Presentation on theme: "Drell-Yan Experiments for determining Nucleon Partonic Structures Wen-Chen Chang Institute of Physics, Academia Sinica, Taiwan The International Symposium."— Presentation transcript:
Drell-Yan Experiments for determining Nucleon Partonic Structures Wen-Chen Chang Institute of Physics, Academia Sinica, Taiwan The International Symposium on Physics of Unstable Nuclei 2014 ISPUN14 Ho Chi Minh City, Vietnam, November 3-8, 2014
How to Probe the Structure of Nucleus / Nucleon? 2 Shoot high-energy beam
Elastic Electron Scattering of Nuclei and Nucleons 3 Nuclear Form Factor Nucleon Form Factor Charge distributions of nuclei and protons.
From Elastic Scattering to Deeply Inelastic Scattering (DIS) 4 Elastic scattering Inelastic scattering Very weak Q 2 -dependence, form factor 1! Scattering off point-like objects? Very weak Q 2 -dependence, form factor 1! Scattering off point-like objects?
Quark-Parton Model (Feynman) 5 p quark = xP proton 0 < x < 1 Limiting case: x = 1, elastic scattering Bjorken-x: momentum fraction of struck parton
Pauli blocking of valance quarks (Field and Feynman 1977) Meson cloud in the nucleons (Thomas 1983, Kumano 1991) : Sullivan process in DIS. Chiral quark model (Eichten et al. 1992; Wakamatsu 1992): Goldstone bosons couple to valence quarks. 18 “Flavor Structure of the Nucleon Sea” W.-C. Chang and J.-C. Peng, arXiv:1406.1260 Prog. in Part. and Nucl. Phys. 79 (2014) 95.
19 Fixed Target Beam lines Tevatro n 800 GeV Main Injector 120 GeV Fermilab E906 Physics data taking: Feb, 2014 – Dec, 2015. 1 H, 2 H, and nuclear targets Unpolarized Drell-Yan using 120 GeV proton beam KEK, RIKEN, Tokyo Tech, Yamagata, AS and U.S. institutes
x+ x- t GPD s P P’ Generalized Parton Distribution (GPD) 20
Accessing GPD using Lepton Beam 21 Deeply Virtual Compton Scattering Deeply Virtual Meson Production JLAB, HERMES@DESY, COMPASS@CERN
Explored Regions of Generalized Parton Distribution (GPD) 22
Spacelike vs. Timelike Processes Muller et al., PRD 86 (2012) 031502 23 Deeply Virtual Meson Production Exclusive Meson-induced Drell-Yan Cross sections of exclusive DY process drop with an increase of beam energy. No sensitivity to parton d.o.f. if beam energy is small. The beam energy of pions at J-PARC at 10-20 GeV might be most ideal for studying this hard exclusive process. Cross sections of exclusive DY process drop with an increase of beam energy. No sensitivity to parton d.o.f. if beam energy is small. The beam energy of pions at J-PARC at 10-20 GeV might be most ideal for studying this hard exclusive process.
24 High-res., High-momentum Beam Line at J-PARC High-intensity secondary Pion beam High-resolution beam: p/p~0.1% Dispersive Focal Point (DFP) p/p~0.1% Collimator 15kW Loss Target (SM) Exp. Target (FF) Pion Beam Up to 20 GeV/c H. Noumi See K. Tanaka’s talk
25 High-res., High-momentum Beam Line High-intensity secondary Pion beam – >1.0 x 10 7 pions/sec @ 20GeV/c High-resolution beam: p/p~0.1% * Sanford-Wang:15 kW Loss on Pt, Acceptance :1.5 msr%, 133.2 m Open a new platform for hadron physics Prod. Angle = 0 deg. (Neg.) KK p bar K+K+ Prod. Angle = 3.1 deg (Pos.) H. Noumi
J-PARC E50 Spectrometer + MuID 26 LH 2 -target Ring Image Cherenkov Counter Internal DC FM magnet ss Fiber tracker Beam GC Internal TOF DC TOF wall 2m Decay p( ) 20 GeV/c Beam Acceptance: ~ 60% for D*, ~80% for decay + Resolution: p/p~0.2% at ~5 GeV/c （ Rigidity ： ~2.1 Tm) | |<60 Scintillator Muon trigger device
20-GeV N + -N M X In E-50 Spectrometer + MuID 27 Red: Exclusive DY ( 5 pb ) Blue: Inclusive DY ( 500 pb ) Green: random BG from meson decay After 200-day data-taking Assumption: Δp/p = 0.2 % Missing Mass M X (GeV 2 ) Nevent The signal of exclusive Drell- Yan processes can be clearly identified in the missing mass spectrum of dimuon pairs. S. Sawada (KEK) S. Kumano (KEK) J.C. Peng (UIUC) T. Sawada (AS) W.C. Chang (AS)
Explored Regions of Generalized Parton Distribution (GPD) 28 J-PARC (exclusive DY)