55. Jahrestagung der ÖPG, September 2005 Präzisionsmessungen mit kaonischen Atomen – von DEAR zu...

55. Jahrestagung der ÖPG, September 2005

Präzisionsmessungen mit kaonischen Atomen – von DEAR zu SIDDHARTA

J. MartonStefan Meyer Institut der ÖAW

on behalf of the DEAR / SIDDHARTA Collaborations


Motivation

• Exotic (kaonic, pionic) hydrogen atoms are used as sensitive probes for strong interaction

• Strong interaction shift ε1s and width Γ1s are directly observable by precision X-ray spectroscopy

NuPECC Long Range Plan 2004Fundamental Interactions: Recommendations

… Exotic atom spectroscopy providesimportant input for the further development of low energy QCD. …


DEAR Collaboration @ LNF

Work supported by TARI-INFN,Contract HPRI-CT-1999-00088and

Contract No. RII3-CT-2004-506078

G. Beer1, A.M. Bragadireanu2, M. Cargnelli3, C. Curceanu(Petrascu)4,2, J.P. Egger5, H. Fuhrmann3, C. Guaraldo4 (spokesperson), M. Iliescu4,2, T. Ishiwatari3, K. Itahashi6, M. Iwasaki6, P. Kienle3, B. Lauss7, V. Lucherini4, L. Ludhova8, J. Marton3, F. Mulhauser8, T. Ponta2,4, L.A. Schaller8, R. Seki9,10, D. Sirghi4, F. Sirghi4, P. Strasser6, E. Widmann3 and J. Zmeskal3

1Univ. of Victoria; 2Inst. of Physics and Nuclear Engineering “Horia Hulubei”;

3Stefan Meyer Institut of the Austrian Academy of Sciences; 4INFN Laboratori Nazionali di Frascati;5Université de Neuchâtel; 6RIKEN; 7University of California; 8Université de Fribourg; 9California Institute of Technology; 10California State University


Kaonic hydrogen atoms used

as probes for strong interaction

strong interaction shift ε1s and width Γ1s

directly observable by X-ray spectroscopy

K-p: Information on Λ(1405)

deeply bound states (kaonic nuclear Clusters)

Kaonic Hydrogen: Motivation

Breaking news from KEK, FINUDA@DAΦNE(c.f. T. Suzuki et al., Phys. Lett. B597 (2004) 263, M. Agnello et al. PRL 94 (2005) 21303)


• Kaonic hydrogen / deuterium Kp simplest exotic atom with strangeness

kaonic hydrogen „puzzle“ solved –

but: precision data missing

kaonic deuterium never measured before

atomic physics: new cascade calculations to be tested

Motivation cont‘d


Precision measurement of strong interaction shift and width of kaonic hydrogen and kaonic deuterium at the highest precision

• Determination of the isospin dependent scattering lengths

no extrapolation to zero energy

• Testing chiral symmetry breaking in systems with strangeness

Goals


K-p and K-d atoms

• K-p (K-d) e.m. bound kaonic atoms• Bohr radius ~80 fm• binding energy ~9 keV• strong interaction range ~1 fm• strong interaction treated perturbatively

Kaonic atom

e.m. position

of K line

(eV)

(eV)

(eV)

hydrogen 6480 200 250

deuterium 7810 325 630

X-ray Yield

~1-3%

~0.2 % !


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

Scattering Lengths

)(

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

But: isospin-breaking and e.m. corrections


Kaonic Hydrogen

Negative kaons stopped in H2 initial atomic capture electromagnetic cascade X-ray transitions

1s

1s

s p d f

E1s}

E2p

n

43

2

1

KkeV

ε1s = E2p-1s(meas.) – E2p-1s(e.m.)

K

As the kaon interacts strongly with the nucleus the 1s energy level is shifted and broadened

Shift and width of states n>1 negligible


DEAR

DAΦNE (LN Frascati)

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.

http://www.oeaw.ac.at/imep/imep/lnfdear.htm


Experimental Set-up

TMP

CCD Electronics

Vacuum Chamber

APD Cryo-Cooler

Target Cell

CryoTigerCCD Cooling

CCD Pre-Amp

CCD55-Chips

e+ e-

X-ray energy measurement of kaonic K lines with an array of 16 CCD X-ray detectors

X-ray energy measurement of kaonic K lines with an array of 16 CCD X-ray detectors

kaons from Φ decayLight-weight cylindrical target structure


CCD-Detector Array

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


Shielding

Overall shielding factor of the DEAR interaction region ~ 100


DEAR Setup at DAΦNE


Features of the Experiment

• Low energy (16 MeV) nearly mono-energetic (Δp/p ~ 0.1%) kaons from meson decay (pion-induced background largely suppressed compared to proton accelerator, ~ factor 100)

• Light weight cryogenic target for low X-ray background

• Carefully chosen structure materials (checked by different analysis methods, e.g. XFA)

• Optimized gas density for high X-ray yield (cryogenic gas target, 3% LHD)

• CCD array for X-ray detection (16 CCD-55, large area 116 cm2, pixel analysis for background reduction, excellent energy resolution)

• Shielding for background reduction

• Performance verified first with kaonic nitrogen measurement


Kaonic Nitrogen X-ray Spectrum


3 X-ray transitions first measured

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

Impact on cascade calculations

Kaonic nitrogen nearly fully stripped of electrons: high precision measurement of the charged kaon mass possible

Kaon mass (test) mK- = 493.884 ± 0.314 MeV

Results on kaonic nitrogen

ΔmK- = 60 keV


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.) eV


DEAR Results w

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


Next Steps

Goal: High precision X-ray spectrocopy with X-ray timing

New X-ray detectors SDDs: JRA in I3HP (EU FP6)in cooperation with LNF, MPG, PNSensor, Politecnico Milan, IFIN-HH

timing capability background suppression by using the kaon-X ray time correlation

excellent energy resolution high efficiency, large solid angle radiation hardness compact versatile design

New dedicated target-detector set-up

In the next stage of the experiment we expect an improvement in the signal / background ratio of ~ 2 – 3 orders of magnitude


SDD Structure

Detector produced at the MPI Halbleiterlabor, Munich, Germany

n

n+

p+ -V cc

p+

100

150

200

250

300

-60 -50 -40 -30 -20 -10 0 10 20

temperature [°C]

FW

HM

[e

V]

100 mm² SDD

typ. 10 mm²SDDnoise fit


Triple coincidence: SDDX * ScintK * ScintK

Scintillator

Scintillator

D2 gas

SD

D

e+

e-

K+

K-

X-ray

Triple coincidence: SDDX * ScintK * ScintK

Scintillator

Scintillator

D2 gas

SD

D

e+

e-

K+

K-

X-ray

Kaon – X-ray Coincidence

SDDs

e-

e+

Trigger scintillators not shown

X-ray detector array : ~ 200 SDDs 1 cm2 each


Monte Carlo: K-d with SDDs

Energy (keV)Energy (keV)

No timingSDD‚single‘

coinc.SDD * Scint * Scint

Backgroundsuppressionto < 10-3

Kaonic deuterium

K K

Ag K fluorescencelines (calibration)

Large SDD energy resolution tested: ~ 160 eV @ Mn(cooling to -120°C, voltage 200V)


Kaonic Helium @ KEK


Kaonic helium "puzzle"

Theory gives more than10 times smaller values

but


Kaonic L line X-ray spectrum

Monte Carlo Simulation104 K-He eventsand S/B ~ 4 ± 1.5 eV ± 4.4 eV

energy [keV]

nu

mb

er o

f ev

ents


What we can learn ?

Nature of S0(3115) state observed recently at KEK

Experimental information on anti-kaon – nucleon interaction

T. Suzuki, Phys. Lett. B597(2004) 263


Epilogue

"The most important experiment to be carried out in low energy K-meson physics today is the definitive determination of the energy level shifts in K-p and K-d atoms, because of their direct connection with the physics of the KN interaction and their complete independence of all other kind of measurements which bear on this interaction“

R.H. Dalitz

"Hadronic atoms are a wonderful tool to measure QCD amplitudes at threshold."J. Gasser, Proc. DAFNE04


Summary and Outlook

Final DEAR results on strong interaction shift and width in K-p: repulsive shift in K-p verified. smaller values and higher precision for shift and width. Kβ, Kγ line pattern observed for the first time.

Final DEAR results on strong interaction shift and width in K-p: repulsive shift in K-p verified. smaller values and higher precision for shift and width. Kβ, Kγ line pattern observed for the first time.

DEAR one of the first experiments at DAΦNE

First production of exotic atoms at DAΦNE shown

Measurements on kaonic nitrogen and finally kaonic hydrogen

Large SDDs and new set-up in progressNew experiments – physics program• Measurement of kaonic deuterium (first measurement ever)• Precision measurement of kaonic hydrogen (percent level). • Further perspectives: kaonic helium (He-3, He-4).

Precision measurement of charged kaon mass….

Large SDDs and new set-up in progressNew experiments – physics program• Measurement of kaonic deuterium (first measurement ever)• Precision measurement of kaonic hydrogen (percent level). • Further perspectives: kaonic helium (He-3, He-4).

Precision measurement of charged kaon mass….

SIDDHARTASilicon Drift Detectors for Hadronic AtomResearch by Timing Applications



Thank you

On the way to new precision experiments



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