M. Ripani INFN Genova Introduction

In less than three years from now, the Jefferson Lab upgrade will be completed, allowing to deliver energies up to 12 GeV During the same time span, several new detectors will be installed in Hall B, transforming the existing CLAS spectrometer into a new apparatus, CLAS12 Goals of this Workshop  To offer the opportunity to learn about the CLAS12 spectrometer, its baseline equipment and additional new detectors (where European institutions are playing a major role) that have been proposed to extend its capabilities  To illustrate the current physics program with the 12 GeV upgrade s well as new possible directions  To host presentations illustrating some intersections of the current and future CLAS program with experiments conducted or planned at other facilities  To strengthen existing ties and to foster new relationships between Jefferson Lab and European physicists interested in the 12 GeV physics Why this Workshop ?

The Workshop is held in conjunction with the periodic CLAS Collaboration meeting  besides presenting the 12 GeV physics already on the books and the CLAS12 instrumentation, we will present  Highlights from the current physics program at 6 GeV, in particular the status and results from recent runs  Updates on approved proposals that will go in front of the Jlab PAC to get rating and actual beam time assignments

I want to draw your attention on some specific aspects of CLAS Since the beginning of CLAS, the physics program is very diverse, because of  the large acceptance and multiparticle detection capability of the spectrometer  the availability of both electron and photon beam  the capability of installing several different targets, from liquid hydrogen to nuclei, to polarized targets for both photon and electron beams  and we even ran with electrons and positrons together via a double conversion of the primary electron beam !

The physics items covered by the 6 GeV program are: Physics of QCD bound states:  Elastic nucleon form factors  Excited baryon properties in photo- and electroproduction and search for new states predicted by models but not found  Meson properties and search for exotics Partonic structure of the nucleon Unpolarized and polarized  inclusive electron scattering  evolution of nucleon structure functions and their moments with the momentum transfer  semi-inclusive meson electroproduction  new parton distribution functions depending on the quark transverse momentum  exclusive hard processes (a hard photon or meson is produced while the nucleon remains intact)  generalized parton distribution functions  3D picture of nucleon Nuclear physics:  Electron scattering off nuclei, kicking off one or two nucleons  high momentum components and correlations  Meson photoproduction in nuclei  medium modifications  Meson electroproduction in nuclei  quark propagation in cold nuclear matter, color transparency

The physics of the 12 GeV program is also multifaceted: Physics of QCD bound states:  Elastic nucleon form factors and excited baryon properties at even higher momentum transfer  how a constituent quark can reveal its bare nature  Search for exotics Partonic structure of the nucleon  Inclusive nucleon structure functions at even higher Bjorken x  Semi-inclusive meson electroproduction  new PDFs depending on the quark transverse momentum  Exclusive hard processes  generalized PDFs  3D picture of quark motion and spin Nuclear physics:  Meson electroproduction in nuclei  quark propagation in cold nuclear matter, color transparency

The current CLAS Collaboration INFN, Sezione di Roma Tor Vergata, Rome, Italy IN2P3-IPNO, Orsay, France IN2P3-LPSC, Grenoble, France Irfu-SPhN, CEA-Saclay, France ITEP, Moscow, Russia James Madison University, Harrisonburg, VA Kyungpook University, Daegu, South Korea University of Massachusetts, Amherst, MA Moscow State University, Moscow, Russia University of New Hampshire, Durham, NH Norfolk State University, Norfolk, VA Ohio University, Athens, OH Old Dominion University, Norfolk, VA Rensselaer Polytechnic Institute, Troy, NY Rice University, Houston, TX University of Connecticut, Storrs, CT University of Richmond, Richmond, VA University of South Carolina, Columbia, SC Thomas Jefferson National Accelerator Facility, Newport News, VA Union College, Schenectady, NY Virginia Polytechnic Institute, Blacksburg, VA University of Virginia, Charlottesville, VA College of William and Mary, Williamsburg, VA Yerevan Institute of Physics, Yerevan, Armenia Brazil, Germany, Morocco and Ukraine, as well as other institutions in France and in the USA, have individuals or groups involved with CLAS, but with no formal collaboration at this stage. Arizona State University, Tempe, AZ University of California, Los Angeles, CA California State University, Dominguez Hills, CA Carnegie Mellon University, Pittsburgh, PA Catholic University of America Christopher Newport University, Newport News, VA Edinburgh University, Edinburgh, UK Florida International University, Miami, FL Florida State University, Tallahassee, FL George Washington University, Washington, DC University of Glasgow, Glasgow, UK Idaho State University, Pocatello, Idaho INFN, Sezione di Ferrara, Ferrara, Italy INFN, Laboratori Nazionali di Frascati, Frascati, Italy INFN, Sezione di Genova, Genova, Italy

CLAS12 - Institutions France: - IN2P3-LPSC, Grenoble - IN2P3-IPNO, Orsay - Irfu-SPhN, CEA-Saclay Armenia: - Yerevan Physics Institute, Yerevan, Armenia United Kingdom: - Edinburgh University, Edinburgh, Scotland - Glasgow University, Glasgow, Scotland Russian Federation: - MSU, Skobeltsin Institute for Nuclear Physics, Moscow - MSU, Institute for High Energy Physics, SiLab, Moscow - Institute for Theoretical and Experimental Physics, Moscow Italy: - INFN – LN Frascati, Rome - INFN - Genoa, Genoa - INFN - University Bari, Bari - INFN - University Ferrara, Ferrara - INFN – ISS, Rome - INFN – Rome II, Tor Vergata, Rome Republic of Korea: - Kyungpook National University, Daegu, Korea United States of America: - Argonne National Laboratory, Argonne, MI - California State University, Dominguez Hills, CA - Catholic University of America, Washington, DC - College of William and Mary, Williamsburg, VA - Christopher Newport University, Newport News, VA - Fairfield University, Fairfield, CT - Florida International University, Miami, FL - Hampton University, Hampton, VA - Idaho State University, Pocatella, ID - James Madison University, Harrisionburg, VA - Norfolk State University, Norfolk, VA - Ohio University, Athens, OH - Old Dominion University, Norfolk, VA - Renselaer Polytechnic Institute, Troy, NY - Temple University, Philadelphia, PA - Jefferson Lab, Newport News, VA - University of Connecticut, Storrs, CT - University of New Hampshire, Durham, NH - University, of Richmond, Richmond, VA - University of South Carolina, Columbia, SC - University of Virginia, Charlottesville, VA Chile: - University Santa Maria, Valparaiso 38 Institutions, November 7, 2010

Agenda Now let’s take a look at the I wish you an interesting, fruitful and enjoyable Workshop !