The dbar/ubar Ratio in Proton

Transcription

1 The dbar/bar Ratio in Proton Lingyan Zh HUGS

2 What s the expection with dbar and bar? Peng & Garvey, Prog.Part.Ncl.Phys.47(2001)203 [+sbar]: MeV K0[d+sbar]: MeV π+[+dbar]: MeV SU(2) symmetry 2

3 Sea Asymmetry from DIS 4 1 F / x = ( + ) + (d n F2 / x = (d + d ) + ( p n [ F2 F2 ] / x = ( + ) 3 p 2 proton[d] = = > 1 [ 0 v 1 d ) + (s + s ) 9 1 ) + (s + s ) 9 1 (d + d ) 3 d v ]dx = [ F2p F2n ] / xdx 0 2 [d ]dx = * = = Gottfried Integral SG=1/3? NMC at CERN: PRL66(1991)2712;PRD50(1994)R1 3

4 Sea Asymmetry from Drell-Yan Towell et al., Phys.Rev. D64 (2001)

5 Sea Asymmetry from Models Prog.Part.Ncl.Phys.47(2001)203 Pion clod models:bare ncleon +pion clod π N Phys.Rev.D59(1999) Chiral Models: Constitent qarks + Goldstone Bosons More: Instanton Models, Lattice Gage Approach, Chiral-Qark Soliton Model 5

6 Flavor Decomposition in Semi-Inclsive DIS 1 dσ ( ep hx ) = σ dz q eq2 f q ( x ) Dqh ( z ) q eq2 f q ( x) f q ( x ) : parton distribtion fnction Dqh ( z ) : fragmentation fncti on z = Eπ /ν Unfavored fragmentaion D- π (d ) or d π + (d ) Favored fragmentation D+ π + (d ) or d π (d ) 6

7 Fragmentation Fnctions Normally two jets: q h or qbar h e+e- hx constrains D++D7

8 Semi-Inclsive DIS, D. Boer R. Jakob, and P.J. Mlders, NPB564, 471 (2000) [hep-ph/ ]. Boer-Mlders Transversity/Collins Sivers Long. Polarized PDF Unpolarized Polarized target Polarized beam and target 8

9 HERMES at DESY DESY-Hambrg: 27 GeV e+/ GeV p 9

10 Factorization Check at HERMES 10

11 Sea Asymmetry from HERMES 11

12 Jefferson Lab (JLab) 6 GeV polarized CW electron beam (P = 85%, I = 180 ma) 3 halls for fixed target experiments Hall A: 2 high resoltion spectrometers +BigBite Hall B: large acceptance spectrometer Hall C: 2 spectrometers 12

13 Factorization Check at JLab H(e,e π+/-) from JLab E00108: PRL98(2007) [hep-ph/ ] 1,2 Data beyond Δ region are well described by LO SIDIS ansatz. 13

14 Sea Asymmetry Measrement at JLAB L.Y.Zh, J.P.Chen, X. Jiang and J.C. Peng, JLab Hall A PR

15 Flavor Asymmetry in Kaons? + Is d sea ( x) = sea ( x) in K? Difficlt to measre sea qark distribtions in! Can the / d flavor asymmetry be observed i n the kaon fragmentation fnctions? d Is D ( z ) > D ( z )? 15

16 Unpolarized Kaon SIDIS The semi-inclsive prodction of charged kaons from proton and netron target K = D D + d K d s, D DK = DK, Y p Y K p YnK + K n Y [ [4D [4dD [4dD 4D = D D s + sd = D + d K d DsK = DsK = D + 4 D = D s + sd + (d + d ) D + sd + s DsK + 4d DK + sdsk + ( + ) DdK + 4 D s d s K s + sd d + (d + d ) D s s d + sd + 4d D + sd + ( + ) D ]/ 9 ]/ 9 ]/ 9 ]/ 9 16

17 Kaon Fragmentation Fnction Ratio If at large x ignoring strange qark contribtion, DK + d D D [ s ] > > DK + [ s ] d 2D D + D = + K d + K D D + = 4 d+ + d+ + YpK ) + (YnK + YnK ) (YpK + d (Yp + YpK ) > 1? d (Yn + YnK ) Projection for JLab Hall A PR

18 SIDIS Coverage With JLab Upgrade From Hart Avakian 27 Ge V HERA EIC ) ed d gra p ( b es L6aGeV m J r b@ he JLa co mp as s Q2 Higher beam energy provide larger phase space. 18

19 Sea Asymmetry with JLAB Upgrade H. Gao, A.Brell, H.Mkrchyan, J.P.Chen&L.Y.Zh, JLab Proposal PR

20 Sea Asymmetry with 120 GeV Proton Beam Fermilab E866/NSea (M. Leitch) Data in GeV proton beam Fermilab E906 (D. Geesaman, P. E. Reimer) Data in GeV proton Beam et g r Ta nes d e li Fix eam B Main Injector 120 GeV Tevatron 800 GeV Cross section scales as 1/s Backgronds, primarily J/ψ decays drop with s E789,PRD52(1995) x statistics!! 20

21 Fermilab E906 Drell-Yan timeline Expt. Fnded Experiment Rns Magnet Design Experiment And constrction Constrction Proposed Jan : approved by Fermilab PAC 2006: reaffirmed by Fermilab PAC Fnding reqest to DOE: ~$2M primarily for the magnets. Pblications 21

22 Drell-Yan & DIS Error Propagation 22

23 (anti-)netrino cross section on hydrogen 23

24 Minerva experiment with hydrogen At x>0.3, (dbar+sbar)/(bar+cbar) have similar slope as dbar/bar. 24

25 W prodction with proton beam 25

26 W asymmetry Yang et al., arxiv: RHIC: p+p center-of-mass energy at 500 GeV LHC: p+p center-of-mass energy at 14 TeV 26

27 W asymmetry measrement at RHIC and LHC Yang et al., arxiv: RHIC PHENIC: p+p center-of-mass energy at 500 GeV LHC CMS: p+p center-of-mass energy at 14 TeV 27

28 Smmary The bar and dbar asymmetry is large in the proton sea, with dbar/bar arond 2 at x=0.2. No model can explain the drop of this ratio at higher x observed in Drell-Yan process. Recent data has shown the LO factorization in Semi-inclsive DIS in HERMES and even JLab. The SIDIS was sed to check the bar and dbar sea asymmetry in proton, bt the ncertainties can be greatly redced at JLab especially with the energy pgrde. SIDIS can be also sed to probe other parton distribtion fnctions and fragmentation fnctions inclding thetransverse-momentmdependent parton distribtion fnctions. (Anti-)netrino DIS on hydrogen target or W prodction with p+p collision may provide a way to measre the sea asymmetry withot any nclear correction and any charge symmetry assmption. 28

29 CTEQ inpts 29

30 Drell-Yan Cross Sections & Global PDF E866(J.C.Webb et al.), hep-ex/