FB18, Santos JZ / Aug. 25, 2006

Experimental Studies on Kaonic Atoms

at DANE

Johann Zmeskal Stefan Meyer Institute for subatomic Physics

Austrian Academy of Sciences, Vienna, Austria

for the DEAR/SIDDHARTA Collaborations

18th International IUPAP Conferenceon Few-Body Problems in Physics

Aug. 21 – 26, 2006 - Santos, Brazil

LNF - ItalySMI - AustriaINFN Trieste - Italy IPNE - RomaniaUniv. Fribourg - SwitzerlandUniv. Neuchâtel - SwitzerlandRIKEN - JapanUniv. Tokyo - JapanUniv. Victoria - CanadaUCB - USA

2FB18, Santos JZ / Aug. 25, 2006

Content

Motivation The DEAR experimental set-up Kaonic atom measurements with

DEAR Results on kaonic nitrogen Results on kaonic hydrogen

The SIDDHARTA project New X-ray detectors New setup Physics goals

Summary & Outlook

3FB18, Santos JZ / Aug. 25, 2006

Experiments with exotic atoms,

a broad research field

K-p, K-d-p, -d….

4FB18, Santos JZ / Aug. 25, 2006

Motivations

K-p simplest exotic atom with strangeness

strong interaction shift ε1s and width Γ1s

directly observable by X-ray spectroscopy

K-p: Information on Λ(1405) antikaon bound nuclear clusters

(A. Gal P24, Theory overview of antikaon bound state

N.V. Shevchenko R1-26, Search for a K-pp bound state)

kaonic hydrogen, precision data missing

kaonic deuterium never measured before

5FB18, Santos JZ / Aug. 25, 2006

Kaonic Hydrogen - Goals

Measurement of strong interaction shift and width of kaonic hydrogen and kaonic deuterium with an accuracy of a few eV

Determination of the isospin dependent scattering lengths near threshold

no extrapolation to zero energy

Testing chiral symmetry breaking in systems with strangeness

6FB18, Santos JZ / Aug. 25, 2006

Review – results before DEAR

K-p interaction attractive/repulsive ? Solution by KEK experiment

wid

th

1s

[eV

]

KpX

-500 50000

200

400

600

800

1000

shift 1s [eV]

Dav

ies

et a

l, 19

79

Izyc

ki e

t al,

1980

Bir

d et

al,

1983

repulsive attractive

KpX (KEK)M. Iwasaki et al, 1997

=

- 3

23 ±

63

± 11

eV

=

407

± 2

08 ±

100

eV

7FB18, Santos JZ / Aug. 25, 2006

Strong Interaction in K-p

1s

1s

s p d f

E1s}

E2p

n

43

2

1

K

Due to the strong interaction kaon-protonthe 1s level is shifted and broadened

Shift and width of states n>1negligible

KkeV

ε1s = E2p-1s(meas.) – E2p-1s(e.m.)

8FB18, Santos JZ / Aug. 25, 2006

Scattering Lengths

Relation of strong interaction shift and width to the complex Kp scattering length aK-p

)(

4122)0(2

21232

1

ThirringBaumannGoldbergerDeser

aeVfmaaipKpKpKs

For the determination of the isospin dependent scattering lengths a0 and a1 the hadronic shift and width of kaonic hydrogen and kaonic deuterium are necessary

9FB18, Santos JZ / Aug. 25, 2006

Requirements

Kaon Beam at DANE with unique performance

Slow, nearly monochromatic kaons (E~16 MeV) Kaon pair emitted back-to-back Low hadronic background

Target System Cryogenic gas target, pure hydrogen gas Thin windows, light-weight construction

X-ray Detector Large active area Superior energy resolution Background suppression capability

Calibration “online“ calbration – fluorescence lines

10FB18, Santos JZ / Aug. 25, 2006

DANE (LNFrascati)

electron – positron collider collision energy tuned to the Φ resonance at 1.02 GeV c.m.

electron – positron collider collision energy tuned to the Φ resonance at 1.02 GeV c.m. DEAR

11FB18, Santos JZ / Aug. 25, 2006

DEAR Setup at DAΦNE

TMP

CCD electronics

Vacuum chamber

APD Cryo-Cooler

Target Cell

CCD cooling

CCD pre-amplifier

CCD55-chips

e+ e-

K-

12FB18, Santos JZ / Aug. 25, 2006

CCD X-ray Detection

Array of 16 CCD55-30 -1242 x 1152 pixels / chip- pixel size 22.5 x 22.5 µm- total area per chip 7.24 cm2

- depletion depth ~30 µm- read-out time per CCD 2 min.- energy resolution ~150 eV @ 6keV- temperature stabilized at 165 K

Array of 16 CCD55-30 -1242 x 1152 pixels / chip- pixel size 22.5 x 22.5 µm- total area per chip 7.24 cm2

- depletion depth ~30 µm- read-out time per CCD 2 min.- energy resolution ~150 eV @ 6keV- temperature stabilized at 165 K

13FB18, Santos JZ / Aug. 25, 2006

DEAR Target

Light-weight cylindrical target structure

Diameter: 12.5 cmHeight: 14 cmVolume: 1150 ccm Side wall: 75 µm HostaphanEntrance window: 125 µm HostaphanGrid structure: glass fiber reinforced epoxy

Hydrogen filling:Temperature: 25 K (hydrogen)Pressure: 2 barDensity: 2.1 g/l (3 % LHD)

Light-weight cylindrical target structure

Diameter: 12.5 cmHeight: 14 cmVolume: 1150 ccm Side wall: 75 µm HostaphanEntrance window: 125 µm HostaphanGrid structure: glass fiber reinforced epoxy

Hydrogen filling:Temperature: 25 K (hydrogen)Pressure: 2 barDensity: 2.1 g/l (3 % LHD)

kaon

14FB18, Santos JZ / Aug. 25, 2006

Kaonic nitrogen

published in : Phys. Lett. B 593 (2004) 48-54

15FB18, Santos JZ / Aug. 25, 2006

Resulting K-p X-ray Spectrum

X-ray energy spectrum with all background fit-components subtracted

1s = - 193 ± 37 (stat.) ± 6 (syst.) eV1s = 249 ± 111 (stat.) ± 30 (syst.) eV

1s = - 193 ± 37 (stat.) ± 6 (syst.) eV1s = 249 ± 111 (stat.) ± 30 (syst.) eVAt lowest order:

aK-p= (-0.468 ± 0.090stat± 0.015syst) + i(0.302± 0.135stat± 0.036syst) fm

16FB18, Santos JZ / Aug. 25, 2006

DEAR Resultsw

idth

1

s[e

V]

KpX

-500 50000

200

400

600

800

1000

shift 1s [eV]

Dav

ies

et a

l, 19

79

Izyc

ki e

t al,

1980

Bir

d et

al,

1983

repulsive attractiveKpX (KEK)M. Iwasaki et al, 1997

=

- 3

23 ±

63

± 11

eV

=

407

± 2

08 ±

100

eV

DEAR

17FB18, Santos JZ / Aug. 25, 2006

From DEAR to SIDDHARTA

Precision of the DEAR result limited by high X-ray background (S/N~1:70)

Next step: background reduction by using kaon – X-ray time correlation(expected background suppression~ 3 orders of magnitude S/N ~ 10:1 for kaonic hydrogen)

New X-ray detectors SDDs

New dedicated target-detector set-up

18FB18, Santos JZ / Aug. 25, 2006

New X-ray Detector - SDD

New X-ray detectors with timing capability background suppression

by using the kaon - X ray time correlation excellent energy resolution high intrinsic efficiency, large area

Development of large area SDD detectors

JRA10 in I3HP (EU FP6)

19FB18, Santos JZ / Aug. 25, 2006

Silicon Drift Detector SDD

Large area SDD with 1 cm2 active area3 SDD on 1 chip

SDD has small capacitance low noise Good energy resolution, comparable with CCD But: timing capability (t < 0.5 µs)

SDD with JFET

20FB18, Santos JZ / Aug. 25, 2006

Performance of Large SDDs

First application of large (1 cm2) SDDs in K-He experiment at KEK (see talk by S. Okada at this Workshop)

21FB18, Santos JZ / Aug. 25, 2006

Triple coincidence: SDDX * ScintK * ScintK

Scintillator

Scintillator

hydrogen gas

SD

De+

e-

K+

K-

X-ray

Background suppression

22FB18, Santos JZ / Aug. 25, 2006

Energy (keV)Energy (keV)

No timingSDD‚single‘

coinc.SDD * Scint * Scint

Backgroundsuppressionto < 10-3

Kaonic deuterium

K K

Ag K fluorescencelines (calibration)

Kaonic Deuterium (MC)

23FB18, Santos JZ / Aug. 25, 2006

SIDDHARTA Setup

Cryogenic setup

SDD array(~200 cm2 SDDs)

24FB18, Santos JZ / Aug. 25, 2006

SDD unit (2x3x3 SDDs)

25FB18, Santos JZ / Aug. 25, 2006

SIDDHARTA Setup cont‘d

Cryogenic target cell

Target cell – SDD array assembly

Cryogenic target cell75 µm Kapton within a pure aluminum gridPmax. ~ 5 bar

26FB18, Santos JZ / Aug. 25, 2006

SIDDHARTA Setup – side view

C C

BB

SIDDHARTA SETUPSchnitt A-A

571,

0084

8,00

1190,00

105,

00

1524

,00

SDD ArrayGas target

Beam pipe

Kaon Detector

27FB18, Santos JZ / Aug. 25, 2006

Material Analysis by PIXE

Carefully selected structure materials analyzed by PIXE@VERA:Avoiding iron content

28FB18, Santos JZ / Aug. 25, 2006

Monte Carlo Results

Co

un

ts

Energy [keV] Energy [keV]

K-p K-dKα

Kβ

Kγ

Khigh

Monte Carlo simulated X-ray spectra (data taking 30 days).Measurement with SDD array and kaon trigger.

K-p: ε1s = 193 eV, Γ1s = 249 eV, Y(Kα )=2%ε1s= 2eV, Γ1s= 4eV

K-d: ε1s = 325 eV, Γ1s = 630 eV, Y(Kα )=0.2%ε1s= 18eV, Γ1s= 45eV

29FB18, Santos JZ / Aug. 25, 2006

SIDDHARTA - Outlookw

idth

1

s[e

V]

KpX

-500 50000

200

400

600

800

1000

shift 1s [eV]

Dav

ies

et a

l, 19

79

Izyc

ki e

t al,

1980

Bir

d et

al,

1983

KpX (KEK)M. Iwasaki et al, 1997

=

- 3

23 ±

63

± 11

eV

=

407

± 2

08 ±

100

eV

DEAR

SIDDHARTA

30FB18, Santos JZ / Aug. 25, 2006

Outlook

Future physics program at DAΦNE

Measurement of kaonic deuterium

(first measurement ever)

Precision measurement of kaonic hydrogen

(at the percent level).

Further perspectives: Kaonic helium studies with 3He and 4He targets

Precision measurement of charged kaon mass

31FB18, Santos JZ / Aug. 25, 2006

SUMMARY

First production of exotic atoms at DAΦNE, Successful measurements on kaonic hydrogen

New X-ray detector (SDD array) and setup in preparation,

Installation at DAΦNE 2007

repulsive shift in K-p verified smaller shift and width values, higher precision

32FB18, Santos JZ / Aug. 25, 2006

Spare

33FB18, Santos JZ / Aug. 25, 2006

Results on kaonic nitrogen

3 X-ray transitions - first measured

extraction of the transition yields for 7-6, 6-5, 5-4

34FB18, Santos JZ / Aug. 25, 2006

K-p and K-d Atoms

Kaonic Atom Kaonic Hydrogen

Kaonic Deuterium

e.m. positionof K line (eV)

6480 7810

1s (eV) ~200 (DEAR) *) theory

1s (eV) ~250 (DEAR) *) theory

X-ray Yield (K ) 1-3 % ~0.2% (estimate)*) new studies: c.f. A.N. Ivanov et al., Eur.Phys.J. A 23 (2005) 79,

U.-G. Meißner, U. Raha and A. Rusetsky, arXiv:nucl-th/0603029, 2006

K-p (K-d) e.m. bound kaonic atoms, Bohr radius ~80 fm