First measurement of kaonic hydrogen and nitrogen X-rays at DA NE J. Zmeskal Institute for Medium Energy Physics, Vienna for the DEAR Collaboration LNF.

First measurement of kaonic hydrogen First measurement of kaonic hydrogen and nitrogen X-rays at DAand nitrogen X-rays at DANENE

J. Zmeskal Institute for Medium Energy Physics, Vienna

for the DEAR Collaboration

LNF – IMEP - INFN Trieste - Univ. Fribourg - Univ. Neuchâtel – RIKEN – Hokkaido Univ. - Univ. Tokyo - Univ. Victoria

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ContentContent

Motivation of DEARExperimental set-upFeatures of the experimentData analysisKaonic nitrogen measurementResults on kaonic hydrogenSummary

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• Exotic (kaonic) atoms – probes for strong interaction hadronic shift ε1s and width Γ1s directly observable experimental study of low energy QCD

• Kaonic hydrogen K-p simplest exotic atom with strangeness kaonic hydrogen „puzzle“ solved – but still: precision data missing kaonic deuterium never measured before atomic physics: new cascade calculations (to be tested !)

• Information on (1405) sub-threshold resonance important for research on deeply bound kaonic states

• Determination of the isospin dependent KN scattering lengths

no extrapolation to zero energy

MotivationMotivation

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Kaonic HydrogenKaonic HydrogenNegative 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>1are negligible

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Experimental Set-upExperimental Set-up

TMP

CCD Electronics

Vacuum Chamber

APD Cryo-Cooler

Target Cell

CryoTigerCCD Cooling

CCD Pre-Amplifier

CCD55-Chips

e+ e-volume: 1150 cm3 cryogenic H2 gas fillingside wall: 75 µm Kaptonentrance window: 125 µm Kaptongrid structure: glass fiber reinforced epoxy

Energy measurement ofkaonic K lines with an array of 16 CCD X-ray detectors

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CCD Detector ArrayCCD Detector ArrayArray of 16 CCD-55 chips- pixels format 1242 x 1152- pixel size 22.5x22.5 µm- total area per chip 7.24 cm2

- depletion depth ~30 µm- read-out time per CCD ~ 90 s- energy resolution ~140 eV (5.9 keV Mn-55 K line)

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Setup at DASetup at DAΦΦNENE

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Features of the ExperimentFeatures of the Experiment Nearly mono-energetic kaons from decay

(pion-induced background largely suppressed compared to proton accelerator)

Light weight target for low X-ray background

Carefully chosen structure materials

(checked by different analysis methods)

Optimized gas density for high X-ray yield

(cryogenic gas target)

CCD array for X-ray detection (16 CCD-55, large area 116 cm2, pixel analysis for background reduction,

excellent resolution)

Multilayer shielding for background reduction

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Experimental DataExperimental Data

Kaonic Nitrogen 3.-29.04.2002 ca. 9000 × 16 files (160GB)

14.2 pb-1 => 20.5 × 106 K-

Kaonic Nitrogen 6.-28.10.2002 ca. 7000 × 16 files (112GB)

17.4 pb-1 => 25.1 × 106 K-

Kaonic Hydrogen: 30.10.-16.12.2002 ca. 18000 × 16 files (288GB) 58.4 pb-1 => 84.1 × 106 K-

Hydrogen, 16.-23.12.2002 ca. 2600 × 16 files (42GB)no collisions

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Results on Kaonic NitrogenResults on Kaonic NitrogenThesis T. Ishiwatari (IMEP), Phys. Lett. B in press

3 X-ray transitions

Extraction of the transition yields

Impact on cascade calculations

Kaonic nitrogen high precision measurement of the charged kaon mass

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Kaonic Hydrogen Data AnalysisKaonic Hydrogen Data Analysis

Components of the X-ray spectra:

• Continuous background due to bremsstrahlung

• Fluorescence lines from structure materials

• Kaonic X-ray lines (only in H)

Procedure:

• Fit of the continuous background

• Disentangling of the kaonic Kα line from the Kα fluorescence iron line

• Testing the sensitivity of different input for the K(n>4) lines

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Kaonic Hydrogen X-ray spectrumKaonic Hydrogen X-ray spectrum Raw spectrum – bremsstrahlung background fitted with cubic function

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Resulting KResulting K--p Spectrump Spectrum(all background fit-components subtracted)(all background fit-components subtracted)

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Results on the Shift and WidthResults on the Shift and Width

Shift: 1s = - 194 ± 37 (stat.) ± 6 (syst.) eV

Width: 1s = 249 ± 111 (stat.) ± 30 (syst.) eV

aK-p = – 0.466 (± 0.104) + i 0.299 (± 0.174) fm

Combined results => preliminary DEAR averageto be published in Phys.Rev.Lett.

2 independent analyses starting from the raw datagiving consistant results

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DEAR ResultsDEAR Results (preliminary)(preliminary) 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 attractive

KpX (KEK)M. Iwasaki et al, 1997

=

- 3

23 ±

63

± 11

eV

=

407

± 2

08 ±

100

eV

New theoretical studies:Ivanov et al. 2003 / 2004Meißner, Raha, Rusetsky 2004

DEAR prelim.

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SummarySummary

Preliminary results on strong interaction shift and width:

repulsive shift in K-p verified

smaller values and better precision for shift and width

Kβ, Kγ resolved for the first time

future high precision measurements on kaonic atoms are feasible

DEAR one of the first experiments at DAΦNE

First production of exotic atoms at DAΦNE

Measurements on kaonic nitrogen and kaonic hydrogen

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