N~clear Physics B (Proc. Suppl.) 13 (1990) 261-269 261 North-Holland

CHARMED SEMILEPTONIC B MESON DECAYS *

Sheldon STONE

Wilson Laboratory, Cornell Univ., Ithaca N. Y. 14853 USA

Recent 8 meson semileptonic branching ra t io measurements are summarized and appear to be lower than theoret ical expectations. Measurements of the exclusive f i na l states D°~'u, De°~'~, D*~E"~ and D**~ '~are reported. The ra t io of rates D*°/D ° and the polar izat ion of the D e+ are shown to be consisten¢ with theoret ical models. F ina l ly comparing the D*°~-uand D ~ [ ' ~ rates, the

.22 l i fe t ime ra t io of neutral and charged B~s is shown to be equal t;o 1.18,0.27+°.a O.

1. INTRODUCTION

Theoretical models of heavy quark decay

apply to both the O and B systems. Models of

semileptonic decays are the simplest.

Measurements in D decays of the re la t i ve widths

for K*£u versus K£u are lower than model

predict ions and the K * po lar izat ion is larger

than model predict ions. 1 Here I w i l l describe

s imi lar , but poorer, measurements in B decays.

F i rs t , however, I w i l l summarize our knowledge

of the average semileptonic branching ra t io of

B°and B" mesons and some recent resul ts from

CLEO on the B ° semileptonic rate.

2. INCLUSIVE SEMILEPTONIC DECAYS

Spectator model predict ions 2 of the

semileptoni¢ B branching ra t io BsL=B(B4Xev ) are

16S. ~CD correct ions enhance the hadronic width

and lower t h i s expectation by 25~. 3 An

albernat lve theoret ical approach using the 1/N

expansion can dr ive the predict ion as low at

12~. 4 Although many 9roMps in the past have

measured BSL , I w i l l summarize only recent

ones. 5 The lepton momentum spectrum has two

components, one from B*XI~u and the other from

the cascade B~DX, D+Y£u. (See f igure 1.)

* Vork u-ppo,tod by the National 8cfen=e Foundation.

CLEO ozsoTee-oo5 i I i i i

o E leclronI x Muons

0.20 . ~

0.15

\'IL / - b - :'°°- " 0.o5 :j .-\

0 I 2

Momentum (GeV/c)

FIGURE 1

Momentum Dis t r ibu t ion of muons and electrons

from B decay. The contr ibut ion from the

continuw, below the T(4S) has been subtracted.

The dashed curve is the expected spectrum for B

decays to charmed mesons and the so l id curve is

the spectrum from B decays to charmed par t ic les

which subsequently decay into leptons. The

histogram is a f i t to the data using the two

curves.

0920-5632/90/$03.50 © Elsevier Science Publishers B.V. (North-Holland)

2~2 S. Stone/Charmed semileptonic 13 meson decays

T o ~ m i n e ~ S L A R ~ U S f i ~ s the lepton

s ~ u ~ t o predictions of theoretical models

a~ovep~of 1.4QeV/c (or in so~ecaseel.7

~Y/©) in order to r ~ o v e ~ s t of the iep~ons f r e d d~ay. CLEO f i~s the ent i re spat,rum for

~ c ~ p o n ~ s . One theeretical model,

A | ~ r e | i i e t a l . , 6 (ACM) is b~sedon free quark

decay an~ in~udee one gluon corrections and

F~rmi ~ e s t u m o f the b-qu~rk. The other models

calcula~ ~ p | i c i ~ f inal s~ t~s : D~, D*~aed, |node©ass (ZS~), D**~.~.7They calculato~he

exclusive ~ id~s in ~er~s of meson fo r~ fac tors ~icht~eymat~:h with qu~rkmedel wave functions. ZS~Mt~:h atmximummomntum transfer (q2) where the rate is the largest while V i ~ 8 and KS 9 m~tch at qZ=O where the

meson I~smaximal momentum. The r e s u l ~ o f the

fi~,s ~o the data are given in Table Z. The CLEO results are unpublished numbers ~eriv~d in Ko~l~ski+s~h~s~s 10 and represent the most

c(mprehensive analysis of CLEO*s 1985 data sample.

Table ~: 8 ~ s o n S~i leptonic Branching Ratio Mo~l AR(IJ~ ~1 CLEB Crys~l Ball 12

AC~ 10.1~0.7~ ~0.1~0.5~ 12.0"0.5~

8.7~0.5~ g.3~0.5~ 10.8~0.~

There i~good agreement between CLEOand ARQUS whlc~ measure both e's and ~'s using

magnetic ~omentum analysis. BSL appears to be

approxi~te ly 10~. Crystal Bal l '~ electron

~ s u r ~ n ~ is somewhat higher. BSL appears to be lower than any expec~tion.

One possiblesource of leptons that hasn:t been considered are those coming from the

reaction B"'+AC+~..,."~. These lepton have a sof t ~ n t u m spectrum and would not be included by the f i t s to the da~ in the above quoted

exper i~nts. An estima~ of the magnitude of th is e f f ~ t uses the CLEO measurement 13 of

Br(B+ACX)=7.5~ multipl ied by the expected

s~ i lep ton ic branching rat io in these decays.

This is about20Z since the v i r tua l W canner

materialize as~s or ~ . Thus there can be an additional 1.5~ which could add ~ the IO.SSto

raise BsL to 11.5S s t i l l a l i t t l e below the theoretical expectation. On the other hand, al l

A C production in B decay could proceed via mechsnim which don' t have semileptonic decays so th is correction is somewhere between 0-1.5S.

3. THE B ° SE)GLEPTONZC B,~ICHING RATZO

The T(4S) resonance decays to B-B + or B°i °.

The f ract ion of decays to the charged and neutral B's modes has not been measured d i rec t ly . Di f ferent numbers would arise from

d i f ferent amounts of phase space caused by d i f ferent B mosses. Previous CLEO measurement

gave 2.0~1.1MeVmoremassto the B°than the 13". 14 Using th i s central value and p-wave phase

space, CLEO found 431 neutral B's and 57~ charged B's. A new, preliminary, CLEO mass

difference measurement, based on the data shown

in f igure 2, is -0.2t0.6 MeV. I f the mass

difference is zero there can't be any

difference between the charged and neutral B

fract lons. Zn the rest of th is paper, 1 wi l l

assume th is is the case and that the fract ion

of charged or neutral B's on the T(4S) is equal to 1/2.

By looking at the re lat ive numbers of single

lepton events and dilepton events, CLEO had

previously constrained the ra t io of B~L/B;L to

be between 0.+4 and 2.05, I now discuss recent di rect measurements of B~l.

v ~

The f i r s t method uses a sample of "tagged"

B° 's to investigate the decay of the other B °

meson in the event. Samples of B ° mesons are

found by I pa r t l a l l y " reconstructing the decays

i%D*+~ "- and B°+D*+~'~. Procedures for

selecting the la t ter channel w i l l be discussed later. Here m+J throughout th is paper, charge

conjugate r=~ctions are also used. D*+~" are

found by using t h e ~ from D*++~+D° decay

S. Stoae / ChaJrmc.i semileptoaic B meson dec~ys 2~3

40.0

30.0 f

20.0 f

1 7 7 0 6 8 9 - 0 1 5

, : . • I : • ° ' I " " ' ° 1 . . . .

B" Moss I:::],:<- 1o ~ o o -

I0.0

0.0 u 5.200 5.225 5.250

Moss (Ge~

t | o • , • : | ! |

40.0 i B ° Moss

[] D = * ~ " L Ill D =* s'-

30.0 | m #K-~r~(Non-resonont)

20.0

I0.0

0.0 5.200 5.225 5.250 5.275

5.275 ~.~C,O

1 7 7 0 6 8 9 - 0 1 6

[ : i ~ i

(b

i |

5.300

Moss (GeV)

FTcURE 2

Ful ly reconstructed B meson decays from CLEO.

a) is for charged B's and b) for neutral B's.

without f ind ing the D °. Events with a fast w =

and slow r + with the cosine of the angle

between the two pions (-0.8 are searched for . A

B mass is then calculated by a t~:hnique which

e f fec t ive ly maxi=izes the p o s s i b | e u s s v a l e

for a given track ps i r . This B mass

d i s t r i bu t i on is shown in f igure 3 along with

the mss d i s t r i bu t i on found for l i ke ¢ ~ r ~

pion pairs. The Fox - t~ l f rms~ :pe v a r ~ | e 15 R 2

is required to be l e s s ~ n O.Sto r,c~ceCP~

conbinuum contr ibubien. The f i t t ,~trough the

data gives 336*40 B ° events ~ ich~ aft;or

ef f ic iency correct ion, t ranslates into

B(B°~D~r')==O.49*O.O6*O.O~and is cc~slstdmt

with the value found by f u l l reconstruction. 5

t 480~"

420

> 360 : S t ~

300

240

180

12C

60

| 7 7 0 6 a | - ~ 4

'{,,T

' ' I ! ! II ! s !

5.12 5.16 5.20 5.24 h2a B Moss (GeV)

FI(~IRE 3

Themss spectrum of candist~s for i%D*@~r "

using a par t ia l reconstruction technique. The

histogram is D*÷tr ~ candidates.

Although the signal to background ra t io is

poor, i t turns out that 80~of the background @ -

i s from lepton-poor continuum • e

annih i la t ions and can be d i rec t l y s u b t r a c t .

The remaining background from the T(4S) is

evaluated using the cont inumsubtractad event~

which rmain s t masses jus t below the B mass.

2~ S. SCone/Chimed semfleptonic B meson dec&ys

iept~ns of mmntum grem~er than 1.4 QeV/c

ar~ c o u n t . The con t r ibu t ion from semi leptonic

O ¢iecays is re~mv~ and the resu l t i ng B~L=

9 . ~ 2 . ~ ( p r ~ | i ~ i ~ r y ) . The number from the

O*÷~ e v ~ t s is 9.1,3.4~ (pre l iminary) which

~ a v e r e ~ gives g.4~2.0~, censiston~ wi th

• ver~3~ ~SL"

~o~,her intor~st ing~ but no~ dec is ive

r e s u i ~ c~ms from ~ust tagging s O ~ . Here

CLEO looks fo r an ~.~ to insure t ha t the lepton

comes from the other B. They f i nd

8 ( I ~ L ~ ) / B ( ~ D * ~ X ) : 7.1"1.9~. He,ever, there

~mst be a correct ion fo r ~ mixing because when

a ~ mixes i t wi I | no longer decay in to an ~..~

but in to an #.-. This mixing cor rec t ion can be

done esact ly i f i~ is t rue t h a t D *÷ are only

predu=ed by B°:s. Then the corrected resu l t is

B~L = 9.2-2.2~.

4. THE REACTION ~%D*÷e.'~ Candidate events are i den t i f i ed by f i nd ing

1 ? 7 0 6 8 9 - 0 1 8

1500 . . . . , . . . . ~ . . . . I . . . . I . . . . i . . . .

Q

3 ( n

q .

e c¢

IO00

500

. . . . B ÷ - DaW(2420) 1%

- - B ° - Dm-X,--I-X Mixing

. r

0 . . . . I . . . . I . . . . | , ,

-I0.0 -7.5 -5.0 -2.5 MM =

FIC~RE 4

The W 2 spec~r~ fo r three d i f f e r e n t processes resu. l t i ,g in a D** and an ~.-.

0.0 2.5 5.0

D *~ and L" and then ca l cu la t i ng the missi:,g

mass sqn red g iven by

where E B is known beam energy, S 0 and PD refer to the m s u r e d D *~ candidate energy and

momentum, E L and P~. re fe r to the lepton and ~B

is the unknown B momentum. Ac tua l l y IPBI i s

known to be 320 MeV but the d i r ec t i on is

unknown. The best guess is made by ~.4king ~B--O.

Di f fe ren t processes f o r producing D *÷ and P."

lead to d i f f e r e n t shapes in MU 2 as shown in

f i gu re 4.

This technique was pioneered by ARGUS. 16

There are new, pre! iminary, ¢LEO resu l t s which

i w;[ ! de.~crlbe. The gU 2 d i s t r i b u t i o n s from

CLEO are shown in f i gu re 5 fo r D ~'÷ P.- " r i g h t -

s ign" events and D ~÷ JL ÷ Wwrong-sign" events,

f o r 2.4OeY/¢ ) pp. ) 1.4 OeV/c. D *+ are found by 1 7 7 0 6 8 g - OI I

1 . . . . •

m

[ ( b ) Wrong Sign

t -I0.0 -7.5 -5.0 2.5 0 2.5 5.0

MM~(GeVZ)

FIGURE 5

The gU 2 from the CLEO data. The histograms are

f i t s to the data using the var ious components

shown on the p lo t s . (a) is fo r D*÷~ "

combinations, wh i le (b) is fo r D*÷~ ~

combinations.

S. Stone/Charmed semileptonic B meson decays 2~5

the i r decay into ~÷D ° where the D ° subsequently

decays into K-~ + or K-~+~+~ - . The D *+

background was estimated by using O *÷

sidebands. The other curves are determined by a

f i ~ t o t h e data le t t ing the normalizations of

each component vary. CLEO expresses the i r

resul ts in terms ra t i o ' s . The denominator is

taken as BSL. They f ind Br(B°~D*~&'~)/Br(B÷X£~)

= 0.46~0.05~0.07 where the las t error is due to

the measured errors on the D *÷ and DO branching

ra t ios . CLEO also f inds weak evidence for a D**

or D*~ component,

Br(B%D**~E-~)/Br(B*X~) = 0.18-0.11~0.03.

The amount of D** is rather large (and has

large er ro rs ) , but i t is agreemnt with

predict ion Of 13~ for D == in the IS~Wmodel. 7

These rates are based on the assumption that

the production of neutral

at the 7(4S) are equal as

mass measurements.

I f we take BSL as 10£~

B~s and charged B~s

implied by the recent

The quoted value from the or ig inal ARGUS

measurement is 7.0,1.2,1.9~. However the

dif ference in the CLEO and ARQUS numbers is

merely the resu l t of using d i f fe ren t

mu l t i p l i ca t i ve factors rather than a difference

~ actual measurements. ARGUS assumed a charged

~ neutral B ra t io of 55/45, Br(DJ%~+D °) of

49~ rather than the newer value of 57S that

CLEO uses and a d i f fe ren t factor to account for

the f rac t ion of the lepton spectrum above the

lower lepton momentum c u t o f f . CLEO uses the

model of ISGWto account fo r the lost leptons.

ARG~I~ u~es a value of 0.75~0.08 as the f ract ion

above 1.0 ~eV/c while the IS~W model gives

0.88. Putt ing these three factors together

scales the AR~JS number to 4.6~.

The polar izat ion of the D *~ can be used to

d is t inguish among models of semileptonic heavy

quark decay. This has been done for D~K*E~

decay by E6911 and was f i r s t ~one in B decay by

ARGUS. 15 They selected D * ~ " events with M~ 2

close to zero and required t ~ m t p E ) 1.0 ~eV/c.

The angular d is t r ibu t ion of tF.~ D ° in the D ~÷

rest frame with respect to the D *~ d i rect ion in

the laboratory is then investiga~=d and f i t t e d

to the form

(Z/N)dN/dcose = t • = cos20. (2~

= relates the amount of longitudinal O ~+ to

amount of transverse, a = ~i'L/rT-1. They found

the polar izat ion parameter = = 0.7~O.g.

CLEO uses events with pp.. ) t . 4 ¢=eV/c, since

they are worried about contamination f ron

leptona from D decays. They select events with

W 2 consistent with zero (wi~hin *:lQeY 2) and

f i t for the number of D~+'s. This removes the 177o5~J--oo7

ARGUS

i

.3

.2

0

z -%

I

!

1.0 -.5 0

COS IO ~1

l.O

FIGURE 6

The angular d is t r ibu t ions of t;~e D ° in the D ~

rest frame with respect to the l) ~ l ine of

f l i g h t in the laboratory for both CLEO and

ARCUS.

2~ S. Stone~Charmed semi!eptoaic B meson decays

pro~|e~ of how to account for fake ~*÷=s. They

fi~¢i ~ = 0.7~0.7 The number of events in

d i f f e r e ~ ¢os8 bi~s from both groups is shown

in f lgare 6. The reeul~s are compared with

predict lons of three theoret ical models in

f igare 7. The KS and IGS~ models are in

agreeamnt with the me~sur~nts . 1 7 7 0 1 8 9 - 0 1 9

5

3

2 ARGUS GLEn

0

- I . . . . ~ ' ', , ~ t _ _ . , 0 0.5 1 1.5 2

LOWER P~ CUT-OFF IGeV!

F I ~ E ?

¢o~parison of some of the mode~s with the data.

The p r e d i c ~ ~. is integrated from the lower E~.

cu~=of~ ~o 2.4 GeV/c.

5. THE REACTIOHSB'*D°E'~AND B%D*°E-~

Let us f i r s t consider the inc lus ive rates of

charm meson production for PE > 1.4 GeV/c. The

CLEO i n v a r i a n t m s s spectra for candidate D°~K"

~ a n d D%K'~÷~ ÷ events when an~" is present

are shown in f igures 8a and 8b respectively.

After correct ing for ef fects of semi|~ptonlc D

decays, and BSmixing the resu l t ing rates are:

8r (e÷D°x~-v ) /e r (e÷x 'e~ ) = o .Ts .o .og and

er(S÷~÷Y~=u)/er(S÷X'~v) = o .s2 ,o .o8 .

The error bars contain s t a t i s t i c a l and

s~st~matic errors but do not include the

uncer~ in t lee in the D branching rat ios (which

are 13~). The sum is 1.05*0.12,consistent with

other data showing that charm dominates the

semile~to~ic r~es . 17 Zt ~|so implies that the

centre| values of the O branchln~ rat ios are

more or Oess correct.

1 7 7 0 6 8 9 - 0 0 8 ! i I ! ! ! I

0 On T(4S) O ) n Continuum (Scaled)

400

30O

= 200

On T(4S) Continuum (Scaled) ( b

i ! i

I O O ~ _

I~0 I~0 2DO 2.20 M ( K - v+T÷) (GeV) FIGURE 8

The charmed meson candidate mass d i s t r i bu t i on

in events containing a E-. (a) :s for K'w÷mass

comblnatlons and (b) is for K'w÷w ~

combinations. The points are for data taken on

the T~S) whi le the histograms are for data

taken at center-of-mass energies j us t below and

have been scaled to account for the dif ference

in Iominosit¥.

S. Stone/Charmed semileptonic B meson decays 26?

CLEO has taken the concept of using the

missing mass squared d i s t r i bu t ion one step

fur ther . They calculate MM 2 from events with a

D ° candidate andS- when the D°÷K-f +. The idea

here is to be able to ext ract branching ra t i o ' s

for B'+D°E'~ and B-+D*°E-~. The MM 2

d is t r i bu t ion is shown in f igure 9~ fo po > 1.4

OeV/c. There is a clear peak near MM 2=0 ~with a

great deal of background. The data have been

continuum subtracted. Also shown is the

d is t r i bu t ion of the continuum subtracted D °

sldebands. (In p lo t t ing th i s la t te r

d i s t r i bu t ion the K and • 3-moments are

constrained so that the K~ invar iant mass is

that of the Do.)

After sideband subtraction the MM 2

d is t r i bu t ion appears as shown in f igure ~0. To

ext ract branching rat ios certain components are

i 7 T 0 6 ~ 9 - 0 0 9

oJ 3>

F3

I00

80

60

4O

20

D c Even',s r~ D ° Sidebond Events

+tt +

-I0 - 8 -6 - 4 - 2 0 2 4 M M2(GeV 2)

FIGURE 9

The MM 2 spectrum from K'f+~ - . The data have

been continuum subtracted. The data points are

those for which the K'~ + are close to the 0 e

mass while the histmgram is fo r D ° sidebands.

80

m 60

W

2O

-I0.0 -7.5 -5.0 -2.5 0 2.5 5~ MMZ(GeV) 2

FI~JRE lO

The sideband subtracted p/~2 spectrum. The

histogram is the f i t to the various components

as indicated on the f igure.

f ixed. The ra t io of the D=* te 9" is f ixed from

the previously discussed analysis of C h e w 2

from D*+E - events. The dot dashed curve is

f ixed te the calculat~KI amount of mixing and

fake leptens. The data are then f i t ~ ¢ l for the

magnitude of the 9°~"u component (sol id curve}

and the magnitude of the sum of D*°~'u ÷ D*+~"~

(dashed curve). The dotted curve is the D**

component. The D°~'u part comes d i rec t l y out of

the f i t , while the D * ° ~ is derived by

subtracting the previously determined D ~÷ part

from the f i t of the sum.

One immediate resul t of the f i t s is the

ra t io of branching rat ios

Br (B-+O*°~'~)/mr (B-+DOC-~) = 1.6.0.8_0 .S . + ° ' ;

The s ta t i s t i ca l error includes the correlat ion

between t hsD ° and D *° rates from the f i t . The

syst4makic error is given by varying the

D*e/D *~ rate. The rate has been correct~sd by

the f ract ion of leptons expected above 1.4

QeV/¢ in each mode by usins the ICSWmodeU. To

proceed fur ther I assume that the charged and

neutral B f rac t ions on the T(4S) are equal.

Again~ the resul ts are expressed in terms of

rat ios to the average BSL above a lepton

268 S. Stone/Chimed seraileptonic B meson decays

~ n c L , , of 1.4 GsV/c. The resul ts are:

0 . 2 4 - 0 . 0 8 " Sr (8-.~)o~-;)/Br (B÷X~.--~) = ÷0 0~

o.s o . 0 8 _ 0

~r(B'*D**°t.'u)/Br(B~X~"u) = 0.16,0.10,0.03,

and the sum = 0.79,0.15-0.11

The amount missing 0.21~0.19 is consistsnt

with zero.

In the model of Wirbel and Bauer 18 (WB)

there is a free parameter which they cal l

JB/JBo. This paramoter represents the i r

i nab i l i t y to calculate some of the coef f ic ients

of the form factors. In f igure 11 the CLEO

polar izat ion moasure~ent and vector to

pseudoscalar ra t io in semi leptonic decay are

compared with the ~B predict ions for p~. > 1.~

¢~eV/c and r e s t r i c t 0.62 (JB/JBo( 1.08. (In t h i s

~ n t u m region, the V/P ra~io is scaled up by 1 7 7 0 6 8 9 - 0 1 7

6 , 0 ' ' ' I ' ' | ' ' ' I '

Pe > 1.4 GeV/c/" /

/ 5.0 /

/ ,/

/ °

" ° / .-" i ~ ~ -~

./" IUpper limil on "" -

~ ° ° ° I " '

,,-'" Allowed Range of I . . . . . -" :

* " °

1.0 ~~"~"- Upper h'mi~ on G ~ I

(CLEO} !

0.0 -J ~ I , , , I , , , !I , , , 0 . 5 0 0 . 7 0 0 . 9 0 1 . 1 0 1 . 3 0

JB/a~

FIGURE 11

The curves lab;ed R and e refer to the

predict ions of the ~mode l as func~ioL of the

free parameter JB/JBO for p~ ) 1.4 GeVjc. The

range is l imited on the low side by th~ CLEO

.~asurement of a and on the high side by the

CLEO measurement of R=F (B%D*°~"u)/r (B%D°~'~).

The 90~confidence level upper l imi ts on • and R were used.

a factor of 1.36.) The s imi lar p lo t in the case

of D decay gives JD/JDO equal to about 0.6.

6. ANOTHER MEASURE OFT HE B°-B - LIFETIME RATIO

The semileptonic widths of B ° and B- into

~heir respective D R channels are expected to be

equal. Since BsL--rSL/rto t and Fro t is inversely proportional to the l i fe t ime j we have that

Br(~%D*÷~-~)/Br(B%D*O~-~) = ~o/~-. We can

compare the measured values of the two rat ios

8r(~°~D~÷L'~)/Br(B4X~-u)--0.46*O.05 and Br(B-

• D*°L'u)/Br(B~X~-~) = 0.39*0.08 to obtain

~o/~- = 1.18,0.27÷~ .22 - . 3 0 "

The systematic error resul ts from varying

the D ~ component in the f i t s and from the

inaccuracy in the D ~÷ t o r s o ° branching ra t io .

This resu l t represents the most accurate

determination by CLEO of t h i s quant i ty. I t is

interest ing to note that lowering the B °

f ract ion on the T(4S) would increase th i s

ra t io . Since theore t i ca l l y i t is expected that

~o is less than or equal to ~-, t h i s would push

the resu l t in the wrong d i rect ion.

7. CONCLUSIONS

The average B semileptonic branching ra t io

!s lower than theoret ical expectations and

cer ta in ly in the range from 9.5-11~. Asid8 from

th is , theoret ica l models seem to be able to

match the semileptonic B decay data.

Results on exclusive semileptonic decay

rates are becoming avai lable from CLEO and

ARm. The data much of i t new and preliminary

indicate tha t ~o and B" have s imi la r decay

rates in contrast with O ° and D ÷.

The l i f e t ime ra t i o of charged and neutral

B's, ~ o / ~ - is measured by CLEO as

1.18"0.27~ "22 by using measurements of the . 3 0

exclusive branching rat ios Br(B°*D*÷L'~) and

Br(B%D~°~'u). I t is apparent that the B ° and

B- do not have the large l i fe t ime differences

that the D ° and D ÷ have. The Br(B÷D*÷~'~) is

measured as 0.46*0.05*0.07 for an average B

S. Stone/Charmed semileptonic B meson decays 2Gg

semileptonic branching ra t io of 108 the to~al

semileptonic, while the D**÷ID *+ ra t io is found

1;o be about 38£. Here D** can include

contr ibut ions from non-resonant D*7

combinations. The ra t io of vector to

pseudoscaler, D*°E'~/D°E-v +0 7 = 1 . 6 ~ 0 . 8 _ 0 ~ 5 , is consistent with model expectations. The D *~

polar izat ion coupled with the above measured

ra t io places res t r i c t i ons on the models.

With ARGUS taking data and CLEO I I about to

s ta r t up, we can expect s ign i f i can t

improvements in these measurements in the next

few years.

REFERE~ICES

1.

2.

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B. Gittelman and S. Stone, "B Meson Decay", in High Energy_Electron-Positron

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g. J. Q. Kor~r and Go A. Schuler Z. Phys. C38 (1988) a n .

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K. Wachs e~ =1., Z. Phys. C4___22 (19e9) 33.

M. S. Alam et a l . , Phys. Rev. Left . 599 (lo87) 2 2

C. Babek e t a | . , Phys. Rev. D36 (1987) 1289.

15. Q.C. Fox and S. Wo|frama Physo Rev. ~ t . 41, (1978) 15811 we use R2==H2/~.

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17. S. Behrends et s | . , Phys. Bey. Le~t. 59 ( t g u ) 407.

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