27 - 31 October 2014 Trento, Italy

Measurements of kaonic 4He and 3He at DANE

Achievements and Perspectives in Low-Energy QCD with Strangeness

Diana Laura Sirghi

INFN-LNF

on behalf of SIDDHARTA collaboration

SIDDHARTASIlicon Drift Detector for Hadronic Atom Research by Timing Applications

the determination of the isospin dependent KN scattering lengths through a

~ eV measurement of the shift~ eV measurement of the shift and of the width

of the K line of kaonic hydrogen andthe first (similar) measurementfirst (similar) measurement of kaonic deuterium

The scientific aimThe scientific aim

Fundamental study of Fundamental study of strong interactionstrong interaction

between anti-K & nucleus at low energy limitbetween anti-K & nucleus at low energy limit

Fundamental study of Fundamental study of strong interactionstrong interaction

between anti-K & nucleus at low energy limitbetween anti-K & nucleus at low energy limit

The scientific aimThe scientific aim

SIDDHARTA measures the SIDDHARTA measures the X-ray transitionsX-ray transitions

occurring in the cascade processes occurring in the cascade processes

of kaonic atomsof kaonic atoms

In the framework of the SIDDHARTA experiment we have performed the measurements related with the Kaonic helium transition to the 2p level (L-lines):

- for first time in a gaseous target for 4He- for the first time ever for K3He

The interest for such type of measurement was rather high due to:

so-called “kaonic helium puzzle”

some theoretical predictions of possible very small energy shift

(if any)

Kaonic Helium measurements SIDDHARTA experiment

Kaonic Helium atomsKaonic Helium atoms

ε = E3d 2p (exp) – E3d 2p (e.m.)

The most suitable transition to observe the strong interaction effects

The most suitable transition to observe the strong interaction effects

The absorption is too strong to observe the radiative transition to 1s state

the last observable state is the 2p state

The absorption is too strong to observe the radiative transition to 1s state

the last observable state is the 2p state

Kaonic atom data (Z≥3)

Kaonic atom data (Z≥3)Used for studies of KbarN interaction

Optical model

Experimental X-ray data of shift & width:Well fitted with optical potentials

Expected shift of K-4He 2p state:ΔE ~ 0 eV

C.J. Batty et al., Physics Reports 287(1997) 385-445

The shift and widths of kaonic atom X-ray energy have been measured using targets with atomic numbers from Z=1 to Z-92, which provide very important quantities for understanding the antiKN strong

interaction.

There are discrepancies for:

Kaonic Hydrogen

(Z=1)

Kaonic Helium

(Z=2)

2p level shifts for 2p level shifts for Kaonic Helium atomsKaonic Helium atoms

E2p(eV) 2p (eV)

-41±33 -

-35±12 30±30

-50±12 100±40

-43±8 55±34

Kaonic helium atom data (Z=2)Kaonic helium atom data (Z=2)

1971

1979

1983

Averageof above

Kaonic helium atoms theoretical valuesKaonic helium atoms theoretical values

Shift (eV) Ref.

-0.13±0.02 Batty, NPA508

(1990) 89c

-0.14±0.02 Batty, NPA508

(1990) 89c

-1.5 Akaishi, Proc. EXA05

There are two types of theories compared to the experimental results:

Optical-potential model:

(theoretical calculations based on kaonic atom data with Z> 2)

Tiny shift(E2p 0 eV)

Recent theoretical calculations:

Akaishi-Yamazaki model of deeply-bound kaon-nucleus states

Predicts a possible maximum shift:E2p of ± 10 eV

What is What is Kaonic helium puzzle?Kaonic helium puzzle?

Need a new K-4He X-ray measurement!

Experiment:Large shift

(E2p 40 eV)

Theory:E2p 0 eV

or< ± 10 eV

New KNew K44He results by KEK PS E570He results by KEK PS E570

PLB 653 (2007) 387

E2p =2±2(stat.)±2(syst.) eV)

K4He 3d→2p: 1500 events

3x higher statistics2x better Energy resolution6x better S/N

Solving the kaonic helium puzzleSolving the kaonic helium puzzle

Old experiments:Large shift(-43±8 eV)

E570 experiment:Small shift

(+2±2±2 eV)

Theory:E2p 0 eV

or< ± 10 eV

Difference between the new and the old experiments

Experimental confirmation need!SIDDHARTA experiment

SIDDHARTA experimentSIDDHARTA experiment

Monochromatic, low-momentum kaon beam from DANE (127 MeV/c)

No hadronic background due to the beam line (compare with hadron beam line :e.g with KEK line)

Big advantages of the SIDDHARTA experiment:

•Low density gas target (higher yields of the atomic state in gaseous helium over the liquid one, due to the density dependent Stark mixing; negligible Compton scattering in helium).

•The availability of kaons with low energy and low momentum spread results in efficient kaon stopping in gas target.

•Silicon Drift Detector (SDDs) as detector

1515

xy

z

e-

510 MeV/c510 MeV/ce+

510 MeV/c510 MeV/c127 MeV/127 MeV/ccΔΔpp//pp=0.1%=0.1% K+

K-

Φ

TargetTarget

DetectDetectby SDDsby SDDs

Detect by Detect by two two scintillatorsscintillators

SIDDHARTA overviewSIDDHARTA overview

1 cm1 cm22 x 144 x 144 SDDsSDDs

Silicon Drift Detector - SDD Silicon Drift Detector - SDD

SDD Energy resolution: 150 eV (at 6 keV)

SDDs & SDDs & TargetTarget(inside (inside vacuum)vacuum)

Kaon Kaon detectordetector

SIDDHARTA setup SIDDHARTA setup

Kaonic Kaonic 44He dataHe dataSIDDHARTA experimentSIDDHARTA experiment

The Kaonic 4He X-ray data were taken for about two weeks in January 2009.

In this period, an integrated luminosity of about 20pb-1 was collected.

This corresponds to about 4.7 × 106 kaons detected by the kaon detector.

SDD spectrum of X-ray uncorrelated with kaon production.Ti and Mn X-ray peaks are produced by the 55Fe source in normal condition of beam

Energy resolution: FWHM (@6.4 keV): 151 ± 2 eV

Energy calibrationEnergy calibration

Target

Ti foil

Fe55

Degrader

K-He data taking

Triple coincidencesTriple coincidences

Background suppression more than

104

Energy spectrum of K-Energy spectrum of K-44He X-raysHe X-rays

Energy of K4He L (3d2p) line:

Eexp = 6463.6±5.8 eV

New results of K-New results of K-44He 2p level shiftHe 2p level shift

Eexp = 6463.6±5.8 eV Ee.m. = 6463.5±0.2 eV

E = Eexp – Ee.m. = 0±6(stat) ±2(syst) eV

Published in PLB 681(2009) 310-314

“kaonic helium puzzle” solved

SIDDHARTA’s results is consistent with the results obtained by E570 experiment

Summary of the K-Summary of the K-44He shiftsHe shifts

Data taking periods Data taking periods of SIDDHARTA in 2009of SIDDHARTA in 2009

DANE shutdown in Summer

New alignment of setupImprove S/N ratio

K-He3 data (~4days)

55Fe source: Good for reduce sys. error on K-4HeBad for “background” events on K-H,K-D

Removed 55Fe source in other data

e e

SDDs

Ti/Cu foil

X-ray tube

Data taking scheme at DAFNE

calibration data

e e

K

K

SDDs

degrader

Scintillators

Production data

Calibration data with X-ray tube have been collected under the beam condition in regular interval of the production runs.

For that purpose a remote controlled mechanism was built to move away the kaon detector and instead have the x-ray tube

in place.

SDD X-ray energy spectra

Cal

ibra

tion

data

with

X-r

ay t

ub

eCalibration Ti&Cu

e e

SDDs

Ti/Cu foil

X-ray tube

calibration data

Instead of Fe source, “X-ray tube” data taken

Estimated systematic error ~ 3-4 eV

In-beam

X ray tube

Ti, Cu foils

SDD X-ray energy spectra

Cal

ibra

tion

data

with

X-r

ay t

ub

eN

ot

corr

elat

ed t

o

Kao

n si

gnal

s

Pro

duct

ion

data

Energy scale determinedby X-ray tube data

Energy spectrum withuncorrected to kaon timing[Fig. (b)]

ee

K

K

X-ray SDDs

degrader

Scintillators

ee

K

K

X-ray SDDs

degrader

Scintillators

Calibration Ti&Cu

providing large statistics background events + X-Ray lines form the target maetrials induced

by the beam background

SDD X-ray energy spectra

Cal

ibra

tion

data

with

X-r

ay t

ub

eN

ot

corr

elat

ed t

o

Kao

n si

gnal

sS

elec

ted

with

K+

K-

& S

DD

tim

ingPro

duct

ion

data

Kaon detector

Time difference between SDD & Kaon detector

providing kaonic atom X-ray energy spectra with a high background suppression.

SDD X-ray energy spectra

Cal

ibra

tion

data

with

X-r

ay t

ub

eN

ot

corr

elat

ed t

o

Kao

n si

gnal

s

Pro

duct

ion

data

The shift is due to the instability of our electronics caused by differing conditions between the production and X-ray tube data.The largest contribution is a rate-dependent effect on the SDDs.The hit rate of the SDDs in the X-ray tube data was about 10 times higher than that in the production data, causing the observed shift.

High rate

Low rate

High rate

Low rate

The X-ray peak fit

The accuracy of the energy scale was determined by using X-rays energis of the TiKa, CuKa and Au La lines.The intensities of these X-ray lines in the kaonic helium data were not high enough to observe systematic effects on the energy calibration and energy resolution of the SDDs, so the data measured with the deuterium target, which were taken for about 20 days, were also analyzed using the same method.

Natural line widths taken into account

X-ray peaks are fitted with Voigt function

Determination of the accuracy of the energy scale of the SDDs: using production data not correlated with the kaon signal

The peak position

The vertical axis gives the difference between the fit values and the reference data.

Result of the fit:energy scale in the production data is shifted by −6 eV compared to the reference data.

The accuracy of the energy determination was ±4 eV in the energy region from 4 keV to 10 keV.

The variation of ±4 eV corresponds to the uncertainty of about ±0.2 channels in the analogue-to-digital converters (ADCs) used in the measurements. The variation could be related to the nonlinearity of ADCs.

The uncertainty of ±4 eV is taken as a systematic error in the energy determination.

DAFNE shutdown in Summer

Kaonic Kaonic 33Helium data SIDDHARTA experimentHelium data SIDDHARTA experiment

The Kaonic- 3He X-ray data were taken for about 4 days in November 2009.

In this period, an integrated luminosity of about 16 pb-1 was collected.

The Kaonic-The Kaonic-33He caseHe case

TransitionKaonic-3He e.m.

(eV)(*)

3d->2p 6224

4d->2p 8399

5d->2p 9406

There are NOT previous experiments done for the X-ray measurements for Kaonic- 3He

Planned experiments: SIDDHARTA (done);

E17 (to be done)

(*)Zeitschrift fur Physik D 15 (1990) 321

Kaonic Helium-3 energy spectrumextraction of the strong interaction shift

Eexp=6223.0±2.4(stat)±3.5(syst.) eV

Ee.m.=6224.6 eV

The calculation of the e.m. energies for kaonic 3He was done using the Klein –Gordon equation and the vacuum polarization from the first order term of the Uehling potential.

ε=ΔE2p= Eexp-Ee.m. = -2±2(stat)±4(syst)

World First ！Observation of K-3He X-rays

Determination of strong-interaction shift

PLB 697 (2011) 199. Cited 13 times

Target material: Kapton Polymide (C22H10N2O5)

DANE shutdown in Summer

K-4He (3d-2p)

eV)(4)(352 sysstaE p

More date on K-More date on K-44He 2p level shiftHe 2p level shift

2p level widths for 2p level widths for Kaonic Helium atomsKaonic Helium atoms

Experimental results for the widths Experimental results for the widths of kaonic helium atomsof kaonic helium atoms

Average:

Theory: -0.13+-0.02 1.8+-0.05

Nuclear Physics A392 (1983) 297-310

“The shift measurements are seen to be in good agreement. The situation for the width values is much less satisfactory and theerror bars of the two measured values do not overlap. The error on the quoted average has been taken from the external variance of the measured values.”

New experiment for the widths of the 2p state for kaonic helium: SIDDHARTA experiment

Uncertainty of detector resolutionUncertainty of detector resolution

Due to the strong correlation between the detector resolution and line width of KHe, the detector resolution was fiexd form the production data not correlated with the kaon signal

Since all the positions are located within the error curves, the error is taken as the accuracy of the determination of the dector resolution for the fit of the kaonic helium X-rays.

3d→2p = (65.4±2.3) eV

K-3He

3d→2p = (66.4±2.3) eV

K-4He

The energy dependence of the energy resolution of the SDDs: evaluated from the widths of the peaks of Ti, Cu and Au

The deviations from the fit file are plotted for

each target material

Results for the widths of K-3He and K-4HeResults for the widths of K-3He and K-4He

The energy shift and broadening of the 3d→2p transition can be obtained from the peak fit using a Voigt Function V=V(, ), where represents the strong-interaction 2p width and was fixed using the values obtained from the energy resolution of the detector.

The systematic error was evaluated from the uncertainity of the resolution .

In addition, since the K-3He peak partially overlaps the K-O transition, the systematic error of the width of K-3He includes the uncertainity of its intensity.

Summary of the results

Experiment Target Shift [eV] Reference

KEK E570 Liquid +2±2±2 PLB653(07)387

SIDDHARTA (He4 with 55Fe) Gas +0±6±2 PLB681(2009)310

SIDDHARTA (He4) Gas +5±3±4 arXiv:1010.4631,

PLB697(2011)199SIDDHARTA (He3) Gas -2±2±4

*error bar 22 )()( syststat

Results for the shifts and widths Results for the shifts and widths of K-3He and K-4Heof K-3He and K-4He

• The large shift and width obtained by the experiments done in 70-80 was not observed in kaonic 3He and 4He.

• The results for shift and width agree with the theoretical calculations.

• No abnornally large shift abd width were found.

L-series X-ray yields ofL-series X-ray yields ofKaonic Helium atoms in gaseous Kaonic Helium atoms in gaseous

targetstargets

By using accurate Monte Carlo simulations, the absolute yields of the kaonic 3He and 4He X-ray transitions to the 2p state was successfully determined by the SIDDHARTA experiment .

The measured yields provide information for understanding the cascade processes of kaonic helium atoms as a function of the target density.

L-series X-ray yields ofL-series X-ray yields ofKaonic Helium atoms in gaseous targetsKaonic Helium atoms in gaseous targets

The absolute X-ray yield is defined as the X-ray intensityper stopped kaon.

The X ray detection efficiency is defined as the number of measured X-rays normalized by the number of K+K− events recorded in the kaon detector :

Comparing these efficiencies to those given by Monte Carlo simulations, the absolute yields of the kaonic atom X-

rays can be determined.

(*) C.E. Wiegand, R. Pehl, Phys. Rev. Lett. 27, 1410 (1971).(**) S. Baird et al., Nucl. Phys. A 392, 297 (1983).

• The yields of the Lα lines in gas are about 2.0–2.5 times higher than in liquid• The yields of the Lβ and Lγ lines are consistent. •The intensities of the Lhigh lines in gas are obviously higher than those in liquid.

These yield differences are related to the density dependence of the cascade processes, such as the molecular Stark effect and molecular ion formation.

D (2.50 g/l)

3He (0.96 g/l)

4He (1.65 g/l)

4He (2.15 g/l)

The absolute X-ray yield (Y ) per stopped K−:In performing the comparison, the normalization was done using the number of K+K− events detected by the kaon detector.

ConclusionsConclusions SIDDHARTA experiment measured the kaonic helium 3d2p transitions:

for the first time ever for 3He.

for the first time in a gaseous target for 4He

Shift and width are founded to be few eV both in K-3He and K-4He

No abnormally large shift and width were found in K-3He and K-4He

These results agree with theoretical calculations

The kaonic helium puzzle was solved for shift and width both K-3He and K-4He.

These results agree with theoretical calculations

The absolute X-ray yields of L-series lines were determined for the first time

DANE proves to be a “ideal” kaonic atom “factory”.

Future plansFuture plans

The upgrade of the SIDDHARTA experimental setup

Precise measurements for the X-ray transitions for kaonic deuterium.

Measuring, with higher precision, the X-ray transitions for Kaonic 4He and Kaonic 3He to the 2p level and the first tempt to get the transitions to the 1s level.

SIDDHARTA 2 experiment

Kaonic atoms data (Z>3)Kaonic atoms data (Z>3)

The shifts and widths for kaonic atoms with Z≥3 are systematically well understood;

The optical model expressing the kaonic atom data have been used for calculation of the antiKaonN interaction.

C.J. Batty et al., Physics Reports 287(1997) 385-445

The shift and widths of kaonic atom X-ray energy have been measured using targets with atomic numbers from Z=1 to Z-92, which provide very important quantities for understanding

the antiKN strong interaction.

There are discrepancies for:

Kaonic Hydrogen

(Z=1)

Kaonic Helium

(Z=2)

See talk of A. Romero Vidal

DAFNE shutdown in Summer New alignment of setupImprove S/N ratio

K-He3 data (~4days)

55Fe source: Good for reduce sys. error on K-4HeBad for “background” events on K-H,K-D

Removed 55Fe source in other data

Data taking periods Data taking periods of SIDDHARTA in 2009of SIDDHARTA in 2009

X ray energy (keV)

Cou

nts

/ bin

KH

e (3

-2)

KC

(6-

5)

KH

e (4

-2)

transition e.m.energy events(3-2) 6.464 1047 ± 37(4-2) 8.722 154 ± 21(5-2) 9.767 91.8 ± 19(6-2) 10.333 82.4 ± 25higher < 11.63 131 ± 41

Ti K

KHe used forgasstop optimization+ physics interest1)

data from setup 2(no Fe55 source)

1) compare KEK E570KHe L lines in liquid He,consistent result,first measurement in gas

KH

e (5

-2)

KN

(5-

4)

KH

e L h

igh

p r e l i m i n a r y

KC

(5-

4)

KH

e (6

-2)

KO

(6-

5)

KO

(7-

6)

Higher statistics of the K-4He L lines (L, Lβ, L)

Smaller statistics in shift, determination of width

X-ray yield information in gas (for the first time)

Very preliminary K-Very preliminary K-44He spectrum He spectrum

e e

SDDs

Ti/Cu foil

X-ray tube

Data taking at DAFNE -Calibration

calibration data

Estimated systematic error ~ 3-4 eV

Seminar TUM, 27 June 2011

e e

K

K

SDDs

degrader

Scintillators

Production data

Data taking at DAFNE - Production

Seminar TUM, 27 June 2011

X ray energy (keV)

Cou

nts

/ bin

KH

e (3

-2)

KC

(6-

5)

KH

e (4

-2)

KC

(5-

4)

transition e.m.energy events(3-2) 6.224 1209 ± 40(4-2) 8.399 220 ± 22(5-2) 9.406 90.0 ± 18(6-2) 9.953 65.8 ± 24higher < 11.4 397 ± 40

Ti K

KHe3never measured before !

KH

e (5

-2)

p r e l i m i n a r y

KH

e L h

igh

KH

e (6

-2)

KO

(6-

5)

KN

(5-

4)

KO

(7-

6)

Very preliminary K-Very preliminary K-33He spectrumHe spectrum

The statistical error for the transition 3d2p in K 3He is less than 3 eV.

Target Shift [eV]

KEK E570 Liquid +2±2±2 eV

SIDDHARTA (w/ 55Fe) Gas +0±6±2 eV

SIDDHARTA (New) Gas +5±3±4 eV

Comparison of results

Target Shift [eV]

SIDDHARTA Gas -2±2±4 eV

J-PARC E17 Liquid planned

..exp2 mep EEE

Kaonic 4He 2p level shift

Kaonic 3He 2p level shift

shift),"repulsive("0

),"attractive("0

2

2

shiftE

shiftE

p

p

Conclusions (2)Conclusions (2)

Confirmed the small shift obtained by recent experiment E570 for Kaonic 4Helium

The “kaonic helium puzzle” for Kaonic 4Helium is now solved

The preliminary analysis of the 3d2p transitions for Kaonic 3Helium, indicate that the statistic error shift is less than 3 eV.

e e

SDDs

Ti/Cu foil

X-ray tube

Data taking scheme at DAFNE

calibration data

e e

K

K

SDDs

degrader

Scintillators

Production data

Instead of Fe source, “X-ray tube” data taken

Estimated systematic error ~ 5 eV

- rebuilding of the sdds mounts: gain of solid angle of X ray detectors- replacement of sdd modules: 144 cm2 detectors operational- new upper kaon detector: less material in vicinity of target, clean trigger- improved shielding: new multimaterial and more narrow collimator

Setup improvements during summer 2009 shutdownSetup improvements during summer 2009 shutdown

Recent theoretical calculation for the Recent theoretical calculation for the width of kaonic helium atomswidth of kaonic helium atoms

theoretical calculations ofphenomenological optical

potential model by Friedman

Akaishi-Yamazaki model of deeply-bound kaon-nucleus states

Small width(E2p 2 eV)

Possible large width 5eV

K-4He K-3He

Contamination of K-O peakContamination of K-O peak

Several small peaks were observed in all the spectram which originated from kaonic atom X-rays produced in the target window material (C22H10N2O5)

The X-rays peaks are: (K-C) 6→5

(K-O) 7→6,(K-C) 6→5

(K-N) 6→5

(K-C) 8→6

Kaonic Helium atomsKaonic Helium atoms

p d f

3d 2p X ray

E2p (exp.)

n

4

3

2

Strong Interaction causes:energy shift

of the last energy levels form their purely electromagnetic

values AND

level width finite lifetime of the state

corresponding to an increase in the observed

level width

electromagnetic cascade

K- stopped in He

Repulsive type

Attractive type

Kaonic Helium atom: last orbit 2p

E2p (e.m.)

The experimental setupThe experimental setup

Target size: r = 72 mm height = 155 mm

For He3: Temp. of gas: 20K

Pressure: 1 bar

Installed SDD: 144 cm2

SDD operation temp: 170 K

SDD Energy resolution: 150 eV (at 6 keV)