2,647 research outputs found
Leptoquarks decaying to a top quark and a charged lepton at hadron colliders
We study the sensitivity of the Tevatron and the 7 TeV LHC to a leptoquark S
coupling to a top quark and a charged lepton L (= e, mu, or tau). For the
Tevatron, we focus on the case m_S < m_t, where the leptoquark pair production
cross section is large, and the decay is three-body: S --> W b L^{\pm}. We
argue that existing Tevatron observations could exclude m_S \lsim 160 GeV. For
m_S > m_t, we show that the LHC experiments with low integrated luminosity
could be sensitive to such leptoquarks decaying to tl^{\pm} with l= mu or tau.Comment: 13 pages, 6 figures, minor changes (typos
Low energy n-\nuc{3}{H} scattering : a novel testground for nuclear interaction
The low energy n-\nuc{3}{H} elastic cross sections near the resonance peak
are calculated by solving the 4-nucleon problem with realistic NN interactions.
Three different methods -- Alt, Grassberger and Shandas (AGS), Hyperspherical
Harmonics and Faddeev-Yakubovsky -- have been used and their respective results
are compared. We conclude on a failure of the existing NN forces to reproduce
the n-\nuc{3}{H} total cross section.Comment: To be published in Phys. Rev.
Fractional Laplacian in Bounded Domains
The fractional Laplacian operator, ,
appears in a wide class of physical systems, including L\'evy flights and
stochastic interfaces. In this paper, we provide a discretized version of this
operator which is well suited to deal with boundary conditions on a finite
interval. The implementation of boundary conditions is justified by appealing
to two physical models, namely hopping particles and elastic springs. The
eigenvalues and eigenfunctions in a bounded domain are then obtained
numerically for different boundary conditions. Some analytical results
concerning the structure of the eigenvalues spectrum are also obtained.Comment: 11 pages, 11 figure
Solutions of the Faddeev-Yakubovsky equations for the four nucleons scattering states
The Faddeev-Yakubowsky equations in configuration space have been solved for
the four nucleon system. The results with an S-wave interaction model in the
isospin approximation are presented. They concern the bound and scattering
states below the first three-body threshold. The elastic phase-shifts for the
N+NNN reaction in different () channels are given and the corresponding
low energy expansions are discussed. Particular attention is payed to the n+t
elastic cross section. Its resonant structure is well described in terms of a
simple NN interaction. First results concerning the S-matrix for the coupled
N+NNN-NN+NN channels and the strong deuteron-deuteron scattering length are
obtained.Comment: latex.tar.gz, 36 pages, 10 figures, 11 tables. To be published in
Physical Review
Few-nucleon systems in translationally invariant harmonic oscillator basis
We present a translationally invariant formulation of the no-core shell model
approach for few-nucleon systems. We discuss a general method of
antisymmetrization of the harmonic-oscillator basis depending on Jacobi
coordinates. The use of a translationally invariant basis allows us to employ
larger model spaces than in traditional shell-model calculations. Moreover, in
addition to two-body effective interactions, three- or higher-body effective
interactions as well as real three-body interactions can be utilized. In the
present study we apply the formalism to solve three and four nucleon systems
interacting by the CD-Bonn nucleon-nucleon potential. Results of ground-state
as well as excited-state energies, rms radii and magnetic moments are
discussed. In addition, we compare charge form factor results obtained using
the CD-Bonn and Argonne V8' NN potentials.Comment: 25 pages. RevTex. 13 Postscript figure
Conducting research with individuals at risk for suicide: protocol for assessment and risk management
Published in final edited form as: Suicide Life Threat Behav. 2020 April ; 50(2): 461–471. doi:10.1111/sltb.12602.OBJECTIVE: Suicide prediction, prevention, and intervention are urgent research areas. One barrier for research with high‐risk populations is limited resources to manage risk in a research setting. We describe using the University of Washington Risk Assessment Protocol (UWRAP) to assess and manage suicide risk during phone‐administered eligibility assessments in two clinical trials.
METHOD: Study 1 (N = 151) recruited suicidal adults who were not engaged in mental health treatment and Study 2 (N = 135) recruited suicidal adults who used alcohol to regulate emotions. Pre‐ and postassessment ratings of stress, urge to harm self, urge to use drugs/alcohol, and intent to harm self were compared and strategies to manage increased suicide risk following screening interviews were implemented, as indicated.
RESULTS: In both studies, average postassessment ratings were significantly lower than pre‐assessment. A minority of participants reported higher ratings on one or more domains; however, following more thorough suicide risk assessment, risk was appropriately managed by providing low‐level interventions (e.g., validation).
CONCLUSIONS: Suicide risk in research involving community participants can be managed by using appropriate risk protocols.Published versio
The Price of WMAP Inflation in Supergravity
The three-year data from WMAP are in stunning agreement with the simplest
possible quadratic potential for chaotic inflation, as well as with new or
symmetry-breaking inflation. We investigate the possibilities for incorporating
these potentials within supergravity, particularly of the no-scale type that is
motivated by string theory. Models with inflation driven by the matter sector
may be constructed in no-scale supergravity, if the moduli are assumed to be
stabilised by some higher-scale dynamics and at the expense of some
fine-tuning. We discuss specific scenarios for stabilising the moduli via
either D- or F-terms in the effective potential, and survey possible
inflationary models in the presence of D-term stabilisation.Comment: 15 pages, 6 figures, plain Late
Total 4He Photoabsorption Cross Section Revisited: Correlated HH versus Effective Interaction HH
Two conceptually different hyperspherical harmonics expansions are used for
the calculation of the total 4He photoabsorption cross section. Besides the
well known method of CHH the recently introduced effective interaction approach
for the hyperspherical formalism is applied. Semi-realistic NN potentials are
employed and final state interaction is fully taken into account via the
Lorentz integral transform method. The results show that the effective
interaction leads to a very good convergence, while the correlation method
exhibits a less rapid convergence in the giant dipole resonance region. The
rather strong discrepancy with the experimental photodisintegration cross
sections is confirmed by the present calculations.Comment: LaTeX, 7 pages, 3 ps figure
Liquid-Phase Exfoliation of Graphite into Single- and Few-Layer Graphene with α-Functionalized Alkanes.
Graphene has unique physical and chemical properties, making it appealing for a number of applications in optoelectronics, sensing, photonics, composites, and smart coatings, just to cite a few. These require the development of production processes that are inexpensive and up-scalable. These criteria are met in liquid-phase exfoliation (LPE), a technique that can be enhanced when specific organic molecules are used. Here we report the exfoliation of graphite in N-methyl-2-pyrrolidinone, in the presence of heneicosane linear alkanes terminated with different head groups. These molecules act as stabilizing agents during exfoliation. The efficiency of the exfoliation in terms of the concentration of exfoliated single- and few-layer graphene flakes depends on the functional head group determining the strength of the molecular dimerization through dipole-dipole interactions. A thermodynamic analysis is carried out to interpret the impact of the termination group of the alkyl chain on the exfoliation yield. This combines molecular dynamics and molecular mechanics to rationalize the role of functionalized alkanes in the dispersion and stabilization process, which is ultimately attributed to a synergistic effect of the interactions between the molecules, graphene, and the solvent.We acknowledge funding from the European Commission through the Graphene Flagship, the FET project UPGRADE (GA-309056), the Agence Nationale de la Recherche through the LabEx project Nanostructures in Interaction with their Environment (ANR-11-LABX-0058_NIE), the International Center for Frontier Research in Chemistry (icFRC), the Belgian National Fund for Scientific Research (FNRS-FRFC), the ERC synergy grant Hetero2D, ERC PoC HiGRAPHINK, and the Engineering and Physical Sciences Research Council grants EP/K01711X/1, EP/K017144/1, and EP/L016087/1.This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/acs.jpclett.6b0126
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