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German Rodrigo

Publications and source records attributed to German Rodrigo.

At least 91 records · Page 5Linked to original sources
arXiv2003

Ritorno radiativo per la misura di R: come e perche

The measurement of the pion form factor and, more generally, of the cross section for electron--positron annihilation into hadrons through the radiative return has become an important task for high luminosity colliders such as the $Φ$- or $B$-meson factories. This quantity is crucial for predictions of the hadronic contributions to $(g-2)_μ$, the anomalous magnetic moment of the muon, and to the running of the electromagnetic coupling. But the radiative return opens also the possibility of many other physical applications. The physics potential of this method at high luminosity meson factories is discussed and recent results are reviewed.

hep-ph↗
arXiv2003

Resummed jet rates for $e^+e^-$ annihilation into massive quarks

Expressions for Sudakov form factors for heavy quarks are presented. They are used to construct resummed jet rates for up to four jets in $e^+e^-$ annihilation. The coefficients of leading and next-to-leading logarithmic corrections, mandatory for a combination with higher order matrix elements, are evaluated up to second order in $α_s$.

hep-ph↗
arXiv2002

Precision measurement of the hadronic cross-section through the radiative return method

Electron--positron annihilation into hadrons plus an energetic photon from initial-state radiation allows the hadronic cross-section to be measured over a wide range of energies at high luminosity meson factories. Weighted integrals over this cross-section are a decisive input for electroweak precision tests. A Monte Carlo event generator called PHOKHARA has been developed, which simulates $e^+ e^- \to$ hadrons + photon(s) at the NLO accuracy. The latest tests and upgrades are presented in this paper.

hep-ph↗
arXiv2002

Radiative Return at NLO: the PHOKHARA Monte Carlo generator

Electron--positron annihilation into hadrons plus an energetic photon from initial state radiation allows the hadronic cross-section to be measured over a wide range of energies at high luminosity meson factories. A Monte Carlo generator called PHOKHARA has been constructed, which simulates this process at the next-to-leading order accuracy.

hep-ph↗
arXiv2002

The radiative return at small angles: virtual corrections

Virtual corrections for electron--positron annihilation into one real and one off-shell photon of invariant mass Q^2 are evaluated. Special attention is paid to those configurations where the real photon is collinear with the beam direction. This calculation is an important ingredient of a Monte Carlo program, which simulates events with tagged photons from initial-state radiation, including NLO corrections.

hep-ph↗
arXiv2001

Radiative return at NLO and the measurement of the hadronic cross-section

The measurement of the hadronic cross-section in $e^+ e^-$ annihilation at high luminosity factories using the radiative return method is motivated and discussed. A Monte Carlo generator which simulates the radiative process $e^+ e^- \to γ+hadrons$ at the next-to-leading order accuracy is presented. The analysis is then extended to the description of events with hard photons radiated at very small angle.

hep-ph↗
arXiv2001

NLO QED corrections to ISR in e+ e- annihilation and the measurement of σ(e+ e- \to hadrons) using tagged photons

The leptonic tensor for the process $e^+ e^- \to γ+γ^*$, which describes the next-to-leading order virtual and soft QED corrections to initial state radiation in $e^+ e^-$ annihilation with emission of an extra virtual photon decaying into hadrons, is calculated. A Monte Carlo generator for the reaction $e^+ e^- \to γ+ π^+ π^-$ has been set up which includes these corrections. It thus describes configurations where the invariant mass of the hadrons plus photon is very close to $\sqrt{s}$. Predictions for cms energies of 1 to 10 GeV, corresponding to the energies of DAPHNE and B-meson factories, are presented. The possibility for an accurate measurement using tagged photons of $σ(e^+ e^- \to hadrons)$, which plays an important role in the theoretical description of the muon anomalous magnetic moment and the running of the electromagnetic coupling, is discussed.

hep-ph↗
arXiv2000

QCD factorization with heavy quarks

We further analyze the definition and the calculation of the heavy quark impact factor at next-to-leading (NL) $\log s$ level, and we provide its analytical expression in a previously proposed k-factorization scheme. Our results indicate that k-factorization holds at NL level with a properly chosen energy scale, and with the same gluonic Green's function previously found in the massless probe case.

hep-ph↗
arXiv2000

Heavy Quark Impact Factor at Next-to-leading Level

We further analyze the definition and the calculation of the heavy quark impact factor at next-to-leading (NL) log(s) level, and we provide its analytical expression in a previously proposed k-factorization scheme. Our results indicate that k-factorization holds at NL level with a properly chosen energy scale, and with the same gluonic Green's function previously found in the massless probe case.

hep-ph↗
arXiv1999

$m_b(m_Z)$ from jet production at the $Z$ peak in the Cambridge algorithm

We consider the production of heavy quark jets at the $Z$-pole at the next-to-leading order (NLO) using the {\it Cambridge jet-algorithm}. We study the effects of the quark mass in two- and three-jet observables and the uncertainty due to unknown higher order corrections as well as due to fragmentation. We found that the three-jet observable has remarkably small NLO corrections, which are stable with respect to the change of the renormalization scale, when expressed in terms of the {\it running quark mass} at the $m_Z$-scale. The size of the hadronization uncertainty for this observable remains reasonably small and is very stable with respect to changes in the jet resolution parameter $y_c$.

hep-ph↗
arXiv1999

Quark-mass effects for jet production in e^+ e^- collisions at the next-to-leading order: results and applications

We present a detailed description of our calculation of next-to-leading order QCD corrections to heavy quark production in e^+ e^- collisions including mass effects. In particular, we study the observables $R_3^{b\ql}$ and $D_2^{b\ql}$ in the E, EM, JADE and DURHAM jet-clustering algorithms and show how one can use these observables to obtain $m_b(m_Z)$ from data at the $Z$ peak.

hep-ph↗
arXiv1999

Improved Determination of the b-Quark Mass at the Z Peak

Next-to-leading order calculations of heavy quark three-jet production in e^+ e^- annihilation are reviewed. Their application for the measurement of the b-quark mass at LEP/SLC and to the test of the flavour independence of the strong coupling constant are discussed. Prospects for future improvements are studied.

hep-ph↗
arXiv1998

Do quark masses run?

The importance of measuring the b-quark mass at different scales is emphasized. The recent next-to-leading order calculation of three jet heavy quark production at LEP and its use to measure $m_b(m_Z)$ is discussed.

hep-ph↗
arXiv1997

The running of the b-quark mass from LEP data

Next-to-leading order QCD corrections to three jet heavy quark production in $e^+ e^-$ collisions, including quark mass effects, are presented. The extraction of the b-quark mass form LEP data is considered and the first experimental evidence for the running of a quark mass is discussed.

hep-ph↗