Prospects for e+e- physics at Frascati between the φ and the ψ

Ambrosino, F.; Anulli, F.; Babusci, D.; Bianco, S.; Bini, C.; Brambilla, Nora; Sangro, R. de; Gauzzi, P.; Gensini, Paolo M.; Giovannella, S.; Muccifora, V.; Negrini, M.; Nguyen, F.; Pacetti, S.; Pancheri, G.; Passera, M.; Passeri, A.; Polosa, A. D.; Radici, Marco; Srivastava, Y. N.; Vairo, Antonio; Venanzoni, G.; Violini, G.

doi:10.1140/epjc/s10052-007-0271-1

Cited by 20 publications

(15 citation statements)

References 301 publications

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“…In spite of the fact that the discussion presented here is not really new, the substantial amount of new data in the low energy region from KLOE, SND and CMD-2 and from BABAR leads to a noticeable change of the error profile of α eff (E) at different scales and it provides a strong motivation for the upcoming VEPP-2000 [17] and future DANAE/KLOE-2 [18] projects to continue precise measurements of σ hadronic in the region from threshold up to 2.5 GeV.…”

Section: Introductionmentioning

confidence: 85%

Precision measurements of σhadronic for αeff(E) at ILC energies and (g−2)μ

Jegerlehner

2006

Nuclear Physics B - Proceedings Supplements

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A more precise determination of the effective fine structure constant α eff (E) is mandatory for confronting data from future precision experiments with precise SM predictions. Higher precision would help a lot in monitoring new physics by increasing the significance of any deviation from theory. At a future e + e − -collider like the ILC, as at LEP before, α eff (E) plays the role the static zero momentum α = α eff (0) plays in low energy physics. However, by going to the effective version of α one loses about a factor 2 × 10 2 at E = mµ to 10 5 at E = MZ in precision, such that for physics at the gauge boson mass scale and beyond α eff (E) is the least known basic parameter, about a factor 20 less precise than the neutral gauge boson mass MZ and by about a factor 60 less precise than the Fermi constant GF . Examples of precision limitations are α eff (mµ) which limits the theoretical precision of the muon anomalous magnetic moment aµ and α eff (MZ) which limits the accuracy of the prediction of the weak mixing parameter sin 2 Θ f and indirectly the upper bound on the Higgs mass mH. An optimal exploitation of a future linear collider for precision physics requires an improvement of the precision of α eff (E) by something like a factor ten. We discuss a strategy which should be able to reach this goal by appropriate efforts in performing dedicated measurements of σ hadronic in a wide energy range as well as efforts in theory and in particular improving the precision of the QCD parameters αs, mc and m b by lattice QCD and/or more precise determinations of them by experiments and perturbative QCD efforts. Projects at VEPP-2000 (Novosibirsk) and DANAE/KLOE-2 (Frascati) are particularly important for improving on α eff (MZ) as well as α eff (mµ). Using the Adler function as a monitor, one observes that we may obtain the hadronic shift ∆αpQCD where the first term includes the full non-perturbative part with the choice s0 = (2.5 GeV) 2 or larger. In such a determination low-energy machines play a particularly important role in the improvement program. We present an up-to-date analysis including the recent data from KLOE, SND, CMD-2 and BABAR. The analysis based on e + e − -data yields ∆α

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Section: Introductionmentioning

confidence: 85%

Precision measurements of σhadronic for αeff(E) at ILC energies and (g−2)μ

Jegerlehner

2006

Nuclear Physics B - Proceedings Supplements

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“…We recall that the integrated cross section for e + e − → pp in the considered region is approximately 1 nb; hence, at the foreseen luminosity of 10 32 cm −2 s −1 for DAFNE-2 [13,14] this sample can be collected in one month with efficiency 1. The lower q 2 bin does not include the pp threshold, because this region is characterized by peculiar mechanisms like, e.g., the Coulomb focussing and possible subthreshold resonances.…”

Section: General Features Of the Numerical Simulationsmentioning

confidence: 99%

“…[15], we analyzed in detail the conditions for an unpolarized e + e − → pp measurement at DAFNE-2 [13,14] in order to estimate the achievable precision in the reconstruction of r e = |G E /G M | and in a possible detection of 2γ contributions. As it has been recalled in Sec.…”

Section: Reconstruction Of the Spin Asymmetrymentioning

confidence: 99%

“…energy range from the φ mass to 2.5 GeV while keeping a luminosity of 10 32 cm −2 s −1 , and, in particular, by inserting a polarimeter around the interaction region [14], would allow to explore the production of polarized pp, nn, ΛΛ, and ΣΣ pairs with great precision. As for protons, in a previous paper [15] we explored the conditions under which the ratio |G E /G M | could be extracted at DAFNE-2 from the angular distribution of the unpolarized cross section at any given q 2 .…”

Section: Introductionmentioning

confidence: 99%

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Extraction of proton form factors in the timelike region from single-polarizede+e−→p→p¯events

2006

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We have performed numerical simulations of the single-polarized e + e − → pp process in kinematic conditions under discussion for a possible upgrade of the existing DAFNE facility. By fitting the cross section and spin asymmetry angular distributions with typical Born expressions, we can study the conditions for extracting information on moduli and phases of the proton electromagnetic form factors in the timelike region, which are poorly known and whose preliminary data show puzzling features. We have explored also non-Born contributions by introducing a further component in the angular fit, which is related to two-photon exchange diagrams.Using a dipole parametrization, we show that these corrections can be identified if larger than 5% of the Born contribution; we also explore the conditions for extracting information on the phase and, consequently, on the relative weight between their real and imaginary parts, which are presently unknown.

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“…Such measurements would be crucial for the muon g − 2 as well as for a more precise determination of the running fine structure constant α QED (E). In particular, e + e − low energy cross section measurements in the region between 1 and 2.5 GeV [93,94] are able to substantially improve the accuracy of a had(1) µ and α QED (M Z ) [63].…”

Section: Prospectsmentioning

confidence: 99%

The Muon g—: Status and Perspectives

Jegerlehner

Precision Physics of Simple Atoms and Molecules

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The muon anomalous magnetic moment is one of the most precisely measured quantities in particle physics. Recent high precision measurements (0.5ppm) at Brookhaven reveal a "discrepancy" by 3 standard deviations from the electroweak Standard Model which could be a hint for an unknown contribution from physics beyond the Standard Model. This triggered numerous speculations about the possible origin of the "missing piece". The remarkable 15-fold improvement of the previous CERN experiment, actually animated a multitude of new theoretical efforts which lead to a substantial improvement of the prediction of a µ . The dominating uncertainty of the prediction, caused by strong interaction effects, could be reduced substantially, due to new hadronic cross section measurements in electron-positron annihilation at low energies. After an introduction and a brief description of the principle of the experiment, I review the status of the theoretical prediction and discuss the role of the hadronic vacuum polarization effects and the hadronic light-by-light scattering contribution. Prospects for the future will be briefly discussed. As, in electroweak precision physics, the muon g − 2 shows the largest established deviation between theory and experiment at present, it will remain one of the hot topics also in future. Lepton magnetic momentsThe subject of our interest is the motion of a lepton in an external electromagnetic field under consideration of the full relativistic quantum behavior. The latter is controlled by the equations of motion of Quantum electrodynamics (QED), which describes the interaction of charged leptons ( = e, µ, τ ) with the photon (γ) as an Abelian U (1) em gauge theory. QED is a quantum field theory (QFT) which emerges as a synthesis of quantum mechanics with special relativity. In our case an external electromagnetic field is added, specifically a constant homogeneous magnetic field B. For slowly varying fields the motion is essentially determined by the generalized Pauli equation, which also serves

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Prospects for e+e- physics at Frascati between the φ and the ψ

Cited by 20 publications

References 301 publications

Precision measurements of σhadronic for αeff(E) at ILC energies and (g−2)μ

Precision measurements of σhadronic for αeff(E) at ILC energies and (g−2)μ

Extraction of proton form factors in the timelike region from single-polarizede+e−→p→p¯events

The Muon g—: Status and Perspectives

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