PION STRUCTURE FUNCTION AND MORE. Pion signature in experiment: Forward neutrons in DIS Gottfried...
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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
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1
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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
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2
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2
2
31
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2
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Conclusions
Conclusions
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2
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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