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Workshop on the Physics of Excited Nucleon – NSTAR 2009, Beijing. Latest results from GRAAL collaboration presented by Valentina Vegna on behalf of the GRAAL Collaboration Università degli Studi di Roma “Tor Vergata” and INFN Sezione di Roma Tor Vergata. the GRAAL experimental set-up; - PowerPoint PPT Presentation
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Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Latest results from GRAAL collaborationpresented by
Valentina Vegnaon behalf of the GRAAL Collaboration
Università degli Studi di Roma “Tor Vergata” and INFN Sezione di Roma Tor Vergata
Workshop on the Physics of Excited Nucleon – NSTAR 2009, Beijing
the GRAAL experimental set-up; and 0 photoproduction on quasi-free neutron; K+ and K+0 photoproduction on free proton; in memoriam of Eid Hourany.
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Meson Photoproduction at GRAAL
(b
)
GRAAL/ESRF
E (GeV)
threshold
K threshold
’ threshold
Beam Asymmetry Measurements for accessible
reactions:
• polarized photon beam;
• large acceptance apparatus;
• tagged photon beam.
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
GRAAL Polarized and Tagged Photon Beam
e-
e-
Ee,me
E’e, me
E
EL
L
16 MeV FWHM
Ee= 6 GeV
EL= 2.41 eV (green line, = 514 nm)
EL= 3.53 eV (U.V. line, = 351 nm)
Emax= 1.1 GeV
Emax= 1.5 GeV
green line
UV line
Tagger Energy Spectrum Energy Resolution
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
GRAAL Detector
Photon detection (energy resolution 3% FWHM at 1 GeV); Charged particle identification (protons - pions); Energy measurement for protons; Neutron detection (and energy measurement in forward direction).
NOT IN SCALE
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Measurement at GRAAL
))cos(2P(121
/KN/KN/KN
HHVV
VV
Experimental Distribution at fixed E and m
CM: )cos(2 PΣ 1ε kN VH,VH,
pnpn
kp pnpn 0
deg0
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Photoproduction on Quasi-Free Nucleon in Deuteron npnp
pnpn
Preselection:
2 neutral cluster detected in BGO (invariant mass (0.35-0.7) GeV/c2);
1 neutron or 1 proton (in the central or in the forward detectors);
no other particles.
1
Kinematic Analysis:
• Two-body nature of each reaction step:
2
miss
calc
calcN
measN
measN
measmeasmeas
M
EE
E
Selection cuts:
•
•
3
180 measmeasN
calcN
measN vs
Nmissmeascalc MMvsEE
A.Fantini et al., Phys.Rev.C 78, 015203 (2008)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
in Photoproduction on qfp and fp
qfp
fp
MAID2001 - fp
reggeized model - qfp
MAID2001 - qfp
• at low energies: dependence
• with increasing energy: forward-backward asymmetry
CM
2sin 152013D
167015F
A.Fantini et al., Phys.Rev.C 78, 015203 (2008)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
in Photoproduction on qfn
qfn
reggeized model
MAID2001
GeVE 9.0
GeVEGeV 25.19.0
EGeV 25.1
: symmetric behaviour
: symmetric behaviour
: peak in forward direction
167515D
A.Fantini et al., Phys.Rev.C 78, 015203 (2008)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
up to 1.05 GeV: qfn quite close to qfn;
above 1.05 GeV:• P11(1670);• S11(1650)-P11(1710).
qfnqfp
in Photoproduction on qfp and qfnA.Fantini et al., Phys.Rev.C 78, 015203 (2008)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
0 Photoproduction on Quasi-Free Nucleon in Deuteron npnp 0
pnpn 0
Pre-selection:
2 neutral cluster detected in BGO (invariant mass (0.09-0.20) GeV/c2);
1 neutron or 1 proton (in the central or in the forward detectors);
no other particles (quasi-free kine).
1
Kinematical Analysis:
• Two-body nature of each reaction step:
2
miss
calc
calcN
measN
measN
measmeasmeas
M
EE
E
0
0000
Selection cuts:
•
•
3
180 0measmeas
NcalcN
measN vs
000 miss to π
meascalc MvsEE
R. Di Salvo, to be submitted
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
in 0 Photoproduction on qfp and fpR. Di Salvo, to be submitted
fpqfp
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
in 0 Photoproduction on qfnR. Di Salvo, to be submitted
qfn
MAID2007
MAID2007 new
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
in 0 Photoproduction on qfnMultipole extraction in MAID2007
MAID2007 qfn
mod MAID2007 qfn
170011P
1.0
70
MeVtot
172013P
Real partImmaginary part
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
in 0 Photoproduction on qfp and qfnR. Di Salvo, to be submitted
qfnqfp
MAID2007 “new” for neutron
MAID2007 “new” for proton
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
K+ and K+0 Photoproduction on Free Proton pKKp
pKKKp 0
Kinematic Analysis:
• Three-body kinematics;
• Two-body nature of each reaction step;
Check: decay length
Preselection:
3 tracks + at most 1 neutral cluster detected in BGO (no neutral particle: K+; 1 neutral particle: K+0)
Kp
p
0 Kp
0
p
Selection cuts:
• Energy balance;
• Charged particles mass;
• Missing mass ;
• Energy of the from decay.
Kpm
1
2
3
4
A.Lleres et al., EPJ A 31, 79-93 (2007)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
in K+ and K+0 Photoproduction
GRAALGhent Isobar
SaclayBonn coupled
channel
GRAAL
Published Bonn coupled channel
New Bonn coupled channel
A.Lleres et al., EPJ A 31, 79-93 (2007)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
GRAAL
CLAS
Ghent Isobar
Saclay
Bonn coupled
channel
P in K+ PhotoproductionA.Lleres et al., EPJ A 31, 79-93 (2007)
0cos0cos
0cos0cos2
pp
pp
NN
NNP
013.0642.0
• Saclay Model:
170011S 180013P 185013D
• Ghent Isobar Model: 190013D
• Reggeized Model:
190013P 190013D
• Bonn Coupled Channel Model:
187513D
From and P measurements:
pp PW cos12
1cos
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Formalism for Recoil Observables in K+ Photoproduction
]2sin2cos2sin2cos1[2
1'''
0 zzyxxf OPTPPOPP
d
d
d
d
2cos1
2sin,','
P
OPP zxzx
2cos1
2cos'
P
TPPP y
S1
S1
S2S2 S4
S4 S3
S3
<Py’
>S1 S2
lab=0°
lab=90°
P
TPP
2
2
P
TPP
2
2
P
TPP
2
2
P
TPP
2
2
<Px’,z’
>S3 S4
lab=0°
lab=90°
zxOP ,2
zxOP ,2
zxOP ,2
zxOP ,2
',',',' cos2
12
1cos zx
pzxzx
p
OPW
',',','','0
',' cos2
1cos2
1 zxp
zxzxp
zxzx OPNN
'''
0' cos
2
21cos
2
1 yp
yp
yy
P
TPPNN
pp PW cos12
1cos
'' cos
2
21
2
1cos y
pyp P
TPPW
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Double Polarization Observables in K+ PhotoproductionA.Lleres et al., EPJ A 39, 149-161 (2009)
GRAALGI RPRBonn Gatchina
GRAALGI RPRBonn Gatchina
'''
'
cos2
12 x
px
xx
x OP
NN
N
'''
'
cos2
12 z
pz
zz
z OP
NN
N
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
T in K+ Photoproduction
GRAALGI RPRBonn Gatchina
From Ox, Oz and T extractions:
• Ghent Isobar RPR Model:
165011S 171011P 172013P
190013P 190013D
• Bonn Gatchina Model:
153511S 165011S 172013P 184011P
190013P
'
'
''
'
cos1
cos2
21
21
2yp
yp
yy
y
P
P
TPP
P
NN
N
A.Lleres et al., EPJ A 39, 149-161 (2009)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Comparison with CLAS
PTOCOC zxxz
22222221 zxzx CCPOOT A.Lleres et al., EPJ A 39, 149-161 (2009)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Conclusions• photoproduction on nucleon:
measurement of in the energy range from 0.7 to 1.5 GeV;
qfp is similar to fp: it suggests that qfn is similar to fn;
the energy dependence of qfp and qfn is very similar up to 1.05 GeV;
above 1.05 GeV, qfp is forward peaked while qfn looks more symmetric around CM = 90°;
above 1.05 GeV and backward angles, qfn is substantially higher than qfp;
• 0 photoproduction on nucleon:
measurement of in the energy range from 0.5 to 1.5 GeV;
qfpis similar to fp : it suggests that qfn is similar to fn;
qfp and qfn are very similar for low values of 0* but differ a lot with increasing of
0*;
• K+ photoproduction:
systematic measurements of , P, Ox, Oz and T in the energy range from 0.9 to 1.5 GeV;
comparisons with 4 different models confirm the necessity to introduce new or poorly known resonances in the 1900 MeV mass region: P13and/or D13;
we need only one additional double-polarization observable to extract helicity amplitudes.
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
In memory of Dr. Eid Hourany
Dr Eid HOURANY died in October 2008 at the age of 67.
He had been involved as the leader of the Orsay team in the GRAAL venture since the beginning and constructed the scintillating wall of the GRAAL detection system.
He has been a talented experimentalist able to analyse complex data. In the last few years, he has analyzed almost alone, « exotic » final states as: Nπ0π0, Nπ0η, Nω and extracted from the GRAAL data very innovative information.
The quality of the GRAAL physics production is largely indebted to his constantly demanding attitude.
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Double 0 photoproduction
P.R.L. 90 (2003) Phys.Lett.B 651 (2007)
...on the proton ...on the neutron
1520D
1440P
13
11
1700D
1710P
13
11
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
photoproduction on the proton
P.R.L. 96 (2006)
1680F 1720P 1520D 151313
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Simultaneous and 0 photoproduction
P.R.L. 100 (2008)
3-body phase space
Döring, Oset,Strottman (2006)
ηpS ,Sπpγ 11110
pπΔ ηΔ,pγ 0
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Thanks a lotfor your attention
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
0 Photoproduction: Re-calculation of 0 C.M.
R. Di Salvo, to be submitted
FPP
Deviation of the Lorentz Boost Axis
PPPP extr
NF 0 Re-calculation of 0 C.M.
EMEE NextrN
22
NextrN
extrN MEP
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Photoproduction: Selected EventsFantini et al., Phys.Rev.C 78, 015203 (2008)
proton neutronce
ntr
al re
gio
nfo
rward
regio
n
Proton Neutron
Centre 2.4% 3.9%
Forward 0.9% 1.4%
Total exstimated background
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Photoproduction: CheckFantini et al., Phys.Rev.C 78, 015203 (2008)
Check on the validity of:
3-parameters fit:
Similiar results for beam asymmetry;
Higer 2;
The quality of fits gets worse.
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
P0 in K+0 Photoproduction
pKKKp 0
uuPP
0
u , unity vector along the direction of emission in the 0 rest frame
0
3
1 PP
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
K+ Photoproduction : Efficiency Dependence for N+ and N-
Lleres et al., EPJ A 31, 79-93 (2007)
via Monte Carlo simulation
'' coscos xp
xp
sel
xx
x
gen
xx
x
NNN
NNN
Cor
''
'
''
' 22
Detection efficiencies and correction factors depend on the input values of Ox , Oz and T: iterative method (3 iterations).
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Internal Check
1PT
11
1
1
2222
222
222
zx
zx
zx
OOPT
OO
OOPA.Lleres et al., EPJ A 39, 149-161 (2009)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Photoproduction: theoretical models for comparisonsFantini et al., Phys.Rev.C 78, 015203 (2008)
Beijing, 19-22 April 2009 NSTAR 2009 Valentina Vegna
Models in K photoproduction off free protonsSACLAY G.I.
GRPR
BCC