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.

Neutrino CP violating parameters from nontrivial quark-lepton correlation: a S3xGUT model

We investigate the prediction on the lepton phases in theories with a non trivial correlation between quark (CKM) and lepton (PMNS) mixing matrices. We show that the actual evidence, under the only assumption that the correlation matrix $V^M$ product of $CKM$ and $PMNS$ has a zero in the entry $(1,3)$, gives us a prediction for the three CP-violating invariants $J$, $S_1$, and $S_2$. A better determination of the lepton mixing angles will give a strong prediction of the CP-violating invariants in the lepton sector. These will be tested in the next generation experiments. To clarify how our prediction works, we show how a model based on a Grand Unified Theory and the permutation flavor symmetry $S_3$ predicts $V^M_{13}=0$.Comment: 7 pages, 3 figures. V2: new figure adde

Fractional Laplacian in Bounded Domains

The fractional Laplacian operator, $-(-\triangle)^{\frac{\alpha}{2}}$, 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 ($S,T$) 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

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

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

Four-nucleon shell-model calculations in a Faddeev-like approach

We use equations for Faddeev amplitudes to solve the shell-model problem for four nucleons in the model space that includes up to 14 hbar Omega harmonic-oscillator excitations above the unperturbed ground state. Two- and three-body effective interactions derived from the Reid93 and Argonne V8' nucleon-nucleon potentials are used in the calculations. Binding energies, excitations energies, point-nucleon radii and electromagnetic and strangeness charge form factors for 4He are studied. The structure of the Faddeev-like equations is discussed and a formula for matrix elements of the permutation operators in a harmonic-oscillator basis is given. The dependence on harmonic-oscillator excitations allowed in the model space and on the harmonic-oscillator frequency is investigated. It is demonstrated that the use of the three-body effective interactions improves the convergence of the results.Comment: 22 pages, 13 figures, REVTe

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