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.