Physics perspectives at JLab with 12 GeV beam Marco Mirazita INFN – Laboratori Nazionali di Frascati XCVI Congresso Nazionale della Societa’ Italiana di Fisica Bologna, 20-24 Settembre 2010

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

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

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 1996 End physics program @ 6 GeV in 2012

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 2008-2014: Construction (funded at 99% by DOE- cost 310 M$) May 2012 6 GeV Accelerator Shutdown starts May 2013 Accelerator Commissioning starts October 2013 Hall Commissioning starts 2013-2015 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

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

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 2010-11) Different models predicts different asymptotics; will the ratio cross the zero?

FF experiments at JLab12 HALL A HALL B High momentum proton detection requires upgrade of the existing spectrometer E12-07-109: Large acceptance proton Form Factor ratio measurements at 13 and 15 (GeV/c)2 using recoil polarization method E. Cisbani co-spokesperson E12-09-016: Measurement of the neutron electromagnetic Form Factor ratio GEn/GMn at high Q2 E12-09-019: Precision measurement of the neutron magnetic Form Factor up to Q2=18(GeV/c)2 by the rario mathod HALL A E12-07-104: Measurement of the neutron magnetic Form Factor at high Q2 using the ratio method on the deuterium HALL B

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

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

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)

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~ 5 1033

SIDIS experiments at JLab12 HALL A PR-09-018: Measurement of the Semi-Inclusive p and K electro-production in DIS regime from transversely polarized 3He target E. Cisbani co-spokesperson New SBS E12-09-007: Studies of partonic distributions using semi-inclusive production of Kaons M. Mirazita co-spokesperson E12-09-008: Studies of the Boer-Mulders asymmetry in Kaon electroproduction with hydrogen and deuterium targets M. Contalbrigo co-spokesperson E12-09-009: Studies of spin-orbit correlations in Kaon electroproduction in DIS with longitudinally polarized hydrogen and deuterium targets E. Cisbani, P. Rossi co-spokesperson E12-06-112: Probing the Proton’s Quark Dinamics in Semi-Inclusive Pion Production at 12 GeV E12-07-107: 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

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

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 .

“Probing Strangeness in Hard Processes” Workshop: “Probing Strangeness in Hard Processes” Laboratori Nazionali di Frascati October 18-21, 2010 http://www.lnf.infn.it/conference/pshp2010/index.html

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

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

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

Meson Spectroscopy beyond the quark model (qq angular momentum) - L = 0 1 2 3 4 5 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 - 3.0 GeV (5 GeV < Eg <9 GeV) Lattice-QCD predictions for the lowest hybrid states 0++ 1.6 GeV 1-+ 1.9 GeV

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

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)