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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

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novel technique to measure the polarizability of the nucleon

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

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 1

motivation

E

B

Motivation

a, b- electric and

magnetic

polarizabilities

m = bB

d = aE

describe the response of the nucleon internal structure

to applied electric and magnetic fields

V. Olmos de Leon et al., Eur. Phys. J. 10 (2001) 207

M. Lundin et al., Phys. Rev. Lett. 90 (2003) 192501

Goal: better accuracy of these constants

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 2

motivation1

Point

t

~

a+b

a-b

Motivation

Low energy Compton scattering ( E < 140 MeV)

Low Energy Theorem:

Powell cross section for the point like proton with anomalous magnetic moment

Structure term

Terms of higher order structure constants

V. Petrun‘kin et al., Sov. J. Part. Nucl. 12 (1981) 278

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 3

experiment with compton scattering
Experiment with Compton Scattering

previous

now

Eg´

Eg´

Detector

Detector

1023 protons/cm2

1022 protons/cm2

Eg, qg

qg

qg´

qg´

Target

Ep,d

qp,d

Liquid H/D-target

Active high pressure H/D-target

Ep = 0.4 – 8 MeV

  • high luminosity:
  • 106g/MeV/s 109g/MeV/s
  • background suppression:
  • redundancy of kinematic values
  • Bremsstrahlung spectrum has to be known

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 4

s dalinac
S-DALINAC

Accelerator Hall

Experimental Hall

5 m

Design Parameters

Maximum energy: 130 MeV

Energy spread : 10-4

Maximum current: 20 mA

Material: Niobium

Temperature: 2K

g,g

g,

n)

- Experiments

(

´) &

(

Compton Scattering on Nucleon

g,g

´x)- Experiments at NEPTUN Tagger

(

(e,e´x) & 180°- Experiments

at QCLAM Spectrometer

(e,e´) - Experiments

at Lintott Spectrometer

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 5

experimental setup
Experimental Setup

6

7

7

2

5

1

8

1m

9

3

4

6

4

5 – High pressure ionisation cahmber

6 – NaI(Tl) spectrometer (10“x14“)

7 – Collimator system

8 – BPM, Quantameter

9 – NaI(Tl) spectrometer (10“x10“)

1 – Bremsstrahlung facility

2 – Collimator system

3 – Faraday cup

4 – Concrete shield

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 6

bremsstrahlung
Bremsstrahlung

Ee= 71.3 MeV t = 40 min

Ie = 200 pA under 0°

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 7

experimental setup1
Experimental Setup

6

7

7

2

5

1

8

1m

9

3

4

6

4

6 – NaI spectrometer (10“x14“)

7 – Collimator system

8 – BPM, Quantameter

9 – NaI spectrometer (10“x10“)

1 – Bremsstrahlung facility

2 – Collimator system

3 – Faraday cup

4 – Concrete shield

5 – High pressure ionisation chamber

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 8

high pressure ionisation chamber
High Pressure Ionisation Chamber

Determination of the energy and the position of the

recoiled protons

Strips in the direction of the recoiled protons

p

e

20 MeV ≤ Eg≤ 90 MeV

0.4 MeV ≤ Ep≤ 8 MeV

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 9

proton signals
Proton Signals

FADC

IK

Flash ADC (FADC)

Sampling: 105 MHz, 10 ns

Time window: 4.5 ms

NaI(Tl)

Trigger

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 10

high pressure ionisation chamber1
High Pressure Ionisation Chamber

1 cm

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 11

normalisation
Compton kinematics

Proton vs. electron

Arrange q and mass

Normalisation

identical kinematics

qp = 90° 130°

qe = 1.89° 2.42°

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 12

experimental setup2
Experimental Setup

6

7

7

2

5

1

8

1m

9

3

4

6

4

6 – NaI spectrometer (10“x14“)

7 – Collimator system

8 – BPM, Quantameter

9 – NaI spectrometer (10“x10“)

1 – Bremsstrahlung facility

2 – Collimator system

3 – Faraday cup

4 – Concrete shield

5 – High pressure ionisation chamber

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 13

normalisation1
Normalisation

Ng‘ – number of Compton events

Ng – number of incoming photons

NT– number of target nuclei

e– detector efficiency

DW – solid angle

C

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 14

experiments
Experiments

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 15

first results
First Results

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 16

summary and outlook
Summary and Outlook
  • Experiments were performed
  • Preliminary results were shown
  • Analysis is running
  • Simulations with GEANT4
  • Better statistics
  • Experiment with deuteron

SFB 634

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 17

slide18
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

10.03.2008 | Institut für Kernphysik | TU Darmstadt | Olena Yevetska | 18