Recent results on D meson decays from BES

陈江川 (for BES Collaboration)

Institute of High Energy Physics, Beijing China

高能物理学会第七届全国会员代表大会暨学术年会 广西 桂林

2006 年 10 月 27 日 -11 月 1 日

Outline Introduction

Semileptonic decays of D mesons

Summary

Inclusive decays of D mesons

The Beijing Electron Positron Collider (BEPC)

L ~ 11031 /cm2s at (3770) peak Ecm~2-5 GeV

BESII Detector

VC: xy = 100 m TOF: T = 180 ps counter: r= 3 cm MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.5 % = 7.9 mr B field: 0.4 T p/p=1.7%(1+p2) z = 3.1 cm

Muon identification can be done by the Muon Counter for the charged track with momentum of great than 0.55 GeV/c

dE/dx

TOF

(3770) data sample

~18 pb-1 data taken at 3.773 GeV

~7 pb-1 data taken at the region from 3.768 GeV to 3.778 GeV

~8 pb-1 data taken in the energy region from 3.665 to 3.878 GeV

The total Luminosity is about 33 pb-1.

Near DD-bar production threshold region

π–

With the singly tagged D sample, we can do some absolute measurements

e+

e-

D

D

K+

π–tag

D+

D-

X

π–

e-e+

D

D

K+

tag

0X

Singly tagged D sample

Absolute Measurements

0D

0D

Semileptonic D Decays (1)Semileptonic D Decays (1)

e+

e-

Dtag

D+

D-

0K

π-K+

π-

e+

e-

Dtag

D0

K

π-0D

K+

D D

0

0

KD

,KD

Motivation

Isospin conservation requires

2041)()/(00 ..eKDeKD ee

From PDG Br

1)()( 0 ll KlD/KlD

It is called “Longstanding puzzle” in Charm decay !

Is isospin conservation held in the D semileptonic dec

ays?

Recently:

070220081)(

)(0

0

...eKD

eKD

e

e

040050001)(

)(0

0

...eKD

eKD

e

e

BES-II published on Phys. Let. B608(2005)24-30

CLEO-c contributed paper at LP05 reports:

Solved the puzzle in Charm decays !

CKM matrix elements &|| csV || cdV

Form factors & |)0(| f

Branching fractions

*

*

*

0Dc

u)(d

)( D

s ][d

u)(d

K ][

)( 0K][ || ||VV cdcs

)]0([ )0( ff K

Motivation

)()(00

KD/KD

5021)()(00 ..KD/KD

From PDG04 Br

|)0(| Kf

0

0

KD

, ,KD

Charged track

photon

0 from , SK 22 yx < 0.08 m & |z| < 0.2 m

BSCE > 0.1 GeV 5firstHit22 ch

37 DC

85.0|cos|

Good track selection

Charged track with good helix fit

To be consistent with originating from the primary events vertex Vxy <0.02 m & |z| < 0.2 m

Singly tagged modes KD0 , 0 K , K , 0

SK KD , 0K , KK 0 , KK ,

00 K, 0K

PID made by combining TOF, dE/dx & BSC information

CL > 0.1% ;

: K > CL K : CL

prob (2 , n ) > 0.1%, n = 1, 2, 3

Singly tagged D sample

1C kinematic fit

(mKnπ)

0 K,

, K ,

(Throughout the talk, charge conjugation is implied.)

Invariant mass distribution for tags0D Invariant mass distribution for tagsD

34119875840 tagD

N 1601495321 tagD

N

,)(,)(

,)(,)(0000

00

KDdKDc

KDbKDa

S

KD0

00 KD

KD0

00

SKD

D)i(

KD)h( ,KD)g(

KD)f( ,KD)e(

,KKD)d( ,KKD)c(

,KD)b( ,KD)a(

SS

S

S

00

000

0

0

KD 0SKD

KKD S0

KKD

0SKD00 SKD

0 K K

D

9 modes

Candidate modes KD0,

π:

CLKCL K :

;

0KD

μ :

missU selection

Double-tagged D decays (1)

80.

KCLCLeCL

CL

e

+

e-

D

D

tag

D+

D-

0K

π-K+

π-

Missing energy and momentum

missmissmiss PEU Should be around zero

missUmiss |U| 2

Nγ=0 (on recoil side of the D tag)

(or Nhit > 2 on μ counter)

Combined TOF , dE/dx & BSC information

80.

KCLCLeCL

CL

νKD 0

data

Bckgrd DD-bar

MC

Data (subtracted bck)

tags.)D of RECin (found 0

K ) tagsD of REC.in (found -0 K

Distribution of the Inv. masses of combinations

for the events for which the and

are observed in the recoil side

mKn

,K 0K

tags)D of REC.in (found 0

Preliminary

Branching fraction

Experiment

BES

MARKIII

E687(93)

E687(95)

PDG 04

)( 0 KDBF

59.056.055.3

)( 0 DBF )(

0 KDBF

10.030.038.0

500490123 ...

170193 .. 030207 ...

8032310 ...

Results

[%] [%] [%]

130130243 ...

21030207 ....

An up limit at 90% C.Lis set to be <0.89%

Preliminary

hep-ex/0610019 & 0610020

BES MARK III PDG04

)(

)(0

0

KD

KD15.024.087.0 5021 .. 5021 ..

Ratio of partial width

Obtained based on the branching fractions quoted from PDG04

Preliminary

The ratio of Br. for D0 decays to K(π)μν is:

03.009.011.0)(

)(0

0

KDBr

DBr

Semileptonic D Decays (2)Semileptonic D Decays (2)

e+

e-

Dtag

D+

D-

0*Ke

e

π-K+

π-

e+

e-

Dtag

D0

*Ke

e

π-0D

K+

D D

e*

e

e*

e

eK ,eKD

eK ,eKD

0

00

Candidate modes

π: CLKCL K :

e :

missU selection

Combined TOF and dE/dx information

80

0010

.KCLCLeCL

eCL

and .eCL

e+

e-

D

D

tag

D+

D-

0*Ke

π-K+

π-

Missing energy and momentum

missmissmiss PEU Should be around zero

missUmiss |U| 3

0010.CL

e*

e

e*

e

eK ,eKD

eK ,eKD

0

00

Double-tagged D decays (2)

Combined TOF , dE/dx & BSC information

2200 c/MeV |MM|SK

KS0:

νe

eeKD

eeKD 00

eeKD 0*

eeKD *0

Events found in REC. of Dtag

Results:Published in Eur. Phys. J. C47 (2006) 31

Results:

With the measured branching fractions in this work and

quoted from BES-II earlier work, we obtain:

%...eKDBF

%...eKDBF

e

e

270400823)(

670591958)(0

0

Published in Eur. Phys. J. C47 (2006) 31

Comparison

)(

)(

l

l*

lKD

lKD

uncertainty of theoretical

prediction

Inclusive Decay Branching Fractionsfor

XK/K ,XK/KD 0** 0

e+

e-

Dtag

D+

D-

0*K

π-K+

π-

e+

e-

Dtag

D0

*K

π-0D

K+

D D

X X=any particles

K–

π+π –

0K

Motivation

Serving as a check on the sum of the branching fractions for the exclusive D decay.

Providing information about the relative strength of Cabibbo-favored and Cabibbo suppressed D decays.

Candidate modes

π: 0.001KCL& CLKCL K :

Combined TOF and dE/dx information

0010.CL

XK/KD ,XK/KD

XK/KXK/K ,XK/KXK/KD

XK/KXK/K ,XK/KXK/KD****

****

00000

0000

00000

Double-tagged D decays

cmLxycm. &|MM|SKS

MK8703

00 KS0:

e+

e-

Dtag

D+

D-

0*K

π-K+

π-

D

X=any particles

K–

π+

e+ D0

*K

0D

D

Xπ –

e-

0K

The Kπ with maximum CL(K)•CL(π) retained in an event

D0 signal region

D0 sideband

K +π –

K –π+K+π –

XKXKD * 0XKXKD * 0

XKXKD * 00

Cabibbo favored decay Cabibbo suppressed decay

XKXKD * 00

K –π+ K+π –

D – signal region

D – sideband

Results

%...XKDBF * 210478)( 00

Cabibbo favored decay:

%...XKDBF * )035423(2)( 0

Cabibbo suppressed decay:

%...XKDBF * 402182)( 00

C.L. 90%at 66)( 0 %.XKDBF *

%..XK

XKsum*

*

02123)BF(D

% 0.88.1)BF(D :PDG04 BF exclusive of 0

00

Published in PLB625 (2005) 196

)20(1.5)(or 921.0-

0 %.XKDBF .*

Neutral K decay of D: Charged K* Decay of D: XK/KD **

e+

e-

Dtag

D0

*K

0D

K+

D

X

0K

π –

π+π –

KS0

Removing double counting with sideband background.

XK/KD 00

3σ

D0 signal region

D0 sideband

XK/KD 000

XK/KD 00

D+ signal region

D+ sideband

π+π –

π+π –

Preliminary

X K D

*

0 X K D*

D0 signal region

D0 sideband

X K D*

0

X K D*

K S

0π –K

S0π –

K S

0π + K S

0π +

Preliminary

Mass(GeV/c2)

Mass(GeV/c2)

Mass(GeV/c2)

Mass(GeV/c2)

D – signal region

D – sideband

Results

% 0.38.46.47)/( 000 XKKDBF

% 3.35.55.60)/( 00 XKKDBF

% 9.13.83.15)( *0 XKDBF

% )7.02.57.5()( * XKDBF

%6.3)( *0 XKDBF

% 3.20)( * XKDBF

Cabibbo favored decay:

Cabibbo suppressed decay (at 90% C.L.):

The results submitted to PLB

Comparison

BES measured semileptonic D decay branching fractions

.

.

% 8.03.23.10)(

% 10.030.038.0)(

% 59.056.055.3)(

0

0

0

KDBF

DBF

KDBF

03.009.011.0)(

)(0

0

KDBr

DBr

The ratio of branching fractions is

Summary

Ratio of partial width BES MARK III PDG04

)(

)(0

0

KD

KD15.024.087.0 5021 .. 5021 ..

.

Preliminary

hep-ex/0610019 & 0610020

Summary

.

Measured semileptonic D decay branching fractions

% )27.075.050.3()( eeKDBF

% 28.004.161.2)( 00 eeKDBF

% 40.021.106.5)( 0* eeKDBF

% 39.048.187.2)( *0 eeKDBF

With the measured branching fractions in this work and quoted from BES-II earlier work, we obtain:

%...eKDBF%...eKDBF ee 270400823)( , 670591958)( 00 .

02.017.057.0)(

)(0

0*

e

e

eKD

eKD

Published in Eur. Phys. J. C47 (2006) 31

Summary

.

Measured branching fractions for inclusive Cabibbo favored and suppressed decays of D mesons:

%...XKDBF * )210478()( 00 Cabibbo favored decay:

%...XKDBF * )0354223()( 0

Cabibbo suppressed decay:

%...XKDBF * )402182()( 00

C.L. 90%at 66)( 0 %.XKDBF *

)%..()XKBF(D

0.8)%(8.1)XKBF(D :(PDG04) BF exclusive of sum*

*0

021230

0

Published in PLB 625(2005)196

)20(1.5)(or 921.0-

0 %.XKDBF .*

SummaryCabibbo favored decay:

Cabibbo suppressed decay (at 90% C.L.):

%)0.38.46.47()/( 000 XKKDBF

%XKKDBF )3.35.55.60()/( 00

Branching fractions of inclusive neutral K decay of D .

.

.

% )9.13.83.15()( *0 XKDBF

)%7.02.57.5()( * XKDBF

%6.3)( *0 XKDBF

%3.20)( * XKDBF

The results submitted to PLB

谢 谢！

Thank You ！