Recent results on non-DDbar decays of (3770) at BES

HaiLong Ma [For BES Collaboration]

The IVIIth Rencontres de Moriond session devoted to QCD AND HIGH EN

ERGY HADRONIC INTERACTIONS (La Thuile, Italy)

Mar.17-24 2007

R values

Outline

Summary

BF[(3770) → D0D0,D+D-,DD and non-DD]

Introduction

Parameters of (2S) and (3770)

Search for charmless decays of (3770)

Introduction

evaluation of the electromagnetic coupling at the Z mass scale, .

)( ZQED M

determination of of the muon. 2/)2( ga

evaluation of )(sS

understanding of (3770) non-DD decays and others……

R(s) values are important for vacuum polarization correction, which plays an important role in the precision test of the Standard Model;

R is one of the most fundamental quantities in particle physics, which counts directly the charges, the flavors and the colors of quarks involved.

Introduction

Long-standing puzzle of (3770) production and decays

(3770) is thought to decay almost entirely to pure DDbar, but there is large discrepancy between and )3770( DD

nb 8.16.11))3770((12

2)3770(

)3770( eeBFM

prd

nb 0.50.5)( DDeeobs (Mark-III)nb 7.01.7)( DDeeprd

before BES-II & CLEO-c

Cross section at peak (PDG04 parameters)

Simultaneously measusing both and )3770(DD

Precisely measuring the energy dependent cross sections for both inclusive hadrons and DDbar events production simutanmeously, directly measure and00[ (3770) , , ]BF D D D D DD [ (3770) ]BF non DD

Search for some exclusive non-DDbar decays

BES made several fine cross section scans covering both the (3686) and (3770) to measure the resonance parameters, branching fractions and search for non-DD decays …

BESII (3770) data sample of about 33 pb-1

~17.3 pb-1 data taken at 3.773 GeV

~7 pb-1 data taken at the region from 3.768 GeV to 3.778 GeV during Mar. 2003

~8 pb-1 data taken in the energy region from 3.665 to 3.878 GeV during Dec. 2003

0

50

100

150

200

250

300

MARK-I DELCO MARK-II MARK-III BES-II CLEO-c

~6.5 pb-1 of data collected at 3.650 GeV

~1.0 pb-1 of data collected at 3.665 GeV

ECM [GeV]

σobshad(nb) σ0

had(nb) R

3.650

3.6648

3.773

18.983 0.087 0.182

18.299 0.199 0.176

27.680 0.056 0.266

14.578 0.067 0.141 0.588

14.128 0.158 0.139 0.580

22.855 0.046 0.220 1.144

2.236 0.010 0.022 0.089

2.185 0.024 0.022 0.087

3.746 0.008 0.036 0.187

WA| 2.218 0.019 0.089udsR

(3686) (3770)fit to &| 2.262 0.054 0.109uds σR

Obtaining by fitting to the R values measured by BES in the range from 2.0 to 3.0 GeV

14.026.2| GeV 3.0 to 2.0 udsR

PLB641(2006)145

Measurements of the R values at 3.650, 3.6648 and 3.773 GeV

Measurements of Rhad, Ruds(c) and Ruds(c)+(3770)in the range from 3.650 to 3.872 GeV

efficiency

ISR factor

PRL 97(2006)262001

Dec. 2003 data set

Sources ΔSYS (%)

Luminosity 2.1

Hadron selection 2.5

M.C. modeling 2.0

ISR 1.5

Ψ(3770) resonance parameters 2.7

Total (off Ψ(3770) region)

4.0

Total(within Ψ(3770) region) 4.9

Table. Systematic uncertainties in the determination of R values

Radiative correction factor B

obs

g

Born

obsDD

Born

BornDDDD

σgN

NDDBF

)3770(IIBES)3770(prd

(3770)

prd

))3770((

BES II 0.770 0.014g

Some systematic uncertainties can be canceled out

Radiative correction factor obtained based on new (3770) resonance parameters measured by BES-II, hep/0605107.

BF[(3770) → D0D0,D+D-,DD and non-DD]

( (3770) ) (35.7 1.1 3.4)%BF D D

0 0( (3770) ) (49.9 1.3 3.8)%BF D D

( (3770) ) (85.5 1.7 5.8)%BF DD ( (3770) ) (14.5 1.7 5.8)%BF non DD PLB641(2006)1

45

nb 0.500.126.14 obsDD

2 BrL

NtagDobs

DD

Single tag method

PLB 603(2004)130

(3770) 9.323 0.253 0 801 nbBorn .

Determination of

with the measured R values at 3.650, 3.6648 and 3.773 GeV

Line shape of the cross sections for hadron and DD-bar production

Branching fractions

Simultaneously.fitting to the inclusive hadron and the DD-bar production cross sections

00DD

DD

Inclusive hadrons

Inclusive hadrons

Inclusive hadrons

PRL97(2006)121801

Mar. 2003 data set

)%2.43.74.16())3770((

)%2.43.76.83())3770((

)%8.27.39.36())3770((

)%3.27.47.46())3770((00

DDnonBF

DDBF

DDBF

DDBF

Comparison of (3770) Resonance Parameters

nb 0.3566.063.9|MeV 3.3772)3770(

s

prd

109.0054.0262.2uds R

nb 0.2848.094.6|MeV 3.3772

obs)3770(

s

Mar. 2003 data set

)3770(M)2()3770( SMMM

tot)3770(

ee)3770(

PRL 97 (2006) 121801

Comparison of (3686) Resonance Parameters

Experiment

This measurement

BES-II published

(PLB550(2002)24)

PDG2006

(MeV) M '(keV) '

tot

(keV) 'ee

3685.5 0.0 0.3 331 58 2 2.330 0.036 0.110

..AN 27264 21.044.2

034.0093.3686 337 13 2.48 0.06

The measured partial width is consistent with PDG06 partial width of (3686).

)%018.0735.0(])3686([ eeB PDG06

)%033.0122.0704.0(])3686([ eeB PRL97(2006)121801

Mar. 2003 data set

Precision measurements of the mass, total and leptonic widths of (3770) with the measured R values in

the range from 3.650 to 3.872 GeV

Preliminary! hep-ex/0612056

Dec. 2003 data set

13 D1

Par

tial

wid

th

084.0023.0121.2Ruds

Leptonic branching fraction

510 ]))3770([( eeB

PRL97(2006)121801

PRL97(2006)121801

Preliminary! hep-ex/0612056

(0.98+/-0.06)

PRD21(1980)2716

Observed Cross Sections

No obvious cross section discrepancy at the two energy points is observed. However, to extract the non-DD-bar branching fractions of (3770) decays, one needs to consider the interference between the two amplitudes of the continuum and the resonances, and to consider the difference of ISR & vacuum polarization corrections at two energy points.

Search for charmless decays of (3770) International Journal of Modern Physics A, Vol 21 No. 27 (2006) 5416

Preliminary

BES measured R values at the three energy points and in the energy region between 3.650 and 3.872 GeV

SummarySummary

BES firstly measured the branching frations for non-DDbar decays of (3770) using two different data sample and two different methods

BES more precisely measured the parameters of the (2S) and (3770) resonances

Thank You ！

BES searched for charmless decays of (3770)