Sacha Kopp, Univ. Texas -- Austin 1 Search for CP in Rare B Decays Sacha E. Kopp, University of...

Sacha Kopp, Univ. Texas -- Austin 1

Search for CP in Rare B Decays

Sacha E. Kopp,University of Texas – Austin

for the CLEO Collaboration


Rare B Decays

• Tree decays bu vs. bc suppressed by |Vub|2/|Vcb|2 ~ 0.01

• Additional |Vus|2/|Vud|2 ~ 0.04 for K

• Expect tree dominantly buud.

• Decays bs,d GIM-suppressed

• Loop diagram (mt/mW)2.

• |Vtd|2/|Vts|2 ~ 0.01

• Expect penguins dominantly buus.

u

u

su

u

K

uu

s

u

Tree:Tree:

Penguin:Penguin:

du

su

K

du


CP Asymmetries

• Measure B and B reactions described by two amplitudes:

(Bf) = | a1ei(1+1) + a2ei(2+2) |2

(Bf) = | a1ei(1+1) + a2ei(2+2) |2

• CP asymmetry from strong and weak phase differences

sin(1

2)sin(1 2 )

• Depends upon comparable magnitudes as well

• CLEO can measure decays that are sensitive to = arg(Vub*)

BK, BK, BK’


ACP Predictions

• Factorization model calculations (no FSI interactions)

Ali, Kramer, Liu, hep-ph/9805403» K 0.04 - 0.11 » K 0.03 - 0.09

» K 0.01 » K’ 0.02 - 0.06

» -0.12 - +0.02

• Final state interactions may boost ACP ~ 20 - 40%.»He et al, Phys. Rev. Lett. 81, 5738 (1998) »Neubert, JHEP 9902, 014 (1999)»Deshpande et al., Phys. Rev. Lett. 82, 2240 (1999)

• New physics could boost ACP ~ 40 - 60%.»He et al., hep-ph/980982


R* (1-R*)/3/2 |EW - cos|

• Fleischer-Mannel (Phys. Rev. D57, 2752(1998))

(BK)(BK)

• Neubert-Rosner (Phys. Lett. B441, 403 (1998))

(BK) 2(BK)

from Decay Rates

R sin2CLEO: R = 1.01 0.26

• Also model-dependent fit to many CLEO branching ratios of , K, , (Wuerthwein et al. hep-ex/9910014):

84 < < 154 (90% C.L.)

0.58 0.74 | (0.64 0.15) - cos|


CESR Ring/CLEO Detector

• Total 14 fb of ee collisions

• ~ 1/3 at s = 10.520 GeV to study continuum ee qq (q = u, d, s, c)

• ~ 2/3 at (4S) resonance. BB ~ 1 nb

9.7 106 BB pairs

• Symmetric collider PB ~ 300 MeV/c

• CESR Phase II peak instantaneous luminosity: 8.3 1032 cm-2 sec-1

• Recorded 4.4 fb in 1998 alone, stored 36 bunches/beam, 260 mA/beam

• Phase III underway now

Mass (GeV/c2)

Rat

e (n

b)

1998 1996 1997

Mon

thly

Inte

grat

ed L

umin

osi ty

(pb

-1)

off on


B K/ Topology

B KB K

e+e- qqe+e- qq

• Pdaughter ~ 2.55 – 2.85 GeV/c

(higher than for bc decays)

• Major background from e+e- qq “continuum”

• Continuum events are “jetty” in topology

• PB ~ 300 MeV/c BB events “spherical”

• Continuum suppression from ML fit to several kinematic and topological variables (more efficient).

• Continuum suppression factor of ~ 106, efficiency for K/ of ~ 40%


K/ Separation

(dE/dx - Expected)/

PionsKaons

E (GeV)

K

• E resolution studied with D0 K() mass resolutions

E E dE/dx

CLEO II 25 MeV 1.7 1.7

CLEO II.V 20 MeV 2.1 2.0

• K vs. from dE/dx in drift chamber»Resol. confirmed with D*D, DK

• Also separation from kinematics:

E = E + E - Ebeam

CLEO data


Fit Results for B hh

• KK yield is 0+3.4 events set to zero

• Restricted fit for …

20.0 +7.6 4.2 K 80.2 +11.8 11.7

• First observation of a mode!

• If remove 3 events with highest likelihood, still 3.4 significance.

N(K)

N( )

- 0.0

- 6.5

- 11.0


BK and B

• Cuts applied on E and topological variables to make these plots.

• Results in ~ factor 2 loss in efficiency

• Can perform similar procedure to look at other distributions (E, Fisher, etc).

B Mass (GeV/c2)


Signal (events)

# (%)

BR (10-6)

20.0 + 7.6

21.3 + 9.7

-

4.2

3.2

-

48

39

-

4.3 + 1.6 0.5

< 12.7

-

K

K

K

K

80.2 + 11.8

42.1 + 10.9

25.4 + 6.4

16.1 + 5.9

11.7

6.1

7.6

4.9

48

38

14

11

17.2 + 2.5 1.2

11.6 + 3.0 1.4

18.2 + 4.6 1.6

14.6 + 5.9 + 2.4

KK

KK

0.7 + 3.4

1.4 + 2.4

0.0

1.1

48

14

< 1.9

< 5.1

BK, BSummary

-6.5

-6.5

-11.0

-9.9

-5.6

-5.1

-0.0

-1.3

- 1.4

- 2.4

- 2.7

- 4.0

- 5.1 - 3.3


B, B

Signal (events) # (%)

BR (10-6)

31.0 + 9.4

29.8 + 8.2

5.6

5.4

12

30

27.6 + 8.4 4.2

10.4 3.3 2.1

-8.3

-8.3

-7.4

B Mass (GeV/c2)

K

28.5 + 8.2

7.9 + 6.0

6.2

2.1

26

26

11.3 + 3.3 1.4

< 7.9- 7.3

- 4.7

-2.9

•Greater challenges from feed-across ()•Results soon on 00 and 0+.•Inconsistent with non-resonant Bhhh


• Look for ’ decays

• Look for , decays

B

’K

B Mass (GeV/c2)

’K

B Mass (GeV/c2)

• Fit for (’)K and (’) simultaneously

• Efficiencies ~ 2 - 9% for these modes


Signal (events) #

BR (10-6) Prediction*

K’

K’

KK

101 + 15

39 + 8

2.2 + 2.8

0.0 + 3.2

16.8

12

0.8

0.0

80 + 10 7

89 + 18 9

<6.9

<9.3

21 - 41

21 - 41

2 - 4

2 - 4

KKK’

K’

19.2 + 6.0

15.8 + 6.5

11.1 + 12.7

7.8 + 7.7

4.8

5.1

1.8

1.8

26.4 + 9.6 3.3

13.8 + 5.5 1.6

<35

<24

2 - 3

2 - 3

0.3 - 0.4

0.1 - 0.4

B Summary

-14

-7

- 4.5

- 9

- 4.6

- 16

- 4.2 - 8.2

- 2.2

- 0.0

- 5.7

- 8.0

* Ali, Kramer, Liu, hep-ph/9804363


CP Asymmetry Systematics

• B flavor tagged by high momentum track

• Must demonstrate reconstruction not charge dependent.

• Charge difference in K-N and K+N cross sections

• Track reconstruction difference confirmed in Monte Carlo ~ 0.002


CP Systematics (cont’d)

• Likelihood fits heavily dependent on tracking resolutions

• See no CP asymmetry in reconstructed D0 mass --even in tails of resolution.


dE/dx Uncertainty

• dE/dx used in likelihood fit

• Charge asymmetry checked with D0 K+(0) decays

• No asymmetry observed -- even in tails of resolution

• Assign systematic error 0.01

(dE/dx – Expected)/


CP Asymmetry Results

80.2 + 11.8 events

42.1 + 10.9 events

25.2 + 6.4 events

101 + 13 events

28.5 + 8.2 events

K+

K0

K+

K

+

ACP

- 11.0

- 9.9

- 5.6

- 12

- 7.3

90% C.L.


CP from New Physics?

• Penguin amplitude |Vts|

• Other amplitudes, CP, small in SM

• Some Higgs models introduce CP, possibly even if bs rate unaffected.

»Wolfenstein & Wu, Phys. Rev. Lett. 73, 2809 (1998)»Asatrian & Ioannissian, Phys. Rev. D54, 5642»Kagan & Neubert, Phys. Rev. D58, 094012 B Candidate Mass (GeV/c2)

126 15 events


bs Results

• Upper limit on bd exclusive penguins:

BR(B()) < 10-5

• Updated branching ratio results:

BR(B0K*0) = (4.50.70.3) 10-5

BR(B+K*+) = (3.80.90.3) 10-5

• CP asymmetry from special kinematic region for best K/ identification

• CLEO result: ACP = 0.08 0.13

• Asymmetry for inclusive bs (based on 3.3M BB pairs only):

-0.09 < ACP < 0.42 (90% C.L.)

Monte CarloMonte Carlo


Search for bd

• Expect that Balso described by penguin amplitude dominant top?

(B ) |Vtd|2

(BK*) |Vts|2

• Updated branching ratio limits:

BR(B00) < 1.7 10-5

BR(B++) < 1.3 10-5

BR(B0) < 1.0 10-5

• Expect /K* ~ 1/50 and they look alike!

=

=

K*


• Current /K separation statistical -- we want event-by event

• Lower fake rates for rare modes ()

• Goal: 4 /K at p = 2.8 GeV/c with dE/dx (3.2 from RICH)

• Several photons per track in radiator materialtrk = / n

• Design goals of = 14 mrad

n = 12

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

eKp

Che

renk

ov A

ngle

(ra

d)

Momentum (GeV/c)

CLEO III RICH Detector

C = 12.8 mrad in LiF need trk = 4 mrad


CLEO III RICH

Proximity focussing

with solid radiators.

•LiF radiators

•N2 expansion gap

•CH2 /TEA photosensitive medium in MWPC

•Pad read-out

Photon Detector

LiF Radiator

Charged Particle

Cherenkov Photon

192 mm

CH +TEA

4

CaF Window2

Fibreglass Siderail

Reinforcing G10 Rod

Pure N

2

20 µm wires


First Colliding Beam Data

• Engineering run• Recorded ~ 80 pb-1 of data• Peak lum. ~ 5 1032 cm-2s-1

Nov.16, 1999Bhabha event


• After background subtraction:» 10.2flat radiators (stat. error only)» 13.2sawtooth radiators

• Expect 10-20% more photons with higher gain

CLEO RICH Performance

PlanarPlanar SawtoothSawtooth

Gain ~ 2 104


Conclusions

• bs penguins appear dominant» K » (’)K(*)

• Definitive observations of hadronic bu decays » » »

• First CP asymmetries consistent with zero»Based on ~ 9.7 fb-1 of data»Will be statistics limited for some time to come

• First exciting data from CLEOIII»RICH, Drift Chamber working very well.»Silicon installed in February.»Physics running begins April 3rd.


B

BD DD DK

K

A Fully-

Reconstructed

event

Sacha Kopp, Univ. Texas -- Austin


Continuum Suppression (cont’d)

B Mass (GeV/c2)

cos(T)»Fisher variable which utilizes

R2 = H2 / H0 Fox-Wolfram moment

cosB – angle between thrust axis and beam

Energy flow around thrust axis – 9 cones

»“Beam-constrained” mass of B:

MB = Ebeam - |pB|2

»Resonance masses (for , , K* modes)

2

• Maximum Likelihood fit utilizes 6 different variables:

»cosT -- angle between thrust axis of B and rest of the event

|cosT | < 0.8 removes 83% of continuum backgrounds

Off (4S) dataBB Monte Carlo

Sacha Kopp, Univ. Texas -- Austin 1 Search for CP in Rare B Decays Sacha E. Kopp, University of...

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