Hadron production via<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:math>collisions with initial state radiation

Druzhinin, V. P.; Eidelman, S.; Serednyakov, S. I.; Solodov, E. P.

doi:10.1103/revmodphys.83.1545

Cited by 89 publications

(70 citation statements)

References 173 publications

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“…[18] and the compilation of e + e − induced cross sections in Refs. [25,26] the most promising case is certainly the π + π − π 0 channel, see Table I. In fact, the available data [27,28] could hint at an anomaly around theN N threshold.…”

Section: Then N → 5π 6π Reactionsmentioning

confidence: 99%

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Origin of the structures observed ine+e−annihilation into multipion states around thep¯pthreshold

et al. 2015

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We analyze the origin of the structures observed in the reactions e + e − → 3(π + π − ), 2(π + π − π 0 ), ωπ + π − π 0 , and e + e − → 2(π + π − )π 0 around the antiproton-proton (pp) threshold. We calculate the contribution of the two-step process e + e − →N N → multipions to the total reaction amplitude. The amplitude for e + e − →N N is constrained from near-threshold data on the e + e − →pp cross section and the one forN N → multipions can be likewise fixed from available experimental information, for all those 5π and 6π states. The resulting amplitude for e + e − → multipions turns out to be large enough to play a role for the considered e + e − annihilation channels and, in three of the four reactions, even allows us to reproduce the data quantitatively near theN N threshold. The structures seen in the experiments emerges then as a threshold effect due to the opening of theN N channel.

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Section: Then N → 5π 6π Reactionsmentioning

confidence: 99%

“…In three of the four reactions investigated those interference effects are indeed sufficient to explain the behavior of the measured cross sections in the region around theN N threshold. [18] and e + e − annihilation cross sections around theN N threshold [25,26].…”

Section: Then N → 5π 6π Reactionsmentioning

confidence: 99%

Origin of the structures observed ine+e−annihilation into multipion states around thep¯pthreshold

et al. 2015

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“…Interested readers may also consult reviews in Refs. [40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,39].…”

Section: General Status Of Hadron Spectroscopymentioning

confidence: 99%

The hidden-charm pentaquark and tetraquark states

et al. 2016

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In the past decade many charmonium-like states were observed experimentally. Especially those charged charmoniumlike Z c states and bottomonium-like Z b states can not be accommodated within the naive quark model. These charged Z c states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states.

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“…• The use of 'Initial State Radiation' (ISR) data [25][26][27] which has opened a new way to precisely obtain the electron-positron annihilation cross sections into hadrons at particle factories operating at fixed beamenergies [28,29].…”

Section: Recent Results and Expected Improvement On The Hadronic Contmentioning

confidence: 99%

Measuringa_μ^HLOwith space-like data

Venanzoni

2015

EPJ Web of Conferences

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Abstract. After reviewing the traditional way of computing the leading order hadronic correction to the muon (g-2) through a dispersive approach via time-like data, I will present a novel approach, based on the measurement of the effective electromagnetic coupling in the space-like region extracted from Bhabha scattering data. We argue that this new method may become feasible at flavor factories, resulting in an alternative determination potentially competitive with the accuracy of the present results obtained with the dispersive approach via time-like data 1 α em running and the Vacuum Polarization Precision physics requires appropriate inclusion of higher order effects and the knowledge of very precise parameters of the electroweak Standard Model SM. One of the basic input parameters is the fine structure constant which depends logarithmically on the energy scale [1]. At zero momentum transfer, the QED coupling constant α(0) is very accurately known from the measurement of the anomalous magnetic moment of the electron and from solid-state physics measurements:(1)Vacuum polarization effects lead to a partial screening of the charge in the low energy limit (Thomson limit) while at higher energies the strength of the electromagnetic interaction grows. This is due to virtual lepton and quark loop corrections to the photon propagator. This effect can also be understood as an increasing penetration of the polarized cloud of virtual particles which screen the bare electric charge of a particle. Thus, at large distances, we observe a reduced bare charge due to this effect of screening. As we probe closer we penetrate into the cloud of virtual particles, decreasing the screening effect and observing more of the bare charge and thus a strengthening of the coupling The charge has to be replaced by a running charge: e 2 → e 2 (q 2 ) = e 2 Z 1 + Π γ (q 2 ) .The wave function renormalization factor Z is fixed by the condition that for q 2 → 0 one obtains the classical charge (charge renormalization in the Thomson limit) [2]. Thus the renormalized charge is: a e-mail: graziano.venanzoni@lnf.infn.it e 2 → e 2 (q 2 ) = e 2 1 + (Π γ (q 2 ) − Π γ (0)) (2) where, in the perturbation theory, the lowest order diagram which contributes to Π γ (q 2 ) is: which describes virtual creation and reabsorption of fermion pairs:in leading order. In terms of the fine structure constant α = e 2 /4π:The shift Δα is large due to the large change in scale going from zero momentum to the Z-mass scale μ = M Z and due to the many species of fermions contributing. Zero momentum more precisely means the light fermion mass thresholds [1]. The various contributions to the shift in the fine structure constant come from the leptons (lep=e,μ and τ) the 5 light quarks (u,b,s,c and the corresponding hadrons =had) and from the top quark:While the leptonic contributions are calculable with very high precision in QED by the perturbation theory, the hadronic ones are more problematic as they involve the quark masses and hadronic physics at low momentum scales. B...

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Hadron production viae+e−collisions with initial state radiation

Cited by 89 publications

References 173 publications

Origin of the structures observed ine+e−annihilation into multipion states around thep¯pthreshold

Origin of the structures observed ine+e−annihilation into multipion states around thep¯pthreshold

The hidden-charm pentaquark and tetraquark states

Measuringa_μ^HLOwith space-like data

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Hadron production viae+e−collisions with initial state radiation

Cited by 89 publications

References 173 publications

Origin of the structures observed ine+e−annihilation into multipion states around thep¯pthreshold

Origin of the structures observed ine+e−annihilation into multipion states around thep¯pthreshold

The hidden-charm pentaquark and tetraquark states

MeasuringaμHLOwith space-like data

Contact Info

Product

Resources

About

Measuringa_μ^HLOwith space-like data