DA F NE-2 plans for the study of Nucleon Form Factors

1. DAFNE-2 plans for the study of Nucleon Form Factors Marco Mirazita INFN Laboratori Nazionali di Frascati Workshop on Nucleon Form Factors Frascati, 12-14 October 2005

2. See talk by S. Pacetti on DR analysis of proton FFs • Time-like FFs are basically unknown • Poor knowledge of the absolute values • Phases never measured Why measure time-like FFs • Proton FFs have been measured from threshold up to ~15 GeV2 • in e+ e-→ p pbar (ADONE, DM1-2, FENICE, BaBar) • p pbar → e+ e- (PS135 and PS135 at CERN, E760 and E835 at FNAL) TOTAL CROSS SECTION PLUS THE ASSUMPTION |GE|=|GM| Space-like data showed that this relation is valid only at threshold Different hypothesis on |GE|/|GM| produce large changes in the FF

3. Accurate measurement of pp and nn cross section •  model-independent extraction of proton and neutron FFs • First measurement of outgoing proton (neutron) polarization •  relative phase between GE and GM • First measurement of L (S) baryon production (including polarization) •  strange baryon FF • Study of angular asymmetry in pp (nn) distributions •  look for 2-photon contribution • Measurement of e+ e-→hadrons and other exclusive multipion processes •  sub-threshold NN resonance • … and many other processes Proposal for nucleon FF measurement at DAFNE2 A Letter of Intent has been already signed by more than 70 physicist from 22 institution and 6 countries

4. Experimental requirements • Beam requirements: • beam energy >1 GeV • high luminosity ~1032 cm-2 s-1 (cross section ~ 0.1-1 nb) • beam polarization not required (but could help) • Detector requirements: • high detection acceptance for charged and neutral particles • identification of exclusive final state • - protons  momentum+TOF • - high neutron efficiency • - detection of antinucleons  converter • installation of a polarimeter • - carbon analyzer + 2 tracking systems

5. Peak luminosity at the F mass (cm-2 s-1) DAΦNE energy upgrade • Minimal modifications to reach 1.2 GeV per beam • interaction region (only one) • vacuum chambers • dipoles (normal conducting) • control system • diagnostic • Injection at 510 MeV keeping the present injection system • ramp up time ~ minutes • beam life time ~ hours

6. DAΦNE parameters for 1.2 GeV operation

7. KLOE 1 m The DAFNE detectors FINUDA

8. ISIM OSIM nuclear targets TOFino vertex region 1 cm The FINUDA detector • Two series of 8 drift chambers, 6 cm thick each • 6 layers of straw tubes (total thickness 16 cm) • TOFone (72 scintillators, 10 cm thick) drift chambers straw tubes TOFone 10 cm • Beam pipe (Be, 0.5 mm thick) • TOFino (12 scintillators, 0.2 cm thick) • ISIM (8 modules, 300 m thick) • Nuclear targets • OSIM (10 modules, 300 m thick)

9. Track reconstruction with FINUDA • Number of hits per particle • Inner region: • TOFino 1 • ISIM 1 • OSIM 1 • Vertex region • DC 2 • straw 1 • TOFone 1 Ep = 1.2 GeV pp = 748 MeV/c • 7 total hits per particle, at least 4 hits for the track fit • Back-to-back events  use hits of both nucleons

10. beyond vtx region before DC ISIM OSIM TOFino Antinucleon converter Carbon seems to be the best choice ( proton polarimeter) Two possible otpions Between inner and outer regions 8 carbon “targets” vertex region 1 cm

11. e+e-pp with FINUDA Low energy protons: annihilation can help s = 1890 MeV, B = 0.2 T

12. E=1.2 GeV E=1.1 GeV E=1.0 GeV Efficiency and resolution for pp tracks PRELIMINARY MC STUDY B=10 kgauss proton efficiency For comparison in real data: - Muons in K+ → m+ n s/p<1% for Pm=235 MeV/c

13. |GM| |GE| FINUDA Max sensitivity to |GE| Proton angular distributions • Projected data assuming |GE| = |GM| • Integrated luminosity L=100 pb-1 • Constant detection efficiency e=80% • fit of angular distributions in the FINUDA coverage • F(q)=A(1+cos2q)+Bsin2q

14. e+e-nn with FINUDA 1.5 cm carbon converter A. Filippi, INFN Torino s = 1890 MeV, B = 0.2 T • strong gg background reduction if Ntracks > 2 • neutron TOF signal in coincidence

15. |GM| |GE| FINUDA Neutron angular distributions • Projected data assuming |GE| = |GM| (black) or |GE| = 0 (red) • Integrated luminosity L=100 pb-1 • Constant detection efficiency e=15% • fit of angular distributions in the FINUDA coverage • F(q)=A(1+cos2q)+Bsin2q

16. proton neutron FF measurement: projected accuracy prototne Integrated luminosity  700-1000 pb-1 KLOE in last 12 months: 1800 pb-1 at F mass

17. Polarization normal to the scattering plane No beam polarization • non negligible polarization • Py maximal at 45° and 135° • high discriminating power between theories • extraction of FF relative phase Induced polarization

18. The polarization is measured through secondary scattering in a strong interaction process • The spin-orbit coupling causes an azimuthal asymmetry in the scattering p z’ tracking system drift chambers straw tubes TOFone f qs Analysing power p tracking system analyzer Vertex region OSIM e- e+ P PC qp Polarization measurement

19. Fits of exp. data Average values q=5°-20° T=260 MeV T=100 MeV T=60 MeV Multiple scattering cut Carbon analysing power Ac known from few tenths of MeV up to some GeV

20. y Polarization is extracted by measuring asymmetries f - + For example, for Pypol( cosf) x Polarization ~ 15% max (pQCD model) Averaged analysing power ~ 50 % Polarization measurement Expected effect of the order of few % at EBEAM = 1.2 GeV For ΔR/R 30 %: total luminosity 2500 pb-1 (1 year with average 1032 cm-2 s-1)

21. Integrated luminosity

22. Conclusions • The increase of DAΦNE energy above the nucleon-antinucleon threshold is possible with minor changes in the machine • FINUDA is well suited for the Nucleon FF measurement • - good proton resolution • - adequate neutron detection • - easy implementation of a polarimeter • Possibility to improve the neutron detection • - two (or more) converters • - new array of scintillators just before the end-cap • - neutron polarimeter