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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
DANE 04 / JZ
ContentContent
Motivation of DEARExperimental set-upFeatures of the experimentData analysisKaonic nitrogen measurementResults on kaonic hydrogenSummary
DANE 04 / JZ
• 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
DANE 04 / JZ
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
DANE 04 / JZ
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
DANE 04 / JZ
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)
DANE 04 / JZ
Setup at DASetup at DAΦΦNENE
DANE 04 / JZ
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
DANE 04 / JZ
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
DANE 04 / JZ
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
DANE 04 / JZ
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
DANE 04 / JZ
Kaonic Hydrogen X-ray spectrumKaonic Hydrogen X-ray spectrum Raw spectrum – bremsstrahlung background fitted with cubic function
DANE 04 / JZ
Resulting KResulting K--p Spectrump Spectrum(all background fit-components subtracted)(all background fit-components subtracted)
DANE 04 / JZ
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
DANE 04 / JZ
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.
DANE 04 / JZ
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
DANE 04 / JZ