novel technique to measure the polarizability of the nucleon*
DESCRIPTION
Novel Technique to Measure the Polarizability of the Nucleon*. Olena Yevetska Institut für Kernphysik, TU Darmstadt. Motivation Experimental Setup Experiments Results Summary and Outlook. SFB 634. *Supported by the DFG within SFB 634. E. B. Motivation. a , b - electric and - PowerPoint PPT PresentationTRANSCRIPT
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 1
Novel Technique to Measure the Polarizability of the Nucleon*
Olena YevetskaInstitut für Kernphysik, TU Darmstadt
SFB 634
• Motivation
• Experimental Setup
• Experiments
• Results
• Summary and Outlook
*Supported by the DFG within SFB 634
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 2
Motivation
, - electric and magnetic
polarizabilitiesu
d
u
u
d
u E
Bd = E = B
describe the response of the nucleon internal structure to applied electric and magnetic fields
3410)3.15.09.11( fmp 3410)3.07.02.1( fmp
V. Olmos de Leon et al., Eur. Phys. J. 10 (2001) 207
Goal: better accuracy of these constants
3410)4.28.8( fmn
3410)4.25.6( fmn
M. Lundin et al., Phys. Rev. Lett. 90 (2003) 192501
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 3
Motivation
Low energy Compton scattering ( E < 140 MeV)
Low Energy Theorem:
intPod
),E(d
Powell cross section for the point like proton with anomalous magnetic moment
Structure term
)E( 40 Terms of higher order structure constants
V. Petrun‘kin et al., Sov. J. Part. Nucl. 12 (1981) 278
)(0),(),( 4
Ed
Ed
d
Ed
Poin
tPoint
2´
22 )cos1(2
)cos1(2 E
~
+ -
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 4
Experiment with Compton Scattering
previous now E´
p,dEp,d
´
DetectorDetector
Target
1023 protons/cm21022 protons/cm2
E,
Liquid H/D-target Active high pressure H/D-target
• high luminosity: 106 /MeV/s 109 /MeV/s
• background suppression:redundancy of kinematic values
• Bremsstrahlung spectrum has to be known
E´
´
Ep = 0.4 – 8 MeV
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 5
S-DALINAC
5 m
Accelerator Hall Experimental Hall
( ́ ) & - Experiments (n)
Compton Scattering on Nucleon
(e,e´x) & 180°- Experiments at QCLAM Spectrometer
(e,e´) - Experiments at Lintott Spectrometer
( ´x)- Experiments at NEPTUN Tagger
Design Parameters
Maximum energy: 130 MeV
Energy spread : 10-4
Maximum current: 20 A
Material: Niobium
Temperature: 2K
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 6
Experimental Setup
1 – Bremsstrahlung facility2 – Collimator system3 – Faraday cup4 – Concrete shield
1m
2
1
6
5
7
8
7
9
43
4
5 – High pressure ionisation cahmber6 – NaI(Tl) spectrometer (10“x14“)7 – Collimator system8 – BPM, Quantameter 9 – NaI(Tl) spectrometer (10“x10“)
6
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 7
Bremsstrahlung
Ee = 71.3 MeV t = 40 min
Ie = 200 pA under 0°
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 8
1 – Bremsstrahlung facility2 – Collimator system3 – Faraday cup4 – Concrete shield5 – High pressure ionisation chamber
Experimental Setup
1m
2
1
6
5
7
8
7
9
43
4
6
6 – NaI spectrometer (10“x14“)7 – Collimator system8 – BPM, Quantameter 9 – NaI spectrometer (10“x10“)
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 9
High Pressure Ionisation Chamber
Determination of the energy and the position of the
recoiled protons
0.4 MeV ≤ Ep ≤ 8 MeV
Strips in the direction of the recoiled protons
proton track electrons
cathode (-60kV)
anode strip (0kV)
grid (-5kV)
17.0
1.0
20 MeV ≤ E ≤ 90 MeV
p
e
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 10
Proton Signals
Flash ADC (FADC)
Sampling: 105 MHz, 10 nsTime window: 4.5 s
IK
NaI(Tl)
FADC
Trigger
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 11
High Pressure Ionisation Chamber
1 cm
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 12
Normalisation
Compton kinematics
Proton vs. electron
Arrange and mass
e
)e(
p
)p(
m
cos
m
cos
11
identical kinematics
)cos(m
E
EE '
11
p = 90° 130°e = 1.89° 2.42°
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 13
Experimental Setup
1m
2
1
6
5
7
8
7
9
43
4
6
1 – Bremsstrahlung facility2 – Collimator system3 – Faraday cup4 – Concrete shield5 – High pressure ionisation chamber
6 – NaI spectrometer (10“x14“)7 – Collimator system8 – BPM, Quantameter 9 – NaI spectrometer (10“x10“)
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 14
dd
),(dd
CN
Ne
p
e'
p'
Normalisation
N‘ – number of Compton events
N – number of incoming photons
NT – number of target nuclei
– detector efficiency
– solid angle
dddd
N
N
N
N
N
N
d
dNNN
e
p
e
p
eT
pT
e
p
e'
p'
T'
e
p
eT
pT
eγ
pγ
N
N
N
N
C
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 15
Experiments
August 2006 April-May 2007
Current Ie, A 1-7 1-3**pulsed beam
Energy Ee, MeV 60 79
Charge, Ah 1116.4 333.54
Pressure, bar 73.5 73.5
Voltage, kV VC = 39, VG = 3.5 VC = 39, VG = 3.5
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 16
First Results
)cos(m
E
EE
EEE
p
'
'p
11
10 20 30 40 50 600
1000
2000
3000
4000
5000
6000
Ep (
keV
)
E' (MeV)
Chamber 130° Experiments (N
p = 3459)
Fit
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 17
Summary and Outlook
SFB 634
• Experiments were performed
• Preliminary results were shown
• Analysis is running
• Simulations with GEANT4
• Better statistics
• Experiment with deuteron
10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 18
Institut für Kernphysik, TU Darmstadt, Darmstadt, Germany:
O. Yevetska
A. Richter
G. Schrieder
S. Watzlawik Petersburg Nuclear Physics Institute, Petersburg, Russia:
V. Chizhov
V. Iatsioura
E. Maev
E. Orishchin
G. Petrov
L. Sergeev
Y. Smirenin Institut für Kernphysik, Johannes Gutenberg-Universität, Mainz, Germany:
J. Ahrens