The partonic structure of protons and nuclei: from current - PowerPoint PPT Presentation

The partonic structure of protons and nuclei: from current facilities to the EIC Alberto Accardi Hampton U. and Jefferson Lab “Frontiers in Nuclear and Hadronic Physics” Galileo Galilei Institute, Florence, Italy 20-24 February 2017

Plan of the lectures  PART 1: QCD factorizatjon and global PDF fjttjng • Lecture 1 – Hadrons, partons and Deep Inelastjc Scatuering • Lecture 2 – Parton model • Lecture 3 – The QCD factorizatjon theorem • Lecture 4 – Global PDF fjts  PART 2: Parton distributjons from nucleons to nuclei • Lecture 5 / 6  PART 3: The next QCD frontjer – The Electron-Ion collider • Lextures 7 / 8 2 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Plan of Part 1  Lecture 1 – Motjvatjon – Quarks, gluons, hadrons – Deep Inelastjc Scatuering (DIS)  Lecture 2 – Parton model – DIS revisited – Collinear factorizatjon and Parton Distributjon Functjons (PDFs) – Limitatjons  Lecture 3 – The QCD factorizatjon theorem – QCD factorizatjon, universality of PDFs – DIS, Drell-Yan (DY) lepton pairs, W and Z productjon, hadronic jets  Lecture 4 – Global PDF fjts – How to make a fjt, and use its results – Fits as community service ( e.g. , measure PDFs, apply to LHC) – Fits as a tool to study hadron and nuclear structure 3 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Resources  Textbooks – Povh et al., “Partjcles and Nuclei,” Springer, 1999 – Halzen, Martjn, “Quarks and leptons,” John Wiley and sons, 1984 – Lenz et al. (Eds.), “Lectures on QCD. Applicatjons,” Springer, 1997 • esp. lectures by Levy, Rith, Jafge – Devenish, Cooper-Sarkar, “Deep Inelastjc Scatuering,” Oxford U.P., 2004 – Feynman, “Photon-hadron interactjons,” Addison Wesley, 1972 – Collins, “Foundatjons of perturbatjve QCD”, Oxford U.P, 2011  PDFs and Global QCD fjttjng – Jimenez-Delgado, Melnitchouk, Owens, “Momentum and helicity distributjons in the nucleon”, arXiv:1306.6515 – Forte, Watu, “Progress in partonic structure of proton”, arXiv:1301.6754 – J.Owens, “PDF and global fjttjng”, 2007 / 2013 CTEQ summer school  Lectures (from the CTEQ pedagogical page) – W.K. Tung, “pQCD and parton structure of the nucleon” – B. Poetuer, “Calculatjonal Techniques in pQCD: The Drell-Yan Process” 4 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Lecture 1 – Motivation  An illustrated introductjon – Hadrons are made of quarks and gluons – How to probe the partonic structure of hadrons  Deep Inelastjc Scatuering (DIS) – A bit (!) of kinematjcs – Cross sectjon – Structure functjon  A taste of the parton model 5 accardi@jlab.org GGI, Feb 2017 – Lecture 1

An illustrated introduction 6 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Motivation: quarks, gluon, hadrons...  The strong force is described in terms of colored quarks and gluons: “color” a quark a gluon  But only color neutral hadrons can be detected – color confjnement – How can one understand, say, proton and neutrons in terms of quark and gluons? – And, for that matuer, what's the evidence for quarks and gluons? 7 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Hadrons are made of quarks  6 fmavors (and 3 colors): up, down, strange – light charm, botuom, top – heavy spin ½; charge (elm, weak) isospin ( u = ½, d = – ½) strangeness ( s = 1)  Confjned in “colorless” hadrons – mesons – 2 quarks – baryons – 3 quarks – Tetraquarks (?) – Pentaquarks (???) – Hybrids (quarks+gluons) … – Glueballs ... 8 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Hadrons are made of quarks nucleons  6 fmavors (and 3 colors): up, down, strange – light charm, botuom, top – heavy spin ½; charge (elm, weak) isospin ( u = ½, d = – ½) strangeness ( s = 1)  Confjned in “colorless” hadrons – mesons – 2 quarks – baryons – 3 quarks – Tetraquarks (?) – Pentaquarks (???) – Hybrids (quarks+gluons) … – Glueballs ... 9 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Nucleons are made of 3 quarks… Parton Distributjon Functjons (PDF) Fractjonal momentum: 10 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Nucleons are made of 3 quarks… Parton Distributjon Functjons (PDF) Fractjonal momentum: 11 accardi@jlab.org GGI, Feb 2017 – Lecture 1

… and gluons, and sea quarks … Parton Distributjon Functjons (PDF) 12 accardi@jlab.org GGI, Feb 2017 – Lecture 1

… and gluons, and sea quarks … Parton Distributjon Functjons (PDF) 13 accardi@jlab.org GGI, Feb 2017 – Lecture 1

… spinning and orbiting around... Much studied at: JLab, HERMES, COMPASS, RHIC Fundamental topic at: JLab 6, Electron-Ion-Collider (EIC) 14 accardi@jlab.org GGI, Feb 2017 – Lecture 1

...and interacting inside nuclei  EMC efgect discovered more than 30 years ago: ? ? – A ≠  p,n – quarks / hadrons modifjed inside a nucleus – stjll a theoretjcal mystery 15 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Evidence for quarks and gluons 16 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Evidence for quarks and gluons – a whirlwind tour  Baryon spectroscopy – light sector ( u , d , s ), ground state – J=3/2 + : | q 1 ↑ , q 2 ↑ , q 3 ↑ ⟩ totally symmetric w.fn. – J=1/2 + : | q 1 ↑ , q 2 ↑ , q 3 ↓ ⟩ Fig: [from Povh et al.] 17 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Evidence for quarks and gluons – a whirlwind tour  Baryon spectroscopy – light sector ( u , d , s ), ground state – J=3/2 + : | q 1 ↑ , q 2 ↑ , q 3 ↑ spin symmetric, color antjsymmetric ⟩ – J=1/2 + : | q 1 ↑ , q 2 ↑ , q 3 ↓ spin antjsymmetrics, color symmetric ⟩ Fig: [from Povh et al.] 18 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Evidence for quarks and gluons – a whirlwind tour  e + + e – annihilatjon into hadrons – quark-mediated process [htup://www.quantumdiaries.org/author/richard-ruiz/] 19 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Evidence for quarks and gluons – a whirlwind tour  e + + e – annihilatjon into hadrons – quark-mediated process naïve quark model 3-loop calculatjon [from Partjcle Data Book, pdg.lbl.gov] 20 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Evidence for quarks and gluons – a whirlwind tour  Jets in high-energy e + + e – collisions – Hadron produced in 2, 3, … N, high-energy collimated “jets” – Evidence of common origin from a parton Fig.: 2- and 3-jet events observed by the JADE detector at PETRA [from Povh et al.] 21 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Probing the quark and gluon structure of a hadron 22 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Probing the nucleon parton structure  Need large momentum transfer Q 2 = q m q m to “resolve” partons  Example 1: Deep Inelastjc Scatuering (DIS) – Photon wave-length in rest frame, neglect proton mass M / Q ≪ 1: – E.g. , for x =0.1, Q 2 =4 GeV 2 (and puttjng back c and hbar ), l = 10 -17 m = 10 -2 fm to be compared with R p ≈ 1 fm 23 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Probing the nucleon parton structure  Need large momentum transfer Q 2 = q m q m to “resolve” partons  Example 1: Deep Inelastjc Scatuering (DIS) 24 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Probing the nucleon parton structure  Need large momentum transfer Q 2 = q m q m to “resolve” partons  Example 2: Lepton-pair productjon (“Drell-Yan” process) 25 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Probing the nucleon parton structure  Need large momentum transfer Q 2 = q m q m to “resolve” partons  Example 3: jet productjon in p+p collisions 26 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Deep Inelastic Scattering 27 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Kinematics  Inclusive lepton-hadron scatuering: Virtual photon momentum Hadronic fjnal state momentum – Notatjon: – Masses: 28 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Kinematics  Inclusive lepton-hadron scatuering: Virtual photon momentum Hadronic fjnal state momentum – Notatjon: – Masses:  The photon is virtual: q 2 < 0 Neglect compared to q 2 (MeV vs. GeV) 29 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Kinematics  Inclusive lepton-hadron scatuering: Virtual photon momentum Hadronic fjnal state momentum – Notatjon: – Masses: 30 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Kinematics  Inclusive lepton-hadron scatuering: Virtual photon momentum Hadronic fjnal state momentum – Notatjon: – Masses:  Measuring q 2 (see [Levy]) : – Scatuered lepton – Hadronic fjnal state – Mixed methods 31 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Kinematics  Lorentz invariants virtuality Bjorken x beam energy loss * center-of-mass (fjnal state) inelastjcity * energy invariant mass * interpretatjon valid in hadron rest frame, see later 32 accardi@jlab.org GGI, Feb 2017 – Lecture 1

Kinematics  Lorentz invariants virtuality Bjorken x beam energy loss * center-of-mass (fjnal state) inelastjcity * energy invariant mass – Ex.1 (easy) – Do these 6 invariants exhaust all possibilitjes? – Ex.2 (easy) – Are all 6 independent of each other? Prove that: * interpretatjon valid in hadron rest frame, see later 33 accardi@jlab.org GGI, Feb 2017 – Lecture 1