ANKEANKE, a magneticspectrometeranddetectionsystemat aninternal

targetpositionof COSY, allows to separateandmo-

mentumanalyzeejctiles from the circulating COSY beamwith forward emissionanglesaround0 . Due to its largesolid angleandwide momentumacceptanceANKE canbeusedfor a varietyof experimentalstudies.Currently, theex-perimentalprogramat ANKE focuseson:1. K - (and later K -) mesonproductionin the nuclearmedium.2. Investigationof thelight scalar resonances a0

f0 980 .

3. Study of the proton induceddeuteron breakup at highmomentumtransfer.4. Measurementof neutralmeson(π0, η, ω, . . . ) productionin proton-neutron collisions.The detectionsystemsof ANKE have beenextendedby anegative particledetectorwhich is optimizedfor K -mesondetection.It has beenusedin a test beamtime in spring2002 during which the productionof φ-mesons has beenmeasuredin pp interactionsfor the first time at COSY.Furthertechnicaldevelopmentsfor ANKE comprise:a. An atomic beam source (ABS) which, togetherwith astoragecell, can be usedas a polarizedinternal target fordoublepolarizationexperiments.b. A frozen pellet target for investigationat highestlumi-nosities, 1032cm 2s 1.c. Target-nearsolid state detectors which will be installedinsidethevacuumpipeof COSYfor spectator tagging.d. An electromagnetic calorimeter which will allow tomeasurephotonsfrom, e.g.,decayof neutralmesons.

Range telescopesfor K + identification

TargetD1

D2

D3

1 m

COSYbeam

Side wallcounters

Forwarddetectors

Backwarddetectors

Negative particledetectors

Fig. 1: Sketchof ANKE andthedetectionsystems.

K -meson production in the nuclear mediumThedesignof ANKE andits detectionsystemshavebeenop-timizedto measuretheproductionof K -mesonswith smallcrosssectionsin a hugebackgroundof other particles.Asa first setof experiments,the productionof K -mesonsinpA (A C, Cu, Ag, Au) hasbeeninvestigatedby inclusivemeasurementsof doubledifferentialK spectrain thebeam-energy rangeTp 1 0 2 3 GeV. The dataat the lowestbeamenergies,farbelow thefreenucleon-nucleonthresholdat 1.58GeV, reveala high degreeof collectivity in thetargetnucleus.Basedon simple kinematicalargumentsit can beshown that theintrinsic momentaof thenucleonsparticipat-ing in the reactionmustbe large(up to 550MeV/c if thekaonsareproducedin a singlecollision betweenthe beamproton andone nucleon).Alternatively, more than one nu-cleonat restmusttake part in the reaction,i.e. the effectivetarget massmustbe up to 6mN. For a detailedunderstand-

ing of the processesleadingto subthresholdK productionmicroscopicmodelcalculationsareunderway.Anothermajorresultfrom theinclusivemeasurementsis thatthedataoncrosssectionratiosfor K productionondifferenttargetnucleiallow to determinethenuclearK potential(orthe“in-mediummass”)atnormalnucleardensityρ ρ0. Asanexample,Fig. 2 shows thecrosssectionratio Au/C mea-suredwith ANKE in themomentumrangepK 150 600MeV/c. For all beamenergiesbetween1.5 and2.3 GeV the

Cro

ss s

ectio

n ra

tio (

Au/

C)

2

6

10

14Coulombrepulsion

Nuclearpotential

VK+ = 0

20 MeV

K+ momentum (MeV/c)100 300 5000

Fig. 2: Crosssectionratio Au/C for proton-inducedproduc-tion of K mesonsmeasuredat a beamenergy ofTp 2 3 GeV (greencircles).Theeffectof therepul-sive Coulombandnuclearpotentialsis indicatedbythe lines which arethe resultsof modelcalculationswith a CBUU transportcode(dashed- no potentials,darkblue- only Coulomb,red- nuclearpotentialforkaons,nucleons,andΛ hyperontakeninto account).

ratiosexibit similar shapes,rising with decreasingkaonmo-mentapassinga maximumandfalling down towardslowermomenta.This peculiarshapecouldbeexplainedby a com-bined effect of repulsive Coulomb and nuclearpotentialswhich the K “see” in the nuclearenvironment.This is il-lustratedin Fig. 2 by the lines representingthe resultsof amodel calculation.Without any potentials(light blue line)the amountof producedkaonswould steadilyrise towardslower momenta— dueto strongerrescatteringprocessesinthe heavy Au nucleuswhich tend to slow down the kaonsoncethey are produced.When a nuclearkaon potentialofV0

K 20MeV is used(andtakinginto accounttheabsorptionof theincidentprotonby includingabaryonpotentialinto thecalculations)a reasonableagreementwith theexperimentisachieved,with a maximumcloseto the experimentalvalueof 245 5MeV/c (red line). More refined model calcula-tionswill permitusto achieveanimproveddescriptionof theshapesof themeasuredspectraandto determinethenuclearK potentialwith anaccuracy of betterthan3 MeV. It shouldbe notedthat studiesof the nuclearpotentialscruicially de-pendon the detectionof low momentumkaons,which cur-rently is only possibleat ANKE.Thesecondphaseof theexperimentalprogramonin-mediumK -productionhasstartedin fall 2001with a testmeasure-menton (K p) and(K d) coincidences.For the first time,thesedataallow to draw direct conclusionsaboutthe K -productionmechanisms.As an example,Fig. 3 shows themomentumspectraof deuteronsproducedin coincidencewith kaonsat a beamenergy of 1.2 GeV. The upperspec-trum, obtainedin the full angular-momentumacceptanceofANKE, revealsa prominentpeakat pd 960 MeV/c. This

dN/d

Ω (

arb.

units

)

Deuteron momentum (MeV/c)400 800 1200

0

4

8

12

16

cluster?(backward)

cluster?(forward)

0

10

20

30

40

p(2N) → dK +Λ

pN1 → dπ πN2 → K+Λ

coalescentbackground

ϑd < 4° pK < 400 MeV/c

ϑd < 8° pK < 600 MeV/c

Fig. 3: Momentumspectrumof deuteronsfrom the reactionp 1 2 GeV C dK X (green circles). The up-per spectrumis obtainedin the full ANKE angular-momentumacceptance,whereasthe lower for re-stricteddeuteronanglesandkaonmomenta.Accord-ing to phase-spacesimulations,thesecutsshouldsup-pressthe eventsfrom two-stepK production.Twopeaksremainwhicharepossiblydueto productionofkaonson (2N) clusters,p 2N dK Λ.

agreeswith modelpredictionsfor deuteronsproducedin theparticulartwo-stepmechanismpN1 dπ, πN2 K Λ. Ourdatashow that this processcontributesto about30% of thetotal kaonyield at this beamenergy. A hint on moreexoticprocessescomesfrom theobservationthatthedeuteronpeakhasa width of about350 MeV/c, thus significantly largerthanthevalueof 200– 250MeV/c expectedfor the“normal”two-stepprocess.It canbe presumedthat this is dueto twosmallerpeaksat bothsidesof thecentralone,which canbeattributedto theproductionof K -mesonson a two-nucleoncluster, i.e. p 2N dK Λ. A correspondingfit to thedatawith threeGaussiansis shown in the upperpart of Fig. 3.According to phase-spacesimulations,the K (deuterons)from the clustermechanismshouldhave smallermomenta(emissionangles)thantwo-stepkaons.Thus,afterapplyingsuchconditionsto the dataone expectsa strongreductionof the central (pN1 dπ) peak,whereasevents from thecluster mechanismshould remain largely unaffected.Thisexpectationis confirmedby the lower spectrumof Fig. 3for restrictedkaonmomentaanddeuteronangles.Thusthetwo peaksmight be attributed to kaon productionon (2N)clusterwith forwardandbackwardemission(in cms)of thedeuteron.Furthercorrelationmeasurementsaimingat a bet-ter understandingof thedifferentmechanismshavebeenap-proved by the COSY-PAC and are scheduledfor summer2003.

A proposalto studyK K -productionin pA collisionsis inpreparation.Thesemeasurementswill make useof the newdetectionsystemfor negatively chargedejectiles(seebelow)

whichhasbeencommissionedin 2002.Goalof thisproposalis notonly to studymediumeffectsontheK -mesonbut alsoto measurethe target-massdependenceof φ-mesonproduc-tion. Several theoreticalpublicationpredicta significantin-creaseof theφ-decaywidth in nuclearmatter, dueto astrongactractive K potentialin nuclei (i.e. a significantlysmaller“in-mediummass”).

Study of light scalar resonances at ANKEThe lightestscalarresonancesa0 980 and f0 980 aretwowell establishedstatesin theexcitedmesonspectrum.How-ever, their interpretationasconventionalqq statesis by nomeansundisputed.In spiteof avarietyof dataontheproduc-tion of thea0

f0 with electromagneticandhadronicprobes,

their natureis still in doubtandthe variousscenariosabouttheir structureallow to describethedataequallywell. Thus,anexperimentalprogramusingtheANKE spectrometerhasbeenstartedaimingat complementarydatafrom pp, pn, pdanddd interactionscloseto theKK threshold.The a0 has isospin 1 and three charge states 1, 0, 1,whereasthe f0 has isospin and charge 0. From a test ofisospinrelationsin hadronicreactions,e.g. pp da0 vs.pn da0

0 or pd 3H a0 vs. pd 3Hea00, valuablein-

formationaboutthe structureof the a0 and f0 andpossiblyabouta0- f0 mixing canbe expected.This isospinviolatingmixing may be significantly larger than in the caseof π0

andη mesons.In this context thereactionsdd 4Hea00

f0

areof specialrelevance,sinceonly the isospin0 state( f0)canbe produceddirectly dueto isospinconservation.Thustheobservationof the reactiondd 4He f0 4He a0

0 4He π0η maybeadirectindicationof a0- f0 mixing.First measurementsof a0 resonanceproductionin thereac-tion pp da0 have beenperformedin 2001at Tp 2 65GeV (Q 46 MeV excessenergy above the KK threshold)and2002at Tp 2 83 GeV (Q 103 MeV). Both experi-mentsaimat thesimultaneousmeasurementof thetwo maindecaychannelsa0 K K

0andπ η. Theanalysisof there-

actionp 2 65GeV p dK K0

hasbeenfinalized;thetotalcrossseectionfor this reaction(seeupperpart of Fig. 4) aswell asmassandangulardistributionshavebeenobtained.It is a priori not clearwhich fraction of the observed pp dK K

0eventscan be ascribedto resonantKK-production

via thea0 . Thelinesin theupperpartof Fig. 4 correspondtoa modelpredictionfor resonant(redsolid) andnon-resonant(bluedashed)KK-production.Accordingto this model,res-onantproductionis dominant,however, theKd final-statein-teractionis not yet taken into accountin this approach.Themodelalsopredictsthatthenon-resonantKK-pairsaredom-inantly in a relative P-wave whereaskaonsfrom a0 -decaymustbein anS-wave.The possible different angular-momentumconfigurationsshouldbe reflectedin the shapeof the invariantmassdis-tribution of theKK-pairswhich is shown by the lines in thelower part of Fig. 4. Our dataclearly favor dominanceofS-waveKK-production.Ontheotherhand,themeasuredan-gulardistributions(not shown here)cannotbe explainedbypurea0 -resonanceproduction.This indicatesthatfor acom-pletedescriptionof thedataalsotheKd final-stateinteraction(mediated,e.g.,by theΛ(1405))hasto betakeninto account.

Observation of K - and φ-mesonsThe ANKE spectrometerdipole D2 leavesroom for the in-

Tota

l cro

ss s

ectio

n (n

b)dσ

/dm

(nb/

(MeV

/c2 ) )

Excess energy (MeV)

m(K +K0) (MeV/c2)

20 1000.1

_

1.2

0.8

0.4

0950 1000 1050

! #"%$&$

')( +*,(38±2±10) nb

10

1000

pp → ppK +K-

-.0/!1pp → dK +K0

_

Fig. 4: Upper Total cross section for the reaction pp dK K0 from ANKE and model predictionsfor theresonant(i.e. via the chain pp da0 dK K0,red line) and non-resonantcontributions (blue). Forcomparisonthecrosssectionsfor thereactionspp ppK K from COSY-11andDISTO arealsoshown.Lower: InvariantK K0 massdistribution. The linesshow phase-spacebehavior for a relative S

P-wave

of theK K0 pair (red/blue).

stallationof adetetectionsystemfor negativelychargedejec-tiles.Thefinal setupof thedetectorelements— partially in-sidethe returnyoke of D2 (Fig. 1) — andthe readoutelec-tronicshasbeenfinalizedin summer2002.The systemcandetectnegatively chargedpionsandkaons.In combinationwith the positive detectionsystem,reactionslike φ-mesonandK K -pair productionon elementaryaswell ason nu-cleartargetscanbeinvestigated.The first experimentusingthesedetectorsforeseesto mea-surethenear-thresholdφ-productioncrosssectionin pp col-lisionsby detectingtheK K decaymode.In spring2002afirst weekof beamtime at anexcesseneryof Q 35 MeVwastaken.Thedataanalysisstill is in progress,asa first re-markableresultwe show in Fig. 5 theinvariantK K -massspectrumwith aclearpeakaroundtheφ mass.Thisis thefirstobservationof φ-mesonproductionin pp collision at COSY.The measurementswill be continuedin 2003at differentQvalues.The pp ppφ datafrom ANKE may lead to a betterun-derstandingof this reactionnearthreshold.In addition,theywill provide — togetherwith existing datafor the reactionpp ppω from SPES-IIIandTOF — thecross-sectionra-

dN/d

m (

arb.

uni

ts)

Invariant K +K- mass (MeV/c 2)960 1000 1040 10800

10

20

30

40 φ(1020)

∆m ≅ 10 MeV/c2

(FWHM)

Fig. 5: InvariantK K massdistributionmeasuredatANKEfor the reactionp 2 7GeV p ppφ. The enhance-mentat lower massesis due to misidentifiedK π events.

tio Rφ 2 ω σφσω. Under the assumptionthat the Okubo-

Zweig-Iizuka(OZI) rule is fulfilled andusingαv 3 7 asthe deviation from the ideal SU(3) ω-φ mixing angle,oneexpectsROZI tan2 αv 4 2 3 10 3. A deviation from thisvaluemight be a hint on intrinsic strangenessin the protonor on the importanceof higher-orderrescatteringprocessesleadingto φ production.Theeventsshown in Fig. 5 wereobtainedby detectingonlytwo coincidentparticles,i.e. the K K -pair. This demon-stratesthefeasibility to measureat ANKE φ-mesonproduc-tion also in proton-nucleusreactions,without detectionofa third coincidentparticle.A correspondingproposalis inpreparation.Anotheralreadyapprovedproposalaimsat theinvestigationof theneutralscalarresonancesa0

0 and f0(980)in pn dK K reactions.Thesedatawill alsobe usedtostudy φ-mesonproductionon the neutron,i.e. the reactionpn dφ.

ω-meson production on the neutron and spectator coun-tersR.Schleichert,1

2 page

Deuteron breakupF. Rathmann,1 page

The Polarized Internal Target (PIT)Many few-nucleoninteractionstudiesbenefit significantlyfrom experimentsinvolving spin-degreesof freedom.Whilein a standardcross-sectionexperiment,only a singleobserv-able is probed,additional observablesbecomeaccessible,wheneitherbeamor target, or wherever possible,both arepolarized.It shouldbe emphasizedthat after closingof theCooleroperationat IUCF in 2002,COSY remainsthe onlyring capableof storingpolarizedprotonsanddeuteronsona worldwide scale.For state-of-the-artspin-physicsexperi-mentsin thehadronicsectorwith polarizedbeamsat COSY,apolarizedinternaltarget(PIT) is presentlybeingdevelopedfor ANKE. Besidesour development,only oneotherPIT ispreparedin the electromagneticsectorfor the physicspro-grammeof theBLAST facility at MIT-Bates.Thesetwo tar-getswill allow for complementarystudiesusingbothpolar-izedelectromagneticandhadronicprobesin thefuture.

Thepolarizedatomicbeamsource,which will feedthePIT,is depictedin Fig. 6. The sourceprovidesa beamintensi-tiesof 7

4 4 5 1016 atoms/sin two hyperfinestatesof hydrogen,which constitutesa world recordfor this type of PIT. Thissuccessis largely basedon the high performanceof a newsystemof high-fieldpermanentmagnets,developedby us.

Fig. 6: Theatomicbeamsourcefor thepolarizedinternaltar-getof ANKE (laboratoryset-up).Thepolarizedatomsare injectedinto an ionizer and electrostaticallyde-flectedonto the horizontalaxis. The nuclearpolar-ization of the atomsis subsequentlyanalyzedby theLamb-shiftpolarimeter.

Thenuclearpolarizationof thePIT will bedeterminedfroma measurementof the polarizationof atomsextractedfromthestoragecell, ionizedandtheninjectedinto a Lamb-shiftpolarimeter. Thispolarimeter, developedat theUniversityofCologne,is alsoshown in Fig. 6. The measuredpopulationof magneticsubstates(mI 6 1

2) of an atomichydrogen

beamis shown in Fig. 7.The detectedasymmetryof the Lyman-α light after all cor-rectionyieldsa nuclearpolarizationof P 0 89. Testswithprototypestoragecells, aiming at the identificationof celldimensionssuitable for the ANKE target, are underway.The implementationof the target at the internal spectrom-eterANKE constitutesa majortechnologicalenterprise.Re-cently, a new largetargetchamberhasbeenimplementedatANKE to accommodatestoragecells in the future, a newset of small-aperturehorizontaland vertical beampositionmonitors,anda systemof target-neardetectors.Among the

50 55 60 65

0

25

50

75

100

125

150

175

mI=1/2

mI=-1/2

PLyman-α=+0.78

Sig

nal o

f PM

T [a

.u.]

Magnetic Field in Spin-Filter [mT]

PFinal=+0.89

Correction Factors

Fig. 7: Magneticsubstatepopulationof anatomichydrogenbeamandtheresultingpolarizationvaluesdeterminedwith theLamb-shiftpolarimeter.

first experimentsto becarriedoutwith thenew PIT atCOSYis themeasurementof theproton-induceddeuteronbreakup,which as a first step in the sequenceof investigationshasbeenstudiedin anunpolarizedexperiment.But theneedto providehigherluminosityfor COSYprevailsin particularfor experimentsinvolving polarizedbeams.Dueto thelimited targetdensityavailablefrom e.g.aPIT, in orderto reachluminositiesbeyond1030 cm 2s 1 requiresto pro-vide similar numbersfor polarizedparticlesstoredin COSYthancurrentlyavailableunpolarized.

Frozen pellet targetThe ANKE frozenpellet target,seeFig. 8, will allow mea-surementsat highestluminositieswhile the interactionzoneis almostpoint like andthe gasload on the ring vacuumisverysmall.Accordingto theexperiencewith a similar targetatCELSIUS,luminositiesof 7 1032cm 2s 1, e.g.compa-rableto solid-statestrip targets,areexpected.In theANKE targetdropletsof liquid hydrogen— andlateralsofrom otherliquefiablegases— areproducedfrom acon-tinuousflux of liquid hydrogenwhich entersa triple-pointchamber(TPC,containinghydrogengascloseto triple-pointconditions)throughavibratingnozzlewith adiameterof cur-rently 40 µm. Thesedropletswill freezedueto evaporationcooling when they leave the TPC into the acceleratorvac-uum througha thin tube of 0 5mm diameterand a fewcm length.In contrastto theCELSIUStarget thecryostatiscooledwith liquid nitrogenandhelium which shouldmini-mizedistortionsinduced,e.g.,by vibratingcold heads.Thetarget is currentlybeingpreparedin a teststandlocatedin theCOSYacceleratorhall (Fig.8). In 2002thetargetcryo-statandthehydrogensupplysystemhave largelybeenmod-ified, anda new TPC, offering larger observation windowsfor an optical diagnosticsystem,hasbeeninstalled.Duringseveraltestrunsstablefluxesof hydrogendropletshavebeenobtainedin the TPC, seeFig. 9. The productionof frozenpelletshasnotbeenobservedyetsincethecorrespondingdi-agnostictools — basedon two video camerasand a lasersystem— still arein preparation.They will be availableinspring 2003 whenfirst test runs with pellet productionarescheduled.During thesetestsnozzleswith diametersdownto 20 µm will beused.

Fig. 8: Testset-upof the ANKE pellet target in the COSYhall.

Sincethe proposedexperimentswith the pellet target (e.g.investigationof neutralscalarmesons)also requireneutralparticledetection,it is plannedto install thetargetat ANKEtogetherwith thephotondetector.

Photon detectorThe compact,large-acceptanceelectromagneticcalorimeterwith adiameterof lessthan80cmhasreachedits final designphase.It will cover polaranglesbetween25 and165 withfull azimuthalacceptanceandwill be usedto detectmulti-photonfinal states(e.g.decayof neutralmesons)in coinci-dencewith chargedejectilesin forwarddirection.In thebeginningof 2002modulescombiningleadtungstate(PbWO4) crystalsandshieldedHamamatsuR5505fine-meshphotomultipliersweresuccessfullytestedat thephotonbeamline of MAMI (Universityof Mainz).Linearity, timeanden-ergy resolution,gainandcount-ratestability of this specificcombinationwerefoundto bewell suitedfor thisapplication.Moreover, on-goingcrystaltestsshow thatrecentsamplesofPbWO4 haveanincreasedlight outputand,thus,anevenbet-ter performance.While theseinvestigationshave beendoneusingstandardhigh-voltagedividers,the final moduleswilluseactive Cockroft-Walton bases.A setof thesebaseshasbeenorderedfrom HVSys in Dubna,Russia,and will betestedfinally beginningof 2003.About 900of thesesinglemoduleshave to bemountedin aspherearoundthe targetpoint. In orderto keepthe flexibil-ity to have differentnear-target installations(or to combinethem)it is a strongrequirementthat all of themcanbe ex-changedwithin onemaintenanceweekof COSY. This canbe achieved only with a modulardesignof the full setup.Therefore,it is plannedto usequarteror half spheresmadeof carbonfibre ascontainersto allow a convenientandfast

Nozzle

Sluice to1st vacuum chamber

Hydrogenbreaks into

droplets

Fig. 9: Stableflux of liquid hydrogendropletsin the TPC.The nozzlediameterandfrequency were40 µm and6 kHz, resultingin adropletdiameterof 80 µm.

assemblinganddisassemblingof thewholedetector. For thispurposediscussionshave startedwith the Zentralabteilungfur Technologie(ZAT) of theFZJandtheInstitut fur Kunst-stoffverarbeitung(IKV), RWTH Aachen.It is intendedto fixthefinal geometrywithin thesecondhalf of 2003.In parallel,thenewly developedread-outelectronicsfor theTAPSspectrometerwill bemodifiedandadoptedto thepho-tondetector. Furthermore,thedevelopmentof avetodetector(to beplacedinsidethecrystalshell)will startat theInstituteof Physicsof the JagiellonianUniversity in Cracow. Withinthecurrenttime scheduleit is foreseento have thefull setupreadyfor installationat ANKE in thefirst half of 2006.

External activities: Measurements at PSIMeasurementof the hadronic ground-stateshift ε1s andbroadeningΓ1s in pionic hydrogengives accessto funda-mentalparametersof the pion-nucleoninteractionlike theisoscalarand isovector s-wave scatteringlengths and thepion-nucleoncoupling constant.Ongoing improvementinChiral PerturbationTheory — the low-energy approachofQCD — will allow calculationsat the percentlevel, whichshouldbe experimentallytestedwith comparableaccuracy.The isovector scatteringlength is directly related to thehadronicbroadeningand constitutesone key point for thecomparisonof theoryandexperiment.Hence,the main goal of the new pionic hydrogenexperi-mentat the Paul-Scherrer-Institut (PSI) is to achieve finallyanaccuracy for Γ1s of about1%,whichis animprovementofsevenascomparedto previousexperiments.Thetechniqueisbasedon thecyclotrontrapto producea brightX-ray source

for a focusingreflection-typecrystalspectrometer. Braggre-flectedX-raysaremeasuredby a large-areatwo-dimensionalposition-sensiti8 ve detectorsetup with Charge-Coupledde-vices.The essentialpart of the experimentalprogramis to studytheinfluenceof non-radiativede-excitationprocessesduringtheatomiccascade,whichcompetewith X-ray emissionandoccurin collisionswith targetmolecules.At first, formationof molecularstructureslike [(πpp)p]eecould causean en-ergy shift of theX-ray lines,which falsifiestheresultfor ε1s.Secondly, whende-excitationenergy is sharedaskinetic en-ergy betweenthecollisionpartners(Coulombde-excitation),aDopplerbroadeningof theX-ray linesoccur. Consequently,thestrategy of theexperimentis to measureatvariousdensi-ties.A first seriesof measurementshasbeencompletedin 2002,coveringthepressurerangefrom 3.5barto liquid. No densityeffect for ε1s could be established.To studythe line broad-eningdueto Coulombde-excitation, the threeπH 2p 1s(2.4keV),πH 3p 1s (2.9keV) andπH 4p 1s (3.0keV)transitionswere studied at a target density equivalent to10 bar(Fig. 10).An increaseof theline width wasfoundforthe2p 1s line comparedto the3p 1s transition,which isattributed to the higherenergy releaseavailable for the ac-celerationof thepionic-hydrogensystem.This resultis cor-roboratedby a reducedline width of the 4p 1s transition(seethis report).At present,thedataarebeinganalysed.Animprovementof both ε1s andΓ1s is expectedby a factorofabout2.

Fig. 10: πH4p9 1s transitionmeasuredin 2002.5400eventsweretaken over 2 weeksof beamtimewith a peak-to-backgroundratioof 35 to 1.

A further improvement for Γ1s requires a more pre-cisely known correctionfor the Doppler broadening.Thiswill be achieved by future studiesof muonic hydrogen,where hadronic broadeningcannot contribute to the linewidth. In preparation,an electron-cyclotron-resonance-ion-trap (ECRIT) hasbeenset up at PSI to measurethe crys-tal responsewith narrow X-ray linesemittedfrom electronichydrogen-and helium-like light ions. A successfulcom-missioningin 2002resultedin a high rate for X-rays fromhelium-like Ar (seethis report).Suchhigh-statisticsstudieswill replacethemeasurementof thecrystalspectrometerre-sponsewith theπ12C 5g 4 f line usedupto now, for whichthestatistics— andcorrespondinglytheaccuracy — arelim-ited dueto beamtime considerations.

For the measurementof X-rays from light and mediumZexotic atoms,a high-ratecapabledetectorsystembasedonfully depletedCCDs as usedin X-ray astronomysatelliteshasbeenbuild up.It hasbeentestedsuccessfullyin 2002(seethis report).Becausethemeasurableenergy rangeextendstobelow 2 keV, it will be the ideal diagnosistool for optimis-ing beam-injectionfor the next stepof the pionic hydrogenexperiment.

AcknowledgementsThe work at the ANKE spectrometerhas partially beensupportedby: BMBF (grants WTZ-RUS-684-99, WTZ-RUS-686-99,WTZ-RUS-211-00,WTZ-RUS-691-01,WTZ-GEO-001-99,WTZ-POL-007-99,WTZ-POL-015-01,WTZ-POL-041-01,WTZ-KAZ-001-99),DFG (436RUS 113/337,436 RUS 113/444,436 RUS 113/561);Polish StateCom-mittee for Scientific Research(2 P03B 101 19); Rus-sianAcademyof Science(RFBR99-02-04034,RFBR99-02-18179a,RFBR99-02-06518,RFBR02-02-16349),RussianAcademyof Science;ISTC (1861,1966).Systemdevelopmentfor COSYexperimentsis donein closecooperationwith the Central Laboratory for Electronics(ZEL). Themaingoalis to improvetheefficiency, flexibilityandstandardizationincludingstateof theart technologies.