ultimately compromised by special relativity. Using a classical formalism of first-order perturbation theory, we calculate the relativistic frequency-shifts associated with the motional degrees of freedom for a spinless particle stored in an ideal Penning trap, and we compare the results with the simple but surprisingly accurate model of relativistic mass-increase.Comment: 8 pages, 0 figures, 1 table; Accepted manuscript subsequently published with a slightly extended description of the perturbative metho

Precision Mass Measurements at THe-Trap and the FSU trap

THe-Trap is a Penning-trap mass spectrometer at the Max-Planck-Institute for Nuclear Physics in Heidelberg, Germany, that aims to measure the T/3He mass ratio with a relative uncertainty of 10^(−11). Improvements of the measurement technique, in particular the measurement of systematic shifts, enabled measurements of mass ratios with relative uncertainties of 7*10^(−11), as demonstrated by a cyclotron frequency ratio determination on 12C4+/16O5+. This uncertainty was limited by the lineshape. An improved theoretical model based on a rotating wave approximation can be used to describe dynamical interactions between the detection system and the ion, in order to better understand the lineshape and to further reduce the uncertainty. The Florida State University trap is a Penning-trap mass spectrometer located in Tallahassee, Florida (USA). In the context of this thesis, three mass ratios were measured, and further 20 mass ratio measurements analyzed, which resulted in the publication of the masses of 82,83Kr, 131,134Xe, 86−88Sr, and 170−174,176Yb with relative uncertainties between (0.9 - 1.3)*10^(−10). These masses serve as reference masses for other experiments and have applications in the determination of the fine-structure constant alpha via the photon-recoil method

EMX2 gene expression predicts liver metastasis and survival in colorectal cancer

Background: The Empty Spiracles Homeobox (EMX-) 2 gene has been associated with regulation of growth and differentiation in neuronal development. While recent studies provide evidence that EMX2 regulates tumorigenesis of various solid tumors, its role in colorectal cancer remains unknown. We aimed to assess the prognostic significance of EMX2 expression in stage III colorectal adenocarcinoma. Methods: Expression levels of EMX2 in human colorectal cancer and adjacent mucosa were assessed by qRT-PCR technology, and results were correlated with clinical and survival data. siRNA-mediated knockdown and adenoviral delivery-mediated overexpression of EMX2 were performed in order to investigate its effects on the migration of colorectal cancer cells in vitro. Results: Compared to corresponding healthy mucosa, colorectal tumor samples had decreased EMX2 expression levels. Furthermore, EMX2 down-regulation in colorectal cancer tissue was associated with distant metastasis (M1) and impaired overall patient survival. In vitro knockdown of EMX2 resulted in increased tumor cell migration. Conversely, overexpression of EMX2 led to an inhibition of tumor cell migration. Conclusions: EMX2 is frequently down-regulated in human colorectal cancer, and down-regulation of EMX2 is a prognostic marker for disease-free and overall survival. EMX2 might thus represent a promising therapeutic target in colorectal cancer

Identification of residues important for NAD+ binding by the Thermotoga maritima α-glucosidase AglA, a member of glycoside hydrolase family 4

AbstractThe NAD+-requiring enzymes of glycoside hydrolase family 4 (GHF4) contain a region with a conserved Gly-XXX-Gly-Ser (GXGS) motif near their N-termini that is reminiscent of the fingerprint region of the Rossmann fold, a conserved structural motif of classical nicotinamide nucleotide-binding proteins. The function of this putative NAD+-binding motif in the α-glucosidase AglA of Thermotoga maritima was probed by directed mutagenesis. The Kd for NAD+ of the AglA mutants G10A, G12A and S13A was increased by about 300-, 5-, and 9-fold, respectively, while their Km for p-nitrophenyl-α-glucopyranoside was not seriously affected. The results indicate that the GXGS motif is indeed important for NAD+ binding by the glycosidases of GHF4

Neutron/Proton Structure Function Ratio at Large x

We re-examine the large-x neutron/proton structure function ratio extracted from the latest deuteron data, taking into account the most recent developments in the treatment of Fermi motion, binding and nucleon off-shell effects in the deuteron. Our findings suggest that as x->1 the ratio of the neutron to proton structure functions (F_2^n/F_2^p) is consistent with the perturbative QCD expectation of 3/7, but larger than the value of 1/4 obtained in earlier analyses.Comment: 18 pages RevTeX, 4 postscript figures, accepted for publication in Phys. Lett.

Confronting Spectral Functions from e+e- Annihilation and tau Decays: Consequences for the Muon Magnetic Moment

Vacuum polarization integrals involve the vector spectral functions which can be experimentally determined from two sources: (i) e+e- annihilation cross sections and (ii) hadronic tau decays. Recently results with comparable precision have become available from CMD-2 on one side, and ALEPH, CLEO and OPAL on the other. The comparison of the respective spectral functions involves a correction from isospin-breaking effects which is evaluated. After correction it is found that the dominant 2pi spectral functions do not agree within experimental and theoretical uncertainties. Some problems are also found for the 4pi spectral functions where different experiments do not agree well with each other. The consequences of these discrepancies for vacuum polarization calculations are presented, with emphasis on the muon anomalous magnetic moment. The work includes a complete reevaluation of all exclusive cross sections, taking into account the most recent data that became available in particular from the Novosibirsk experiments and applying corrections for the missing radiative corrections. The values found for the lowest-order hadronic vacuum polarization contributions are a_mu[had,LO] = (684.7 +- 6.0[exp] +- 3.6[rad])x10^(-10) [e^+e^- -based], and a_mu[had,LO] = (709.0 +- 5.1[exp] +- 1.2[rad] +- 2.8[SU(2)])x10^(-10) [tau-based]. The errors have been separated according to their sources: experimental, radiative corrections in e+e- data, and isospin-breaking. We observe deviations of the full SM prediction with the recent BNL measurement at the 3.0 (e+e-) and 0.9 (tau) sigma level, when adding experimental and theoretical errors in quadrature.Comment: 45 pages, 15 figures; v2: e+e--based evaluation unchanged; modifications of the tau-based estimate: added OPAL data, corrected evaluation of Sew factor, used re-evaluated error matrices in preliminary ALEPH spectral functions; v3: updated arXiv abstract, no changes in result

Physics searches at the LHC

With the LHC up and running, the focus of experimental and theoretical high energy physics will soon turn to an interpretation of LHC data in terms of the physics of electroweak symmetry breaking and the TeV scale. We present here a broad review of models for new TeV-scale physics and their LHC signatures. In addition, we discuss possible new physics signatures and describe how they can be linked to specific models of physics beyond the Standard Model. Finally, we illustrate how the LHC era could culminate in a detailed understanding of the underlying principles of TeV-scale physics.Comment: 184 pages, 55 figures, 14 tables, hundreds of references; scientific feedback is welcome and encouraged. v2: text, references and Overview Table added; feedback still welcom

Bose-Einstein Correlations of Three Charged Pions in Hadronic Z^0 Decays

Bose-Einstein Correlations (BEC) of three identical charged pions were studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP. The genuine three-pion correlations, corrected for the Coulomb effect, were separated from the known two-pion correlations by a new subtraction procedure. A significant genuine three-pion BEC enhancement near threshold was observed having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029 (syst.) fm and a strength of \lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041 (syst.). The Coulomb correction was found to increase the \lambda_3 value by \~9% and to reduce r_3 by ~6%. The measured \lambda_3 corresponds to a value of 0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the three-pion sample purity. A relation between the two-pion and the three-pion source parameters is discussed.Comment: 19 pages, LaTeX, 5 eps figures included, accepted by Eur. Phys. J.

Search for CP Violation in the Decay Z -> b (b bar) g

About three million hadronic decays of the Z collected by ALEPH in the years 1991-1994 are used to search for anomalous CP violation beyond the Standard Model in the decay Z -> b \bar{b} g. The study is performed by analyzing angular correlations between the two quarks and the gluon in three-jet events and by measuring the differential two-jet rate. No signal of CP violation is found. For the combinations of anomalous CP violating couplings, ${\hat{h}}_b = {\hat{h}}_{Ab}g_{Vb}-{\hat{h}}_{Vb}g_{Ab}$ and $h^{\ast}_b = \sqrt{\hat{h}_{Vb}^{2}+\hat{h}_{Ab}^{2}}$, limits of \hat{h}_b < 0.59$and$h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st