The d/u Ratio in Proton Lingyan Zhu HUGS 2009 1 Parton - PowerPoint PPT Presentation

The d/u Ratio in Proton Lingyan Zhu HUGS 2009 1

Parton Distribution Functions 2

The First Traces of Quarks The Nobel Prize in Physics for 1990: A breakthrough in our understanding of the structure of matter 3

The Mysterious Quarks The Nobel Prize in Physics for 2004: David J. Gross, H. David Politzer and Frank Wilczek solved a mystery surrounding strong interaction that quarks sometimes appear to be free in the nucleons though no free quarks have ever been observed. The approximation of free quarks inside nucleon works well in DIS region . 4

PDFs as a function of Bjorken x 5

Lepton DIS One-photon-exchange approximatio n One-photon-exchange approximatio n At ε =1, ∝ F 2 σ ( ) ( ) 1 d = σ + ε σ 2 2 Diff. ∝ F L { x, Q x, Q At ε =0, ∝ F 1 T L Γ Ω d dE' − 1     ν θ 2   ε = + + 2 1 2 1 tan     2 Q 2     ε     + 2 2 σ π α 1 4 M x 2 1 d 4   = + ε p − 2 2 2   2 xF ( x , Q ) F ( x , Q ) 2 xF ( x , Q )   ′ 1 2 1 Γ Ω − 2 2 2 d d E x ( W M ) Q       p σ F L = 2 2 = L 4 M x R = + − F L ( 1 ) F 2 xF σ 2 1 2 xF 2 Q T 1 6

Unpolarized Structure Functions proton—uud neutron--ddu 2 q F 2 =x∑e q xq σ (e,e’)  F 2  q(x) 7

Different Sets of PDFs CTEQ, MRTW/MRST, GJR/GRV, Alekin, ZEUS, H1,…. CTEQ6M Lepton Neutrino Drell-Yan xu(x) xd(x) 8 From HEPDATA online parton distribution calculator.

d/u predictions 9

d/u at x=1 limit SU(6) spin-flavor symmetry: d/u=(1/9+2/9)/(1/2+1/18+1/9)=1/2 The mass difference between N and ∆ implies symmetry breaking S=0 diquark dominance d/u=(0)/(1/2)=0 Hyperfine-perturbed quark model (Isgur at al .) with one-gluon- exchange; MIT bag model with gluon exchange (Close & Thomas ); Phenomilogical quark-diquark(Close) and Regge (Carlitz) arguments S z =0 diquark dominance d/u=(1/9)/(1/2+1/18)=1/5 pQCD with helicity conservation (Farrar and Jackson); quark counting rule ( Brodsky et al.) Others: 10 Diquark model(Close & Roberts)

d/u in proton subject to big nuclear correction Charge symmetry: u in proton = d in neutron 11 From BONUS proposal

Deuteron/Nucleon Ratios From Wally Melnitchouk Various nuclear models Various wave functions 12

Nuclear Corrections 13

Nuclear effects in A/D ratios Gomez et al., PRD49(1994)4348 SLAC E139 at x=0.6 Shadowing….Anti-shadowing…EMC effect E139 (Fe) EMC (Cu) BCDMS (Fe) 14

Recent Jlab results on EMC effects of light nuclei Seely et al, arXiv:0904.4448 15

Drell-Yan & DIS T JLab User’s Group Meeting 16

A/D ratio in Drell-Yan Alde et al (Fermilab E772) Phys. Rev. Lett. 64 2479 (1990) No clear anti-shadowing region 17

(anti-)neutrino DIS y= ν /E d l + u l - W - W + ν u ν d 18

Neutrino NuTeV vs. Drell-Yan E866 Owens et al ., PRD75(2007)054030 Neutrino NuTeV has different Pull of the PDFs at large x from E866. 19

EMC for neutrino experiment Schienbein et al ., PRD77(2008)054013 neutrino+iron anti-neutrino+iron d u l + l - W - W + ν u ν d 20

JLab d/u experiments 21

Select kinematics with small nuclear correction Binding Effects BoNuS Region “BoNuS” VIPs 0.07 0.2 GeV/c Final State Interactions 22

BONUS at 6 GeV 23

BONUS: radial TPC using cylndrical GEMs 140 μm Gas Electron Multiplier Window Cathode Drift Region Helium/DME at 80/20 ratio Time Projection Chamber 3 GEMs Readout pads and electronics 24

Improvement of resolution with tagged proton E = 4.223 GeV 2 = p n 2 = D − E s ) ν − r p n ⋅ r µ p n µ + 2 ( M ( ) ( ) − Q p n + q 2 W q 2 + 2 M ν ( 2 − α S ) − Q ≈ M * 2 W 2 = M 2 + 2 M ν − Q 2 € 25

6 GeV BONUS preliminary From Kuhn’s talk at DIS09 W > 1.6 GeV W > 1.9 GeV Q 2 > 2 GeV 2 Q 2 > 1 GeV 2 Wait for the Jlab upgrade to get to higher x . 26

JLab 12 GeV d/u with Bonus detector BONUS 27

JLab 12 GeV d/u with Helium/trillium target based on nuclear models; close to 1 28

Hydrogen Alone d/u 29

(anti-)neutrino cross section on hydrogen 30

WA21: (anti-)neutrino on hydrogen Jones et al , Z. Phys. C44(1989)379 31

Valence quark from WA21 Sterman et al , Rev. Mod. Phys. 67(1995)157 xu v xd v 32

NUMI beam line Most powerful ν beamline so far in the world. 4X10 20 protons/year Configurable beam Wide range of ν energies Neutrino and anti-neutrino 33

Neutrino Beam Components Combo beam: 1 year LE+3 year ME; 4.0 x 10 20 POT per year 34

MINERVA experiment Cryotarget LHe LHe LH2 Position determined by charge sharing Particle 35

Module Construction Tracker module Typical module: • has 302 scintillator channels • weighs 3,000 lbs • 3 types of modules Full detector: • 108 modules; ~30K channe ls. HCAL module include 1” steel absorber ECAL module incorporate Pb absorber 3 strip orientations 36

Projection with NUMI ME (anti-)neutrino beam 37

Empty Taret Background neutrino beam: Al/H=6.7 anti-neutrino beam: Al/H=3.5 d u W - l + l - W + ν ν d u 38

Projection with NUMI HE (anti-)neutrino beam 39

Summaries d/u is very important for us to understand the proton structure. The comparison with calculation at x=1 limit can provide very useful information about SU(6) sysmmetry breaking. The better knowledge with d/u can help constrain gluon distribution within a global parameterization of the PDFs. The nuclear corrections are not well stood. There is no unique thoery/model that can explain the well measured EMC effect in A/D ratio. The recent data from JLab with light nuclei suggest that the quark distribution may depend on the local nuclear environment. The nuclear corrections may affect PDF extraction based on to the (anti-)neutrino data with nuclear targets. The nuclear corrections for deuteron may be big for d/u at large x. BONUS and A=3 Trillium/Helium experiments were proposed to reduce the nuclear corrections at JLab. But the ultimiate way to avoid nuclear correction is to use hydrogen target alone, with neutrino and anti-neutrino beam. This is possible with Minerva experiment at Fermilab. 40