中国高能物理学会第十届全国粒子物理学术会议 , 南京

Observation of X(1835) in J

房双世

“ 晨光杯”论文报告

Outline

Introduction Event Selection Background Study Results Summary and Discussion

A narrow enhancement is observed in . Assuming that the system is in an S-wave resulted in a resonance mass of MeV and a total width of MeV.

ppJ pp

5325101859

m30

M=1859 MeV/c2

< 30 MeV/c2 (90% CL)

+3 +510 25

M(pp)-2mp (GeV)0 0.1 0.2 0.3

Introduction

Introduction

pp J

It can be interpreted as a ppbar bound state. In such a case, it is desirable to observe such a state in other decay modes.

Many possible decay modes suggested in

C. S. Cao and S.L. Zhu Commun. Theory. Phys. 42, 844(2004)

C. J. Ding and M. L. Yan, Phys. Rev. C72(2005)

J One possible decay modes,

never studied before at BES

easy to tag using

Charged tracks

• 4 good charged tracks with |cos|<0.8 in MDC;

• The total charge is required to be 0;

• PID: at least three of them are identified as pions with TOF and dE/Dx ;

Photon selection

• Energy deposited in BSC greater than 60 MeV

• Isolated from charged tracks by more than 5o

• N =3 for

• N =2 for

Event Selection

)( J

)( J

used to improve the mass resolution

Event Selection for )( J

824 C

GeVMM 05.0||

1525 C

M

GeVMM 015.0||

Analysis of )( J

' X(1835)

Event Selection for )( J

224

KKC

824 C

GeVM

GeVmM

GeVM

82.072.0

05.0||

22.0

GeVMM 025.0||

0

Analysis of )( J

' X(1835)

mass-sideband events Main background, 60M decays by LUND model Check efficiency curve phase space

Background Study

' 0J

J

J

Bkg. study for )( J

LUND MC

)(0 J

sidebandsdata

data

Bkg. Study for )( J

Phase space eventsEfficiency curve

MC

Bkg. Study for )( JLUND MC

)(0 J

sidebands

data

data

)( J

Bkg. Study for

Efficiency curve Phase space events

MC

)( J

Observation of X(1835) in

The sum +- mass spectrum for decaying into +- and

J

J

Mass spectrum fitting

2668obsN

MeVm 1.84.1827

MeV5.342.54

410)7.08.1()()( XBXJB

5.1 The +- mass spectrum for

)( J

Mass spectrum fitting

43193obsN

MeVm 9.73.1836

MeV1.233.70

410)5.03.2()()( XBXJB

6.0

The +- mass spectrum for

)( J

Mass spectrum fitting

54264obsN

MeVm 7.21.67.1833

MeV7.73.207.67

410)4.04.02.2()()( XBXJB

7.7The sum +- mass

spectrum for decaying

into +- and

Mass and width from m=1827.48.1MeV/c2 , =54.234.5MeV/c2

Mass and width from m=1836.37.9MeV/c2 , =70.323.1MeV/c2

The sum of mass spectrum for two decay modes

m=1833.76.12.7MeV/c2 , =67.720.37.7MeV/c2

)( J

)( J

The sum of mass spectrum for two decay modes

)( J410)7.08.1()()( XBXJB

)( J

410)4.04.02.2()()( XBXJB

410)5.03.2()()( XBXJB

The mass, width and branching fractions obtained from two different decay modes are consistent with each other.

Results of mass spectrum fitting

Paper published inPhys. Rev. Lett. 95,262001(2005)

(Received 11 August 2005; published 28 December 2005)

SPIRES-HEP search

(2008-04-01) 39 times cited

• 首次在以我国科学家为主进行的北京谱仪实验中发现新粒子。国际权威《粒子数据手册》 PDG2006 首次收录以中国科学家为主发现的新粒子 X(1835) 等。

强烈反响和广泛的认同 (I)

《粒子数据手册》在 2006年版的“非常规介子”综合评述部分，因 BES 实验的新发现而首次加入有关“质子－反质子束缚态”的评述。

强烈反响和广泛的认同 (II)

在国内，“北京电子对撞机上发现 X1835 新粒子”被评为

– “2006 年度中国基础研究十大新闻”第一名

– “2006 年度国内十大科技新闻”第二名。

Summary and Discussion

A new resonance X(1835) observed in

The mass, width and branching fractions obtained from two different decay modes are consistent with each other.

J

X(1835) could be the same structure as ppbar mass threshold enhancement.

It could be a ppbar bound state since it dominantly decays to ppbar when its mass is above ppbar mass threshold.

Its spin-parity should be 0-+: this would be an important test.

PDG2006 takes it as a possible ppbar bound state.

Fit to J/pp including FSI

Include FSI curve from A.Sirbirtsev et al.(hep-ph/ 0411386) in the fit (I=0)

M = 1830.6 6.7 MeV

= 0 93 MeV

ppp mM 2

In good agreement with X(1835)

Summary and Discussion

Other interpretations are not excluded.

Glueball?

N. Kochelev, D. P. Min Phys. Lett. B633:283(2006);

B.A. Li, Phys. Rev. D74:034019(2006);

C. F. Qiao Phys. Lett. B642:53(2006)

radial excitation ?

T. Huang S. L. Zhu Phys. Rev D73:014023(2006)

• Determination of its IGJPC helps us to understand this resonance

• Confirmation of X(1835) in other decay modes needed

• With 100 times high quality data, may BESIII issue a new “birth certificate” for X(1835) soon !

Summary and Discussion

谢 谢

Back up

BCK subtracted PS corrected

BCK subtracted PS corrected

Photon angular distributions in

• For Data – it is not inconsistent with 0-+ -- statistics is too low.

)( J

X(1835) region

X(1835) sideband

Sideband Subtracted &Eff. corrected

)( J