35,166 research outputs found

    Singlet Charge 2/32/3 Quark hiding the Top: Tevatron and LEP Implications

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    If cc and tt quarks are strongly mixed with a weak singlet charge 2/32/3 quark, BR(t→ℓν+X)BR(t\to \ell\nu + X) could be suppressed via the t→cH0t\to cH^0 mode, thereby the top quark could still hide below MWM_W, whereas the heavy quark signal observed at the Tevatron is due to the dominantly singlet quark QQ. This may occur without affecting the small mcm_c value. Demanding mQ≃175m_Q \simeq 175 GeV and m_t \ltap M_W, we find that BR(t→ℓν+X)BR(t\to \ell\nu + X) cannot be too suppressed. The heavy quark QQ decays via W, HW,\ H, and ZZ bosons. The latter can lead to bb-tagged Z+4Z + 4 jet events, while the strong cc--QQ mixing is reflected in sizable Q→sWQ\to sW fraction. Z→tcˉZ\to t\bar c decay occurs at tree level and may be at the 10−310^{-3} order, leading to the signature of Z→ℓνbcˉZ\to \ell\nu b\bar c, all isolated and with large pTp_T, at 10−510^{-5} order.Comment: 10 pages + 3 Figures (not included), ReVTeX, NTUTH-94-1

    Eigenvalues of Ruijsenaars-Schneider models associated with An−1A_{n-1} root system in Bethe ansatz formalism

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    Ruijsenaars-Schneider models associated with An−1A_{n-1} root system with a discrete coupling constant are studied. The eigenvalues of the Hamiltonian are givein in terms of the Bethe ansatz formulas. Taking the "non-relativistic" limit, we obtain the spectrum of the corresponding Calogero-Moser systems in the third formulas of Felder et al [20].Comment: Latex file, 25 page

    Anyonic interferometry without anyons: How a flux qubit can read out a topological qubit

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    Proposals to measure non-Abelian anyons in a superconductor by quantum interference of vortices suffer from the predominantly classical dynamics of the normal core of an Abrikosov vortex. We show how to avoid this obstruction using coreless Josephson vortices, for which the quantum dynamics has been demonstrated experimentally. The interferometer is a flux qubit in a Josephson junction circuit, which can nondestructively read out a topological qubit stored in a pair of anyons --- even though the Josephson vortices themselves are not anyons. The flux qubit does not couple to intra-vortex excitations, thereby removing the dominant restriction on the operating temperature of anyonic interferometry in superconductors.Comment: 7 pages, 3 figures; Added an Appendix on parity-protected single-qubit rotations; problem with Figure 3 correcte

    A semismooth newton method for the nearest Euclidean distance matrix problem

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    The Nearest Euclidean distance matrix problem (NEDM) is a fundamentalcomputational problem in applications such asmultidimensional scaling and molecularconformation from nuclear magnetic resonance data in computational chemistry.Especially in the latter application, the problem is often large scale with the number ofatoms ranging from a few hundreds to a few thousands.In this paper, we introduce asemismooth Newton method that solves the dual problem of (NEDM). We prove that themethod is quadratically convergent.We then present an application of the Newton method to NEDM with HH-weights.We demonstrate the superior performance of the Newton method over existing methodsincluding the latest quadratic semi-definite programming solver.This research also opens a new avenue towards efficient solution methods for the molecularembedding problem

    Grazing activity increases decomposition of yak dung and litter in an alpine meadow on the Qinghai-Tibet plateau

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