Search results for "Corrections"
showing 10 items of 65 documents
Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2016
2017
This article reports world averages of measurements of $b$-hadron, $c$-hadron, and $\tau$-lepton properties obtained by the Heavy Flavor Averaging Group using results available through summer 2016. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, \CP~violation parameters, parameters of semileptonic decays and CKM matrix elements.
Quantum corrections to inflation: the importance of RG-running and choosing the optimal RG-scale
2017
We demonstrate the importance of correctly implementing RG running and choosing the RG scale when calculating quantum corrections to inflaton dynamics. We show that such corrections are negligible for single-field inflation, in the sense of not altering the viable region in the ${n}_{s}\ensuremath{-}r$ plane, when imposing Planck constraints on ${A}_{s}$. Surprisingly, this also applies, in a nontrivial way, for an inflaton coupled to additional spectator degrees of freedom. The result relies on choosing the renormalization scale (pseudo-)optimally, thereby avoiding unphysical large logarithmic corrections to the Friedmann equations and large running of the couplings. We find that the viabl…
Next-to-leading order Balitsky-Kovchegov equation with resummation
2016
We solve the Balitsky-Kovchegov evolution equation at next-to-leading order accuracy including a resummation of large single and double transverse momentum logarithms to all orders. We numerically determine an optimal value for the constant under the large transverse momentum logarithm that enables including a maximal amount of the full NLO result in the resummation. When this value is used the contribution from the $\alpha_s^2$ terms without large logarithms is found to be small at large saturation scales and at small dipoles. Close to initial conditions relevant for phenomenological applications these fixed order corrections are shown to be numerically important.
Precision measurement of the mass of the tau lepton
2014
An energy scan near the $\tau$ pair production threshold has been performed using the BESIII detector. About $24$ pb$^{-1}$ of data, distributed over four scan points, was collected. This analysis is based on $\tau$ pair decays to $ee$, $e\mu$, $eh$, $\mu\mu$, $\mu h$, $hh$, $e\rho$, $\mu\rho$ and $\pi\rho$ final states, where $h$ denotes a charged $\pi$ or $K$. The mass of the $\tau$ lepton is measured from a maximum likelihood fit to the $\tau$ pair production cross section data to be $m_{\tau} = (1776.91\pm0.12 ^{+0.10}_{-0.13}$) MeV/$c^2$, which is currently the most precise value in a single measurement.
A Theoretical Prediction of the Bs-Meson Lifetime Difference
2000
We present the results of a quenched lattice calculation of the operator matrix elements relevant for predicting the Bs width difference. Our main result is (\Delta\Gamma_Bs/\Gamma_Bs)= (4.7 +/- 1.5 +/- 1.6) 10^(-2), obtained from the ratio of matrix elements, R(m_b)=/=-0.93(3)^(+0.00)_(-0.01). R(m_b) was evaluated from the two relevant B-parameters, B_S^{MSbar}(m_b)=0.86(2)^(+0.02)_(-0.03) and B_Bs^{MSbar}(m_b) = 0.91(3)^(+0.00)_(-0.06), which we computed in our simulation.
A minimal model for ${\rm SU}(N)$ vector dark matter
2015
We study an extension of the Standard Model featuring a hidden sector that consists of a new scalar charged under a new SU$(N)_D$ gauge group, singlet under all Standard Model gauge interactions, and coupled with the Standard Model only via a Higgs portal. We assume that the theory is classically conformal, with electroweak symmetry breaking dynamically induced via the Coleman-Weinberg mechanism operating in the hidden sector. Due to the symmetry breaking pattern, the SU$(N)_D$ gauge group is completely Higgsed and the resulting massive vectors of the hidden sector constitute a stable dark matter candidate. We perform a thorough scan over the parameter space of the model at different values…
Measurement of K-e3(0) form factors
2004
The semi-leptonic decay of the neutral K meson $K^{0}_{L} \to \pi^{\pm}e^{\mp}\nu (K_{e3})$, was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector $(f_{+}(q^{2}))$, scalar $(f_{S})$ and tensor $(f_{T})$ interactions were measured. The linear slope of the vector form factor $\lambda_{+} = 0.0284 \pm 0.0007 \pm 0.0013$ and values for the ratios $|f_{S}/f_{+}(0)|=0.015^{+0.007}_{-0.010} \pm 0.012$ and $|f_{T}/f_{+}(0)|=0.05^{+0.03}_{-0.04} \pm 0.03$ were obtained. The values fo…
Two-parton contribution to the heavy-quark forward–backward asymmetry in NNLO QCD
2006
Forward-backward asymmetries, $A_{FB}^Q$, are important observables for the determination of the neutral-current couplings of heavy quarks in inclusive heavy quark production, $e^+ e^- \to \gamma^*, Z^* \to Q +X$. In view of the measurement perspectives on $A_{FB}^Q$ at a future linear collider, precise predictions of $A_{FB}^Q$ are required for massive quarks. We compute the contribution of the $Q \bar Q$ final state to $A_{FB}^Q$ to order $\as^2$ in the QCD coupling. We provide general formulae, and we show that this contribution to $A_{FB}^Q$ is infrared-finite. We evaluate these two-parton contributions for $b$ and $c$ quarks on and near the $Z$ resonance, and for $t$ quarks above thres…
Measurement of the transverse spin correlation in Z → τ+ τ- decays
1997
The measurement of the correlation between the transverse spin components of tau(+)tau(-) pairs collected during 1992 to 1994 with the DELPHI detector at LEP1 is presented. A value C-TT = 0.87 +/- 0.20 (stat.)(-0.12)(+0.10) (syst.) was obtained for the correlation parameter, in agreement with the Standard Model expectation. (C) 1997 Published by Elsevier Science B.V.
Search for neutral and charged Higgs bosons in $e^+ e^-$ collisions at $\sqrt{s}$= 161 GeV and 172 GeV
1998
A search for neutral and charged Higgs bosons has been performed in the data collected by the {\sc DELPHI} detector at centre-of-mass energies of 161~GeV and 172~GeV. The analysis assumes either the pair-production of charged Higgs bosons, ${\mathrm H}^{\pm}$, or the production of the lightest neutral Higgs boson, h, with either a Z or a neutral pseudoscalar Higgs boson, A. All final state topologies expected from the decay of h and A %neutral Higgs particles into hadrons or a pair of $\tau$ leptons, and from the decay of ${\mathrm H}^{\pm}$ %charged Higgs bosons into a pair of quarks or a $\tau \nu_{\tau}$ pair have been considered. %In the case of the associated production with a Z boson,…