1 Chen Jiangchuan (for BES Collaboration) Institute of High Energy Physics, Beijing 100039, P.R. C....

transcript

Chen Jiangchuan(for BES Collaboration)

Institute of High Energy Physics, Beijing 100039, P.R. C.

The International Conference on QCD and Hadronic PhysicsJune 16—20, 2005

Recent Results on (3770) Resonance and D Mesons Production

& Decays from BES

D0 & D+ Meson Decays

(3770) production & decays

Outline

Summary

~18 pb-1 of data taken at 3.773 GeV

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

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

about 33 pb-1 of data collected around 3.773 GeV in total.

2004 Jan.5 BES completed total (3770) data collection.

BES (3770) data Sample

(3770) production & decays

(3770) resonance parameters

DD-bar cross cection at 3.773 GeV

Search for charmless decays of .. ,..)3770( *00* ccK KccKK

/)3770( JψEvidence for

Since its mass is above open charm-pair threshold and its width is two order of magnitude larger than that of , (3770) is thought to decay almost entirely to pure DD-bar.

(3770) is believed to be a mixture of and states of

system

131 D 1

)3686(

nb 8.16.11))3770((12

2)3770(

)3770( eeBFM

(3770) production cross section at peak

MeV 5.29.3769)3770( M 51012.1))3770(( eeBF Using mass and branching fraction (PDG02):

nb 0.50.5)( DDeeobs (Mark-III)

nb 7.01.7)( DDeeprd Non-saturate decay ?

About 39% of (3770) does not decay to DD-bar ?

Puzzle of (3770) production and decays

(1991)11 PLB267keV 160)( 13 gggD

Rosner) J.L. ,ph/0105327-(hep keV 620 )χ γΓ(ψ(3770) cJ

)155PRD41(1990 Kuang, Y.P. keV, 200) /)3770(( J

keV 980))3770(( DDnon

4.2%))3770(( DDnonBF Added all above numbers up !

There are some theoretical calculations about non-DD-bar decays

Theoretical predictionThere are some theoretical arguments about decays

Lipkin pointed out that could decay to non-DD-bar final states with a large branching fraction.

(3770)

(3770) resonance parameters

To understand this long-standing puzzle, (3770) and production cross section should be measured more precisely.

The cross section of (3770) can be obtained based onthe (3770) resonance parameters.

(3770) resonance parameters can be extracted froma fit to the observed hadonic cross sections in the energy range which cover (3770) resonance (-- scan experiment).

e+e-e+e-

e-e- -

e+ + +

e+e-e+e-

Events Recorded by BESII

Cosmic-ray and beam associated background

Distributions of the vertex of events

physics background could be estimated based on cross sections, luminosities and acceptances

)1( hadNhad

)3770(

GeV 78.3energy c.m. Nominal s

Monte Carlo productionhadronsee

The ISR (Initial State Radiation) return. The histogram show the hadronic eventproduction due to ISR when nominal center-of-mass energy at 3.78 GeV.

Monte Carlo productionhadronsee

Shadows are experimental data, lines are MC sample, (Ecm= 3.773 GeV).(Nch, KNO, Thrust, Sphericity, Aplanarity, xp, η, <pTin>, <pTout> distributions)

Hadron efficiency vs C.M. energy

[GeV] cmE

trgcmhadcm

obshad EEL

)( )()(

exp ))1(( ),( )( xssxfdxs Becthad

)(12)(

2222 sMMs

(Kuraev and Fadin)

functionsampling issxf ),(

had Observed cross section

12When scan over 3.770 G

Just before the scan experiment

Mass [MeV]

04.087.3096

05.030.3095

09.096.3685

01.090.3684

02.050.3684

BEPC energy calibration

3095.33684.8

MM3095.3)(EME

PDGJ/ψ

ψBEPCPDG02J/ψ

true '

EBEPC is the energy of BEPC set in the experiment,

Etrue is the true energy

01.070.3684

8.36842

9.36847.3684

(3770) productionTo get right resonance parameters, the two resonance productions and decays should be considered simultaneously. In this way the “correct” QED background ( ) can be determined correctly !

quarks) s and du, (from QED

)3770(

BES-II Preliminary !

[GeV] cmE [GeV] cmE

obshad

0.010.132.21Ruds

(preliminary !)

Experiment

MARK-I

MARK-II

BES-II

(MeV) Γ tot (eV) Γee

2.53769.9

0.31.03772.3

130224

(MeV) M

2.483.9

2.723.6

Comparison of (3770) Resonance Parameters

0.13.125.5 1.086.8

nb 0.0382..| MeV8.sprd

)( 007937723770

(MeV) )3770(M

Comparison of (2s) Resonance Parameters

experiment

This measurement

(preliminary !)

BES-II published

(PLB550(2002)24)

PDG2002

(MeV) M '(keV) '

(keV) 'ee

300063685 ... 3569269 020110252 ...

..AN 27264 21.044.2

09.096.3685 25300 15.019.2

Using a constant for vacuum polarization correction

Single tag analysis

Using kinematical fit method to improve momentum resolution and select the singly tagged D meson

1pb 3.17 L

Xfit MM Requiring

PDG02 Br

From Monte Carlo

DD-bar Cross Section at 3.773 GeV

NtagDobs

BES-II: of data @ 3.773 GeV

Single tag method

nb 0.260.082.56 obs

nb 0.500.126.14 obsDD

Observed cross sections for DD-bar production at 3.773 GeV

nb 0.310.093.58 00 obs

Near DD-bar production threshold region

π+tag

Using ‘double tag’ method, pioneered by MARK-III

1pb 3.17 L

DD-bar Cross Section at 3.773 GeV

BES-II: of data @ 3.773 GeV

Singly tagged D sample

Doubly tagged D

π+ π+

Double tag method

nb 0.190.333.50 00 obs

nb 0.190.332.49 obs

nb 0.380.475.99 obsDD

绝对测量

Preliminary !

)(12)(

2222 sMMs

0|))1((1|))1(( ),( )(

xsxssxfdxssM Bobs

Assuming that decay exclusively into (3770) DD

Radiative correction

PR D62 (2000)012002-1024.0047.1)1(|))1((1| 2

Initial State Radiation correction factorB

Obtained based on PDG02 (3770) resonance

parameters:

GeV 773.3At s

Radiative correction factor

Due to the uncertainties in resonance parameters and vaccum polarization )1( vp

GeV 773.3@ s

MeV2.53769.9M

MeV2.723.6" tot

eV 40260" ee

nb 0.370.103.29 tree

nb 0.740.157.88 treeDD

nb 0.450.124.60 00 tree

036.0779.0 Tree

12.002.029.1

treeDD

The contribution to R in the charm threshold region from the light quarks is estimated to be , which is obtained by fitting to the R values from 2.0 to 3.0 GeV measured by BES-II. The theoretical expectation is that is approximately independent of center of mass energy in this region.

14.026.2 udsR

yielding 18.002.055.3 R

The open square is charm counting method of R measurementAssuming that decays

exclusively into DD-bar

GeV) 3.773(at nb 709.6(GeV)

nb 8.8622

cmee E

Squares are the BES-II direct R measurements by counting inclusive hadronic events

(3770)

0.010.132.21Ruds which is obtained in measurement of (3770) resonance parameters

udsDDRRR udsDD

RRR or

4-prong with net charge zero0.85|cos|

(K) 0.001CL (K) π

01.0)4,P( 2 K

ππππ

22 ,4)P(χ)4,P( K

selection Ksatisfy 0S

Selection criteria

..00* ccKK S

.C.L 90%at @ 3.2)( * KKeeN

Data taken around (3770) peak

1pb 727 .Ldt

windowmass K0S

8.35.12)( 00* SKKeeN

0)( * KKeeN

Neutral mode Charged mode

Search for charmless decays of .. ,..)3770( *00* ccK KccKK

observed signalc.c. KK nt significaNo S* 00

observed signal No KK*

.C.L 90% @ 3.2)( * KKeeN

Data taken off-resonance (@ 3.65 GeV)

7.100*

SKKQEDN

Normalized to the luminosity and phase space of ψ(3770) production

1pb 4.6 Ldt

.C.L 90% @ 3.9)( 00* SKKeeN

Check if there are continuum

production ?

process photon one onannihilati process continuumphoton one

hadrons hadrons

Resonance productions and decays QED process

Observed in experiment

ga amplitude a amplitude QEDa amplitude

Charmless final states observed

2||)hadrons charmless( QEDgobserved aaaeeN

hadrons

|a|~|a| and |a||a| gQEDg around 3.77 GeV

Three gluon annihilation process

A detailed maximum likelihood analysis based on above observed event numbers gives

69592 .

230.246.1

00* ||86.1))3770(( gS aKKN

2490300

00 4390 |a|.)KKee(N QED..QEDS

o.cos 1809990

16162 . χ 0 |a| set g

giving a significance of 2.4

Those yield the branching fraction and upper limit to be

pb 4.0)6.04.18()( GeV 3.773

00* KKeeobs

L. C. 90%at 102.1))3770(( 3-00* KKBF

keV 3.3)1.10( 7.120.8)3770(

C.L. 90% @ keV 2900*)3770(

4-5.44.3

00* 101.3)3.4())3770(( KKBF

and partial width to be

(preliminary !)

Evidence for Decay

it is an interesting question if transitions inside the charmonium system exist.

/Jψ ''

Examine the recoil mass of

Projecting the events on to the vertical scale (recoil mass of

), the evidence for is observed

llECMll

5 . 2| |

MeV150| | / JllMM

22 ||)(

PEEM cmREC

(mainly)

/)3770( J

Due to ISR

Evidence for (cont’d)

/Jψ ''

/ return ISR ' Jψ

/)3770( J

/' Jand

Data MC

9.55.25 /J MeV3.03103.3M1

signal events

Analysis of the recoil mass

3.11.11 9.55.25

out of

events in total

20 times large than the data

/Jψ ''

analysis of the fitted dilepton masses ofOpen histogram is for e+e- channel,

histogram in yellow is for mu+mu- channelISR todue production '

mainly

The histogram is psi(3686), while error bars are the psi(3686) + psi(3770)

/Jψ ''

8.48.17 signal events obtained 8.00.6

8.48.17

/)3686( Jψ

/)3686( Jψ out of/J

signal events/J8.48.11)/)3770(( JN

data MC

20 times large than the data

It has been quoted 21 times.

(3770)

(3770)It is an interesting question if transitions inside the charmonium system exist.

It is very important in elucidating the exact nature of the (3770) and help us understand why the (3770) does not seem to be saturated by DD-bar decays.

Before BES-II one knows the decays

BES-II established the transition at level ! σ3

Paper published in PLB605 (2005)63

Comments by Referees of the paper

keV )()J)(( 2333803770

)%...()J)((BF 0901403403770

D0 & D+ Meson Decays

Exclusive Semileptonic D DecaysExclusive Semileptonic D Decays

Purely Leptonic DPurely Leptonic D+ + DecayDecay

D absolute hadronic decay branching fractions

Singl tag samples

(3770) is a good laboratory for study D meson decays

34Invariant mass distribution for tags0

DInvariant mass distribution for tagsD

19875840 tagD

N 1495321tagD

KKD S0

00 SKD

0 KD KD

Singly tagged D samples

Semileptonic D DecaysSemileptonic D Decays

π+π+

Branching fractions for eKD0 eD0and

To measure the standard model parameters Vcs, Vcd

Probing the hadronic current

Understand the dynamics of semileptonic decays

GilXMA

qqqQ ''

vluL )1( 5

))(()( '22 ppqfqH

Where is a vector form factor, and are the four momenta of the initial and final mesons, respectively, and is the squared mass of the virtual W.

)(qf 2 p 'p

2 2 21 2

* : , ,

lD Kl f q m f q

D K l A q A q V q

As an example

11122 100531 s|)(f||V|.)KeD( K

cse11122 100013

s|)(f||V|.)eD( cde

(“nearest pole dominance”)

Motivation

Branching fraction for

To test if the Isospin conservation is still held in D semileptonic decays. Isospin conservation requires

2.04.1)(/)(00

ee eKDeKD

From PDG Br

1)(/)(00

ee eKDeKD

It is called “Longstanding puzzel” in Charm decay !

eKD0 )(

Longstanding Puzzle in charm decay

Is isospin conservation held in the D semileptonic decays?

Motivation

tags.)D of RECin (found 0

eeK ) tags D of REC. in (found eK -

Distribution of the Inv. masses of

Combinations for the events in which the

are observed in the recoil side

eeKD 0

REC.)in (found ee

Distribution of the momentum of the electronfrom the events of eeKD 0

Experiment

MARK III

PDG 04

)( 0eeKDBr

27.040.082.3

)( 0eeDBr )(

0eeKDBr

03.013.033.0

4.05.04.3

18.058.3

04.039.0 23.011.0

06.036.0 9076 ..

7.00.6 2.23.1

670591958 ...

Results

[%] [%] [%]

Phy. Let. B597(2004)39-46 Phy. Let. B608(2005)24-30

11.078.0

|)0(| Kf |)0(| f

11.065.0

00.007.0)3(71.0

01.000.0)6(57.0

03.004.078.0

00.007.0)5(64.0

01.000.0)4(66.0

06.014.073.0

LQCD(1)

LQCD(2)

|)0(/)0(| Kff 07.019.093.0

Phys.Rev.D66,114002,2000

Nucl.Phys.Prog.Suppl.83,286,2000

Nucl.Phys.B619,565,2001

111220 10|)0(|||53.1)(

sfVeKD Kcs

111220 10|)0(|||01.3)(

sfVeD cd

Theoretical predictions are in the range from 0.7 to 1.4. See J.D. Richman et al., Rev. Mod. Phys., Vol. 67, No 4, 1995

Different theoretical predictions

Form factors

| |VV cdcs ||PDG04

inserting

Average MARK-III and CLEO gives

06013006011 ....

030060290 ...

030040050260 .

BES(QCDSR)

BES(LQCD(1)

BES(LQCD(2)

|| csV || cdV

15005001 ...

090080060181 ....

050050250 ...

BES MARK III

2|/| cscd VV 003.0017.0043.0 005.0057.0 038.0017.0

100 |)(f/)(f| K

CKM matrix elements Input theoretical predictions for the form factors

)0( )0( ff K

BES MARK III PDG04

62.044.1 2.04.1

Ratio of partial width

Obtained based on the branching fractions quoted from PDG02

070220081 ...

Solve the longstanding puzzle in Charm decays !

BES-II results support isospin conservation is held in the D semileptonic decays!

Purely Leptonic DPurely Leptonic D+ + DecayDecay

Phy. Let. B610(2005)183-191

Motivation

|V|GνlD(

Lattice gauge, potential models bag model, QCD sum rule …, calculation predict the value of

The fD measurement will allow comparison with the theoretical calculation to improve the theory. Lattice predicts fB/fD with small errors. Precision measurement of fD precision estimate of fB and precision determination of Vtd

Df Bf00 BB Mixing experiment

It is very difficult to measure the fD due to |Vcd| is small D

DThe effect of strong interaction can be parameterized by

)%08.0()( 17.005.0

MeV)300( 8018040150Df

MARK-III set an upper limit of fD < 290 MeV

BES-I observed 1 event for and measured

Physics Letters B 429(1998) 188-194

Previous measurements

GeV 03.4@ S

missmissmiss PEU Neutrino carries energy and momentum away

Should be around zero

1495321tagD

Fully reconstruct one D

Require one additional charged track and no additional photons

0 KD DVS

Monte Carlo sample 150 times more than data

3 events in the signal region

Monte Carlo simulation

missU 3

Estimation of background

The main background are 000 K , ,KD

)background continuum possible theas wellas

, ντ,πK,ππD as(such

modes)decay all ( 00

DorDDD ee -

3 X 100 times more Monte Carlo samples for each of the modes Nb = 0.22

Analysis of 320 pb-1 Monte Carlo samp

le Nb = 0.33+/-0.11

13 events in the tagged D- mass region

Method 1

Method 2

Method 3

1 hadronic track in the recoil of the tags

Nb=0.31±0.09

1 muon is fund in the recoil of the tags, and the events satisfied the requirements for selection of

Search for the decay

Singly tagged D-

Candidate

%,)010.0122.0()( 111.0053.0

2.67±1.74 Events D

νlDBr

|| cdV

MeV )25371( 129119 D

Double-tag

They are two very important constants to normalize all other branching fractions for the D mesons decays, B mesons and Z0 decays.

They enter into CKM matrix elements determinations. So more precisely measuring the both branching fractions can directly improve the CKM matrix elements:

|| csV

|| cdV

|| cbV

determine from

)( 0 eKDB

determine from

)( 0 eDB

lDBB )( 0 lDBBand

Methods of measuring )( 0 πKDB and

• at (3770) ---

• B decay

)( πKDB

DD double tag analysis

Absolute branching fractions for

(preliminary !)

SUMMARYBES measured (3770) resonance parameters

nb 0.030.829.07 prd)( 3770

BES measured the DD-bar Cross Section at 3.773 GeV to be

Experiment

BES-II

)3770(M (MeV) Γ tot (eV) Γee

2.53769.9

0.31.03772.3

130224

(MeV) M

2.723.6

0.13.125.5 1.086.8 (preliminary !)

2.483.9

( ISR based on PDG02 )

nb 0.740.157.88 treeDD

nb 0.760.158.14 treeDD

( ISR based on BES-II parameters )

(preliminary !)

(3770)

0.010.132.21Ruds From 3.66 to 3.87 GeV

BES observed the charmless decay events of

measured the partial width of

BES observed hadronic transition of to and measured the partial width to be

(3770) /J

keV )213280()/( '' J

keV 3.3)1.10( 7.120.8)3770(

..,..)3770( *00* ccK KccKK

C.L. 90% @ keV 2900*)3770(

and set its upper limit to be

(preliminary !)

SUMMARY

SUMMARYMeasured the form factors & ratio of partial widths

06.014.073.0|)0(f|

07.022.008.1)Γ(/)Γ(00

ee eKDeKD

Observed 3 D+ purely leptonic decay events, and obtained

MeV 25)(371 129119 D

. πππ, Kππ KKD 00 ,

00000 K,K,K,K,KD

03.004.078.0|)0(f| K 07.019.093.0

f Theory: from

0.7 to 1.4

Solve the longstanding puzzle in Charm decays

Measured absolute hadronic branching fractions for

Those would improve the normalization constants used in Charm and B physics !

谢谢！

Thank You ！

Comparing the BES Results with that from CELO-c

Near DD-bar Threshold Experiments

LP03 关于 J/ 的讨论

?ee→ 2S2S→ J

Ecm -Mass recoiling

3770→ J

mainly

BES-II

CLEO-c

BES-II 结果成为热门话题，被广泛关注，讨论和引用！这是 BES-II 与 CLEO-c 的物理结果第一次被 CLEO 成员所做的对比。 (at LP03)

DAPHNE’04 06/08/04 Hanna Mahlke-Krueger, Cornell (RG mdfy)

ee→ 2S2S→ J ?

232 events

Ecm -Mass recoiling

• 5.2±0.2 pb-1, (4.5±0.4)104 ’’decays

• efficiency: 37% < 4.75 events @ 90%CL B

R3770J(1S)) <0.26% @ 90% CL

17.8±4.8 events incl 6.0±0.8 bgd (0 from cont) BR3770→J)

= (0.34±0.14±0.08) % = (80 ±32±21) keV

BESII CLEO-c

T. Skwarnicki, QWG03

ee→ 2S2S→ J

M(ℓ+ℓ) GeV

hep-ex/0307028

已 21次被引用

DAPHNE’04 06/08/04 Hanna Mahlke-Krueger, Cornell

ee→ 2S2S→ J ?

232 events

Ecm -Mass recoiling

• 5.2±0.2 pb-1, (4.5±0.4)104 ’’decays

• efficiency: 37% < 4.75 events @ 90%CL BR

3770J(1S)) <0.26% @ 90% CL

• 28 pb-1 (3.783-3.885GeV), 1.85105 ’’decays

• efficiency: 16% 17.8±4.8 events incl 6.0±

0.8 bgd (0 from cont) BR3770→J)

= (0.34±0.14±0.08) % = (80 ±32±21) keV

BESII CLEO-c

T. Skwarnicki, QWG03

ee→ 2S2S→ J

M(ℓ+ℓ) GeVhep-ex/0307028

Results given at international conference from BES-II & CLEO-c

Moriond EW04 (2004 年 3 月 )

APS (2004 年 5 月 )

nb 0.370.124.18 00 tree

nb 0.340.093.23 tree

nb 0.670.157.41 treeDD

nb 0.250.093.26 00 obs

DD nb 0.210.143.43 00 obs

nb 0.240.072.52 obs

DD nb 0.160.152.44

nb 0.450.115.78 obsDD

nb 0.360.205.87 obsDD

无报道MeV )(365 32121

28-113-D

f MeV 10)42(230 Df

18.003.048.3 R

这是 BES-II 的物理结果与 CLEO-c 的第二次对比。

2 个月之后

Results given at international conference from BES-II & CLEO-c

BES -- Moriond EW04 (March, 2004)

CLEO-c -- APS (May, 2004) 00

无报道keV 21)32(80 )/)3770(( J

Dalitz analysis of N./A.

Branching fractions

CLEO-c 原计划要在 Moriond’04 国际会议上正式报道物理结果。但最后却什么也没讲。

Rosner 主要根据 BES Moriond’04 结果 , 提出 rescattering 模型 , 来解释衰变 . 他在文章中先后 5 次引用 BES 结果 .

DDnon )3770(

0.0030.0210.052 |/| cscd VV

08.021.004.1)(

0.080.201.01 /)0( Kff

0.020.040.74 )0( Kf

0.060.140.77 )0( f

nb 0.310.093.58 00 obs

nb 0.260.082.56 obs

nb 0.500.126.14 obsDD

BES-II DD-bar Cross section in good agreement with CLE-c

与 CLEO-c 物理结果的对比及国际反响

在 1.3% 的范围内一致！

69070220081 ...

BES-II Final result

Heavy Quarkonia

8 类典型的热点问题 3 大不解之迷 ? 有 2 个主要起源于 BES的近期研究工作！

QQ-bar 的热点问题和不解之迷？国际反响

(3770)

几乎是常数效率，早年的辐射修正， …

MARK-I, DELCO, MARK-II 平滑效率； ( 相对 scale)

BES-II 效率曲线

依赖于 ) measured(Only DD B

目前 PDG 采用 MARK-III 的 nb 3.06.02.4 D

依赖于 )( 0 πKDBF

πKDBF

πKDBF CLEO measured

绝对测量

πDD 0*

软标记π

实验状况

It is important to accurately measure the cross sections for DD-bar production !

)( 0 πKDBF )( πKDBF

CKM matrix elements &|| csV || cdV

Form factors & |)0(| f

Branching fractions

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

)]0([ )0( ff K

Motivation

Isospin conservation implies

)(/)(0

eeeKDeKD

2.04.1)(/)(00

ee eKDeKD longstanding puzzle in Charm decays !

From PDG Br

|)0(| Kf

1)(/)(00

ee eKDeKD

eKDeeKD 00 , ,

1 Chen Jiangchuan (for BES Collaboration) Institute of High Energy Physics, Beijing 100039, P.R. C....

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