Measurement of pd breakup cross sections at E/A = 13 MeV in the off-plane star configuration

1
Measurement of pd breakup cross sections at E/A
13 MeV in the off-plane star configuration
FB19 2009/8/31

• Yukie Maeda (University of Miyazaki)
• H. Shimoda, K. Sagara, S. Kuroita, T. Sueta, Y.
  Eguchi, K. Yashima (Kyushu Univ.)
• A. Nonaka, N. Fujita (Univ. of Miyazaki)
• D. Ishikawa, K. Hatanaka, H. Okamura, A. Tamii
  (RCNP, Osaka Univ.)

2
Introduction
Kievsky et al, PRC64 (2001) 24002.

• Study of the three-nucleon system at low energy
  region
• DCS of elastic scattering
• 3NF effect is small
• NN 3NF Coulomb reproduce the data well

3
pd breakup reaction _at_ low energy
A. Deltuva et al, PRL95 (2005) 92301.

• Study at 13MeV for some configurations(solidpd,
  opennd)
• Quasi-free scattering (QFS)
• Final state interaction (FSI)
• Introduction of the Coulomb into the calculation
  improved the predictions.
• Some discrepancies are left to be explained.
• Space-star (SST)
• Large discrepancy between the data of pd and nd
  can not be explained by the Coulomb effects.
• The theoretical prediction overestimates the pd
  data about 20.

CD Bonn D Coulomb CD Bonn D
?
SST
QFS
FSI
4
Off-plane star configurations

• a90 Space Star.
• a 0, 180 Coplanar Star.
• a?0,180 Off-plane Star.

Definition in this talk The a is the angle
between p-beam axis and the equilateral trianglr
plane which include the momentum of p1, p2, n
in the c.m. system.
5
Data from Köln
J. Ley et al, PRC73 (2006) 64001.

• 1H(d,pp) breakup measurement at Ed19MeV
  (9.5MeV/A) at Köln
• 3NF effects slightly improve the theory by 5
  8.
• The predictions with 3NF and Coulomb effects
  still overestimate the data up to 30.

CD Bonn CD Bonn D CD Bonn D Coulomb
Off-plane-star anomaly
6
Motivation

• We performed the measurements of 1H(d,pp) breakup
  reactions at Ed 26 MeV at RCNP
• Off-plane star anomaly is truly exist or not?
• Systematical study of the discrepancy between the
  data and the theory
• Measurements for some other configurations (SST,
  FSI) of pd breakup reactions have performed at Ep
  13 MeV at KUTL tandem accelerator, Kyushu
  University.
• Off-plane star configuration measurements of
  2H(p,pp) at Ep 13 MeV at KUTL.
• Range of a 0 180 deg will be covered by the
  data of RCNP KUTL

7
Experimental procedure

• 1H(d,pp) breakup reactions at Ed 26 MeV
• 26MeV deuteron beam from AVF
• Proton target CH2 (polyethylene)
• Two proton detection 3pairs of SSDs
• Luminosity monitor
• dp elastic scattering
• Configurations
• a 120, 140, 160, 180 deg

Skip beam line
F.C.
Left detectors
Right detectors
p1
CH2
Monitor
p2
d-beam
8
Setup

• Two protons detection by using a pair of 3000 mmt
  SSD (Si-Li)

(msr)
(msr)
a qRL fR fL DWR DWL
180 22.0 0.0 180.0 0.333 0.321
160 22.7 11.2 168.8 0.319 0.291
140 24.5 20.4 159.6 0.272 0.287
120 27.1 26.6 153.4 0.241 0.243

• Monitor SSD q 35.0, f0, DWR 0.0306(msr)
• Monitoring of the target thickness by measuring
  the pd elastic scattering
• Calibration of the solid angles of each detectors
• Measurement of the Cp elastic scattering at q
  35.0 by using each SSD and Monitor-SSD
  simultaneously

9
Rotary target
Motor

• Simulation
• At 20 r.p.m., the temperature of the target foil
  increases only 15 degrees.

Rotation feedthrough
Atmosphere
Deutron 26MeV 200nA , 0.3mg/cm2
Beam spot

• Rotary target system
• Through magnetic coupling, a shaft in a vacuum
  chamber is rotated by a motor in the air.
• The target foil 5cm diameter.
• Rotation speed 20 r.p.m.
• Rotary target can be lift up in vacuum, and other
  foil targets can be used in turn.

Inside Scattering chamber
Beam
Beam Line
10
Uniformity of the target thickness

• Thickness of a CH2 rotary target was constant for
  20 hours.

Change of CH2 thickness
Stationary CH2 target 25??100? (Beam Intensity
100nA)
Rotate CH2 target 25??40? (Beam Intensity 200nA)
0 2.5 10
20
Time (hour)
High luminosity was obtained without the decrease
of CH2 target thickness!
11
Analysis

• Most of the data is the accidental coincidence
  events
• Event selection by using the information of the
  time difference between p1 and p2

Single energy spectrum
E1-E2 spectrum after TOF gate
H(d,d)
H(d,d)
C(d,d)
H(d,p)
breakup
C(d,d1)
S-curve of true events
12
Results

• DCS

Theoretical predictions can reproduce the data
well.
13
Systematic error

• Derivation of the data

? Sagara et. al, PRC50,576 (1994)
List of the error source
DW1, DW2 /- 2.6
DWmon /- 1.5
Y12 /- 1.0
Ymon /- 0.5
total /- 4.1
14
Angular energy dependence

• Ratio of data/calc. at the star configuration
• We can not see the large anomaly in the backward
  region at 13MeV/A, which is different from the
  Köln data at 9.5MeV/A .
• More experimental studies are needed to see the
  energy dependence of the anomaly.

This work
15
Summary

• To study the off-plane star anomaly, we performed
  the experiment of 1H(d,pp) and 2H(p,pp) breakup
  reactions at E/A 13MeV at RCNP and KUTL.
• Si-Li type SSDs were used for detecting 2 protons
  in coincidence.
• Rotary target system allowed us to obtain high
  luminosity.
• The differential cross sections for a 120 180
  deg (RCNP) and 0 75 deg (KUTL) were measured.
• From the comparison between the data and the
  theoretical predictions
• The data at 13MeV/A can be well reproduced by the
  calculations including the Coulomb effects, which
  is different from the data of Köln.
• It is better to perform the experiment at Ed
  19MeV at RCNP to confirm the large anomaly
  reported from Köln.

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END
17
SCRE configurations

• Off-plane star configuration
• a0 (coplanar star), 17.7, 36, 56 deg
• Two proton detection in coincidence by a pair of
  SSDs.
• Differential cross sections and Tensor analyzing
  powers
• Normalization dp elastic scattering
• Rawdata E3, E4, Dt

E2
E1
18
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• ???????
• ?????

? pd elastic scattering