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Search Results: 1 - 10 of 18553 matches for " Alberto Sirlin "
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How Strong is the Evidence for Electroweak Corrections Beyond the Running of $α$?
Alberto Sirlin
Physics , 1993, DOI: 10.1103/PhysRevLett.72.1786
Abstract: The evidence for electroweak radiative corrections not contained in $\alpha(m_Z)$ is examined. At low energies there is very strong evidence in the analysis of the unitarity of the CKM matrix. At LEP and collider experiments the current direct signals are not strong, but there is substantial indirect evidence, which will likely become sharper when $m_t$ is determined. The advantage of using $(\Delta r)_{res}$ as a measure of these effects is emphasized. In order to improve the direct evidence, more accurate measurements of $m_W$ and the on--resonance asymmetries are indicated.
Considerations Concerning the QCD Corrections to $Δρ$
Alberto Sirlin
Physics , 1994, DOI: 10.1016/0370-2693(95)00079-Z
Abstract: Using recent results of Avdeev et al. and an expansion for $\mu_t/\mms$ ($M_t$ is the pole mass and $\mu_t\equiv \hat{m_t}(\mu_t)$ ), it is shown that when deltarho is expressed in terms of $\hat{m_t}^2(M_t)$, the QCD correction is only $(2-3)\times 10^{-3}$ in the NLO approximation. As a consequence, in terms of $M_t^2$ the correction to $\dr$ is almost entirely contained in $\mmss/M_t^2$, a pure QCD effect. The latter is studied using various optimization procedures, and the results compared with the expansion proposed by Avdeev et al.. Implications for \ew physics are discussed. Threshold effects are analyzed on the basis of a simple sum rule.
Alberto Sirlin
Physics , 1995,
Abstract: The phenomenological evidence for electroweak corrections in the Standard Model, both at very low energies and the $Z^0$ scale, is discussed. In particular, we review a simple but sharp argument for the presence of Electroweak Bosonic Corrections.
On the QCD corrections to $Δρ$
Alberto Sirlin
Physics , 1994,
Abstract: We discuss some recent developments in the evaluation of the QCD corrections to $\Delta\rho$, their interpretation, an estimate of the theoretical error, and its effect on electroweak physics.
Ten Years of Precision Electroweak Physics
Alberto Sirlin
Physics , 1999,
Abstract: We review a number of theoretical developments in Precision Electroweak Physics that are closely connected with the interpretation of experiments. The emphasis is on the test of the Standard Model at the level of its quantum corrections, the search for the Higgs boson, and constraints on new physics.
Remembering a Great Teacher
Alberto Sirlin
Physics , 2015,
Abstract: The article is a recollection of the memorable experience of attending a course on Quantum Mechanics given by Feynman in Brasil, as well as several meetings and exchanges Daniele Amati and I had with him over many years, in both the U.S. and Europe. The article also includes a small sample of the problems assigned in the course, a one-page guide, hand-written by Feynman, to study QED on the basis of two of his most important papers, and his reply to a letter of congratulations that the author had sent to him on the occasion of his Nobel Prize Award.
Renormalon contributions to δρ
Paolo Gambino,Alberto Sirlin
Physics , 1995, DOI: 10.1016/0370-2693(95)00741-3
Abstract: Leading QCD vacuum polarization contributions to the electroweak parameter $\delta\rho$ are evaluated numerically using several different prescriptions for the gluon self-energy. Simple theoretical estimates of the asymptotic behavior are given. The results show a significant contribution from the leading infrared renormalons when $\delta\rho$ is expressed in terms of the top-quark pole mass and its absence when the $\msbar$ running mass is employed. The calculations are applied to estimate higher order QCD contributions to $\delta\rho$.
Application of the Pinch Technique to Neutral Current Amplitudes and the Concept of the Z Mass
Kostas Philippides,Alberto Sirlin
Physics , 1995, DOI: 10.1016/0370-2693(95)01453-5
Abstract: The pinch technique (PT) is applied to neutral current amplitudes, focusing on the mixing problem. Extending recent arguments due to Papavassiliou and Pilaftsis, it is shown that the use of the PT self-energies does not shift the complex-valued position of the pole through order {\cal O}($g^4$). This leads (to the same accuracy) to a simple interpretation of $M_Z$, the mass measured at LEP, in terms of the PT self-energies. It is pointed out that the PT approach provides a convenient and rather elegant formalism to discuss important neutral current amplitudes, such as those relevant to four-fermion processes and LEP2.
Renormalizable W Self-Energy in the Unitary Gauge via the Pinch Technique
Joannis Papavassiliou,Alberto Sirlin
Physics , 1994, DOI: 10.1103/PhysRevD.50.5951
Abstract: We use the S-matrix pinch technique to derive to one loop order an effective renormalizable self-energy for the W gauge boson, when the theory is quantized in the unitary gauge. We then show that this amplitude is identical to the $\xi$-independent W self-energy previously constructed by applying the pinch technique in the context of the renormalizable $R_{\xi}$ gauges.}
Consistency Condition for the Pinch Technique Self-Energies at Two Loops
Kostas Philippides,Alberto Sirlin
Physics , 1996, DOI: 10.1016/0550-3213(96)00300-8
Abstract: A simple and testable necessary condition for the gauge independence of the Pinch Technique self-energies at two loops is discussed. It is then shown that, in the case of the $Z$ and $W$ self-energies, the condition is indeed satisfied by the Papavassiliou-Pilaftsis formulation.
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