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

The d/u Ratio in Proton

1

HUGS 2009

Lingyan Zhu

Parton Distribution Functions

2

The First Traces of Quarks

3

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

The Mysterious Quarks

4

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

• bserved.

The approximation of free quarks inside nucleon works well in DIS region.

PDFs as a function of Bjorken x

5

Lepton DIS

6

One-photon-exchange approximatio One-photon-exchange approximation

n

At ε =0, ∝ F1

• Diff. ∝ FL {

At ε =1, ∝ F2

                − + + − = ′ Ω Γ

) , ( 2 ) , ( 4 1 ) , ( 2 ) ( 4 1

2 1 2 2 2 2 2 2 1 2 2 2

Q x xF Q x F Q x M Q x xF M W x E d d d

p p

ε α π σ

1 2 2 2 2

2 ) 4 1 ( xF F Q x M FL

− + =

1

2xF F R

L T L =

= σ σ ε

( ) ( )

2 L 2 T

Q x, Q x, dE' d d 1

ε σ σ σ + = Ω Γ

1 2 2 2

2 tan 1 2 1

−

              + + = θ ν ε

Q

Unpolarized Structure Functions

7

xq F2=x∑eq

2q

σ(e,e’)F2q(x)

proton—uud neutron--ddu

CTEQ6M

Different Sets of PDFs

8

CTEQ, MRTW/MRST, GJR/GRV, Alekin, ZEUS, H1,….

xu(x) xd(x)

Lepton Neutrino Drell-Yan 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 Sz=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:

Diquark model(Close & Roberts)

10

d/u in proton subject to big nuclear correction

11

Charge symmetry: u in proton = d in neutron From BONUS proposal

Deuteron/Nucleon Ratios

12

From Wally Melnitchouk Various wave functions Various nuclear models

Nuclear Corrections

13

Nuclear effects in A/D ratios

14

SLAC E139 at x=0.6

E139 (Fe) EMC (Cu) BCDMS (Fe)

Shadowing….Anti-shadowing…EMC effect Gomez et al., PRD49(1994)4348

Recent Jlab results on EMC effects of light nuclei

15

Seely et al, arXiv:0904.4448

Drell-Yan & DIS

JLab User’s Group Meeting 16

T

A/D ratio in Drell-Yan

17

Alde et al (Fermilab E772) Phys. Rev. Lett. 64 2479 (1990) No clear anti-shadowing region

(anti-)neutrino DIS

18

ν

l-

d u W+ W-

l+

d u ν

y=ν/E

Neutrino NuTeV vs. Drell-Yan E866

19

Neutrino NuTeV has different Pull of the PDFs at large x from E866.

Owens et al., PRD75(2007)054030

EMC for neutrino experiment

20

neutrino+iron anti-neutrino+iron

ν

l-

d u W+ W-

l+

d u ν Schienbein et al., PRD77(2008)054013

JLab d/u experiments

21

Select kinematics with small nuclear correction

22

Final State Interactions “BoNuS” Binding Effects

BoNuS Region

VIPs

0.07 0.2 GeV/c

BONUS at 6 GeV

23

Readout pads and electronics

24

BONUS: radial TPC using cylndrical GEMs

Gas Electron Multiplier

140 μm Helium/DME at 80/20 ratio

Drift Region

3 GEMs

Cathode Window Time Projection Chamber

Improvement of resolution with tagged proton

25

E = 4.223 GeV

W

2 =

p n + q

( )

2 = p n

µ p n µ + 2 ( M

D − E s )ν − r

p n ⋅ r q

( )− Q

2

≈ M *

2 +2 M ν ( 2 − α S ) − Q 2

€

W 2 =M2+ 2Mν− Q2

6 GeV BONUS preliminary

26

W > 1.9 GeV Q2 > 1 GeV2 W > 1.6 GeV Q2 > 2 GeV2

Wait for the Jlab upgrade to get to higher x. From Kuhn’s talk at DIS09

27

BONUS

JLab 12 GeV d/u with Bonus detector

28

JLab 12 GeV d/u with Helium/trillium target

based on nuclear models; close to 1

Hydrogen Alone d/u

29

30

(anti-)neutrino cross section on hydrogen

WA21: (anti-)neutrino on hydrogen

31

Jones et al, Z. Phys. C44(1989)379

Valence quark from WA21

32

Sterman et al, Rev. Mod. Phys. 67(1995)157

xuv xdv

NUMI beam line

33

Most powerful ν beamline so far in the world. 4X1020 protons/year Configurable beam Wide range of ν energies Neutrino and anti-neutrino

Neutrino Beam Components

34

Combo beam: 1 year LE+3 year ME; 4.0 x 1020 POT per year

MINERVA experiment

35

LHe

Cryotarget

LHe

Position determined by charge sharing

Particle

LH2

Module Construction

36

Typical module:

• has 302 scintillator channels
• weighs 3,000 lbs
• 3 types of modules

Full detector:

• 108 modules; ~30K channels.

Tracker module ECAL module incorporate Pb absorber HCAL module include 1” steel absorber 3 strip orientations

Projection with NUMI ME (anti-)neutrino beam

37

Empty Taret Background

38

ν

l-

d u W+ W-

l+

d u ν neutrino beam: Al/H=6.7 anti-neutrino beam: Al/H=3.5

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