Neutron Emission and Evolution of Hot Nuclei Formed in ... - JINR

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Neutron Emission and Evolution of Hot Nuclei Formed in ... - JINR

XIX International Baldin Seminar on High Energy Physics Problems, 2008

Neutron Emission and Evolution of Hot Nuclei

Formed in High-Energy Reactions

Vladimir Yurevich

JINR, Dubna






Space-time picture of particle emission

Recent experiments and Neutron data

Reaction kinematics and Moving Source Model

Results of MSM analysis

Source characteristics

Source origin

Source contributions to neutron yield

Conclusion


Space-time picture of particle emission

Collisions of GeV hadrons and light nuclei with heavy nuclei

are effective method of

hot nuclear system production with small excitation of collective modes

Probability of hot nuclear system production in reactions:

π, p + A 1-12 GeV Shibata et al. 1983 (Exp.) ~30%

p + Au 2.55 GeV Avdeychikov et al. 1987 (Exp.,The.) ~20%

p + Au 2 GeV Ledoux et al. 1998 (Exp.,The.) ~25%

p + Au 2.16 GeV Avdeyev et al. 2002 (Exp.,The.) ~20%

He + Au 4, 14.6 GeV

C + Au 22.4 GeV

Avdeyev et al. 2002 (Exp.,The.) ~25-30%

4

V.I. Yurevich XIX ISHEPP Dubna 2008


Space-time picture of particle emission

Light projectile

(H,He,C)

Heavy

nucleus

First collisions of projectile

and target nucleons

Source 1 (CC&PC)

Ηot non-equilibrium stage

Source 2 (CC)

Emitted particles

n, p, π

n and LCP

Time

Stage of expansion

and thermalization

Freeze-out stage

(fragmentation)

Source 3 (CC)

De-excitation of fragments

by evaporation

Source 4 (CC&PC)

n, LCP and IMF

n

CC – Central collisions, PC – Peripheral Collisions

V.I. Yurevich XIX ISHEPP Dubna 2008


Recent experiments & Neutron data

Collisions of relativistic light nuclei with nuclei

Neutron emission (TOF data)

1-9 GeV p+A (ITEP, 1983)

0.1-0.8 GeV p+A (LANL, 1989-1993)

0.8-3 GeV p+A (KEK, 1995)

0.8-1.6 GeV p+A (Saclay, 2002)

0.8-1.6 GeV p+A (ITEP, 2003)

2 GeV p+A (JINR/RI, 2006-2008)

2 GeV d+Pb

4 GeV 4 He+Pb (JINR/RI, 2006)

24 GeV C+Pb

Charged particle emission

1-19 GeV p+Xe (AGS, 1989)

1 AGeV Au+C (EOS, 1998)

2 GeV p, 3 He+Ag-U (Saclay, 1998)

2-8 GeV p+Au

4,14.6 GeV 4 He+Au (FASA, 1999-2002)

22.4 GeV C+Au

1 GeV p+A (PINP, 2001)

1.8-4.8 GeV 3 He+Ag,Au (ISiS, 2004)

2.5 GeV p+Au (PISA, 2004)

0.2-1.4 GeV p+Xe (CHICSi, 2007)

V.I. Yurevich XIX ISHEPP Dubna 2008


Recent experiments & Neutron data

Experiments on neutron production

10

At Ep, E p

,GeV/u

A t

1

0,1

250

200

150

100

1 10 100

Neutron data set is very poor and

there is only a few experiments

with GeV nuclear beams !

-JINR, - ITEP, -PSCERN, -PSКЕК,

- BEVALAC, - SATURNE,

-HIMAC, - GANIL, -PSI,

-COSY, - LAMPF, - IUCF.

50

0

1 10 100

A p

Ap

V.I. Yurevich XIX ISHEPP Dubna 2008


Recent experiments & Neutron data

Measurements in Dubna (JINR/RI collaboration)

Accelerator complex of

Laboratory of High Energy Physics

JINR

V.I. Yurevich XIX ISHEPP Dubna 2008


Recent experiments & Neutron data

Measurements in Dubna (JINR/RI collaboration)

Angular range: θ>30 o

Studied process:

Neutron emission in decay

of excited nuclear system

Not studied process:

Neutron production in elastic and

quasi-elastic interactions and projectile

fragmentation

Ap

At

Region of small angles

Neutron detectors

Method of analysis:

Neutron data

2

d σ

dEdΩ

Moving Source Model used for

extraction and study of neutrons

emitted in different decay stages

V.I. Yurevich XIX ISHEPP Dubna 2008


Recent experiments & Neutron data

Measurements in Dubna (JINR/RI collaboration)

List of measurements

Projectile Energy Targets

p 2 GeV

Be, Al, Cu, Cd, Pb

d 2 GeV Pb

He-4 4 GeV

C, Pb

C-12 24 GeV C, Al, Cu, Cd, Pb

Status of data analysis:

− finished

in progress

V.I. Yurevich XIX ISHEPP Dubna 2008


Reaction kinematics and Moving Source Model

Central Collisions

Peripheral Collisions

Source 1

Nucleon-nucleon collisions

Time

Source 3

(fragmentation)

Source 2

(hot)

Multifragmentation

Hot non-equilibrium stage

(hot source decay)

Target spectator decay

High E* Medium E* Low E*

Fragmentation

with heavy remnant

Low E*

Source 4

De-excitation of remnant by evaporation

V.I. Yurevich XIX ISHEPP Dubna 2008


Reaction kinematics and Moving Source Model

2 4

d σ

E + m − p

i

cos

= ∑ β θ

pAi

exp( −(

− m) / T )

2 1/ 2

i

dEdΩ i= 1

(1 − β )

Parameters:

10 3 4

A i

– amplitude

β i

– velocity

T i

– temperature

i

β > β > β > β

1

1

2

2

T > T > T > T

3

3

4

4

d 2 σ/dEdΩ, mb MeV -1 sr -1

p+Pb

2 GeV

10 2

10 1

10 0

10 -1

10 -2

3

2

0,1 1 10 100 1000

10 4

10 3

4

JINR/RI data

d 2 σ/dEdΩ, mb MeV -1 sr -1

10 2

3

E, MeV

10

Neutrons from Hot and Fragmentation

1

2

p+Pb

1

Sources dominate in middle part of

2 GeV

12 C+Pb 1

θ=90 o 10 neutron energy spectra !

0

24 GeV 1

θ=60 o

10 -1

0,1 1 10 100 1000

E, MeV

V.I. Yurevich XIX ISHEPP Dubna 2008


Results of MSM analysis

Source characteristics

Temperatures

T , MeV

1000

100

10

1

p+A

He+Pb

JINR/RI (2 GeV) JINR/RI (4 GeV)

ITEP (1.6 GeV)

KEK (1.5 GeV)

C+Pb

JINR/RI (24 GeV)

79 MeV

22 MeV

5 MeV

1.7 MeV

T 1

T 2

T 3

T 4

T, MeV

1000

100

10

1

p+Pb

JINR

LANL JINR/RI

KEK

ITEP(2003)

ITEP(1983)

4 He+Pb

JINR

C+Pb JINR/RI

JINR

JINR/RI

70 MeV

21 MeV

4.65 MeV

1.6 MeV

T 1

T 2

T 3

T 4

0,1

0 50 100 150 200 250

A t

Constant values of source temperatures,

independent of target, projectile and energy

are observed !

0,1

0,1 1 10

E, GeV

50

V.I. Yurevich XIX ISHEPP Dubna 2008


Results of MSM analysis

Source characteristics

Hot & Fragmentation Sources

T 3

, MeV

T 2

, MeV

50

40

30

20

10

0

12

10

8

6

4

2

21 MeV

4.65 MeV

Temperatures

Hot source

(source 2)

Fragmentation

(source 3)

Ch. Particle data

Au+C p+Au

EOS(1998) PINP(2001)

PISA(2004)

3

He+Au Saclay(1998)

ISiS(2004)

Saclay(1998) p+Xe

CHICSi(2007)

Neutron data

LANL

ITEP(2003)

p+Pb

KEK

ITEP(1983)

p

He4 +Pb JINR/RI(2006)

C

β 2

β 3

0,20

0,15

0,10

0,05

0,00

0,020

0,015

0,010

0,005

Velocities

Hot source

(source 2)

Fragmentation

(source 3)

3 He+Au

ISiS(2004)

p+Au

FASA(1999)

PISA(2004)

p+Xe

AGS(1989)

0

0,1 1 10

50

0,000

0,1 1 10

50

E, GeV

E, GeV

Neutron and LCP sources have the same origin,

or these particles are emitted in the same decay processes !

V.I. Yurevich XIX ISHEPP Dubna 2008


Results of MSM analysis

Fragmentation Source

Nuclear Thermometers

• Double ratios of isotopic yields (ALADIN, EOS, INDRA, ISiS, CHICSi and PNPI)

• Slopes of kinetic-energy spectra

-LCP (AGS,Saclay, PISA)

- Thermal bremsstrahlung photons (TAPS)

- Neutrons (Dubna)

• Isospin thermometer (FRS)

Freeze-out temperature f

Neutron thermometer is

unique tool for determination

of hot nucleus temperature !

Recent results

Neutron thermometer 4.65(0.15) MeV

Double ratios of isotopic yields

Slope of LCP energy spectra

EOS (DT-He) 4.7(0.4) MeV

ISiS (DT-He) 5.0(0.5) MeV

CHICSi (Li-He) 4.9(0.2) MeV

Saclay (Z=2) 4.5(0.3) MeV

V.I. Yurevich XIX ISHEPP Dubna 2008


Results of MSM analysis

Source origin

Hot & Fragmentation Sources

σ 2

, b

20

15

10

p, 4He,C + Pb

Hot source

(source 2)

Fit

LANL

ITEP(2003)

p+Pb

KEK

ITEP(1983)

p

He4 +Pb JINR/RI(2006)

C

Source of particles & heating

Beam

energy

At

Δ, N*, π

production

Target

heating

σ 3

, b

5

0

0,1

30 Fragmentation

(source 3)

25

20

15

10

5

N+N - N Δ

N+π - Δ

N+N - N N*

N+π -N*

N π

N π

π Δ

N π

π Δ

N π

N π

σ (mb)

σ (mb)

30 D+N* Δ+Ν∗

20

10

N*

D Δ

0

0,0 0,5 1,0 1,5 2,0 2,5 3,0

40

p+n inelastic cross section

30

20

10

pp inelastic

pn inelastic

N*

Δ

D

D+N* Δ+Ν∗

0

0,1 1 10

E, GeV

50

β 2 ~0.02 & t2~25 fm/c

L(S2)


Results of MSM analysis

Source contributions to neutron yield

Mean neutron multiplicity of Source Si

Total mean neutron multiplicity

For pA-reactions at 1.5-2 GeV

At-dependence from MSM analysis:

M = 0.3A

1 t

1

3

M

2

= 0.2 + 0. 0143A t

M

3

= 0. 022A t

M = 0.008A

4 t

n

4

3

M

i

4


M n

= M i

M +

i=

1

=

σ

i

σ

in

σ

n

=

σ

1 3

4 3

= 0.2

+ 0.3At

+ 0.0363At

0.008A

or

t

n

t

in

M ≈ 0 .2 + 0. 092A

V.I. Yurevich XIX ISHEPP Dubna 2008


Results of MSM analysis

Source characteristics

Hot and Fragmentation Sources

give large fraction of emitted

neutrons in high-energy reactions !

V.I. Yurevich XIX ISHEPP Dubna 2008


Results of MSM analysis

Source contributions to neutron yield

Hot & Fragmentation Sources

(M 2

+M 3

)/M n

, %

100

80

60

40

20

p+A

(1.5-2 GeV)

41%

JINR/RI (2.0 GeV)

KEK (1.6 GeV)

ITEP (1.6 GeV)

Fit

Relative contribution, %

100

80

60

40

20

41 %

p+Pb

(M 2

+M 3

)/M n

M 2

/M n

0

0 50 100 150 200 250

A t

JINR/RI data

Reaction Energy Mn Source 2 Source 3

(GeV) (n/reac.) (%) (%)

p+Pb 2 21.8±3.4 16 22

4

He+Pb 4 22.5±3.5 19 23

12 C+Pb 24 29.1±4.5 16 26

0

0 1 2 3 4

E p

, GeV

About 41% of all neutrons are emitted

from Hot and Fragmentation Sources

and this value is independent of target,

projectile and energy in GeV energy range !

~41% of neutron multiplicity

V.I. Yurevich XIX ISHEPP Dubna 2008


Results of MSM analysis

Source contributions to neutron yield

M n

, neutron/reaction

30

p+A

KEK (1.5 GeV)

JINR/RI (2 GeV)

ITEP (1.6 GeV)

25

Saclay (1.6 GeV)

Cugnon formula (1.6 & 2 GeV)

Sum of source contributions

20

COSY (1.2 GeV)

Fit to COSY data

15

10

M, neutron/reaction

35

30

25

20

15

10

p+Pb

M n

35 (1 −1.32

( E + 1.4))

=

p

M n

M 2

+M 3

5

5

0

0 50 100 150 200 250

A t

0

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

E p

, GeV

Saturation effect with increasing of proton energy !

V.I. Yurevich XIX ISHEPP Dubna 2008


CONCLUSION

• New measurements of neutron production cross sections have been carried out

4

in Dubna with beams of p, He and C at GeV energies.

• Developed MSM with four decay processes (neutron sources) is effective tool

for neutron data analysis in high-energy reactions.

• The analysis of TOF neutron data in GeV energy range shows:

- source temperatures do not depend on beam energy, projectile and target nuclei,

- neutron and charged particle sources have the same origin,

- about 41% of mean neutron multiplicity in reactions comes from hot source

decay and multifragmentation occurring in central collisions.

• For further progress new experiments with event selection on impact parameter

and reaction energy are needed.

V.I. Yurevich XIX ISHEPP Dubna 2008

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