1. Physics perspectives at JLab with 12 GeV beam
Marco Mirazita
INFN – Laboratori Nazionali di Frascati
XCVI Congresso Nazionale della Societa’ Italiana di Fisica
Bologna, Settembre 2010

2. INFN is involved in the JLab activity since 1991
Jefferson Lab & Cebaf A B C
Extraction element
0.6 GeV Linac
45 MeV
Injector
5 Recirculation Arcs
Newport News (VA) - USA
Three Simultaneous Beams with Independently Variable Energy and Intensity
Ee max : 6 GeV
Imax : 200 A
Duty Factor : 100% (CW beam)
Pe : 85%
INFN is involved in the JLab activity since 1991

3. Hall A: Two High Resolution (10-4) Spectrometers
L[cm-2s-1] = 1039
High-precision electron-hadron coincidence exp.
ELETTRO/LEDA
ISS+RM1+BA
Hall B: The CEBAF Large Acceptance Spectrometer (CLAS)
L[cm-2s-1] = 1034
Electron and real photon exclusive reactions with multi-particle final states
AIACE LNF+GE
Hall C: A High Momentum and a Short Range Spectrometer
L[cm-2s-1] = 1039
High momentum final state and coincidence experiments with unstable particles

4. Baryon and meson excitation spectrum 3D imaging of the nucleon
JLab physics program
From nuclei to quarks:
a laboratory from “strong” to perturbative QCD
Distance
Energy
heavy
nuclei
few
body
quarks
gluons
vacuum
quarks
gluons
Correlations
Hypernuclei
Eff. NN (+ΛN) force
n-radii: N  Z
Hadrons in-medium
Baryon and meson excitation spectrum
Missing resonances
Exotics
Parton D.F.
TMD
GPD
3D imaging of the nucleon
PV e-scattering
Strange FF
Start physics program in End physics 6 GeV in 2012

5. Upgrade magnets and power supplies
add Hall D
(and beam line)
GlueEx
CLAS12
CHL-2
Upgrade magnets and power supplies
12 GeV CEBAF
6 GeV CEBAF
HRS
SHRS
: Construction (funded at 99% by DOE- cost 310 M$)
May 2012
6 GeV Accelerator Shutdown starts
May Accelerator Commissioning starts
October 2013
Hall Commissioning starts
Pre-Ops (beam commissioning)
Enhance equipment in existing halls
Imax = 90 A
Emax Hall A,B,C: 10.9 GeV
Emax Hall D: 12 GeV

6. Structure of the nucleon
The complex structure of the nucleon can be described through a large variety of functions
PDF
longitudinal momentum distributions of partons
inclusive scattering
elastic FF
charge and current distributions
elastic scattering
transition FF
inelastic scattering
TMD
longitudinal and transverse momentum distributions of partons
semi-inclusive scattering
GPD
longitudinal momentum distributions at a given transverse point
exclusive reactions
JLab main program:
determination of multi-dimensional parton distribution functions in a large kinematics range

7. Nucleon FF FF Discrepancy between Rosembluth and
polarization methods is established: charge and current dist. are DIFFERENT
The reason is not completely clear, possible explanation can be TPE (CLAS measurement in )
Different models predicts different asymptotics; will the ratio cross the zero?

8. FF experiments at JLab12 HALL A HALL B
High momentum proton detection requires upgrade of the existing spectrometer
E : Large acceptance proton Form Factor ratio measurements at 13 and 15 (GeV/c)2 using recoil polarization method
E. Cisbani co-spokesperson
E : Measurement of the neutron electromagnetic Form Factor ratio GEn/GMn at high Q2
E : Precision measurement of the neutron magnetic Form Factor up to Q2=18(GeV/c)2 by the rario mathod
HALL A
E : Measurement of the neutron magnetic Form Factor at high Q2 using the ratio method on the deuterium
HALL B

9. The new SBS in Hall A New SBS tracker Requirements:
high luminosity (1038 cm-2 s-1 )
small angle coverage
Dp/p ~ 0.5% at 5-8 GeV/c
Dq ~ 2 mrad
relatively large acceptance
flexibility
New SBS tracker
large GEM tracking chambers
silicon detectors to improve resolution
Silicon
Detectors

10. The nucleon parton model
In the collinear approximation
Inclusive DIS Dist. Functions
Parton transverse momentum
more complex dist. functions
8 DF at leading twist
Transverse degrees of freedom are important
Nucleon spin decomposition:
 0.3 k
could be
large
small

11. SIDIS Observables PT
Semi-Incusive Deep Inelastic Scattering
e N  e’ h X
U unpolarized
L long.polarized
T trans.polarized
Target polarization
Beam helicity
s = sUU + ST sUT sin(f – fS) + l ST sLT cos(f – fS)
high intensity beam with high polarization
polarized targets
high acceptance for the hadron (charged or neutrals)

12. PDF and TMD measurements at 6 GeV
Measurements of PDF&TMD already play a big role in the 6 GeV program
With longitudinally polarized beam and/or target
- beam polarization ~70 %
- target polarization ~75% (H), ~30% (D)
Transversely polarized target: HD-ice
Several advantages:
high H (95%) and D (70%) polarization with high dilution factor
wider acceptance
Very complicated target:
long production cycle
need to optimize several parameters
can remain polarized under a high intensity electron beam?
photon run with HD-ice Mar-May 2011
test run with e- May 2011
physics run with e- (?)
Expected luminosity L~

13. SIDIS experiments at JLab12
HALL A
PR : Measurement of the Semi-Inclusive p and K electro-production in DIS regime from transversely polarized 3He target E. Cisbani co-spokesperson
New SBS
E : Studies of partonic distributions using semi-inclusive production of Kaons M. Mirazita co-spokesperson
E : Studies of the Boer-Mulders asymmetry in Kaon electroproduction with hydrogen and deuterium targets
M. Contalbrigo co-spokesperson
E : Studies of spin-orbit correlations in Kaon electroproduction in DIS with longitudinally polarized hydrogen and deuterium targets
E. Cisbani, P. Rossi co-spokesperson
E : Probing the Proton’s Quark Dinamics in Semi-Inclusive Pion Production at 12 GeV
E : Studies Studies of Spin-Orbit Correlations with Longitudinally Polarized Target (Pion) P. Rossi co-spokesperson
Kaon measurements are a large part of the TMD program in Hall-B
HALL B

14. PID in CLAS12
Low Threshold Cerenkov Counter (LTCC) for (p,K)/p separation
High Threshold Cerenkov Counter (HTCC) for e/p separation
Scintillator Counters (TOF) with timing resolution of 80 and 150 ps, for charged hadron ID
Electromagnetic Calorimeter, lead and scintillators for e/p separation and g/n detection
GeV/c 1 2 3 4 5 6 7 8 9 10
p/K
p/p
K/p
TOF
LTCC
HTCC
Need good Kaon ID in the 2-8 GeV/c momentum range
p/K rejection factor of 1:1000 for SIDIS experiments

15. The RICH project for CLAS12
Charged particle
Radiator
Proximity gap
Photon detector
Aerogel mandatory to separate hadrons in the momentum range 2-8 GeV/c
Collection of the visible Cherenkov light
 larger Npe
Small pad size (< 1cm)
 better resolution .

16. “Probing Strangeness in Hard Processes”
Workshop:
“Probing Strangeness in Hard Processes”
Laboratori Nazionali di Frascati
October 18-21, 2010

17. Generalized Parton Distributions
They represent interference of amplitudes
 NO probabilistic interpretation
DIS cross section
GPDs are the generalization of parton distribution functions when one allows:
- momentum transfer to the nucleon
- longitudinal momentum transfer to the quark
For the unpolarized or longitudinal polarized case, there are 4 GPDs
After Fourier transform:
longitudinal momentum distributions of quark at a given transverse point in the nucleon
 3D imaging of the nucleon
GPDs are not directly accessible
 need deconvolution
- model dependent

18. GPDs: from theory to experiments
Can be measured in exclusive electroproduction experiments
Deeply Virtual Compton Scattering (DVCS)
Different final state and/or polarizations selects different GPDs
DVCS (g): H, E, H, E
VM (r, w, f): H E
PS mesons (p, h): H E ~
Re[F1H]
Im[F1H] ~
Im[F2H- F1E]
Im[F2H- F1E]
Re[H,H,E]
DVCS observables

19. Measurement of GPD E Ji sum-rule: ALU(sinf) 
DVCS on the proton
DVCS on the neutron
CLAS12 Central Detector
Neutron Detector
nDVCS by detecting the scattered neutron in the central detector
Limitation:
High magnetic field (2-5 Tesla)
Limited space (mainly for the read-out)
Geometry of the detector is defined, electronic readout is under study
- SiPM
- MWPC
- readout from the backward side only

20. Meson Spectroscopy beyond the quark model
(qq angular momentum) -
L =
Exotic nonets
Meson map
Experimental signature for the presence of gluonic d.o.f. in the spectrum of mesonic states:
mesons with 'exotic' quantum numbers (not compatible with quark-model)
Hybrid mesons and glueballs mass range:
1.4 GeV GeV
(5 GeV < Eg <9 GeV)
Lattice-QCD predictions for the lowest hybrid states
GeV
GeV

21. Meson Spectroscopy with real photons
Meson (and baryon) spectroscopy with real photons is the main goal of the Hall-D
- exotic JPC more likely produced by J=1 probe
- production rate comparable to regular mesons
This program can be pursued in a complementary way in Hall-B
- high luminosity
- “tagging” of the photon
- linear polarization to simplify Partial Wave Analysis
Quasi-real electroproduction at low Q2 (<10-1 GeV2)
- detect scattered electron at small angle (2-5 deg)
- photon energy 7 < E < 10.5 GeV
- linear polarization ~ 65 – 20%
- photon flux ~ 5 107/s
calorimeter + tracking + veto
~ 40 cm

22. Conclusions
JLab12 is the new Collaboration, born in 2009, for the Italian activity at Jefferson Lab
Institutions: Bari, Catania, Ferrara, Genova, Laboratori Nazionali di Frascati, ISS/Roma I, Roma II
Researchers: 47 (~33 FTE)
Technicians: 31 (~13 FTE)
Research activity in Hall A & Hall B
Main fields of investigations: TMDs, GPDs, Nucleon Form Factors, Meson Spectroscopy
Hardware contribution to the 12 GeV upgrade:
Neutron Detector for the nDVCS measurement (Hall B)
SBS Front tracker for the proton form factor measurement at high Q2 (Hall A)
RICH detector for TMDs measurements (Hall B)
Forward tagger for meson spectroscopy investigation (Hall B)