20,411 research outputs found

    The tauola-photos_F environment for versioning the TAUOLA and PHOTOS packages

    Get PDF
    We present the system for versioning two packages: the TAUOLA of tau lepton decay and PHOTOS for radiative corrections in decays. The following features can be chosen in automatic or semi-automatic way: (1) format of the common block HEPEVT; (2) version of the physics input (for TAUOLA): as published, as initialized by CLEO collaboration, as initialized by ALEPH collaboration (it is suggested to use this version only with the help of the collaboration advice); (3) type of application: stand-alone, universal interface through HEPEVT, interface for KKMC Monte Carlo; (4) random number generators; (5) compiler options.Comment: nine pages, late

    Next Generation Higgs Bosons: Theory, Constraints and Discovery Prospects at the Large Hadron Collider

    Get PDF
    Particle physics model building within the context of string theory suggests that further copies of the Higgs boson sector may be expected. Concerns regarding tree-level flavor changing neutral currents are easiest to allay if little or no couplings of next generation Higgs bosons are allowed to Standard Model fermions. We detail the resulting general Higgs potential and mass spectroscopy in both a Standard Model extension and a supersymmetric extension. We present the important experimental constraints from meson-meson mixing, loop-induced bsγb\to s\gamma decays and LEP2 direct production limits. We investigate the energy range of valid perturbation theory of these ideas. In the supersymmetric context we present a class of examples that marginally aids the fine-tuning problem for parameter space where the lightest Higgs boson mass is greater than the Standard Model limit of 114 GeV. Finally, we study collider physics signatures generic to next generation Higgs bosons, with special emphasis on AhhhZ4b+2lAh\to hhZ\to 4b+2l signal events, and describe the capability of discovery at the Large Hadron Collider.Comment: 43 pages, 12 figures; v3: minor corrections, published in Physical Review

    Prospects for Observing an Invisibly Decaying Higgs Boson in the t anti-t H Production at the LHC

    Full text link
    The prospects for observing an invisibly decaying Higgs boson in the t anti-t H production at LHC are discussed. An isolated lepton, reconstructed hadronic top-quark decay, two identified b-jets and large missing transverse energy are proposed as the final state signature for event selection. Only the Standard Model backgrounds are taken into account. It is shown that the t anti-t Z, t anti-t W, b anti-b Z and b anti-b W backgrounds can individually be suppressed below the signal expectation. The dominant source of background remains the t anti-t production. The key for observability will be an experimental selection which allows further suppression of the contributions from the t anti-t events with one of the top-quarks decaying into a tau lepton. Depending on the details of the final analysis, an excess of the signal events above the Standard Model background of about 10% to 100% can be achieved in the mass range m_H= 100-200 GeV.Comment: Final version as accepted by EPJ

    Implementation of liquid culture for tuberculosis diagnosis in a remote setting: lessons learned.

    Get PDF
    Although sputum smear microscopy is the primary method for tuberculosis (TB) diagnosis in low-resource settings, it has low sensitivity. The World Health Organization recommends the use of liquid culture techniques for TB diagnosis and drug susceptibility testing in low- and middle-income countries. An evaluation of samples from southern Sudan found that culture was able to detect cases of active pulmonary TB and extra-pulmonary TB missed by conventional smear microscopy. However, the long delays involved in obtaining culture results meant that they were usually not clinically useful, and high rates of non-tuberculous mycobacteria isolation made interpretation of results difficult. Improvements in diagnostic capacity and rapid speciation facilities, either on-site or through a local reference laboratory, are crucial

    Linear independence of localized magnon states

    Full text link
    At the magnetic saturation field, certain frustrated lattices have a class of states known as "localized multi-magnon states" as exact ground states. The number of these states scales exponentially with the number NN of spins and hence they have a finite entropy also in the thermodynamic limit NN\to \infty provided they are sufficiently linearly independent. In this article we present rigorous results concerning the linear dependence or independence of localized magnon states and investigate special examples. For large classes of spin lattices including what we called the orthogonal type and the isolated type as well as the kagom\'{e}, the checkerboard and the star lattice we have proven linear independence of all localized multi-magnon states. On the other hand the pyrochlore lattice provides an example of a spin lattice having localized multi-magnon states with considerable linear dependence.Comment: 23 pages, 6 figure

    Machine learning classification: case of Higgs boson CP state in H to tau tau decay at LHC

    Full text link
    Machine Learning (ML) techniques are rapidly finding a place among the methods of High Energy Physics data analysis. Different approaches are explored concerning how much effort should be put into building high-level variables based on physics insight into the problem, and when it is enough to rely on low-level ones, allowing ML methods to find patterns without explicit physics model. In this paper we continue the discussion of previous publications on the CP state of the Higgs boson measurement of the H to tau tau decay channel with the consecutive tau^pm to rho^pm nu; rho^pm to pi^pm pi^0 and tau^pm to a_1^pm nu; a_1^pm to rho^0 pi^pm to 3 pi^pm cascade decays. The discrimination of the Higgs boson CP state is studied as a binary classification problem between CP-even (scalar) and CP-odd (pseudoscalar), using Deep Neural Network (DNN). Improvements on the classification from the constraints on directly non-measurable outgoing neutrinos are discussed. We find, that once added, they enhance the sensitivity sizably, even if only imperfect information is provided. In addition to DNN we also evaluate and compare other ML methods: Boosted Trees (BT), Random Forest (RF) and Support Vector Machine (SVN).Comment: 1+20 pages, 9 figures, 6 tables, extended content and improved readabilit

    Localized-magnon states in strongly frustrated quantum spin lattices

    Get PDF
    Recent developments concerning localized-magnon eigenstates in strongly frustrated spin lattices and their effect on the low-temperature physics of these systems in high magnetic fields are reviewed. After illustrating the construction and the properties of localized-magnon states we describe the plateau and the jump in the magnetization process caused by these states. Considering appropriate lattice deformations fitting to the localized magnons we discuss a spin-Peierls instability in high magnetic fields related to these states. Last but not least we consider the degeneracy of the localized-magnon eigenstates and the related thermodynamics in high magnetic fields. In particular, we discuss the low-temperature maximum in the isothermal entropy versus field curve and the resulting enhanced magnetocaloric effect, which allows efficient magnetic cooling from quite large temperatures down to very low ones.Comment: 21 pages, 10 figures, invited paper for a special issue of "Low Temperature Physics " dedicated to the 70-th anniversary of creation of concept "antiferromagnetism" in physics of magnetis

    Frustrated Heisenberg antiferromagnet on the honeycomb lattice: Spin gap and low-energy parameters

    Full text link
    We use the coupled cluster method implemented to high orders of approximation to investigate the frustrated spin-12\frac{1}{2} J1J_{1}--J2J_{2}--J3J_{3} antiferromagnet on the honeycomb lattice with isotropic Heisenberg interactions of strength J1>0J_{1} > 0 between nearest-neighbor pairs, J2>0J_{2}>0 between next-nearest-neighbor pairs, and J3>0J_{3}>0 between next-next-neareast-neighbor pairs of spins. In particular, we study both the ground-state (GS) and lowest-lying triplet excited-state properties in the case J3=J2κJ1J_{3}=J_{2} \equiv \kappa J_{1}, in the window 0κ10 \leq \kappa \leq 1 of the frustration parameter, which includes the (tricritical) point of maximum classical frustration at κcl=12\kappa_{{\rm cl}} = \frac{1}{2}. We present GS results for the spin stiffness, ρs\rho_{s}, and the zero-field uniform magnetic susceptibility, χ\chi, which complement our earlier results for the GS energy per spin, E/NE/N, and staggered magnetization, MM, to yield a complete set of accurate low-energy parameters for the model. Our results all point towards a phase diagram containing two quasiclassical antiferromagnetic phases, one with N\'eel order for κ<κc1\kappa < \kappa_{c_{1}}, and the other with collinear striped order for κ>κc2\kappa > \kappa_{c_{2}}. The results for both χ\chi and the spin gap Δ\Delta provide compelling evidence for a quantum paramagnetic phase that is gapped over a considerable portion of the intermediate region κc1<κ<κc2\kappa_{c_{1}} < \kappa < \kappa_{c_{2}}, especially close to the two quantum critical points at κc1\kappa_{c_{1}} and κc2\kappa_{c_{2}}. Each of our fully independent sets of results for the low-energy parameters is consistent with the values κc1=0.45±0.02\kappa_{c_{1}} = 0.45 \pm 0.02 and κc2=0.60±0.02\kappa_{c_{2}} = 0.60 \pm 0.02, and with the transition at κc1\kappa_{c_{1}} being of continuous (and probably of the deconfined) type and that at κc2\kappa_{c_{2}} being of first-order type

    A solvable model of a random spin-1/2 XY chain

    Full text link
    The paper presents exact calculations of thermodynamic quantities for the spin-1/2 isotropic XY chain with random lorentzian intersite interaction and transverse field that depends linearly on the surrounding intersite interactions.Comment: 14 pages (Latex), 2 tables, 13 ps-figures included, (accepted for publication in Phys.Rev.B

    О влиянии свойств инструментального материала на усадку стружки при резании сталей

    Get PDF
    The exploitation of solar power for energy supply is of increasing importance. While technical development mainly takes place in the engineering disciplines, computer science offers adequate techniques for simulation, optimisation and controller synthesis. In this paper we describe a work from this interdisciplinary area. We introduce our tool for the optimisation of parameterised solar thermal power plants, and report on the employment of genetic algorithms and neural networks for parameter synthesis. Experimental results show the applicability of our approach
    corecore