symmetries and hadron form factorsbijker/franco70/talks/tomasigusta...egle tomasi-gustafsson irfu,...
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Egle Tomasi-GustafssonIRFU, SPhN-Saclay, and
IN2P3- IPN Orsay France
Symmetries and
Hadron
Form Factors
Egle TOMASI-GUSTAFSSON IFAE, 29-V-2011 1
e-e-
p pe-
e+ p
p
Egle TOMASI-GUSTAFSSON 2
Hadron Electromagnetic Form factors
Cocoyoc, May 15, 2012
•
Characterize the internal structure of a particle (≠ point- like)
•
Elastic form factors contain information on the hadron ground state.
•
In a P- and T-invariant theory, the EM structure of a particle of spin S is defined by 2S+1 form factors.
•
Neutron and proton form factors are different.•
Deuteron: 2 structure functions, but 3 form factors.
•
Playground for theory and experiment•
- at low q2 probe the size of the nucleus,
•
- at high q2 test QCD scaling
IHEP
Cocoyoc, May 15, 20123
The proton vertex is parametrized in terms of FFs: Pauli and Dirac F1
,F2
Electromagnetic InteractionElectromagnetic Interaction
q2<0
e-e-
p p
)2q(2FM2qi
)2q(1Fνμνσ
μγμΓ +=
or in terms of Sachs FFs:GE=F1
-τ F2
, GM=F1
+F2
, τ=- q2/4M2
The electron vertex is known,γμ
The interaction is carried by a virtual photon of mass q2
What about high orderradiative corrections?
Egle TOMASI-GUSTAFSSON
Cocoyoc, May 15, 2012 4
AnalyticityAnalyticity
__
q2<0
e-e-
p p
q2>0
e-
e+ p
p
q2q2=4mp2
FFs are complexFFs are real Unp
hysi
cal r
egio
n
GE=GM
Space-like
Time-likeGE(0)=1
GM(0)=μp
Asymptotics- QCD-
analyticity
p+p ↔ e++e-e+p → e+p
p+p ↔
e++
e- +π
Egle TOMASI-GUSTAFSSON
The polarization method (1967)
Egle TOMASI-GUSTAFSSON 5
The polarization induces a term in the cross section proportional to GE GM
Polarized beam and target orpolarized beam and recoil proton polarization
Cocoyoc, May 15, 2012
Polarization experiments -
JlabA.I. Akhiezer and M.P. Rekalo, 1967
GEp collaboration1)
"standard" dipole function
for the nucleon magnetic FFs GMp
and GMn2) linear deviation
from the dipole function for the electric proton FF Gep
3)
QCD scaling not reached3) Zero crossing of Gep?4) contradiction between
polarized and unpolarized measurements
A.J.R. Puckett et al, PRL (2010)
PRC85 (2012) 045203Cocoyoc, May 15, 2012 6
Egle TOMASI-GUSTAFSSON
Egle TOMASI-GUSTAFSSON 7
Issues•
Some models predicted such behavior before the data appeared
•
Simultaneous description of the four nucleon form factors...•
...in the space-like and in the time-
like regions•
Consequences for the light ions
description•
When pQCD starts to apply?
•
Source of the discrepancy
BUT
Cocoyoc, May 15, 2012
Franco, 1973
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 8
Iachello, Jackson and Landé (1973)
Isoscalar and isovector FFs γ* ω,ρ,ϕ
Egle TOMASI-GUSTAFSSON 9
)2
(GeV2Q0 1 2 3 4 5 6 7 8 9
p*G
Ep
/GM
pμ
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
a
)2
(GeV2Q0 5 10 15 20 25 30
pμG
Mp
/GD
/
0.6
0.7
0.8
0.9
1
1.1
1.2
b
)2
(GeV2Q0.2 0.4 0.6 0.8 1 1.2 1.4
GE
n
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0.11
c
)2
(GeV2Q0 2 4 6 8 10
n/G
Dμ
GM
n/
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
d
The nucleon form factors
VDM : IJLF. Iachello..PLB 43, 191 (1973)
Extended VDM (G.-K. 92): E.L.Lomon PRC 66, 045501 2002)
HohlerNPB 114, 505 (1976)
BostedPRC 51, 409 (1995)
Electric Magneticne
utro
npr
oton
E. T.-G., F. Lacroix, Ch. Duterte, G.I. Gakh,
EPJA (2005)
Cocoyoc, May 15, 2012
Egle TOMASI-GUSTAFSSON 10
Models in T.L. regionE. T-G., F. Lacroix, C. Duterte, G.I. Gakh EPJA 2005
VDM : IJLF. Iachello..PLB43 191 (1973)
Extended VDM (G.-K. 92): E.L.Lomon PRC66 045501(2002)
‘QCD inspired’
proton
neutron
Cocoyoc, May 15, 2012
R. Bijker and F. Iachello, Phys.Rev., C69 (2004) 068201 F. Iachello and Q. Wan, Phys.Rev., C69 (2004) 055204
Egle TOMASI-GUSTAFSSON 11
Models in T.L. Region (polarization)
VDM : IJLExt. VDM
‘QCD inspired’
AngularAsymmetry
Ay Axx Ayy
AxzAzz
E. T-G., F. Lacroix, C. Duterte, G.I. Gakh, EPJA 2005
Cocoyoc, May 15, 2012
R. Bijker and F. Iachello, Phys.Rev., C69 (2004) 068201 F. Iachello and Q. Wan, Phys.Rev., C69 (2004) 055204
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 12
]2 [(GeV/c)2q4 6 8 10 12 14
R0
0.5
1
1.5
2
2.5
3
|GE| and |GM| individual determination up to large q2
PREDICTIONS
R=GE/GMBaBAR
PS170PANDA sim
L = 2x1032 cm-2.s-1, 107 s (~100 days)
]2|[(GeV/c)2|q0 5 10 15 20 25 30
D|/G
p|F
−110
1
10
GM(SL)
BaBarE835FenicePS170E760DM1DM2BES
GE(SL)
GM(TL)
CLEO
PANDASim
Symmetries
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 201214
Crossing SymmetryCrossing SymmetryScattering
and annihilation channels:
-
Described by the same amplitude :
-
function of two kinematical variables, s and
t
k2
→ – k2
-
which scan different kinematical regions
p2
→ – p2
p + p e+ + e- + π0 and e- + p e- + p + π0
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 15
)+
p(p
)−p(p
)π(p0π
(k)*γ
)−(k−e
)+
(k+e
)1
p(p
)π(p0π
(k)*γ
)2
(k−e)1
(k−e
)2
p(p
Described in general by 6 amplitudeswhich depend
on 3 kinematical variables
π + N e+ + e- + Naccess the unphysical region
M. P. Rekalo (1967)
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 16
n(p2)
p̄(−p1)
γ∗(q)
�−(p−)
�+(p+)
π−(qπ)
p2 + p1
n(p2)
p̄(−p1)
π−(qπ)
�−(p−)
�+(p+)
p2 − qπ
γ∗(q)
n(p2)
p̄(−p1) π−(qπ)
γ∗(q)�−(p−)
�+(p+)
−p1 + qπ
(a) (b)
(c)
p + n e+ + e- + π-
Axial
Nucleon FFs
FFs in the unphysical region
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 17
Time-like electromagnetic form factors
IJL pQCD
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 18
C. Adamuscin, E. T-G,E. Santopinto, R. Bijker
DipoleBI
IJL
S=1 form factors
Cocoyoc, May 15, 2012 19
Egle TOMASI-GUSTAFSSON
Egle TOMASI-GUSTAFSSON 20
The IA deuteron structure: S=1, T=0
2) The S (u) and D (w) deuteron wave function
1) The nucleon form factors:
Cocoyoc, May 15, 2012
Deuteron VMD
Meson cloud: isoscalar vector meson only
Normalization
Intrinsic term
C. Adamuscin, G.I. Gakh and E.T-G. PRC 73, 045204 (2006)
Cocoyoc, May 15, 2012 21
Egle TOMASI-GUSTAFSSON
ResultsFrom 12 to 6 parameters fit1) Constrains on the nodes: Q2
0C
=1.7 GeV2, Q20M
=2 GeV2
2) Intrinsic part common to the 3 FFs:
δ=1.04 ±0.03, γ=12.1 ± 0.5
Cocoyoc, May 15, 2012 22
Egle TOMASI-GUSTAFSSON
Results
GCGQ
GM
C. Adamuscin, G.I. Gakh and E.T-G. PRC 73, 045204 (2006)
Cocoyoc, May 15, 2012 23
Egle TOMASI-GUSTAFSSON
e+ + e- → d + d
PRC 74, 025202 (2006)-Imaginary part from the intrinsic term-No finite width for ρ,ω
mesons)
U&A (Dubnicka)
Parametrization I (real part)[Abbott, EPJA 2000]
|GM
|
|GQ
|
|GC
|
Cocoyoc, May 15, 2012 24
Egle TOMASI-GUSTAFSSON
ρ−Meson
Form Factors
Analytical extension : imaginary part from the width (Γ ~ 1% or 10% M)
TL-parametrization:
…no experimental constraints, no new parameterCocoyoc, May 15,
2012 25Egle TOMASI-GUSTAFSSON
A=1, B=0.33 from the node of Gc at q2=-3 GeV2
Fit on light front calculation de Melo and Federico, PRC55,2043 (1997)
Space-like Time-like
ρ -
form factors : Observables
Spin 1
Cocoyoc, May 15, 2012 26
Egle TOMASI-GUSTAFSSON
[n
b/s
r]Ω
/dσd
25
30
35
40
45 (a) σR
0.8
0.85
0.9
0.95
1 (b) xP
-1-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.1
-0 (c)
yP
-0.01
-0.005
0
0.005
0.01(d) z
P
-0.8-0.6-0.4-0.2
-00.20.40.60.8 (e) xx
P
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0 (f)
[deg]θ0 90 180
xzP
-1
-0.5
0
0.5
1(g)
[deg]θ0 90 180
zzP
0.8
1
1.2
1.4
1.6
1.8
2 (h)
[deg]θ0 90 180
yzP
0
0.1
0.2
0.3
0.4
0.5 (i)
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 27
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 28
)2 (GeV2q90 100 110 120
2|F
|
0
0.5
)2 (GeV2q-20 0 20
|G|
-310
-210
-110
1
10
A. Dbeyssi, E.T-G,G.I.Gakh,C.Adamuscin
|GM
|
|GC
||GM
|
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 29
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 30
Tanti Auguri, Franco!
Egle TOMASI-GUSTAFSSON 31
The Rosenbluth separation
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟
⎠
⎞
⎜⎜
⎝
⎛+
+Ω=
Ω)2(2)2(2
)1(1 QMGQEG
Mottdd
dd
ετ
τσσ
2M4
2Q,1
2e2)tan1(21 =
−++=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
⎟⎠⎞
⎜⎝⎛ τ
θτε
2MG2
EGR τεσ +=
→Holds for 1γ exchange only
Linearity of the reduced cross section
PRL 94, 142301 (2005)
→tan2θe dependenceε
Q2
fixed
Cocoyoc, May 15, 2012
From Space-Like to Time-Like
Phenomenological parametrizationsmust include an imaginary part
The sign is important for polarization observables
Cocoyoc, May 15, 2012 32
Egle TOMASI-GUSTAFSSON
SL and TL generalized form factors
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 33
Definition:
space-time distribution of the electric charge in the space-time volume D
In SL-
Breit frame (zero energy transfer):
In TL-(CMS):
: time evolution of the charge distribution in the domain
E.A. Kuraev et al., arXiv:1106.1670
Cocoyoc, May 15, 201234
Time-like observables: | GE | 2 and | GM | 2 .
As in SL region:-
Dependence on q2
contained in FFs-
Even dependence on cos2θ (1γ
exchange)
-
No dependence on sign of FFs-
Enhancement of magnetic term
but TL form factors are complex!
A. Zichichi, S. M. Berman, N. Cabibbo, R. Gatto, Il Nuovo Cimento
XXIV, 170 (1962)B. Bilenkii, C. Giunti, V. Wataghin, Z. Phys. C 59, 475 (1993).G. Gakh, E.T-G., Nucl. Phys. A761,120 (2005).
Egle TOMASI-GUSTAFSSON
Egle TOMASI-GUSTAFSSON 35
The simultaneous measurement of Pt and Pl reducesthe systematic errors
The polarization method (exp)
Cocoyoc, May 15, 2012
C. Perdrisat et al, JLab- GEp collaboration (2000)
JLab, Hall A
Mpp=1.877Mpp=1.877--1.91.9A=0.01A=0.01±±0.020.02
Mpp=2.4Mpp=2.4--33
E. T.-G., E.A. Kuraev, S. Bakmaev, S. Pacetti, Phys. Lett. B (2008)
Cocoyoc, May 15, 201236
Egle TOMASI-GUSTAFSSON
Cocoyoc, May 15, 2012 37
Phragmèn-Lindelöf theorem
Asymptotic properties for analytical functions
E. T-G. and G. Gakh, Eur. Phys. J. A 26, 265 (2005)
Δ=0.05, 0.1
If f(z) →a as z→∞along a straight line, and f(z) →b as z→∞along another straight line, and f(z) is regular and bounded in the angle between, then a=b and f(z) →a
uniformly in the angle.
Egle TOMASI-GUSTAFSSON
The reaction p + p e+ + e- + π0
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 38
font[132]{q}
)+
p(p
)−p(p
)π(p0π
(k)*γV(q)
)−(k−e
)+
(k+e CMS system
γ∗NNπNN
VNN Vπγ∗
Thesis J. Boucher
V=ρ,ω,φ, J/Ψ, ..
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 39
1{g
1γ-2γ interference
2γ1γ
M. P. Rekalo, E. T.-G. and D. Prout, Phys. Rev. C60, 042202 (1999)
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 40
•
Differential cross section at complementary angles:
Symmetry relations (annihilation)
The DIFFERENCE enhances the 2γ contribution:
The SUM cancels the 2γ contribution:
Egle TOMASI-GUSTAFSSON 41
Spin ObservablesAnalyzing power, A
Double spin observables
Cocoyoc, May 15, 2012
The reaction p + p e+ + e- + π0
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 42
γ∗NN
πNN
M. P. Rekalo
Egle TOMASI-GUSTAFSSON Cocoyoc, May 15, 2012 43
STATUS on Time-like EM Form factors
1)
No individual determination of |GE| and |GM|2)
Assume GE=GM
(valid only at threshold)
3)
TL
nucleon FFs are twice larger
than SL
FF
Λ QCD
=0.3 GeV
A(p)
= 56.3 GeV4
A(n)
= 77.15 GeV4
)]/(ln[ 2222 Λ+=
ssAGM π
VMD or pQCD inspired parametrizations (for p and n):
IHEP