Helicity Analysis of Semileptonic Hyperon Decays Including Lepton Mass Effects

Using the helicity method we derive complete formulas for the joint angular decay distributions occurring in semileptonic hyperon decays including lepton mass and polarization effects. Compared to the traditional covariant calculation the helicity method allows one to organize the calculation of the angular decay distributions in a very compact and efficient way. In the helicity method the angular analysis is of cascade type, i.e. each decay in the decay chain is analyzed in the respective rest system of that particle. Such an approach is ideally suited as input for a Monte Carlo event generation program. As a specific example we take the decay $\Xi^0 \to \Sigma^+ + l^- + \bar{\nu}_l$ ($l^-=e^-, \mu^-$) followed by the nonleptonic decay $\Sigma^+ \to p + \pi^0$ for which we show a few examples of decay distributions which are generated from a Monte Carlo program based on the formulas presented in this paper. All the results of this paper are also applicable to the semileptonic and nonleptonic decays of ground state charm and bottom baryons, and to the decays of the top quark.Comment: Published version. 40 pages, 11 figures included in the text. Typos corrected, comments added, references added and update

Latitudinal decline in stand biomass and productivity at the elevational treeline in the Ural mountains despite a common thermal growth limit

Aim: To quantify tree biomass and stand productivity of treeline ecotones and identify driving factors. Location: treeline ecotones of seven regions from the South to Polar Urals, spanning a latitudinal gradient of 1,500 km. Taxa: Picea obovata, Betula pubescens, Larix sibirica. Methods: Stand biomass and productivity were estimated across 18 elevational transects from the tree species line to the closed forest line based on allometric measurements of 326 trees (including roots for 53 trees), stand structure assessments and demographic patterns of 20,600 trees. Stand growth data were linked to (a) temperatures monitored in situ for five years in the South and Polar Urals, (b) climate variables extrapolated from nearby climate stations and (c) measures of nutrient availability in soils and tree foliage. Results: treeline position along the latitudinal gradient occurred at a similar mean growing season temperature. Despite the common cold limitation of tree distribution along the Ural mountain range, stand biomass and productivity within the treeline ecotone decreased by a factor of three and five from the South to the Polar Urals, mainly due to a declining stand density. Among climatic variables, growing season length decreased by 20% and winter temperatures declined by 4°C towards the Polar Urals, whereas growing degree days > 5°C remained similar, averaging 554 ± 9°C. Soil development was poorer in the Polar than in the South Urals, and plant-available N and P in the soil were 20 and 30 times lower, respectively, probably due to lower winter temperatures. Main conclusions: Our results suggest that once the thermal limitation for tree growth is relieved, soil fertility—restricted by permafrost and low soil temperatures during winter—plays a key and yet underexplored role for stand productivity in treeline ecotones. The observed latitudinal decline in stand productivity is important for above- and belowground diversity and functioning. © 2020 The Authors. Journal of Biogeography published by John Wiley & Sons Lt

Drell-Yan forward-backward and spin asymmetries for arbitrary vector boson production at next-to-leading order

Longitudinally polarized, unpolarized and forward-backward mass differential cross sections for Drell-Yan lepton-pair production by arbitrary vector bosons are calculated in next-to-leading order (NLO) QCD. Analytical results are presented in a form valid for all consistent $n$-dimensional regularization schemes, with the mass factorization scheme kept general. NLO predictions for all Drell-Yan type processes ($W^\pm$, $Z$ and $\gamma^*$) at BNL's relativistic heavy ion collider (RHIC) are made using polarized parton distributions which fit the recent deep-inelastic scattering data. These are examined as tools in the determination of the polarized parton distributions and the unpolarized $\bar{u}/\bar{d}$ ratio. NLO predictions for the forward-backward lepton asymmetry at Fermilab are made and the precision determination of $\sin^2 \theta_W$ from future runs is studied. In all the above, the QCD corrections are found to be significant. An introductory discussion is given of various theoretical issues, such as allowable factorization and regularization schemes, and scale dependences.Comment: 34 pages, figures included, revtex. Some discussions and references added/modified. In more compact form. To appear in Phys. Rev.

Weak magnetic dipole moments in two-Higgs-doublet models

We investigate the effects of the new scalars in a two-Higgs-doublet model on the weak magnetic dipole moments of the fermions at the $Z$ peak. Proportionality of the Yukawa couplings to the fermion masses, and to $\tan{\beta}$, makes such effects more important for the third family, and potentially relevant. For the $\tau$ lepton, the new diagrams are suppressed by $v_\tau = 2 \sin^2 \theta_W - 1/2$, or by powers of $m_\tau/M_Z$, but may still be comparable to the SM electroweak contributions. In contrast, we find that the new contributions for the bottom quark may be much larger than the SM electroweak contributions. These new effects may even compete with the gluonic contribution, if the extra scalars are light and $\tan \beta$ is large. We also comment on the problem of the gauge dependence of the vertex, arising when the $Z$ is off mass shell. We compute the contributions from the new scalars to the magnetic dipole moments for top-quark production at the NLC, and for bottom and $\tau$ production at LEP2. In the case of the top, we find that the SM electroweak and gluonic contributions to the $Z t {\bar t}$ vertex are comparable. The new contributions may be of the same order of magnitude as the standard-model ones, but not much larger.Comment: 17 pages, LaTex, 8 figures available upon reques

Laurent series expansion of a class of massive scalar one-loop integrals to ${\cal O}(\ep^2)

We use dimensional regularization to calculate the {\cal O}(\ep^2) expansion of all scalar one-loop one-, two-, three- and four-point integrals that are needed in the calculation of hadronic heavy quark production. The Laurent series up to {\cal O}(\ep^2) is needed as input to that part of the NNLO corrections to heavy flavor production at hadron colliders where the one-loop integrals appear in the loop-by-loop contributions. The four-point integrals are the most complicated. The {\cal O}(\ep^2) expansion of the three- and four-point integrals contains in general polylogarithms up to ${\rm Li}_4$ and functions related to multiple polylogarithms of maximal weight and depth four.Comment: 48 pages, 4 figures in the text, slight change in the title, one reference added, matches published versio

The quantum state vector in phase space and Gabor's windowed Fourier transform

Representations of quantum state vectors by complex phase space amplitudes, complementing the description of the density operator by the Wigner function, have been defined by applying the Weyl-Wigner transform to dyadic operators, linear in the state vector and anti-linear in a fixed `window state vector'. Here aspects of this construction are explored, with emphasis on the connection with Gabor's `windowed Fourier transform'. The amplitudes that arise for simple quantum states from various choices of window are presented as illustrations. Generalized Bargmann representations of the state vector appear as special cases, associated with Gaussian windows. For every choice of window, amplitudes lie in a corresponding linear subspace of square-integrable functions on phase space. A generalized Born interpretation of amplitudes is described, with both the Wigner function and a generalized Husimi function appearing as quantities linear in an amplitude and anti-linear in its complex conjugate. Schr\"odinger's time-dependent and time-independent equations are represented on phase space amplitudes, and their solutions described in simple cases.Comment: 36 pages, 6 figures. Revised in light of referees' comments, and further references adde

Heavy-Higgs Lifetime at Two Loops

The Standard-Model Higgs boson with mass $M_H >> 2M_Z$ decays almost exclusively to pairs of $W$ and $Z$ bosons. We calculate the dominant two-loop corrections of $O( G_F^2 M_H^4 )$ to the partial widths of these decays. In the on-mass-shell renormalization scheme, the correction factor is found to be $1 + 14.6$, where the second term is the one-loop correction. We give full analytic results for all divergent two-loop Feynman diagrams. A subset of finite two-loop vertex diagrams is computed to high precision using numerical techniques. We find agreement with a previous numerical analysis. The above correction factor is also in line with a recent lattice calculation.Comment: 26 pages, 6 postscript figures. The complete paper including figures is also available via WWW at http://www.physik.tu-muenchen.de/tumphy/d/T30d/PAPERS/TUM-HEP-247-96.ps.g

Holder exponents of irregular signals and local fractional derivatives

It has been recognized recently that fractional calculus is useful for handling scaling structures and processes. We begin this survey by pointing out the relevance of the subject to physical situations. Then the essential definitions and formulae from fractional calculus are summarized and their immediate use in the study of scaling in physical systems is given. This is followed by a brief summary of classical results. The main theme of the review rests on the notion of local fractional derivatives. There is a direct connection between local fractional differentiability properties and the dimensions/ local Holder exponents of nowhere differentiable functions. It is argued that local fractional derivatives provide a powerful tool to analyse the pointwise behaviour of irregular signals and functions.Comment: 20 pages, Late

Search for light-to-heavy quark flavor changing neutral currents in νμN\nu _{\mu}N and νˉμN\bar{\nu}_{\mu}N scattering at the Tevatron

We report on a search for flavor-changing neutral-currents (FCNC) in the production of heavy quarks in deep inelastic $\nu_{\mu}N$ and $\bar{\nu}_{\mu}N$ scattering by the NuTeV experiment at the Fermilab Tevatron. This measurement, made possible by the high-purity NuTeV sign-selected beams, probes for FCNC in heavy flavors at the quark level and is uniquely sensitive to neutrino couplings of potential FCNC mediators. All searches are consistent with zero, and limits on the effective mixing strengths $$, $| V_{db}| ^{2}$, and $| V_{sb}| ^{2}$ are obtained

Experiences in managing problematic crystal methamphetamine use and associated depression in gay men and HIV positive men: in-depth interviews with general practitioners in Sydney, Australia

© 2008 Saltman et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background This paper describes the experiences of Australian general practitioners (GPs) in managing problematic crystal methamphetamine (crystal meth) use among two groups of male patients: gay men and HIV positive men. Methods Semi-structured qualitative interviews with GPs with HIV medication prescribing rights were conducted in Sydney, Adelaide and a rural-coastal town in New South Wales between August and October 2006. Participants were recruited from practices with high caseloads of gay and HIV positive men. Results Sixteen GPs were recruited from seven practices to take part in interviews. Participants included 14 male GPs and two female GPs, and the number of years each had been working in HIV medicine ranged from two to 24. Eleven of the GPs who were based in Sydney raised the issue of problematic crystal meth use in these two patient populations. Five key themes were identified: an increasing problem; associations with depression; treatment challenges; health services and health care; workforce issues. Conclusion Despite study limitations, key implications can be identified. Health practitioners may benefit from broadening their understandings of how to anticipate and respond to problematic levels of crystal meth use in their patients. Early intervention can mitigate the impact of crystal meth use on co-morbid mental illness and other health issues. Management of the complex relationships between drug use, depression, sexuality and HIV can be addressed following a 'stepped care' approach. General practice guidelines for the management of crystal meth use problems should address specific issues associated with gay men and HIV positive men. GPs and other health practitioners must appreciate drug use as a social practice in order to build trust with gay men to encourage full disclosure of drug use. Education programs should train health practitioners in these issues, and increased resourcing provided to support the often difficult task of caring for people who use crystal meth. Greater resourcing of acute care and referral services can shift the burden away from primary care and community services. Further investigation should consider whether these findings are reproducible in other general practice settings, the relationship between depression, drug use and HIV medication, and challenges facing the HIV general practice workforce in Australia