Measurement of time-like nucleon form factors at Frascati

1. Measurement of time-like nucleon form factors at Frascati Marco Mirazita I.N.F.N. - Laboratori Nazionali di Frascati • Introduction and definition of the nucleon Form Factors • Space-like and time-like data • The DANAE project at Frascati QCD 06, Montpellier 3-7th July 2006

2. Nucleon Form Factors and QCD • QCD has been extensively tested in the high energy domain • asymptotic freedom  perturbative calculations (at percent level) • QCD at low energy is much more complicated • confinement several non-perturbative approaches, but no completely satisfactory agreement with data Nucleon FFs are one of the simplest non pQCD observables in the hadronic physics - fundamental quantities describing the internal structure of the nucleon from low (charge and magnetization distributions) to high Q2 regimes (valence quark distributions) - their calculation includes all the complications of the non-pQCD regime A succesfull non perturbative QCD model must be able to reproduce nucleon FF in all the q2 plane Nucleon FFs are also important for all process where nucleons are involved - GPDs - strange content of the nucleon - neutrino experiments

3. SL  TL → FF • Sachs Form Factors • Fourier transforms of nucleon charge and magnetization density distributions (in the Breit Frame). • Space-like form factors are real, time-like are complex. • The FF are analitic functions, thus space-like and time-like regions are connected by dispersion relations. • By definition GM and GE do not interfere in the expression of the cross section, therefore, in the timelike case, only polarization observables allow to get the relative phase. Dirac Pauli Nucleon EM Form Factors

4. old cross section data new polarization data The new data imply a completely different picture of the proton Fourier transform of GM and GE : charge and magnetization distributions Proton FF in the SL region JLab measurement with polarization transfer technique in ep → ep scattering • 2-photon exchange contributions? • Quark angular momentum?

5. |GM| proton • Time-like FF are complex  4 quantities to be measured • In general measured from total cross section and making some (arbitrary) assumption on the |GE|/|GM| ratio • Besides several questions posed by the data, basically |GE| remains unmeasured |GM| neutron |GE|=|GM| Independent extraction of |GE| and |GM| has been tried (LEAR and BaBar) - inconsistent results - large statistical errors |GE|=0 FF in the Time-like region

6. yellow band: fit of SL + BaBar TL data green band: fit of SL + LEAR TL data unphysical region ASYMPTOTICS space-like time-like Scaling “restoration” • Results not clear • Available data are not sufficient to get FF in the whole q2 plane QCD limit An important tool: DR One example: S. Pacetti et al. – Eur. Phys. J. C46,421 use of DR to fit the experimental data of the ratio |GE|/|GM| Time-like Form Factors HAVE TO BE MEASURED (polarization)

7. The physics case covers a broad spectrum • kaon physics (Ks rare decays, neutral kaon interferometry, , ’ physics) • kaonic nuclear physics (deeply bound kaonic nuclear states) • MEASUREMENT OF NUCLEON (and hyperon) FF • precision measurements above the f energy (hadronic cross section, vector meson spectroscopy, physics) • developments in the collider physics • application of the accelerator as synchrotron radiation source High luminosity High energy DAfne New with Adjustable Energy The DANAE project http://www.lnf.infn.it/lnfadmin/direzione/roadmap/roadmap.html • DANAE is a flexible collider that must ensure: • the maximum luminosity reachable at the f energy • the maximum reachable energy • a design capable of possible further developments The new machine will have: - one interaction region - one detector

8. LINAC DANAE layout INJECTION Sc rf SCwigglers Only one IR ACCUMULATOR IR

10. Moduli: extraction from d/d measurement q B y z x Phases: extraction from polarization measurements e- e+ relative phase B No beam polarization needed FF measurement in TL region Time like FFs are complex functions moduli & phases

11. 1 m The DAFNE detectors • KLOE • better resolution and coverage for charged particles (20o < q < 160o) • neutrons? • free space only in the vertex region • FINUDA • large amount of free space • good neutron detection • limited angular coverage • 45o < q < 135o

12. |GM| |GE| proton neutron |GM| FF measurement: projected accuracy Integrated luminosity  700-1000 pb-1 Statistical error of the order of few percent for the proton and below 10% for the neutron in the whole explored region

13. Integrated luminosity 2 years of data taking with the expected DANAE luminosity

14. Tentative schedule • T0 CDR and Project approval (2006) • T0 + 1 year call for tender • T0 + 2 years construction and delivery • T0 + 3 years DAFNE decommissioning and DANAE installation • T0 + 4 years 1st beam for commissioning and for 1st experiment (2010)

15. VEPP2000 • max energy ~ 1 GeV per beam, luminosity ~ 1032 cm-2 s-1 • pp and nn measurement, no polarization measurements • start run ~ 2007 • BEPC • energy range ~ 2.4-4.2 GeV, luminosity ~ 1033 cm-2 s-1 • only pp measurement, no polarization measurements • start run ~ 2007 • PANDA-PAX • inverse reaction pp → e+e- (no neutron measurement) • single and double polarization measurements • start run >2013 DANAE proton neutron s (GeV) 2.0 2.4 4.2 MN Competitors

16. Summary • A new project for an e+e- storage ring collider at Frascati is been developping. • The new machine will be upgraded in energy and luminosity and it is designed to run in two modes: • High energy (up to 1.2 GeV energy per beam) • High luminosity (up to 1033 cm-2 sec-1 at  energy) For both cases interesting physics programs has been proposed • The study of Nucleon (and hyperon) FF will be one of the main goal of the high energy part of the project • independent extraction of magnetic and electric FF at the few percent level for the proton and < 10% for the neutron • the first measurement of the complex phase of FF • first measurement of FF of hyperons (L, S, ..) including the phase