crystal ball at desy - stanford university · 2016-03-24 · the crystal ball at desy the...

The Crystal Ball at DESY

The peripatetic Crystal BallLogo stolenfrom BNL 913. . .

I Crystal array assembly at Harshaw Chemical Company inCleveland

I 1978-1981 SLAC - SPEAR (Mark Oreglia talk)I work on possible move to PEP(-I!) (JCT)I 1982 proposal to be first/second detector at SLC

I 1982-1987 DESY - DORIS III 1987-1996 SLAC ESB (mothballed)I 1996-2002 BNL AGSI 2002-present Mainz Microtron (A2 Collaboration)

I Opportunities for the Crystal Ball at JLABStarostin, AIP proceedings 1257 (2010) 808

(J. K. Bienlein’s DESY-F31-91-02 has been helpful)

Transport pictures from David Gelphman’s blog

March 18, 2016 Frank Porter, Elliott Bloom Symposium 1

https://davidgelphman.wordpress.com/2014/01/15/moving-the-crystal-ball/

mailto:[email protected]

http://mu2e-docdb.fnal.gov:8080/cgi-bin/ListBy?eventid=1084&mode=conference

The SLC letter of intent

EPAC deferred. . .March 18, 2016 Frank Porter, Elliott Bloom Symposium 2



Crystal Ball DORIS physics – proposed

Contents from 1984 proposal2 years after the move




The Crystal Ball at DORIS-II collaboration (I)

Germany DESY Bartels Bienlein Brockmuller Cooper Drews FolgerFridman Gomez-Moreno Kloiber Koch Lenzen Mar-siske Meyer Rehder Scmitz Schneider Selonke TrostVoigt Wachs Zschorsch

Erlangen Glaser Kobel Lurz Schutte Volland WegenerHamburg Bieler Graaf Heimich Heinsius Kiel Kruger Leke-

busch Lezoch Maschmann Nernst Pegel SchwarzSievers Stock Strohbusch

Wurzburg Karch Keh Kilian Konigsmann Scheer ScmittItaly Firenze Bizzeti Cartacci Compagnucci Conforto DeJudi-

cibus Landi Monteleoni Papini PelferNetherlands Nijmegen Janssen Konig Metzger Pols Reidenbach Schotanus

Van de Walle WalkPoland Cracow Jakubowski Korbel Lesiak Muryn Niczyporuk

Nowak Skwarnicki




The Crystal Ball at DORIS-II collaboration (II)

South Africa Cape Town AschmanUSA Caltech Edwards Peck Porter Ratoff

UCSC/Princeton Cavalli-Sforza Coyne LitkeCMU Brock Engler Kraemer Marlow Messing

Prindle Renger Rippich VogelHarvard Antreasyan Irion McBride Strauch

WilliamsPrinceton Besset Cabenda Cowan Newman-HolmesStanford/SLAC Bloom Broder Clare Fairfield Gaiser Gelph-

man Godfrey Hofstadter Kirkbride Lee Lef-fler Lockman Lowe Matsui Pollock Tomp-kins van Uitert Wacker




The journey in a C-5A

Drinking from a tanker Unloading in Frankfurt




The flight crew

Chad Edwards now (link) David Gelphman now (link)


https://www.youtube.com/watch?v=e60BfCRwZmU

http://davidgelphman.com/davidgelphman.com/Home.html



The road to Hamburg




DORIS-II Crystal Ball detector

2634 D. ANTREASYAN et al. 36

Nat(TE)End Cap~Na l(TP )

ki~i~~i%iiiiii~g

Mini- 0 ~Quadru pole

LumlnosMonitor

HernisphBoundar

isphereundary

FIG. 1. The Crystal Ball detector.duai

gle. It contains 672 optically isolated crystals, eachviewed by a phototube. Each crystal is a truncated tri-angular pyramid 16 radiation lengths deep pointing to-wards the interaction point. The segmentation of thespherical shell is based on an icosahedron, as shown inFig. 2. Each of the 20 triangular faces, referred to as"major triangles, " is subdivided into four "minor trian-gles" each consisting of nine individual crystals. A com-plete 4~ ball would contain 720 crystals; to allow entryand exit of the beams, 24 crystals from each of two di-ametrically opposed regions are omitted. The 30 crys-tals immediately surrounding each beam hole are calledthe "tunnel crystals. " The remaining crystals, covering85% of 4~, make up the "main ball. " NaI(T1) end capscover an additional 5%%uo of 4~, but are not used in theanalysis presented here.

The measured energy resolution for electrornagnetical-ly showering particles is o.z /E =(2.7+0.2)% I &E (Ein GeV), with the energy shared among a symmetriccluster of 13 neighboring crystals. A photon deposits onaverage 70%%uo of its energy in the central crystal, andabout 2% is outside the cluster of 13. This pattern of la-teral energy deposition is useful in identifying elec-tromagnetically showering particles. Using the distribu-tion of energy within the cluster, we determine the direc-tions of showering particles to an accuracy ranging fromabout 3 for the polar angle of a 70-MeV photon toabout 2' at 500 MeV. The NaI(T1) energy scale is set foreach —3 pb ' of accumulated data using large-angleBhabha-scattering events. We use our studies of theY(2S)~~ n Y(IS) channel to correct our calibration atlower energies by a one-parameter nonlinear expression,which gives a correction of +5%%uo at 100 MeV.

Charged particles are detected in a set of cylindrical

e beamdirection

FIG. 2. The organization of the individual crystals into ma-jor and minor triangles, and into top and bottom hemispheres.The shaded area is the layer of "tunnel crystals" next to thebeam.

proportional tube chambers which surround the beampipe. There were originally three double-layeredchambers filled with "magic gas. " They have been re-placed in stages by a set of four double layers filled witha (79-20-1)% Ar-COz-methane mixture. The beam pipehas a thickness corresponding to 0.017 radiation lengths(r.l.). Each double-layer chamber adds 0.010 r.l. in theold and 0.017 r.l. in the new configuration. In theanalysis presented here, we are interested in all-neutralfinal states, and use the chamber information to rejectevents with charged tracks. Although the chambers canbe used for tracking, we find it sufhcient here to simplycount chamber "hits" with pulse-height discriminatorswhich are also used in the trigger. We use the hits inthe third chamber, which is at a radius of 14.5 cm (11cm) and covers 78% (87%) of 47r in the old (new)configuration.

The triggers are based on fast analog sums of the ener-gy deposited in the main ball, its top and bottom hemi-spheres, and each of its major triangles. These are sub-jected to various discriminator thresholds. The tunnelcrystals are excluded from these sums, giving an eff'ectivetrigger solid angle of 85% of 4~. For use in vetoingbeam gas and other events originating far from the in-

TABLE I. Triggers.

Trigger name

2 hemisphere6 hemisphere

MultiplicityCombination

Min. E inmain ball

(MeV)

800860

450800

Max. E intunnels(MeV)

30No limit

3065

Chamberveto?

NoYes

YesNo

Additional requirements

& 180 MeV in top, bottom& 1 major with & 150 MeVin each of 6 hemispheres

&3 majors with & 110 MeV& 1 major with &60 meVin each of 6 hemispheres and) 3 majors with & 110 MeV




Crystal Ball dataset at DORIS-II

Energy Luminosity (pb−1)

Υ(1S) 46Υ(2S) 56Υ(4S) 89continuum 42scans 21

total 254




Physics program – actual

I Bottomonium spectroscopy [8]

I (other) QCD [2]

I B and D decays [4+1]

I τ decays [3+1, including lepton flavor violation]

I Spectroscopy in two-photon interactions [7]

I New physics [1+1]




Bottomonium: χb states in theinclusive photon spectrum

34

I/

/

11

11

1 II

1I

1

1

I

1I

1

11

1

1

1

1I

1I

1

1

I11

~'s, ~,——+&—

2'S0

FIG. 1. The energy-level scheme for bE bound states that canbe reached by a radiative transition from the YI,'2S). The solidlines represent the observed transitions.

e+e storage ring DORIS II. The data sample corre-sponds to an integrated luminosity of 63.1 pb

In Sec. II we discuss the technical features of the Crys-tal Ball detector relevant to the analysis presented here; amore detailed description has been presented elsewhere.In Sec. III the event selection leading to the final eventsample is described. In Sec. IV we present our results andcompare them with Crystal Ball inclusive photon mea-surements and with previous cascade results. In Sec. Vour results are compared with @CD predictions. SectionVI is reserved for conclusions.

II. THE DETECTOR

The Crystal Ball apparatus, shown in Fig. 2, is a non-magnetic detector designed for measuring electromagneti-cally showering particles. The excellent energy and angu-lar resolution of the Ball, resulting from its depth of 16radiation lengths and its high segmentation, make it wellsuited to study yye+e and yyp+p final states. Itsmajor component is a spherical shell of 672 taperedNaI(T1) crystals, covering 93% of the total solid angle.Two arrays of end-cap crystals increase the coverage ofthe solid angle to 98%.

The energy resolution for elex:tromagnetically shower-ing particles is

u(E)/E =(2.7+0.2+0.2)%/1 E(GeV) .

Event 'r(») - n/'/

A typical shower is distributed over approximately 13crystals. Using an algorithm to find the center of ashower, an angular resolution of 1' to 2' is achieved, de-

pending an the energy. The energy response of theNaI(T1) crystals to a monochromatic electromagnetic par-ticle is slightly asyinmetric but well fitted by the sum of aGaussian combined with a polynomial tail toward lowerenergies. The parameters of this so-called NaI line-shapefunction were fixed in previous studies of the reactionQ(2S)~rlJ/g, rI~yy. Unlike photons and electrons,high-energy muons do not deposit all their energy in thecrystals. Their energy deposition follows a Landau spec-trum peaking at 210 MeV, the most probable energy lossfor a minimum ionizing particle crossing 16 radiationlengths of NaI. This energy is deposited in one or twocrystals only; thus, the angular resolution for minimumionizing particles is 2' to 3'. Typical energy patterns formuons, electrons, and photons are shown in Figs. 3 and 4which present Mercator-type crystal projections of theBall, each showing a cascade event candidate.

Three double layers of proportional tube chambers withcharge division readout are used to identify charged parti-cles. Electrons are recognized by their large energy depo-sition in the crystals and the presence of an associatedtrack in the tube chambers. Muons are identified by achamber track pointing to a minimum ionizing energypattern in the NaI(T1). Photons are seen as particles witha typical electromagnetic shower pattern, but without anassociated track in the chambers.

The NaI(T1) energy scale is fixed by measuring largeangle Bhabha events. The time stability of the electronicsassociated with each channel was checked using a lightflasher system. Studies of the Y(2$)~motr Y(1S) decaychannel, show that a linear relation between the measuredpulse height and the energy deposition in the crystalsleaves both the n mass and the mass differencehM =M[Y(2S)]—M[Y(1S)] about 5%%uo below the estab-

NoI{TE)End Cop~i'

Lumino

M~ni- gQuodr upole

sityMonitor

kXXXXXXXXXXXX

CRYSTAL BALL

NoI (Tg )

Tube Chornbers

,::::,'~xxxxxxxxxxxxxxx4

V

N/N. "/V~ NNN/NIM NRMNN NN

NINN/ NINN NNN/NRNNN NN N'N

FIG. 2. Schematic of the detector as configured at DESY forthis experiment.

FIG. 3. Event map for Y(2S}~yyp+p event. The energyis given in MeV for all crystals containing more than 0.5 MeV.

VOLUME 54, NUMBER 20 PHYSICAL REVIEW LETTERS 20 MAY 1985

The hadronic Y(2S) event sample is obtained by re-moving background due to beam-gas interactions,cosmic rays, two-photon events, and QED events.The remaining data sample contains contributionsfrom the resonance and the continuum in a ratio of ap-proximately 1 to 1. The efficiency for the selection ofhadronic decays of the Y(2S) is calculated to beeh = (86 +7)% with use of a Monte Carlo simulationof the properties of the detector. Further details of theevent selection and the efficiency determination canbe found in Edwards and Nernst. 8

The photon selection is described next; it isdesigned to remove charged particles, photons from 7ro

decays, and photons whose showers are contaminatedby energy depositions of nearby particles. A photonmust lie within an angular range defined by Icos&I~ 0.75 (0 is the photon angle with respect to the posi-tron beam). This cut ensures coverage by all threetracking chambers. The photon has to be "neutral"which means that no crystal contributing to the photonshower is correlated with hits in the tracking chambers.To minimize distortion of the photon energy we re-quire that the energy cluster of any photon candidate iswell separated from all other clusters by at least 30'.The lateral energy distribution in the crystals must beconsistent with the pattern of a single electromagneticshower, and photon pairs which can be fitted to

yy decays are removed.The photon selection efficiency for these cuts is

e~ = (15.2 + 1.5)'/o, independent of energy for 50~ E ~ 500 MeV. It is determined by adding MonteCarlo photons in that energy range into hadronicY(1S) events and analyzing these events with the cutsdescribed above. See also Ref. 6 for details on themethod.

Figure 1 shows the energy spectrum, with a loga-rithmic energy scale, of photons satisfying the aboverequirements. Three clearly separated peaks in the re-gion between 100 to 170 MeV and another around 430

MeV are visible. The shoulder at 210 MeV is due tomisidentified charged particles. We fit the spectrumfrom E = 50 to E = 650 MeV using the sum of thefollowing terms: (1) A fourth-order Legendre poly-nomial series representing the photon background.(2) A charged-particle spectrum with variable ampli-tude to take account of the remaining charged-particlecontamination. (The shape of this spectrum is ob-tained by taking genuine charged particles as definedby the three tracking chambers and applying the pho-ton selection cuts. ) (3) Three Gaussian distributionswith widths determined by the known energy resolu-tion to describe the signals in the 100—170-MeV re-gion. (4) Two Gaussian distributions to describe theDoppler-broadened secondary lines around 430 MeV,at energies fixed by the two lower energy lines and theknown Y(25)-Y'(1S) mass difference. 9'o We assumehere and below that the line around 430 MeV is due tothe secondary transitions P2 t yY'(15), where theP2 and P~ are assumed to be the two more massive

of the three observed states. " The Po yY(15)branching ratio is expected to be small. '2 This is indi-cated by a previous experiment' and our studies'4 ofthe exclusive channel Y(2S) yyY(1S) yy&+I

The result of the fit to the inclusive photon spec-trum is shown in Fig. 2. The dashed line in Fig. 2(a)represents the smooth polynomial background. Thecharged-particle "punchthrough" background is givenby the difference of the solid line (that excludes theGaussians) and the dashed line. In Fig. 2(b) this back-ground has been subtracted. The fit has a confidencelevel of 72%

The branching ratios for the observed transitions arecalculated according to B=N~/N„, e„„where N isthe number of photons in a given peak, N„„ is the

40

50O

20

400X

c 300~O

o20

I I I IIII I I I ! I IIII I I

~O0O

WC

0

IO

O I I I I I

4 (b)

10 —2 I I I I I I I I

I0' IO IO

(Mev)

I04

FIG. 1. The inclusive photon spectrum from the Y(2S)hadronic decay selected with the cuts described in the text.

50 IOO 200 500(Mev)

FIG. 2. (a) The fitted part of the photon energy spec-trum. As described in the text, the curves represent theresult of the fit. (b) The same distribution after backgroundsubtraction. Only error bars are shown for clarity. The datapoints are in the middle of the error bars.

PRL 54 (1985) 2195




Bottomonium:Υ(2S)→ γγΥ(1S), Υ(1S)→ e+e−

34 gg STATES IN EXCLUSIVE RADIATIVE DECAY OF THE Y(2S) 2613

vNN NN NN NN NN/N'M /NM /N/N /NM /N/N

NNM NNM NN/N MNN NNMVVVVVVVVVVV3

VVVVVVVVVVVVVVVVVVVVVVVV&

VVVVVVVVVVVVVVVVVYVV

NN. „„NN NN NN .„,NN

FIG. 4. Event map for Y(2S)~yye+e event. The energyis given in MeV for all crystals containing more than 0.5 MeV.

lished values. ' We therefore correct our energy calibra-tion with a one-parameter nonlinear expression found towork well for photons in the 50-to-300-MeV range for thereaction Y(2S)~m n Y(1S)~yyyy Y(1S),

Emeas

I +aln(E, /Eb„) (3)

with a=0.0137; the value of a was derived from a fitmaking both the rl mass and the 2S-1S mass differenceagree with their nominal values.

III. EVENT SELECTION

For trigger and selection purposes we use the "mainball, " i.e., all crystals which are not in the so-called tunnelregions (two layers of 30 crystals closest to the beam en-trances).

The triggers relevant to this analysis were the following.(a) A total-energy trigger, which requires the total ener-

gy deposited in the main ball to exceed 1700 MeV.(b) A topology trigger, which requires the total energy

in the main ball to be above 760 MeV and to be roughlysymmetrically deposited around the interaction point.The latter condition is implemented by dividing the mainball in (ten) different ways into two hemispheres and re-quiring for each of these configurations to have at least150 MeV energy deposited in each hemisphere.

(c) A "p-pair" trigger, which requires more than 220MeV in the main ball, two back-to-back energy clustersand less than 40 MeV in each tunnel region. Clusters areconsidered back-to-back if the directions of their centersare acollinear by less than 40'.

The total-energy trigger is expected to detect allyye+e events within the accessible solid angle, whilethe topology trigger and the p-pair trigger are intended todetect the yyp+p events which only deposit about 950MeV. The efficiencies of all three triggers are determinedusing Monte Carlo —simulated cascade events survivingthe software selection. The results obtained vary by ap-

proximately 1% depending on the spin assumption used.Averaged over all possible spin hypotheses, one finds forthe yye+e cascades efficiencies of —100%, -99%,and —100% for the total energy, topology, and p-pairtrigger, respectively; for the yyp+p cascades the corre-sponding numbers are -Ok, -94%, and -93%. Thecombined efficiency of all three triggers is larger than98% for all p-channel cascade events and nearly 100%for all e-channel cascades.

To search for events of the cascade type [Eq. (1)j, allsuch triggered events are subjected to a set of criteria op-timized for selecting the characteristic topology involved:namely, two almost back-to-back leptons and two addi-tional photons. The software selection is carried out asfollows.

(i) An event must have exactly four particles (energyclusters larger than 10 MeV) in the main ball and no par-ticles in the tunnel region.

(ii) There must be two particles (the lepton candidates)with an electron signature, or two particles with a muonsignature from the crystals. We require that at least oneof the lepton candidates has an associated charged trackin the tube chambers. In addition, the opening angle ofthe lepton candidates must be greater than 160'.

(iii) The two remaining particles must each have an en-

ergy of at least 50 MeV and have a photon signature.This 50-MeV cut eliminates background, but also limitsthe accessible photon energy range.

(iv) To provide a good energy measurement, each parti-cle is required to deposit its energy in an isolated group ofcrystals. This is achieved by applying a cut on the open-ing angle, a, between each pair of particles of such thatcosa &0.8, if both particles are showering, or cosa ~0.9, ifone is minimum ionizing.

(v) To eliminate background in the yyp+p channel,both the unassociated energy (not belonging to any of theparticles) in the main ball and the energy deposited in theend caps are required to be less than 45 MeV.

(vi) Finally, all events must pass a two-constraintkinematic fit, using energy and momentum conservation,to the hypothesis @pl+I . The lepton energies and theintermediate Xb and Y(1S) mass constraints are not usedin the fit.

After imposing all the above cuts we are left with asample of 282 yyl+1 events.

IV. RESULTS

A. The energy levels of the gq states

Figure 5 shows a scatter plot of E~i,„(defined as thelowest of the two photon energies) versus the mass differ-ence bM =M[Y(2S)]—M(1+1 ) for all events survivingthe selection procedure described in Sec. III. M(1+1 ) isthe effective mass of the two leptons recoiling against thephotons; it is calculated using the Y(2S) mass" and themeasured four-momentum vectors of the two photons; thefact that the Y(lS) decaying into two leptons is alwaysclose to being at rest implies that given the resolution ofour detector, using the angles of the charged-lepton tracksin fitting M(1+1 ) yields no improvement. Two distinct

PRD 34 (1986) 2611March 18, 2016 Frank Porter, Elliott Bloom Symposium 13



Bottomonium:The Υ(2S)→ γγΥ(1S) transitions

1000

800—

600— ~ ~~ ~I! ~

~ ~ ~ ~ ~L~e~~ / ~ ~~ + 0 ~ ~

~ ~

+- CUT

~ CUT

~ ~ r*

.//

~ /

~ ~ / fk

/:"gY

~/

//

400 -'

~ ~

/ ll! ~

200-'' '

Ez~,„clusters are observed in the region of bM-560MeV.

Figure 6 shows the projection of the scatter plot on thehM axis for 440 MeV ~b3f ~680 MeV; the peaking ofevents in the region of the Y(2S)—Y(1S}mass differenceindicates that we indeed see the photon transitions fromthe Y(2S) to the Y(1S). A fit to this distribution using aNaI line shape (see Sec. II) on top of a flat background

18—

16—

l l l l I l l l l

50 75 100 125 150 175 200 225 250 275 300

E„.„(M.V~

FIG. 5. Scatter plot of the lowest of the two photon energiesversus the mass difference hM = [Y(2S))—M(l+l ) for all 282events surviving the selection cuts for the yy1+I final state(see text). The horizontal lines indicate the sidebands: 3o wide

regions on both sides of the 6o wide signal band. The arrowsindicate the final cut on hM.

gives XV~k ——(562+2) MeV, in good agreement with theprecise mass difference measurement, ' and a width con-sistent with our experimental resolution (a=16+2 MeV).The hM distribution is used to apply a final cut to thedata; all events outside AM~k+ 3o. are eliminated.Monte Carlo studies show that this (symmetric) cut elim-inates about 3% of "good" events at the low-end side ofthe AM distribution and less than 1% at the high-endside, the asymmetry originating from the non-Gaussiannature of the NaI energy response. After this cut a sam-ple of 58 yye+e decays and 42 yyp+p decaysremains.

The projection of this final sample on the E„&,„axisisshown in Fig. 7. This distribution shows two well-separated peaks at about 107 and 132 MeV, respectively,with widths consistent with our experimental resolution.Our data do not show an indication of a thirdY(2S)~yXb transition, which was seen in inclusive analy-ses ' at about 164 MeV. In the following we will assumethat the 107-MeV line corresponds to the decayY(2S)~y1'b and the 132-MeV line to the decayY(2S)~yXb . This agrees with expectations from poten-tial model calculations and with our preliminary spindetermination of these states. ' This assumption is alsoconsistent with the theoretical prediction that the transi-tion Xb ~y Y(1S) has a smaller branching ratio than theother two transitions. '

A fit to the distribution of Fig. 7 in the region 50 to200 MeV, using two NaI line shapes with widths fixed toour energy resolution [Eq. (2)] on top of a flat back-ground, yields the following energies EJ ..

E2 ——107.0+1.1+1.3 MeV,

E) ——131.7+0.9+1.3 MeV

where the first error is statistical and the second systemat-1c.

Fitting the yye+e and yyIM+p channels separatelyyields compatible values as shown by the results displayedin Table I. Estimates of the systematic errors from energyscale uncertainty, event selection and fitting procedure arelisted in Table II. The final error was obtained by addingthe suberrors linearly, rather than in quadrature. Linearaddition of the errors was chosen after comparing the en-

440it

480 520

CUT

t

560l I l

600 640 680

,r„, aV (MeV/c')

!

~ 2oI!!!8

)6-l4I

iv)

8

6 I-

50

FIG. 6. Projection of Fig. 5 on the AM axis for 440MeVghM~680 MeV. The curve represents the fit to a NaIline shape on top of a flat background (see text).

FIG. 7. Projection of the signal band (100 events) in Fig. 5 onthe E~~ axis. The curve represents the fit to two NaI lineshapes of fixed width on top of a flat background (see text).

Observe χb1 and χb2 in“cascade” channel

PRD 34 (1986) 2611

Also spin analysis of χb statesPRL 58 (1987) 972

0.4 t 4 ywe 1

no

0.4

t G

0.3 -

0.2 -

0.1 -

0.0 -

, :-’ #P:. ‘. I ’

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..-._-- ’ . . . . . . . . . . . . . . . . . . . . . . . no

90.0 95.0 100.0

M2iY US), 71 (GeV/c212 40483

Figure 1:

12

Looking for Υ(2S)→ ηΥ(1S)and Υ(2S)→ π0Υ(1S)

ZPhC 36 (1987) 383March 18, 2016 Frank Porter, Elliott Bloom Symposium 14



Bottomonium:Υ(2S) mass by resonance depolarization∣∣∣∣ (g − 2)Ebeam

2me− n

∣∣∣∣ =fDf0

Scan fD to find depolarizingresonance =⇒ EbeamVolume 135B, number 5,6 PHYSICS LETTERS 16 February 1984

/ existing feedback system for DORIS

"--"3 I . . . . I coils (horizontal I TeeaDacK radial field. ) ]II

despi ;]L~rli z i ng

frequency synthes zer

b Hut nt the top of DORIS

:kets cell ~ Mirror

Ar ÷ laser (cavity dumped) I i i i t._J

bockscattered electron interQction point

bend mirror

IFT- Hut

movable slit

~ unter

Fig. 1 (a) Block diagram of the DORIS depolarizer. (b) Schematic view of the DORIS polarimeter.

501

Oscillate B at fDf0 = revolution freq.

polarimeter

σ(e+e− → hadrons) vs ECMVolume 135B, number 5,6 PHYSICS LETTERS 16 February 1984

8 av,s[nbl

e -e - - - - - . ) hQd r on s

ARGUS

÷ ÷

o 9~6 ' a~8 ~'o2 ~'o~ ~g [GeV]

A)

1 ~obo ~:o6

10

Ovis[nb]

8

, , l • , • • ,

e* • ---~ h(:ldrons B)

Crystal Ball

-f-

i J J i i

9;6 998 ,600 ,0'o2 ~oo, ~o'.o6 Cg [GeV J

Fig. 3. The visible hadronic cross section of the T' resonance.

long tail caused by nuclear interactions. Neutral, electromagnetically decaying hadrons deposit all their energy in the detector.

In the selection of hadronic events and the determination o f the visible cross section three different methods which gave compatible results were used. Two of the methods yielded results so rapidly that they were used to optimize the scan strategy during the run. In the following, one particular method is presented.

The events used in this analysis triggered the apparatus by passing a total-energy threshold at about 1800 MeV. The pat tern o f energy deposit ion was required to be symmetric with respect to the interaction point in order to remove cosmic ray and b e a m -

gas events. A minimum of 5 detected particles (charged or neutral) was required. The latter cut also removed events due to the QED processes e+e - -+ e+e - and

e+e- ~ 77. The contamination of the hadron sample due to

cosmic ray and beam-gas events was measured with separated-beam runs which were distributed over the period of data taking and was found to be less than 2%.

The luminosity was measured in two ways. In the first method, a small angle luminosity monitor was used to detect Bhabha scattering events in the range of 6 - 1 0 degrees of the scattering angle. In the second method, the main detector was used to identify Bhabha and e+e - ~ 77 events in the angular range given by i cos 01 < 0.85. The two luminosities agreed well, to better than 10%, and their ratio was constant within statistical errors over the run period.

The resulting visible cross section is shown in fig. 3b. Runs without depolarization energy measurement were not used. The data points were fitted with the same function as in fig. 3a (solid line). The resulting mass value is (10022.8 +- 0.5) MeV, where the error is statistical only. The gaussian width due to the beam energy spread was found to be 8.1 + 0.5 MeV.

The two beam width results agree with the expected DORIS resolution [2]. The two mass results are averaged to give

m ( T ' ) = (10023.1 + 0.4) MeV. (3)

In combining the errors of the two experiments, correlations due to common errors in the beam energy were taken into account. The difference between the sum of the average electron and positron energies determined by depolarization and the sum of the actual mean electron energy and mean positron energy in each of the two interaction areas is estimated to be small. A detailed estimate of the difference results in a systematic error of less than 0.1 MeV on the T ' mass which is included in the overall systematic error estimate.

After finishing the experiment, we learnt that the Novosibirsk group [10] had also measured the T ' mass using the depolarization method at their storage ring VEPP-4. Their result is

m ( T ' ) = (10023.8 -+ 0.5) MeV, (4)

The two values, (3) and (4), are in good agreement.

503

ARGUS

Crystal Ball

PLB 135 (1984) 498March 18, 2016 Frank Porter, Elliott Bloom Symposium 15



Axion (and light Higgs)

“Standard” Weinberg-Wilczek axion isruled out by Crystal Ball (combiningSPEAR and DORIS results)

Γ(Υ→ γa) = Γ(Υ→ µ+µ−)GFm

2b√

2παCΥ

1

x2

Γ(J/ψ → γa) = Γ(J/ψ → µ+µ−)GFm

2c√

2παCJ/ψx

2

x = ratio of Higgs VEVs (=1 for lightHiggs)CΥ ∼ CJ/ψ ∼ C ∼ 0.5 higher ordercorrections

a

C

16'

UT* 1

1

C

10* 1

IO -3 lo-* lo-' 1 10 lo* lo3

X

0 -3 lo-* 10-l 1 10 lo* lo3

X

FIG. 2

PLB 251 (1990) 204

(Υ→ γee exclusion is

from ARGUS)




Two photon (e+e− → e+e−X )A good way to look for and study C -even states

Almost as many papers on γγ as on bottomoniumCrystal Ball at DORIS studied γγ →

I γγ [π0, η, η′]I ηπ0π0 [η′, discovery of η2(1870)]I ηπ0 [δ(980), A2(1320)]I π0π0 [threshold to 2 GeV; f0(975), f2(1270)]

Most cited paper!I π0π0π0 [π2(1670)]

The η2(1870) in γγ → ηπ0π0

Z. Phys. C 54, 33 (1992)




B physics

B physics is hard for a non-magnetic detector, but ARGUS waskeen to run on the Υ(4S)Nonetheless, the Crystal Ball made some of the earlymeasurements of great relevance in the physics of the B factories

For example, b → u transitions in semileptonic decays

Missing mass against an e± anda π0 to search for B± → e±νπ0

6

4

2

0 I I I L

0

I III

5

(Missing mass)2 [ (GeV/c2)2]

Figure 5 -

0 5

(Missing mass)2 [ (GeV/c2)2]

Figure 6

16

Z.Phys. C48 (1990) 553

Inclusive electron spectrum for Binclusive semileptonic rate

Z.Phys. C42 (1989) 33




B physics

Relevant to later B factory studies of CP violation, Crystal Ballmeasured the b → ccs (plus b → ccd) process in inclusiveB → J/ψ, using J/ψ → e+e−

Figure 1

Combinations / 100 MeV/c2

2300 2700 3100 3500 3900 4300 e+e- invariant mass [MeV/c2]

Figure 2

15

Figure 1

Combinations / 100 MeV/c2

2300 2700 3100 3500 3900 4300 e+e- invariant mass [MeV/c2]

Figure 2

15

Z.Phys. C46 (1990) 555




B physics

Search for radiative B decays, an early search for b → s“penguins” in B physics

dn’ d In E.0.03

100.0 -

50.0 - :..‘“: - :... :“: ,. ._ ,. ., .’ : ; ,.. :. . ‘. I .. : ‘: ,f ‘:, . ..,’ .._.: . . . .

0.0 1100 1500 2000 2500 3000 4000

Figure 2: Inclusive spectrum of photons from the ON Y(4S) (solid histogram) and the continuum (dotted histogram) data samples. We multiply the continuum spectrum by T = 4.025 before subtracting it to get, Fig. 3.

100.0 1 I 1

dN d In E-0.03 I

photons from B meson decayst 11 -+ not B decays

II + . + II

1 ~~~tt+,~~+‘~~,~,i_,

? T M recoil : 2045 892 M~l’/c2

I I I I ‘-100.0 ’ 1100 1500 2000 2500 3000 4000 E, (Mel-)

Figure 3: The inclusive photon speckum from BB events (aft,er the subtraction of t.he con-

tinuum contribution from the ON Y(4S) events).

12

Z.Phys. C55 (1992) 33




The ζ in Υ(1S) radiative decays

Seen in multiple hadrons and low multiplicity “two”-jets (“τ+τ−”)

m(ζ) = 8322± 8± 24 MeVΓ(ζ) < 80 MeV

B(Υ(1S)→ γζ) ∼ 0.5%

Υ(1S)→ γ hadrons

I

-.

I I

o- 0.75 1.00 1.50 2.00

100

7- 84

80

60

40

20

20

0

-20

I I I I

I (b) -

I I I I 1 0.8 1.0 I.2 1.4

y ENERGY (GeV) 4868A1

Fig. 1


additional selection

- 80 s 0 Cu 60

I ’ I 1 I I

0.75 1.00 1.50 2 .oo

80 ’

60

> 0 5 y 30 W

20

IO

0

-IC

I I I I

-20 4 0.8 I.0 1.2 1.4

7-04 y ENERGY (GeV) 486812

Fig. 2

.


3 300 0 ni 2 200 t-

El

0.8 1.0 2.0

-- I50

,\” 0 100 ni

x 50 I I I I I

I I (Cl -I

-.

20

0

-20

-40 - 0.8 1.0 1.2 1.4 1.6

7 - a4 y ENERGY (GeV) 40bRA3

Fig. 3

Υ(1S)→ γ“τ+τ−”

--

-.

0.6 0.8 1.0

p lfl .

$0

z y IO (c) W

5

-5

-10 0.7 0.9 1.0 2.0

7 - 84 y ENERGY (GeV) 48bBA4

Fig. 4

SLAC-PUB-3380March 18, 2016 Frank Porter, Elliott Bloom Symposium 21



oh well, it was fun

More data and many checks later:

“In summary, the absence of the ζ in theCrystal Ball high multiplicity analysis and theCUSB spectra, together with the Crystal Ballstudies of their 1983 analysis and theTye-Rosenfeld model, indicate the ζ’sexistence is very unlikely”

– EDB

80

8 60

s d T P 40

ifi ?I

20

I I I II I I I III11IIlIIIIIIIIL

I ’ ” ’ 1 ‘1”1’1”~“1’1”’ 1984 DATA (b) i

Crystal Bol I

29.3 4 29.3

0 I I I I I I I IIfIIIILII~J11~11~ 0.75 1.00 1.25 1.50 1.75

5-85 ENERGY (GeV) 5118635

Fig. 19. Results on T(lS) + 7X from the Crystal Ball experiment at DORIS II. a) The inclusive photon spectrum obtained for the high multiplicity analysis using the 1983 'Y'(lS) data (100K T(lS) decays, - 10 pb -‘). b) The inclusive photon spectrum obtained for the high multiplicity analysis using the 1984 T(lS) data (200K r(w), - 20 pb -l). There is over a 4 s.d. difference between these two spectra at a mass - 8.3 GeV.

22

1983 data∼ 10 pb−1

1984 data∼ 20 pb−1

Elliott Bloom, SLAC-PUB-3686




Thanks, Elliott

Working on the Crystal Ball was great fun, great interactions, andI learned a great deal!

An old friend has returned to Germany




A few more things




Bottomonium:The Υ(1S) and Υ(2S) resonance parameters

CM energy dependence ofσ(e+e− → hadrons)σ(e+e− → µ+µ−)

Yields Bµµ, ΓµµBee

I

b) . t ia5 “‘...... . . . . . . ..( ..( ..! $2 : . . . ..._....,,., ’ 1 ‘It

, b,‘, , , ,,.,.,,,,,,

0.4

++ i+ . . . . . . . . . . . . ““M “” *

. “....““....“;“‘“““““’

0.3 FI “““““‘l”“/J/J”““““““‘/“/“““““““‘i’ I I’ 9.4 9.5 9.95 10.05 10.45 10.55

VI’ (Gel-)

Figure 1

Measured µ+µ−

Predicted, without Υ(nS)

Scan over Υ(1S)

I

-

CT b-w - 14.0

-12.0

10.0

8.0 .- _.

6.0

4.0 0.4

0.3

- 0.2

0.1

0.0

-0.1

-0.2

-0.3

-0.4

I --_ .

I 1 -_ . . . :

._ ., 1 . . ..-

9.36 9.38 9.40 9.42 9.44 9.46 9.48 9.50 H’ (Gel’ )

Figure 2

σ(e+e− → hadrons)

σ(e+e− → Υ(1S)→ µ+µ−)

ZPhC 53 (1992) 193March 18, 2016 Frank Porter, Elliott Bloom Symposium 25



Bottomonium:The Υ(2S)→ ππΥ(1S) transitions

I Crystal ball can do π0π0 andπ+π−

I branching fractionsconsistent with isospininvariance

I ππ mass distributions

I angular distributions

2894 D. GELPHMAN et al. 32

DETECTOR AND TRIGGER

The Crystal Ball detector is a nonmagnetic calorimeterespecially designed for measuring electromagneticallyshowering particles. The major component of the detectoris a highly segmented spherical array of 672 NaI(T1) crys-tals covering 93% of the total solid angle. Each crystal is16 radiation lengths long. The geometry of the array isbased on an icosahedron. Each of the 20 triangular faces,referred to as "major triangles, " is subdivided into four"minor triangles" each consisting of nine individual crys-tals. The solid-angle coverage of the Ball is extended to98% of 4' sr by NaI(Tl) end caps. The energy resolutionof

cr( E) 2.6%E 1/4

for electromagnetically showering particles makes the Ballwell suited for measuring energies of photons and elec-trons. The most probable energy deposited by minimumionizing particles is about 210 MeV. The high segmenta-tion of the detector provides a measurement of the direc-tion of photons and electrons with an angular resolutionof 1'—2, slightly dependent on energy. Tracking ofcharged particles is performed by three double layers ofproportional tube chambers with charge division readout,resulting in an angular resolution for charged tracks ofabout 1'. The direction of noninteracting charged parti-cles can also be determined from their energy depositionin the crystals with an angular resolution of 2'. The lumi-nosity is determined by measuring large-angle Bhabhascattering; a check is made by also measuring Bhabhascattering at small angles.

The analysis of the decay Y(2S)~em Y(1S) is based ona data sample of 193000 Y(2S) decays corresponding toan integrated luminosity of 60.6 pb '. The search forevents containing approximately back-to-back electron ormuon pairs plus additional energy clusters in the centralcalorimeter is performed by requiring at least one of thefollowing hardware triggers.

(a) A total energy trigger, which requires an energy sumin the Ball of more than 1.7 GeV. For m~e+e eventscompletely contained in the fiducial volume of the detec-tor, this trigger is 100% efficient.

(b) A topology trigger, which is based on the fact thatthe Ball can be divided ten different ways into approxi-mate hemispheres. This trigger requires that, for eachdivision, both hemispheres contain at least one major tri-angle with more than 150 MeV and that the total energydeposition in the Ball exceeds 770 MeV.

(c) A trigger, which requires two approximately back-to-back minor triangles each containing more than 85MeV and a total energy of more than 220 MeV in theBall.

Triggers (b) and (c) are designed to accept events withat least two almost back-to-back particles and a low totalenergy deposition. From a measurement of the triggerthresholds and a Monte Carlo simulation of the triggers,we estimate the overall trigger efficiency to be greaterthan 98% for mnp+p events fully cont.ained in thefiducial volume of the detector.

THE DECAY Y(2S)~mom Y(1S)

For events of the type nm. 1.+l ( I =p or e) we requireexactly six particles in the Ball within

~

cosO~

&0.85,where 0 is the angle between any particle and the incom-ing positron beam direction. To avoid systematic effectsdue to varying chamber performance we do not use thechamber information for charged-particle tagging or anglemeasurements in the m ~ l+I channel. All particledirections for this channel are therefore based on the ener-

gy deposition in the Ball with the assumption that theparticles originate from z =0. The lepton pair is identi-fied by finding two particles with an acollinearity smallerthan 17 (Ref. 14). Furthermore, for electron pair candi-dates each of the two particles is required to have an ener-

gy deposition of more than 3.5 GeV whereas for eachmuon candidate an observed energy between 150 and 330MeV is required with essentially all of the energy con-tained in only one or two crystals. The selection criteriafor muon candidates are based on studies ofe+e —+p+p annihilation events. The lateral energydistribution of the other four particles, the photon candi-dates, must be consistent with that of electromagneticallyshowering particles, and the energy deposition of eachparticle has to be greater than 10 MeV. In addition, thesum of the energy deposited by the photon candidates isrequired to be greater than 160 MeV. To ensure a cleanenergy measurement of the photons we require the open-ing angle between any two particles to be larger than 26'(cosO;J &0.9). For events of the type yyyyp+p we ap-ply additional cuts on event cleanliness: the energy mea-sured by the end caps must not exceed 40 MeV, and theenergy measured in the Ball which is not assigned to anyof the six particles must be less than 80 MeV.

All events surviving these cuts are kinematically fit tothe hypothesis e+e —+Y(2S)~yyyyl+I using energyand momentum conservation. This results in a two-constraint (2C) fit since the measured energies of the lep-tons are not used. ' For events passing the fit with a con-fidence level larger than 5%, we plot in Fig. 1 the two-photon invariant mass mr& of each pairing combinationversus the invariant mass of the remaining photons. The

250

200—CU

~Oo l50(D

~ IOO—E

r

50—~ ~

I0 I I I I I I I I I I I I I I I I I I I I I I I I

0 50 I 00 I 50 200 250

mzz (Mev/c )

FIG. 1. Scatter plot of the observed m~~ masses of theyyyyp+p and yyyye+e samples (three entries per event).The box indicates the boundaries of the cut.

PRD 32 (1985) 2893




Bottomonium:The Υ(2S)→ ππΥ(1S) transitions

2896 D. GELPHMAN et al. 32

number. of observed and efficiency-corrected events ofboth decay modes we obtain average efficiencies of

p=0. 10+0.01 and e 0 0 ——0.09+0.01, where the er-eem m'

' '@pm m

rors are almost entirely systematic. The main contribu-tions to the systematic errors are the uncertainties inrriodeling the detector, the simulation of the backgroundenergy in the Ball, and the sensitivity of the branching ra-tios to variations of the cuts. The overall systematic erroris obtained by adding the different contributions in quad-rature.

From the final-event sample we obtain the invariant-~ ~ -mass distribution shown as the histogram in Fig. 4.Clearly, a mass distribution according to phase space(dashed curve) is excluded by the data. We fit the ob-served mass spectrum to three different theoretical expres-sions ' ' folded with our experimental resolution inM p& of 8 MeV and the acceptance curve of Fig. 3. All

three theoretical expressions contain a term ( M ~—const) which accounts for the peaking of the dipionmass distribution at high values. Within the drawing ac-curacy, the fits to all three theoretical models arerepresented by the solid curve in Fig. 4. The functionalform and the value of the fitted parameter of each modelare listed in Table I. These values have been determinedpreviously only for the decay Y(2S)~n.+m Y(lS).Our results are consistent with those measurements. Aprevious measurement of Y(2S)~m m Y(1S) also showsa peaked dipion mass distribution, in qualitative agree-ment with our data.

We also extract from our data the angular distributionsfor cos8++ and cos8+. The angle 8 p, is the polar angleof the dipion momentum vector with respect to the beamaxis in the laboratory frame. The angle 0 0 is the polarangle of the ~ direction in the rest frame of the m.m sys-tem, where the z axis is parallel to the beam axis. Thisangle is sensitive to the spin of the n.~ system. Figures5(a) and 5(b) show the observed distributions superim-posed with the Monte Carlo prediction (solid curve),

20CU

CU

l0

5

0400 500

M~o~o (Mev/c )

FIG. 4. The invariant-m m -mass distribution. The histogramis the data without acceptance correction. The solid curverepresents the fits to the data of the theoretical expressions fold-ed with the experimental resolution in M p p of 8 MeV and the

acceptance curve of Fig. 3. The confidence level of all fits isgreater than 79%. The dashed curve shows the phase-space dis-tribution folded with the acceptance. The agreement betweenthe data and the expectation from phase space has a confidencelevel of less than 10

500

which is calculated using the measured M 0 0 mass distri-bution and isotropic decay distributions as expected for adipion system of spin zero emitted in an S wave. Thedata for cos8, are in good agreement with isotropy. Forthe distribution in cosO++ the confidence level of theagreement between the data and the prediction from iso-tropy is only 3%%uo. This low confidence level is due to thehigh number of counts at cosO p p= —0.5. We havelooked for and have found no systematic effects whichcan explain this. We believe that this high bin is due to astatistical fluctuation and that this distribution is con-

TABLE I. The results of the fit of the M mass distributions toE = [ [(M~ +M~) —M~ ][(M~ —M~) —M ](M —4M )] ' is the phase-space factor.

different theoretical expressions.

Model Mass distributiondX

dMm m result a+m. result

Yan' ~E (M „—2M„) = —0. 18 p'13+0.18 +0.01-o. 1

+0.13

(M ' —2M ')3A

(M „'—4M ')2(M '+2M„'), +0M

Voloshin-Zakharov

Novikov-Shifman'

[Kp ——(M~ 2+M ' M~~) j(2M~ )]—~X(M,2 —XM.2)2

2

~K M„—x(M~ —M~) 1+22 M+O(~ )

A —3+3 14

0. 14—o.o6+0.05

X=2. 1+007,

K' =0.08 p' p4

' References 8 and 23 ~

Reference 18.' Reference 19.

D. GELPHMAN et aI. 32

40

M

~ 30—(D

CGCU~ 20—(AI—z'.Ld

10

I & i i I

500 400 500M~+~- (MeV/c2)

FIG. 6. The invariant-m+~ -mass distribution. The histo-gram is the data without acceptance correction. The solid curverepresents the fits to the data of the theoretical expressions fold-ed with the experimental resolution in M + of 15 MeV and

the nearly flat acceptance. The confidence level of all fits is3%. We have found no systematic effect which can account forthis low confidence level and believe it is due to a statistical fluc-tuation in the highest-mass bin.

evaluated with Monte Carlo techniques and are found tobe negligible. The background due to radiative QEDevents with additional spurious energy in the detector isestimated by carrying out the above analysis on approxi-mately 30 pb ' of Y(1S) data. We find four events satis-fying all cuts. Based on twice the luminosity for ourY(2S) data, we estimate a total of eight backgroundevents to be subtracted from the final sample of 169events for the calculation of the branching ratio.

The Monte Carlo model used to determine the overalldetection efficiency incorporates the M mass distribu-tion as given by Voloshin and Zakharov' with the onlyparameter fixed at A, =2. This choice is not crucial since

, our efficiency is almost constant over the whole M +mass region. We obtain e + ——0.17+0.03, where the

error is dominated by the systematics in the determinationof the tube-chamber tracking efficiency. This efficiencyhas been obtained bg studying e+e ~p+p events andis found to be 0.90+0'12 per track.

From the final data sample we extract the invariantM + + mass distribution shown in Fig. 6. This spectrumexhibits the same behavior as that observed in our m m

analysis and that seen by other experiments. We fitthe observed mass spectrum to the three theoretical ex-pressions ' ' corrected for acceptance and folded withour experimental resolution in M + of 15 MeV.Within the drawing accuracy, all fits are again representedby one solid curve. The results from these fits, includedin Table I, are consistent with those found in the n. nanalysis and those obtained by other experiments.

We also obtain angular distributions for cos0 + andcos8*+. The definitions of these angles are identical tothe ones for the neutral mode. Figures 7(a) and 7(b) showthe data superimposed with the expectation from theMonte Carlo model as described above. Both angular dis-

30 I I I I II I I I

/

I I I If

I I I I

(a)

C)

V)

Ld

IQ—

I I I I I I I I I I I I I I I I I I

—1.0 -0.5 0 0.5COSI9„+—

1.0

30— (b)

D

(n 20—

LLj

10—

I

0.20

1.00.80.40 Q.6cos 8~—

FIG. 7. Angular distributions of the ~++ system. The his-

tograms are the data without acceptance correction. The curvesrepresent isotropic distributions corrected for acceptance andnormalized to the number of events. (a) cosO + distribution.

(b) cos8 + distribution. For a description of the angles see the

text. Note that we do not distinguish between positive and neg-ative pions. The confidence levels of the agreement between thedata and the curves are 43% and 89%, respectively.

=(4.9+0.4+1.0) &&10

With the average leptonic branching ratioBii(Y( 1S)) = (2.9=0.3)%%uo we obtain B(Y(2S)~n.+m. Y(1S))=(16.9+4.0)%, where the statistical andsystematic errors are added in quadrature. This result isconsistent with the present average value ofB(Y(2$)—+ir+ir Y(1S))=(18.8+1.0)%%uo derived from ex-clusive and inclusive measurements. For completeness,we present the ratio of our measured branching ratios forthe neutral- and charged-pion transitions. In this ratio the

tributions show good agreement with the hypothesis of anisotropic emission of a spin-zero dipion system.

From the background-corrected number of events, thedetection efficiency, and (193+15)X 10 Y(2S) events weobtain the following branching ratio:

8(Y(2S)~n+n. Y(1S))8(Y(1S)~e+e )

Dashed curve is phase space.Solid curves are fits to theoretical expressions.π0π0 and π+π− mass distributions look the same.




Tau physics

Michel parameter ρ in τ → eνν

dΓ

dx=

G 2Fm

5τ

16π3x2

[1− x +

2

3ρ

(4

3x − 1

)]x = 2Ee/mτ (in τ frame). For V − A, ρ = 0.75 (solid curve)

80

2 60

F g 40 LLI

20

0

7-89

I I I I I I I

0.3 0.5 0.7 0.9 x = E/EsEAM

6397A2

Fig. 2 PL B 228 (1989) 273March 18, 2016 Frank Porter, Elliott Bloom Symposium 28



Tau physics

Search for lepton flavor violationin τ → eγ, eπ0, eη

Phys.Lett. B 212 (1988) 123

3

entri

es

I 60

MeV

O4

.




Crystal Ball at DORIS References

K. Karch et al. [Crystal Ball Collaboration], “Analysis of theηπ0π0 final state in photon-photon collisions,” Z. Phys. C 54,33 (1992).

D. Antreasyan et al. [Crystal Ball Collaboration], “Search forD0 and B0 decays into π0π0,” Submitted to: Z.Phys.C.Using algorithm to recognize merged high-energy π0 → γγ, setlimits on D → π0π0 and B → π0π0

M. Kobel et al. [Crystal Ball Collaboration], “Measurement ofthe decay of the Upsilon (1S) and Upsilon (2S) resonances tomuon pairs,” Z. Phys. C 53, 193 (1992).

T. Lesiak et al. [Crystal Ball Collaboration], “Search forradiative B meson decays,” Z. Phys. C 55, 33 (1992).

D. Antreasyan et al. [Crystal Ball Collaboration],“Measurements of the branching ratios for the decays




τ → hadron π0ν and τ → hadron π0π0ν,” Phys. Lett. B 259,216 (1991).τ → h±π0ν, τ → h±π0π0ν and the “one-prong problem” (wemade it worse)

D. Antreasyan et al. [Crystal Ball Collaboration], “Limits onaxion and light Higgs boson production in Upsilon (1S)decays,” Phys. Lett. B 251, 204 (1990).

C. Bieler et al. [Crystal Ball Collaboration], “Measurement ofπ0 and η meson production in e+e− annihilation at

√s near

10 GeV,” Z. Phys. C 49, 225 (1991).π0 and η inclusive production and multiplicity at

√(s) = 10

GeV (continuum and Υ(1S))

K. Karch et al., “Observation of a new ηπ0π0 resonance at1900 MeV/c2 in two photon scattering,” Phys. Lett. B 249,353 (1990).




D. Antreasyan et al. [Crystal Ball Collaboration], “Observationof the exclusive decay B → eνD∗ and search for B → eνπ0,”Z. Phys. C 48, 553 (1990).Looking at high energy e± back-to-back with a soft π0, wemeasure the b → c process: B → eνD∗, D∗ → π0D

D. Antreasyan et al. [Crystal Ball Collaboration], “Firstobservation of the reaction γγ → π2 → π0π0π0,” Z. Phys. C48, 561 (1990).

H. Marsiske et al. [Crystal Ball Collaboration], “AMeasurement of π0π0 Production in Two Photon Collisions,”Phys. Rev. D 41, 3324 (1990).

W. S. Maschmann et al. [Crystal Ball Collaboration],“Inclusive J/ψ Production in Decays of B Mesons,” Z. Phys.C 46, 555 (1990).




H. Janssen et al. [Crystal Ball Collaboration], “The MichelParameter for the Decay τ → eνν,” Phys. Lett. B 228, 273(1989).

K. Wachs et al. [Crystal Ball Collaboration], “The ElectronSpectrum From B Meson Decays,” Z. Phys. C 42, 33 (1989).

S. Keh et al. [Crystal Ball Collaboration], “Search for ExoticTau Decays,” Phys. Lett. B 212, 123 (1988).

Z. Jakubowski et al. [Crystal Ball Collaboration],“Determination of Γee of the Υ(1S) and Υ(2S) Resonancesand Measurement of R at W = 9.39 GeV,” Z. Phys. C 40, 49(1988).

D. Williams et al. [Crystal Ball Collaboration], “Production ofthe pseudoscalars π0, η, and η′ in the reaction γγ → γγ,”SLAC-PUB-4580.




S. Keh et al. [Crystal Ball Collaboration], “Observation of taulepton decays to eta mesons,” SLAC-PUB-4582.

P. Schmitt et al. [Crystal Ball Collaboration], “Search forradiative Υ(1S) decays into light mesons,” Z. Phys. C 40, 199(1988).Υ→ γX , X = η, η′, f2(1270), f2(1720), or other narrowresonance below 3 GeV

D. Williams et al. [Crystal Ball Collaboration], “Formation ofthe pseudoscalars π0, η and η′ in the reaction γγ → γγ,”Phys. Rev. D 38, 1365 (1988).

D. Antreasyan et al. [Crystal Ball Collaboration],“Measurement of the η′ and Search for Other Resonances inγγ → ηπ0π0,” Phys. Rev. D 36, 2633 (1987).




B. Lurz et al. [Crystal Ball Collaboration], “Experimentalupper limits for the hadronic transitions Υ(2S)− → ηΥ(1S)and Υ(2S)→ π0Υ(1S),” Z. Phys. C 36, 383 (1987).

T. Skwarnicki et al. [Crystal Ball Collaboration], “Spin analysisof the χb states,” Phys. Rev. Lett. 58, 972 (1987).

W. S. Walk et al. [Crystal Ball Collaboration], “The χb statesin exclusive radiative decay of the Υ(2S),” Phys. Rev. D 34,2611 (1986).

D. Antreasyan et al. [Crystal Ball Collaboration], “Formationof δ(980) and A2(1320) in photon-photon collisions,” Phys.Rev. D 33, 1847 (1986).

D. Gelphman et al. [Crystal Ball Collaboration], “Measurementof the decay Υ(2S)→ ππΥ(1S),” Phys. Rev. D 32, 2893(1985).




R. Nernst et al. [Crystal Ball Collaboration], “Observation ofthree P states in the radiative decay of Υ(2S),” Phys. Rev.Lett. 54, 2195 (1985).

C. Peck et al. [Crystal Ball Collaboration], “Evidence for anarrow massive state in the radiative decays of the upsilon,”eConf C 840723, 020 (1984).

C. Peck et al. [Crystal Ball Collaboration], “Crystal Ball 1984Proposal,” DESY-PROPOSAL (1).

D. P. Barber et al. [ARGUS and Crystal Ball Collaborations],“A precision measurement of the Υ′ meson mass,” Phys. Lett.B 135, 498 (1984).




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