13 research outputs found

    Shot Noise at High Temperatures

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    We consider the possibility of measuring non-equilibrium properties of the current correlation functions at high temperatures (and small bias). Through the example of the third cumulant of the current (S3{\cal{S}}_3) we demonstrate that odd order correlation functions represent non-equilibrium physics even at small external bias and high temperatures. We calculate S3=y(eV/T)e2I{\cal{S}}_3=y(eV/T) e^2 I for a quasi-one-dimensional diffusive constriction. We calculate the scaling function yy in two regimes: when the scattering processes are purely elastic and when the inelastic electron-electron scattering is strong. In both cases we find that yy interpolates between two constants. In the low (high) temperature limit yy is strongly (weakly) enhanced (suppressed) by the electron-electron scattering.Comment: 11 pages 4 fig. submitted to Phys. Rev.

    Decay constants, light quark masses and quark mass bounds from light quark pseudoscalar sum rules

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    The flavor udud and usus pseudoscalar correlators are investigated using families of finite energy sum rules (FESR's) known to be very accurately satisfied in the isovector vector channel. It is shown that the combination of constraints provided by the full set of these sum rules is sufficiently strong to allow determination of both the light quark mass combinations mu+mdm_u+m_d, ms+mum_s+m_u and the decay constants of the first excited pseudoscalar mesons in these channels. The resulting masses and decay constants are also shown to produce well-satisfied Borel transformed sum rules, thus providing non-trivial constraints on the treatment of direct instanton effects in the FESR analysis. The values of mu+mdm_u+m_d and ms+mum_s+m_u obtained are in good agreement with the values implied by recent hadronic Ď„\tau decay analyses and the ratios obtained from ChPT. New light quark mass bounds based on FESR's involving weight functions which strongly suppress spectral contributions from the excited resonance region are also presented.Comment: 28 pages, 10 figure

    Valence-quark distributions in the pion

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    We calculate the pion's valence-quark momentum-fraction probability distribution using a Dyson-Schwinger equation model. Valence-quarks with an active mass of 0.30 GeV carry 71% of the pion's momentum at a resolving scale q_0=0.54 GeV = 1/(0.37 fm). The shape of the calculated distribution is characteristic of a strongly bound system and, evolved from q_0 to q=2 GeV, it yields first, second and third moments in agreement with lattice and phenomenological estimates, and valence-quarks carrying 49% of the pion's momentum. However, pointwise there is a discrepancy between our calculated distribution and that hitherto inferred from parametrisations of extant pion-nucleon Drell-Yan data.Comment: 8 pages, 3 figures, REVTEX, aps.sty, epsfig.sty, minor corrections, version to appear in PR
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