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A-dependence of deuteron
knock out from light nuclei
by intermediate energy pions
B.M.Abramov, Yu.A.Borodin,
S.A.Bulychjov, I.A.Dukhovskoy,
A.I.Khanov, A.P.Krutenkova,
V.V.Kulikov, M.A.Martemianov,
M.A.Matsyuk, V.E.Tarasov,
E.N.Turdakina.
ITEP, Moscow
A(π --, d π -- )X
A= Li-6, Li-7, C-12, O-16 0.7, 0.9 and 1.3 GeV/c
Motivation for deuteron and triton knock out study
1. Reaction mechanism.2. Nuclear structure: nucleon-nucleon correlations, clustering properties etc.3. Possible modification of deuteron properties in nuclear media.4. Different projectiles are disirable to have a full picture of nuclear fragment knock out processes. Data exist on proton, electron and photon beams but not on a pion beam.5. High energy and large momentum transfer are important to minimize distortion6. Clustering aspects of Li isotopes
Main problems of deuteron knock out experiments with pion beam.
1. An intensity of pion beams is smaller than that of proton.
2. Cross secion for the backward pion deuteron elastic scattering is less by two oders of magnitude than cross section for backward
proton deuteron elastic scattering.
3. Non favourable kinematics and large additional pion production in pion beam make it impossible to observe the peak of quasielastic scattering without detection of scattered pion.
p+A->d+X, 660 MeV, L.S.Azhgirei ..(JINR)
π+A->d+X, 0.7 GeV/c, B.M.Abramov ..(ITEP)
ITEP 3-meter magnet spectrometer
Trigger ~100 PM FEY-60, 85, 30, 63
d: - ->d- B= (H1·C2·C3)·(antiC5)
B·(H5·H2·H3)·(C7+H4) ·(C2·H3)td
p: - ->p- B·(H2·H3)·(C7+H4) ;
: - ->+ B·(H5·H2·H3)·(C2·H3)t
Beam: 0.72, 0.88, 1.3 GeV/c; p/p=1.5%; p/p=0.2%; I=(5-1) ·105 /burst.
Targets: Li-6((90%), Li-7, C-12, O-16 in H2O, D2O ; 10x10 cm
Spark Ch. 70 gaps, ~30 space points/track, Ne-He, <5pictures/burst
Data: 0.75M pictures->taken->scanned->processed->analysed a lot of on-line/off-line/MC/physics software
Deuteron/triton selection by TOF
Mass of the flying particle was calculatedusing known momentum and TOF
PF = PB - Pd - Pπ ; MX2= (PB + PT - Pd ) 2
Plane Wave Impulse Approximation
π
Li-6
π
X
d
PF
PB Pd
Pπ
X= He-4, He*, dd, dpn …..
Emiss = TB - Td - Tπ = Md + MHe - Mli + E*He + TF
dN = nddσ(πd)NbNLiKε(PF ,Emiss)
D2O
H2O
MX2, GeV2
MX2= (PB + PT - Pd ) 2
Eve
nts
Eve
nts
PB
PdT
PF = PB - Pd - Pπ
Pπ
PF ,GeV/c
PF <70 MeV/c
PF = 0 for free deuteron
MX2= Mπ
2 =0.02 GeV2
for free deuteron
πd - elastic scattering on heavy water targetπd - elastic scattering on heavy water target
σP = 20 MeV/c
70 MeV/c cut
Emiss resolution as measured on
D2O target at 0.7 GeV/c
GeV
Emean = 1.15 MeV
σ = 15.5 MeV
For Li-isotopes due to smaller multiple
scattering in the target Emiss resolution
is 9.5 MeV.
Comparison of the measured differential crosssection for backward pion deuteron scatteringon free deuteron with data of Keller et al.
Excitation energy distribution for rest nucleus for deuteron knock out from Li-6
Li-6, 0.7 GeV/c
He-4 (0.60)
Emiss = 1.5 MeV
dd (0.65)
dpn (0.65)
Nd=1.90+-0.15
Emiss>22 MeV
Excitation energy distribution for rest nucleus for deuteron knock out from Li-7
(2 /n.d.f.=18/12)
5Heg.s.(0,55)
5Hee.s. (1.0)
He-5 hypothesys
Li-7, 0.7 GeV/c
Excitation energy distribution for rest nucleus for deuteron knock out from C-12
EmissGeV
C-12, 0.7 GeV/c
Emean = 43+/-2 MeV
σ = 22+/-2 MeV
∆E 0-35 35-60 60-100 Nd 0.39+/-0.06 0.71+/-0.11 0.63+/-0.14Nd 0.32+/-0.01 McGregor et al. (γ,pn),150 MeV
Nd = 1.73+/-0.15
O-16, 0.7 GeV/c
EmissGeV
Excitation energy distribution for rest nucleus for deuteron knock out from O-16
Emean = 34+/-2 MeV
σ = 18+/-2 MeV
Nd = 1.40+/-0.16
(p,d) inclusive
A0.66
(,d) full kinematics
Effective number of quasideuterons as a function of atomic number A.
Straight line approximation for particleabsorption in nuclear media
X
b
d
beam pion
scattered pion
Lb=0.55 FmLd=Lb/3Ls=Lb/4
RA
(p,d)
π,dπ
A0.33
Sutter(BNL)Azhgirey(JINR)
Arefiev(ITEP)
This experiment
π,dπ
(p,d)
A
Nef
fN
eff
ρ(r)
ρ(r)
(p,d)
(p,d)
(π,dπ)
(π,dπ)
Pb
C-12
b, Fm
b, Fm
Num
ber
of e
vent
s
Different A - dependences
~ R2 = A 2/3
h ~hR = A 1/3
L
h
h*2R = (L/2)2
~ hR ~ L2 = const
CONCLUSION
1. For the first time the quasielastic deuteron knock out has been studied on pion beam in full kinematics.
2. Peak of quasielastic deuteron knock out is clearly seen on all nuclei. It shows that single step mechanism dominates.
3. A-dependence of effective numbers of participating deuterons is practically constant from Li-6 to O-16 showing large difference in comparison with measurements of inclusive deuteron knock out by protons.
4. Simple calculations indicate that such a dependence can be connected with larger absorption for deuteron knock out in full kinematics measurements.