PION STRUCTURE FUNCTION AND MORE

Pion signature in experiment:

Forward neutrons in DIS

Gottfried Sum rule

•Forward Neutron Calorimeters at H1 and ZEUS at DESY

A.Bunyatyan “Physics with FNC”

FNC – design specifications

The size and weight of FNC is defined by the space available in HERA tunnel •position– 105m from the interaction point, size ~ 70 x 70 x 200cm3 , weight <10t•geometrical acceptance is limited by beam-line elements <0.8mrad•should work in high radiation environment

Pion signature

H1 detector at HERA collider

A.Bunyatyan “Physics with FNC”

A.Bunyatyan “Physics with FNC”

The H1-FNC energy response

CERN test-beam Ebeam=120-350 GeV

A.Bunyatyan “Physics with FNC”

Neutron and photon energy spectrum measured in H1

-cluster in Preshower = photon, -cluster in main calorimeter and/or Preshower = neutron

Different pion fluxes used in analysis (different form factors)

A.Bunyatyan “Physics with FNC”

Data

Rapgap-MC Rapgap-MC after tuning

Acceptance determined by MC

H1 Publications:• “Measurement of leading proton and neutron production in DIS at HERA” DESY-98-169

• “Measurement of dijet cross sections in ep interactions with a leading neutron “, DESY-04-247

ZEUS Publications:• “Study of the pion trajectory in the photoproduction of leading neutrons at HERA” DESY-04-037 • “Photoproduction of D* mesons associated with a leading neutron”” DESY-03-221 • “Leading neutron production in ep collisions at HERA” DESY-02-039 • “Measurement of dijet cross sections for events with a leading neutron in photoproduction at HERA” DESY 00-142 • “Observation of events with an energetic forward neutron in DIS at HERA” DESY 96-093

A.Bunyatyan “Physics with FNC”

F2 from ZEUS

A.Bunyatyan “Physics with FNC”

Data show sensitivity to the parameterizations of the pion structure function (constrained for x (=)>0.1 from the fixed target experiments).

F2LN(3) (z=0.7)

X

A.Bunyatyan “Physics with FNC”

Comparison of LN production rate for different processes (ZEUS)

e.g. rp < rjj < rD* ≤ rDIS

Absorption - ratio depends on the transverse size of virtual photon

01.025.0

01.018.0

01.016.03

2 2

pnPn

Pion signature

Estimation of the probability of the p→n++ in DIS

from the neutron rate in DIS extrapolating to the full

energy range (for three different pion fluxes}

DIS on Proton and Deuteron

Pion signature

NMC detector at CERNDeep inelastic scattering of muons off protons and deuterons

Pion signature

Gottfried sum rule

3

1)

9

1

9

1

9

4()

9

1

9

4

9

4(

3

1)(

.),(.),(

22

2222

np

npG

vi

FFx

dxS

seadxxQqzdxxQFx

dx

0 seadx for flavour symmetric sea

Pion signature

026.0235.0but 3

1 GG SS

Pion signature

Interpretation

02.020.0

2

2

2

31

2

2

31

20

2

0

0

a

auuaud

da

uadad

ua

dauau

Conclusions

Conclusions

332333

2

2

31

32

0

qPqPqPqp

ua

dauau

NNN

Conclusions

The constituent quarks are a superposition of the massive quarks and pions

Spontaneous breaking of the chiral symmetry

and fossil pions

Chiral symmetry breaking

• Nambu-Jona-Lasinio Model

]))()[( .( 25

2 iGidxH

Chiral symmetry breaking

22222

cMpc

MNG

c

AM

Chiral symmetry breaking

0m

Conclusions

Gluonic structure of the nucleon-

resolution on the order of 0.3 fm

d

u

u

d

u

d

d

u

Conclusions

Microscopic view of the chiral symmetry breaking

The interaction that is responsible for giving the mass to

quarks binds quark-antiquark to a pion

Chiral symmetry breaking

AP

P

1 1

2McA

Chiral symmetry breaking

• Nambu-Jona-Lasinio Model in Cartoons

ip

P

1

iMccp

2

1