Egle Tomasi-Gustafsson 1 Peculiar Features of Electromagnetic Proton Form Factors Varenna, 15-VI Egle Tomasi-Gustafsson CEA, IRFU,SPhN, Saclay, France In collaboration with A. Bianconi (Univ. di Brescia) and Wang Ying(IPN Orsay) 4th INTERNATIONAL CONFERENCE ON NUCLEAR REACTION MECHANISMS Varenna (Italy), Villa Monastero June , 2015

Egle Tomasi-Gustafsson 2 _ _ q 2 <0 e-e- e-e- pp q 2 >0 e-e- e+e+ p p q2q2 q 2 =4m p 2 Time-Like FFs are complex Space-like FFs are real GE=GM G E (0)=1 G M (0)=  p Asymptotics - QCD - analyticity p+p ↔ e + +e - e+p  e+p Unphysical region p+p ↔ e + e - +   0 Proton Charge and Magnetic Distributions Varenna, 15-VI- 2015

Egle Tomasi-Gustafsson 3 Varenna, 15-VI GE=GM p+p ↔ e + +e - e+p  e+p _ _ q 2 <0 e-e- e-e- pp q 2 >0 e-e- e+e+ p p q2q2 q 2 =4m p 2 Time-Like FFs are complex Space-like FFs are real Unphysical region GE(0)=1 GM(0)=  p Asymptotics - QCD - analyticity p+p ↔ e + +e - +   Hadron Electromagnetic Form Factors GE=GM GE unpolarized GM GE Polarized

Egle Tomasi-Gustafsson 4 Varenna, 15-VI GE=GM e+p  e+p Hadron Electromagnetic Form Factors GE=GM GE unpolarized GM GE Polarized

A.I. Akhiezer and M.P. Rekalo, 1967 Jlab-GEp collaboration 1)"standard" dipole function for the nucleon magnetic FFs GMp and GMn 2) linear deviation from the dipole function for the electric proton FF Gep 3) QCD scaling not reached 3) Zero crossing of Gep? 4) contradiction between polarized and unpolarized measurements Egle Tomasi-Gustafsson Varenna, 15-VI A.J.R. Puckett et al, PRL (2010), PRC (2012) Polarization Experiments

Time-like observables: | G E | 2 and | G M | 2. Egle Tomasi-Gustafsson Varenna, 15-VI As in SL region: - Dependence on q 2 contained in FFs - Even dependence on cos 2  (1  exchange) - No dependence on sign of FFs - Enhancement of magnetic term but TL form factors are complex! A. Zichichi, S. M. Berman, N. Cabibbo, R. Gatto, Il Nuovo Cimento XXIV, 170 (1962) B. Bilenkii, C. Giunti, V. Wataghin, Z. Phys. C 59, 475 (1993). G. Gakh, E.T-G., Nucl. Phys. A761,120 (2005).

Time-like observables: | G E | 2 and | G M | 2 Egle Tomasi-Gustafsson 7 A. Zichichi, S. M. Berman, N. Cabibbo, R. Gatto, Il Nuovo Cimento XXIV, 170 (1962) B. Bilenkii, C. Giunti, V. Wataghin, Z. Phys. C 59, 475 (1993). G. Gakh, E.T-G., Nucl. Phys. A761,120 (2005). IHEP Varenna, 15-VI- 2015

Egle Tomasi-Gustafsson 8 VMD: Iachello, Jakson and Landé (1973) Isoscalar and isovector FFs ** ,ρ,,ρ, Varenna, 15-VI- 2015

The Experimental Status No individual determination of GE and GM TL proton FFs twice larger than in SL at the same Q 2 Steep behaviour at threshold Babar:Structures? Resonances? Egle Tomasi-Gustafsson 9 The Time-like Region GE=GM Panda contribution: M.P. Rekalo, E.T-G, DAPNIA-04-01, ArXiv: S. Pacetti, R. Baldini-Ferroli, E.T-G, Physics Reports, 514 (2014) 1 Varenna, 15-VI- 2015

Egle Tomasi-Gustafsson 10 The Time-like Region Expected QCD scaling (q 2 ) 2 Varenna, 15-VI GE=GM

Egle Tomasi-Gustafsson 11 Oscillations : regular pattern in P Lab A: Small perturbation B: damping C: r < 1fm D=0: maximum at p=0 Varenna, 15-VI The relevant variable is p Lab associated to the relative motion of the final hadrons. Simple oscillatory behaviour Small number of coherent sources A.Bianconi, E. T-G. Phys. Rev. Lett. 114, (2015)

The nucleon Egle Tomasi-Gustafsson Varenna, 15-VI antisymmetric state of colored quarks 3 valence quarks and a neutral sea of qq pairs Does not hold in the spatial center of the nucleon: the center of the nucleon is electrically neutral, due to strong gluonic field Main assumption E.A. Kuraev, E. T-G, A. Dbeyssi, Phys.Lett. B712 (2012) 240

The annihilation channel : Egle Tomasi-Gustafsson Varenna, 15-VI The neutral plasma acts on the distribution of the electric charge (not magnetic). Prediction: additional suppression due to the neutral plasma similar behavior in SL and TL regions Implicit normalization at q 2 =4M p 2 : |GE|=|GM| =1 No poles in unphysical region

space-time distribution of the electric charge in the space-time volume Model: generalized form factors Egle Tomasi-Gustafsson Varenna, 15-VI Definition: In SL- Breit frame (zero energy transfer): In TL-(CMS): : time evolution of the charge distribution in the domain

Egle Tomasi-Gustafsson 15 Fourier Transform Rescattering processes Large imaginary part Related to the time evolution of the charge density? Consequences for the SL region? Data expected at BESIII, PANDA (E.A. Kuraev, E. T.-G., A. Dbeyssi, PLB712 (2012) 240) Varenna, 15-VI F 0 = =

A. Bianconi, E. Tomasi-Gustafsson 16 Conclusions Recent and precise data on the proton time-like form factors measured by the BABAR collaboration show a systematic sinusoidal modulation in the near-threshold region. The relevant variable is the momentum p associated to the relative motion of the final hadrons. The periodicity and the simple shape of the oscillations point to a unique interference mechanism, which occurs when the hadrons are separated by about 1 fm. At some stage of the hadronic matter, is distributed in a non-trivial way: the formation evolves along alternative interfering channels. The oscillation period corresponds to hadronic-scale  scaling-violating parameter  origin ?

A. Bianconi, E. Tomasi-Gustafsson 17

Egle Tomasi-Gustafsson Varenna, 15-VI The long range color forces create a stable colorless state of proton and antiproton The initial energy is dissipated from current to constituent quarks originating on shell separated by R. The annihilation channel : The repulsion of p and p with kinetic energy is balanced by the confinement potential

The nucleon Egle Tomasi-Gustafsson Varenna, 15-VI In the internal region of strong chromo-magnetic field, the color quantum number of quarks does not play any role, due to stochastic averaging Intensity of the gluon field in vacuum: Inner region: gluonic condensate of clusters with randomly oriented chromo-magnetic field (Vainshtein, 1982): didjdidj proton neutron Colorless quarks: Pauli principle

Model Egle Tomasi-Gustafsson Varenna, 15-VI ) uu (dd) quarks are repulsed from the inner region 2) The 3 rd quark is attracted by one of the identical quarks, forming a compact di-quark 3) The color state is restored Formation of di-quark: competition between attraction force and stochastic force of the gluon field Antisymmetric state of colored quarks Colorless quarks: Pauli principle attraction force >stochastic force of the gluon field proton: (u) Qq=-1/3 neutron: (d) Qq=2/3

Egle Tomasi-Gustafsson Varenna, 15-VI Proton: r 0 =0.22 fm, p 0 2 = 1.21 GeV 2 Neutron: r 0 =0.31 fm, p 0 2 = 2.43 GeV 2 Model attraction force > stochastic force of the gluon field Applies to the scalar part of the potential

Egle Tomasi-Gustafsson Varenna, 15-VI Quark counting rules apply to the vector part of the potential Model

Egle Tomasi-Gustafsson Varenna, 15-VI Additional suppression for the scalar part due to colorless internal region: “charge screening in a plasma”: Additional suppression (Fourier transform) fitting parameter Model Neutrality condition: Boltzmann constant

2) The vacuum state transfers all the released energy to a state of matter consisting of: 6 massless valence quarks Set of gluons Sea of current qq pairs of quarks with energy q 0 >2M p, J=1, dimensions The annihilation channel: Egle Tomasi-Gustafsson Varenna, 15-VI ) Pair of p and p formed by three bare quarks: Structureless Colorless pointlike FFs !!! 1) Creation of a pp state through intermediate state with

The annihilation channel : Egle Tomasi-Gustafsson Varenna, 15-VI The point-like hadron pair expands and cools down: the current quarks and antiquarks absorb gluon and transform into constituent quarks The residual energy turns into kinetic energy of the motion with relative velocity The strong chromo-EM field leads to an effective loss of color. Fermi statistics: identical quarks are repulsed. The remaining quark of different flavor is attracted to one of the identical quarks, creating a compact diquark (du-state)

At larger distances, the inertial force exceeds the confinement force: p and p start to move apart with relative velocity  The annihilation channel : Egle Tomasi-Gustafsson Varenna, 15-VI For very small values of the velocity FSI lead to the creation of a bound NN system. p and p leave the interaction region: at large distances the integral of Q(t) must vanish.

Egle Tomasi-Gustafsson Varenna, 15-VI Point-like form factors? S. Pacetti

Egle Tomasi-Gustafsson 28 Varenna, 15-VI e + +e -  p + p +  B. Aubert ( BABAR Collaboration) Phys Rev. D73, (2006) Radiative return (ISR)