Hadron Structure Theory I. Alexei Prokudin

Transcription

1 Haron Strctre Theory I Alexei Prokin

2 The plan: l Lectre I: Strctre of the ncleon l Lectre II Transverse Momentm Depenent istribtions (TMDs) Semi Inclsive Deep Inelastic Scattering (SIDIS) l Ttorial Calclations of SIDIS strctre fnctions sing Mathematica Lectre III Avance topics. Evoltion of TMDs

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5 DOE fne Topical Collaboration for theory 5 years of fning of $2,160, instittions Theory, phenomenology, lattice QCD Several postoc positions. 2 tenre track positions: Temple, NMSU Spport of nergraates. 5 years of fning 18 instittions Theory, phenomenology, lattice QCD Several postoc an tenre track positions to be create To aress the challenges of extracting novel qantitative information abot the ncleon s internal lanscape To provie compelling research, training, an career opportnities for yong nclear theorists 5

6 Why is it so important for theory? We are a ata-riven science! 6

7 Stanar moel

8 Interactions Electromagnetism (photon) Atomic an Moleclar Bining Gravitation (graviton) Stars an Galaxies Weak Nclear Interaction (W,Z bosons) Nclear Beta Decay Strong Nclear Interaction (glon) Nclear Bining

9 This talk Stanar moel

10 Qark moel Proton Two p one own Netron Two own one p 10

11 Qark moel Proton Charge 2/3 + 2/3-1/3 = +1 Qark charges are fractional of positron s charge Netron 2/3-1/3-1/3 = 0 Qarks are bon (confine) by strong interaction (glons) 11

12 Qark moel Proton Netron Charge 2/3 + 2/3-1/3 = +1 Qark charges are fractional of positron s charge No evience of free qarks observe irectly in experiment Long istance - qarks are confine in harons Short istance - qarks behave as if they were free 2/3-1/3-1/3 = 0 Qarks are bon (confine) by strong interaction (glons) Asymptotic freeom - later in this talk! 12

13 Qantm Electro Dynamics an Qantm Chromo Dynamics Force carrier: QED Gage theory U(1) photon (electrically netral) electron positron Interaction 13

14 Qantm Electro Dynamics an Qantm Chromo Dynamics Force carrier: QED Gage theory U(1) photon (electrically netral) electron positron Interaction Richar Feynman, Nobel Prize 1965 for... fnamental work in qantm electroynamics" 14

15 Qantm Electro Dynamics an Qantm Chromo Dynamics Force carrier: QED Gage theory U(1) photon (electrically netral) electron positron Interaction QCD Gage theory SU(3) Force carriers: Interaction glons (carry color) qark anti-qark strong Richar Feynman, Nobel Prize 1965 for... fnamental work in qantm electroynamics" Glons interact with each other - non abelian theory 15

16 Asymptotic freeom The copling epens on the scale conseqence of renormalizability of the theory At short istances qarks behave as if they were almost free particles! long DISTANCE short for the iscovery of asymptotic freeom in the theory of the strong interaction" Gross, Politzer, Wilczek, Nobel Prize 2004

17 Scattering as the metho of sty Ernest Rtherthor, Nobel Prize 1908 for his investigations into the isintegration of the elements, an the chemistry of raioactive sbstances" 1911

18 Electron Scattering Detector of electrons Virtality of the photon electron scattere electron photon Detector of harons

19 Electron Scattering Detector of electrons Virtality of the photon electron scattere electron The photon probes istance of ~1/Q insie of the proton. Asymptotic freeom - photon scatters off a qark photon Detector of harons

20 Electron Scattering: interpretation Electromagnetic probe resolves a qark or anti-qark with momentm p=xp insie of the proton of momentm P. Bjorken variable Gives the fraction of longitinal momentm of the proton carrie by the parton

21 Electron Scattering: interpretation Experimental ata Behavior is almost flat qarks are pointlike

22 Electron Scattering: interpretation Unlike the proton itself: Proton size ~ 1 fm

23 Exploring the ncleon: a fnamental qest Know what we are mae of! Unerstan the strong force: QCD Use protons as tool for iscovery (e.g. LHC ) 23

24 Why Spin? Xiangong Ji at DIS08 Spin is a fnamental qantm egree of freeom Spin plays a critical role in etermining the basic strctre of fnamental interactions Test of a theory is not complete withot a fll test of spin-epenent ecays an scattering Spin provies a niqe opportnity to probe the inner strctre of a composite system (sch as the proton) 24

25 Spin an QCD Experiments with spin have kille more theories than any other single physical parameter Elliot Leaer, Spin in Particle Physics, Cambrige U. Press (2001) Polarization ata has often been the graveyar of fashionable theories. If theorists ha their way they might well ban sch measrements altogether ot of self-protection. J. D. Bjorken, Proc. Av. Research Workshop on QCD Haronic Processes, St. Croix, Virgin Islans (1987). See lectres by Thomas Ullrich an Anselm Vossen

26 Ncleon lanscape Ncleon is a many boy ynamical system of qarks an glons Changing x we probe ifferent aspects of ncleon wave fnction How partons move an how they are istribte in space is one of the irections of evelopment of nclear physics Technically sch information is encoe into Generalise Parton Distribtions (GPDs) an Transverse Momentm Depenent istribtions (TMDs) These istribtions are also referre to as 3D (three-imensional) istribtions 26

27 Unifie View of Ncleon Strctre Wigner fnction 5D Transverse Momentm Depenent istribtions Generalize Parton Distribtions 3D Parton Distribtion Fnctions Form Factors 1D Alexei Prokin