Exclusive Vector Mesons at HERA Henri Kowalski DESY DIS 2006 Tsukuba, April 2006
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Transcript of Exclusive Vector Mesons at HERA Henri Kowalski DESY DIS 2006 Tsukuba, April 2006
Exclusive Vector Mesons at HERA
Henri KowalskiDESY
DIS 2006
Tsukuba, April 2006
)2
exp(12*21
0
2*
bddzrdptot
)2/exp(~)(
)exp(~
2 BbbT
tBdt
d diff
GBW - Golec-B, WuesthoffBGBK - Bartels, Golec-B, Kowalski KT - Kowalski, TeaneyKMW - Kowalski, Motyka, Watt
2*1
0
22 |)2
exp(12|16
1*
VM
bip
VM dzebdrddt
d
proton shape
)(),()( 2222
bTxxgrN sC
Glauber Mueller
0)t,(WImAW
1σ 2
el2γptot
Dipole Models equivalent to LO perturbative QCD for small dipoles
x < 10-2
universal rate of rise of all hadronic cross-sections
tottot xWp )/1(~)(~ 2*
Total *p cross-section
6.520
202
2
)1(1
),( xx
Axxg
r
C
g
g
KT
KMW
Inclusive Diffraction-LPS
Dipole cross section determined by fit to F2
simultaneous description of many reactions
F2 C
KT
BGBK
H. Kowalski, L. Motyka, G. Watt
Exclusive Vector Meson Production
Effective modification of Fourier Trans by Bartels, Golec-Biernat, Peters
)1( 2
Real part correction
Skewedness correction Martin, Ryskin Teubner
))2/exp(1(2 2
bd
d)(),()( 222
2
bTRxxgrN gsC
Wave Functions
Boosted Gaussian – NNPZ, FS Gaussian distribution of quark 3-momentum in the meson rest frame
then boosted to LC
Gauss LC - KTGaussian distribution of quark 2-momentum in LC, factorization of r, z components- strong endpoint suppression in T
)2
exp()1(2
),(2
2
2LL
L R
rzz
R
Nzr
)
2exp()1(
2),(
2
222
2TT
T R
rzz
R
Nzr
Parameters of WF fixed by normalization conditions and the values of mesons decay constant, fV
WF Overlaps
Boosted Gaussian - different fV
for T and L
Gaus-LC- different R for T and L
Differences in fV
for Boosted Gaussiansizably smaller thandfferences in R forGaus-LC
Boosted Gaussian more consistentthan Gaus-LC
WF Overlaps integrated over z
KMW
KMW
)2/exp(~)( )exp(~ 2GD
diff
BbbTtBdt
d
KMW
BG BG
))1(( rzbibi ee
Description of the size of interaction region BD
Modification by Bartels, Golec-Biernat, Peters
proton size
KMW
KMW
)2
exp()1()1(2
),(2
2
2,LL
KOMOLT R
rzzzz
R
Nzr
Sensitivity to end points suppression of the wave function
’ ~ 0.1
)(),()( 2222
bTxxgrN sC
))2/exp(1(2 2
bd
d
QCD Evolution within Dipole Sat-Models
DSM with DGLAP (BGBK) + b-dependence (KT, KMW) — b-Sat
DSM with CGC-BFKL (IIM) + b-dependence (KMW+IIM) — b-CGC model
IIM Iancu Itakura Munier
Advantage of b-Sat
Advantage of b-CGC
ρ-meson BD ?
22
12
2
)),(exp()(
SS
s
rQ
ebrbS
Saturation scale (a measure of gluon density) b-frequency
)(),()( 2222
bTRxxgrN gsC
In b-Sat (b-CGC) there are substantial saturation effects in the proton center but only limited part of x-section is in
saturated region
b-independent proton shape?
instead of
J/Psi t-distributions clearly prefer Gaussian proton shape
ρ-meson t-distributions?
Conclusions
we are developing a very good understanding of inclusive and diffractive DIS interactions: F2 , F2
D(3) , F2c , Vector Mesons (J
we obtain a good description of Q2, W and t dependence of and J/ vector meson cross sections with a simple wave function ansatz
HERA measurements suggests presence of Saturation phenomenaSaturation scale determined at HERA, in the proton center,agrees with RHIC
____________________________________________________ Diffractive vector mesons scattering - an excellent probe of nuclear matter, ---- Measure t distribution on polarized nuclei ----- >>>> Obtain holographic picture of nuclei !!!! <<<<<
Possible device: e-RHIC like machine with ~1/3 of HERA energy
Inclusive DIS Hard Diffraction
Optical T
GBW – first Dipole Saturation Model Golec-Biernat, Wuesthoff BGBK – DSM with DGLAP Bartels, Golec-Biernat, Kowalski
IIM - BFKL-CGC motivated ansatz Iancu, Itakura, Munier FS – Regge ansatz with saturation Forshaw and Shaw
....4/))2/exp(1(2 XS Dipole 22
bd
d
Dipole Models equivalent to LO perturbative QCD for small dipoles
Glauber Mueller