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General Review of GRAAL physics : Achievements and Future. D. Rebreyend LPSC Grenoble (GRAAL Collaboration) MENU04, 30 August ’04. Outline. GRAAL set-up Meson photoproduction on the proton Eta photoproduction on the neutron HYDILE polarized HD target. Compton Beam. Polarisation. - PowerPoint PPT Presentation
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General Review of GRAAL physics :Achievements and Future
D. Rebreyend LPSC Grenoble
(GRAAL Collaboration)
MENU04, 30 August ’04
D. Rebreyend, MENU04 2
Outline
GRAAL set-up Meson photoproduction on the proton Eta photoproduction on the neutron HYDILE polarized HD target
D. Rebreyend, MENU04 3
Compton Beam
(nm) E(MeV)
514 1100
351 1483
300 1660
Energy Spectrum Polarisation
Simulation
Experiment
EeESRF = 6027.6 0.6
MeV
Linear
Circular
tag~ 10 6 /s
FWHM=16 MeV
Tagged
region
D. Rebreyend, MENU04 4
LAGRANE Detector
1: Compton beam 2: Liquid H2/D2 target
3: BGO Calorimeter 4: Cylindrical MWPC’s
5: Plastic Barrel 6: Plastic Wall
7: Plane MWPC’s 8: Shower Wall
Shower Wall
• neutron efficiency 20 %
• / neutron PID
ToF
E
250
D. Rebreyend, MENU04 5
GRAAL Domain
• E = .6-1.6 GeV/ W=1.4-2 GeV
• Region of second and third resonance
• , K, ’ thresholds
• Complementary of LEGS and LEPS
’ threshold
threshold
K threshold
LEGS/BNL LEPS/SPRING8
E (GeV)
(
b)
threshold
Meson Photoproduction on the proton
D. Rebreyend, MENU04 7
Survey of GRAAL Results Published
+n: from 700 to 1500 MeV (PLB ’00 and ’02) p : and d/d from threshold to 1100 MeV (PRL ’98, PLB ’02)
00p: and d/d from 700 to 1500 MeV (PRL ’03)
Close to completion 0p: and d/d from 700 to 1500 MeV p : extension to 1500 MeV
In progress p : comparison neutral (0 ) / charged decay (+0) K and K
K AnalysisChannel selection
• 3 tracks in MWPC’s
• 2-body kinematical constraints calculation of 3 momenta
• PID by combining calculated momenta with E and/or ToF
important check: vertex reconstruction
p + - K
Distance (primary-secondary) vertices
(No efficiency correction)
Distance (primary-secondary) vertices
(No efficiency correction)
c = 7.6 cm
(PDG: 7.89 cm)
Azi
muth
al dis
trib
uti
on
NH+NV NV-NH/NH+NV
P
Beam Asymmetry
Recoil Polarization (linear polar.)
Px = P Ox sin21 - Pcos2
Py = P - P T cos2/ 1 -
Pcos2
Pz = P Oz sin21 - Pcos2
1.2 GeV
1.4 GeV
1.05 GeV
1.2 GeV
1.4 GeV
1.05 GeV
angular distributionangular distribution
P angular distributionP angular distribution
Good agreement with LEPS
PRL ‘03
d/d = (d/d)0{1 – P cos(2) }
Cross SectionC
ount
s/do
se (
a.u.
)C
ount
s/do
se (
a.u.
)
p K+ p K+
p K+ p K+
SAPHIR data (EPJ ’04)
Eta photoproduction on the neutron
D. Rebreyend, MENU04 12
• SAID analysis : Possible narrow N* at 1680 and/or 1730 MeV
• Polyakov & Rathke (EPJ A18 (03)) :Dominance of photoproduction on the neutron for N10
look for reactions : n N10 n, K0 , K+ -
Recent Motivation Soliton Model anti-decuplet
Non-exotic resonance with a narrow width 10 MeV
D. Rebreyend, MENU04 13
Preliminary Remarks Grenoble analysis (A. Lleres) Studied channels :
d +
n K0 n K+ -
n n (“ easy channel ”) cross section Comparison p p proton target / deuteron target Preliminary results (error bars only statistical) No Fermi momentum correction:
width structure (E)100-130 MeV
No evidence but statistics is too poor for
definite conclusion
D. Rebreyend, MENU04 14
n(p) n(p) Event Selection
• Identical geometrical acceptances for n and p
• Selection of “Quasi-Free kinematics” ??
All final state particles detected: 2 + n (p) proton/neutron detected at forward
angles : lab 250
2 detected in BGO : lab 250
Selection by invariant mass and
2-body kinematical angular correlations no recoil proton/neutron
n / p
D. Rebreyend, MENU04 15
Invariant Mass
p : 0.6 % (taking p= n ) n : 0.3 %
N N : 1-3 %
1.2 % 0.9 %
n n n n p p p p
Simulation
Data
Small background
Background
estimates
D. Rebreyend, MENU04 16
p p Differential Cross Section : Free/Quasi-free
d/
d
(b
/sr)
CM = 1620
Distributions at fixed CM (backward) angles versus E
CM = 1480
CM = 1390
CM = 1230 CM
= 1170
CM = 1300 CM
= 1100 CM = 1040
Clear Discrepancy below 1100 : Data Analysis / Physics ?
not quasi-free reaction close to 1000
D. Rebreyend, MENU04 17
n n Differential Cross Section
• No prominent peak
• Structure at E 1.05 GeV (W 1.7GeV)
• Marked Angular Dependence
d/d (b/sr) at fixed CMd/d (b/sr) at fixed CM
CM = 1540 CM
= 1340
CM = 1200 CM
= 1070
D. Rebreyend, MENU04 18
Comparison QF neutron vs QF proton (1)Ratio QF neutron/QF proton
R=dn/dp at fixed CMR=dn/dp at fixed CM
• Ratio 0.6-0.5 below 900 MeV
(Bonn, R=0.68 PRL ’97)
• Sudden rise around 1 GeV resonance
(Kouznetsov, Moscow seminar, April ’03)
CM = 1540 CM
= 1340
CM = 1200 CM
= 1070
D. Rebreyend, MENU04 19
Comparison QF neutron vs QF proton (2)Integrated Cross Section (p,n 250)
• No “narrow” peak observed in neutron cross section but
shoulder for neutron above 900 MeV
• Rise in difference (neutron-proton) compatible with “narrow” structure
neutron
normalized QFproton
neutron
normalized QFproton*
neutron – C x protonneutron – C x proton
Simulated peak :
W=1.68 GeV, = 10 MeV
Because of Fermi motion :
FWHM = 127 MeV
D. Rebreyend, MENU04 20
Comparison QF neutron/QF proton (3)Integrated ( n) Invariant Mass (p,n 250)
• No peak : compatible with behaviour of d/d
• Spreading due to Fermi motion Resolution
( n) Invariant Mass (GeV)
neutron
normalized proton
neutron
normalized proton*
neutron – C x protonneutron – C x proton
Simulated peak :
W=1.68 GeV, = 10 MeV
Because of resolution :
FWHM = 96 MeV
Num
ber
of e
vent
s
D. Rebreyend, MENU04 21
Beam Asymmetry
See R. Di Salvo’s talk in Parallel Session for more details
n n n n p p p p
Bea
m A
sym
met
ry
HYDILE target
D. Rebreyend, MENU04 23
Operating Principle & Performances Pure HD
good dilution factor (15 % Al)
n and p are polarized
“Relaxation Magnetic Switch” principle (Hoenig ’67)
o-H2 impurities used to polarize (HD weakly coupled to lattice)
o-H2 decays to p-H2 in a few days HD spins decoupled from lattice
relaxation time / 1/ o-H2 concentration
Fabrication process
polarization of HD with static method in a Dilution Refrigerator (17 T, 10 mK)
at Orsay
aging process in DR for 2-3 months 1 T, 1 K
transport from Orsay to Grenoble
Expected performances
polarization : 80 % for p and 20 % for d (50 % with FAP)
relaxation time : 1-2 weeks
Dilution Refrigerator (Orsay)
In-beam + transfert cryostats (Grenoble)
D. Rebreyend, MENU04 25
First run with polarized HD in November 2004
Recent achievements
• Installation of Transfer (TC) and In-beam cryostats (IBC) in Grenoble (10/03)
• Running of IBC during 3 days at 1.5K (11/03)
• First complete and successful transfer of an unpolarized HD sample from Orsay to Grenoble (April 2004)
D. Rebreyend, MENU04 26
Summary
p and K, : results will be released in a “near” future
n n : preliminary results on d/d have been obtained at neutron forward angles ( 250) No prominent peak but structure is observed around W=1.7 GeV
not seen on the proton Extension to all angles foreseen
First data with HYDILE target scheduled in November!!
D. Rebreyend, MENU04 27
Proton Beam Asymmetry
D. Rebreyend, MENU04 28
Neutron Beam Asymmetry
D. Rebreyend, MENU04 29
K0 Analysis
D. Rebreyend, MENU04 30
K0results
D. Rebreyend, MENU04 31
European Synchrotron Radiation Facility
• Circumference : 844 m
• 40 beamlines
• Ee = 6.03 GeV
• Ie = 200 mA
• Bunch structure = 2.8 ns
ESRF parameters
GRENOBLE