Recent Results on (3770) Physics at BES

Ming-gang Zhao

(For BES Collaboration)

The 44th Rencontres de Moriond, QCD and High Energy Interactions

March 14-21, 2009, La Thuile, Italy

Introduction

Summary

Measurements about (3770)non-DD

Outline

Anomalous line-shape of e+e-hadrons in energy region from 3.65 to 3.87 GeV

Measurement of D+D-(s)/D0D0(s)

Introduction

• Only exist one resonance: (3770)

• Long standing (3770) decay puzzle

•

Knowledge about 3.70~3.87 GeV region [before BES-II and CLEO-c results]

• Theory prediction: nearly 100% DD decay

Experiment measurement: unsaturation (nearly 40%) of (3770) production and decay

Introduction

about 17.3 pb-1 data taken at 3.773 GeV about 7 pb-1 data taken from 3.768 GeV to 3.778 GeV

0

100

200

300

400

500

600

700

800

900

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

[pb-1]

World (3770) Samples

about 8 pb-1 data taken from 3.665 to 3.878 GeV

about 1 pb-1 data taken at 3.665 GeV

BESII (3770) data sample

Data Samples

about 6.5 pb-1 data taken at 3.650 GeV

Several different methods and data samples ， and systematical studies on B[(3770)→non-DD]. All first time measurements.

Measurements about (3770) non-DD

PDG 2008

PRD76, 122002 PLB659, 74PRL97, 121801PLB641, 145

Anomalous line-shape

high-energy sidelow-energy side

One simple (3770) resonance hypothesis is quite questionable to fit the current data.

initial state radiation

DD production threshold

the energy dependence of the D D scattering amplitudes due to the Blatt-Weisskopt barrier

high energy slope steep than low energy slope

low energy slope steep than high energy slope

Two data sets taken in March and December

2003

Anomalous line-shape

Solution 1: two amplitudes, no interference

Solution 2: two amplitudes, complete interference

Comparison: one (3770) amplitude hypothesis

Solution 3: (3770) amplitude + G(3900), interference

)(Eσ)(Eσ)(Eσ)(Eσ)(Eσ cmCTMhadcm

expψ(3686)cm

expJ/ψcm

expRs(3770)cm

exphad

2cm2

2cm1cm

expRs(3770) )(EA)(EA)(Eσ

2cm2cm1cm

expRs(3770) )(EA)(EA)(Eσ ie

The expected cross section for e ＋ e － hadrons:

Rs(3770) means the full structure around 3.773 GeV, we use one or two pure P wave Breit-Wigner amplitude(s) with energy dependent to express

Babar PRD76 (2007) 111105(R); Belle PRD77 (2008) 011103(R)

PRL101 (2008) 102004

])M(EiΓ)M(E

Γ12π)(E[A

jcmtotj

2j

2cm

hadj

eej

cmj

Anomalous line-shape

Solution 1: two amplitudes, no interference

Circles with error bars in black are the observed cross section;

Red line: fitted values of cross section;

Green line: the fit with one (3770) hypothesis;

Circles with error bars in red are the measured net cross sections after subtracting J/and continuum contribution.

The blue line shows the fits

PRL101 (2008) 102004

Anomalous line-shape

Circles with error bars in black are the observed cross section;

Red line: fitted values of cross section;

Green line: the fit with one (3770) hypothesis;

Circles with error bars in red are the measured net cross sections after subtracting J/and continuum contribution.

The blue line shows the fits

Solution 2: two amplitudes, complete interference

PRL101 (2008) 102004

Anomalous line-shape

Solution 3: (3770) amplitude + G(3900), interference

Red line: Solution 3Blue line: one (3770) Yellow line: Solution 1Green line: Solution 2The ratio of the

residual between the observed cross section and the fitted value for one (3770) amplitude to the error of the observed cross section

PRL101 (2008) 102004

Anomalous line-shape

2. Significance of the interference between the two amplitudes is 3.6

1. Significance of the two amplitudes is more than 7

3.

4. Solution with two amplitudes +G(3900) gives almost the same results with Solution 2

The hypothesis of (3770) amplitude +G(3900) and interference does not significantly improve the fit from the one (3770) amplitude hypothesis

PRL101 (2008) 102004

Numbers of events and Detection efficiencies

Measurement of D+D-(s)/D0D0(s)PLB668 (2008) 263

DD [n

b]

Measurement of D+D-(s)/D0D0(s)D+

D-(s

)/D0

D0(s

)

PLB668 (2008) 263

Cross section for DD production

Summary

Anomalous lineshape of e+e-hadrons(s) in energy region from 3.65 to 3.87 GeV

Measurement of D+D-(s)/D0D0(s) in energy region from 3.74 to 3.80 GeV

Systematic study about B[(3770)non-DD]

Thank You !