JLab experiment results and future perspectives Patrizia Rossi

JLab experiment: results and future perspectives Patrizia Rossi - 39 th LNF Scientific Committee - October 26, 2009

5 Recirculation Arcs Jefferson Lab & Cebaf Newport News (VA) - USA 0. 6 Ge. V Linac 45 Me. V Injector 0. 6 Ge. V Linac Extraction element A B C Three Simultaneous Beams with Independently Variable Energy and Intensity complementary, long experiments Ee max : 6 Ge. V imax : 200 A Duty Factor : 100% (CW beam) Pe : 85% L > 106 x SLAC at the time of the original DIS experiments

Hall A: Two High Resolution (10 -4) Spectrometers L[cm-2 s-1] = 1039 High-precision electron-hadron coincidence exp. Hall B: The CEBAF Large Acceptance Spectrometer (CLAS) L[cm-2 s-1] = 1034 Electron and real photon exclusive reactions with multiparticle final states Hall C: A High Momentum and a Short Range Spectrometer L[cm-2 s-1] = 1039 High momentum final state and coincidence experiments with unstable particles

JLab physics program From nuclei to quarks: a laboratory from “strong” to perturbative QCD ce n a t Dis ergy quarks gluons En few body heavy nuclei quarks gluons vacuum Start physics program in 1996 End physics program @ 6 Ge. V in 2012

add Hall D (and beam line) 6 Ge. V 12 Ge. VCEBAF 2008 -2014: Construction (funded at 99% by DOE- cost 310 M$) Upgrade magnets and power supplies CHL-2 Glue. Ex May 2012 6 Ge. V Accelerator Shutdown starts May 2013 Accelerator Commissioning starts October 2013 HRS CLAS 12 SHRS Hall Commissioning starts 2013 -2015 Pre-Ops (beam commissioning) Enhance equipment in existing halls Imax = 90 A Emax Hall A, B, C: 10. 9 Ge. V Emax Hall D: 12 Ge. V The performance and design characteristics of the CEBAF accelerator has allowed an energy upgrade without modification of the basic layout

Structure of the nucleon form factors nucleon resonances Δ(1232), N*(1440), S 11(1535), D 13(1520) (generalized) ONE OF THE MAIN parton. FORCES distributions DRIVE OF THE 12 GEV UPGRADE spin, tomography

Nucleon Form Factors La J e b r fo Be Wit h. J Lab Jones et al. , PRL 84, 1398 (2000) Gayou eta al. , PRL 88, 092301 (2002) Punjabi et al. , PRC 71, 055202 (2005) Approved experiments @ 12 Ge. V OPE assumpion used in the Rosenbluth separation seems inadequate to describe the process Polarization transfer technique gives different results ! REVOLUTIONAZED OUR KNOWLEDGE OF CHARGE AND CURRENT IN THE NUCLEON Double polarization experiments only possible with high intensity, high polarized beam

Structure of the nucleon PDFs fpu(x), gpu(x), . . What we know (studied for decades) Measure momentum transfer to quark Direct info about momentum distributions No information about spatial location of partons Measure momentum transfer to target Direct info about spatial distributions No information about underlying dynamics Form Factors F 1 pu(t), F 2 pu(t ). . What we would like to know Probability to find a quark in a nucleon with a given polarization in a position r and momentum x, k. T

Structure of the nucleon Wigner Mother Functions GPDs TMD PDFs t=0 =0 (SI)DIS PDFs Form Factors JLab main program: determination of new multidimensional parton distribution functions in a large kinematics range Exclusive Reactions

Hard Scattering Processes: Kinematics Coverage collider experiments 0. 006/0. 02<x. B<0. 3 : gluons/valence and sea quarks Ge 27 V Q 2(Ge. V 2) COMPASS, HERMES 200 Ge H 1, ZEUS 10 -4<x. B<0. 02: Gluons and sea quarks fixed target experiments V H 1, ZEUS COMPASS HERMES e. V d ae r g 2 G p U 1 b a @ L e. V J ab G 2 L J = 11 11 Ge. V V e G W JLab/JLab@12 Ge. V 0. 1<x. B<0. 7 : valence quarks x f(x, Q) CTEQ 5 M parton distribution 0. 7 Q=5 Ge. V We are here! Kinematic suppression small cross section x Study of high x. B domain requires high luminosity

TMDs: Physics Motivation Nucleon spin as probed in DIS is incomplete! First attempt to explain the nucleon spin in the naive CQM framework k 0. 3 small could be large Transverse structure of the nucleon accessible through measurements of correlations between transverse momentum of quarks (k ) and the spin of the quark/nucleon

TMDs: experiments l N l’ Parton distributions *and fragmentation functions are universal measurements at different facilities q information provide complementary DF q q’ FF x FNAL BNL JPARC Factorization Theorem 8 TMD DF 8 TMD FF h =E-E’ Q 2=(k-k’)2 y= /E x=Q 2/2 M z=Eh/

TMDs: measurements program: access TMDs A 1 Jlab’s FUU µ f. ALL 1 D 1 (5 exp. approved @ 12 Ge. V) µ cos(2 ) h 1 H 1 Collins + A 2 cos(2 ) FUU advantages: + AJlab’s 3 l FLL µ g 1 D 1 • broad kinematical range & large x µ sin(2 ) h 1 L H 1 • high luminosity beam polarization (1) + A 5 S • high |sin( µ sin( S) f 1 T D 1 S)FUT + A 4 sin(2 )FUL + A 6 Asymmetries l S |cos( S)F µ cos( S) g 1 T D 1 measurements: LT statistics (2) + A 7 S • high |sin( S)FUT µ sin( S) h 1 H 1 (3) + A 8 S • Q |sin(3 2 dependence S)FUT µ sin(3 S) h 1 T H 1 • on the relevant variables: x, P , z Observables: spin azimuthal asymmetries correlations between transverse momentum of quarks and the spin of the quark/nucleon and appear as moments of (moments of

6 Ge. V: Current experiment in Hall A (E-06 -010) • Trasversely polarized 3 He target (Pol. ~ 65%) • Lumi ~ 1036/s/cm 2 HERMES on proton COMPASS on deuteron Sivers Function 1 month data taking: statistical errors comparable to HERMES (3 years) COMPASS (2 years)

6 Ge. V: Current Experiment in Hall B (E-015 -113) • Longitudinally polarized (NH 3/ND 3) target (Pol. >75%/30%) • Lumi=1. 5. 1034 cm-2 s-1 3 months data taking: ~ 10 times statistics accumulated by HERMES in 6 years!

TMDs Experiments @ 12 Ge. V HALL B E 12 -09 -007: Studies of partonic distributions using semi-inclusive production of Kaons M. Mirazita co-spokesperson E 12 -09 -008: Studies of the Boer-Mulders asymmetry in Kaon electroproduction with hydrogen and deuterium targets M. Contalbrigo co-spokesperson E 12 -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 E 12 -06 -112: Probing the Proton’s Quark Dinamics in Semi-Inclusive Pion Production at 12 Ge. V E 12 -07 -107: Studies of Spin-Orbit Correlations with Longitudinally Polarized Target (Pion) P. Rossi co-spokesperson HALL A PR-09 -018: Measurement of the Semi-Inclusive p and K electro-production in DIS regime from transversely polarized 3 He target with the SBS & BB spectrometers in Hall A E. Cisbani co-spokesperson

Global TMD Analysis In SIDIS always 2 unknown functions involved which cannot be measured independently UNIVERSALITY appears to be proven in LO by Collins and Metz [PRL 93, 252001 (2004) ee+ Hermes/p + COMPASS/d (Q 2~2. 5 Ge. V 2) e+e- from BELLE (Q 2=110 Ge. V 2) ONLY Fragmentation Function H 1 Anselmino et al, Nucl. Phys. Proc. Suppl. 191: 98 -107, 2009

GPDs: Physics Motivation proton state = over Fock states * the corresponding w. f. x. P PDF ~ p(P) Probability density Probability to find a quark with a fraction x of the momentum of the proton In Q. M. the sole probabilities that the system is in a particular state is not enough for a FULL description of the state off-diagonal elements need! xin. P p(P) x’out. P’ p(P’) GPD ~ Interference of probability amplitudes NO probabilistic interpretation! GPDs are the generalization of parton distribution functions They measure the quark momentum correlations in the nucleon

GPDs: from theory to experiments e’ e , L*(Q 2) x+ξ p ~ ~ x-ξ ~ H, H, E, E (x, ξ, t) GPDs: set of mathematical functions accessible through HARD EXCLUSIVE processes p’ x = long. mom. fraction = long. mom. transfer = x. B/2 -x. B t = (p-p’)2 t Fourier transform of GPDs gives simultaneous distributions of quarks w. r. t. longitudinal momentum x P and transverse position b The form factor limit: ~ The forward limit: t 0, 0 The Ji’s sum rule: t 0, 0 2 Jq = x(H+E)(x, ξ, 0)dx longitudinal momenta of the parton related to tranfer momenta of the parton

GPDs: from theory to experiments • VM ( : H E Quantum number of final state selects different GPDs: ~ ~ • PS mesons ( : H E ~ ~ • DVCS ( ): H, E, H, E Deeply Virtual Compton Scattering (DVCS) Re[F 1 H] Im[F 1 H] ~ Im[F 1 H] Im[F 2 H- F 1 E] ~ ~ Re[H, H, E] - complete analysis up to twist-3 - factorization proved at all orders - sensitive to all GPDs ALL AVAILABLE AT JLAB

DVCS: Polarized Beam Asymmetry +- = A= + 2 + - ep ep LU~sin {F 1 H+…}d Extract H(ξ, t)

Measuring GPDs: experimental requests • but only and t accessible experimentally • x is mute variable (integrated over): apart from cross-over trajectory ( =x) GPDs not directly accessible: deconvolution needed ! (model dependent) GPD moments cannot be directly revealed extrapolations t 0 are model dependent high+variable beam energy hard regime wide kinematic range high luminosity small cross sections measure in 3 kinematic variables simultanously complete event reconstruction ensure exclusivity JLab fits these requirements

Nucleon tomography [M. Burkardt, M. Diehl 2002] FT (GPD) : momentum space impact parameter space: probing partons with specified long. momentum @transverse position b T polarised nucleon: u-quark d-quark from lattice

Gluonic Excitations and the Origin of Confinement • QCD predicts a rich spectrum of - as yet to be discovered - gluonic excitations whose experimental verification is crucial for an understanding of QCD in the confinement regime • With the upgraded CEBAF and linearly polarized photon beam JLab will be uniquely poised to: (1) discover these states (2) map out their spectrum and (3) measure their properties A NEW EXPERIMENTAL HALL DEDICATED TO THIS PROGRAM

Meson Spectroscopy: beyond the quark model hybrids & exotics 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) Exotic nonets Hybrid mesons and glueballs mass range: 1. 4 Ge. V - 3. 0 Ge. V (5 Ge. V < Eg <9 Ge. V) Lattice-QCD predictions for the lowest hybrid states L= 0 1 2 3 4 5 - (qq angular momentum) 0++ 1. 6 Ge. V 1 -+ 1. 9 Ge. V

Meson Spectroscopy with photons at JLab-12 Photoproduction: exotic JPC are more likely produced by S=1 probe The detectors Determination of JPC of meson states requires Partial Wave Analysis Decay and Production of exclusive reactions Good acceptance, energy resolution, particle Id Hermetic charged/neutral particles detector Coherent tagged Bremss. (HALL D) quasi-real (HALL B) E (Ge. V) 6 -11 7 -10 E (Ge. V) 0. 01 Flux ( /s) 107 -108 5 x 107 L (cm-2 s-1) 1031 1034 Polarization ~50%-15% (collective) ~65%-20% (individual) The photon beam Tagger (E ) : required to add 'production' information to decay Linear polarization: useful to simplify the PWA analysis High intensity High energy (5 -9 Ge. V)

What else… http: //www. jlab. org/12 Ge. V/ The 12 Ge. V research program will allow breakthroughs to be launched in five main areas: • Through the search for exotic mesons, in which gluons are an unavoidable part of the structure, researchers will explore the fascinating and complex vacuum structure of QCD and the nature of confinement. • Through extremely high precision studies of parity violation, developed in order to study the role of hidden flavors in the nucleon, researchers can explore physics beyond the Standard Model, on an energy scale that cannot be explored even with the proposed International Linear Collider. • The combination of luminosity, duty factor and kinematic reach of this machine will far surpass anything available up to this point, allowing the nuclear physics community a previously impossible view of the spin and flavor dependence of the valence parton distributions - the heart of the proton, where its quantum numbers are determined. • Researchers will be able to take a revolutionary look into the structure of atomic nuclei, exploring Parity violation and mixing angle at low energy how the valence quark structure is modified in a dense nuclear medium. These studies will give the world a far deeper and more fundamental understanding of the structure of atomic nuclei with far-reaching implications for all of nuclear physics and nuclear astrophysics. • The Generalized Parton Distributions will allow researchers, for the first time, to engage in nuclear tomography, discovering the true three-dimensional structure of the nucleon.

JLAB 12: Italian Collaboration @ Jefferson Lab SBS ed e’ n(p) CLAS 12 neutron detector q Institutions: Bari, e’Catania, Ferrara, Genova, Laboratori Nazionali di Frascati, ISS/Roma I, Roma II t e L*(Q 41 ) (~30 FTE) q Researchers: Techniciens: x+ξ 25 (~12 FTE) 2 x-ξ gap ~ & Hall BReplace 2 sectors q Research A n activity. H, in. H, Hall E, E (x, ξ, t) of LTCC with n’ a proximity Main fields of investigations: TMDs, GPDs, RICH Nucleon Form Factors, Meson ~ 60 detector m Spectroscopy cm 40 c Forward Tagger ~ q Hardware contribution to the 12 Ge. V upgrade: ~ 10 for m the n. DVCS measurement (Hall B) Neutron Detector ~7 m SBS Front tracker for the proton form factor measurement at high Q 2 (Hall A) RICH detector for TMDs measurements (Hall B) Forward tagger for meson spectroscopy investigation (Hall B)

Conclusions It is hard to fit in 1/2 hour presentation the broad experimental program carried out at Jlab and foreseen for the 12 Ge. V upgrade I hope having been able to give the feeling that Jefferson Lab place itself at the Forefront of Hadron Physics